Can a rocket really stand on its own engine bell?

[Xavven]

In KSP we launch early-career rockets without launch clamps and without landing legs, and the engine bell sitting in the dirt. In addition, many players complete their first Mun landings by sitting the rocket's engine bell directly on the ground. I have three questions related to this:

1. Can the *edge* of an engine bell really support the weight of the whole rocket if it were standing on the ground directly? Of course when in flight, common sense would dictate the engine bell must support the weight of the whole rocket under multiple G when it's running, but isn't that force spread out across the entire bell and combustion chamber, not concentrated on the rim? Could the bell crumple if you tried to land on it?
2. Imagine a lander without landing legs coming in to land on the Moon. As the engine approaches to mere inches above the ground, and there is less and less room for exhaust gas to escape, how does this affect the stability of the landing craft?
3. Are there any real life examples of rockets landing or taking off directly on the engine bell, without legs or an elevated launch rail of some kind?

[MaverickSawyer]

Nope, not possible in real life.

[Ultimate Steve]

If you custom made a nozzle so it could be landable, in theory it could work, but besides that or landing on a low gravity body like an asteroid I don't see it happening.

But there is one real world example I can think of. Apollo 15 landed a bit hard and on some terrain sloped in just the right way that the descent nozzle actually contacted the surface and got bent up before the landing legs took the rest of the weight.

The damage isn't super prominent but it is surely noticeable.

[Green Baron]

Oh, somehow good feeling to see it happening to the cracks too

Edited December 23, 2018 by Green Baron

[cubinator]

I dunno, the SSME looks pretty sturdy as far as engine bells go. Of course, there's no spacecraft with that engine where landing on it would end well. A small craft with a thick, sturdy bell landing on the Moon might be all right, but why bother when it's so much better to put legs on it.

[tater]

I can't imagine this being a thing in RL, ever. An accident like Apollo 15, above, might result in an engine that functions at some level afterwards, but I'd not want to trust anyone's life on it.

[YNM]

I think if someone go out and try it, there are limitations at which below it is possible, but above it for all reason and purposes it's impossible.

Edited December 26, 2018 by YNM

[DDE]

I have an absolutely concrete answer.

Some rockets should be able to. All of them are SLBMs made at Makeeyev.

One of their signature length reduction schemes is to use the main engine as the bottom endcap for the UDMH tank, attaching it by the skirt. Thus the skirt bears all of the thrust loads.

Edited December 24, 2018 by DDE

[mikegarrison]

That Apollo 15 picture looks so kerbal. ("Oh, the landing legs didn't take all the weight? No problem, we'll just land on the engine.") Good thing for that mission that they used separate descent and ascent stages instead of a one-stage lander.

As for the issue of the exhaust gas, I believe the math for that would work much like a wing in ground effect. Because the ground acts as a reflection plane, the effect on the ship would be the same as if there were a reflected thruster firing from a reflected ship pointing in the opposite direction. This would hold true as long as the conditions for potential flow were still valid.

[Xd the great]

Well, engine bells thick enough to stand on will have cracking from thermal loads.

Remember that one rocket engineerer managed to snip 4 feet of engine bell by hand tools.

[V7 Aerospace]

It all depends.

Obviously the 2950 metric ton Saturn V will not stand on 5 F1 Engines, but model rockets that only weigh a few kg will happily sit on their bells. Gravity as well is a large factor, if you built a strong enough engine bell on a descent stage for a light lunar landing craft, it may well be a suitable alternative to a separate landing gear system.