Sunday, December 22, 2024
Saturday, December 21, 2024
Alien Intervention-A Great Science Fiction Film
This week, I have discussed unpleasant subjects like wars, assassinations, etc. I want to end the week with an uplifting subject and a great movie recommendation. "Alien Intervention" from 2023 is already a cult classic in my mind. Here is a link for those curious:
https://www.imdb.com/title/tt15076688/?ref_=nm_flmg_job_1_cdt_t_3
The film tells the story of a young girl who encounters a relatively benign alien. This visitor from another world vanishes. Then he comes back to visit this young girl who is now a woman in her 30s married and living in a very small desert town somewhere in the Southwest.
A most accomplished actress named Carie Kawa plays the woman who encounters the alien again. She is an actress that I had never heard of until I watched this incredible film. You have not heard of her either.
Rest assured that the professors at her acting school hold Carie in the highest regard. Directors who have worked with her on stage plays, television programs, movies, etc. hold her in the highest regard. We would hear them describe her as "an actor's actor." I would describe her as the modern-day Katherine Hepburn.
Carie's character in the movie is Clive. She owns a small and not very successful hotel in a small town. She is married to a man who is an artist. He makes money from time to time selling paintings. The couple are in love.
The alien from her childhood reappears. Clive's whole world is turned upside down. A mysterious government official appears and starts spending a lot of money. Carie's character is very middle class, normal, and easy to like and understand. She is vulnerable, sweet, and feminine. She is also "tough as nails” and brave.
Carie's great acting carries the show. It turns it into an incredibly emotional experience. This is a great film and worth the time to watch.
Friday, December 20, 2024
Thursday, December 19, 2024
Wednesday, December 18, 2024
Tuesday, December 17, 2024
The Future Of Mars Robotic Exploration
Ingenuity
The Ingenuity Mars helicopter after its final landing, which snapped its four rotor blades. (credit: NASA/JPL-Caltech/LANL/CNES/CNRS)
The future of robotic Mars exploration
by Jeff Foust
Monday, December 16, 2024
In January, the Ingenuity Mars helicopter lifted off for the 72nd time, a simple “pop up” flight for the tiny vehicle to get its bearings after making a rough emergency landing on its previous flight. But on the flight, the vehicle’s navigation system, which uses images from a downward-facing camera to lock onto rocks and other surface features to determine where it is and how it is moving, struggled in the featureless sandy terrain in that portion of Jezero Crater.
At a briefing at last week’s annual meeting of the American Geophysical Union (AGU) in Washington, JPL engineers discussed what they believe happened on the final flight of Ingenuity. Immediately after the flight, they thought that the helicopter came in at an angle, with one of its rotor blades hitting the surface and breaking off, based on the images that Ingenuity was able to send back.
“This program is looking at changing the paradigm of how we think about Mars missions,” said Ianson. “Every opportunity there is when a launch window opens up, can we send something up?”
Instead, the force of a hard landing with high lateral velocities broke all four rotors at the same location, about one-third of the way from the tip. “It suggests that they were all subjected to similar loads and they broke at a weak structural point along the blade,” said HÃ¥vard Grip, chief pilot for the first half of Ingenuity’s mission at JPL, at the briefing. That conclusion, he added, was supported by structural analysis of the lightweight blades.
The investigation led to several recommendations, such as improving navigation systems to handle terrain with few features and more robust handling of telemetry in the event on anomalies for any future helicopters. But when might another fly on Mars?
The same day as the JPL team discussed the results of the Ingenuity investigation, NASA outlined its vision of the future of robotic exploration of Mars. The agency released a 154-page report titled “Expanding the Horizons of Mars Science” that describes what future robotic missions on Mars might do, and how.
“This program is looking at changing the paradigm of how we think about Mars missions,” said Eric Ianson, director of NASA’s Mars Exploration Program, during a side meeting at the AGU conference to discuss the report. “Every opportunity there is when a launch window opens up, can we send something up?”
Rather than a few large missions, costing in some cases more than a billion dollars, the plan envisions more, smaller missions focused on specific science questions. Many of those missions will cost between $100 million and $300 million, carrying potentially a single instrument or a small suite of instruments. They would be augmented by a few “medium-class” missions with bigger price tags, potentially over $1 billion, along with missions of opportunity to fly an instrument on another space agency’s mission.
And what would those missions do? The report outlined three “co-equal” science themes. One, called “exploring the potential for Martian life,” would focus on the search for past or present life on Mars. “Did life ever arise on Mars, and if so, does it exist today?” said Becky McCauley Rench, program scientist in NASA’s planetary science division and co-lead of the study, at the meeting. “If life never developed, why not?”
A second, related one, called “revealing Mars as a dynamic planetary system,” would conduct other science about Mars, with a focus on comparative planetology, contrasting Mars with Earth and other worlds in the solar system. “We want to learn as much about Mars as we know about Earth,” she said.
While the strategy is focused on robotic exploration, a third theme seeks to prepare for future human missions by doing preparatory science and filling knowledge gaps. The idea, she said, is to determine what those future crews can best do while on Mars to advance broader science goals. “How can we prepare to maximize that precious human time on the surface and the resources in connection with the export community here on Earth?” she said.
The plan is a not a specific architecture of missions—fly missions A, B, and C in 2026, mission D and E in 2028, etc.—but rather an overall approach. Many of the missions, particularly the smaller ones, will be competed, with teams submitting proposals to fund their mission concepts that address science questions in those three themes. Ianson noted that might result, in some cases, NASA picking a single $300 million mission for a particular launch window or three $100 million missions.
As NASA was working on the plan, the agency was looking at what roles commercial providers could play in robotic Mars missions. In May, the agency awarded 12 small study contracts to nine companies to explore how commercial capabilities could deliver payloads to Mars as well as provide communications and imagery. Those capabilities could refresh aging infrastructure, like the high-resolution camera on the nearly 20-year-old Mars Reconnaissance Orbiter.
At a meeting in November of the Mars Exploration Program Analysis Group (MEPAG), NASA officials provided summaries of the studies. SpaceX, which had a study contract for communications services, proposed, perhaps unsurprisingly, a version of its Starlink constellation dubbed “Marslink.” Blue Origin examined how its Blue Ring transfer vehicle could be used to deliver large payload to Mars and also provide communications services. Albedo, a startup developing high-resolution Earth imaging satellites, explored using that technology at Mars.
Agency officials said at MEPAG that while they were still reviewing the results of the industry studies, they appeared promising, an assessment that Ianson echoed at last week’s meeting. “There really is some merit here and we think there is something that merited further studies and further work,” he said.
He added that the companies that participated in the studies were interested in playing a role in Mars exploration. “The biggest question or the biggest comment that we generally get from the commercial sector is, what’s the business case?” he said.
He indicated that a purely commercial services approach, where the companies develop the capabilities and NASA then buys services from them, “is probably not a totally workable solution,” a finding that aligns with commercial services for crew and cargo transportation to the space station and commercial lunar missions. “There probably needs to be some level of investment through a public-private partnership on the NASA side up front,” he concluded.
MSR update
The Mars plan announced last week does not cover human exploration of Mars, which is the subject of the agency’s separate Moon to Mars strategy, beyond discussion of precursor science to support those later missions. The plan also does not include the ongoing Mars Sample Return program, which has been the subject of ongoing efforts to reduce its cost and shorten its schedule (see “NASA looks for an MSR lifeline”, The Space Review, April 29, 2024).
Those efforts included soliciting a dozen studies from industry and within NASA on ways to alter the entire MSR architecture or key portions of it, like the Mars Ascent Vehicle (MAV) rocket that would launch the samples collected by the Perseverance rover into Martian orbit to be picked up and returned to Earth.
“They’re free to evaluate the benefits represented in the whole span of the studies and put together the architecture they think gives us the best chance of returning samples to Earth before 2040 and/or putting together an architecture that will cost less than $11 billion,” Gramling said of the MSR review team.
Those studies are now complete and in the hands of NASA. The organizations involved have released varying degrees of details. At the ASCEND conference in Las Vegas in late July, for example, Northrop Grumman described its work to make the MAV smaller, which could in turn make the lander that delivers the MAV to the Martian surface smaller and cheaper. Quantum Space explored how its technologies could be used for the “anchor leg” of returning samples form cislunar space to the Earth, simplifying the Earth Return Orbiter spacecraft.
At the MEPAG meeting last month, JPL showed how it could make the Sample Retrieval Lander, which carries the MAV, small enough to use the same “sky crane” technology for landing Perseverance and Curiosity, an approach that could cut the overall cost of MSR in half from earlier estimates of as much as $11 billion and get the samples back in 2035 versus 2040. The Applied Physics Lab and L3Harris discussed at the same meeting separate approaches for making the MAV smaller.
Other companies have been less forthcoming. SpaceX was one of the companies that performed an MSR study but has provided little information about how it would do it other than a proposal abstract that stated it would leverage Starship.
The studies are now in the hands of an independent committee called the MSR Strategy Review Team, or MSR-SR, chaired by MIT planetary scientist Maria Zuber. (When NASA announced the MSR-SR in October, it was originally led by former administrator Jim Bridenstine, but he stepped down shortly after it started work; NASA said he concluded he was “unable to fully dedicate the time necessary to complete this important work for the agency.”) The team will review the studies and make recommendations to NASA on the best way forward.
“That go-forward architecture doesn’t necessarily have to be any of the studies as proposed,” said Jeff Gramling, MSR program director, at the MEPAG meeting. “They’re free to evaluate the benefits represented in the whole span of the studies and put together the architecture they think gives us the best chance of returning samples to Earth before 2040 and/or putting together an architecture that will cost less than $11 billion.”
That recommendation will go to NASA leadership this month, a schedule that agency officials have subsequently said they are maintaining. While NASA may decide on a new architecture for MSR in the final weeks of the current administration, it’s widely expected that the incoming administration will review and possibly reconsider that plan after it takes office in January.
“We’re very happy that we have a range of options that are being looked at,” Gramling said. “We think we’re going to be able to come forward with a plan.”
Mars Chopper
The Mars Chopper helicopter would use the experience from Ingenuity for a larger, more capable vehicle. (credit: NASA/JPL-Caltech)
Next steps
With the broader robotic Mars exploration strategy in place, NASA is thinking about how to implement the plan. That strategy emphasized the need for technology development in several areas, from mobility to entry, descent, and landing. NASA’s 2025 budget request included $40 million to support technology development in those areas.
While that budget request has yet to result in a final appropriations bill, NASA is taking action on that plan. Ianson said the agency has decided to allocate $30 million of that to 25 technology development projects at NASA centers, with the other $10 million being considered for grants to industry and academia for what he called “innovative robotic mobility technologies.”
Mars Chopper “is a concept, intended to put out there a possibility for something that could be—and, obviously, we hope, would be—implementable in the future,” Grip said.
He cautioned at last week’s meeting that the plan, which offered few specifics on funding levels, was unlikely to be adopted fully by NASA. The document itself stated that it depends on other priorities within the agency and its planetary science division. “Realistically, this Plan would not be fully realized until after MSR has returned samples to Earth,” it stated, but added that “the agile nature of the architecture provides the flexibility to implement portions of the Plan significantly sooner if funding were available.”
“Obviously, we would love to do everything in the plan. However, that’s not realistic under challenging budget circumstances and competing priorities,” Ianson said. “I look at this plan less as a roadmap but more as a menu of options to choose from, based on the availability of budget and the most pressing needs to support Mars science.”
Many, though, are prepared to offer missions if and when NASA does proceed with specific portions of the strategy. At the Ingenuity briefing, for example, the JPL team discussed their development of a new helicopter concept called Mars Chopper. The helicopter, with six sets of rotors, would be able to carry up to five kilograms of scientific payload—Ingenuity itself weighed less than two kilograms—and travel three kilometers per Martian day.
“It’s really a gamechanger when it comes to exploration and discovery,” said Teddy Tzanetos, Ingenuity project manager.
They added there were no firm plans to develop or fly Mars Chopper, although a vehicle like it could fit into the new Mars exploration plan. “It is a concept, intended to put out there a possibility for something that could be—and, obviously, we hope, would be—implementable in the future,” Grip said.
“We believe that although Ingenuity was the first aircraft on another planet,” said Travis Brown, chief engineer and team lead for Ingenuity, “it shouldn’t be the last.”
Jeff Foust (jeff@thespacereview.com) is the editor and publisher of The Space Review, and a senior staff writer with SpaceNews. He also operates the Spacetoday.net web site. Views and opinions expressed in this article are those of the author alone.
Countering Threats To U.S. Commercial Space Projects
Starlink Ukraine
The use of Starlink in the Ukraine war shows the growing use of commercial space capabilities in combat and the threats those systems now face. (credit: Ukraine Military Center)
Countering threats to US commercial space systems
by Marc Berkowitz
Monday, December 16, 2024
The reemergence of threats to US national interests in outer space is a byproduct of the renewed geopolitical competition between the United States and other great powers. A new entente of powers led by autocratic regimes with revisionist or irridentist political aspirations seek to alter the international order. To achieve that aim, China and Russia are acting independently as well as collaborating with each other, Iran, and North Korea at the expense of the security of the United States, our allies, and international partners.
The operating environment in outer space reflects the increasingly complex and dangerous international security environment on Earth. Indeed, the ongoing conflict in Ukraine is considered the first commercial space war. Ukraine is leveraging commercial broadband satellite Internet, communications, remote sensing, analytics, and cloud computing services for diplomacy, strategic communications, intelligence support, planning and executing combat operations, and critical infrastructure. Consequently, Russia is targeting and deliberately interfering with US commercial space systems that Ukraine is employing to support its self-defense and asserts they are legitimate military targets.
Russia is targeting and deliberately interfering with US commercial space systems that Ukraine is employing to support its self-defense and asserts they are legitimate military targets.
This article examines how to counter threats to US commercial space systems. It discusses the commercial space marketplace, US policy regarding commercial space activities, the government’s interest in leveraging commercial space capabilities for national security, the threat to commercial space assets and operations, and alternative approaches for their protection and defense. It concludes by recommending how and when to protect and defend commercial space systems and assure they will continue to contribute to America’s economic and national security.
Commercial space marketplace
The commercial space market is robust and vibrant, with a mix of traditional, non-traditional, and new entrants, an expanding number of market segments, and increasing economic value. Indeed, the global space economy is forecast to grow from about $469 billion to more than $1 trillion by 2030. American private enterprises are the primary catalyst for this growth.
The United States is the global leader in space investment, innovation, and invention. American private investment now exceeds that of the public sector in most areas of space research and development. As evidenced by the most recent US government data, the US space economy accounted for $211.6 billion of gross output, $129.9 billion (0.6%) of gross domestic product, $51.1 billion of private industry compensation, and 360,000 private industry jobs in 2021 (Figure 1).[1]
figure
Figure 1: Space Economy Gross Output, 2012–2021
Another indicator of the vibrancy of the commercial space market is the investment startup space ventures were able to attract. Such ventures begin as angel or venture capital-backed new starts. They differ from startup ventures from aerospace and defense contractors and large, publicly traded space companies. According to a study by Bryce Technologies, space startups attracted approximately $8.2 billion in total financing in 2022 despite the global economic downturn which prompted reduced venture funding across all industries.[2] . This involved 154 deals, more than 400 investors, and 123 companies based in more than 20 countries. The average size of the deals was $53 million and seven were more than $100 million. These involved SpaceX and accounted for $2.2 billion out of the $8.2 billion.
The international commercial space marketplace consists of both mature and emerging market segments. The mature segments are launch services, telecommunications, Earth observation, and navigation. Emerging segments include space situational awareness, tourism, in-space servicing and manufacturing, and resource extraction. The commercial or private space sector is one of four sectors in the United States’ space enterprise. The other three are federal government sectors (defense, intelligence, and civil) that interact with and regulate the commercial sector. In fact, the US government is concurrently a regulator, investor, and consumer of the commercial goods and services supplied by the private sector.
US Space Policy
US policy defines “commercial” space as goods, services, or activities provided by private sector enterprises that bear a reasonable portion of investment risk and responsibility, operate in accordance with typical market-based incentives for controlling cost and optimizing return on investment, and have the legal capacity to offer goods or services to existing or potential nongovernmental customers.[3] Presidential guidance directs that the US government shall support and enhance the international competitiveness of America’s space industry, use commercial goods and services to the maximum extent practicable, except for national security, foreign policy, or public safety reasons, and not compete with the commercial space sector.[4]
In addition, the US government has endeavored to streamline regulations on the commercial use of space. Presidential guidance directs the reform of the Executive Branch’s commercial space regulatory framework to ensure America is a leader in space commerce.[5] This includes commercial space transportation regulations, commercial remote sensing regulations, radio frequency spectrum management, and export licensing regulations.
US policy has succeeded in enabling the growth of commercial space activities. In addition to strengthening the US economy with jobs, technology, trade, and revenue, this creates opportunities to leverage the commercial space sector for US national security. Such opportunities include reforming government space acquisition practices and processes; accelerating capability delivery; accessing new sources of innovation and invention; saving or avoiding costs; focusing government investment on unique and/or advanced defense and intelligence capabilities; using competition as a catalyst for improved space capability, affordability, and agility; improving inter-sector relationships regarding resilience, protection, and defense of critical space missions and assets; and enhancing space mission resilience and the deterrence of aggression.[6]
Leveraging commercial space for national security
Commercial space is one of America’s main asymmetric advantages in the ongoing astropolitical competition. Consequently, the US national security space community has embarked on creation of “hybrid” (government and commercial) architectures that leverage space capabilities designed, developed, and produced by both the traditional aerospace and defense industry as well as new commercial enterprises to field systems rapidly, increase opportunities for technology insertion, and enhance the resilience of the national security space force structure and posture. Considering America’s reliance on space for both economic and national security as well as the array of threats posed to space systems, it is prudent to leverage the commercial space sector’s financial resources, technical innovations, and entrepreneurial skill, while managing the potential risks of doing so.
The US government and the private sector must determine how much protection is required, under what circumstances, and for how long. Different degrees of protection may satisfy different mission needs.
Indeed, recognizing that it will be more resilient and capable if it combines organic capabilities with the capabilities from other providers, the US Space Force recently issued a Commercial Space Strategy to “leverage the commercial sector’s innovative capabilities, scalable production, and rapid technology refresh rates to enhance the resilience of national security space architectures, strengthen deterrence, and support Combatant Commander objectives in times of peace, competition, crisis, conflict, and post-conflict.”[7] Consistent with this strategy, the Space Force will consider commercial support for space domain awareness; satellite communications; space access, mobility and logistics; tactical surveillance, reconnaissance, and tracking; environmental monitoring; cyberspace operations; command and control; and positioning, navigation, and timing.[8] It will not seek commercial support for missile warning, combat power projection, electromagnetic warfare, and nuclear detonation detection.[9]
Similarly, the National Reconnaissance Office (NRO) is pursuing a hybrid approach to its future intelligence space architecture.[10] As Dr. Troy Meink, the NRO’s principal deputy director, stated that the NRO sees value in leveraging new commercial capabilities for certain missions where small satellites can meet requirements at lower cost. The NRO has issued contracts for electro-optical, radar, radio frequency, and hyperspectral imaging contracts for the acquisition of commercial data.[11] 11
The Department of Defense (DoD) defines “protection” as “preservation of effectiveness and survivability of mission-related personnel, equipment, facilities, information, and infrastructure deployed or located within or outside the boundaries of a given operational area.”[12] Defense, security, survivability, assurance, operational continuity, and resilience, however, have all been used by US government officials as synonyms for protection. There are, of course, different degrees of protection that can be provided to commercial space systems. Not all forms of protection are equivalent. The US government and the private sector must determine how much protection is required, under what circumstances, and for how long. Different degrees of protection may satisfy different mission needs. Required levels of protection should be driven by mission, threat, vulnerability, and available alternatives.
The US government has long declared that unimpeded access to and use of space is a vital national interest because of its overriding importance to America’s safety, integrity, and survival.[13] US space policy states that space systems are sovereign property with the right of passage through and operations in space without interference.[14] “Purposeful interference,” with space systems, including supporting infrastructure, is an infringement on US sovereign rights.[15] The United States may respond to such interference at a time, place, and manner of its choosing, including with the use of force, consistent with its inherent right of self-defense.[16]
Despite this declaratory policy, the US government either has not responded or only issued diplomatic demarches in response to the increase in such purposeful interference incidents. The DoD only amended its space policy to state that it would protect and defend such assets if directed by the Secretary of Defense or other appropriate authority.[17] DoD’s Commercial Space Integration Strategy states that “in general, the Department will promote the security of commercial solutions through three lines of effort: norms and standards, threat information sharing, and financial protection mechanisms.”[18] In this regard, US Space Command, National Geospatial-Intelligence Agency, and NRO established a “Commercial Space Protection Tri-Seal Strategic Framework” to jointly share threat information to avoid or reduce harm to commercial satellites from potential threats.[19]
Threat to commercial space assets and operations
The geopolitical competition has extended to near Earth space and may expand to cislunar space, the region beyond geosynchronous Earth orbit and the Moon’s surface. The astropolitical dimension of the conflict has prompted the current and growing threat to US national interests in space. Adversaries have developed, tested, fielded, and operate anti-satellite (ASAT) or other offensive space control weapons systems to contest freedom of passage through and operations in space. Whether they are owned and operated by governments, international consortia, or commercial enterprises, spacecraft are being held at risk. As then-Vice Chief of Space Operations General David Thompson stated, “both China and Russia are regularly attacking U.S. satellites with non-kinetic means, including lasers, radio frequency jammers, and cyber-attacks.”[20]
Russia and China see space as a domain where the United States can be coerced given its dependence upon vulnerable space systems. They are pursuing an array of cyber, electronic warfare, kinetic energy, directed energy, nuclear, and orbital counterspace weapons.[21] Indeed, the White House recently confirmed media reports that Russia has developed and is preparing to deploy a nuclear-armed ASAT weapon on-orbit.[22] Similarly, Iran and North Korea have cyber, electronic warfare, and missile capabilities which can interfere with space assets and operations.[23]
The value of space systems for prestige, influence, knowledge, wealth, and power is what makes them lucrative targets. Political, symbolic, and economic as well as dedicated defense and intelligence space assets thus may be attacked. Conflict may begin in or extend to space to undermine US military combat effectiveness, intelligence collection, economic prosperity, societal cohesion and morale, and political resolve.
The Russia-Ukraine conflict highlights the increasing value and utility of commercial space operations for US and international security.[24] It also underscores the associated risk of being considered military targets by adversaries. Months prior to the invasion, Russia conducted a destructive test of a direct-ascent kinetic-energy ASAT. The test generated thousands of pieces of orbital debris that endangered both American astronauts and Russian cosmonauts on the International Space Station as well as harmed space environmental sustainability (Figure 2).[25]
figure
Figure 2: Orbital Debris Track From Russian Kinetic Energy ASAT Test[26]
While it prompted international opprobrium, the ASAT test served as a clear warning of Russia’s ability to hold key satellites at prompt risk of destruction.
Moreover, Russia engaged commercial and civil space systems as a precursor to their large-scale invasion and during subsequent kinetic combat operations. An hour before the invasion, Russia launched a targeted denial of service cyberattack against Viasat’s KA-SAT ground network (Figure 3).[27]
figure
Figure 3: Viasat’s KA-SAT Cyber-attack Summary[28]
It has also repeatedly attempted to interfere with SpaceX’s Starlink satellite internet services.[29] In addition to commercial satellite Internet and telecommunications services, Russia jammed civil satellite positioning, timing, and navigation services with electronic warfare systems (Figure 4).[30]
figure
Figure 4: Russian Zhitel and Tirada-2 Electronic Warfare Systems[31]
In an ex post facto justification, a senior Russian Foreign Ministry official asserted that commercial assets are legitimate military targets. Konstantin Voronstov, deputy director of the Department for Non-Proliferation and Arms Control, said at the United Nations that:
I would like to draw special attention to the extremely dangerous tendency, which has surfaced in the course of the developments in Ukraine. I mean the use of outer space civil infrastructure facilities, including commercial ones, in armed conflicts by the United States and its allies…Quasi-civil infrastructure may be a legitimate target for a retaliation strike. [32]
Similarly, Russian Foreign Ministry spokesperson Maria Zakharova said, “We are aware of Washington’s efforts to attract the private sector to serve its military space ambitions … [such systems] become a legitimate target for retaliatory measures, including military ones.”[33]
The US government’s renewed interest in leveraging commercial space capabilities for national security will heighten the risk that commercial space assets operations will become military targets.
As evidenced by Russian words and deeds, they are not inhibited in targeting commercial systems that are US sovereign property and being employed by numerous countries besides Ukraine. Russia clearly recognizes that third-party space systems not owned or operated by their adversary can impact the course and outcome of the conflict. Consequently, they are conducting sustained non-kinetic offensive space control operations for area denial and force protection.
The US government’s renewed interest in leveraging commercial space capabilities for national security, especially integrating commercial goods and services into hybrid architectures with both government and private sector capabilities, will heighten the risk that commercial space assets operations will become military targets. Consequently, all approaches for how to protect commercial space systems must be considered.
Protection and defense alternatives
There are numerous options for protecting and defending commercial space systems. As shown in Figure 5, these range from avoidance to active defense. Options vary, among other things, in terms of practicability, cost, and likelihood of success. None are mutually exclusive. While they could be implemented independently, a course of action with a combination of options is more likely to create synergistic benefits and be effective.
figure
Figure 5: Options for Protecting and Defending Commercial Space Systems
Avoidance, self-restraint, or strategic evasion would entail the US government greatly reducing or eliminating its use of, and reliance upon, commercial space goods and services for defense or intelligence purposes. The benefit of avoidance is that it could undercut an adversary’s motive for holding at risk and attacking commercial space systems. Its disadvantages are its impracticability as well as that an adversary may not believe America will not rely upon commercial space capabilities that have dual (civil and national security) uses and might target commercial assets anyway because of the impact of disrupting or eliminating their services.
Diplomacy involves negotiating with foreign nations or non-nation-state actors on tacit or formal agreements to protect commercial space systems. It can also involve bringing pressure, for example, through political or economic sanctions, to persuade a belligerent to adopt a policy of not interfering with commercial space systems providing services to non-combatants prior to hostilities or stop doing so if already engaged in hostilities. The advantages of diplomacy are that is it the lowest-cost option and may help to legitimize or provide political top cover for other approaches. Its disadvantages are an unfavorable track record and opportunity costs. Diplomatic initiatives may be unpersuasive, and sanctions may be ineffective as well as impose financial burdens on the US, its allies, and friends.
Arms control involves negotiating measures to prohibit or constrain the development, testing, or use of ASATs and counterspace weapons to minimize the costs and risks of a space arms competition or conflict involving space, as well as limit the scope and intensity of violence in the event of war. The advantages of space arms control are that it could inhibit or reduce the threat as well as the cost of defensive preparations. Its disadvantages include creating opportunities for adversaries to conduct political and legal warfare (lawfare), the problem of defining what constitutes a weapon, the variety of threats against space systems, dual-use technology, verifying compliance, and enforcement.
Deterrence by cost imposition, punishment, or retaliation entails confronting an adversary with prospective costs greater than expected gains.[34] Punitive threats could involve military action, economic sanctions, diplomatic penalties, or other measures that will punish or thwart the adversary if it does not comply. The advantage of deterrence by cost imposition is that it may restrain an adversary from threating or using force against commercial space assets. Its disadvantage is that it may fail. The opponent may not perceive the threat is credible, it may not be sufficient to produce restraint, the adversary also may be able to absorb the punishment, be willing to risk escalation, or, if the decision-maker is insane, a religious zealot, or terrorist, literally may be “beyond deterrence.”
The US government should implement a comprehensive approach that integrates diplomacy, threat awareness, deterrence (by denial and cost imposition), as well as passive and active defenses to protect commercial space systems.
Deterrence by denial involves acquiring and fielding capabilities and preparing potential counteractions that would make the benefits of attacking commercial space assets and operations appear too difficult or expensive to achieve.[35] Denial of benefits can be accomplished with defensive measures. The advantages of deterrence by denial are that it not only may inhibit or reduce the threat, but it also provides a hedge against deterrence failure. Its disadvantages are that it may not be effective if the threat is perceived as incredible, the adversary is willing to risk escalation, or is beyond deterrence.
Passive defenses involve measures to evade, withstand, operate thru, or degrade gracefully against ASAT or counterspace weapons effects. Such countermeasures include, for example, physical security, infrastructure protection, backups, autonomy, encryption, hardening, and proliferation.[36] The advantages of passive defenses are that they can counter specific types of weapons systems and effects, enable deterrence by denial, and hedge against deterrence failure. Its disadvantages are penalties of increased size, weight, or cost of acquiring and operating the satellite system.
Active defenses involve fielding military capabilities to suppress and destroy threats to space assets. The authority to “shoot back” at threats to commercial assets either could be retained by uniformed military personnel or the government could issue “letters of marque and reprisal” to allow private persons to conduct active defense or launch counterattacks against the space weapons of a foreign nation.[37] The advantages of active defenses are that they enable deterrence by denial, inhibit or reduce the threat, and hedge against deterrence failure, and limit damage. Its disadvantages are cost and concerns about “weaponizing” space.
Recommendations
Outer space is an increasingly complex and dangerous operating environment for government and commercial space systems. In order to determine the best mix of non-materiel and materiel solutions to address the threat to US vital national interests in space, the DoD should conduct rigorous, objective, data-driven analytic decision support to inform force design and acquisition decisions, including where commercial goods and services fit in national security space force structure and posture. Decisions regarding the employment of commercial capabilities for national security purposes should be based on multidisciplinary system engineering, architecture, economic, and operational analyses.
Such analyses should be used to determine mission utility, mission-critical dependencies, operational risks, vulnerabilities, costs, and policy implications that reliance or dependence upon commercial space systems would entail so the government can “use the right tool for the job.” In addition, the President, Secretary of Defense, and Director of National Intelligence should provide direction regarding the acceptable extent of reliance or dependence on commercial space capabilities for defense and intelligence space missions. This could range from deconfliction and coordination, to augmentation and integration, all the way to federation or interdependence.
Based on the aforementioned decision support and direction, the US government should implement a comprehensive approach that integrates diplomacy, threat awareness, deterrence (by denial and cost imposition), as well as passive and active defenses to protect commercial space systems. This includes fielding a dynamic, layered, defense in-depth with a mix of passive and active defenses to evade, withstand, operate through, degrade gracefully, suppress, and destroy threats to space systems. Such a defense in-depth will help to thwart an attack with successive layers and multiple countermeasures at each layer to defeat threat kill chains, rather than relying on a single line of defense.
The federal government should incorporate this comprehensive approach into declaratory policy statements and diplomatic engagements to convey US national interests and the stakes that would be involved in a conflict in the space domain to deter adversaries as well as reassure allies and partners. In addition, the President should provide guidance to the Director of National Intelligence to assess foreign capabilities and intentions regarding threats to commercial space assets and operations. The President should also provide guidance to the Secretary of Defense to prepare operations and contingency plans as well as rules of engagement, thresholds, and triggers for protection and defense of US citizens, property, and commercial assets as well as non-US forces, and foreign nationals or property in space.
The Secretary of Defense should then direct the combatant commanders to incorporate such protection and defense in their development of critical asset lists and defended asset lists. Policy reviews of war plans as well as war games and exercises should be conducted to evaluate such rules of engagement, thresholds, triggers., and defensive priorities. This will require the US government to determine what constitutes hostile actions and declarations of hostile intentions involving space systems. In comparison to a nuclear detonation or a kinetic strike in space, non-kinetic acts may not necessarily constitute an armed attack under international law. At what point (in scale, duration, or effect), for example, should electronic warfare jamming or spoofing be considered a hostile act?
Additionally, it will be up to the President and Congress to decide, given the circumstances, interests, stakes, and risks, whether deliberate interference with a dual-use commercial system is considered a casus belli or act or war, like the sinking of the Lusitania that killed 1,195 people, including 123 Americans, in 1915, or whether it does not, as is the case thus far during the Ukraine conflict. DoD can communicate America’s resolve to protect and defend commercial space assets via diplomatic exchanges, experiments, tests, demonstrations, exercises, deployments, and operations.
Moreover, the US government should exercise its influence on the commercial space sector as the monopsonist in the federal space marketplace. In this regard, federal departments and agencies must leverage and align the government’s roles vis-Ã -vis the commercial space sector as a regulator, consumer, and investor. They should engage the commercial space sector with a mix of incentives, inducements, and requirements to increase the protection of their goods and services. This should include financial investments in innovative capabilities, increased procurements of commercial space goods and services, classified information sharing, contractual mandates for traditional commercial insurance, commercial war risk insurance, or government provided insurance or indemnification, and requirements for selected threat countermeasures.
Federal agencies should engage the commercial space sector with a mix of incentives, inducements, and requirements to increase the protection of their goods and services.
The US government can educate the private space sector and foster its enlightened self-interest, among other things, by increasing the sector’s threat awareness via routine information sharing and space domain awareness support of commercial operations. It can also increase its collaboration with the private sector to contract for and utilize commercial systems, information, and analytic capabilities for such support. This can be accomplished, among other things, through the USSF’s Joint Commercial Operations cell, Commercial Space Office, and Commercial Augmentation Space Reserve, as well as the NRO’s Commercial Systems Program Office.
Furthermore, the DoD and intelligence community should engage US space system manufacturers, owners, and operators to influence the design, development, and operations of commercial space systems. They should also incorporate and specify protection requirements in competitions for procurements of commercial goods and services. Additionally, federal authorities (resident in the Departments of Commerce, Transportation, State, Homeland Security, and Justice as well as the Federal Communications Commission) and relationships with the private sector should be utilized to establish a consistent regulatory approach to mandate and enforce minimum levels of protection for commercial space systems to help safeguard US national and economic security.
Where the DoD or intelligence community determines it is prudent to employ commercial capabilities for national security space missions, they should selectively supply government furnished equipment for threat awareness, protection, or defense to the commercial vendors. Similarly, they should selectively fund commercial space enterprises to modify their systems for enhanced threat awareness, protection, or defense.
Finally, the federal government should assess the utility and feasibility of enabling legislation for indemnification, anchor tenancy, and advanced funding in exchange for the ability to leverage commercial space capabilities for national security. The precedent of legislation for indemnification of commercial asserts for such purposes was established in the cases of both the merchant marine and civil reserve aircraft fleets.[38]
References
Department of Commerce, “U.S. Space Economy Statistics 2012-2021”.
Bryce Technologies, Start-Up Space: Update on Investment in Commercial Space Ventures 2023./li>
“National Space Policy of the United States of America,” The White House, December 9, 2020.
Ibid.
Space Policy Directive 2, Streamlining Regulations on Commercial Use of Space, May 24, 2018.
See, for example, Marc J. Berkowitz, “Leveraging Commercial Space Capabilities for U.S. National Security,” National Security Space Association, February 22, 2022.
U.S. Space Force Commercial Space Strategy (Washington, D.C.: Headquarters U.S. Space Force, April 8, 2024).
Ibid.
Ibid.
Dr. Troy Meink, NRO Principal Deputy Director, “Space Symposium Remarks,” April 9, 2024, 3d; and Dr. Christopher J. Scolese, Director, National Reconnaissance Office, “Testimony to House Armed Services Committee, Subcommittee on Strategic Forces, Hearing on Fiscal Year 2024 National Security Space Programs,” April 26, 2023.
Sandra Erwin, “National Reconnaissance Office embracing mix of big and small satellites”, SpaceNews, March 18, 2024.
Joint Publication 1-02, Department of Defense Dictionary of Military and Associated Terms (Washington, D.C.: The Joint Staff, April 2001 as amended through 2010), p. 375.
See for example, William J. Clinton, A National Security Strategy for a New Century (Washington, D.C.: The White House, December 1999), p.12; and United States Space Priorities Framework (Washington, D.C.: The White House, December 2021), p.1.
“National Space Policy of the United States of America.”
Ibid.
Ibid.
Department of Defense Directive 3100.10, “Space Policy,” August 30, 2022.
Commercial Space Integration Strategy, (Washington, D.C.: Department of Defense, 2024).
“Tri-Seal Commercial Space Protection Framework,” National Reconnaissance Office, August 31, 2023.
Josh Rogin, “A Shadow War in Space is Heating Up Fast,” The Washington Post, November 30, 2021.
Defense Intelligence Agency, Challenges to Security in Space (Washington, D.C.: Department of Defense, 2022), pp. 17-18, 27-29.
“Press Briefing by Press Secretary Karine Jean-Pierre and White House National Security Communications Advisor John Kirby,” The White House, February 15, 2024.
Challenges to Security in Space, (Washington, D.C.: Department of Defense, 2022), pp. 30-32.
See, for example, Marc J. Berkowitz, “Strategic Lessons for the Russia-Ukraine Conflict,” in David J. Trachtenberg, ed., Lessons Learned from Russia’s Full-Scale Invasion of Ukraine National Institute for Public Policy Occasional Paper, (Vol. 3, No. 10 (October 2023), pp. 11-20.
“Russian Direct-Ascent Anti-Satellite Missile Test Creates Significant, Long-Lasting Space Debris,” U.S. Space Command Office of Public Affairs, November 15, 2021.
“Russian ASAT Test Debris Visualization,” UK Space Agency, November 11, 2021.
United Kingdom National Cyber Security Centre, “Russia Behind Cyber Attack with Europe-Wide Impact an Hour Before Ukraine Invasion”, May 10, 2022.
“KA-SAT Network Cyber Attack Overview,” Viasat Corporate News, March 30, 2022.
Alex Horton, “Russia Tests Secret Weapon to Target SpaceX’s Starlink in Ukraine,” The Washington Post, April 18, 2023.
Juliana Suess, “Jamming and Cyber Attacks: How Space is Being Targeted in Ukraine,” Royal United Services Institute, April 5, 2022; and Georgi A. Angelov, “Suspected Russian GPS Jamming Risks Fresh Dangers in Black Sea Region”, Radio Free Europe, Radio Liberty, October 26, 2023.
“OSCE Spots Russia's Brand New Military Equipment in Occupied Donbas,” UNIAN, April 3, 2019.
Konstantin Voronstov, “Statement at the Thematic Discussion on Outer Space (Disarmament Aspects) in the First Committee of the 77th Session of the UN General Assembly,” October 26, 2022.
Guy Faulconbridge and Dmitry Antonov, “Russia responds icily to U.S. hint on arms control talks with Moscow and Beijing”, Reuters, March 30, 2024.
See, for example, Marc J. Berkowitz, “Dominance or Deterrence: The Role of Military Power in Addressing Challenges to U.S. National Security,” Comparative Strategy, (October 17, 2022)
Ibid.
See, for example, U.S. Congress Office of Technology Assessment, Anti-Satellite Weapons, Countermeasures, and Arms Control (Washington, D.C.: U.S. Government Printing Office, 1985).
See, for example, James D. Rendelman and Robert E. Ryals, “Private Defense of Space Systems and Letters of Marque and Reprisal,” AIAA Space 2015, August 28, 2015/
46 U.S. Code, Merchant Marine Act, 1920; and 10 U.S. Code, Civil Reserve Air Fleet
Marc Berkowitz is an internationally recognized, well-published expert on national security space matters who served five Secretaries of Defense; was responsible for development, coordination, and oversight of US and Defense Department policy and guidance for space activities; and retired after nearly 20 years as a vice president at a leading aerospace and defense prime contractor. He continues to advise the Defense Department and Intelligence Community as well as private sector clients on defense, intelligence, and space matters.
Canada Now Has A Moon Rover
Canadian lunar rover
A description of the lunar rover being developed by Canada and whose name is the topic of an ongoing contest. (credit: CSA)
Canada’s first moon rover will soon have a name as it prepares to explore a hostile lunar region
by Gordon Osinski
Monday, December 16, 2024
The Conversation
The Canadian Space Agency announced a competition last month to name Canada’s first-ever rover mission to the Moon. This robotic mission will explore the south polar region of the Moon to search for water ice and explore its unique geology.
I am a professor and planetary geologist. I am also the principal investigator for Canada’s first rover mission to the Moon and a member of the science team for the upcoming Artemis 3 mission, the first human landing on the Moon since 1972.
A Canadian first
It was two years ago that Canadensys Aerospace Corporation and its team was selected to build the Canadian lunar rover.
It’s a testament to the caliber of Canada’s space community that, for the first time in history, we are in the driver’s seat.
This mission is hugely significant because it’s not only the first rover that Canada will send to the Moon, but it will be the first-ever Canadian-led mission to another planetary body. While Canadian technology has made it to the surface of the Moon and Mars before, it’s always been on missions led by other nations.
Not that this is a bad thing: science is only possible through collaboration. But it’s a testament to the caliber of Canada’s space community that, for the first time in history, we are in the driver’s seat.
Canada’s first rover mission is truly a team effort. Supporting Canadensys are seven Canadian companies that will build various parts of the rover and its science instruments.
I am proud to lead the science team, which includes faculty and students from six Canadian universities in Québec, Ontario, Manitoba, Alberta, and British Columbia. In keeping with the spirit of collaboration in space, we also have several scientists from the United States and the United Kingdom on our team.
One of the science instruments is also being provided by the Johns Hopkins University Applied Physics Laboratory, supported by NASA. In return, Canada gets a launch from NASA.
What’s in a name?
Every mission needs a name, but not everything is equal when it comes to naming spacecraft. Satellites, for example, are often named in a very functional way, like Radarsat, Canada’s flagship satellite program.
When it comes to rover missions, however, NASA has been choosing inspirational names since the early 1990s with its first Mars rover, Sojourner. Then came along Spirit and Opportunity in 2004 followed by Curiosity eight years later.
The most recent arrival on Mars was Perseverance in 2021, which is currently emerging from a deep meteorite impact crater called Jezero.
NASA’s goal in naming its rovers is to inspire interest in science, technology, engineering and mathematics (STEM); this has undoubtedly been a huge success.
The connection to rovers has also become deeply personal, evident in the outpouring of grief when Oppy, the nickname given to NASA’s Opportunity rover, was declared “dead” in 2019.
The European Space Agency followed suit with its hugely popular animated stories for the Rosetta mission, the first mission designed to orbit and land on a comet, that depicted its Philae lander with a backpack and yellow helmet.
Four potential names
The names of NASA’s series of Mars rovers are inspirational and capture the quest of exploration. In contrast, the Apollo and Artemis programs and many other space missions were named after figures in Greek mythology. Other mission names have historical connotations; some also allude to the culture and values of the country leading the mission.
For Canada’s first moon rover, the Canadian Space Agency has come up with a shortlist of four potential names that conjure up various characteristics of Canada as well as capturing the spirit and goals of the mission:
Athabasca — A famous river that flows from the Rockies through Alberta to Lake Athabasca. Canada’s rivers have been used for millennia and continue to be pathways of discovery, transport and exchange.
Courage — A name that would be representative of the work that has led to the Canadian lunar rover mission.
Glacier — Not only are glaciers associated with the polar regions of Canada, but one of the goals of the rover mission is to find water ice on the Moon.
Pol-R — A word play on polar. Canada is a polar country and the rover mission will be landing in the south polar region of the Moon.
The online voting form to name Canada’s first rover mission to the moon is open until December 20.
The work continues
As our team waits for Canadians to choose the name of our mission, we are hard at work on all aspects of its design and implementation.
In June, we got the green light for our preliminary design review aimed at assessing whether the original design met all the requirements set forth by the government of Canada, and that the risks, cost, and schedule, were all acceptable.
Canada aims to build a lunar utility vehicle that will help to transport cargo, perform science investigations, and support astronauts on the Moon.
We haven’t chosen an easy mission for Canada’s first trip to the Moon. We are going to one of the most hostile regions of the lunar surface: the South Pole. Because of this, our rover must survive very long and cold lunar nights, where the temperature can drop below –200 degrees Celsius for up to 14 Earth days.
We also have to pack all the hardware, plus our six science instruments, into the rover, which is the size of a small coffee table and weighs only 35 kilograms.
I recently provided an update on the science of our soon-to-be-named mission at the International Astronautical Congress in Milan, Italy. In addition to talking about our science instruments, I also delved into the three main objectives of the mission:
To investigate the geology of this unique region of the Moon where, so far, no human or robot has ever been.
To search for water ice, a major discovery in the decades since the Apollo missions. The Moon was thought to be devoid of water, but satellite observations suggest deposits of water ice may be present in this polar region. But we need boots on the ground—or wheels, in our case—to confirm these satellite observations.
To study the radiation environment of this region in preparation for the return of humans to the Moon.
Canadian rovers
The Canadian Space Agency’s fleet of prototype rovers. (credit: CSA)
Canada’s long involvement in space rovers
Over the past two decades, the Canadian Space Agency has funded the construction of a series of prototype planetary rovers ranging from small so-called “nano-rovers” to massive machines capable of carrying two astronauts. Our new lunar rover has a lot of heritage behind it.
If not for the delay to the launch of the European Space Agency’s ExoMars rover mission, originally scheduled for 2022, Canada would have already had wheels on Mars. The wheels, chassis, and drive train for the Rosalind Franklin ExoMars rover was built by Canada’s MDA Space. Launch is now set for 2028.
Canada has also set its sights on a much bigger moon rover. Announced in the 2023 federal budget, Canada aims to build a lunar utility vehicle that will help to transport cargo, perform science investigations, and support astronauts on the Moon.
This rover will be a major contribution to the NASA-led Artemis program. Following the flight of Canadian astronaut Jeremy Hansen on the upcoming Artemis 2 lunar flyby mission, the Lunar Utility Vehicle, Canadarm3, and other Canadian contributions to the Artemis program will ensure a Canadian will one day walk on the Moon.
This article is republished from The Conversation under a Creative Commons license. Read the original article.
Dr. Gordon “Oz” Osinski is a Professor in the Department of Earth Sciences at the University of Western Ontario (Western), Canada. He is the Director of the Canadian Lunar Research Network and the founder and Chair of the Planetary Sciences Division of the Geological Association of Canada. He also served as Associate Director and then Director of the Centre for Planetary Science and Exploration from 2008 to 2019 and was the Founding Director of its successor, the Institute for Earth and Space Exploration (2019–2021).
Book Review: Alcohol In Space
film poster
Review: Alcohol in Space - The Movie
by Jeff Foust
Monday, December 16, 2024
Alcohol in Space - The Movie
Directed by Sam Burbank
2024, 50 mins.
Available to rent and own on Amazon Prime Video
Alcoholic beverages, in their various forms, are key parts of society, and as that society expands into space, it’s natural that alcohol will come along in some way. That has traditionally been limited in government space programs, which often become skittish to even consider the possibility that people might want to have a drink while in space.
“People get a little bit nervous about the topic,” says Chris Carberry, the author of the 2019 book Alcohol in Space that looked at the history and prospects of drinking or making booze in space (see “Review: Alcohol in Space”, The Space Review, December 2, 2019). He is speaking in the opening of a new documentary, also called Alcohol in Space, that is based on the book, looking at the interest people have in drinking in space or using it to make alcoholic beverages.
The film is best seen as showing the enthusiasm and creativity people show when considering the possibilities of alcohol and spaceflight rather than significant progress towards space spirits.
The brief documentary looks at three efforts involving alcohol and spaceflight. One is an effort involving French designers, working with champagne company Maison Mumm, to develop a champagne bottle and glass that can work in microgravity. A second involves Ninkasi Brewing, an Oregon microbrewery that flew yeast on sounding rockets for use to brew beer. The third features a partnership between Nanoracks and Ardbeg to fly terpenes, key compounds in scotch, on the International Space Station.
The film documents those efforts and the ups and downs (figurative and literal) each faced. The design of the champagne bottle required several versions that were tested on aircraft flying parabolic arcs to provide moments of zero-g. Ninkasi’s first attempt to fly yeast failed when they were not able to recover the amateur rocket in time. Ardbeg had to be convinced that Nanoracks was serious when that company offered last-minute accommodations on an ISS payload rack.
The film is best seen as showing the enthusiasm and creativity people show when considering the possibilities of alcohol and spaceflight rather than significant progress towards space spirits. Ninkasi was primarily motivated by the novelty of seeing of yeast that had flown, ever so briefly, in space, could be used to brew beer; as one brewer put it, they didn’t want something too different from what they normally brewed. (The space-flown yeast was used for “Ground Control” beer sold for a time by the brewery.) The terpenes flown in space were not significantly different from those on the ground, and one Ardbeg official noted that, if anything, the ones on the ground tested better. Had the space-flown version been significantly better, it might have posed other challenges, the company noted: regulations require scotch whisky to be aged for at least three years in Scotland, not space.
In 2022, Maison Mumm announced a partnership with Axiom Space to fly its champagne, in that specially designed bottle, on future Axiom flights (see “Commercial space stations: labs or hotels?”, The Space Review, October 10, 2022). The companies, though, have been, well, mum, about that effort since then.
Nonetheless, Alcohol in Space does show the interest in this topic. Perhaps, in the near future, visitors to commercial space stations will be able to sip some Maison Mumm while floating next to a window to see the Earth below, or astronauts on the Moon will drink a beer after a long EVA on the lunar surface. If they do, they can thank, and raise a glass to, some of the people profiled in the film.
Jeff Foust (jeff@thespacereview.com) is the editor and publisher of The Space Review, and a senior staff writer with SpaceNews. He also operates the Spacetoday.net web site. Views and opinions expressed in this article are those of the author alone.
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Artemis Reentry
heat shield
The Orion heat shield from the Artemis 1 mission, whose erosion led to a lengthy investigation that has significantly delayed Artemis 2. (credit: NASA)
Artemis reentry
by Jeff Foust
Monday, December 9, 2024
In January, NASA announced delays in the next Artemis missions to the Moon. Artemis 2, which had been scheduled to launch by the end of the year, was pushed back to September 2025, which resulted in a similar slip in Artemis 3 to September 2026. NASA blamed the delay on several technical issues with the Orion spacecraft, including unexpected erosion of the heat shield seen on the Artemis 1 mission in late 2021 (see “Twenty years of chasing the Moon”, The Space Review, January 15, 2024.)
“There was a lot of little links in the error chain,” Kshatriya said, “that accumulated over time that led to our inability to predict this in ground tests.”
NASA provided few significant updates in the months that followed, sticking to the September 2025 launch date for Artemis 2 even as the slow pace of launch preparations suggested a delay. In late October, NASA officials said that the agency had determined the root cause of the heat shield erosion, but declined to provide details, saying they would wait until after determining how to address the problem for Artemis 2 before disclosing more details. (NASA even avoided releasing images of the heat shield; the only photographic evidence of the erosion came in a report by the agency’s inspector general.)
What corrective action NASA decided to pursue would determine when Artemis 2 could fly. If NASA decided it could just change the reentry profile of Orion, the spacecraft could fly as-is with a modest delay. However, if the heat shield needed to be replaced, a much longer delay—perhaps a year or more—might be in store.
On Thursday—ten years to the day after Orion first flew on the short EFT-1 mission, launched on a Delta IV Heavy—NASA finally announced the outcome of the heat shield investigation and its implications for Artemis 2. During a briefing at NASA headquarters announced on less than 24 hours’ notice, agency leaders said Artemis 2 would be delayed again, now to April 2026, even while avoiding the worst-case scenarios.
“We were able to recreate the problem here on Earth, and now we know the root cause,” NASA administrator Bill Nelson said. “This has allowed us to devise a path forward.”
That root cause was linked to the “skip entry” used by Orion when it reenters, dipping in and out of the atmosphere to bleed off energy. “We have since determined that while the capsule was dipping in and out of the atmosphere as part of that planned skip entry, heat accumulated inside the heat shield’s outer layer,” said deputy administrator Pam Melroy. The created gases inside the heat shield that could not escape, “and led to cracking and uneven shedding of that outer layer.”
The issue, said Amit Kshatriya, deputy associate administrator of NASA’s Moon to Mars Program Office, was linked to the permeability of the heat shield material, called Avcoat. “The permeability of the Avcoat material is essential,” he said, something that only became clear when looking at portions of the heat shield that did not suffer the cracking and loss of char material.
“The acreage of the heat shield was not uniform in terms of its permeability,” he said. “There were places where it was actually more permeable than the rest, a small percentage. In those places, we did not witness in-flight cracking. That was the key clue for us.”
He blamed several factors, including changes in the formulation of Avcoat and “dissolution of the understanding” of how to make it over the decades since its use on Apollo. There was also a change in the geometry of the blocks of Avcoat material as applied to the heat shield. “There was a lot of little links in the error chain,” he said, “that accumulated over time that led to our inability to predict this in ground tests.”
“We can either change the material to mitigate the issue or we can change the environment,” he said. For later Artemis missions NASA will take the former approach, with efforts underway to produce Avcoat with the desired permeability.
For Artemis 2, though, “we can safely and with high degrees of success control that entry environment” with the same heat shield. That revised trajectory will limit the “skip” part of the reentry, where the reduced heating causes gas to build up without the charring that allows the gas to be safely released.
“We need our commercial and international partners to double down to meet and improve this schedule,” Nelson said.
“We want to constrain the downtrack, the period from which the vehicle hits the entry interface down to where aerothermal loading stops,” Kshatriya said. That will be reduced to 1,775 nautical miles (3,287 kilometers). “I wanted 1,776 nautical miles because, if we’re going to fly in the first part of 2026, we could have celebrated the 250th anniversary at the same time. That would have been elegant, but engineering said I couldn’t do that.”
heat shield
A closeup of a portion of the heat shield shows cracking and erosion. (credit: NASA)
That has implications for landing trajectories to ensure the capsule comes down in the preferred location off the coast from San Diego. That also affects launch availability. “In order to constrain yourself to 1,775 [nautical miles], you basically lose the tails of every launch window,” he said. “About 50% of the window is cut out.”
With that assessment of the heat shield issue complete (which, agency officials said, was reviewed by an independent committee that agreed with the root cause), NASA is moving ahead with preparations for Artemis 2. NASA had been holding off the start of stacking of the Space Launch System solid-rocket booster segments, which begins a clock on their certified lifetime.
“As soon as we walked out of the administrator’s executive council today, we gave direction to the team at EGS [Exploration Ground Systems] to start moving the aft-center segments over,” Kshatriya said. “That will start, essentially, tomorrow.”
On Artemis 1, the certified lifetime of the boosters once stacking of the segments started was 12 months, but that was extended to closer to two years before the rocket finally launched. While stacking is starting now, launch is still 16 months away.
“The theoretical concern is that, because of the compression on the seals and the interfaces, you could have propellant grains migrate from the inner liner and cause issues,” he said. However, with the ability to monitor the segments, and the experience of Artemis 1, he said NASA was confident that the booster lifetime can be extended. “I believe we can get between 18 and 24 months pretty comfortably.”
The delay in Artemis 2 to April 2026 pushes out Artemis 3, which is now scheduled for mid-2027. Nelson said he would be pushing the various companies involved in SLS, Orion, the Human Landing System, and spacesuits to accelerate their work in a long-shot bid to move up the missions.
“We need our commercial and international partners to double down to meet and improve this schedule,” he said, describing meetings with company executives “sometimes unannounced” at their facilities to impress upon them “a shared sense of urgency, and I think we have that.”
briefing
NASA administrator Bill Nelson, deputy administrator Pam Melroy, associate administrator Jim Free, and Artemis 2 commander Reid Wiseman discuss plans for Artemis 2 and the future of the program at a December 5 briefing. (credit: NASA/B. Ingalls)
Will Artemis 2 ever fly?
The timing of the announcement raised eyebrows given the impending change in administrations and, with it, new leadership at NASA. Officials argued the decision was made now to avoid any further delays.
“To the greatest extent possible, we certainly want to defer any decisions about starting or ending programs,” Melroy said. “We’re on a day-for-day slip. We had to make this decision. If you’re waiting for a new administrator to be confirmed and a team to come up to speed on this technical work that we’ve all been tracking very closely, I think that would actually be far worse to defer it.”
She added that agency leadership wasn’t able to brief the incoming Trump Administration ahead of the public briefing since the Trump transition team had not named an agency review team for NASA.
However, the day before, President-elect Trump announced his intent to nominate Jared Isaacman as NASA administrator. Both the timing of the announcement and Trump’s choice took many by surprise. Previous administrations have traditionally waited until after inauguration to nominate a NASA administrator: the first Trump Administration waited more than seven months before nominating Jim Bridenstine, for example.
Isaacman blamed “excessive consolidation among defense and aerospace players” for the problems NASA and others, like the Pentagon, have faced on programs.
Isaacman, meanwhile, was on virtually nobody’s radar as a potential candidate to lead the agency. The billionaire founder of payment processing company Shift4 is best known to the space community as the commander of the Inspiration4 and Polaris Dawn private astronaut missions flown on SpaceX Crew Dragon spacecraft. Those missions, which Isaacman funded, included the first commercial spacewalk that Isaacman performed on Polaris Dawn in September.
“Jared’s passion for Space, astronaut experience, and dedication to pushing the boundaries of exploration, unlocking the mysteries of the universe, and advancing the new Space economy, make him ideally suited to lead NASA into a bold new Era,” Trump stated in his announcement (capitalization in original.)
Isaacman has said little since last week’s announcement about his plans for the agency, but he does have a significant paper trail—or, rather, social media trail—of statements on space topics outside of his own missions.
That included, in October, endorsing an op-ed by Bloomberg founder Michael Bloomberg critical of NASA’s Artemis campaign, including SLS and Orion. “There are government boondoggles, and then there’s NASA’s Artemis program,” Bloomberg wrote. Artemis, he argued, “has so far spent nearly $100 billion without anyone getting off the ground, yet its complexity and outrageous waste are still spiraling upward. The next US president should rethink the program in its entirety.”
“These points are not new, and I agree with most of them, but it’s great to have someone like Mike, with a loud voice, educating people on topics they may not be as familiar with,” Isaacman wrote in a social media post about Bloomberg’s commentary. Isaacman blamed “excessive consolidation among defense and aerospace players” for the problems NASA and others, like the Pentagon, have faced on programs.
Even before Isaacman’s nomination, there was widespread speculation that the incoming administration would at least revisit Artemis, in particular programs like SLS, Orion, and the lunar Gateway. Musk’s current influence with Trump heightened that speculation, and the selection of Isaacman to lead NASA—which still requires Senate confirmation in the new year—further supports it.
At last week’s briefing, though, agency leaders said they believed they were giving the incoming Trump Administration a firm plan to return humans to the Moon using SLS and Orion, along with SpaceX’s Starship lunar lander.
“I think we are handing to the new administration a safe and reliable way forward for us, which is to go back to the Moon, get there before China, to have a presence in cislunar, which is important to our country other than NASA, and to be on the way of Moon-to-Mars,” Nelson said. “I think we’ve got that wrapped up with a bow and I think it’s on its way.”
He seemed unconcerned that the next administration might, for example, replace SLS and Orion with Starship, a topic that prompted questions along those lines at the briefing. “Are they going to axe Artemis and insert the Starship? First of all, there is one human-rated spacecraft that is flying and has already flown beyond the Moon, farther than any other human-rated spacecraft, and that’s the SLS combined with Orion,” he said.
“We have a large decision behind us,” Wiseman said of the Orion heat shield. “A lot of the uncertainty has been removed.”
“I expect that this is going to continue,” he said of the current architecture. “I don’t see the concern that your question raises—although it’s a legitimate question—that you’re suddenly going to have Starship take over everything.”
NASA, of course, won’t be able to cancel SLS and Orion without the support of Congress, including members from states and districts heavily invested in those programs. The attempt by the Obama Administration in 2010 to cancel the Constellation program ultimately led to the end of that program, but Orion continued, as did a shuttle-derived rocket in the form of SLS.
It does, though, offer uncertainty about whether and how those key elements of Artemis will continue. One of the participants at the briefing was Reid Wiseman, the astronaut commanding Artemis 2. “We have a large decision behind us,” he said of that decision to proceed with the mission using the current heat shield but new reentry technique. “A lot of the uncertainty has been removed.”
However, there is now uncertainty, not about how Artemis 2 will fly, but if it will even get off the ground in anything like its current form.
Jeff Foust (jeff@thespacereview.com) is the editor and publisher of The Space Review, and a senior staff writer with SpaceNews. He also operates the Spacetoday.net web site. Views and opinions expressed in this article are those of the author alone.
What Do We Need Astronauts For?
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What is the most effective use of astronauts in the future?
What do we need astronauts for?
by Joe Carroll
Monday, December 9, 2024
The Conversation
The key space exploration challenge to US astronauts is not foreign astronauts, but robotic spacecraft. They travel farther, arrive earlier, survive far worse conditions, and deliver far more data far longer. And they cost less, and don’t trade crew safety versus cost.
We can only settle the Moon or Mars if they have enough gravity for good long-term human health. And we don’t know if lunar or Martian gravity are enough!
Astronauts lost that contest decades ago. And since then, robotic spacecraft have continued to evolve far faster than humans. Artificial intelligence should further speed that evolution. We will make faster progress in exploring space if we move our human space exploration funding to a wider range of uncrewed missions. Don’t redo Apollo.
If space exploration doesn’t need astronauts, then what else might they be useful for?
Since Apollo, their main tasks have been living, working, and testing microgravity effects for longer and longer times, in low Earth orbit. I suggest a challenging extension of those tasks: Identify realistic paths for human settlement beyond Earth.
This task inherently needs astronauts, because we can only settle the Moon or Mars if they have enough gravity for good long-term human health. And we don’t know if lunar or Martian gravity are enough! Besides testing health in lunar and Martian gravity, crews can tackle other settlement challenges, like reducing dependence on Earth. This can make settlements more realistic, by cutting costs and risks.
Human health as a constraint on settlement
Surface gravities in this solar system between 0.09 and 2.3g all fit into three fairly tight clusters, near Moon, Mars, or Earth gravity. Venus, Saturn, Uranus, and Neptune each have within 12% of 1g. But all four pose many serious challenges, including extreme temperatures and pressures. And all but Venus have escape velocities of 21 to 35 kilometers per second. (Forget about ever leaving.) The only other bodies with surface gravities between 0.09 and 2.3g are Mars and Mercury, each with 0.38g, and the six largest moons, each of which has 0.13 to 0.18g.
These numbers matter, because if lunar gravity isn’t high enough to allow good life-long health, forget about settling any moon. And if Martian gravity isn’t high enough, then we must master the challenges of either settling Venus, Saturn, Uranus, or Neptune, or developing spinning free-space settlements that provide enough gravity.
All that we know now is that we have normal health in 1g, but health deteriorates in microgravity, despite decades of refining “countermeasure” diets, medications, and exercise (now about two hours a day). And as more crews stay 6 to 12 months in microgravity, we keep finding new health problems!
Hence human health, specifically in lunar or Martian gravity, is a key constraint on space settlement destinations and types. Space settlers will need good health for the full human lifecycle. We have no data on human health in sustained low gravity. We should be healthier in 0.13 to 0.38g than in microgravity, but we don’t know if degradation of health will stop or just slow down, what microgravity health issues will persist, what countermeasures we will still need or how well they will work and with what side effects, or how well we might tolerate 1g later—or even if we will grow up normally, from conception to adulthood.
I know of no way to determine the health impacts of sustained low gravity without people actually living in sustained low gravity. One option is to keep crews on the Moon and Mars long enough (about one year and then longer?) But another option seems far better and cheaper.
It’s time for artificial gravity (“AG”)
A spinning dumbbell with 7:3 mass ratios can give artificial gravity at both lunar and Martian gravity levels, in LEO. Testing at both levels allows sharing of staff and analysis equipment. Adding a microgravity node even allows tests of commuting from AG to microgravity. (for more details on this concept, see “How to clarify human futures beyond Earth,” The Space Review, December 6, 2021.)
As we go further from Earth, minimizing Earth supplies becomes a key part of making a profit. It’s not the full story, but it’s a key part of half of the full story.
Most proposed AG designs use fast spins (3 to 10 rpm) to reduce facility size and cost. These rates are based on reactions of people in rotating rooms. Many people have negative initial reactions even at 3 rpm, but felt “spin effects” in rotating rooms stay consistent when you turn around. So, you adapt to them. But in AG, the felt effects reverse direction every time you turn around. We won’t know how we will adapt to that until we do relevant tests. My companion article describes how we can do AG spin tests on Crew Dragon.
But longer radii do reduce spin rates and their effects. This argues for the longest practical radius, not the shortest tolerable one. A dumbbell shape gives the longest affordable radius and slowest spin.
Monitoring crew health and even lab-animal health and life cycles need not take much of the crew’s time. They can also take on other settlement challenges, like recycling, growing food, and hosting tourism as a step towards settlements. I discuss these tasks below.
Recycling as a settler technology
On the ISS, food is less than half the total crew supplies. That may also occur in settlements. Settlers must greatly reduce dependence on all external supplies. Recycling is not as sexy as mining celestial materials, but it may be far easier to recycle the midden (which has the right mix of all elements you need) than to find, refine, transport, and process celestial materials into forms as useful as the midden.
We need to recycle much more even on Earth, but recycling will be far more critical for living affordably in space. We can test and refine automated recycling faster and cheaper in LEO than beyond LEO.
But space settlers will need some Earth-based supplies for a long time, and must trade things of enough value to cover all delivery costs. Details may vary wildly from site to site. In contrast, recycling will have far more commonality over all sites, even including Earth.
But while recycling may sustain a settlement, it cannot expand it. Traffic can let it grow. In the last 20 years, the total mass of cargo vehicles that departed ISS and then burned up is over twice the 420-tonne mass of ISS. Most of it was aerospace alloys. And even most of the rest would be considered a high-grade ore, if we found it near a Moon or Mars settlement.
This focus on recycling may be jarring to those who envision paying for supplies from Earth, out of profits from selling water or helium-3. But as we go further from Earth, minimizing Earth supplies becomes a key part of making a profit. It’s not the full story, but it’s a key part of half of the full story. Recycling is a critical settler technology.
Growing food
We recycle most of the air and water on the ISS. But food from ISS plant growth tests is probably less than 0.1% of the crew diet. All other food comes from Earth. Settlers will also need Earth-supplied food at first. But each settler will need about half a kilogram per day, even freeze-dried. That is about twice the settler mass per year. This will drive settlers to grow as much of their food as possible.
LEO should cost about a tenth as much as on the Moon or Mars for testing human health in low gravity, developing settler technologies, and developing commercial space resorts.
The many issues found in testing Biosphere 2 suggest that we should do more iterations on Earth, perhaps at Biosphere 2. Then we can do tests in LEO, at both lunar and Martian levels of AG. The task is not just growing crops, but also managing a microbiome, worms, pests, and more, all in new gravity levels. Doing these tests in LEO will cost far less than on the Moon or Mars. And AG spin in LEO lets us sling sample capsules back to Earth for more analysis. It will make sense to try to settle beyond LEO only after we close most of the supply loops.
LEO tourism as a step towards space settlements
If an AG facility spins slowly enough to prevent unpleasant spin effects, space tourists may prefer it to a microgravity-only facility, because AG offers experiences at Moon and Mars gravity as well as microgravity. Tourists may be attracted more to microgravity, but may spend more time in lunar and Martian gravity, especially if that assists the awkward transition to microgravity. An AG facility with serious health diagnostics and staff for long-term crew can also provide useful medical support for space tourists and can even assess the health implications of low gravity on the elderly.
A spinning resort does complicate views of Earth. But a clear dome on the spin axis allows a de-spun view in microgravity. And de-spun cameras can support hi-res steerable zoomable displays all over the resort.
An AG resort cannot host true microgravity-class lab or fab operations, but can support them indirectly. Traffic to and from an AG resort can reduce times and costs for delivering supplies and technicians to and from a co-orbiting microgravity facility. A local taxi can transfer technicians and cargo between resort and microgravity facility, for service and swapping out supplies.
Graphics of spinning cylindrical settlements with open interiors look appealing, but waste usable space. Some inboard volume can be used for farming and recycling, and some can host low-gravity activities. In AG facilities, an elevator allows easy access to a range of gravity levels. Real gravity can’t offer that. That may be a key attraction in AG settlements, and perhaps even more so in AG resorts in LEO.
LEO remains the place to beat (for now)
LEO should cost about a tenth as much as on the Moon or Mars for testing human health in low gravity, developing settler technologies, and developing commercial space resorts. This is based just on costs of delivering mass to and from LEO versus the Moon and Mars. Simpler LEO crew vehicles further reduce costs, and we can even share them and technicians and equipment with both ends of one AG facility.
Modified Starship stages may launch only once, without fins or TPS, but with an integrated payload. They can be used earlier, more often, and more productively in LEO than on the Moon or Mars.
LEO also allows quicker return to earth in emergency, and can allow much lower radiation doses, particularly in low inclination orbits. This is very relevant if some people plan to stay more than a year.
Beyond LEO
Even on celestial bodies, keeping a space settlement working will depend more on recycling than mining. And recycling is common to all space settlements. What will differ from site to site is the business that pays for continued dependence on Earth or other settlements.
The criticality and complexity of life support and recycling suggest that all free-space AG settlements be checked out in LEO, before going elsewhere. One can boost a spinning dumbbell to escape by thrusting parallel to the spin axis from the heavier end. Thrust changes a flat spin into a conical spin, somewhat like a tether ball.
Trips to the Moon take just a few days. But it may be useful to pair vehicles together in LEO, to test critical hardware at Moon-level AG.
Trips to Mars will require vehicles to enter and land separately. But during a roughtly six-month passenger transit, it seems useful to tether them to provide Mars-level AG with an acceptably slow spin rate.
Beyond that are near Earth objects (NEOs). We may start with million-tonne-class NEOs: about 100 million NEOs are bright enough to see, but there are enough of them to be useful. Some will occasionally allow low-ΔV access. We can send unmanned spacecraft to survey candidates. Later we can send “settlement seeds” to convert suitable NEOs into settlements.
Some theses for discussion
Let me digest the above discussion into seven theses:
Surface gravities near those of Moon, Mars, and Earth are the only ones available for human settlement in our solar system.
A key unknown in where and how we can settle beyond Earth is our health in Moon and Mars gravity, from conception to death.
It is faster, better, safer, and cheaper to test low-g human health and settler technologies in AG in LEO, than on the Moon and Mars.
We should shift US human space exploration funds to robotic space exploration plus human health tests in low gravity in LEO.
Settlers will reduce dependence on supplies from Earth more by recycling, than by mining and processing celestial resources.
It is faster, better, safer, and cheaper to reduce dependence on Earth supplies by developing recycling in LEO, not beyond LEO.
Artificial gravity may be more appealing than real gravity, since it allows easy “elevator access” to a range of gravity levels.
Now let me add four more theses, without elaboration:
We want a long slow-spinning dumbbell-shaped crew facility, to minimize all negative AG spin effects on human health and comfort.
What we learn about human health in lunar and Martian gravity will significantly improve future exploration and settlement plans.
It will be much more complex and costly to keep people alive and supplied on Mars than to transport them to Mars.
Settling all of Mars just doubles our settleable land. Free-space settlements can vastly exceed that. And we can even start in LEO.
A scenario to consider
If you accept many of the above theses, you may be interested in this sequence of six initial steps:
Find crew responses to a range of AG spin rates by spin tests in Crew Dragons, as described in my companion article.
Test the sustained health of crews in Moon and Mars gravity in LEO, as I proposed in an earlier article.
Do more AG tests in LEO, at Moon, Mars, and even Earth gravity: longer crew stays, primate life cycles, crop growth, and recycling.
Expand that facility into a microgravity-Moon-Mars-Earth AG LEO resort, with a long-term staff large enough to support resort operations.
Gradually grow facility capabilities, sustainability, and economic viability, as a test facility, resort, and embryonic settlement.
Use all data on health, sustainability, economics, etc., to refine plans for larger space settlements, both in and beyond LEO.
I doubt that anyone can give good estimates of the cost, schedule, or chance of completing such a sequence. But it is a serious alternative to “human space exploration” that can do far more to clarify realistic human futures beyond Earth. It may also allow faster and broader commercialization of human space, and earlier and broader work on a range of space settler technologies.
If is this is not the best new role for astronauts, what may be better?
Joe Carroll is a mostly retired aerospace engineer. He developed the mission scenarios and tether systems used on SEDS, SEDS-2, PMG, TiPS, and TEPCE. His email is tetherjoe1@gmail.com.
How To Test Artificial Gravity
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An illustration of an artifical gravity test involving a Crew Dragon spacecraft and Falcon 9 second stage.
How to test artificial gravity
by Joe Carroll
Monday, December 9, 2024
The Conversation
But first: Why does artificial gravity (“AG”) matter?
Most people interested in human expansion beyond Earth suggest settling the Moon or Mars first. But we don’t know how much gravity we will need, to avoid the novel health issues we keep finding after long stays in microgravity.[1-7] Many of those problems were found only after 6- to 12-month stays in microgravity, so it seems prudent to test human health at both gravity levels, possibly eventually in multi-year tests.
The five other large moons in our solar system all have about our Moon’s gravity (0.13 to 0.18g, versus 0.16g). And Mars and Mercury have the same gravity, 0.38g. The only other bodies between 0.09g and 2.3g all are within 12% of 1g: Venus, Saturn, Uranus, and Neptune. All four are all hard to live on or return from. So, our solar system offers only lunar and Martian gravity (and with difficulty, terrestrial gravity) for settling.
We know that humans thrive in 1g but not in microgravity, but we know nothing about health in between. In 2021, I suggested how to clarify human futures beyond Earth.[22] We can determine our “gravity prescription” for good health by having people live in a long dumbbell-shaped station in LEO.[20] It can offer lunar and Martian gravity at opposite ends, while using a slow enough spin to avoid sustained negative sensory effects of spin. This can tell us whether and how we might handle long-term living at Moon and Mars gravity, at far lower cost and risk than by actually living on those bodies. And if we do end up needing more than Mars gravity, we must live in AG, in free space.[19] AG tests then become even more relevant. Besides better health, AG offers other benefits to space habitats. Even Moon-level AG may improve design, operations, life support, training, and many other aspects of space facilities.[6]
For any given gravity level in AG, spin rate drives facility radius and cost. Most advocates of AG suggest the highest spin rates they feel reasonable, to minimize the facility radius.[13-16] They usually base this on the responses of people in rotating-room tests. But all such tests are of uncertain relevance, as discussed below.
Sensory effects in rotating rooms vs AG
Early in the space age, Graybiel et al. tested six young soldiers in a rotating room over two days.[8] After that, the rotation stopped and they returned to the room for tests on a third day. The room was round, windowless, and 15 feet [4.6 meters] in diameter, and smoothly rotated about a vertical axis, at rates from 1.71 to 10 rpm. Some subjects reported an initial mild general malaise, nausea, or headaches even at 1.71 rpm, and one vomited at 2.21 rpm. The frequency and severity of reported negative reactions increased at 3.82 and 5.44 rpm. But eventually most of the subjects did fully adapt, even to spins up to 5.44 rpm. One subject had minimal negative reactions even at 10 rpm. And a control subject who lacked normal vestibular function had little response to rotation. Some later studies tested longer adaptation periods, including up to two weeks of sustained rotation.[9]
Some later AG proposals added other constraints.[10-11] One is setting a maximum allowed relative change in gravity from head to foot when standing. This directly sets a minimum spin radius. Another is constraining the change in relative weight when walking with or against the spin. This in turn sets the minimum ratio of tangential spin velocity to assumed walking speed at that radius.
John Charles, then chief scientist of NASA’s Human Research Program, told me that ground-based vertical-axis rotating room tests may not be relevant for estimating the response to the spin of orbiting AG facilities. He said that in rotating rooms, the spin axis aligns with gravity, but in AG, they are at a right angle. A footnote in the Graybiel paper also notes this.[8] I thought this was a minor subtlety at first, but eventually realized that this difference causes completely different sensory effects from vertical-axis rotating rooms. This is worth discussing in detail.
The sensed effects of spin in different spin axes
In a vertical-axis rotating room, standing everywhere but the spin axis requires you to tilt. But each point has a fixed tilt and direction. Horizontal motion adds a horizontal Coriolis force at a right angle to your motion. Facing in any direction, you feel the same amount and direction of motion-induced force in your body coordinates. Walking or swinging your arms causes aiming errors initially. But this effect is consistent, so people adapt to it after several iterations. But if the rotation stops or reverses, people retain their recent spin adaptation. The result is an opposite aiming error at first, as seen the video for Ref. 12.
Compare this to AG. Coriolis effects still make all motion in the spin plane cause a force in the spin plane, at a right angle to the motion. But in AG, that plane is vertical. Horizontal motions cause vertical forces, and vice versa. And unlike rotating rooms where effects are fixed unless you change the spin, the felt force in AG reverses each time you turn around. Adapting to such changes may take far longer, and we may never fully adapt to them. Trying to simulate this in a rotating room requires either smoothly reversing the spin, or lying down, moving your limbs, rolling over, and then moving them again.
You are also directly sensitive to spin even if you don’t move. Room rotation rates down to about 0.5 rpm may be felt if people stay still, but they tolerate it. They also adapt to changes in rate and even direction but that takes time. But in AG, the direction of felt rotation depends on which way you face. Turning around reverses the direction felt. Another turn flips it back. As with ground tests of Coriolis forces, the analogs are reversing the spin, or lying down and rolling over.
But there is one sensory effect of AG that we can test fairly well on the ground. It is a significant weight change that occurs when you walk with or against the spin direction in AG. I discuss this next.
How to test AG weight changes caused by walking
People feel an approximately 5% transient change in weight when an elevator starts or stops. We often stumble a bit if we are moving around then. In AG, walking either with or against the spin changes your spin rate and hence your centrifugal force and weight. If you walk with or against the AG spin at 1 meter per second, you feel a weight change of just 2.1% of Earth gravity per rpm. But at 10 rpm, that is a weight change of 21% of Earth gravity, or 55% of felt gravity in Mars AG.
A Vertical Motion Simulator (VMS) at NASA Ames can provide these changes in felt gravity. The VMS allows a vertical stroke up to 18 meters. This is more than enough to provide the same weight changes as AG, when people walk around. The VMS has fove interchangeable cabins. The largest one has a 1.8 x 3.7 meter floor.
illustration
Consider two people each walking around a 1.2 x 3.0 meter elliptical path, as illustrated above. Moving spots of light on the floor or wall can pace them to allow smooth sinusoidal motion in the long axis. If each cycle takes 8.5 seconds, peak walking speed is 1.0 meters per second. If the cabin oscillates up and down with strokes of 0.76 to 7.6 meters, it causes the same Earth weight changes as walking the same path in AG at spin rates of 1 to 10 rpm.
This test is open-loop, with walking to fit cab oscillation. At higher cost, one can move the cab in response to sensed one-axis motion of one test subject. But open-loop tests are easier, can test two people at a time, and may be enough to limit the acceptable AG spin rates based on this constraint. The VMS can test many people to quantify their sensitivities, adaptation times, and any residual sensitivity. I don’t know a good way to test other felt AG effects other than in orbit, by actual AG spin tests somewhat like the test done on Gemini 11.
Gemini 11: a precursor tethered spin test in LEO
The Gemini spacecraft program actually began after Apollo, to answer time-critical questions that Mercury could not test. Early missions answered most of them, so NASA added new tests to the last few missions. This included passive tethered stationkeeping, using slow spin on Gemini 11, and gravity gradients on Gemini 12.[17]
The Agena’s docking collar on Gemini 11 held a 30-meter flat coil of seatbelt-like tape. During an EVA, the crew attached its free end to Gemini’s docking bar. Later they released Agena and used Gemini’s thrusters to move away and pull out the tape. Then they used other thrusters to spin up to 0.11 rpm. Later they went to 0.15 rpm. The crew did not feel the less than 0.0004g accelerations. The tape tension also caused Gemini to slowly rock back and forth. The crew found the test uneventful enough that they ate lunch during the test. After three hours they released the docking bar, and the Agena and tape drifted away.
The Gemini 11 mission movie is on YouTube.[18] The tether test starts at 10:50. The narrator said it was a test of passive stationkeeping. The Gemini 7 crew had already spent two weeks in microgravity, longer than any planned Apollo mission, so AG itself was of little interest.
Possible AG spin tests on Crew Dragon
Using spinning more than ten times faster, Crew Dragon allows similar tests, but at lunar and Martian gravity. The tests can be simpler than on Gemini, if they use the Falcon second stage as counterweight. This avoids any need for rendezvous, docking, or spacewalks. Any mission with enough free time and RCS margin can do these tests. One might do them on flights for Axiom, Polaris, Vast, Fram2, NASA, and future customers. Releasing data on crew responses to spin could greatly speed AG development.
One can use a “nose-up” Dragon gravity alignment, as before launch. But that requires attaching a strong tape or bridle to Dragon’s nose, before or after launch. Either option seems far more challenging than attaching a bridle inside the trunk, before launch. I suggest starting with nose-down AG spin tests. If there is enough interest in nose-up tests, those details can be worked out then.
Crew Dragon spin tests can focus primarily on finding the spin rate at which unpleasant effects start to occur, and how fast and complete any adaptation is to that spin. During a spin test, the crew can stand, sit, lie down, turn around, look out at Earth, and try other activities while facing in different directions. There is little room to walk, but the VMS can test the effects of walking in AG.
The most important goal from Crew Dragon AG spin tests is to find suitable spin rates and radii for early crewed AG facilities. Another useful goal is to learn whether time and/or activity in low AG either eases or hinders any later adaptation to microgravity. If it eases adaptation, AG spin ops might become regular parts of future crew flights. Another goal might be quantifying correlations between crew responses to ground tests and spin in AG. Any such correlations could let tourists know how well they are likely to handle spin in AG, before they pay for a flight. This should be invaluable for large-scale AG tourism.
AG spin tests of Dragon with attached Falcon stage
The simplest spin test just spins Dragon. But retaining the Falcon stage shifts the center of mass about three meters aft. This allows a longer crew spin radius and is worth doing, before doing later tests with Falcon on a long tape or tether.
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Spin will pull the crew away from their seats. Then can unbuckle either before or after the spin starts, and can sit or stand on the Dragon “ceiling.” It will serve as their floor during the spin test. The crew should have roughly a four-meter average spin radius both in their seats, or standing on the ceiling.
Each test can start at the usual 200 x 200 kilometer Crew Dragon insertion orbit or any other low orbit. Normally, Dragon and Falcon separate then. But here Dragon starts to spin, with the Falcon stage still attached. The spin axis should point near the sun. Then Dragon’s solar arrays can provide full power, and the radiators can avoid the sun. This allows normal power and thermal performance.
Long pauses during spin-up let the crew try various activities and describe their reactions. When unpleasant effects start to occur, they can maintain that spin rate to see how fast and how thoroughly they adapt to it. If they adapt well enough, they may increase the spin, but smaller steps and with longer adaptation times at each step.
But at any time, the crew can end the spin test by releasing Falcon and despinning Dragon, in either order. We don’t know how fast a spin the crew may be willing to test. But being active in a spin of about 3 rpm that gives only 0.04g may be useful, if it finds sustained low-level AG helps crews adapt to microgravity. It can also start to correlate both similarities and differences in crew responses to low-level AG vs 1g rotating-room tests. Spin tests might be repeated on later missions, using chairs, hammocks, and other props to test a wider range of situations. But even without such props, testing another crew or a new spin-up sequence will be useful, and has very low added cost.
AG spin tests with an inflatable room
Adding a “popout” inflatable room to a Crew Dragon can give the crew much more usable pressurized volume, for both microgravity and AG spin tests. There is limited room inside the nose cap to stow it. But it might expand to as much as 2.2 x 3.6 meters (15 cubic meters), as shown at right. The roughly three meters it can add to the crew spin radius may be most useful in tests with an attached Falcon. The added room may also enable more activities in tethered tests.
illustration
Parts of the normal docking interface can securely hold and then reliably release this hardware, to allow later docking and nose cap closure for reentry.
AG Dragon spin rate tests using a tethered Falcon
Spin tests with an attached Falcon stage limit the crew spin radius to about four meters, or seven meters with an inflatable. This requires a fast spin to get much gravity. The table below shows spin rates and velocities using both attached and tethered Falcons. Longer tethers allow slower spin at the same gravity. A tether system can be lighter, simpler, and more reliable if the full length deploys at low tension. Then different spin rates during one flight test will all occur on one row of this table:
Distances in meters RPM vs AG level Spin up ΔV, m/s
Crew spin radius CM-CM Dragon Falc 0.04 g Moon 0.16 g Mars 0.38 g Earth1.0 g μg to Mars g
~4 docked ~12 3 6 9 15 ~13.0
9 36 2 4 6 10 22.6
16 68 1.5 3 4.5 7.5 32.0
36 158 1 2 3 5 49.6
64 284 0.75 1.5 2.25 3.75 66.9
144 644 0.5 1 1.5 2.5 101.2
To generate this table, I assumed an average crew center of mass during spin tests one meter forward of Dragon’s center of mass, and a Dragon mass 3.5 times that of the Falcon stage, after Falcon vents its remaining propellant.
Tethering Falcon to Dragon causes new complications but allows much lower spin rates at each gravity level. This lets us quantify how much the AG level affects the crew’s tolerance of spin. RCS margins or safety may constrain the spin-up velocity. I quantify them later.
As in AG spin tests with an attached Falcon, “nose-down” gravity is easier to do. Releasing Falcon and thrusting away can pull a tape from the trunk. I suggest a 36-meter crew spin radius in the first test. Then 0.04g, Moon, Mars, and Earth-level AG need spins of 1, 2, 3, and 5 rpm. Later tests can use other combinations of length and spin.
A scenario for tethered AG crew spin tests
As shown below, Dragon might pitch up about 60 degrees, release Falcon, and fire four aft Draco thrusters for about two seconds to move away at about 0.2 meters per second. Payout of a roughly 150-meter tape takes about 12 minutes. Near the end, the tape pulls a bridle from the Dragon trunk, and Draco thrusters start the spin-up. The best thrusters for spin-up also cause inward thrust. That brakes the deployment, but then complicates the spin-up a bit.
Initially, Dragon can tilt to null out the inward part of the spin-up thrust. But as tension rises, the bridle will orient Dragon radially. Pulsing the spin-up thrust can keep the average inward thrust below the AG force. Once the spin exceeds about 0.3 rpm, the AG force exceeds even a sustained spin-up thrust. But using well-timed pulses can also damp attitude oscillations, like those seen in the Gemini 11 movie.[18] And good timing of the pulses can also provide useful orbit boosting above the low SECO orbit.
illustration
With a 36-meter crew spin radius, each 1 rpm spin change requires 16.5 meters per seconds of relative tangential ΔV, from either Dragon or Falcon. Dragon has 3.5 times Falcon’s mass but its Dracos have five times higher specific impulse than Falcon’s cold gas thrusters. Here I assume use of Dragon thrusters for both separation and spin-up.
To use the four axial Draco RCS thrusters mounted there, Dragon must open its nose cap. But spin tests just use the 12 aft Dracos, so Dragon can keep its nose cap closed until after the tape is released.
I assume that with cosine losses, the two best-oriented 400-newton Dracos give 320 newtons of useful transverse spin-up thrust each. Then each 1 rpm of the spin-up takes six minutes of firing. Thrusting in only part of each rotation, and just in the best parts of each orbit, allows effective spin up as well as orbit boost. Long pauses after some pulses allow more time for crew to adapt to the higher spin rate and do more tests. If second stage engine cutoff is at 200 x 200 kilometers, a 3 rpm spin-up can boost the orbit to 260 x 260 kilometers. If all pulses are done near one location in the orbit rather than two, spin-up can boost the orbit to 210 x 310 kilometers. That may be useful.
Dragon ends the test by releasing the bridle. If release is at apogee of a 210 x 310 kilometer orbit, with Falcon moving aft then, release can boost Dragon to 248 x 310 kilometer, while slinging Falcon into a roughly 85 x 310 kilometer targeted reentry trajectory. A lower SECO could let Falcon drop even lower. Falcon’s 3 rpm spin should help reduce reentry dispersions.
Spin tests docked with another module
Another spin test option is to first dock with another previously-launched module, like Haven-1. This allows even more usable space than an inflatable like that shown earlier. But it also doubles the spin test mass. For the same AG level and spin rate with Dragon’s Falcon stage as the counterweight, we need about 1.8 times the tape length and 3.6 times as much Dragon RCS propellant. But each flight provides a new Falcon stage and tether. This lets the tape length and strength be customized for each test.
Safety issues
A critical safety issue is to ensure that a Dragon launch abort can occur without a strong tape tying Dragon to Falcon. I suggest stowing the tape and bridle in the Dragon trunk, with the free end only weakly held by Falcon. After SECO, an actuator on Falcon can securely clamp that end.
A second issue is accidental tape severance under load, which causes fast recoil and may cause the tape to foul on part of Dragon. In the Gemini 11 mission movie, the crew said that after they released the tape, it slowly wrapped and unwrapped around Agena. Here a tape cut at far higher tension will wrap the tape around Dragon far faster. If the tape snags then, it could keep Dragon from ejecting its trunk, until RCS thrust or initial reentry heating can melt the tape. To prevent snags, tape should probably be smooth, slick, and stiff. Also, Dragon’s nose cap should stay closed during the test, and any other exposed Dragon features that could cause a snag should be taped over or otherwise modified.
Note that adding an inflatable volume or docking to another module require that the nose cap be open during the test. Both of these cases also provide additional places for a tape to foul on.
A tape wrapping around Dragon wraps in a direction is opposite to that used in yo-yo de-spin maneuvers. But the continued Dragon spin eventually gives a useful centrifugal peel force, as on Gemini’s Agena. And Dragon’s RCS can spin Dragon far faster when Falcon is not attached. The RCS might also create a wobble, or even melt the tape. Using too much RCS may preclude later parts of a mission, but that may be found acceptable if it lets a crew return safely, after an extremely unlikely but not provably impossible sequence of events.
High drag in AG test orbits of 200–260 kilometers greatly shorten debris transit times and populations of untracked orbital debris. This greatly reduces the chances of a tape cut, or a leak in an inflatable that is too large for the crew to immediately patch.
Multi-strand tethers can preclude severance, but only if enough strands are kept apart far enough to preclude a full cut by a several-centimeter untracked object. And if a multi-strand tether is cut, it is likely to offer far more opportunities for snagging.
Severance or inadvertent release of a tape when Falcon is rotating forward could also sling the Falcon and its tape high enough to reach ISS. A Mars-gravity 3-rpm spin could boost Falcon apogee by up to 135 kilometers.[23] A worst-case cut at 260 kilometers could sling Falcon to 395 kilometers. And release at perigee of an eccentric orbit may let it reach much higher. But a suitable spin axis tilt may be able to preclude contact.
Crew incapacitation by spin can be limited by increasing spin in small steps, and waiting until there is enough adaptation before further spin increases. Other safety issues and complications will come up during development, and may require changes or constraints in the scenario above.
Reasons for selecting other key features
Sustained tests at both Moon and Mars gravity are useful because Moon and Mars gravities are the two most relevant non-Earth gravity levels in this solar system. Later flights with different tape lengths can quantify sensitivities to spin rate vs AG level, scheduling of spin up, and other relevant factors.
These spin tests use the spent Falcon stage as the counterweight, so they must be done early in a mission. Spin tests after Falcon departs put the crew only about one meter forward of the Dragon center of gravity. That seems of little value for crew tests. But that may allow useful low-gravity AG lab or fab tests on Cargo Dragon flights.
It would be more useful to attach a bridle to Dragon’s nose rather than its trunk. Then the gravity direction fits the crew seats and cabin layout better. But it seems far easier to stow, deploy, and release a tape from the trunk than to attach a bridle to Dragon’s nose in orbit and later reliably release it. How to do “nose-up” tests can be worked out later if there is enough interest in that orientation.
If desired, Falcon ullage gas and liquid oxygen boiloff can allow some of the spin-up while the Falcon’s avionics batteries stay alive.
For the best Dragon solar array and radiator performance, the spin axis should aim near the Sun. Then Dragon’s solar arrays can face the Sun and the radiators can avoid it. But this does assume that when the RCS tanks are nearly full, Dragon’s stable flat-spin axis puts the solar arrays and radiators on opposite sides of the spin plane, not straddling it. If not, then we may have to rearrange cargo, add a reaction wheel, actively maintain an unstable balance, or limit spin tests to a few hours.
Spin-up thrust can provide efficient orbit boosting during part of each spin in any spin axis, at least near one or two points in each orbit. And as noted earlier, slinging Falcon aft from apogee of an eccentric orbit can cause a targeted reentry, somewhat like the SEDS-1 targeted reentry tether test.[24] One might even disperse small reentry test payloads from the spinning Falcon, before it reenters.
To do spin tests while docked with a module like Haven-1, I suggest discarding that module’s Falcon stage as usual, and using each visiting Dragon’s Falcon stage as counterweight. This allows a different tether length, strength, and RCS test budget for each flight. But using the Dragon’s Falcon stage as counterweight does require that Dragon approach and dock with the module with that Falcon stage still attached. It may be best to vent any residual fuel before that, to prevent complications from sloshing.
Crew Dragon customers may want to add AG spin tests to many flights. They may want to test different spin rates and schedules, activities, and crews. I don’t know how much each test will cost, but I think it is far better to invest in AG spin tests before we try to do any detailed designs of crewed AG stations. Above I baselined a 36-meter crew spin radius. Tests in the VMS and Dragon can guide us to better tests for later AG spin tests, and eventually to a good radius and design for the first long-term crewed AG station.
Possible payload mass penalties from AG spin tests
The main payload mass penalty in tethered spin tests will usually be from RCS use. Consider a 3-rpm spin at Mars AG, with 3.5:1 mass ratio. It needs about 0.2 meters per second for Dragon to separate, plus 49.6 meters per second tangential ΔV to spin up, each at assumed 0.8 cosines for the best-oriented thrusters. At 300 seconds of specific impulse, this takes 296 kilograms of Draco RCS propellant. If the pulses occur when the thrusters aim furthest aft, the boost impulse may be about 90% of the spin impulse. This can boost the average altitude of the Dragon and Falcon assembly by 60 kilometers. The boost can be circular or eccentric, as desired. If Dragon releases the bridle at apogee, when Falcon spins aft, it can boost Dragon from 210 x 310 kilometers up to 248 x 310 kilometers.
To compare, using the axial thrusters with no cosine loss to boost just Dragon from 200 x 200 kilometers to 248 x 310 kilometers takes 220 kilograms of RCS. So added RCS use for this case is 296-220 kilograms or only 76 kilograms, but only if such an orbit boost is needed. For spin-up with Falcon attached (and spin-down after release), net RCS per rpm is smaller.
There is also a small RCS cost for reboost due to a large drag area and low average altitude. The full spinning assembly may have an average coefficient of aerodynamic drag of about 160 square meters, versus 40 square meters for Dragon itself flying end-on. The added drag at a 230-kilometer average spin test altitude should cost less than one kilogram per hour of added RCS.
There are other payload mass penalties. Spectra and Dyneema have the highest strength/weight of any commercial fiber, and were used in most successful tests of long space tethers.[24-27] A very low ratio of absorptivity to emissivity keeps them very cold. This further increases strength and toughness and greatly reduces creep. But they must avoid RCS plumes, unless we actually want to blow away or melt a tether. With a 14-tonne Dragon and 3.70 meters per second squared Martian gravity, tension is 52 kilonewtons. With SF=6, the mass of a 150-meter Spectra or Dyneema tape is less than 30 kilograms. If sized just for Moon gravity, it is less than 13 kilograms. Support hardware may add 10 to 20 kilograms. Tests using an inflatable volume and its attach interface will require extra hardware.
There is one more mass penalty: added items needed to make low-gravity spin tests useful. Food, water, and air needs will not change if a test ends during planned phasing to reach ISS. But the crew will need some hardware for useful spin tests, and added supplies on non-ISS missions. AG spin tests may also lead to later tests that need more supplies, test props, and perhaps some AG lab experiments.
RCS and tether sensitivities for other spins and lengths
With a fixed tether length, RCS mass penalties and altitude boosting both scale with rpm, but the tether loads and mass scale with centrifugal force and hence rpm squared. But if you compare different spin rates and lengths with the same gravity, tether mass scales with roughly 1/rpm², and spin-up ΔV scales with 1/rpm. If RCS use or worst-case Falcon altitude are too high for a desired case, one can reduce RCS needs and test altitude by using a shorter tether and faster spin for the same maximum gravity. One can reduce RCS use by retracting tether after spin-up, but at higher hardware cost and failure modes.
AG spin tests with Dragon docked to another module will be dedicated missions. If that module has the same mass as Dragon, tape length grows by 1.8 times, and tape mass and RCS use both grow by 3.6 times. And RCS use won’t displace any later boost, except for any module re-boost. Such AG tests will have higher costs, unless Draco thrusters are added to Falcon to allow spin-up from the lighter end.
What gravity levels should early AG space stations use?
The most important sustained early AG tests should focus on the health of humans in Moon and Mars-level AG. Such a facility can also do other biological tests at those gravity levels, including animal gestation.[21] It also seems prudent to learn the effects of lunar and Martian gravity on crop-based ecosystems, in AG in LEO, before we try to settle the Moon or Mars. And we can get far better test results, with fewer complications, if the tests don’t also include high GCR doses, abrasive regolith, or toxic dust.
I have not found clear early payoffs for AG levels between Moon and Mars gravity, or between Mars and Earth gravity. But if AG tests at Mars gravity show that we really need higher average gravity, then living at least most of the time in AG at 0.5 to 1g will have to be the focus of any realistic plans for human expansion beyond Earth.
illustration
Much lower gravity levels may have some value, for lab & fab more than crew. The figure above[23] suggests that many processes have different minimum and maximum gravity tolerances, with some overlap. Slow-spinning crew-tended AG can offer low enough gravity near the spin axis for some “microgravity” processes, while easily settling stored fluids in nearby tanks. Useful testing of low-g AG processes might be done on cargo Dragons, using payloads located both along and near the spin axis.
Implications of AG spin tests
As discussed earlier, there are large differences between the felt effects of vertical-axis rotating room tests and AG. Those differences could plausibly allow higher rpm in AG than in rotating rooms. But AG will probably require slower spins, because each time you turn around, spin sensory effects stay the same in rotating rooms, but reverse in AG. That should affect adaptation time and completeness.
But we don’t know! This is a critical uncertainty preventing prudent investment in commercial AG stations. In addition, the thresholds and severities of reactions to AG spin may vary with the individual, spin rate, gravity level, facility architecture, type of activity and motion, adaptation time, alertness, and motivation. We may need only typical responses to make a good business decision, but we will need to know the sensitivity to many of those details to design a competitive facility.
Weight-change tests on the VMS plus AG spin-rate tests on Crew Dragon can enable realistic AG designs, and perhaps even predict responses of individuals, if we can correlate AG spin test data with ground test data. AG with “slow enough” spin rates is also useful for all long crew trips, as well as LEO resorts and spinning free-space settlements and colonies. Long crew stays in Moon and Mars-level AG will do much to clarify health constraints on human future expansion beyond Earth.[22]
To experience sustained free fall, you must be in space. Sustained lunar and Martian gravity are also available only beyond Earth, either on those bodies or in AG. To date only a dozen astronauts have experienced lunar gravity, and then for only one to three days each. And nobody has yet experienced sustained Martian gravity, real or in AG. Parabolic flights can give 30 seconds of microgravity for people floating inside an aircraft, even if there is some turbulence. But parabolic arcs providing lunar or Martian gravity give bumpier rides.
AG can offer both free fall and sustained lunar and Martian AG. Nearly all tourists in an “AG resort” will try free fall, but most may spend far more time in lunar and Martian gravity, which are even more novel, and easier to adapt to. In contrast, both real gravity and free fall offer only one gravity level, not three. But AG tourists will want any spin adaptation to be brief. They will also want a slow spin (i.e., the longest affordable radius.) This can reduce all spin sensory artifacts. There will only be AG tourists if they really enjoy their stay in AG, and don’t just tolerate it. If we can correlate ground test responses with those in AG spin, this could be invaluable for both prospective tourists and resort operators.
Questions for AG spin tests to resolve
What is the lowest AG level that allows early activity without the adaptation problems seen in microgravity?
Does sustained slow-spinning low-gravity AG either help or hinder a later adaptation to microgravity?
What AG spin rates trigger negative reactions, and how fast and how much do we adapt to them?
How much does the AG gravity level affect the spin rate thresholds that trigger negative reactions?
What are the lowest AG levels for easy walking, sitting in a chair, drinking or eating at a table, etc.?
Do people really enjoy Moon and Mars-level AG, if the spin is slow enough to avoid problems?
What AG spin rate and maximum gravity might make sense on Havens and larger AG stations?
What AG levels and spin rates may be best for lab and fab processes, space resorts, or settlements?
Will most tourists adapt to an AG resort’s spin at arrival, or need to stay at a lower spin first?
Conclusion and recommendations
Long crew stays on ISS keep uncovering new health problems in microgravity. Decades of microgravity countermeasure refinements have helped, but don’t fully stop human health degradation.[1-7] In this solar system, the only gravity levels available between 0.1 and 2 g are Moon and Mars levels (six and two bodies, respectively) and Earth (five bodies, with all but Earth being very challenging to settle.)
But we don’t know whether lunar or Martian gravity allow sustained good human health, or what countermeasures may still be needed, or how well they may work, or with what side effects. Testing of sustained health at both lunar and Martian gravity can clarify realistic human futures beyond Earth: eight bodies, or two, or just spinning free-space settlements. We could test health by long crew stays on the Moon and Mars—or far sooner, better, safer, and cheaper in LEO, in a slowly spinning AG dumbbell.
But we don’t yet even know what AG spin rates crews can handle, without queasiness or other discomforts that affect performance or health. We need relevant AG spin tests to find suitable spin rates and facility radii. Crew comfort and performance are likely to drive us toward the longest affordable spin radius, more than the shortest plausible one. Tests in the VMS and Crew Dragon are the first steps. References 20 to 22 discuss how and why we need to find the “gravity prescription,” to ensure good human health beyond Earth.
I have five recommendations:
Use NASA’s VMS to test the reactions to weight changes caused by walking in AG.
Investigate potential business opportunities for commercial AG facilities in LEO.
Get answers to the questions below, to see if tests like those proposed here are workable.
Start envisioning what crews can do during spin tests, to make the results most useful.
Pursue ways to work on AG spin tests with Crew Dragon customers and SpaceX.
Technical questions for experts
Dragon layout
Is the cabin ceiling flat and strong enough for the crew to stand on in up to 0.37g? If not, can that be fixed?
What is the usable volume for crews in “nose down” AG, and can the seats easily move out of the way?
Can the Dragon/trunk interface handle about 50 kilonewtons tension, both static and during release in AG spin?
How and where can the trunk stow, deploy, and release a tape and bridle, at loads up to about 60 kilonewtons?
Can we cover all exposed “snaggable” Dragon details during a tethered spin test, by tape or anything else?
What size is the “payload envelope” under the nose cap, that could hold a stowed inflatable module?
Is there a practical way to secure a bridle for Dragon nose-up AG tests, and route it to the Falcon?
Dragon RCS
Could RCS propellant acquisition be a problem in any AG direction, up to Martian gravity?
What are the cosine losses and torques for the Dracos that give the most efficient thrust for flat spin-up?
How much lower specific impulse do the 12 scarfed-nozzle aft thrusters have, versus the four axial nose thrusters?
How much net extra RCS propellant is available for AG spin tests, on ISS or other missions? (100 kilograms?)
Operations
How low can the Crew Dragon deployment orbit be, and what altitudes are acceptable during phasing to ISS?
Does Crew Dragon have any time or other limits on parking at low altitude, other than drag reboost?
How many kilograms per day does Crew Dragon need for a crew of four for water, food, air, and all other supplies?
Can Dragon’s nose cap stay closed for hours, until an AG spin test ends and the tape is released?
What may limit Crew Dragon spin test durations, if long-duration AG tests become of interest?
Can Dragon safely release an attached Falcon while in a 3–9 rpm flat spin?
Dynamics & control
Can the inertial platform and controls handle AG & 3–9 rpm flat spins, with or without Falcon’s upper stage?
In a stable flat spin, do Dragon’s solar arrays stay on one side of the spin plane, or straddle it?
If the arrays straddle the spin plane, is there a viable fix (reaction wheel, active balancing, etc.)?
Does a flat spin with solar arrays on one side of the spin plane also allow adequate communications links?
After SECO, what is the mass ratio of Crew Dragon to a vented Falcon second stage (near 3.5:1)?
Where is the Crew Dragon CM after SECO, with seated crew, both with and without an empty Falcon?
Can the controls provide near-optimum automated pulsed spin-up and boost (with crew inhibits)?
Falcon stage 2
How and where should Falcon weakly hold the free tape end, and later it clamp it (up to 60 kilonewtons load)?
How long will the standard Falcon second stage batteries keep the avionics alive after engine cutoff?
How much impulse can a Falcon stage 2 get from its ullage gas, and also with boiloff of minimum LOX?
Can a roughly 85 x 310 kilometer orbit target reentry of a spinning Falcon well enough? If not, then what perigee?
Random questions for others
What useful activities and AG tests can crews do in Dragon, with its nose either up or down?
How much sustained gravity and/or jitter may various useful “microgravity processes” tolerate?
What gravity levels, spin rates, test durations, and issues are of interest to Crew Dragon customers?
What useful spin tests needing a centrifuge too large for ISS might be done during Dragon AG tests?
What other obvious or unobvious “gotchas” do we need to identify, understand, and resolve?
References
Human health in zero or low gravity
M. Roach, Packing for Mars: The Curious Science of Life in the Void, Norton, 336 pp paperback, 2011.
S. Kelly, Endurance: A Year in Space, a Lifetime of Discovery. Knopf, 400 pp, 2017.
K. & Z. Weinersmith, A City on Mars: Can We Settle Space, Should We Settle Space, and Have We Really Thought This Through? Penguin Press, 448 pp, 2023. Some homework for future space settlers.
G. Nordley, Surface Gravity and Interstellar Settlement.
G. Clement et al, Human Research Program Human Health Countermeasures Element Evidence Report, Artificial Gravity, Ver. 5.0
J. Van Loon et al, 2024 preprint
Lectures at Baylor Center for Space Medicine.
Tests and analyses of human response to sustained spin
A. Graybiel, B. Clark, and J. Zarriello, Observations on Human Subjects Living in a “Slow Rotation Room” for Periods of Two Days, 1960.
F. Guedry, R. Kennedy, C. Harris, and A. Graybiel, Human Performance During Two Weeks in a Room Rotating at Three RPM, in NASA and US Naval School of Aviation Medicine Joint Report, 1962.
B. Cramer, Physiological Considerations of Artificial Gravity, in Applications of Tethers in Space, vol. 1, p. 3:95-107. NASA CP 2364, 1983.
J. Lackner and P. DiZio, Adaptation in a rotating artificial gravity environment, Brain Research Reviews, Vol. 28, Nov 1998, 194-202. Argues that 10 rpm AG may be ok.
YouTube video. see 2:10 to 2:50 for adapting to spin, and the aiming error after a stop at 5:40-5:50.
Crewed AG architectures and tests
T. Hall. Artificial Gravity. Many useful AG papers and other AG items, all downloadable.
R. Olabisi and M. Jemison, A Review of Challenges & Opportunities: Variable and Partial Gravity for Human Habitats in LEO, 2022. An extensive AG literature survey.
C. Pengelley, Preliminary Survey of Dynamic Stability of a Cable-Connected Spinning Space Station, Journal of Spacecraft and Rockets 3:10, 1456-1462, 1966.
B. Joosten, Preliminary Assessment of Artificial Gravity Impacts to Deep-Space Vehicle Design, JSC-63743, NASA, 2007; 1g at 4 rpm, uses nuclear reactor as counterweight.
D. Lang & R. Nolting, Operations with Tethered Space Vehicles, in Gemini summary conference proceedings, NASA SP-138, 1967, pp. 55-65.
Gemini 11 mission movie. Tether test starts at 10:40 elapsed time.
G. O’Neill, The High Frontier, Human Colonies in Space, Space Studies Institute, 360 pp paperback, 2019 ed.
J. Carroll, Design Concepts for a Manned Artificial Gravity Research Facility, 2010.
J. Carroll, What Might Partial Gravity Biology Research Tell Us? AIAA, 2015.
J. Carroll, “How to clarify human futures beyond Earth”, the Space Review, Dec. 6, 2021.
Space tether analyses and overviews
J. Carroll, Guidebook for analysis of tether applications, 1985.
J. Carroll, Lessons Learned from Five Orbital Tether Tests, 2024.
Wikipedia article on space tether flight tests.
M. Cosmo and E. Lorenzini, editors, Tethers in Space Handbook, 3rd edition.
E. Levin, Dynamic Analysis of Space Tether Missions, Adv. in Astro. Sci., Vol. 126, Univelt, 453 pp, 2007.
Joe Carroll is a mostly retired aerospace engineer. He developed the mission scenarios and tether systems used on SEDS, SEDS-2, PMG, TiPS, and TEPCE. His email is tetherjoe1@gmail.com.
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