How does the SpaceX Starship design accommodate uneven landing surfaces that might not be stable under the weight of the vessel?

I don't understand how SpaceX's Starship would be able to land on unprepared surfaces on the Moon or Mars. It is 50 meters tall, with 6 relatively small landing legs, so to me that sounds a lot like a tall building with no foundations. What are the odds of finding a perfectly flat level surface that won't yield under the enormous pressure on each of the legs?

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    $\begingroup$ SpaceX's own concept art? google.com/amp/s/www.geekwire.com/2019/… Also the concept of the Starship is that it can function as a primary exploration vehicle. $\endgroup$ – Ags1 Oct 14 '19 at 12:51
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    $\begingroup$ Starship is 50 meters (~150 feet) tall minus the booster. On Earth Starship currently stands on concrete - very different from the martian or lunar regolith. The issue is not whether the ship can support itself, which it clearly can, but how we can be reasonably certain the unknown regolith on the Moon or Mars can support it. $\endgroup$ – Ags1 Oct 14 '19 at 20:38
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    $\begingroup$ Also whether and how the Starship design can cope with imperfections like slight inclines or surface rocks. $\endgroup$ – Ags1 Oct 14 '19 at 20:45
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    $\begingroup$ This runs dangerously close to the internet meme "I see a problem I can't solve so hundreds of engineers at SpaceX must be wrong." Perhaps you could reword it as "How does the Starship design accommodate uneven landing surfaces? " $\endgroup$ – Carl Witthoft Oct 15 '19 at 14:11
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    $\begingroup$ I will clarify the question body along those lines. I don't mean to suggest the SpaceX engineers are wrong, I simply want to understand how the problem can be resolved. $\endgroup$ – Ags1 Oct 15 '19 at 19:09

In my experience, I've noticed that SpaceX uses a lot of temporary components until such temporary components need to actually be tested. Since the legs of MK1, MK2, and most probably MK3 will never see uneven soils rather than concrete landing pads, they will most likely just have simple legs. After a few successes with MK3, we should start seeing much more articulate landing legs that will dynamically adjust to uneven terrain. But for now, it's just an additional engineering effort that is not yet ready for testing. SpaceX has demonstrated that it doesn't put the cart before the horse with many components (unless it's for a press conference, then they do get creative at times!)


Quick answer is all I have time for now -- if someone wants to do a more detailed and referenced answer, please feel free and I'll delete this:

While it's very big, its mass is not that high, and gravity is low. On Mars, for instance, it needs about 150 tons of fuel, plus 100 or so tons of vehicle (mass) to get back to orbit. Under Mars gravity thats only just under 100 tons of weight on the legs -- a couple of fully loaded trucks. It's not surprising that a large truck can drive across a desert supported only by the contact patches of 16 tires.

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    $\begingroup$ Ok... Now make the trucks vertical, stack one on top of the other, crowd all the wheels around the base, and leave it standing there for a year waiting for an Earth-return launch window? $\endgroup$ – Ags1 Oct 14 '19 at 7:13
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    $\begingroup$ Which brings us to the question of what Mars soil is like mechanically. We should have at least some idea of that by now from the various landers and rovers. It's will be somewhat different from Earth -- no liquids, so no muddiness. $\endgroup$ – Steve Linton Oct 14 '19 at 7:39
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    $\begingroup$ I have a hunch that when large, fully loaded trucks drive across a desert they do it on terrain already known to be amenable to truck driving whereas on Mars there is (disappointingly) not so many previously characterized deserts. $\endgroup$ – uhoh Oct 14 '19 at 8:13
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    $\begingroup$ The landing may also serve to blow away (or even melt) some of the surface material.As someone once said of Project Orion -- "you don't have to worry about choosing your landing site, by the time you get to it it'll be flat!". $\endgroup$ – Steve Linton Oct 14 '19 at 14:23
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    $\begingroup$ Lower surface gravity, perhaps unintuitively, means that an object at rest is less stable, easier to topple than in 1 g. That is why Apollo rovers and landers had such a wide base and low center of gravity. Even if it can stable itself at a Moon landing, tourists moving towards the windows at 50 m height could make it lean over, unless they iterate the design somehow. $\endgroup$ – Miles Mutka Oct 14 '19 at 19:10

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