[HN Gopher] The quest to build a telescope on the moon
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The quest to build a telescope on the moon
Author : pseudolus
Score : 113 points
Date : 2024-09-24 10:30 UTC (12 hours ago)
(HTM) web link (www.newyorker.com)
(TXT) w3m dump (www.newyorker.com)
| pseudolus wrote:
| http://archive.today/U7ZfW
| postalcoder wrote:
| articles like this make me wish I could be reading it on a
| magazine
| admissionsguy wrote:
| In 2022, I bought a yearly subscription of the paper version of
| Scientific American in an attempt to recreate the childhood
| feeling of reading it. I am glad I did but I only received six
| out of 12 issues, in two packets of three. Plus it has become
| highly political, so I won't be doing it again.
| s0ss wrote:
| That's available! I miss the tactile experience myself.
| Hmmmm...
| jmclnx wrote:
| That would be great if that can happen, plus I hope the can build
| a Radio Telescope on the Moon with it.
|
| That should avoid all the Radio Interference that plagues Earth
| Based Radio Telescopes.
| zabzonk wrote:
| until the moonbases need moon-orbiting comms satellites?
| avmich wrote:
| True. The reason could be that the Earth interference is
| worse and less controllable.
| ceejayoz wrote:
| With no atmosphere, laser links might be better; like
| Starlink is working on for inter-satellite comms.
| snickerbockers wrote:
| I'm pretty skeptical, as a general rule if something has never
| been done on earth before you're not going to do it in space. Not
| that I think this is impossible, but nobody even has autonomous
| mining and construction abilities on earth, and they're going to
| do that _on the moon_ with an extremely limited ability to
| perform manual maintenance (I 'm sure they have some sort of
| remote manually-operated drone in mind but again, nobody's ever
| even done that on earth and they're going to do it _in space_ ).
|
| TFA also left out that it's not only going to be a PoC for
| autonomous mining and manufacturing, but also autonomous
| refining. When the Toyota corporation built my car they didn't
| start with unrefined steel ore. I don't even know how they're
| going to do that in a vacuum where there's no fires and no
| convection.
| abecedarius wrote:
| Earth seems a much hairier environment. Air means weather,
| water is notoriously corrosive, and random wildlife and
| microorganisms are hair squared. And initially nobody's going
| to care about preserving the wilderness. It is true we mostly
| don't have to worry about meteors and hard radiation, and the
| local temperature range is smaller.
|
| There were some design studies of lunar resources and their
| extraction in the 70s, iirc using solar furnaces. I think I
| read about this in https://space.nss.org/colonies-in-space-by-
| t-a-heppenheimer/ almost that long ago.
|
| The novelty and distance are a challenge but maybe less of one
| than the problems for autonomy on Earth?
| mc32 wrote:
| Probably budgets are different as well. Why automate
| something you can do cheaper with operators? We may be able
| to automate things on earth but at a prohibitive price with
| respect to competitors. On the moon your competitors would
| have the same limitations --ie you'll just have to pay up to
| get it to work.
| mglz wrote:
| > Earth seems a much hairier environment.
|
| Absolutely not. In space you have to dela with things like
| radiation, extreme temperatures, or cold welding of joints.
| Energy supply can be a big issue depending on your
| environment. On the moon you have to deal with extremely
| abrasive dust.
|
| The most critical issue in space is how difficult it is to
| fix things: If you can get a human there, they will be
| constrained by airlocks and space suits. In most cases it
| will be impossible to get anybody there and you need to
| construct 100% reliable or self-repairing machines. This is
| _extremely_ difficult.
| ajuc wrote:
| On Earth you need to compete against other people doing the
| same. So you design on the edge of performance to extract
| the last few percents of efficiency to compete on price
| against all the other people doing the same thing. Which
| means the machines are complicated, use rare materials and
| require a lot of maintenance.
|
| On the Moon you can do the simplest thing that works and if
| it works at 10% efficiency and breaks after 1 year - so be
| it, if it's enough time to get resources to make a new one.
|
| Basically space exploration will have a lot more in common
| with industrial revolution than with overengineered
| spacematerial NASA stuff.
|
| If we have to make the tractors 10x bigger to have the same
| power and output, and to use disposable steel cables
| instead of hydraulics, and to make them disposable after 2
| years instead of lubricating them to last 20 years - that's
| all fine if it means it can work with lunar materials only.
| abecedarius wrote:
| Automation is especially challenged by richly varying or
| adversarial conditions. The moon has much less of both than
| the Earth; i.e. Earth is "hairier". I already agreed that
| the particular conditions include new problems; in fact I
| already listed your first two.
|
| BTW spacesuits could probably be much better for repair
| work; they seem like another area where NASA has stagnated.
| bjelkeman-again wrote:
| The moon has something Earth hasn't and as far as I have
| seen it seems nobody has figured out how to handle it
| yet. Moon dust.
|
| "The tiny, electrostatically charged particles made of
| crushed lunar rock clung to every surface, from
| spacesuits to electronics, and even infiltrated the
| astronauts' lungs. Crews tried using a brush or their
| hands to sweep the sharp, abrasive dust off their
| spacesuits, but neither method proved very effective."
|
| https://www.smithsonianmag.com/smart-news/nasas-moon-
| dust-pr...
| jerjerjer wrote:
| I'm fairly sure it has not been done on earth because labor is
| simply cheaper, not because it's technologically impossible.
| avmich wrote:
| The point here I think is that we should try doing autonomous
| operations on Earth first not because they are cheaper - they
| are not - but because it's cheaper to try them on Earth than
| on the Moon. When we have these tests successful on Earth, we
| can send the systems to the Moon.
|
| But I'm sure this is being done.
| rendall wrote:
| > _But I 'm sure this is being done._
|
| By whom?
| Animats wrote:
| Robotic manipulation in unstructured environments _still_
| doesn 't work well. It's embarrassing. Just picking items
| from bins at human speed or better still doesn't work in
| production. Amazon has spent much effort on this. This is
| what current technology looks like.[1] That's with machine
| learning.
|
| In the early 1980s, some people at Stanford were talking
| about building something on the moon with robots by the year
| 2000. I asked "How soon can you do that in Utah?" They didn't
| like that.
|
| [1] https://www.youtube.com/watch?v=_Ix_nP2D3hQ
| tim333 wrote:
| There's a lot of AI progress now though. Here are some
| deepmind football robots https://youtu.be/ET-MmoeSvXk?t=435
| Animats wrote:
| Robot soccer has been around for years. It's still not
| very good. Here's the current level of performance.[1]
|
| [1] https://www.youtube.com/watch?v=WppNmh6l3DM
| russdill wrote:
| The moon is much more homogeneous. A kilo of regolith is a kilo
| of regolith. You don't need to find ore.
| jiggawatts wrote:
| Which is another way of saying: _There is no ore!_
|
| Extracting pure elements out of undifferentiated regolith
| (dirt) is impractical and uneconomical here in Earth, even
| with abundant water, power, and even with chemicals such as
| carbon and acids. On the Moon you'd have to use a dry process
| in vacuum. What would that even look like!?
|
| Everyone seems to treat this like it's a computer game with
| +1 resources per tile just waiting to be collected by a
| harvester.
|
| Explain in detail how you'd extract anything of industrial
| utility out of undifferentiated dirt, with a smelter light
| enough to launch on rockets for less than the cost of any
| alternative.
| btbuildem wrote:
| It's a WILD assumption that they won't prototype their setup
| "locally" in a most moon-like location they can find, before
| going to the dark side of the moon.
| sandworm101 wrote:
| >> if something has never been done on earth before you're not
| going to do it in space.
|
| Well, with the rate at which we are launching thousands of loud
| satellites, radio astronomy may simply have to move to space.
| Maybe not the moon, but we will need to get the telescopes
| somewhere above the satellite constellations if we want to
| continue doing radio astronomy.
| Animats wrote:
| > When the Toyota corporation built my car they didn't start
| with unrefined steel ore.
|
| Well, actually, they did.[1] Toyota has their own steel mills.
| "Great cars are made with great steel".
|
| [1] https://en.wikipedia.org/wiki/Aichi_Steel
| irunmyownemail wrote:
| I don't know about radio telescopes but it does sound like a good
| platform, no atmosphere, no magnetosphere, etc. Is it just me or
| does this sounds like a more viable goal for the next 20 years,
| than Mars.
| SubiculumCode wrote:
| Why would a moon telescope be desirable over a satellite
| telescope?
| dagw wrote:
| FTA: "Unlike telescopes such as the Hubble and the James Webb,
| which are made from mirrors and lenses, FarView would comprise
| a hundred thousand metal antennas made on-site by autonomous
| robots. It would cover a Baltimore-size swath of the moon."
|
| They want to build a radio telescope, not a simple optical
| telescope.
| SubiculumCode wrote:
| Thanks. Still, this doesn't answer my question about why
| build it on the moon and not in space.
| tekla wrote:
| I think humans currently have a hard time deploying a 20km
| by 20km object in space.
| echelon wrote:
| To be fair, we also have this problem on the moon.
| jessriedel wrote:
| It's easier to deploy in the weightless environment of
| orbit than on the moon with gravity. Consistent with
| this, the largest off-Earth structure ever built (the
| ISS) is in orbit, not on a heavenly body.
| itishappy wrote:
| Sure, but it's even easier to not have to worry about
| deploying at all. The largest structures we've built were
| built in-situ.
| avmich wrote:
| Can't believe you don't see the other reasons why ISS is
| on orbit.
| netcraft wrote:
| the size. An optical telescope is limited by the size of
| the mirror which needs to be one continuous surface (though
| not necessarily smooth for instance the JWT but I digress),
| but a radio telescope doesnt, it can be many individual
| collectors that can be joined together. This enables it to
| be much larger so it can collect more signal, and the radio
| waves are much longer so it needs to be much larger. In an
| extreme example we have used many different radio
| telescopes together with very precise timing to produce the
| images of the black holes at the center of M87 and the
| milky way.
|
| But it requires those different clusters of collectors to
| be stationary - so while you could probably build a swarm
| of satellites, they would have to stay in very precise
| distances from each other over time which would be
| considerably more difficult than planting them on a
| surface.
|
| Also, a big shield like the moon blocking out radio
| interference coming from the earth is desirable.
|
| IANAA, corrections to my understandings welcome
| itishappy wrote:
| I'd flip your comment about optical surfaces: they need
| to be smooth, not continuous, and smoothness is actually
| not required either! The requirement is a consistent
| phase relationship, which allows the signals to add
| together nicely via interference. Rays coming from same
| direction take the same path to the detector and
| interfere constructively, while rays coming from
| different directions tend to cancel.
|
| For optical frequencies, the phase is difficult to
| measure directly, so we instead polish the surfaces down
| to a fraction of the wavelength of light (so that it all
| has the same phase). For radio telescope, the frequency
| is a lot lower, and we actually can measure the phase
| directly, so we can make our sensors crazy shapes and
| adjust it by adding delay. If you can change the
| individual delays (say, via software) you can change how
| they interfere and therefore change the sensitive
| direction for your telescope. This is how phased arrays
| function.
| netcraft wrote:
| sorry, yeah, thats a much better way of saying it and my
| smooth vs continuous was just confusing
| itishappy wrote:
| Your comment was great! I'm not trying to correct you so
| much as adding additional context.
| ambicapter wrote:
| Why is it difficult to measure the phase directly for
| optical wavelength as opposed to radio? Is it purely
| because the shift is smaller?
| itishappy wrote:
| It's really fast. Visible frequencies are in the THz to
| PHz range, while radio frequencies are in the kHz. Modern
| electronics are fast enough to sample the latter but not
| the former.
| varjag wrote:
| Radio frequencies are in KHz to THz range. There is
| equipment already operating in sub-THz bands but not yet
| close to the frequencies of light.
| fatbird wrote:
| _they would have to stay in very precise distances from
| each other over time_
|
| Is this necessary, or do they simply need to precisely
| distinguish their relative position? My understanding of
| the JWT's not-perfectly-smooth lens is that the ability
| to measure (and correct for) its distortions vastly
| simplified the construction, and I naively think the same
| principle could be used in a swarm of satellites.
| HumblyTossed wrote:
| So, wouldn't it still be easier to build a radio
| telescope from orbiting satellites than on the Moon?
| anigbrowl wrote:
| This was already explained very clearly.
|
| _But it requires those different clusters of collectors
| to be stationary - so while you could probably build a
| swarm of satellites, they would have to stay in very
| precise distances from each other over time which would
| be considerably more difficult than planting them on a
| surface._
| HumblyTossed wrote:
| > difficult than planting them on a surface.
|
| Even considering that the "surface" in question is the
| moon?
|
| We know how to make thrusters. We don't know how to mine
| the moon and make a telescope from scratch.
| Teever wrote:
| It sounds like the solution is to attach the satellites
| to some sort of frame that could be assembled in orbit by
| simple robots.
| itishappy wrote:
| Easier to build it where the materials are than try to
| launch a city-sized radio telescope.
| BurningFrog wrote:
| They're planning to _build_ this telescope on the Moon, by
| mining Moon rocks.
|
| In space, there are no rocks to mine, so you're have to
| launch all the material to space, which is wildly
| impractical/expensive.
| avmich wrote:
| I guess local resources are easier to use locally, rather
| than launching to orbit first? You also have a firm base to
| mount the antenna, and the process of mounting could be
| arguably easier.
| jon_richards wrote:
| It's difficult to keep things spaced out properly in
| microgravity without scaffolding. See also
| https://en.m.wikipedia.org/wiki/Project_West_Ford
| tekla wrote:
| I feel that a 20km wide telescope may have a hard time fitting
| in a fairing.
| sorenKaram wrote:
| imagine a roller coaster on the moon...
| sorenKaram wrote:
| A roller coaster could actually be a good way to move things
| around. With lower gravity than earth, and initial thrust could
| take a payload a predetermined distance effectively.
| ck2 wrote:
| It's just so simple and clean though, if we can't do something
| this basic yet so useful, we should just stop all the space stuff
| and go back to bombing each other to death until the planet
| completely melts and floods in 50 years because we're done. Type-
| Zero civilization.
|
| * https://www.nasa.gov/wp-content/uploads/2020/04/niac2020_ban...
|
| * https://www.nasa.gov/general/lunar-crater-radio-telescope-lc...
| HumblyTossed wrote:
| > a small startup called Lunar Resources
|
| Ah yes, the 'ole investor pump and dump. Get a bunch of people
| excited enough to give you millions, make enough to retire and
| then just disappear in a whiff.
| martinclayton wrote:
| There was an interesting Fraser Cain YT vid a couple of weeks
| back:
|
| https://www.youtube.com/watch?v=wcR6gs0Up6k
|
| Interview with Gerard van Belle, director or the Lowell
| Observatory.
|
| The topic was space/lunar optical interferometers. It's easier to
| do this on the Moon than in space, as there's no formation
| flying. He's got a "menu" of projects from a few/small unit
| telescopes right up to lunar manufacturing like this.
| BurningFrog wrote:
| Let's say this works, and they paint a lot of metal lines that
| form workable antennas on the moon surface.
|
| How do you aim that thing at a specific point in the sky?
| CmdrLoskene wrote:
| It's called phased array. Pretty mature tech now.
| jandrese wrote:
| Probably like Arecibo, by moving the collector around in
| relative to the reflector material. To be honest though aiming
| the mirror is way down their list of problems to solve to make
| this work. They basically want to create several brand new
| industries in an inhospitable environment with little to no
| payoff. It is hard to see a path to success in any reasonable
| timeframe.
| Animats wrote:
| The JPL position is that telescopes should be in space, not on
| Luna. Too much dust. Too much gravity. A lunar farside optical
| telescope was proposed, but it would be inferior to one in open
| space.
| yinser wrote:
| You didn't read the article, it _specifically_ mentions JPL's
| proposal for the Lunar Crater Radio Telescope concept "nasa's
| Jet Propulsion Laboratory (J.P.L.) is also exploring the idea
| of a radio-wave detector, the Lunar Crater Radio Telescope
| (L.C.R.T.), inside a 1.3-kilometre-wide moon crater."
|
| https://www.nasa.gov/general/lunar-crater-radio-telescope-lc...
| Animats wrote:
| That's a much simpler project. It's deployment, not
| construction. Two metric tons of mesh have to be soft landed
| at the bottom of the crater. Then mobile robots pull it open
| into a large dish.[1] There's a cheaper approach where the
| mesh is pulled open by weights shot out from the central
| lander. Cost estimates are in the US$1 billion to US$10
| billion range, most of which is shipping cost to Luna
| Farside.
|
| [1] https://www.dropbox.com/scl/fi/d4pivfipd9rpb19fm87lq/LCRT
| _NI...
| yinser wrote:
| If you don't see the contradiction in JPL having an active
| research project to put a radio telescope on the moon and
| your original statement then I guess we'll have to agree to
| disagree.
| tim333 wrote:
| The SpaceX 'Starship Human Landing System' is supposed to land on
| the moon in 2025 or so and should have a cargo variant able to
| deliver quite a few tons of gear. It would interesting to send
| some prototype telescope stuff.
| (https://en.wikipedia.org/wiki/Starship_HLS)
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