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Chang'e 6 lunar sample return mission returns with samples from moon's far side

theguardian.com

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Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#81

Post by hifromwork »

pc86 wrote: post #53
porphyra wrote: post #24

Earlier quoted context omitted.

Let's not bring sinophobia and geopolitics into a scientific mission to the moon.

No, but can we bring realism into it? The explorers may be exploring for the sake of it, but the people paying for it definitely aren't. Many - perhaps even most - of the people at NASA would have probably done the job for free if they were able, but the people allocating NASA's budget in the 50s and 60s were doing so for geopolitical reasons first and foremost.

Personally I don't care much who sponsors scientific missions. I wish we would all collectively spent more on science. If China is going to help science, I'm happy to cheer for them.

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#82

Post by floxy »

itishappy wrote: post #42
somenameforme wrote: post #22

Earlier quoted context omitted.

Another, perhaps even more interesting question, is also how the first generation who are born in low g will evolve and adapt. And this, so far as I know, is a completely unexplored question. Mammal experiments might be interesting, but at some point you simply have to do it with humans, not only because of our fairly long gestation period, but also because of how absurdly undeveloped we are even once when born. Ther…

> And this, so far as I know, is a completely unexplored question. To date, no mammals have given birth in space. We sent pregnant mice and had them return to Earth to give birth, and we've sent mouse zygotes and grown them in space, but no birth!

Mice in space:

https://www.youtube.com/watch?v=q7lgj3aZ8dU

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#83

Post by dotnet00 »

standardUser wrote: post #80

Do either China or the US have plans to attempt a Mars sample return? Does China have the rocket power to attempt such a mission? The US seems focused solely on the return moon missions, with any Mars mission presumably behind at least 5 more major Artemis missions that are scheduled through 2031.

China as far I'm aware doesn't have any solid plans on the books yet. NASA has been working on planning out a Mars sample return for a few years now, part of the Perseverance rover's job is to collect samples, store them in canisters, and drop them for future retrieval. This ensures that the samples have a much lower risk of having been contaminated, if, say, they end up being retrieved by a crewed mission.

The issue has been that previous proposals have all been too complex and too expensive, eg, a second rover that has to retrieve the samples and then place them on a lander which has a rocket on-board, the rocket then launches back into orbit, where an orbiter picks up it up and brings it home.

They've recently started soliciting other ideas for a way it might be done from private industry. The most promising in my opinion being to use a Starship, so they would be able to send a large enough return rocket to not need an orbital rendezvous, significantly simplifying things. I doubt they're seriously proposing a crewed Starship sample retrieval just yet. Another neat proposal I've heard is to build on the success of the Ingenuity helicopter to have a bunch of similar helicopters go around picking up the samples instead of a rover.

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#84

Post by contingencies »

dotnet00 wrote: post #52
barelyauser wrote: post #47

Earlier quoted context omitted.

Don't they use radar altimeters to get altitude? You don't need to rely only on image processing. You can even pull off stereo using a single camera since you are moving and know the altitude at every point.

They definitely combine several sensors to get a proper height reading, but as we've seen with the American and Japanese landers, getting good readings from the sensors, properly accounting for all factors that might affect sensor readings and being able to properly handle sensor disagreements is quite challenging.

Better call my man... Kalman.

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

For distance during landing I would be thinking a spatially maximally distributed array of quartz-shielded, thermally-supported laser TOF sensors along nominal extremities, but that's just because they're familiar to me, small, power-efficient, highly linear, relatively accurate, and cheap. Unsure if the IC physics assumptions work in non-atmospheric conditions. Perhaps the output can be re-scaled to obtain cheap and accurate enough readings.

A non-dilettante with an actual physics degree would clearly be desirable ;)

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#85

Post by standardUser »

dotnet00 wrote: post #83
standardUser wrote: post #80

Do either China or the US have plans to attempt a Mars sample return? Does China have the rocket power to attempt such a mission? The US seems focused solely on the return moon missions, with any Mars mission presumably behind at least 5 more major Artemis missions that are scheduled through 2031.

China as far I'm aware doesn't have any solid plans on the books yet. NASA has been working on planning out a Mars sample return for a few years now, part of the Perseverance rover's job is to collect samples, store them in canisters, and drop them for future retrieval. This ensures that the samples have a much lower risk of having been contaminated, if, say, they end up being retrieved by a crewed mission. The issue…

Excellent info, thank you. If you or anyone else have favorite news sources for keeping up on space programs, please share. I tend to get most of my space news from HN.

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#86

Post by dotnet00 »

contingencies wrote: post #84
dotnet00 wrote: post #52

Earlier quoted context omitted.

They definitely combine several sensors to get a proper height reading, but as we've seen with the American and Japanese landers, getting good readings from the sensors, properly accounting for all factors that might affect sensor readings and being able to properly handle sensor disagreements is quite challenging.

Better call my man... Kalman. https://en.wikipedia.org/wiki/Kalman_filter For distance during landing I would be thinking a spatially maximally distributed array of quartz-shielded, thermally-supported laser TOF sensors along nominal extremities, but that's just because they're familiar to me, small, power-efficient, highly linear, relatively accurate, and cheap. Unsure if the IC physics assumptions work in non-atmos…

A kalman filter wouldn't account for say, the issue that hit the HAKUTO-R lander, where because the reading on the radar altimeter changed too rapidly, the computer assumed it was faulty, or the IM-1 lander, where they initially had a lot of trouble with altitude sensing (in part because they forgot to remove the covers from the laser rangefinders), managed to work around it, and then failed to fully sense and cancel out the lateral velocity, causing it to skid along the surface, snap a leg and tip over.

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#87

Post by contingencies »

dotnet00 wrote: post #86
contingencies wrote: post #84

Earlier quoted context omitted.

Better call my man... Kalman. https://en.wikipedia.org/wiki/Kalman_filter For distance during landing I would be thinking a spatially maximally distributed array of quartz-shielded, thermally-supported laser TOF sensors along nominal extremities, but that's just because they're familiar to me, small, power-efficient, highly linear, relatively accurate, and cheap. Unsure if the IC physics assumptions work in non-atmos…

A kalman filter wouldn't account for say, the issue that hit the HAKUTO-R lander, where because the reading on the radar altimeter changed too rapidly, the computer assumed it was faulty, or the IM-1 lander, where they initially had a lot of trouble with altitude sensing (in part because they forgot to remove the covers from the laser rangefinders), managed to work around it, and then failed to fully sense and cancel…

The first sounds like bad assumption (hard fault limit).

The second sounds like bad process leading to bad input, at which point it becomes garbage in, garbage out. The workaround was untested and insufficient.

While you are of course correct the filter will not fix these, none of these are the fault of the filter, they are all human process issues that are firmly out of scope.

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#88

Post by pavel_lishin »

standardUser wrote: post #80

Do either China or the US have plans to attempt a Mars sample return? Does China have the rocket power to attempt such a mission? The US seems focused solely on the return moon missions, with any Mars mission presumably behind at least 5 more major Artemis missions that are scheduled through 2031.

Yep, the latest NASA lander is dropping samples in containers meant to be picked up by a later mission: https://www.nasa.gov/news-release/nasa-sets-path-to-return-m...

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#89

Post by mturmon »

throwaway199956 wrote: post #10

One thing they seems to have got working fairly reliably is the lunar landing of the probe using image processing to guide the final approach and touch down. It seems to have worked well in this and the previous mission, there are videos on youtube of that. https://youtu.be/wUju9-cckKA?si=nZFOCga10mnCA_vs The other component is the autonomous docking of the return probe in lunar orbit. Soviets have done a lunar sampl…

Here's an article on DIMES, the system JPL developed in the early 2000s to address the problem of estimating horizontal velocity for the Mars landers:

https://robotics.jpl.nasa.gov/media/documents/DIMES-ai-space...

Martian winds make this more important there than on the Moon. The DIMES system integrates radar, visual images, and IMUs. They did not have a dedicated Doppler radar for horizontal velocity, for technical and cost reasons it was not workable.

From the introduction:

> Some of the challenges were subtler — and one in particular was subtle enough that it wasn’t fully appreciated until mission development was well underway.

> This was the challenge of martian winds. How to detect and compensate for them? In the worst-case scenario, they could tip the vehicle over in the final stages of descent such that the powered thrust intended to eliminate downward velocity might actually drive the platform sideways and down into the surface beyond the safety envelope of the airbag cushions.

> This article tells the story of how this late-understood challenge was addressed successfully — and, as it turned out, critically, for Spirit.

The system was improved and re-fielded for the successor missions - I think it goes under the name LVS now. One reference appears to be here: https://www-robotics.jpl.nasa.gov/what-we-do/applications/la...

Re: Chang'e 6 lunar sample return mission returns with samples from moon's far side

#90

Post by DaoVeles »

dotnet00 wrote: post #83
standardUser wrote: post #80

Do either China or the US have plans to attempt a Mars sample return? Does China have the rocket power to attempt such a mission? The US seems focused solely on the return moon missions, with any Mars mission presumably behind at least 5 more major Artemis missions that are scheduled through 2031.

China as far I'm aware doesn't have any solid plans on the books yet. NASA has been working on planning out a Mars sample return for a few years now, part of the Perseverance rover's job is to collect samples, store them in canisters, and drop them for future retrieval. This ensures that the samples have a much lower risk of having been contaminated, if, say, they end up being retrieved by a crewed mission. The issue…

It is such a classic issue with space travel. One way trip is relatively easy, return trips are WAY more difficult because of the reasons listed.

China has a plan to get an orbiting probe to Neptune but nothing about returning Mars samples. Highlights the different scale of the problem.

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