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Comment by joeevans1000 | Hacker News Reader

Not being critical here, just a question from my curious naivety (lunar exploration is hard): these landers seem spindly and unforgiving, landing-wise. Are there bouncy ball type craft that could be made, or something that can reorient or push itself up after landing? I have a vague memory of something like that being used on Mars.

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Yep, most of the previous Mars rover prior to Curiosity did it this way. They had a number of balloons surrounding the rover and landed and bounced along the surface. Then the balloons were deflated in a particular order so the rover ended up the right way up. But for these there was some atmosphere to slow the descent with a parachute and balloons. But for landing on the moon you need the thrusters to slow you down for landing so it can't just be balloons on either side. Presumably you could still use something to slow you down that isn't part of the science mission for the lander that gets ejected right before landing an then let the balloons hit the surface and drop down. But now there are multiple mechanisms and things to do the landing which means more money.

https://www.youtube.com/watch?v=kSbAUtyO7xo

On the moon, you would eventually slow down after bouncing because of the energy loss from the not very elastic balloons. But it might take a while and you might bounce into a crater or something.

The first soft landing on the moon in January 1966 by Luna 9 was like that: https://www.russianspaceweb.com/luna9.html (has a picture of the landing profile)

With the landing probe encased in airbags ejecting from the main body a couple meter above ground. The probe the rolled for a bit, once it stopped it then opened up and started doing science.

There are indeed craft like that. The NASA Pathfinder probe and MER rovers (all to Mars) are probably what you're thinking of.

Ah, cool. I'll look those up. I just looked at the Athena and I'm tempted to armchair quarterback a tiny bit. I mean, that thing looks extremely top heavy. And it had hundreds of millions of dollars of equipment on it. I also wonder if these companies are patenting their approaches so that other companies can't use working solutions.

Size is important. For thin atmosphere or vacuum planet, airbag approach is optimal for small size lander, but for big size space crane is optimal.

Unfortunately, at the moment I could not suggest what is small and what is big for Moon.

And for about IM, things could be even worse, as they are limited as commercial company (NASA lander could use government money to achieve much higher budget and have much more possibilities to do same thing).

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