New Shepard of Blue Origin separates the crew capsule from the booster. The crew capsule is in free fall for a while, then the parachutes open and finally the landing rockets give a brief impulse to land it softly. Meanwhile the booster free falls without parachutes and fires to almost hover to also touch down softly. Actually, it looks to me that the crew capsule dingles more than the booster does (during the last test linked to below).

Wouldn't it be simpler and safer to skip the separation and the parachutes and the double touch down impulses, to instead keep the crew capsule on top of the booster to land both at once still integrated? The crew capsule could rely on its launch abort system to function also as a landing abort system. To separate only when it increases safety to do so, instead of every time.

In this video of the test launch 19 June 2016, the booster landing looks softer than the crewed capsule landing. The time in free fall for the booster seems to last 5 minutes (from about 2:00 to 7:00 in the video). For the crew capsule, free fall lasts only 40 seconds longer (until the drogue parachutes unfold) or maybe 100 seconds longer until the main parachutes are unfolded. Is that difference of free fall time, which I suppose is what their customers are in demand of, worth the extra complexity and risk? Couldn't it be made up with a simpler integrated design? Is it maybe designed to give experiences more relevant to planned orbital launches, and thus by intent in itself not optimal for suborbital crew launches?

  • 2
    The max G the rocket can bear might be higher than that of the humans. Also, suicide burn is probably scary for paying passengers. – Antzi Nov 1 '16 at 7:20
up vote 7 down vote accepted

It would be extremely unstable. There are 2 things that weight a lot on an empty rocket, the capsule and the engine. With the two of them on opposite sides, the rocket would become extremely unstable. Separating the two allows for the entire system to be more stable. This is particularly important when it is on the ground, where it could easily tip over if the capsule was still attached.

Also, having the system designed to separate allows for an easier integration of the launch abort system. The two have to separate already, minimizing most of the gain that would otherwise be found.

  • Couldn't parachutes on the integrated booster+crew module, or even the crew module firing its braking rockets from the top of the integrated stack at landing, effectively stabilize the landing with force from above the center of mass? Or designing the crew model around the bottom of the launch stack instead of on the top of it? – LocalFluff Oct 31 '16 at 21:15
  • They could stabilize it when the parachutes are deployed when in the atmosphere. I suspect it's the very high atmosphere (20 km or so) as well as the on the ground situation that having them as two separate vehicles helps. – PearsonArtPhoto Oct 31 '16 at 21:24

There's 2 major reasons: safety and practicality

Safety: If you look at the history of booster landings it is not a proven technology, the reliability is not good enough for safety. Don't get me wrong, it's amazing that they can land a booster for re-use, and it works a good portion of the time, however when it goes wrong it goes very, very wrong very fast. If a leg doesn't lock properly, a thruster cuts out at the wrong time, or the booster lands just a bit too fast then you will have a fireball and then you are dependent on the launch abort system to save the lives of the crew. Imagine you have a situation where a leg fails on landing: the booster starts to lean, then the launch abort system activates but sends the capsule off at an angle which doesn't leave enough height for chute deployment the crew in that scenario is dead.

Practicality: the capsule is heavy, therefore to land with it the booster would need a significant amount of additional engineering to handle the loads involved. That adds weight. The booster would need significantly more fuel in order to land that additional weight, which requires more fuel to lift that extra fuel. All that additional fuel means a significantly bigger rocket, therefore more expensive.

It's cheaper and safer to use a parachute system.

  • Wouldn't a launch (and here also landing) escape system be required to function even if fired within the seconds it takes for a landing leg to break, and to deal with a non-vertical launch start? The booster should be practically empty at landing and would not represent a great explosion risk. Now, I'm sure they've made the trade offs very carefully, actually, they have demonstrated it. It just isn't obvious to me how the trades played out like this. – LocalFluff Nov 1 '16 at 13:37
  • I think the best point of this is ensuring the booster doesn't collapse upon landing. That would require significantly more engineering to correctly manage. – PearsonArtPhoto Nov 1 '16 at 14:23
  • SpaceX's landing failures have been pretty spectacular @LocalFluff, even a small (comparatively) explosion is still an explosion. Why introduce the risk? – GdD Nov 3 '16 at 8:12
  • @GdD It can be a good idea to do a general fueling rehearsal IFF the real payload is NOT aboard. I do realize now that landing an empty booster stage is easier than one top heavy with a crewed capsule. I still suspect that the suborbital thing is a test rather than a serious business idea of its own. An ambitious reliability commitment. – LocalFluff Nov 3 '16 at 11:28

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