Since I was a young child Mars held a special fascination for me. It was so close and yet so faraway. I have never doubted that it once had advanced life and still has remnants of that life now. I am a dedicated member of the Mars Society,Norcal Mars Society National Space Society, Planetary Society, And the SETI Institute. I am a supporter of Explore Mars, Inc. I'm a great admirer of Elon Musk and SpaceX. I have a strong feeling that Space X will send a human to Mars first.
In a few years SpaceX's Dragon spaceships could be taking American astronauts to the ISS, but can ihey take astronauts further out? To the Moon and beyond? Elon Musk hinted as much when he mentioned that Dragon's heat shield could handle a return from the Moon or Mars. But it takes more then a heat shield to conduct a deep space mission so lets look at the Dragon a bit deeper. Firstly lets compare it to other spacecraft.
Apollo(CM) : Volume- 6.2 sq m Mass - 5.56 MT
Soyuz: Volume 10 sq m Mass 7.07 MT
Orion Volume 19.55 sq m Mass 8.9MT (thats for the capsule only, the service module is another 12.3 MT)
DragonVolume 10 sq m Mass 4.2 MT
We know that Orion and Apollo can do Moon missions, that's what they were designed for. In fact Orion doesn't even need a Heavy Lift Launch Vehicle. LockMart have recently proposed aFarside Moon missionfor Orion (he full 21 MT vehicle) using a Delta V Heavy . So the much lighter Dragon should certainly be able to do Lunar mission. Also, do remember theFalcon 9 Heavyis amore powerful rocket then the ELLVs.
However a mission further out to say, a NEO asteroid, is another matter. The spaceship would need to operate for longer periods and be large enough to carry enough consumables for the voyage. Not to mention have enough room to house the astronauts in reasonable comfort. Lockheed Martin came up with a proposal for anasteroid mission with Oriontoo. They proposed using two Orions, one for the two person crew and another for the consumables.
Even two Dragons would have only slightly larger volume than a single Orion so that's out. However there may be away around the problem. Underneath the heat shield there the trunk. It contains the solar panels and radiators but not much else. There's up to 34 sq m of unpressurised cargo space. That cargo can be a pressurised module. Egress from the capsule to the module would need to be provided . A hatch would be ideal although it would need to be cut through the heat shield. However the MOL program successfully flight tested a Gemini capsule with a connecting hatch back in the 60's. Such a setup would provide Dragon with a more then double the volume of two Orions. So Dragons for deep space? Maybe.