Space Based Solar Power 10 Watt Demos in Space Now and Beaming and Other Demos Now to 2023

The US military tested a pizza box sized solar power module – Photovoltaic Radiofrequency Antenna Module (PRAM) in space. It was first launched in May 2020, attached to the Pentagon’s X-37B unmanned drone.

Orbital Demonstrations for Large-Scale Deployable SPS

The Air Force Research Laboratory (AFRL) is executing a major demonstration project with the goal of beaming power collected in space to expeditionary forces on Earth. The motivation for this capability is clear: assured energy supply with reduced vulnerabilities and lower-cost logistics. The AFRL project created to achieve this capability is Space Solar Power Incremental Demonstrations and Research (SSPIDR). SSPIDR is methodically pursuing rapid, demonstration-driven activities with increasing performance and integration level to reduce risk for an operational space solar power system.

SSPIDR has two major thrust areas:
(1) incremental demonstrations and
(2) developing critical technology elements (CTEs).

Three initial in-orbit prototype demonstrations are being developed in Phase I to advance the TRL of the needed component technologies to enable an operational space solar power system.

(1) Arachne,
(2) SPINDLE, and

Arachne will be the world’s first space-to-ground power beaming demonstration of a solarto-RF modular panel with in-situ surface-shape measurement to optimize beam formation. The solar-to-RF panel technology is designed to scale to very large apertures and to support high volume, low-cost manufacturing. Arachne is planned to fly in 2023. SPINDLE will test on-orbit structural deployment of a sub-scale version of the operational system. SPINDLE is designed to test deployment kinematics and deployed structural dynamics. Finally, SPIRRAL will test thermal management approaches to ensure a long-lasting, high-performance system. The SPIRRAL experiment is planned to launch in 2023 via Alpha Space’s MISS-E platform for rendezvous with the International Space Station.


The Photovoltaic Radiofrequency Antenna Module (PRAM), 12×12-inch panel, is capable of producing about 10 watts of energy for transmission.

IEEE Journal of Microwaves – Microwave and Millimeter Wave
Power Beaming

Abstract – Power beaming is the efficient point-to-point transfer of electrical energy across free space by a directive electromagnetic beam. This paper clarifies the basic principles of power beaming in simple terms, and proposes a benchmarking methodology for improving the comparative assessment of power beaming systems and technology. An in-depth historical overview tracing the worldwide progress in microwave and millimeter wave (mmWave) experimental demonstrations over the past 60 years shows clear evidence of a significant increase in activity during the last 5 years. In addition, a review of progress in scalable rectenna arrays for the reception of microwave power beaming shows sufficient maturity for new research to initiate on the ruggedization, productization, and system integration aspects of the technology. A review of regulatory issues including spectrum management and safety indicates the need for additional technical solutions and international coordination.

Breaking results reported in this paper include
1) data from the first in-orbit flight test of a solar-to-RF “sandwich module”,
2) the construction of multiple US in-orbit demonstrations, planned for 2023 launch, that will demonstrate key technologies for space-based solar power, and
3) a 100-kW mmWave power beaming transmitter demonstrating inherent human life safety.

Increased Areal Absorption per Diode

In 2018, the University of Waterloo and Prince Sattam University collaborated on ways to increase the absorption efficiency per unit area to near unity in order to channel more RF to the rectifying diodes. Using detailed Floquet analysis, they designed the 3.4 GHz energy harvesting rectenna array. This array used asymmetric dipoles covered by a high-permittivity TMM-10i superstrate to increase the incident power delivered to the diodes. An overall array RF-to-DC conversion efficiency of 76% was obtained experimentally, which the authors claim is the highest ever recorded for an energy harvesting surface.

Broad Bandwidth, MMWAVE Operation

In 2019, Shanghai University researchers developed a novel 35 GHz millimeter-wave rectenna designed for broadband performance. The array was
composed of 16 subarrays. Each subarray had a 2 × 2 array of slot coupled patch antennas backed by substrate integrated waveguide (SIW) cavities and a single rectifier. The antennas worked well from 31 to 40 GHz. Each 2 × 2 rectenna subarray had an RF-to-DC conversion efficiency of 51% when 13 dBm was incident upon a 550 load.

Progress and creativity in rectenna array technologies shows sufficient maturity for new work to begin productization of the technology for low cost, environmental resiliency, and compatibility with real-world power systems in support of future large-scale infrastructure and other real world deployments.

Caltech has active development of many aspects of space based solar power. They are advancing lightweight structures and are progressing to inspace demonstrations. Nextbigfuture will have separate articles covering their work and the recent 2021 SSSP conference.

SOURCES – USNRL, Caltech, IEEE microwave journal
Written by Brian Wang,

105 thoughts on “Space Based Solar Power 10 Watt Demos in Space Now and Beaming and Other Demos Now to 2023”

  1. Actually, I insist on a system that will be expected reasonably to supply more than all of Earth's current energy needs. Otherwise, I will talk about one that does, such as LSP. The fact that Earth has never done what LSP clearly can by merely doing more of the starting process, is a testament to the fact that the Earth's surface is not the right place for an expanding tech civilization. "by 2050 10 billion prosperous people will need ≥ 20 TWe". The minimum bid.

  2. Thanx! I got the connection backwards, did you hear about the boarding house that blew up? Roomers are flying!

  3. "There will be a few months before the Space Solar is totally replacing the energy production of Earth."

    You know, if you insist on starting with a system capable of supplying all of Earth's energy needs, it's never going to happen. No technology on Earth was ever adopted in that fashion.

  4. We are dealing with public opinion here. Like the stock prices and things I have no competence in. Think of the dire circumstance if light pollution were as big a problem as the power sat death ray? Now, I really hope Musk can do this for his sats, both as an amateur astronomer and as a proposer of objects in Space, but I would not be at all cavalier about it. Musk seemed totally unaware of the possibility. Now, GEO space junk and *crowding* do seem to preclude much more than starter Space Solar, but my starter kit is bigger than most proposals ever contemplate.

  5. "I figure you start out with LEO demonstrations of the beaming technology, go to GEO satellites for the initial rollout, and then once the market is proven, go to the Lagrange points and lunar surface." This is exactly the sequence of physical things to do, altho I would first start with Earth to Earth to military bases, as you mention, only simple redirectors launched. But I would *sell* the big system, and use these steps as tests rather than market proofs. The market is for a solution to climate concerns, no matter the details of the concern. This transcends the normal profit concern! People are talking of spending $Ts on CO2 extraction that takes vast (I hope Space Solar) energy and makes $0 profit. My nightmare scenario is that Carbon fee is used to do Criswell LSP and gov ends up with all the profit.

  6. "Once you had power satellites at the right Lagrange points, there's no need for it anymore, because everywhere is either in view of one of the satellites, or a transmission line away from someplace in view." There will be a few months before the Space Solar is totally replacing the energy production of Earth. The rectennae work for all, and are the main expense, so Earth to Earth is not a separate system. Think of desert solar. Intermittency and load variability. "power lines are an existing and viable solution for that" so, we don't need nukes? Your statement makes no sense to me. Also, if you are building a power line, you are doing a big project, and could better build H pipe, or use an existing gas pipe, better than anything else for efficiency of movement, and storage too. Each house should have an H powered micro grid, which hook together in larger sharing networks to keep everybody happy. The *current* power is from Earth or Space solar, wind, tide, all power beam balanced, but still as locally used as possible. Trim and big storage H, at all scales of the collaborative grid. The grid is a convenience, not the main source. And what some idiot does in some other place won't leave you "freezing in the dark" as the old windfall tax stickers said, when the whole grid fries.

  7. Light pollution is easily dealt with merely by properly orienting any specular surfaces, and judicious use of anti-reflective coatings. It's just another design constraint, really. Musk is designing the Starlink satellites to minimize it, already.

  8. "I don't see much use for beaming power around on Earth." Whenever you read a nuke article, a main reason for nukes is that they are *not* intermittent, which is *the* problem with renewables. So, whatever reason there is for nukes, use that reason for power beaming, and H pipelines, either of which, let alone both together, can solve intermittency and load variability. Wires cannot change path (power beams switch path electronically and fastly), have to either be built to go everywhere and carry max possible load at all times, or they don't solve intermittency. They don't, and can't, esp over the hilariously short distances we call *long* on this tiny planet. Then, we throw in some talk of Space Solar, now that there are some rectennae to test with. I have two images here: a nuke power beaming energy, and a battery EV driver waiting for a charge from an H fuel cell powered micro grid.

  9. If conduction lines are so good, why are power plants near cities, and stuff to burn hauled in? Criswell sez to power beam the energy after being produced where the stuff to burn is, and then use the captured CO2 to inject as filler in the wells. Touting grid is making the same mistake as Biden. A 60 Hz piece of metal as your main source of power is spooky. I know from direct recent experience. H or power beam supported micro grids, where the power can come from somewhere else far away, are superior. You cannot re arrange conduction lines! The super grid being proposed is idiotic, just asking for the greatest possible disaster when the next big flare hits.

  10. He replied to a spurious claim that Mankins' power beam demo was a failure, when it was a record setting success. Years ago I heard he had gone into Scientology, but I am not making that claim!

  11. We certainly agree on the basic facts. My outlook is that people are *vastly* familiar with GEO system, 99% unaware that it could be any farther out, 99.9% unaware it possibly could be better farther out, and 99.99% unaware of LSP. Yet the practical message of GEO is small, get started size, while LSP/L5 is proudly ready to expand from word go. If we don't show a 20 TWe (at least) system at the very first contact, most new people see Space Solar as just another Space toy. Or worse, a concern you have downplayed, something to fight as light pollution. Our only selling hope seems to be global weirding as a spur, given the 40 years wasted on getting started. And that means big and fast Space Solar.

  12. I'm not actually proposing such a system, (I actually like your Lagrange proposal.) I'm just pointing out that it's hardly impossible.

    Since Criswell actually involves the cells being in shadow much of the time, because there's this Moon between them and the Sun, a hypothetical GEO ring isn't less feasible. It would actually get higher usage out of the cells even if they weren't tracking.

    (The cells don't have to track, all that actually needs to track are thin film mirrors reflecting the light onto them.)

    To be clear, I advocate GEO SPS as a introductory approach to prove out space solar power, not as a final solution to energy supply. It is, as I say, the minimum viable product, not the best product.

  13. 'If humanity is a successful species, we will expand to fill all available niches, because that's just what evolutionarilly successful species do.'
    Seventy percent of the area of this planet is ocean, and humans have been crossing it for at least 50,000 years ( or there'd be no native Australians.) Yet nobody is living there. I know people who've grown up on yachts, but most of the time is spent in port. The infrastructure you'd need to survive permanently on the ocean is a minute fraction of what you'd need in space, but it still hasn't been done. Maybe people would rather live 'normal' lives than occupy some niche that, while huge, is just not that attractive.

  14. Well Brett, not saying Tony Seba is correct, but his idea is to compare actual production curves from different regions and then add batteries to the simulation and see what happens.

    He claims that because both solar and wind will be so cheap, you could easily install a multiple more than what you need at peak power. Say, 10 times more. So then you multiply your curve with a factor of 10, which makes the "floor" of the "valleys" 10 times higher. And the lowest "floor" may be on par with the actual demand of the region.

    If you do that, you only have to add batteries to store a few days worth of power, according to Tony Seba.

    I cannot vouch for his calculations being correct – his numbers on price and electricity production could be "off" – but the approach is correct in principle. And if his numbers are correct, then you would compensate for the variability by installing "more" than what you nominally need.

  15. Not sure that is correct.

    As a matter of fact, I'm pretty sure it's not. It's easy to introduce a fixed phase shift that is equal for all emitters. But that cannot change the direction of the beam. Otherwise, a constant phase shift of the beacon wave would also redirect the beam, and that would obviously not happen. The "absolute" phase of the beacon has no effect on the power beam direction, only the relative phases of the emitters…

    So you would need the exact same requirements on your (variable) offset compared to not having a beacon wave at all. That is, a fraction of a fraction of a degrees precise, individual, phase shifts for each emitter. Now that is difficult, very difficult….

  16. Good point. High altitude for drones and for the rest the military would be happy with anything in combat zones. Though mind you, you need a really big satellite to get any decent power density at the ground… Think 1 GW of power beaming that would allow everyone within 1 km2 to collect about 1 kW per m2. That's loosing about, say, 99.95% of the incident power, since they will only have 500 m2 of rectennas in the field.

    So they would be expending 1 GW to get 500 kW. Seems a bit of a stretch…

  17. Great! Seems like the history of these things is that you need small, modular things that don't go along for the ride if not actually needed. Re connecting and power beaming are needed to overcome the nasty rocket equation. Who thought that one up, anyway?

  18. The NASA DRM mission variant I saw that suggested power beaming to a surface hab combo PV+rectenna rollable panel proposed using RF beaming, not laser. Though characterizing how much a dust storm impedes the minimal life support power output of the surface hab PV, or interfering with RF beam power, is a good point. Choosing a beam frequency that allows a tight-ish spot that can avoid airborne dust interference would be key.

  19. Yes but you save the cost of batteries, which is a *lot* if you're trying to get through windless nights.

    Based on cost projections in the book *The Case for Space Solar Power*, plugging in Starship launch costs, I got a total cost of 4 cents/kWh, which is pretty good for zero-carbon power on demand without storage.

  20. Reputedly Newton, besides being a genius, was also an a hole, so not sure if I'd want a million of him. It only took one to write Principia. Von Neumann came from country of about six million – Hungary – whose much smaller Jewish minority produced a slew of geniuses at the same era. We don't need to put a trillion people into space, just a few into ghettoes. ( Just joking.)

  21. Yup, but that's a paying customer's prerogative.

    Customers can hate your company and not buy anything from you, hurting their own self interests even.

  22. Airbus or Boeing might use dhl instead?

    Wasn't it oneweb's CEO who hated SpaceX, I assume because of Starlink, went with Soyuz for their last launch of 36 satellites 2 weeks ago.

  23. I think you would have to undertake dismantling planets to build cylinders before you have enough to worry about gross leakage loss on million year time scales. Assuming dismantling earth is off limits, phosphorus availability might limit the number of cylinders from reaching ridiculous numbers.

  24. What does Fedex care if the owners of Airbus or Boeing like or hate the package delivery services?

    His rockets are planned to be rented for private usage, any usage, not just those Elon Musk likes.

  25. Whatever population finds a way to retain its will to reproduce in the face of social factors discouraging it will pretty much automatically come to dominate over a few generations

    Yes, and we may not like the results of it.

    If what we call "intelligence" becomes an evolutionary negative trait, then the foolish will inherit the Earth.

    And if they are foolish enough, probably just that and nothing else.

  26. Oh, did not mean him directly it was a metaphor. A driven engineer with a head for business who, through massive drive and innovative thinking does something others view as highly unlikely and changes the world for the better.

  27. Sounds like you are abandoning solar tracking? This is a plan I have not seen exactly. Have you combined it with the RF transparent cells?

  28. You state the obvious. Free markets also take investors, not just customers. That is sort of where we are now. Free market theory, and libertarian thought in general, rely on such abhorrent things as *self interest* to operate, as you are referring to, customer choice. Now, a big socialist gov push in response to climate concerns might happen too, but ignore that stuff for now. From the beginning, this market mechanism has had an important phrase: "enlightened self interest". Stupid self interest is not recommended, for example. Evil is considered fundamentally stupid, too. So to get investor/customers into this, they should be enlightened or at least informed. That is my purpose, not to raise money right now.

  29. If Tony Seba is right, then we will build enough wind farms that they will remove enough energy from wind systems to cause inland areas to become drier; the Greens will suddenly change their mind on wind energy, then.

  30. OK, the part of Earth losing some atmosphere every year was well known, I think.

    I rather wondered if someone had actually calculated how many volatile elements an O'Neill habitat based civilization would lose, with how many equivalent Earth land areas and up to where & when this civilization could live without worrying about losing too many volatiles and/or having to emigrate.

  31. "extreme problems getting together enough capital" I have been demanding an international emergency effort to enact O'Neill and Criswell solutions to Earth problems for decades, particularly global weirding/warming/heating. Or anywhere that someone who wants to participate in this gold rush known as opening Space can get it together. Musk and Bezos should join forces!

  32. In free markets, the one paying the piper calls the tune.

    If you're serious about the growth of this until it can reach everyone, you'd acknowledge that it will require creating and growing a market first, with customers being the ones paying the piper and the melody.

  33. Dust storms are largely a problem because Mars surface solar panels need such a large area, that can get covered with dust. Laser power beaming would have less of a problem with dust storms, because the panels could be much smaller, and more easily cleaned.

    But microwave beaming would deal with it even better.

  34. There is no need, as the radars have to big enuf to work at L5 anyway, and the light pollution is 100 times as bright in GEO. Space junk. No such probs at all w/ LSP.

  35. I'm working on some simple O'Neill and Criswell concepts, and until more people have any clue of the plans, I'll let others worry about how to do the demos.

  36. Some see it as a numbers game, in order to produce a million people like Newton & von Neumann, you will need a population size in the 10s of trillions.

    If you keep the population well educated, you will not have to worry about this eventuality for the foreseeable future. Unless the hoped for breakthrough in ML occurs in the coming decades, no adult current alive will live to see an O'Neill cylinder, they might get to see a basic rotating vacation station.

  37. Unacceptable to you above, where you complain about lack of redundancy! Think positive! edit: also unacceptable to most users. Don't design a system like that, even if a few will use it for a little while.

  38. Earth loses about 50,000 tons of air per year, blown away by the solar wind.

    Pressurized bottles leak. Want to bet that even competently run O'Neill colonies, with an aggregate surface area equal to earth's, wouldn't lose mass faster than that?

    Now build out to a thousand times the surface area of Earth, or ten thousand times. Over geological periods, you could run out of volatiles in the inner solar system. I suppose you could import them from the gas giants.

  39. "Though I do have concern about leakage rates;"

    People cant be concern with factors with serious negative consequences affecting the present to the near term, but you expect them to be concerned about something that isn't happening in the near term and will not potentially yield serious consequences for a million years. This is the kind of problem you try to solve when all the others have been sorted.

  40. Unacceptable? To who exactly? The producer and consumer of the power is almost guaranteed to be the same entity. The world is under no obligation to conform itself to anyone's favorite dreams for space.

  41. Chemical rockets are most likely a temporary phase in our development.

    Volatile elements leakage can be reduced drastically by using other propulsion methods.

    Mostly mechanical ones like space elevators and space tethers can be used to great effect. Electromagnetic ones like mass drivers too. An O'Neill habitats civilization can mostly use mass rails to move cargo and people around, with rockets required only for small course corrections.

    Other sources of volatile leakage will be from fusion, which is energy dense but it will be extensively used for rotating habitats and for moving big masses around. And such a civilization will indeed require a lot of mass movements.

    The Sun's energy and light's thrust can be used as well, if you are well developed and patient. Such a civilization will most likely become mostly solar energy based, when the years of feverish growth pass.

    But any wise O'Neill civilization will eventually look for a mass diaspora into the Oort cloud and beyond, to ensure they never run out of anything.

    All of this, humanity will probably do in a few millennia, thus way before they have to worry about running out of volatiles.

  42. If your life depended on that power, and it probably will, that would make for a suicidal setup. Even with a redirection system, until there is enough redundancy, any solar based solution for well beyond cislunar would be too fragile a setup for a sizeable group to depend on.

    Those with a firmer grip on the realities space recognize systems like KRUSTY is critical for anything beyond going to pickup some more rocks.

  43. 200TW of collecting area would be 10^12 square meters, approximately.

    GEO has a circumference of about 265,000Km.

    You'd be talking about a band of solar collectors maybe 10km wide, accounting for cosine losses and shadowing. What's clearly impossible about that, if we're taking Criswell seriously?

  44. Dust storms are a problem for laser power beaming to the martian surface. However for providing power at night to the surface of an airless body it will be fine.

  45. The navy's solution, user their existing hardware to do nuclear-to-liquid-fuels on the high seas.


  46. True, but power lines are an existing and viable solution for that, and they don't have the high losses power beaming incurs. 

    Outside of special circumstances like military forward bases, I don't see much use for beaming power around on Earth. Once you had power satellites at the right Lagrange points, there's no need for it anymore, because everywhere is either in view of one of the satellites, or a transmission line away from someplace in view.

    I figure you start out with LEO demonstrations of the beaming technology, go to GEO satellites for the initial rollout, and then once the market is proven, go to the Lagrange points and lunar surface.

    At that point the existing SPS can be outfitted with ion thrusters, and moved to other locations in the solar system, they don't have to be thrown away.

  47. Giving power to just one client to begin with is a perfectly acceptable limit, if you're just starting out. Phased arrays such as SPS use are perfectly capable of forming more than one beam, as new clients sign on, but you absolutely need to be able to provide continual, reliable power to at least one customer. And then expand from there if the market proves out.

    If you set out to start with the most capable version of the product right at roll-out, you're going to have extreme problems getting together enough capital, and risk burning up the capital you do get without ever becoming a viable business.

    To minimize entry costs, you need the minimum system necessary to do that minimum task: The minimum viable product. Criswell is NOT a minimum viable product.

  48. Given the clear impossibility of putting 20-200TWe of collecting area anywhere at or below GEO, looks like we are stuck with Criswell or L5 or selling something too small to be relevant for global issues such as warming/heating/weirding. Of course, feel free to prove the Space Solar concept with small demos as desired. Probably will make a small amount of money doing it.

  49. Redirectors are for Earth to Earth and other sources. Being able to switch around is a huge advantage of any power beaming. Loads are not constant, even if Sunlight is, Emergencies happen on Earth.

  50. " It's more likely we end up with a declining population due to
    pathological rejection of modernity and embracing nihilism, than having a growing population requiring arcologies."

    I tend to think current declining populations are, inevitably, a temporary phenomenon, because there are obvious variations in reproduction rates, and this is about as direct a target for genetic and social evolution as you could ask for.

    Whatever population finds a way to retain its will to reproduce in the face of social factors discouraging it will pretty much automatically come to dominate over a few generations, short of genocide.

  51. a planetary population in the trillions, I'm dismissing it as infeasible

    I beg to differ. With some technology advances (high density food production, fusion energy, artificial uteri, caretaker AIs) and societal developments (e.g. archologies), we could technically have that many people on Earth one day.

    But I do think that's unfeasible and undesirable for other reasons.

    First, is achieving a forward thinking free world that needs and allows such growth. Arcologies and hyper-urbanization would be the ultimate evil for NIMBYS and green bleeding hearts on the West. It's more likely we end up with a declining population due to pathological rejection of modernity and embracing nihilism, than having a growing population requiring arcologies.

    Second, the mindset and political systems engendered and required by such a hyper-dense population. Seems only collectivist cultures can sustain the desire and means of going that dense, and will probably require crushing dictatorial political systems to become real. Partly for the reasons stated above.

    For me, the only clear path to avoid the Nihilistic Lotus Eaters and the PRC on Steroids Econumenopolis worlds, is to have more actual physical space. And not just literal space, but space to try other political systems, where the nonconformists, eccentric and misfits can go and try their thing and be mostly ignored, until they fail (or succeed).

  52. Yup. I think that will be one of the first fruits of the relative autonomy granted by actually living tens of millions of miles away and really having their posteriors at stake.

    Politicians and ideologues can get antsy and picky while sitting on merciful planet Earth. On Mars, the ones actually there won't have that luxury.

    But I concur: Musk needs to repeat the mantras of the ruling oligarchs to soothe them. For now.

  53. Well, I suppose if you actually put power satellites at all the Lagrange points, (Except #2, obviously!) so that you didn't need redirection hardware, just target switching at predictable intervals, that would be feasible, too.

  54. PR requires him to be publicly hostile to nukes, right now. That, and the fact that regulations on earth have rendered space qualified nuclear power very expensive indeed.

    Once you have a viable colony on Mars, they'll probably start building CANDU reactors from local resources; Martian water is already enriched in Deuterium, and Mars should have plenty of untouched high grade Uranium and Thorium deposits, ready to be mined.

  55. As Dennis says, Musk is running a shipping company. If the check clears, he'll take your payload to orbit, so you don't actually need to convince him space based power is a good idea. You just need to convince some venture capitalists.

  56. It’s a decent trade not counting the much higher cost of putting it in space vs where you need the power, even if that’s using ultra cheap ultra reusable Starships. Like with Space Colonies, he just doesn’t want it confusing planning in his lifetime. With space manufacturing it all gets more realistic.

  57. You don't actually need the beacon to be located where you're delivering the power, that's just the easiest solution. Once you have a beacon to provide a phase reference, (Ideally several.) you can apply a calculated offset from that phase reference to precision target other locations.

  58. Seems to me that Baader-Meinhoff might have been optimistic about their schedule, but that we are well on our way to becoming a police state.

    Though they likely would not enjoy the probably results of the revolution.

  59. Maybe the beacon would make them too easy a target? Doesn't seem like it'd be a big factor but maybe.

    The other possibility is that they really want to be able to transmit anywhere without a beacon, which might have more disturbing possibilities, especially if they're attempting higher power density and lower-orbit sats. But it's hard enough to make it work well enough for power transmission, let along offensive uses.

  60. But just as life colonized land without leaving the sea, each of these stages will leave the prior in existence. Planets and O'Neill colonies will co-exist with zero G colonies and techno-organic lifeforms living free in space and colonizing the Kuiper belt.

    That's what successful species do. They form clades.

  61. I'm not proposing a planetary population in the trillions, I'm dismissing it as infeasible, and pointing out that it's perfectly feasible for a constellation of O'Neill colonies.

    If humanity is a successful species, we will expand to fill all available niches, because that's just what evolutionarilly successful species do. And since it's possible to have much more habitat in orbital colonies than planetary surfaces, that's just where most people will eventually end up living.

    Eventually. Not immediately.

    I see a natural progression ahead of us: Colonize the Moon, Mars, the Venusian atmosphere. As this is happening we will end up building O'Neill colonies, and colonizing orbit around planets, and the asteroid belt.

    Genetic engineering to aid in working in zero G at the frontier will result in a population capable of living comfortably without gravity, and their lower infrastructure needs will give them a competitive advantage over people needing gravity, so the next step is zero G colonies.

    But even in zero G volatiles leak, and are in short supply, so we will eventually develop a version of ourselves that is actually comfortable without them. Probably some sort of solid state nanotech substrate for uploaded minds.

  62. And with solar/battery, you have to convert photon to electron to chemistry back to electron. I'm not seeing a fundamental difference here.

    Battery is more efficient than transmission, which has about 50% power loss from GEO. But since a solar panel in GEO gets 5X as much sun in 24 hours as the same panel on the ground, that seems like a decent trade.

    I wish someone would explain this to Musk. Luckily he'll soon be selling cheap launch at scale to anyone, so we don't actually need him to be convinced.

  63. Around Mars, a stationary orbit is much lower than around Earth, so a redirection system is hardly worth it.

  64. Why should we want a planetary population in the trillions ? If fish could have known, during the Devonian period, that they might eventually evolve into people with smartphones, do you think it would have increased their survival chances to start flopping out of the water ?

  65. Like I've said before, I think SPS have the advantage, in terms of minimum viable product. Criswell requires a much larger investment in order to deliver 24/7 power to a given location. For Criswell you need multiple sites on the moon, transmission lines or power redirection to reach the near side antenna array, redirection to supply fixed locations on the Earth. All the SPS needs is one satellite and one rectenna farm.

    You might establish space based power using SPS, and once you have proven to people that the concept is valid, and already have some rectenna farms, Criswell might look like a useful advance.

  66. That sounds rather like the Baader-Meinhoff terrorists' goal of forcing the West to become a police state, which would make everyone rebel against it and bring on the Glorious Revolution. ( That worked out well for them.) We had a local sufficiency, 100% renewable economy in the middle ages – or perhaps the 'Dark Ages' is a better term.
    When people say something is a 'political impossibility', they're forgetting that everybody changes their mind all the time, and even if they don't, they die, and their kids do.

  67. Depends on the power density. Laser matched to solar cells is fairly efficient, so worth deploying at only a couple suns intensity. But a couple suns intensity isn't really useful as a weapon, for weapons use you need at least 50-100 suns intensity.

    So laser SPS doesn't have to be a laser space weapon, but could be upgraded to be one.

  68. Maybe the military isn't concerned so much about efficiency, and is fine with 99% of the power being wasted due to illuminating the general area where their soldiers are, instead of just the rectenna?

    Anyway, laser power transmission with high altitude reception allows electrically powered drones unlimited flight time.

  69. One you're building solar power satellites around Earth, it's dirt simple to outfit one with ion thrusters, or some other extremely high ISP electrically powered thruster, and have it relocate itself to another location in the inner solar system. It could even bring cargo along with it.

    Wouldn't be as fast as a regular transfer orbit, but quite economical.

    Musk has some plans for Mars that look good from a marketing standpoint, but make little technical sense. Like that dome, or using ground based solar.

    Of course, a Mars colony would need a mix of power sources to avoid the risk of single point failure, and a SPS in Mars stationary orbit isn't what you'd do right out of the gate, but it makes sense later in the colonization process, along with nuclear plants run off Martian sourced fissiles.

  70. My only complaints are that he keeps raising the topic where it isn't relevant, and has trouble accepting that people are allowed to do what they want to do, not what he thinks they obviously should be doing.

    I have little question that O'Neill is superior in the very long term; Planets are absurdly inefficient ways to produce living space with gravity. If you want a solar system population in the trillions, planetary surfaces won't cut it.

    Though I do have concern about leakage rates; Planets are likely to be a lot better at remaining habitable over astronomical periods, I could see an O'Neill based culture burning through the solar system's volatiles budget in only a few million years, an eye blink in terms of how long a planet could remain habitable. But maybe in that time frame we'll become techno-organic lifeforms that don't need volatiles?

    But you have to live through the present and near term to reach the very long term, and long term advantages don't mean a choice is the first thing you should do.

  71. Primarily because the mandates, and failure to price according to availability and reliability, dumps quite a bit of the cost of them on other technologies, that are forced to run at lower duty cycles to have extra capacity to cover for outages. Which makes them less economic, of course.

    Which then leads to even more solar/wind, which leads to the reliable sources having to run at even lower duty cycles, which leads to even more solar/wind.

    It's a vicious cycle, where the unreliable power source drives out the reliable. The only way to interrupt it is to force unreliable sources to internalize the cost of backup. Which appears to be politically impossible.

    I saw a discussion of this several years ago, by a 'renewables' advocate, who was quite open about the goal being to cause the current grid system to collapse, and force everybody to local self-sufficiency.

  72. More than 80% of US Army convoys transport fuel.
    If you can power your FOBs with space power your logistic ‘tail’ becomes much shorter

  73. Well, we will see. I am still waiting for some data on the beam forming. If you cannot make a "sharp" microwave beam, you will not be able to transmit power effectively and it would not work.

    On a side note. If Tony Seba is right, then the combination of terrestrial solar / wind power will be so cheap within the next decade that it would just be very difficult for any other technology to compete. If he is right, that is….

  74. Both Jaffe and the Caltech researchers both seem to take the beam forming as a given, which surprises me. This is particularly surprising when you consider the military application. I have a hard time believing that you would have the option to unfold a couple of km2 of rectenna fields in combat zones. Perhaps there would be time to unfold a few hundred m2? Which would then require the beam to be ridiculously "sharp", going from 0.01 degrees divergence to, say, 0.001 degrees..?

    Similarly, what use would laser power transmission and high altitude reception be? You would have a high flying plane that would receive the power and then…. charge batteries (on the plane) and then land and discharge them for a waiting "client" only to repeat the procedure. Or is he imagining high flying blimps that are tethered to the ground by some power cable?

  75. I notice that there is very little detail on the beam forming. But, the Caltech guy plans (or so it seems) to use angle measurements of the sun to introduce additional phase shifts from the emitters in order to compensate for structural deformations.

    But I thought that the beacon wave would take care of all the problems of controlling the phase of the emitters? And if you are using the beacon wave, why would you need additional phase shifts?? Presumably, if you are, say, 1% of a wavelength "behind" your ideal position, the beacon wave would be phase shifted by 1% upon arrival and this would automatically compensate for this, since you would be using the phase of the incident wave as your reference.

    So it would seem that the Caltech technology ditches the beacon wave and uses it's own source of phase control, which again makes the problem really hard.

  76. The US military wanting it for reduced vulnerability doesn't make much sense. However, as some sort of orbital death ray….

  77. This is great. I didn't know they were so advanced in their tests.

    But this is the way forward, if they want to avoid nuclear power, at least in the inner solar system.

  78. That might be counterproductive, if space solar is your thing.
     'While Musk loves electric cars and spaceflight, there's one thing he hates: space solar power. "You'd have to convert photon to electron to photon back to electron. What's the conversion rate?" he says, getting riled up for the first time during his talk. "Stab that bloody thing in the heart!"'

  79. The power beam can easily bounce off of a few very simple orbital grids, well worth the weight to get full Mars/planet/low orbit coverage with only one source. Criswell redirectors are for micro, but laser would seem almost simpler, if you knew what you were trying to do. Power beaming is sort of a separate topic from space solar, as it can be surface to surface too, with the same redirectors, and is totally agnostic as to power source. In fact, the Space Solar power beaming may be the simplest kind, big and dumb, nothing fancy. You are looking at small landers, a much harder target.

  80. There's a recent NASA NIAC proposal for an outer planets orbiter/lander pair that would effectively use power beaming from the orbiter to the lander (which was electric thruster powered, thus is power rich), which seemed like a backdoor method to further SPS power beaming research at NASA.

    There have been proposals to strap power beaming equipment to a trimodal NTR/NEP rocket heading to mars, to reduced landed weight by removing the surface reactor payload, substituted with a rollable combo rectenna/solar array laid out on the ground (minimal solar PV for life support, and beamed power for active use). The ugly part is needing to be in a high stationary orbit over the lander site, which means this applies only to the cargo rocket (which is alright, since you'd be leaving that reactor anyways), and not the crew rocket/return vehicle, which will need to be in a lower orbit to pick up a crew ascent vehicle.

  81. Ever since that big position paper by DoD on power being needed in FOB's and overseas bases, and SPS being a game changer on a military logistics train, it's been interesting to watch what DoD/DARPA/ORNL have been up to to advance SPS research, particular their realizing practical RF sandwich modules.

    The elephant in the room is DoD wants laser SPS to reduce the surface receiver footprint (GEO requires a multikilometer rectenna, MEO/LEO requires a rather extensive constellation of smaller sats), but there's no practical difference between a laser SPS and a laser space weapon though.

  82. They should look for ways to convert sunlight directly to microwave without the use of photovoltaics. Only this step reduces efficiency to 30% the highest. Some work has already been done in tweaking sunlight wavelength to increase photovoltaic energy generation efficiency here on earth.

  83. I knew this would make Dan Lantz happy. At the risk of encouraging him, (feeding the beast!) he is not wrong in a lot of what he says about O'Neill. Cost effective and practical remains to be seen.
    I sincerely hope this technology can scale up affordably; it would make most other forms of grid scale power generation obsolete. It would also make them cleaner. If only we could clone Elon to handle it if this were the case to make it happen in our lifetimes.

  84. I actually think L5 is the best place for Solar Station, or perhaps the Moon surface. The radars have to be big for the load, so big that the greater distance is not a problem, amazingly.

  85. Mars needs power on the surface, and has similar problems collecting solar as Earth. If you are going to put a nuke on Mars' surface, you have to land it. It would be easier to tow a working solar array into Mars orbit and only have to land the receiver, which I assume would be for laser because of no clouds(?). Then, even rovers could get a laser charge, perhaps. This would be a high return yet small demo project, just what we need. Now, who might be the main customer?

Comments are closed.