[HN Gopher] Space Solar Power Demonstrator ends first in-space m...
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Space Solar Power Demonstrator ends first in-space mission
Author : geox
Score : 29 points
Date : 2024-01-16 21:29 UTC (1 hours ago)
(HTM) web link (www.caltech.edu)
(TXT) w3m dump (www.caltech.edu)
| superkuh wrote:
| No it didn't. Transmitting power via microwave radio signal
| through a vacuum is no new thing. That's all they did here:
| transmit power a meter or two across the inside of the spacecraft
| while it was in space. They did not even attempt to do
| transmission of power to ground for obvious reasons.
|
| At 9.84 GHz their ~meter scale aperture from 400km LEO orbit to
| the biggest NASA dish in existence (that could track LEO) would
| have a path loss of 76 dB. That means something like (being
| generous) 0.0000000001% of the power would make it. Plenty for
| carrying information but useless for beaming power.
|
| Space solar power requires coherent emitting apertures on the
| order of a handful of kilometers to be feasible (from LEO). We
| can't build kilometer scale anything in LEO. End of story. Once
| that changes we can think about space solar power.
| jahnu wrote:
| > No it didn't.
|
| I think you are reading something in the headline that isn't
| there. They ended their first space based mission which was to
| test various things. It wasn't to beam power back to Earth. The
| details in the article are actually interesting.
| superkuh wrote:
| I read the article. It's glaringly obvious that the goal is
| space solar power to earth.
|
| >"Solar power beamed from space at commercial rates, lighting
| the globe, is still a future prospect. But this critical
| mission demonstrated that it should be an achievable future,"
| says Caltech President Thomas F. Rosenbaum, the Sonja and
| William Davidow Presidential Chair and professor of physics.
|
| This mission did nothing to show that was achievable. The
| hard part isn't the vacuum. It's the distance which requires,
| because of physics, a large coherent emitting aperture. And
| the larger your aperture the harder it is to point. If they
| really wanted to make progress towards this they'd be
| building a km-scale coherent phased array for power
| transmission here on earth.
|
| The EISCAT scattering radars in the artic circle are much
| closer to proving feasibility for space based solar power
| than this is.
| dekhn wrote:
| You're being pedantic, and incorrectly pedantic.
|
| Complaining about a scientist saying "it's a future
| prosect... that should be an achievable future" is just
| silly.
|
| Look, I get it. I see a PR and I get angry at the
| implications. But it's just not worth overinterpreting this
| PR as justifying future research into beamed power
| delivery.
|
| My guess would be this has space-based military
| applications they're not discussing but that's purely
| speculation based on what we believe the military space
| community is already exploring.
| dekhn wrote:
| There's nothing in the press release to suggest that his
| specific mission was intended to demonstrate a working,
| economic delivery of power to earth. The article is clear about
| this, and the title is accurate.
|
| Whether it makes any sense to continue this line of research is
| an open question; they seem to be very far from having
| something that would produce useful power, with a long line of
| technical challenges facing them.
| mattashii wrote:
| Many modern earth imaging satellites use something called
| "synthetic aperture radar" where the movement of the satellite
| is used to increase the aperture for the radar larger than the
| satellite's own dimensions.
|
| Could a similar mechanism be used as well for space to earth
| energy transfer, or is that unrealistic at the orbital speeds
| of LEO?
| superkuh wrote:
| Synthetic apertures are not applicable to power transmission.
| That's just information processing. The velocity at which
| you're traveling doesn't matter. It can be done from plane.
| Or balloon. Or a walking human. You just have to transmit and
| receive from spots some distance apart multiple times (in a
| smaller timescale than your target is moving).
| worldsayshi wrote:
| Space based solar or fusion power - which one will work
| commercially first?
| IshKebab wrote:
| Fusion obviously. It only takes a simple back of the envelope
| calculation to show that space based power makes no sense even
| in theory.
|
| Fusion on the other hand makes total sense if you can do it.
| It's just a really really really hard engineering problem.
|
| Space based power belongs in the same category as solar
| roadways, energy harvesting speed bumps, solar windows, etc.
| Clearly if you want to scam investors an energy project is the
| way to go.
| hutzlibu wrote:
| "It only takes a simple back of the envelope calculation to
| show that space based power makes no sense even in theory."
|
| That would be my gut feeling, but what simple calculation
| would you use to disproof it?
|
| Fusion is currently not working at all - but we can transmit
| power (with big losses over that distance) via laser etc. But
| since space is expensive, I just see no way to make this work
| economically.
| practicemaths wrote:
| People were saying the same thing about terrestrial solar
| for decades.
|
| Both fundamentally are engineering problems now.
|
| Also considering that there has been a lot of investment in
| space launch vehicles of late the cost to lift things into
| orbit are lowering.
|
| Technology takes a while to develop and mature with
| applications for this beyond just beaming power to Earth.
| hutzlibu wrote:
| "Also considering that there has been a lot of investment
| in space launch vehicles of late the cost to lift things
| into orbit are lowering."
|
| Yes, but the cost of installing solar panels on the
| ground are astronomically cheaper than anything you can
| do in space and I do not see the gap closing in the near
| future, even with breakthroughs. Rather the contrary, we
| still have lots of cheap unused land (deserts). And solar
| panels are getting cheaper every day. Having a space
| based laser/power beam sounds cool - but complicated and
| expensive.
| practicemaths wrote:
| The applications for this are well beyond Earth.
|
| Additionally there was a lot more useful testing of
| various related aspects in this beyond just beaming power
| to Earth per the article.
| 0cf8612b2e1e wrote:
| I think the biggest problem is that the ground based
| receiving array is going to be so large you could have just
| installed solar panels in the same location. 24 hour power
| generation is nice, but the economics of batteries + ground
| based solar seems more likely to triumph.
|
| Edit: If you assume a ground based array has a 20%
| utilization factor, the space based panels + receivers can
| only be 5x the cost of the standard solar installation.
| Which requires ~free space launches, plus probably other
| technology we do not currently possess.
| epistasis wrote:
| > Fusion on the other hand makes total sense if you can do
| it. It's just a really really really hard engineering
| problem.
|
| You could also say that space based solar makes total sense
| "if you can do it, it's just a really hard engineering
| problem"
|
| For fusion, the equivalent envelope calculation is the cost
| of a large thermal electricity generation installation, where
| the heat source is, say, half the cost of fission or even a
| tenth the cost of fission. The floor of fusion's end cost is
| that thermodynamic conversion, if the promos of fusion is
| super cheap heat energy. And when you start calculating the
| cost of 2GW of turbines plus 2GW of cooling towers, one might
| conclude that there's only a decade or two left before solar
| and wind and storage makes thermal electricity generation
| obsolete. Thermal electricity generation equipment isn't
| getting any cheaper, but the competition is getting cheaper
| exponentially.
|
| I would say that fusion is prettt close to a scam as a power
| source. There may be some cool physics and should be pursued
| for those reasons. But the idea of fusion as any sort of
| economical source of energy, when it has all the
| radioactivity problems of fission, massive scale challenges,
| and no reason to think that it will ever be anything except
| massive construction project, is just wishful sci fi
| thinking. I know it's not a popular opinion here, but "solar
| roads for sci fi fans" really is the shortest possible
| description of fusion power I can think of.
| jacoblambda wrote:
| > You could also say that space based solar makes total
| sense "if you can do it, it's just a really hard
| engineering problem"
|
| The thing is that while they are both really hard
| engineering problems, space solar (which includes energy
| transmission via lasers) is also a massive ongoing
| logistics and coordination problem.
|
| Solar power without wireless transmission makes a lot of
| sense the closer you get to the sun and in the inner solar
| system it almost certainly makes more sense than fusion but
| once you get to the asteroid belt or further out, inverse
| square law would suggest that it quickly becomes
| infeasible.
| hutzlibu wrote:
| "solar roads for sci fi fans"
|
| Solar roads are expensive and worked out economocially
| nowhere, where they were build. Unless you mean roads that
| have roofs of solar panels - that is a sound concept,
| because you can have standard cheap panels and replace them
| at will, but is not what is generally understood with solar
| roads.
|
| Also about fusion:
|
| "when it has all the radioactivity problems of fission"
|
| Not at all the same. What exactly are you referring to?
| Fission with heavy isotopes has radioactivity by design -
| but Fusion not really. There is some radiation with some
| designs, but the basic idea of fusing hydrogen into helium
| works without radioactivity.
|
| "massive scale challenges"
|
| And where exactly are they? Once a small reactor runs, what
| is the problem to build a big one?
|
| "and no reason to think that it will ever be anything
| except massive construction project"
|
| Because fusion bombs work since 70 years. And fusion in
| labs are not hard either. We can do fusion - we just cannot
| do it in a controlled way yet. But recent records with
| controlling hot plasma indicate that there is real
| progress. So (allmost) no one is currently betting that we
| will soon have fusion power, but at some point we will, if
| we keep on working.
| WJW wrote:
| Trick question! Space based solar derives all its energy from
| fusion anyway.
| londons_explore wrote:
| So if this is in LEO... It orbits the whole earth... And most of
| the time is over oceans where there is nobody to use any beamed
| power or in darkness where it cant generate power.
|
| Given that, can it ever hope to work out cheaper than just
| putting solar panels on the ground?
| gwbas1c wrote:
| It's an experiment to learn about what kinds of panels work
| best, and about beaming power in general.
|
| New technology, especially when it comes out of a lab in an
| academic setting, is never commercially viable. That often
| takes years of refining based on lessons from the lab, and from
| "real" deployments that aren't profitable.
| londons_explore wrote:
| Someone must see a path to being profitable one day or they
| wouldn't be funding research into it...
| WJW wrote:
| It's a demonstrator, trying to verify that the technology can
| work at all. The real version would be sent out to an orbit
| where there is always a direct path to the sun, but sending out
| spacecraft that far is much more expensive than just shooting
| them up to LEO.
| londons_explore wrote:
| But at those higher orbits, the size of the antenna necessary
| to get sufficient directionality gets _waaaaaay_ bigger
| right?
| WJW wrote:
| There's lots of space up there though.
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