241–250 of 277 posts
Is there any reason why we couldn't have some rudimentary GPS-like satellites around the moon? That could help out these kinds of landers, no?
Who do you propose should fund lunar GPS for the benefit of private companies who want to land on the moon?
But “who should fund this?” is a separate question from “would this help?”.
I don’t think it would really help that much, and that is the reason why the private companies are not doing it.
Welp, I worked on this one. Specifically, I worked on the laser rangefinders which are under so much scrutiny. I no longer work at Intuitive Machines, but I'm certainly interested in finding out what happened to the lasers this time.
But in case you can: Was a radar based altimeter considered?
How do you guys deal with kicked up regolith? (I have seen first hand how hard heavy snow is on lidars, and would imagine that regolith “shower” is similar, but what do I know.)
If you take the time to study the documentation from the 1950s & 1960s, the engineering culture of that era appears to be markedly different from the engineering culture prevalent today. And I think it's deeply rooted in the symbiotic relationship between computing, Baumol's cost disease and our obsession with precision, results-oriented, MBA-style-min-maxing, "good enough for government work" engineering. Robert Tru…
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> that is still peanuts comparted to the moon's surface Sure. I'm not trivialising the problem in an absolute sense. Just going from floating barge or chopsticks to Moon is a simpler set of problems than reïnventing the sort of translational velocity and attitude control needed to get to first base.
You say this based on your history of landing rockets on the moon? And on your history of dealing with the lunar regolith near the poles?
Actually, mini propulsive landers in lunar regolith stimulant. Yes. In atmosphere and with Earth gravity, both of which make it more annoying and more difficult.
Why people make temperature in space a big deal? It's mostly vacuum and has no heat capacity. Sun radiation is the real threat, but the concept of temperature can't even be applied to vacuum.
The space surrounding you may not have a temperature but your spacecraft does, and it will lose heat via radiation, batteries and electronics will stop working after your temperature reaches a certain low.
Designing for a wide range of temperatures in space where shedding heat is a challenge and running heaters (during dark/cold periods) is necessary, and where at the best of times re-deploying radiators and heat shields is difficult, let alone when the craft is lying on its side.
So ambient temperature matters. As another comment notes, in most cases, the problem is excess heat and the shedding of it. Particularly for Earth-orbiting satellites, which are subject to 1kW/m² solar radiation and are in shadow for only a small portion of their orbit (less with higher altitudes).
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Any moderately active satellite has far more issues with excess heat
It depends on the size of the satellite and its power use. Small spacecraft often don't use enough power to generate enough heat to warm themselves. The problem then is batteries get cold (which is one of the places you need heaters) and become inefficient and then you end up in death spiral. Here the probe likely wasn't generating enough power anyway, so that would almost certainly kill it before the cold.
Is there any reason why we couldn't have some rudimentary GPS-like satellites around the moon? That could help out these kinds of landers, no?
High lunar orbits is unstable because of Earth influence (i. e. long-term orbiting requires lots of fuel for extensive orbit maintenance). Most low orbits are unstable as well because of uneven mass distribution, but there are some exceptions: https://en.wikipedia.org/wiki/Frozen_orbit Low orbits would also require either more satellites for complete coverage or synchronizing launch window, which is PITA enough as it…
Earlier quoted context omitted.
High lunar orbits is unstable because of Earth influence (i. e. long-term orbiting requires lots of fuel for extensive orbit maintenance). Most low orbits are unstable as well because of uneven mass distribution, but there are some exceptions: https://en.wikipedia.org/wiki/Frozen_orbit Low orbits would also require either more satellites for complete coverage or synchronizing launch window, which is PITA enough as it…
But would they need to be in the orbit? Since nothing is on the moon, couldn't you just create a GPS array on the ground?
Earlier quoted context omitted.
High lunar orbits is unstable because of Earth influence (i. e. long-term orbiting requires lots of fuel for extensive orbit maintenance). Most low orbits are unstable as well because of uneven mass distribution, but there are some exceptions: https://en.wikipedia.org/wiki/Frozen_orbit Low orbits would also require either more satellites for complete coverage or synchronizing launch window, which is PITA enough as it…
But would they need to be in the orbit? Since nothing is on the moon, couldn't you just create a GPS array on the ground?
It's not exactly nothing, the moon itself with its mountains is there and blocking the radio signal and it means propagation isn't unlike that of VHF/UHF on Earth. You still only have no visibility beyond the horizon. In order for it to be visible and useful during landing you would need the base station to be reasonably close. I guess that would make it more akin to ILS/VOR/DME than GPS. That obviously wouldn't be feasible until we have a permanent base there (perhaps an unmanned one).
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For any of these landings, it's a problem of 3d positional/velocity precision . SpaceX has prove that they can reliably land on a target, usually within meters, with negligibly delta velocity on contact. In other words, they've proven they have the control systems in place for placing a craft at a precise location, with a precise velocity. What requirement do you see outside of this that are far outside of placement…
> 3d positional/velocity precision. SpaceX has prove that they can reliably land on a target, usually within meters On Earth, which has GPS. On a very highly engineered landing surface. Landing on inertial guidance on soft regolith is a whole different ballgame.
Which is not the future. Optical/lidar/positioning radio is the future, to make it closed loop (NASA’s Laser Retroreflector Array for high, lidar/optical for low altitudes).
> On a very highly engineered landing surface.
As I mentioned, we shouldn't assume the earthy landing legs are used. That would be a very silly assumption.
From what I can extract from your comment, you believe that the positioning system and landing legs are the issue, rather than the control systems. I suspect both are somewhat related: positioning system to place it over predictable regolith with some, yet-undeveloped, landing legs that need to work at 1/6th gravity.
I'm of the opinion that it's possible/solvable, as is NASA. It would be helpful if you would answer why you think it's not possible: what requirement do you see that make positioning and landing on regolith unachievable for SpaceX?
[1] https://www.nasa.gov/centers-and-facilities/langley/nasas-la...