[thereisnospork]

Assuming the landing is soft enough to survive, shouldn't it be fairly trivial for the astronauts to disembark and right the lander? To the extent anything in space is trivial.

Even if it's a bit more than doable by hand a ratchet jack should make short work of it.

[cpgxiii]

The Apollo LEM, only craft that has ever taken humans to the moon's surface, weighted somewhere around 20,000 kg after landing. Since it only ever operated in space and lunar gravity, it could be built with a much higher mass fraction than a rocket launched from earth requires - greater than 30%, where a Falcon 9 in comparison has a mass fraction below 5%. Even then, the LEM structure had to be built incredibly lightly. While the LEM structure could obviously be lifted by crane and survive launch and docking stresses, those were are at designed points in the structure. Without the presence of a crane capable of lifting the whole LEM, righting an LEM that had landed on its side would have been effectively impossible. Basically all of the modern proposed manned lunar landers are considerably larger than the LEM, and thus considerably heavier.

For comparison, a craft built for earth launch mass fractions probably wouldn't survive falling over in the first place - when that happened to a Falcon 9, the whole rocket simply exploded.

[stonemetal12]

>shouldn't it be fairly trivial for the astronauts to disembark and right the lander?

I don't think that is an assumption you can make. In the worst case scenario the lander lands on the door. In which case the only way to disembark is to lift the lander.

[jethro_tell]

Assuming you have jack points in the right place based on the way it tipped over.

[toss1]

Yup, jack points in the right place, jacking equipment with sufficient range of motion, AND solid lunar soil in the right place under the jack points.

Plus, you've got to get the whole jacking operation done without damaging any of your main or control thruster rockets, and without tipping past the upright point over to the other side, or just effectively rolling onto an adjacent side.

I wouldn't want to go on a craft where [jacking it back upright] was in the top ten on the list of recovery options to get home.

[rkagerer]

All the extra mass budget would likely be better spent on a more robust attitude control system to avoid flopping over in the first place. Unless you need it for something else anyway.

[thereisnospork]

>I wouldn't want to go on a craft where [jacking it back upright] was in the top ten on the list of recovery options to get home.

For a counter, I wouldn't want to be on a lander so fragile[0] that being manipulated upright is infeasible. Something will go wrong, maybe not on that lander, but when it does go wrong it'll have to get duct taped together.

[0]Not just mechanically, but in terms of operation scope. Planning that everything must go perfectly or people die is a recipe for the latter.

[toss1]

I deliberately did not say I wanted jacking to be infeasible — but I DO want it quite far down on the options list, as in there's >10 better things to try first.

(And yes, I've done a fair amount of wrangling vehicles, gear, etc. in snow, dirt, mud, & rocks, and eventually it can often be gotten out. But on a different planet/moon, it really should be not be anything close to a primary option. OTOH, if it's got a set of 6+ pop-out lever-legs to upright itself, tested, etc., that's a different solution)

[ghufran_syed]

agree - which is probably why Elon Musk is so obsessive about increasing the efficiency and thrust of the merlin and raptor rocket engines, a huge amount of downstream capability can be achieved by increasing that number (all other things being equal)

[hinkley]

So if the lander falls over because two of the feet land on regolith, odds are good you don't have a solid point on that side of the craft to put the jack...

[ooterness]

If it's good enough for Jebediah Kerman, it's good enough for me, but maybe not NASA.

https://xkcd.com/1244/

[dredmorbius]

The Explain is worth reading for this one: <https://explainxkcd.com/wiki/index.php/1244:_Six_Words>