Thread: SpaceX - On to Mars

The second and especially the third method of landing require powerful engines to brake the speed for soft touchdown. Dragon already has those engines. It is totally unlike other spacecraft in that regard.

All manned capsules have powerfull rocket engines during launch. They are necessary to save the astronauts in case the rocket fails. Rockets are safer than in the past but catastrophic failure is still possible.

The NASA Orion spacecraft in an abort test shows how NASA does it. Basically the same method was already used for Apollo.



That abort booster on top of the Orion does not only look massive, it is heavy, it alone has approximately as much weight as the Dragon capsule including the abort engines and fuel. This test was with landing in the desert. Any real abort in Cape Canaveral would end in the sea for a softer touchdown. At some point during launch that booster will be dropped, it won't go into orbit. The massive booster with quite extreme acceleration is needed to get away from the solid rocket motors on the planned launch vehicle, the SLS. Solid rocket boosters cannot be shut down or if they are burning debris is all over the place endangering the parachutes. Acceleration is at a level where injuries are likely, but are accepted to safe the life of the astronauts.

Boeing CST-100 uses a different system but also extremely high acceleratiion, because the Atlas V rocket uses solid rocket boosters as well, maybe one, maybe two for launch of CST-100.