[HN Gopher] Caltech to launch space solar power technology demo ...
___________________________________________________________________
Caltech to launch space solar power technology demo into orbit
Author : WalterBright
Score : 98 points
Date : 2023-01-05 17:49 UTC (5 hours ago)
(HTM) web link (www.caltech.edu)
(TXT) w3m dump (www.caltech.edu)
| cratermoon wrote:
| See also https://dothemath.ucsd.edu/2012/03/space-based-solar-
| power/
| c-smile wrote:
| Problem is not in harvesting the energy but in delivering it.
|
| The only reasonable option is to beam highly energetic beam back
| to Earth. Do we want us to be browned by l/masers from the orbit?
| JumpCrisscross wrote:
| > _only reasonable option is to beam highly energetic beam back
| to Earth_
|
| This is how we _should_ do it. But we can't. Fortunately, the
| sat-to-sat laser folks are working on that kit. In the
| meantime, these proposals tend to focus on microwaves.
|
| In any case, to the degree this one day has an economic case
| around Earth, it's in powering low-orbit satellites. Not
| punching through the atmosphere. That said, I don't have any
| obvious near-term high-power use cases for a LEO constellation.
| c-smile wrote:
| > to focus on microwaves
|
| Ah, it will be masers then ... and so together with masks we
| will wear saucepans ...
|
| We do not need additional energy to be delivered to the Earth
| from outside, we are warming it already.
|
| Instead we need to harvest energy that is heating up Earth
| surface already.
| throwaway4aday wrote:
| Why have I been seeing this egregiously wrong idea
| everywhere lately? Delivering power in the form of
| microwaves to the Earth is not going to cause any warming.
| Even if we were to purposefully beam it straight into the
| ocean and heat the water we just aren't capable of
| delivering enough wattage to make a serious difference. The
| reason global warming is a concern is because of the
| greenhouse effect of CO2 trapping the _Suns_ heat which is
| an energy input that we can 't even come close to
| approximating.
| JumpCrisscross wrote:
| > _do not need additional energy to be delivered to the
| Earth from outside, we are warming it already_
|
| Waste heat isn't our problem.
|
| > _we need to harvest energy that is heating up Earth
| surface already_
|
| If we're being artistic that's what an in-orbit solar
| panel, which at least part of the time blocks photons from
| reaching the Earth, does.
| WalterBright wrote:
| In January 2023, the Caltech Space Solar Power Project (SSPP) is
| poised to launch into orbit a prototype, dubbed the Space Solar
| Power Demonstrator (SSPD), which will test several key components
| of an ambitious plan to harvest solar power in space and beam the
| energy back to Earth.
| wrycoder wrote:
| It launched successfully.
|
| I'll point out that a space-based solar array with a microwave
| power downlink was on the front cover of IEEE Spectrum around
| 1971. The article ran the numbers and pointed out the technical
| challenges.
|
| So, this idea is not new, but it hasn't gained enough support
| over the last fifty years to get a project off the ground.
| xxr wrote:
| I first learned about the idea from SimCity 2000[0]. Not
| saying it was the impetus here, but I wonder what amount of
| the continuing interest in orbital power is due to SC2k. (I
| suspect my experience is not unique here on HN, but I wonder
| about the "general" public.)
|
| [0]https://simcity.fandom.com/wiki/Microwave_Power_Plant
| LarryMullins wrote:
| Seems plausible, for millennials at least. SimCity 2000 was
| one of those games that seemed to be in every public school
| computer lab in the late 90s and early 00s. Tons of people
| played it, more than just the usual audience for
| management/business sims.
| DennisP wrote:
| Modern designs are a lot different than those monolithic '70s
| designs. Now it's a bunch of mass-produced small parts self-
| assembled in orbit, with a phased-array transmitter.
| Manufacturing's way cheaper that way, once you start scaling
| a bit. (See NASA's SPS-ALPHA project or the book _The Case
| for Space Solar Power_.)
|
| The other big change is the prospect of $50/kg to LEO with
| Starship. Falcon Heavy's advertised price is already down to
| $600/kg.
| pclmulqdq wrote:
| I wasn't a huge believer in this project when I was at Caltech,
| but I'm glad they stuck to it and are getting something off the
| ground. It's an interesting tradeoff of RF losses vs losses to
| solar power non-ideality. The theory looks great, but I do wonder
| if the theory can be met in practice.
| WalterBright wrote:
| If it works in Earth orbit, it will also work in lunar orbit
| where it can solve the most expensive barrier to a moon base -
| power.
|
| So, although it may be too expensive for Earth power, it can be
| very practical for moon power.
| aerophilic wrote:
| Love this concept... one issue however if I remember
| correctly is that it is pretty costly (fuel wise) to keep
| anything in lunar orbit. The issue is that the moon is very
| "lumpy" causing you to have to constantly correct your orbit.
| However maybe this is a non-issue if you are in a high enough
| orbit... but then you are trading how much power you can get
| to the surface.
| gpm wrote:
| There are a few "frozen orbits" that are stable:
| https://science.nasa.gov/science-news/science-at-
| nasa/2006/3...
| moffkalast wrote:
| Yeah and the LRO has been in one of them for 13 years
| now. It does restrict you quite a bit though.
|
| For Luna it doesn't make as much sense as it would for
| say Mars, since there's no atmosphere to reduce
| efficiency and no shortage of ground real estate. You can
| save a bit of propellant to not bring the panel assembly
| down, but you'll need fuel for orbital stationkeeping
| instead anyway.
| colineartheta wrote:
| If I recall, the current plans for the Artemis base is a
| small nuclear reactor.
| dghughes wrote:
| Wouldn't solar panels on the moon be easier? No atmosphere
| and on always being blasted with sunshine.
| elil17 wrote:
| In addition to what others have said, it takes more
| fuel/energy to land a payload on the moon than it does to
| orbit one.
| josh11b wrote:
| There is no place on the moon that isn't in shadow 14 days
| at a time.
| https://caseyhandmer.wordpress.com/2022/07/03/powering-
| the-l...
| TaylorAlexander wrote:
| Maybe use solar panels to split lunar ice water in to
| hydrogen and oxygen, then use that to run fuel cells in
| the dark periods.
| LarryMullins wrote:
| 14 days of lunar night would get quite cold. Maybe you
| could use the bases' water tanks as thermal batteries.
| Nomentatus wrote:
| Tall lunar pole towers: https://futurism.com/the-
| byte/harvard-super-tall-towers-powe...
|
| Maybe better: nuke the moon and reduce a few key crater
| rims, then use much shorter towers. Could be that a
| series of regular bombs might be more effective and less
| likely to "alarm the horses (general public.)"
| amelius wrote:
| Near the poles?
| Fordec wrote:
| Only works if your bases are at the poles. Which for some
| missions works, but it's a limitation if your project
| needs to be anywhere else.
| Nomentatus wrote:
| https://futurism.com/the-byte/harvard-super-tall-towers-
| powe...
|
| There's a famous-in-the-area ex-NASA blogger with good
| (not perfect) articles on the topic, but I can't Google
| and find him 'cause authoritative institutions now seems
| to trump and drown out mere experts on Google.
|
| Others here cite him:
| https://caseyhandmer.wordpress.com/2019/08/17/blog-
| series-co...
| JumpCrisscross wrote:
| > _Wouldn 't solar panels on the moon be easier?_
|
| Dust.
| nakedrobot2 wrote:
| there is no wind on the moon.
| LarryMullins wrote:
| There's still a bit of dust falling on the moon, kicked
| up by meteorite impacts and perhaps electrostatic
| effects. Probably not enough dust to cause issues though.
| JumpCrisscross wrote:
| > _there is no wind on the moon_
|
| There is near a Moon base, which is presumably where
| you'd need power.
| ben_w wrote:
| "Near" is a relative term; 10 km is a rounding error for
| resistive losses even in a mediocre cable at
| unspectacular voltages, even 1000 km isn't much loss for
| an HVDC cable, and it's economically reasonable to loop
| the moon with a 600O conductor if SpaceX's Starship price
| estimate works out.
| JumpCrisscross wrote:
| I was going to rebut with distance and maintenance, but
| it's a hell of a lot easier to go 10km over than 10km up.
| (I think?)
|
| > _it 's economically reasonable to loop the moon with a
| 600O conductor_
|
| Could you generate nontrivial power from the Moon's
| motion through the Earth's magnetic field?
| ben_w wrote:
| > Could you generate nontrivial power from the Moon's
| motion through the Earth's magnetic field?
|
| Not sure, but my gut feeling says no: the Moon is a very
| long way from the Earth relative to the Earth's size,
| therefore the magnetic field is likely to be fairly
| uniform around the Moon and so that can't extract much
| work.
|
| That said, one fun idea I've had is to just assume that
| the Dark Energy expansion of the universe is pushing the
| Moon away very slowly; 73 (km/s)/Mpc * distance to the
| moon [?] 9.5e-10 m/s, which is pretty close to the actual
| current Moon-Earth recession speed.
|
| Plugging that into the formula for far-field
| gravitational potential energy given the mass of Earth
| and the Moon, that's about 170 GW at the present time.
|
| (But don't go trying to crowd-fund a Dark Energy field
| reactor on my say-so: At my [rather limited] level of
| understanding, it looks like physicists haven't yet
| reached any sort of consensus as to whether or not Dark
| Energy might work like that).
| JumpCrisscross wrote:
| I'll shoot you the DEFCoin white paper.
| WJW wrote:
| My gut feeling says that it is not impossible but you
| would probably need many loops around the moon to
| generate a sufficient coil, making the whole thing cost
| prohibitive. You could probably dot some solar farms
| around the equator of the moon and loop them all up with
| a big cable for a fraction of the price.
| LarryMullins wrote:
| Laying ten thousand kilometers of cable to loop around
| the moon sounds like a huge undertaking, even if you've
| got a rocket that can bring the cable there.
|
| What would the cable layer look like? A huge robotic
| rover? Could you get all 10,000 km onto one spool, or
| deliver new spools to it?
| dirkc wrote:
| Two reasons I can think of
|
| 1. A moon day is 28 earth days, thus 14 days of darkness
|
| 2. Ice are in permanently shaded areas near the poles of
| the moon, it might be easier to setup satellites to beam
| down power rather than setting up in 2 locations
| sveme wrote:
| Why not use classical PV on the moon? Too much dust?
| dahfizz wrote:
| Moon nights last 14 days. Not an option with current
| battery tech.
| JumpCrisscross wrote:
| Does anyone have a recent list of power-constrained activities on
| satellites in LEO? That is, something you'd like to be able to do
| but can't because putting albatrosses of panels on low-orbiting
| birds makes them go down fast?
| LarryMullins wrote:
| The classic example is RORSAT, Radar Ocean Reconnaissance. The
| Soviet Union built a bunch with nuclear reactors because they
| needed a lot of power but were also to be in LEO so large solar
| panels would limit their lifespan.
|
| But I don't think powering a satellite from the ground makes
| much sense; you'd need ground stations around the world.
| JumpCrisscross wrote:
| > _RORSAT, Radar Ocean Reconnaissance_
|
| Radar was the only thing that came to my mind, too. (Didn't
| know about the project, though. Thanks!)
|
| Problem is earth observation, as a market, sucks. With low-
| latency optical imaging en route, I'm not sure what premium
| radar would command.
|
| > _don 't think powering a satellite from the ground makes
| much sense_
|
| Microwave power transmission through atmosphere is terrible,
| and we're nowhere close with laser. The idea would be large
| arrays in a high orbit beaming to lower-orbit birds. That's
| the only proximate case where space-based solar power makes
| sense: space to space. The only place where having the panels
| where you need power doesn't make sense is in the atmosphere.
| I just can't think of anything you'd want to do there that
| requires that much power.
| LarryMullins wrote:
| > _Problem is earth observation, as a market, sucks. With
| low-latency optical imaging en route, I 'm not sure what
| premium radar would command._
|
| One advantage of radar is that sometimes you can see
| through things that aren't transparent to visible light. I
| don't know if it's true, but I've heard that modern SAR
| sats can see through petroleum storage tanks and some
| warehouse roofs, so they can collect data which may be
| valuable to traders. These modern sort of radar satellites
| are apparently fine with solar power, but maybe they'd be
| even better with more power.
| tee_0 wrote:
| I walked the campus at cal tech a few days ago. It feels like a
| real college. Other colleges could be mistaken for luxury resorts
| or spas. They feel like a gimmick. But at cal everything looks
| normal. It looks like a place where people actually come to work
| and learn. It has a monastic quality in comparison. A place where
| people are truly preoccupied with the truth. It's the first
| university I've been to that felt like that. Besides maybe
| Stanford.
| laidoffamazon wrote:
| My state school was like that. It's just buildings. Most
| schools are like that!
| IshKebab wrote:
| Ah I was wondering how something like this could go ahead when
| it's pretty obviously a terrible idea to engineers.
|
| > SSPP got its start in 2011 after philanthropist Donald Bren,
| chairman of Irvine Company and a lifetime member of the Caltech
| Board of Trustees, learned about the potential for space-based
| solar energy manufacturing in an article in the magazine Popular
| Science. Intrigued by the potential for space solar power, Bren
| approached Caltech's then-president Jean-Lou Chameau to discuss
| the creation of a space-based solar power research project. In
| 2013, Bren and his wife, Brigitte Bren, a Caltech trustee, agreed
| to make the donation to fund the project. The first of the
| donations to Caltech (which will eventually exceed $100 million
| in support for the project and endowed professorships) was made
| that year through the Donald Bren Foundation, and the research
| began.
|
| "Ok nobody tell him it's a bad idea and we get like 50 PhDs and 5
| professors!"
| p1esk wrote:
| You forgot to explain why this is "pretty obviously a terrible
| idea".
| thisisbrians wrote:
| Some ideas about what makes it challenging:
|
| - A satellite will have to transmit power through the entire
| atmosphere from space, which will have substantial losses
| even in perfect conditions
|
| - A satellite constellation in orbit would need many ground
| stations to transmit power to from space
|
| - Weather will get in the way of transmission to the ground,
| just like it does with ordinary solar
|
| - The cost of getting a PV array into orbit is very expensive
| relative to the amount of power it can generate and transmit
| p1esk wrote:
| None of these seem like obvious show stoppers.
| JumpCrisscross wrote:
| > _satellite will have to transmit power through the entire
| atmosphere from space, which will have substantial losses
| even in perfect conditions_
|
| Balancing this is at least a half an order of magnitude
| difference in collection efficiency.
|
| > _Weather will get in the way of transmission to the
| ground, just like it does with ordinary solar_
|
| True. But there are extraterrestrial atmospheres where
| water vapor and ozone aren't a problem. (I've only seen
| this proposed with microwave.)
|
| > _cost of getting a PV array into orbit is very expensive
| relative to the amount of power it can generate and
| transmit_
|
| This is the killer. That said, this is a long-term research
| endeavour. If we contemplate such an array around the Moon
| or on Mars, or in a world with in-space resource extraction
| and manufacturing, the economics shift.
| wrycoder wrote:
| _> cost of getting a PV array into orbit is very
| expensive_
|
| Musk will find a way. Another stepping stone to Mars.
| SyzygistSix wrote:
| He's talked about the idea, how much the two aspects -
| solar power and space - are things that excite him, and
| how it just is not a viable idea.
| DennisP wrote:
| He made one comment, a decade ago, well before he started
| talking about $35/kg to orbit with Starship.
|
| In response to his famous question "what's the conversion
| rate," the answer is about 50%, according to the book
| _The Case for Space Solar Power_. That 's not bad
| considering a panel in geostationary collects five times
| as much energy in 24 hours as a panel on Earth.
| ben_w wrote:
| It would be great on Mars. Mars has planet-wide dust
| storms.
|
| But for Earth, even if it was free to put the PV in Earth
| orbit, the ground stations need to have an incredibly low
| total cost to make sense.
|
| I can't remember how low exactly.
| DennisP wrote:
| The ground stations are basically just antenna wire. For
| a large plant they would contribute just 0.7 cents/kWh to
| the total cost, according to the book _The Case for Space
| Solar Power_.
| feoren wrote:
| > half an order of magnitude
|
| Completely off-topic, but would "half an order of
| magnitude" be sqrt(10)? I've just never heard someone
| refer to a factor of ~3 as "half an order of magnitude".
| roelschroeven wrote:
| Sqrt(10) is approximately 3.162278, that's close enough
| to 3.
| [deleted]
| JumpCrisscross wrote:
| > _just never heard someone refer to a factor of ~3 as
| "half an order of magnitude"_
|
| Last time I looked, the estimates ranged from 270% to
| 50x. Seeing the latter, my brain went into astronomer
| mode and then I guess just ran with it.
| LarryMullins wrote:
| > _If we contemplate such an array around the Moon or on
| Mars, or in a world with in-space resource extraction and
| manufacturing, the economics shift._
|
| The economics of anything on Mars or the Moon amounts to
| _' try to convince a government to throw tons of money at
| you.'_ A technology which only makes sense in that
| economic context is very limited.
| JumpCrisscross wrote:
| > _technology which only makes sense in that economic
| context is very limited_
|
| If this were a start-up I'd be roundly criticising it.
| It's not. It's a research project. And each of its sub-
| projects--testing new PVs in space, a novel deployment
| mechanism, power transmission--has clear value outside a
| space-based solar context.
|
| As a focussing mechanism, SBSP is neat because each
| problem needing to be solved to make it economically
| viable is immediately valuable on the ground. (Save for
| power transmission. That's still niche.)
| LarryMullins wrote:
| > _Save for power transmission_
|
| Isn't that the entire point? Putting solar panels in
| space has been done regularly the 1950s.
| JumpCrisscross wrote:
| I meant that I don't see a near-term use terrestrial use
| case for better microwave power transmission.
| LarryMullins wrote:
| Maybe you could use microwave power transmission (from
| the ground) to power atmospheric pseudo-satellites, but
| practical applications seem dubious.
| ben_w wrote:
| Drones. Electric aircraft in general, recharging
| continuously in-flight.
|
| Might be ill-advised for a whole mass of reasons that I,
| as a software engineer, know naught of; but it would be a
| use case.
| IshKebab wrote:
| Even ignoring the power transmission challenges, putting
| stuff in orbit is _really really expensive_. Surely you knew
| that?
| DennisP wrote:
| For now. But if SpaceX succeeds in getting launch costs
| below $50/kg with Starship, space solar starts looking a
| lot more attractive.
|
| Advertised price on Falcon Heavy is already just $600/kg to
| LEO. A big part of that is the throwaway upper stage, which
| Starship eliminates.
| cratermoon wrote:
| https://dothemath.ucsd.edu/2012/03/space-based-solar-power/
| josh11b wrote:
| https://caseyhandmer.wordpress.com/2019/08/20/space-based-
| so...
| [deleted]
| ablatt89 wrote:
| Pretty funny how often when one brings up engineering
| challenges to solar, the challenges are ignored or handwaved.
| There's not even a back of the envelope calculation to prove
| the solution is scalable, maintainable, or cost effective the
| solution, it's all just feel good, "cool" factor, "saving the
| world" factor that's used to argue for investigation.
| alex_duf wrote:
| You mean solar in space specifically right?
|
| Because solar back on earth makes a lot of sense, whereas
| solar back in space to beam down on earth make no sense.
| ablatt89 wrote:
| Solar on earth makes sense in some contexts, but there's
| questions of how it's not scalable, clean up methods, local
| climate effects, is intermittent and causes the power grid
| instability. These are fair questions that should be looked
| at and solar on earth is not some solution to the problem
| of gas without tradeoffs, but these questions and concerns
| are usually ignored.
|
| https://www.nrel.gov/news/features/2020/renewables-rescue-
| st...
|
| These concerns are not really brought up by the media.
| IshKebab wrote:
| I don't think they're _ignored_ exactly. They 're just
| not really significant problems compared to the
| greenhouse emissions of gas or coal power.
|
| It's like how virtual keyboards on smartphones are not as
| good as a full physical keyboard (arguably) but nobody
| really talks about it anymore because the disadvantages
| of physical keyboards are so overwhelming that it doesn't
| matter.
| ablatt89 wrote:
| I don't think that comparison is fair at all. You're
| comparing concerns of a technology and how it scales, to
| how no one talks about physical keyboards and smart
| phones? That's not even remotely the same and is pretty
| dishonest to make that comparison.
|
| The problems of solar as a scalable renewable are very
| fair to talk about, considering that Africa and India
| NEED energy to grow their societies. The only solutions
| that scale are oil or nuclear. The idea you can just hand
| wave any concerns about renewables doesn't seem very
| rationale if you genuinely care about the problem.
| SyzygistSix wrote:
| >Because solar back on earth makes a lot of sense
|
| Where are you replying from?
| jmyeet wrote:
| I encourage you to watch The Future of Solar Power [1].
|
| I am firmly of the belief that solar power is humanity's future
| of energy production.
|
| Yes, beaming power to Earth is viable and could be economical.
| This pretty much solves the problem in variable power generation.
| I've seen estimates that a space-based power collector could
| generate about 6-8x what that same collector could on Earth (due
| to atmosphere, weather and day/night) so even with some power
| loss from beaming power to Earth, it's viable.
|
| But there's an even better fguture for this.
|
| The first is as the power source for space habitats. You
| literally just put them on the outside hull. These are incredibly
| efficient in creating living area per unit mass and ultimately
| would become a Dyson Swarm. I consider this inevitable.
|
| The second is you can do better than beaming power with orbital
| rings [2]. In short, you put a loop of conducting cables in
| orbit, run a current through them and float things on top with
| the magnetic field. The beauty of this is those things elevated
| on the ring are fixed to points on Earth. This means you don't
| need to speed up to Mach 30 to reach orbital speeds.
|
| If you have an orbital ring, you can run cables down from space
| directly to the ground.
|
| [1]: https://www.youtube.com/watch?v=W-TISSvR0L4
|
| [2]: https://www.youtube.com/watch?v=LMbI6sk-62E
| notum wrote:
| Cloud cover doesn't affect microwaves?
| JumpCrisscross wrote:
| > _Cloud cover doesn 't affect microwaves?_
|
| It does. (Ozone and water absorb microwaves. This is how your
| microwave oven works.)
| Nomentatus wrote:
| Microwaves are highly tuned to the particular frequency that
| causes water molecules to resonate. But this is just one
| microwave frequency. You don't have to use that one.
|
| https://www.gi.alaska.edu/news/using-microwaves-see-
| through-...
| notum wrote:
| To expand on my semi-sarcasm with a proper question: so
| there's a microwave frequency that is completely unaffected
| by atmospherics? In which water, ozone, the rest of the gas
| mixure and particulates are mostly transparent?
|
| What frequency spectrum is that? And for bonus points: can
| this project fry commercial planes?
| Nomentatus wrote:
| First sentence: not what was said. But note that
| microwave towers have been in use for mission-critical
| long-range all-weather point-to-point communication on
| earth for many, many decades. My late father helped
| design some of them.
|
| What would the minimum power loss be for thick
| cloud/hurricane? Dunno.
| zaroth wrote:
| Those microwave towers are transmitting some number of
| milliwatts of power though, with super high gain
| antennas.
|
| Not kilowatts.
| notum wrote:
| As synonymous comms and power delivery may look, they are
| a different ball game.
|
| This also seems to be the last nail in the coffin for
| terrestrial radio astronomy, now that you mention it.
| ben_w wrote:
| > Microwaves are highly tuned to the particular frequency
| that causes water molecules to resonate.
|
| That's an urban legend. If it was true, they'd be great
| rather than "meh" at melting ice, and (I appreciate most
| don't do this anyway) we wouldn't be able use domestic
| ovens for glass-working or melting alumina to make
| synthetic sapphires and rubies.
|
| * https://youtu.be/XojnG2IFfTo
|
| * https://youtu.be/xwEQZw3KPWg
|
| * https://youtu.be/ybcdRQmQcHQ
| Nomentatus wrote:
| Good points, but careful of the logic; yes there's a lot
| of energy being produced and plenty of harmonics etc.
| None of which says that every material heats equally
| well, with no passthrough, or that microwave ovens with
| different frequencies wouldn't be more efficient for
| other specific materials.
|
| If a material is dense enough (metal being the prime
| example) it'll block. I've nowhere argued that you could
| send microwave power through solid walls - whether brick
| or sapphire economically.
| JumpCrisscross wrote:
| > _this is just one microwave frequency. You don 't have to
| use that one_
|
| The atmosphere is almost transparent to long-wavelength
| microwave [1]. The tradeoff is in power density.
|
| [1] https://earthobservatory.nasa.gov/features/RemoteSensin
| g/rem...
| nickpinkston wrote:
| I was more hoping for the arcology building from SimCity, not the
| space solar plant, but pretty cool.
| cmdialog wrote:
| When is someone going to launch something to clean up all the
| tech demos and space junk?
| waihtis wrote:
| when a big publicity incident caused by space junk happens
| throwaway4aday wrote:
| It's in LEO, the atmosphere will bring it down.
| pythonguython wrote:
| Yep. Part of launching is making a deorbit plan (if
| possible). That satellite will come down, and they already
| know when that will happen.
| Grim-444 wrote:
| I'm pretty sure there's already FCC rules requiring deorbit of
| satellites within a certain number of years of their mission
| completion.
|
| [Edit] https://www.fcc.gov/document/fcc-adopts-new-5-year-rule-
| deor...
| simonebrunozzi wrote:
| I'm super ignorant on physics and whatnot; but wouldn't it make
| more sense to use airships covered with solar panels at 5k-6k
| meter altitude? Thin solar is now a thing, and I'm quite sure
| that there would be a viable way to engineer an airship in such a
| way. One could even use graphene aerogel instead of helium or
| hydrogen as the lighter-than-air filler.
|
| Is this a really dumb idea? Any of you with a more relevant
| background could tell me where this could be so wrong?
| LarryMullins wrote:
| > _5k-6k meter altitude_
|
| That's not high enough to put you above bad weather (airliners
| fly higher, and they divert around storms.) Bad weather is bad
| news for airships and historically destroyed about as many as
| hydrogen fires. You'd need to bring your airships down into
| hangers when the weather got bad.
|
| Also, wouldn't the graphene aerogel be filled with air and be
| heavier than air? Aerogel doesn't just float away. Unless you
| mean for these to be vacuum airships, but those seem very far
| fetched.
| dahfizz wrote:
| Is graphene aerogel lighter than air? I thought it _was_ mostly
| air, which is why its so light.
| DennisP wrote:
| Biggest advantage of solar in geostationary is that you get
| power 24/7, so you don't need a lot of storage. You're not in
| shadow at all except for a little bit around the equinoxes.
| Total uptime is 99.5%.
| idiotsecant wrote:
| Seems like some of the bad parts of terrestrial solar (fighting
| atmospheric conditions, wind loading, etc) without the good
| parts of orbital solar (once you're in orbit, staying there is
| relatively easy and you have very little in the way of
| mechanical stresses for your solar array, so you can make it
| really huge). I might not be thinking about it hard enough.
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