[HN Gopher] Chang'e 6 lunar sample return mission returns with s...
___________________________________________________________________
Chang'e 6 lunar sample return mission returns with samples from
moon's far side
Author : throwaway199956
Score : 141 points
Date : 2024-06-25 15:48 UTC (7 hours ago)
(HTM) web link (www.theguardian.com)
(TXT) w3m dump (www.theguardian.com)
| ck2 wrote:
| The international moon base plan is fascinating.
|
| https://en.wikipedia.org/wiki/International_Lunar_Research_S...
|
| (nuclear power plans by Russia not so much)
|
| Is there enough gravity on the moon to prevent the long-term
| health problems from the space station like bone, muscle and
| vision loss?
| JumpCrisscross wrote:
| > _nuclear power plans by Russia not so much_
|
| Why? Any lunar base without nuclear power plans is not a
| serious effort.
| consumer451 wrote:
| I often wondered, how do you deal with all the waste heat
| from a fission power reactor, in a vacuum?
|
| Giant radiators?
|
| edit: fixed typo, derp. fusion=fission
| creer wrote:
| Perhaps? Any reason that sounds silly to you?
| consumer451 wrote:
| No, and this is not some attack on nuclear power. I am
| just curious. On earth, nuclear power plants use lots of
| water and cooling towers. How does that work in a place
| with no spare water?
|
| I also meant to write fission in my original question,
| not fusion.
| creer wrote:
| Mostly cooling towers are not likely to work in a place
| with no atmosphere.
|
| Radiators though, are constantly used in spacecraft, and
| seem to work well. Low gravity, no motion might let the
| thing be mostly the radiator, with not much support
| structure. Except it might need to be in shade, in the
| shadow of a building? hill? solar panels?
| squarefoot wrote:
| > How does that work in a place with no spare water?
|
| I wonder if recycling human liquid waste through
| evaporation could be of some use for that purpose.
| rplnt wrote:
| It would likely be a thermal reactor, I guess? So no waste
| heat, since the little heat it gives is used to generate
| electricity.
| eternauta3k wrote:
| Thermal power plants don't use up the heat. They make
| energy through its transfer (like a dam with water).
| ianburrell wrote:
| Most nuclear reactors are thermal power plants and they
| all need to dump waste heat. Thermal power plants convert
| heat into electricity with turbines and are limited by
| dumping the waste heat.
|
| Are you thinking of radioisotope generators? Those aren't
| reactors. They use thermocouples and need to get rid of
| the waste heat. The Voyager RTGs have radiator fins.
| JumpCrisscross wrote:
| > _Giant radiators?_
|
| Yup, that's the thing on top [1].
|
| [1] https://www.nasa.gov/tdm/fission-surface-power/
| consumer451 wrote:
| Thanks, I have seen a lot of pages on nasa.gov, but not
| that one. Neato!
| bongodongobob wrote:
| Heat is what you use to make steam and drive the turbines
| with. I don't understand your question.
| dotnet00 wrote:
| On the Moon you could also use the Moon itself as a heat
| sink. But yeah, any near-term solutions would use giant
| radiators.
| gus_massa wrote:
| Solids don't conduct too much heat. I think most of the
| cooling in a nuclear plant is generated by evaporation of
| water.
| dotnet00 wrote:
| Yes, what I mean is that theoretically you could do
| something like have a very very wide base to passively
| dump heat into the ground (since we're still only looking
| at kW scale reactors in space), or actively cycle large
| amounts of regolith through the cooling loop (say, via a
| heat exchanger from a closed water loop) and dump it out.
| Depending on how much heat the system can handle, you
| could maybe even extract stuff boiling off from the
| regolith.
| mcculley wrote:
| The nuclear plant nearest to me uses sea water, which is
| put back into the ocean.
| photochemsyn wrote:
| Solar PV linked to battery storage is the obvious energy
| source for a moonbase. All reactors require coolant
| circulation and water is going to be among the most valuable
| commodities on the moon, not something you want to circulate
| through a reactor (where you inevitably get tritium
| formation, making the water unsuitable for other uses).
|
| Maybe you could use helium or liquid sodium metal as the
| primary coolant, but then you still need to generate
| electricty via secondary water coolant loop that runs a
| steam-powered turbine. Really not plausible on the moon.
| porphyra wrote:
| You'll need an insane amount of battery storage, since the
| moon only rotates once per month and you'll need to power
| through a long period of no sunlight.
| Lord-Jobo wrote:
| Or just very long power lines and multiple solar
| stations, it's not like the moon is impossible large. But
| that would be harder than a singular location using
| nuclear fuel, it's true.
| dotnet00 wrote:
| Or alternatively, for polar bases, very tall panels,
| which would be able to be in permanent sunlight.
| JumpCrisscross wrote:
| > _very tall panels, which would be able to be in
| permanent sunlight_
|
| Or normal panels on the rim of Shackleton [1]. (You'd
| still want to bootstrap with fission.)
|
| [1] https://en.wikipedia.org/wiki/Shackleton_(crater)#Pot
| ential_...
| JumpCrisscross wrote:
| > _Solar PV linked to battery storage is the obvious energy
| source for a moonbase_
|
| It's not serious with chemical propulsion and the Moon's
| day/night cycle. Put another way, if one team uses nukes
| and is, as a result, power unconstrained, while the other
| spends all its energy launching solar panels and batteries
| to keep life support online, it's obvious who's going to be
| doing any science.
|
| > _All reactors require coolant circulation and water is
| going to be among the most valuable commodities on the
| moon_
|
| Sodium and sterling, no water [1]. There is a reason even
| NASA is only seriously considering nuclear power [2].
|
| [1] https://www.nasa.gov/directorates/stmd/tech-demo-
| missions-pr...
|
| [2] https://www.nasa.gov/tdm/fission-surface-power/
| somenameforme wrote:
| The moon is fairly unique (relative to Earth) in that the
| exact same spot will go from -200C to +100C on a two week
| cycle (day and night). It seems "obvious" that there must be
| some clever way to exploit this to generate energy in a
| simple and novel fashion.
| JumpCrisscross wrote:
| > _seems "obvious" that there must be some clever way to
| exploit this to generate energy in a simple and novel
| fashion_
|
| Sure, once you have two-week power-storage infrastructure.
| (And the scale to harvest a useful amount of energy once a
| month on average.) In the meantime, _i.e._ our lifetimes,
| you have countries that can build space nuclear reactors
| and countries being performative.
| itishappy wrote:
| Good news! Thermal cycles are caused by the sun, and we can
| harvest sunlight directly! Storage is an issue...
| pie420 wrote:
| Storage is not an issue. It's been solved for decades. In
| fact, energy storage is amazing and cheap now, thanks to
| smartphones and EVs. You can buy consumer level batteries
| for very very cheap.
| itishappy wrote:
| Battery tech is awesome, but I think you're overselling
| it a bit. We've barely started figuring out grid-scale
| battery storage _on Earth_. There 's 2 big reasons the
| Moon is going to be much much harder:
|
| 1. Batteries are heavy, and space ain't cheap. Current
| launch pricing is about $1.5k/kg to LEO. The Moon will be
| more, it's further away. Even if Starship brings that
| down by a factor of 10, transportations costs are still
| going to be astronomical.
|
| 2. The day-night cycle on the Moon is slow. Your
| batteries are going to need to be able to store half a
| month worth of power. You'll need 15x more batteries on
| the Moon than you would on Earth.
| jandrese wrote:
| I have always assumed that the first moon colony would be
| on the north or south pole to avoid this issue. Not too
| hard to imagine a solar array set up to track the sun with
| a very slow rotation. The colony itself would be in a
| crater to avoid direct sunlight and provide a place to dump
| the heat from the solar array.
|
| Otherwise the need to bring enormous power storage to
| handle the half month of darkness and bitter cold makes
| solar a bit impractical and the only other reasonable
| alternative is nuclear power.
|
| The big problem with attempting to exploit the temperature
| differential is that it happens on such a slow cycle that
| the total amount of energy available is quite low.
| BurningFrog wrote:
| Could you exploit the temperature differentials between
| the either hot or cold surface, and the presumably in-
| between temperature at the bottom of a drill hole?
| jandrese wrote:
| In theory the temperature underground should be the
| average of the surface temperature, so you could use that
| gradient to generate energy at night. Someone smarter
| than me would have to do the math on the energy density
| of a scheme like this, my gut says it's going to be
| fairly low and you will need a really big power plant to
| supply even a modest colony.
| krisoft wrote:
| > Is there enough gravity on the moon to prevent the long-term
| health problems from the space station like bone, muscle and
| vision loss?
|
| Nobody knows. You might think scientist can science up answers
| to any question but it is impossible to know this without long
| term data which is simply not available.
|
| There were some experiments done in parabolic flights [2] but
| those only last for a very short time.
|
| There is this literature review [2]. They are not optimistic:
| "It can be anticipated that partial gravity environments as
| present on the Moon or on Mars are not sufficient to preserve
| all physiological systems to a 1 g standard if not addressed
| through adequate countermeasures." Which is space speak for
| "you will need to go to the gym on the moon". But they are
| willing to admit how little there is to know for certain: "The
| methodological quality of the vast majority of the
| available/included studies is too low to generate a compeling
| evidence."
|
| 1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10411353/
|
| 2:
| https://www.frontiersin.org/journals/physiology/articles/10....
| somenameforme wrote:
| 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.
| There's every reason to think a human baby may develop
| differently than other mammals which do far more development
| within the womb.
| itishappy wrote:
| > 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!
| floxy wrote:
| Mice in space:
|
| https://www.youtube.com/watch?v=q7lgj3aZ8dU
| JumpCrisscross wrote:
| > _it is impossible to know this without long term data which
| is simply not available_
|
| Generating these data is one of the biggest pay-offs of a
| lunar colony.
| pc86 wrote:
| I know data is the plural of datum but seeing "these data"
| instead of "the data" is always so jarring to me. Almost as
| jarring as seeming anyone use the word "datum" ever.
|
| Is this one of those generational things like "on accident"
| vs. "by accident" or regional things like "math" vs.
| "maths"?
| vlovich123 wrote:
| > The word data can be either singular or plural
| depending on meaning and context. In general usage, data
| is treated as singular when used as a mass noun to mean
| "information" and as plural when used to mean "individual
| facts." In scientific and academic writing, data is
| almost always used as a plural noun. In digital
| technology, data is usually treated as a singular mass
| noun to mean "digitally stored information."
|
| While it's used interchangeably a lot, it's also based on
| whether you have a scientific or CS background. My hunch
| is that the scientific plural usage will eventually
| largely die out except in very specific situations after
| a few generations given that software is eating the
| world.
|
| [1] https://www.thesaurus.com/e/grammar/data-is-or-data-
| are/
| JumpCrisscross wrote:
| Huh, didn't know about that line. I do tend to refer to
| scientific data plurally, where each datum is
| meaningless, and technical data singularly.
| dctoedt wrote:
| > _Is this one of those generational things like "on
| accident" vs. "by accident"_
|
| "On accident": Abomination! Kill it with fire, now!
| </OldFartRant>
| pelagicAustral wrote:
| I do not know for a fact, but I wouldn't think there is a
| single chance in hell that living in an environment with 1/6th
| of the gravity we've got on earth would not cause long term
| effects in your health, specially to the bones and muscle.
| lawlessone wrote:
| Probably fine .. as long as you don't come home.
| uneoneuno wrote:
| Also changes eye shape over time, causing vision issues,
| etc.. Longer you're up there the more starts to go wrong.
| We were built to fight off gravity. I think its worth
| considering that it may be fundamentally impossible for
| humans to reproduce/gestate babies/live entire
| lifetimes/generations in low gravity conditions.
| ta1243 wrote:
| Well there's a world of difference between micro-gravity
| (where there have been problems with nice) and low
| gravity like on the moon (where there's been no
| experiments)
|
| If you did have viable babies in low (not zero) gravity
| situations though, would you in fact be starting a new
| species.
| gus_massa wrote:
| It's not clear when a new specie is different from the
| previous one, but you probably need:
|
| * Like 100.000 years, probably more. (From the split of
| us from chimps 5.000.000 I counted like 30 species in
| https://en.wikipedia.org/wiki/Human_evolution , but the
| number depends a lot on who count them.)
|
| * Isolate the populations so they can't interbreed (first
| because they can't meet and later becuse the dna is
| incompatible)
| scoot wrote:
| What are they expecting to be different about samples from the
| moon's far side to those previously collected?
| somenameforme wrote:
| The reason you seek to explore what you don't know is because
| you don't know what you don't know.
|
| In general I don't think people really appreciate how
| ridiculously little we know about everything outside of our
| planet. Like for instance it was only in 2013 (!!!) that it was
| discovered that Mars' soil is relatively 'moist', about 2%
| water by mass. And that's just the topsoil layer - it's
| suggestive that below the surface it could well be even more
| moist.
|
| But the Moon's much closer, so we must know more, right? Well
| water ice on the Moon was only confirmed in 2018!! [1] So
| actually starting to get surface samples, and explore more of
| the Moon, ideally with a rapid return to humans on it is so
| exciting because who knows what we'll find out next? The
| unknown is precisely what makes exploring the unknown so
| enticing, rewarding, and fun!
|
| [1] - https://www.space.com/41554-water-ice-moon-surface-
| confirmed...
| vasco wrote:
| > Well water ice on the Moon was only confirmed in 2018
|
| Thats for surface water, we confirmed a while longer the moon
| has water underground.
| tshaddox wrote:
| No idea what they're expecting, but I would expect some
| interesting differences based on our current understanding of
| the geological differences between the two sides. Apparently
| the near side was warmed by Earth early in the Moon's history
| which meant the far side cooled more quickly and developed a
| thicker crust.
| tivert wrote:
| > What are they expecting to be different about samples from
| the moon's far side to those previously collected?
|
| Different bragging rights.
| burnished wrote:
| They hope to test their hypothesis that volcanoes on that side
| became inactive 4 billion years ago. Great question frankly,
| this article goes into it in much more detail (I just selected
| a likely looking blurb, there are other elements of the theory)
|
| https://www.cnsa.gov.cn/english/n6465652/n6465653/c10523137/...
| kkylin wrote:
| Leaving aside all the geopolitics and bragging rights, I would
| imagine that one scientifc reason for trying is that since the
| far side gets more meteor hits, there may be more material from
| elsewhere in the solar system. (Having said that I know nothing
| about this mission and am just guessing.)
| HenryBemis wrote:
| I mentioned Gold on my comment before I read yours. Yes that
| makes perfect sense. Why ruin your reputation (hehe) with
| children mining rare metals, when you can have known and
| unknown rare metals flown in..
|
| It is costly though to bring in a ton of <insert element>
| from the moon.
| HenryBemis wrote:
| I was thinking about "what have they found there?". I remember
| reading that the Central Bank of China was feversly buying
| Gold, and a few weeks ago they stopped all buying. Then this
| came to focus, and it made me think... did they find 100 tons
| of Gold up there, and they know that if they start bringing
| this in (on Earth) they price will plummet, and expect a
| massive sell-off in the next few weeks???
|
| But then I _do_ read and watch too much sci-fi!!
| bluish29 wrote:
| I think it is very expensive way to acquire 100t of gold. It
| is cheaper to just buy or mine them from our planet.
| burnished wrote:
| No, absolutely not. I can't say future space mining isn't a
| consideration (a moonshot if you will) but the challenges are
| astronomical. First you have to setup a mining and refining
| operation in an incredibly hostile environment and then you
| need to ship it back. We just aren't there yet.
| psadri wrote:
| It would be a good sci-fi plot to find a moon base hiding back
| there. Populated by aliens/your current enemy/tech billionaire
| mad scientist/high IQ octopi
|
| It could also be an abandoned base.
| burnished wrote:
| Or your ancestors
| sinxccc wrote:
| you won't expect rock samples from New England and middle east
| are the same, right? The current theory is that samples
| collected by Chang'e 6 could be the oldest sample we ever saw
| from Moon. It would be worth to study and prove that.
| joshuahedlund wrote:
| In the book _Super Volcanoes_ , I read about how complex the
| moon is geologically and how little of it we've examined and
| how poor our understanding of the geological history is.
| Apparently we can't yet explain how it was geologically active
| so recently. Imagine if the only rock samples we had from Earth
| were from a couple random spots on the surface, from wildly
| different time periods, and trying to develop together a theory
| of how its geology changed over time from that.
| Symmetry wrote:
| I wonder if not being shielded by the Earth's magnetic field
| during full day would lead to a different balance of isotopes
| deposited by the solar wind.
| throwaway199956 wrote:
| 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 sample return, but they had a probe
| that would lift off directly into a earth return trajectory, but
| that seems to have limited both the liftoff mass and the possible
| zones in moon from which it can lift off. This seems a much more
| complex mission than that.
|
| Also some animated videos of the misson show a skip re-entry back
| to earth, don't know if it is the case during this particular
| flight.
| JumpCrisscross wrote:
| > _the lunar landing of the probe using image processing to
| guide the final approach_
|
| Anyone building precision weapons has gotten fairly good at
| this.
| dotnet00 wrote:
| Weapons guidance systems get to be simpler in many ways.
|
| If you've seen some of the Lunar or Martian landing videos,
| you'll notice that it's very hard to tell the scale.
| Especially on the Moon, the lack of atmosphere to disturb the
| surface makes it fractal-like, which probably really messes
| with the CV algorithm. It'd work fine when high up, but as
| you approach for landing, it would probably struggle,
| especially for, say, estimating how far away the surface is.
| barelyauser wrote:
| 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.
| dotnet00 wrote:
| 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.
| contingencies wrote:
| 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 ;)
| dotnet00 wrote:
| 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.
| contingencies wrote:
| 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.
| sudosysgen wrote:
| It is a lot more difficult in space, since you don't have the
| atmosphere to steer for free and because fuel margins get
| very expensive. Being familiar with these image processing
| systems, I could see it being a significant challenge.
| mturmon wrote:
| 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...
| omneity wrote:
| I sincerely hope there's no moonseed in it.
|
| https://en.wikipedia.org/wiki/Moonseed_(novel)
| jiehong wrote:
| They only linked to other articles of the guardians but not to
| the official announcement.
|
| Official announcement by the CNSA:
| https://www.cnsa.gov.cn/n6758823/n6758838/c10565180/content....
|
| Congratulations for such an achievement!
| standardUser wrote:
| 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.
| dotnet00 wrote:
| 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.
| standardUser wrote:
| 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.
| pavel_lishin wrote:
| 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...
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