[HN Gopher] Powering the Lunar Base
___________________________________________________________________
Powering the Lunar Base
Author : mercutio2
Score : 116 points
Date : 2021-08-07 14:32 UTC (8 hours ago)
(HTM) web link (caseyhandmer.wordpress.com)
(TXT) w3m dump (caseyhandmer.wordpress.com)
| zardo wrote:
| With 1/6 g, no wind, and no quakes, I'm not sure you can rule out
| building a 3km tall tower without actually doing a design study.
| llukas wrote:
| https://en.wikipedia.org/wiki/Quake_(natural_phenomenon)#Moo...
| inglor_cz wrote:
| Also, extreme temperature changes. At least compared to
| Earth.
| unchocked wrote:
| I find it odd that the author dismisses hydrogen storage largely
| based on the requirement to mine water for electrolysis and then
| goes on to propose using ~12,000 tonnes of water for thermal
| energy storage.
| tuatoru wrote:
| 12 000 t of water is a large swimming pool (about 5 Olympic
| pools) and could be used as such, perhaps.
|
| Edit: using hydrogen for steelmaking or other reductive
| processes yes; for energy storage, we have better choices.
| You'd make it as you need it.
| baybal2 wrote:
| Storing water does not require pressure vessels, nor cryogenic
| coolers.
| errantspark wrote:
| It pretty definitely requires pressure vessels if you care
| about it's phase.
| natosaichek wrote:
| Well it requires a closed container that maybe has to take
| a few psi of water pressure. It doesn't require anything
| that can tolerate thousands of psi like hydrogen does.
| nine_k wrote:
| More importantly, water does not diffuse through metal
| vessels.
| sfifs wrote:
| Personally, I think the most viable long term option would be to
| build solar farms with 120 degrees separation on the moon's
| circumference so you'd always have a fairly constant amount of
| solar power generation & run a HVDC grid. From what I can make
| out, a 1000 Amps capable Aluminum Composite core power cable
| seems to weigh about 500kg per km [1](I may be mistaken here,
| happy to be corrected). Moon's circumference is about 10000 km &
| so you'd need about 7000km of cabling or about 3500 tons. That's
| only about 20-40 Starship trips to transport the cables itself.
| Maybe with some minimal cladding (no rain/ice etc on moon), it
| could possibly even be laid or buried on the ground vs. requiring
| pylons. Once the solar panels are installed, there's little
| maintenance needed compared to earth (dust) and you could
| progressively add over time.
|
| [1] https://multimedia.3m.com/mws/media/480556O/3mtm-accr-
| techni...
| ramshanker wrote:
| There must be a redundancy of minimum 2 independent cables
| though. Can't risk losing power with any single fault event.
| kwhitefoot wrote:
| Just add another 3000 km of cable to complete the ring main
| then every point is supplied from both directions.
| tuatoru wrote:
| That 1000 A rating probably assumes some conductive and
| convective cooling, and earth-surface temperatures.
|
| It'd need to be bigger. And 1000 A isn't much if you're
| planning to make anything at scale on the Moon.
|
| Great idea though.
| bishoprook2 wrote:
| Is there somewhere on either pole with constant partial
| sunlight? or is there some sort of 'seasonal' tilt?
|
| I like the idea of the three power stations, but you still need
| enough backup power for eclipses.
| politician wrote:
| The cable could be manufactured from the Aluminum in the Lunar
| regolith which could simplify the logistics.
| jfk13 wrote:
| Although shipping the cable-manufacturing plant out there
| might not be entirely trivial either.
| nkingsy wrote:
| How many starships full of copper would be required to run a hvdc
| line between enough points to get constant coverage?
| baybal2 wrote:
| Moon is 10% aluminium, with that constrain, I doubt copper will
| see much use for long range transmission.
| voakbasda wrote:
| Mining and refining aluminum takes a huge amount of power, so
| you're back to hauling tons of wire to build the initial
| infrastructure. Mining is definitely the way to go after that
| bootstrap stage, but this question remains: is this the best
| bootstrap plan?
| inglor_cz wrote:
| You have a shitton of solar power at your disposal _during
| the lunar day_. Lunar surface is raked by the full solar
| constant of power, no atmosphere = no attenuation. That is
| quite a sizzle.
|
| So you can smelt a lot of aluminium during the fortnight
| when the sun is up. And build a web of wires around the
| entire Moon so that during the cold and dark lunar night
| you can get power from the other side of the Moon.
| gpm wrote:
| But one of the key observations from this article is that
| we won't be power constrained, we will be constrained by
| _consistent_ power, since power at night costs far, far,
| more than power during the day.
|
| If we can ship some extra solar panels up and refine
| aluminum during the day, to reduce the cost of power at
| night, it seems likely to be entirely worth it.
| javajosh wrote:
| It's funny, I never thought of electricity as being a big issue
| for a moonbase. There are so many ways to store potential energy
| - you could, for example, put a bunch of moon rock/dust on a
| platform and run electric motors to raise it for 14 days, and
| then, during the lunar night, allow the platform to lower and
| generate electricity. But the remarkable 300 deg temp swing is a
| dream for power generation, although the OP is right that you'd
| need a medium (e.g. lots of water) to harness it as a carnot
| engine. Still, fun to think about since it's a hard, but not
| unsolvable problem.
| gpm wrote:
| I'm a fan of this comment:
| https://caseyhandmer.wordpress.com/2021/04/25/powering-the-l...
|
| TL;DR - Just don't be there during long winter nights.
| TheOtherHobbes wrote:
| Apparently McMurdo Station needs 7000 tons of assorted supplies
| each year. Assuming Moon Base runs on a similar scale, that's an
| initial annual budget of $7bn _just for the shipping._
|
| This assumes air and water are solved problems and don't need to
| be shipped.
|
| Note that oxygen != air. 100% oxygen atmospheres are not a good
| idea for extended stays.
|
| Nitrogen is not common on the Moon. Nor is carbon (for filtering
| or other organic applications.)
|
| It's not easy to imagine a lunar base generating >$7bn of returns
| every year. Apart from space tourism, there isn't a whole lot you
| can do/build/sell on a moon base that has more value on Earth
| than it would cost to transport back here.
|
| Of course you could argue Science, and that's fair enough. But
| literally all the commercial arguments I've seen have been
| "Something will no doubt appear" - which is possibly not going to
| win over rational investors.
| jhgb wrote:
| > Apparently McMurdo Station needs 7000 tons of assorted
| supplies each year. Assuming Moon Base runs on a similar scale,
| that's an initial annual budget of $7bn just for the shipping.
|
| This would never be a real scenario. McMurdo supply runs are
| not designed for such high transportation costs. With such
| transportation cost expectations you'd be pressed to lower the
| mass of the supplies in the first place so that the sum of the
| cost of preparing the supplies and the cost of transferring
| them were minimized. You need to compare two Pareto optima
| completely, not just one axis of them.
| ketzo wrote:
| Yeah, but flipside, you're probably gonna need things on the
| Moon that you wouldn't for a terrestrial base. I think it's
| fair to assume that the $7bn a year figure is just a very
| rough number, but still a useful one for understanding just
| how outrageously expensive it would be to maintain a Moon
| base.
| jhgb wrote:
| You kind of have a model of a lunar space station in the
| form of ISS. That's definitely not 7000 tonnes of supplies
| for a base. Maybe something like 15 tonnes per year or so.
| aplummer wrote:
| So that's 1% of the US military budget. Double it and it seems
| affordable? What is the return on aircraft carriers 8-11, when
| the next most powerful nation has 1.
| taneq wrote:
| Also let's be honest, aircraft carriers are super awesome and
| fun and good for scaring brown farmers but in a modern war
| against an equal power they're not especially practical.
| Couple o' kinetic strikes and your $13 billion new toy is
| slag on the ocean floor for like, what... cost to get mass to
| LEO is $2600 per kg so if we want 100 special order
| deliveries of 1-ton rods from God that's $2.6mil per rod =
| $260 million to sink a $13 billion aircraft carrier and
| destroy how many billions of dollars worth of F22s and
| ammunition?
|
| Like, I love aircraft carriers, they're so cool. But also
| physics says not so effective. :S
| jeffdn wrote:
| That's also assuming that the satellite that drops said
| rods can maneuver into the orbit required to drop the rod
| without:
|
| 1. getting knocked out at the commencement of hostilities
| by an anti-satellite weapon
|
| 2. the Defense Intelligence Agency/National Reconnaissance
| Office noticing and telling the carrier to change course
|
| 3. getting blown up by an anti-satellite missile fired by
| an aircraft, or a member of the carrier's strike group
|
| Rods from god are a much more potent weapon when used
| against static targets!
| taneq wrote:
| 1. Sure once we're under way but that doesn't change how
| good they are from a first strike perspective.
|
| 2. As a species we can land a rocket on a barge, do you
| think we can't land a big crowbar on a slowly moving
| target?
|
| 3. Might make 2 more difficult but a 1-ton tungsten rod
| is pretty durable.
|
| Certainly more potent against a static target but with
| modern tech and one skilled, ethically ambivalent
| engineer, these days you could probably hit a row boat.
| Andrew_nenakhov wrote:
| Because the barge is carefully positioned to be in a
| place this exact rocket drops from the sky.
|
| Satellites are not 'sitting in orbit', they are falling
| on earth extremely fast, and not reaching it only because
| they fall sideways. Since they go very fast, they have
| immense momentum. To attack a target you have to steer
| that momentum elsewhere, and _that_ takes a lot of energy
| and precision,and you also have a _very_ small attack
| area for every satellite. So to cover all earth reliably
| you 'll need a constellation with numbers like Musk's
| Starlink - i.e. thousands of satellites.
| dnautics wrote:
| Honestly the most important use of a carrier (especially
| for china) is going to be in supporting naval vessels
| interdicting against pirates harassing or stealing from oil
| tankers shipping from the middle east; china depends on
| mideast oil to feed its people. The us does not as of
| 2019-ish, and may in the short to mid term cease protecting
| international sea lanes especially in the mideast since we
| are rapidly disengaging out interests in the area (e.g.
| pulling out of Afghanistan).
| [deleted]
| kcb wrote:
| I'd imagine in the opening phase of a war most orbital
| military systems aren't going to last very long.
| driscoll42 wrote:
| The problem is that if you want one aircraft carrier on
| active deployment, you really need three physical carriers.
| One on patrol, one about to go on/off patrol, and another in
| maintenance. So really 11 carriers lets you actively patrol
| 3, maybe 4 zones. And again, that's just one carrier in that
| area, if you can to concentrate resources you might get a few
| more there, but then you're delaying maintenance/training. If
| anything the US needs more carriers as recent years have
| taught the navy.
|
| https://thehill.com/blogs/congress-blog/homeland-
| security/25...
|
| https://www.popularmechanics.com/military/navy-
| ships/a359282...
| pirate787 wrote:
| Except that aircraft carriers are obsolete-- sitting ducks
| that will be sunk by long range guided missiles within
| hours of the next Great Power conflict. Submarine carriers
| with fleets of drones are the obvious replacement.
| robertk wrote:
| In fact, they have 2 in active service and are rapidly
| constructing more.
|
| https://www.businessinsider.com/leaked-photos-show-chinas-
| ne...
| nsonha wrote:
| As long as there is a race then it justifiable, is it
| bigger fool economy or not quite?
| dwaltrip wrote:
| It looks like you are using a price of $1000 / kg to get that
| figure. Prices will be much lower than that once fully reusable
| rockets are widely deployed.
|
| Currently, equipment costing tens of millions $USD are thrown
| away on every launch. It's hard to overstate the shift fully
| reusable rockets will bring.
| tintt wrote:
| People were optimistic about LEO shipping costs when the
| Space Shuttle program just started, but it didn't exactly
| work out economically. Partially reusable F9 was meant to
| decrease lunch costs, and it did, but not to the extent some
| hoped. Starship, no doubt, will bring prices down, but then
| again, even $1k/kilo to the moon surface sounds kind of... an
| aspirational stretch.
| sandworm101 wrote:
| Retirement homes in the lower gravity? And there is the
| helium-3 fusion dream. That's the purpose of so many recent
| scifi moonbases.
| garmaine wrote:
| Helium-3 from the moon will never be a commercially viable
| energy source. At best it might be captured incidentally as
| part of other mining operations and sold to research labs.
| There are just too many other fusion options that, while not
| as ideal, have fuels that are vastly easier to obtain.
| cstross wrote:
| Get back to me on 3He fuel mining in the regolith after (a)
| demonstrating a working 3He cycle aneutronic fusion reactor
| (hint: it's _much_ harder than the D-T fusion cycle that we
| haven 't got working yet, although ITER is supposed to
| demonstrate it), and (b) ruling out other aneutronic fusion
| fuels like, oh, proton-Lithium-7, or proton-Boron-11 ...
| which are only somewhat harder to achieve than 3He fusion,
| and which run on fuels readily available here on Earth.
|
| (My gut sense is that if aneutronic fusion is practical _at
| all_ then it 'll be cheaper to build more expensive reactors
| that can run on terrestrial fuels so cheap we use them for
| car batteries and as an insecticide, rather than slightly
| less difficult reactors that are fuelled by magic
| extraterrestrial unicorn sparkle-dust.)
| ben_w wrote:
| I saw a blog calculate that regolith He3 was so sparse that
| even with a reactor to use it in, one would make more
| energy from purifying the metals, coil-gunning the purified
| ingots just past the L1 point so they would fall to Earth,
| and setting fire to the ingots. Or, entirely separately, by
| pointing the ingots at electromagnets and collecting the
| energy from the induced currents from electromagnetic
| braking.
|
| (I wish I could find the original and link to it. For all I
| remember it might have been you who wrote it).
| medstrom wrote:
| 70 wealthy retirees, each paying $100M annually.
| nsonha wrote:
| Let's coerce them into spending that money, in fact what do
| old people need that much for, let's seize it for science
| sonograph wrote:
| The market for retirees who are willing to pay $100M
| annually to live in a pressurized bubble on the moon is
| maybe one or two, for only one annum
| sandworm101 wrote:
| I assume that catering to those 70 Uber wealthy might
| increase cargo needs slightly. But it would cut down on
| family visits. The kids might pay to have grandpa sent to
| the moon.
| Andrew_nenakhov wrote:
| It is likely that permanent low gravity will kill them even
| before boredom and depression from realization that the rest
| of their lives will have to be spent in those small confines.
|
| (Low gravity is extremely unhealthy. And even a relatively
| short 1-week stay in such conditions severely affects cardio
| muscles, so that super-healthy astronauts have to exercise
| for several hours per day to keep their heart in shape)
| Nexialist wrote:
| A paper I read recently (Harper 2016 - 10.1089/space.2015.0029)
| has numbers based on the supplies needed to the ISS.
|
| The gist was, "Without some sort of recycling and/or use of in
| situ resources, meeting the lunar settlement goal of 100 people
| would require delivery of over 1 million kilograms of life-
| support consumables per year."
|
| And then assuming a PLSS life support system you get to to
| needing about 5500kg of consumables delivered per person per
| year.
|
| [1] https://www.liebertpub.com/doi/abs/10.1089/space.2015.0029
| WalterBright wrote:
| All the biomass would have to be recycled back into water and
| food.
|
| The gating thing may be if lunar dust is workable as raw
| material for soil or not.
| LatteLazy wrote:
| I can't tell you whether the figures are accurate, or if it's a
| good investment but...
|
| $7bn is 20 usd per US citizen. If the US and EU did it together
| its less than $9 per person per year.
|
| We can afford vastly more for aircraft carriers or walls
| between the us and Mexico or farm subsidies admin costs or
| medicare.
| ben_w wrote:
| Yeah, but one of the big parts of the Brexit referendum's two
| Leave campaigns was moping about a number merely twice that
| size being spent for all the combined benefits of a customs
| union and single market (the absence of which is now being
| blamed as a partial cause for empty supermarket shelves!),
| not something which cynics already deride as a billionaire
| size-measuring contest. Much as I love space, any proper
| space program -- even ones well short of colonies -- must do
| something tangible down on Earth.
| LatteLazy wrote:
| I'd be careful taking anything from the brexit campaigns as
| evidence of anything. It was a baseless conclusion in
| search of excuses...
|
| I take the wider point though. Its hard enough to get
| voters to find money for anything other than pensions, tax
| cuts or bombs.
|
| People love criticizing Bezos and Musk for spending money
| on rockers. But I actually think they're fulfilling
| something we as a society have sadly neglected.
| samstave wrote:
| Will we ever get to some other metric than "money" WRT
| 'returns'?
|
| I've always wondered about this WRT "black budgets" and the
| theories about Breakaway Civilizations; "Of what value does
| 'Money' have in Space?"
|
| ---
|
| Lets assume that trillions are funnelled off into black budgets
| for [purposes] -- that assumes that hte 'money' (fiat currency
| (paper/the-concept-of-value/10101010s/etc)) is being used to
| pay for/buy [goods/services] -- Where the hell is all this
| money going? is there an economy and a place where such vast
| amounts are being spent.
|
| Lets assume they are paying their
| engineers/suppliers/companies/etc - the Deep Workers far beyond
| the depths of SkunkWorks etc - where exactly is that money
| going? What are they buying.
|
| This has been the biggest flaw for me in thinking about
| Breakaway Civs - and spending money/making money in Space.
|
| If we were to assume that the moon had some set of valuable
| minerals/etc that would be beneficial to mine and then return
| to earth, where is the value in mining Tungsten on the Moon
| (given your shipping calc, for example) and bringing that back
| to earth unless the earth had none of said resource...
|
| Personally, it would be interesting to think about how a
| production capability could be built on the moon to support the
| fabrication and manufacture of vessels on a lunar-orbitting
| ship-dock, which then could carry on to mars/wherever... and
| pull from the resources of metals on the moon, which AFAIK is
| supposed to have a lot of metal...
|
| Further, why has Musk constantly talked about "going to Mars",
| but said seemingly very little about doing a dry-run, proto,
| etc to the Moon first?
|
| Shouldnt building a Moon-base be much more immediately
| important than a Bezos-esque trip to Mars?
|
| FFS SpaceX is talking about getting to Mars, but all the
| required life support eco-system requirements do not appear to
| have been even addressed?
|
| It all feels amiss... Please enlighten me.
| tintt wrote:
| $7bn is just a third of NASA budget, it's doable, but you're
| right, there's no reason to go as big as McMurdo Station with
| today's technology.
| taneq wrote:
| > Assuming Moon Base runs on a similar scale, that's an initial
| annual budget of $7bn just for the shipping.
|
| Wow that seems like a lot, which figures for launch and payload
| delivery are you using? Because NASA was like $1mil per kg to
| LEO and isn't SpaceX like $5000?
| go_elmo wrote:
| Looking forward for the re-boost of nuclear space-technology so
| many scientific opportunities!
| aerophilic wrote:
| The idea I have always liked, though have never done the numbers
| on, is a giant "heat pipe" that would circle the moon. You could
| put it on any latitude you want, but you effectively take
| advantage of the temperature gradient to continuously flow a
| gas/liquid around the moon. That in turn turns turbines attached
| wherever you need the power.
| alphydan wrote:
| for those interested, this Austin startup is hiring and building
| potential lunar bases: https://www.iconbuild.com/technology/space
| papito wrote:
| This doesn't even mention Helium-3? Come on.
| ncmncm wrote:
| Lunar Helium-3 is a mirage. There is no plausible scenario
| where trying to gather lunar He-3 turns out well.
| Diggsey wrote:
| How about two/three sites around the Shackleton crater which beam
| power back and forth wirelessly across the crater as each site
| goes in and out of sunlight?
| ncmncm wrote:
| Cabling would be the thing.
|
| Shackleton Crater might make an awesome radio telescope.
| edgyquant wrote:
| This is a sexy idea. I don't know if it would work, but it
| would be fun to work on
| h2odragon wrote:
| dont miss the bit on "remotely beamed microwave power."
|
| "silly idea" it may be but now i _want_ a mega-maser as described
| for my own sporting purposes.
| coatdoor wrote:
| Wouldn't you just use earthlight and normal solar panels? The
| internet says moonlight is 1/345th the power of sunlight but
| once you factor in Earth's larger radius and larger albedo you
| get 1/9th the power of sunlight. IE you just use 10 times as
| many solar panels to get you through the night.
| jhgb wrote:
| > The internet says moonlight is 1/345th the power of
| sunlight but once you factor in Earth's larger radius and
| larger albedo you get 1/9th the power of sunlight.
|
| That sounds weird. As per Wikipedia, Sun's apparent magnitude
| is around -26.7, full Moon's is -12.7, so the Sun is 400000
| times brighter than the Moon under the best circumstances.
| Earth being larger can't correct this by three orders of
| magnitude.
| MCllorf wrote:
| I'm not trained in STEM at all but these discussions are always
| a little confusing for me because if our goal is to bootstrap
| mining/manufacturing in space, why does everyone jump to
| expensive, complicated and inefficient solutions like "energy
| lasers" when we've had power lines for like 150 years and can
| make them on-site much more easily?
| jdavis703 wrote:
| This question is answered in the article and I guarantee you,
| most STEM specialities will never discuss this particular
| problem.
|
| Anyways, the TL;DR is all those cables weigh a lot, so
| launching them in to space isn't cheap.
| whatshisface wrote:
| Well, cables are going to be cheaper at some distance and
| power beaming will be cheaper at a greater distance, and the
| question is, where's the crossover.
| h2odragon wrote:
| Look at the efficiency numbers on contact free charging
| pads. "Beaming" fails for power transmission immediately;
| it needs other factors to justify the efficiency hit; and
| once you're out of near field its much much worse.
| gpm wrote:
| Microwave transmission of power hits 70 or 80% efficiency
| http://large.stanford.edu/courses/2011/ph240/shu2/
|
| What you're seeing with phones isn't microwave, but
| inductance, very different technology with very different
| benefits/drawbacks.
| sjansen wrote:
| The article mentioned why very quickly while discussing
| building multiple solar farms so that at least some aren't in
| shadow at the same time: sending enough cable up on rockets
| to connect all of them would be more expensive than the
| "expensive, complicated and inefficient solutions".
| extrapickles wrote:
| Its likely because bringing a smelter and wire drawing
| machine don't feel "space age". Also most people think of
| small bases where its not cost effective to bring a bunch of
| manufacturing capacity as quite a few processes don't scale
| down well. Mining is another issue as you would need to find
| good sources of each major metal within transportable
| distance of your base.
|
| With the current capital cost of ~$50/W to beam power, its
| reasonable to think about for small endeavors, but for a base
| designed for 100k people making power lines onsite is better,
| as you will need that manufacturing capacity for other things
| anyway.
| Uke wrote:
| it might be a weight constrain?
| extrapickles wrote:
| Its probably more realistic to put a few satellites in orbit of
| the moon and beam power from them. This keeps the distances
| down so the transmitter and receivers can be more reasonably
| sized.
|
| If you also switch to laser power beaming, they can illuminate
| the existing solar farm so a separate receiver is not needed.
| h2odragon wrote:
| I'm totally in favor of any plan that has multiple megawatt
| SPACE LASERS as part of it, yes.
| hereforphone wrote:
| Do they expect to outdo the sun?
| h2odragon wrote:
| In one very specific frequency band, at one comparatively
| small place, yes. by a large amount. Ocean vs firehose.
|
| Or, better: In the same way every "daytime headlight" you see
| is outdoing the sun.
| hereforphone wrote:
| Which 'frequency band'?
| https://www.researchgate.net/figure/Spectral-power-
| density-o...
| jhgb wrote:
| The one that the receiver is the most sensitive to. The
| fact that sunlight comprises many wavelengths is the
| reason why single-junction cells have comparatively low
| efficiency.
| rrss wrote:
| microwave
| hereforphone wrote:
| Brilliant answer
| h2odragon wrote:
| > Achieving a beam that narrow (1/2000000 rad) from the
| Earth would require a phased array spaced out over a much
| larger area, at least 200 km at 5 Ghz (6cm).
|
| I doubt they'd want a very large band but in microwave
| work I dunno what counts as "large".
|
| and i'm a little afraid to go look deeper into this
| because i'll wind up tearing up junkyard microwave ovens
| and building something i shouldn't.
| hereforphone wrote:
| It won't let me reply to your response to _my_ response
| to this comment. But just let me say that as an engineer
| with tons of RF experience, you 're full of shit.
| IggleSniggle wrote:
| At least one person here is exploring an idea and trying
| to learn. I don't get how that makes a person "full of
| shit"
| jacquesm wrote:
| Maybe you should add the HN guidelines to your 'tons of
| RF experience' and see where that leads you?
| TigeriusKirk wrote:
| This thread would be interesting if you would show your
| work. I'm here for interesting ideas, not people
| declaring their expertise without educating us.
|
| Educate me.
| hereforphone wrote:
| I'm not the one making the wacky assertions. Ask the
| parent posts to demonstrate their claims first.
| h2odragon wrote:
| The only assertions I've made are that im interested in
| this idea. The assertions the blog post made included a
| link to another post [1] under the text "I have written
| more than once about how silly this idea is". referring
| to "the space-based solar power trope."
|
| You're arguing against ... what then?
|
| [1] https://caseyhandmer.wordpress.com/2019/08/20/space-
| based-so...
| macintux wrote:
| One of you is performing some mildly interesting
| speculation out of confessed limited knowledge. One of
| you is being rude, insulting, claiming to be the expert,
| but offering no new information.
|
| One of you is contributing to the thread, at least. It's
| not you.
| hereforphone wrote:
| The headlight vs. sun comparison (which I think was an
| edit?) is irrelevant because we're comparing the amount
| of energy deliverable over distance. The energy delivered
| by the sun (at a tenable band) vs. the energy delivered
| by the remote transmitter on earth, after the 'link
| budget' has been applied (taking into account distance,
| atmospheric attenuation, and so on) are the two things
| that need to be compared.
| h2odragon wrote:
| I beg you pardon, im not arguing for the idea of a earth
| to moon microwave power link as viable. or sensible. I
| think it's _beautifully insane_ , i have severe doubts
| about the actual practicality of such a thing, etc.
|
| But thats the thing: now i want to do a mad max maser on
| a truck with maybe dozens of magnetrons if i could tow a
| generator...
|
| It fits with my "Orbital Slingshot" project so well, too.
| hereforphone wrote:
| What is your Orbital Slingshot project?
| h2odragon wrote:
| I'm glad you asked :)
|
| It's a totally silly idea to built a big ass slingshot
| that throws things as high as possible. I figure calling
| it an "Orbital Slingshot" makes it at least as viable and
| investment worthy as some of the other efforts [1] and
| [2] forex.
|
| If I can get my daughter to do some artwork I might fire
| up a web page for it finally.
|
| [1] https://www.space.com/23015-slingatron-reusable-
| launch-syste...
|
| [2] https://www.nextbigfuture.com/2018/02/spinlaunch-is-
| using-la...
| [deleted]
| rrss wrote:
| Ok, check my math.
|
| basics: solar constant: 1.36 kW / m^2
| earth-to-moon range: 400 km
|
| parameters from the article: frequency: 5
| GHz -> wavelength: 6cm earth antenna array linear
| dimension: 200 km transmit power density: 100 W/m^2
|
| Let's assume that the earth antenna array elements are
| 50m wide, and spaced out such that they cover 1% of the
| total 200km * 50m area, for a total antenna aperture of
| 1e5 square meters (10% of the SKA). Combining the stated
| transmit power density of 100 W/m^2 with the antenna
| area, we get a total transmit power of 10 MW.
|
| Throw it at Friis: power density at moon
| = transmit power * earth antenna area / (range^2 *
| wavelength^2) = 10e6 watts * 1e5 m^2 / ( 400e3^2
| m^2 * 0.06^2 m^2) = 1.73 kW / m^2
|
| Atmospheric attenuation at 5 GHz is pretty minimal. If we
| conservatively assume 20% loss, I think we still end up
| with a higher power density at a single frequency than
| from the sun across the entire spectrum.
|
| I don't think anything like this will ever be built, but
| I don't see why it is impossible. Where's the mistake?
| inglor_cz wrote:
| > earth-to-moon range: 400 km
|
| Three zeros seem to be missing.
| rrss wrote:
| yikes, thank you
| state_less wrote:
| I'd imagine they'll need to do a number of electrochemical
| reactions to make oxygen to breathe and fuel to burn, etc... Use
| an oversized solar array and store the chemical products in
| tanks. Batteries are chemical stores too, no? Anyhow, not sure of
| the efficiency of all these reactions, but more panels could help
| until further reaction improvements can be made.
| Diggsey wrote:
| The article does consider that option via splitting and storage
| of water, and then recombination via hydrogen fuel cells.
|
| According to the article the mass of the storage vessels needed
| to store 2 weeks of pressurized hydrogen and oxygen are
| comparable with the mass of batteries you'd need, although I
| haven't done the calculations myself... Intuitively I would
| expect this to be more efficient than batteries though.
| gpm wrote:
| I think the point here is rather that power load at night can
| be much lower than power load during the day, if most of the
| energy is going to optional processes like making oxygen
| and/or rocket fuel.
| ncmncm wrote:
| If you are storing gases at the lunar pole, liquid is the
| right form. Then the tanks are very light and cheap.
| Liquifying gases is very easy there.
| fnord77 wrote:
| another Musk fanboi, redoing the speculative work that NASA did
| in the 70s and then claiming credit for it.
| ttul wrote:
| So, nuclear then.
| edgyquant wrote:
| It's both hilarious and sad that we don't talk about nuclear
| because other countries will think we're building bombs. I
| definitely think the space treaty has to go and be replaced by
| a reasonable treaty that allows militarization of space.
|
| Right now it's akin to nobody building planes that can Cary
| more than a single person (and no cargo) because they know it
| gives the other party an advantage
| MichaelZuo wrote:
| You want to allow every nation to be able to militarize
| space? Since that's what a renegotiated UN treaty implies.
| edgyquant wrote:
| Yes. We are only putting it off at the moment and it's
| hampering progress. If we could put nukes in space it would
| remove the stigma of using nuclear energy. And other
| countries could build their defenses so they aren't as
| worried. We should build a more realistic treaty that
| doesn't hamper progress.
| gpm wrote:
| You're creating an imaginary strawman and arguing against it
| here.
|
| The space treaty does not ban nuclear power, only nuclear
| weapons. Nuclear power is just for the most part not worth
| it, and in the rare cases where it has been worth it, we've
| used it, in the form of RTGs because that's the only form of
| nuclear that has ever made sense for any space mission we've
| launched. Nuclear power is talked about a _ton_ in the space
| community, with everything from "here's a way we could
| potentially power spacecraft to bases" to "hey, maybe we
| could build a nuclear powered rocket engine and get much
| better mass ratios when we send things to mars".
| edgyquant wrote:
| I said that because nuclear weapons are restricted when
| anyone _wants_ to build anything nuclear in space it gets
| put on the back burner because no one wants to piss of
| other countries (who are understandably afraid of it being
| a covert weapon.)
|
| I didn't create a strawman, you did by claiming I did and
| then arguing against that. You did by claiming it's talked
| about in the "space community," whatever that means, when
| we're talking about actual space infrastructure in the
| implementation phase.
| gpm wrote:
| It is simply not the case that nuclear weapons being
| restricted means anything nuclear in space gets put onto
| back burner. And there is no serious opposition from the
| poliferation from despite your strawman that there is and
| your strawman that it is forbidden by the otuer space
| treaty. This is not a strawman on my part, I am directly
| addressing the argument you actually made in your
| comment, even if I was wrong it would not be a strongman,
| and I resent the fact that you would say "no you" when it
| is obviously false.
|
| Space community here is just a throwaway phrase I used
| for the various entities involved in Space, space
| agencies like nasa and the esa, research agencies like
| darpa, and the huge groups of contractors around them.
| For instance the latest award of funding that I'm aware
| of from the US is that General Atomics was awarded $22
| million in April of this year for nuclear thermal
| propulsion research (and theoretically to demonstrate in
| on orbit by 2025, I'm fairly skeptical that they will
| meet that goal): https://www.ga.com/general-atomics-
| awarded-darpa-contract-to...
| inglor_cz wrote:
| The tricky part about nuclear in space is that you either
| manufacture the fuel somewhere off Earth too, or you need to
| launch it from Earth, with a non-zero chance of the rocket
| failing and tons of highly radioactive fuel contaminating the
| atmosphere.
|
| I would probably risk that on a rocket that proved to be
| reliable enough, say, 500 launches in a row without a single
| failure.
| ncphil wrote:
| Yeah. Nuclear may not make sense here on Earth -- even
| Antarctica -- where the environmental and human health
| consequences are practically unavoidable (especially when
| implemented by the lowest bidder), but space outside of LEO is
| another matter. NASA is in fact looking at it.
| https://cen.acs.org/energy/nuclear-power/NASA-thinks-
| nuclear.... Although the idea of migrating researchers to a
| sunlit base when night falls at their primary base has
| potential, it's probably going to be more practical to stand up
| a whopping big RTG or full-on fission reactor a distance off
| from the habitats. Space borne fission plants are going to be
| necessary anyway if we're ever going to send people to the
| outer solar system (Jupiter, Saturn, Uranus, Neptune). We might
| as well learn how to make them work on the Moon ("It's a damned
| research project!").
| devoutsalsa wrote:
| Nuclear is basic the safest (and climate change friendly)
| form of power generation am we have. Isn't it?
| ncmncm wrote:
| On Earth's surface? No. But various forms make sense
| elsewhere.
| ncmncm wrote:
| A smallish chunk of Strontium-90 would safely power quite a
| lot of moonbase for years, as the Soviets did their remote
| lighthouses. Strontium-90 is the ideal radionucleide;
| emitting negligible gamma rays or neutrons, it just sits
| producing heat.
|
| For power in the cloudtops of Venus, Titan, Saturn, Uranus,
| or Neptune, a full-scale nuclear reactor is as simple as a
| naked atomic pile hanging near the bottom of a big fabric
| tube with a wind turbine at the top, supported by a balloon.
| All the radiative output goes into heating the air around the
| pile, which rises and drives the wind turbine, which is the
| only moving part.
|
| On the gas giants, it would have to be supported by a hot-air
| balloon, because the atmosphere is hydrogen.
|
| On all four planets, surprisingly, gravity is very close to
| Earth-normal. (On Titan it is rather less.) Orbital velocity
| at the gas giants is much higher, though, so as comfortable
| as it might be there, it's hard to get home from them.
| andyxor wrote:
| the only answer is nuclear, simply because of energy density
| required for space applications.
|
| the creators of the original solid-core Krusty/Kilopower reactor
| are trying to commercialize the tech, I hope they have enough
| funding (@sama, I hope this is on your radar)
| https://www.spacenukes.com/
|
| This is the first fundamentally new reactor actually built and
| tested by NASA in more than 50 years (vs. countless paper
| designs) https://www.nasa.gov/mission_pages/tdm/fission-surface-
| power...
|
| EDIT: I highly recommend watching the presentation by David
| Poston "Space Nuclear Power for Mars"
| https://www.youtube.com/watch?v=luQfEYs2L0w
| baybal2 wrote:
| I don't see battery storage as a problem for the first outpost,
| but yes, kilopower reactors were made exactly for this.
|
| Another option for early missions is just to limit them to 14
| days.
|
| Heating of the base can be achieved by preheating the regolith
| deep beneath the surface. With regolith density we know, it
| should be well feasible.
|
| Thermal insulation can be made very efficient in space because
| there is no atmosphere.
|
| I see a nuclear/rtg base power for life support, and solar
| powered regolith smelting following the 14 day cycle.
| Robotbeat wrote:
| That's pretty reasonable. Particularly since nuclear (fission
| or radioisotope) produces a lot more heat than electricity
| (thermal to electrical conversion efficiency is just 23% for
| Kilopower and 3-9% for RTGs), so using it for base heating
| during the night is a much better argument. And even some
| solar powered rovers like Spirit and Opportunity used small
| radioisotope heat sources to stay warm.
| Robotbeat wrote:
| "The answer is nuclear" is repeated often but often is an
| innumerate answer. Kilopower for most uses in the inner solar
| system performs considerably worse than solar. The power to
| weight ratio of Kilopower is about 6-7W/kg, no better than old
| time RTGs. UltraFlex solar panels do about 150W/kg near 1AU.
|
| Nuclear in the lunar case may be useful for base power due to
| the long lunar night which makes storage pretty heavy, but
| nuclear is actually usually WORSE performance than solar,
| producing much less power for the same mass. It's only in the
| outer solar system around Jupiter or in niche cases like lunar
| night where nuclear has a solid lead on solar. Otherwise it's
| similar or worse, besides being a lot more expensive. ~$100
| million for 10kWe Kilopower.
| slfnflctd wrote:
| > in niche cases like lunar night
|
| Why would lunar night be considered a niche case? Wouldn't
| this affect any and every long term installation?
| Robotbeat wrote:
| No. The lunar night is 14 days long, which means you need
| 336 kWh of storage for every kilowatt of constant power. In
| orbit, you only need maybe 30 minutes of battery, so
| 0.5-1kWh per kilowatt of power. Mars surface has a similar
| day/night cycle as Earth, plus a need for margin for dust
| storms, so nuclear is roughly the same mass as solar if you
| need near constant power, but still solar is potentially
| cheaper if you need a LOT of power.
| inglor_cz wrote:
| Another nearby place with really long nights is Mercury.
|
| Well, Venus too, but surface conditions are absolutely
| unsurvivable for people. While you can build an
| underground city on Mercury.
| andyxor wrote:
| i think you are missing the point of Kilopower, it was to
| build a working micro reactor prototype on realistic
| timeframe and actually ship it, they have designed the
| extension of this to MW scale where energy density is order
| of magnitude better.
|
| Nuclear scales better than any other source of energy. How
| many sq feet of solar panels do you need for 1, 10, 100,
| 1000, 10000 MWe, now translate it to lbs and $$$ cost
| (including shipping to the moon or mars base), also consider
| dust and lunar night conditions affecting solar use.
|
| if you look at scaling it vs. weight and cost (including
| maintenance and replacement panels over 20-30 years), solar
| is no competitor to nuclear.
| Robotbeat wrote:
| No, the larger nuclear power plants (50kWe) NASA has
| developed to reasonable TRL are still around the same power
| to weight ratio. Nuclear, in addition to everything else
| like the dynamo and the reactor itself, requires heavy
| radiators.
|
| Also, Kilopower has a SHORTER lifespan of about 15 years
| whereas solar can last 30-50 years (solar degradation is
| much slower than is often claimed, at least when we'll
| engineered and in the absence of high humidity) as there's
| no moving parts and nothing to refuel. Remember,
| terrestrial nuclear reactors are regularly refueled
| (annually?) and maintained.
|
| The traditional argument has always been that nuclear
| scales better than solar, but usually such comparisons are
| looking at sandbagged, outdated solar panels and very low-
| TRL nuclear designs relying on super high rejection
| temperatures (ie unrealistic) or shorter lifespans.
|
| I'm not anti-nuclear by any stretch, and I fully support
| increased funding and deployment of nuclear power, but I
| think there has been a lot of hand waving by some nuclear
| advocates. If you look at actually achievable, near term
| nuclear designs, none of them perform anywhere near as good
| as solar does in orbit near 1AU, and it's not even close.
| It's surface applications or outer solar system where
| nuclear has a chance against solar. Outside of those cases,
| solar is much more powerful for a given weight (meaning
| cheaper to transport) plus being far cheaper to build and
| not requiring special launch vehicle risk mitigations
| (currently, the only nuclear-rated launch vehicle is Atlas
| V... and every nuclear launch must be approved by the
| executive branch).
|
| (A human Mars base may benefit from a mix of power sources
| for resiliency purposes.)
| mschuster91 wrote:
| I wonder... we used to use electrically heated stone as storage
| medium for heating homes, until it became uneconomical due to
| energy price hikes.
|
| A lunar base could electrically heat up a _lot_ of easily mined
| rock and use that to store enough heat to keep the base warm
| enough?
| bbojan wrote:
| Yes, but that's not an issue here. Life support would require a
| lot of electrical energy, not heat.
| mschuster91 wrote:
| What do you need for basic human life support? Light, oxygen
| generation/CO2 removal, water, and electricity for vehicles
| and work appliances.
|
| Oxygen and water can be stored in tanks sufficient enough to
| ride out the 14 days dark cycle, LED lighting is extremely
| efficient (especially if everything is under 9m of moon soil,
| so no light can escape useless to space), the only thing that
| may be a problem is CO2 removal - no idea how much energy
| that uses.
| gpm wrote:
| I think CO2 depends heavily on what you're doing with it.
|
| You filter CO2 out of the atmopshere using zeolite beds at
| relatively low temperature/high pressure, you then recharge
| those by venting the beds at relatively high
| temperature/low pressure.
|
| If you're venting the CO2 to space (they do on the ISS), I
| don't have numbers/proof to back this up but you probably
| don't need much energy at all. You just pass air through
| the absorbing bed at ~1ATM (i.e. with a fan), and a heat
| exchanger from the venting bed to the absorbing bed might
| even be enough to keep the temperatures in the right range.
|
| If you're capturing the CO2 afterwards however, you
| probably need some more energy-expensive machinery. Again,
| I don't have numbers, but you're definitely talking about
| running a compressor to force the venting CO2 into a tank
| now, and you might want to compress the absorption side as
| well to get a bigger pressure gradient.
|
| The only real use of that captured CO2 is to recycle it
| into something useful (e.g. O2 and CH4 using the sabatier
| reaction), and that reaction is going to be endothermic,
| but you can probably just store the CO2 until you have
| sunlight and do it then.
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