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Comment by Zondartul | Hacker News Reader

Some Moon ideas: 1) have a small robot bulldozer flatten a landing pad/polygon so there is loads of safe landing area. 2) use same dozer to make a moon highway to other sites of interest around the moon. 3) Moon GPS or laser-based local navigation beacons, so the spacecraft can rely on those if instruments fail. 4) Just stupid-wide landing legs that let the craft ski around the moon even when landing at an angle and with horizontal velocity.

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I had an interesting experience a few years back as a reviewer for proposals to NASA LuSTR program: https://www.nasa.gov/directorates/stmd/space-tech-research-g...

The topic was exactly that: landing pad preparation solutions. Here's a summary slide for one of the winning proposals: https://www.nasa.gov/wp-content/uploads/2022/03/lustr2021_qu...

The Autonomous Site Preparation: Excavation, Compaction, and Testing (ASPECT) Project will develop tools and methods to clear, level, and compact the lunar surface. ASPECT is a fully autonomous rover with equipment for regolith excavation, boulder moving, and surface compaction.

There are a number of well fleshed out plans for doing essentially this. One of the more interesting ones for me was that microwaves can be used to fuse lunar regolith into a solid. One plan had a solar powered rover that sat there and microwaved the ground until is was solid far enough down, then would move forward on to that patch and start with the next patch. As I recall it would take about a month to make an acre sized "pad" which would support landing.

The reason Odysseus's legs are so narrow is that they wanted fixed legs, so there's no leg deployment that could go wrong. But payload fairings are only so wide. The legs are the widest that fit a Falcon 9 payload fairing.

I really like the idea of a mission to build infrastructure though.

Building infrastructure is the only way this stuff will get cheaper and easier

Just like Canadarm ([1]) on ISS considerably simplified docking, I can see a similar approach working for lunar landing: slow down to below 5 m/s, get caught by a robotic arm and gently put into a good spot.

1. https://en.wikipedia.org/wiki/Canadarm

https://en.wikipedia.org/wiki/Catcher_pouch

Its called birthing if you use the Canadarm. And there is a reason every modern ship doesn't use that approach.

> Its called birthing

But mostly by obstetricians and context-unaware autocorrect software?

https://dictionary.cambridge.org/dictionary/english/birthing

https://dictionary.cambridge.org/dictionary/english/berthing

No just by me and the dyslexia gang.

Building infrastructure doesn't make sense for exploratory missions that each want to land somewhere new though.

You know how the martian landers now use a crane to lower the lander to the ground so the retro rockets are outside of the ground effects range?

Someone proposed doing something similar with a lander, where a landing-site-prep robot gets dropped first. But that sounded like a lot of hovering to me, and a solution that would be very specific to lunar landing. I can't see that being successful on anything with higher gravity.

Better perhaps to send a separate stage or a scouting mission to do the work, then land later.

You know, we're probably capable of landing on a landing pad on the moon, now.

Apollo 11/Eagle landed something like 4 miles off from their target site, but SpaceX nowadays routinely lands on target.

A launch and return to the same rotating body is surely a simpler maneuver than orbital transfer to a different spinning body and landing. No doubt we are better at it but I’m not sure earth landings are an accurate analog.

Nah, you can't really compare them like that. And landing on a planet with an atmosphere is completely different from a moon without one.

Landing on the moon is easier. It just looks hard because it's so expensive to get there that you don't get many attempts.

That depends on how much atmosphere. Mars has enough atmosphere to be annoying, but not really enough to be useful. Winds can throw you off target, but you can't use a parachute for a soft landing.

That's not true. Many (most?) Mars missions with Landers have used parachutes, though they are not sufficient for a true soft landing.

I'm not an expert but I think landing on Mars with no atmosphere would be harder, because you'd need so much more fuel for a controlled descent.

Apollo 11/Eagle was deliberately piloted away from the initial landing site because the pilot did not think the original location was safe. So until a perfectly placed target for a robot to land on like SpaceX does (which seems only likely if establishing a sort of base), the robots will need to be made smarter about landing or built to be more agile on landing on less than ideal sites.

> SpaceX nowadays routinely lands on target

On the moon?

No SpaceX-made craft has landed on the moon.

The article mentions that SpaceX has landed on the moon once, and tipped over. The moon is harder to land on then the Earth - less gravity and atmosphere.

I haven’t read the article (paywall) so I can’t be sure, but I believe the article is referring to the Intuitive Machines lunar landing.

SpaceX has not yet attempted to land anything on the moon.

SpaceX launched Odysseus. If you want to argue that this doesn't count as SpaceX landing, that's fine, but then it's even less evidence of Spacex's ability to land anything on the moon standing up.

Apollo 11 isn't really the proper comparison to make, though; more precise landings were goals of later missions.

Fair enough; Apollo 12 landed within walking distance of the Surveyor probe, but I don't have enough information to know whether 535 feet from the probe was exactly on target, or hundreds of feet off target. So maybe we could have landed on a pad 50 years ago, too?

Probably, but do we want to keep going back to the same spot?

... and then Apollo 12 targeted one of the earlier Surveyor probes (which had successfully done its own automated moon landing in the mid-1960s!), and the guidance system had it coming down very close to the earlier probe -- astronaut Pete Conrad manually overrode it to make sure they stayed a safe distance away.

There had been upgrades to software and procedures since Apollo 11 -- most notably, a new guidance parameter the astronauts could enter ("noun 69") to correct for deviations between the planned lunar orbit and the one in which the spacecraft actually was, before descent.

https://www.forbes.com/sites/davidmindell/2019/11/19/apollo-...

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