Caltech Demonstrates Space Based Solar

Caltech Space Solar Power Project (SSPD) launched into orbit a prototype to beam power to Earth and has transmitted power from orbit to another receiver in orbit. They confirmed that MAPLE can transmit power successfully to receivers in space. They have also been able to program the array to direct its energy toward Earth, which we detected here at Caltech. The system was tested on Earth. They now know it can survive the trip to space and operate there.

MAPLE, short for Microwave Array for Power-transfer Low-orbit Experiment and one of the three key experiments within SSPD-1, consists of an array of flexible lightweight microwave power transmitters driven by custom electronic chips that were built using low-cost silicon technologies. It uses the array of transmitters to beam the energy to desired locations. For SSPP to be feasible, energy transmission arrays will need to be lightweight to minimize the amount of fuel needed to send them to space, flexible so they can fold up into a package that can be transported in a rocket, and a low-cost technology overall.

MAPLE was developed by a Caltech team led by Ali Hajimiri, Bren Professor of Electrical Engineering and Medical Engineering and co-director of SSPP.

MAPLE features two separate receiver arrays located about a foot away from the transmitter to receive the energy, convert it to direct current (DC) electricity, and use it to light up a pair of LEDs to demonstrate the full sequence of wireless energy transmission at a distance in space. MAPLE tested this in space by lighting up each LED individually and shifting back and forth between them. The experiment is not sealed, so it is subject to the harsh environment of space, including the wide temperature swings and solar radiation that will be faced one day by large-scale SSPP units.

MAPLE also includes a small window through which the array can beam the energy. This transmitted energy was detected by a receiver on the roof of the Gordon and Betty Moore Laboratory of Engineering on Caltech’s campus in Pasadena. The received signal appeared at the expected time and frequency, and had the right frequency shift as predicted based on its travel from orbit.

The next steps for the team are to assess the performance of individual elements within the system by evaluating the interference patterns of smaller groups and measuring difference between various combinations. The researchers say the process, which can take up to six months to fully complete, will allow the team to sort out irregularities and trace them back to individual units, providing insight for the next generation of the system.

The SSPD deployed a constellation of modular spacecraft equipped with PV to collect sunlight, convert it to electricity, and then wirelessly transmit the electricity to the ground. Caltech said the technology could be useful to remote areas that do not have supportive transmission infrastructure.

Wireless power transfer was demonstrated by Microwave Array for Power-transfer Low-orbit Experiment (MAPLE), developed at Caltech. It is one of three key technologies being tested by the Space Solar Power Demonstrator (SSPD-1), the first space-borne prototype from Caltech’s SSPP.

MAPLE includes lightweight microwave power transmitters driven by custom electronic chips that were built using low-cost silicon technologies. It uses the array of transmitters to beam the energy to desired locations.

In addition to the $100 million from Donald Brens, Northrop Grumman Corporation also provided Caltech $12.5 million over three years through a sponsored research agreement between 2014 and 2017 that supported for the development of technology and advancement of science for the project.

Future Caltech Design

A future Caltech design will have individual SSPP units will fold up into packages about 1 cubic meter in volume and then unfurl into flat squares about 50 meters per side, with solar cells on one side facing toward the sun and wireless power transmitters on the other side facing toward Earth.

A Momentus Vigoride spacecraft launched aboard a SpaceX rocket on the Transporter-6 mission carried 50-kilogram SSPD to space. Momentus is providing ongoing hosted payload support to Caltech, including providing data, communication, commanding and telemetry, and resources for optimal picture taking and solar cell lighting. The entire set of three prototypes within the SSPD was envisioned, designed, built, and tested by a team of about 35 individuals—faculty, postdocs, graduate students, and undergrads—in labs at Caltech.

SSPD has two main experiments besides MAPLE: DOLCE (Deployable on-Orbit ultraLight Composite Experiment), a structure measuring 6 feet by 6 feet that demonstrates the architecture, packaging scheme, and deployment mechanisms of the modular spacecraft; and ALBA, a collection of 32 different types of photovoltaic cells to enable an assessment of the types of cells that are the most effective in the punishing environment of space. The ALBA tests of solar cells are ongoing, and the SSPP has not yet attempted to deploy DOLCE as of press time. Results from those experiments are expected in the coming months.

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A Momentus Vigoride spacecraft was carried aboard a SpaceX rocket on the Transporter-6 mission will carry the 50-kilogram SSPD to space. It consists of three main experiments, each tasked with testing a different key technology of the project:

* DOLCE (Deployable on-Orbit ultraLight Composite Experiment): A structure measuring 6 feet by 6 feet that demonstrates the architecture, packaging scheme and deployment mechanisms of the modular spacecraft that would eventually make up a kilometer-scale constellation forming a power station;

* ALBA: A collection of 32 different types of photovoltaic (PV) cells, to enable an assessment of the types of cells that are the most effective in the punishing environment of space;

* MAPLE (Microwave Array for Power-transfer Low-orbit Experiment): An array of flexible lightweight microwave power transmitters with precise timing control focusing the power selectively on two different receivers to demonstrate wireless power transmission at distance in space.

An additional fourth component of SSPD is a box of electronics that interfaces with the Vigoride computer and controls the three experiments.

17 thoughts on “Caltech Demonstrates Space Based Solar”

  1. Huge phased arrays of solar powered emitters, and the use of relatively cheap lunar elements as reaction mass will make orbital, and cislunar space deltaV easy, and very, very scalable. There will be a distance from the earth moon system where it is possible to power spacecraft. How far, how much power, and how many targets is anyone’s guess.

    A solar system level industrial base could have phased arrays of emitters orbiting around every planet, and their solar LaGrange points. Imagine propelling a craft across the solar system supplied with pre accelerated reaction mass, as well as energy for some VASIMR derived reaction drive. Lots of energy, and lots of mass make high velocities, particularly in the plane of the ecliptic. Sol’s gravity lens would be our oyster.

    It might even obviate tethers other than lifting from the surface. It could power those tethers with lunar mass dropped into Earth’s gravity well, either made into products, or as ballast dropped, or used as reaction mass.

    A way to safely dump ballast to the surface should be developed. How about liquid oxygen dumped into the stratosphere, or bb sized particles targeted at a “drop zone” far from airlines, and habitation. If materials were dropped as different sizes of spheres they could be easily separated, and if small enough would slow, and cool in the troposphere. Some shape other than sphere might better

  2. A gigawatt or two would be great to power a high-thrust arcjet rocket. Heating hydrogen at the same temperature as a chemical rocket but with a fraction of the molecular weight would give it the same performance as a NTR without the hassle of being a private company owning and operating a highly-enriched uranium-fueled nuclear reactor.

  3. Google bard says “the average total cost of constructing a 1 GW solar panel plant in the US is currently around $1.1 billion”. This info with Brian’s always appreciated cost analysis means its going to be tough to find investors.

  4. Was there actually any real question this would work? No, there wasn’t, they’re not testing anything yet that there are real technical questions about, and all these tests could have been done in a vacuum chamber on Earth, at much less expense, and told us just as much. From that perspective, it was mostly a gimmick, a PR stunt. This test wasn’t even performed in the same space environment that a real SPS would experience, the orbit was way, way too low.

    The real test to be done is microwave transmission through the ionosphere. That is, IMO, the real potential deal breaker, the point where the concept stands the most chance of being rendered infeasible. Just because it looks like it will work given a static analysis of things, doesn’t mean you won’t get localized ionization or blooming effects that defocus the beam.

    After that we need real testing of electronics survival rates in HIGH orbit, not low, at scale, so any non-linear effects can be seen. What’s the electrostatic field around an SPS going to do? Will sputtering off one part of the satellite compromise some other part?

    Not to say that this wasn’t valuable, but it was mostly valuable as a learning experience for the students. Actual tests have to be much larger in scale, and in the correct orbit.

    • I look at it as a proof of concept project, rather than a full scale test. Another benefit that they couldn’t do in a vacuum chamber was confirming that the panels would deploy after being subjected to the g-forces of the launch. But I don’t really disagree with your analysis, it’s a small step forward.

  5. More interesting is the possibility of beaming power to a spacecraft. If you can beam megawatts accurately over distance as you would have to do to make this work for power delivery on earth… then powering vasmir or ion engines becomes practical. But that said the collectors have to be orders of magnitude smaller than solar cells for there to be any advantage

    • I think you might profit there by avoiding using power conversion circuitry, and just directly focusing the incoming energy into the reaction mass.

  6. This seems to be an unreasonably expensive way to create electricity. Is everyone going to be cool with giant space lasers firing down from the heavens? How can this ever be more economical than a robot truck setting solar panels in the desert?

    • Once you’re in high orbit, you’re exposed to the Sun nearly 24 hours a day. No storage or backup supply needed. That’s a really big deal.

      Sunlight is also more intense in space.

      No weather to protect the panels from, so they can be a LOT lighter.

      And you can probably beam it down closer to the market than any desert is likely to be.

      But mainly, 24 hour operation, instead of 8 hour.

  7. Kurt Sorenson, of molten salt reactor’s fame, gave a talk about his background and molten salt reactors. He once worked for NASA on a project to predict Solar Satellite costs. He was VERY PRO solar satellites. He’s VERY pro space travel but…he said his fellow worker had this huge spreadsheet of every single cost they could possibly find, and it was not coming out favorably. One day he told him to input the launch cost to zero, and it still was not financially favorable. Maybe they were wrong, but that’s what they came up with. He said the administrator told him to not write that in the report. There’s no doubt that he was favorable to the idea, The numbers just did not work out. I also see they are using solar cells. I don’t think it’s possible for solar cells to get near the same efficiency as solar mirrors and using heat engines to make power.

    I think this is likely one of if not the best talk on nuclear power and molten salt reactors available. It’s well worth watching if you are interested in this sort of thing.

    • I talked to Kirk many times back in the early days of his pro-Thorium work. Others have run the numbers and you can see numbers where the Starship can bring the costs for 25MW per launch down to $5M or $10M per launch. $200-400M to launch a GW.

      Need to mass produce the solar modules at $4000 per Kilowatt to the ground. $4B for a gigawatt with above nuclear power plant operating capacity.95-98% instead of 90%. $2-4B for the gigawatt of ground receiving. $6.2-8.4B for a gigawatt system. At a higher orbit.

      • To make it clear, I am not in any way against solar power satellites. I’ve likely read the same books as Kirk. I have the ones he mentioned in the first part of the video. I would be deliriously happy if SPS could be used to bootstrap space industry and space habitats but what he said was that even with high efficiency heat engines, I assume turbines, and a cost of $0.00 for launch cost the economics would not work. And he emphasized that all their cost was structured to give them the best and most favorable cost possible. It’s in the video I linked at the first few minutes.

        I favor habitats far more than I do going to Mars. Going to Mars is great but living there seems problematic to me compared to habitats. Especially if the habitats are made of lunar or asteroid material.

        One of the biggest problems we have is no sustained long term commitment. If you sent 4 or 5 humanoid robots with basic AI to the Moon with some manual hand tools, big solar mirrors, solar power carts and robot oxen. Have them build tools, machinery and slog away at it, eventually they could build an elaborate infrastructure. Use solar mirrors to melt metals and then build basic machine tool stuff like surface plates, 90 degree right angles, then lathes…etc. Most of it is just repetitious grinding away, but over time you build the tools, you can build anything.

  8. So what is the net energy impact on the planet as we start beaming energy right to the surface? I am curious as to the global warming impact of solar satellites.

    • The calculation for the global warming effect of enough nuclear or geothermal to give everyone of a population of billions several kilowatts is done at the bottom of this webpage & the top of the next.
      It turns out to *just* barely show up as a contributor to climate change. Very small compared to the effect of the CO2 already put into the atmosphere.
      If Solar Power Satellites turn out to be practical, their contribution would be about the same, ie: too small to worry about.

      • I’m not sure where that number above comes from, but if all the power we generate is 1/10000 of the solar energy we receive, then our effect on global warming would have to be insignificant. Since that is not the case, I think the appropriate question might be how much more energy would these satellites bring to the earth as a percent of our existing thermal output.

  9. The SSP hype is much greater than the reality. I doubt that the percentage of the power collected on the Earth was significant compared to the power collected in space. It takes very little power to light up a single LED. Such demos don’t indicate that profitability is in the foreseeable future. And profitability is what matters if large solar power satellites are ever going to become a reality.

    • True, … but consider that the very, very, very first transistor was invented way back in the early 1950s, and consisted of a little chunk of germanium with 2 uniquely important ‘whiskers’ of wire touching it. One, was called the ’emitter’ because it’d be the source of electrons going thru the germanium. The other was the ‘collector’, since it’d collect the electrons back. And the chunk itself was the ‘base’, because it was the base upon which the other parts touched, and did the modulation business.

      Not a single person had yet foreseen, or for that matter, predicted that someday soon after, the transistor would be substantially hardened, made robust by sintering (at first) blobs of indium onto the germanium to act as much better electron carriers, and then relatively shortly after that, that basic photographic methods (“lithography”) would be used to etch little patterns on the flattened silicon (which replaced germanium, rather quickly), to create the absolute first-ever entire logic gates on a single chunk of the base material.

      And from there, within a matter of 5 years, the I.C. or integrated circuit became basically ubiquitous. Hobbyists could purchase ‘grab bags’ of various chips, mind-bogglingly primitive by today’s measure(s), and could hook them up using a simple 6 volt ‘lantern battery’ or easy-peasy DC power supply in such a way that true digital logic could be wired-and-tested. By 10 year olds. In their Dad’s basement ‘shop’. Which I did. At the time. Obviously

      AND STILL it wasn’t imagined that ‘the computer’ would come in just a few years, and would be almost as accessible to the (rather well heeled) hobbyist as those first lame IC chips. Indeed, from CromemCo, one could (as I did) purchase entire kits of CPUs, memory chips, sockets, circuit boards, and so forth to wire-wrap (no solder!) them together not-quite per instructions, but helpfully pointed in the right direction, to make a actual, functional, and even better, barely useful computer. A computer!!! Hot d*mn!

      Anyway the point is obvious. This little experiment, lofted to fr*gging space, to transmit a few watts of power from a phased array to a purpose-built receiver, and convert that to DC, to get a couple of LEDs to blink … is pretty primitive. And good. And like the story above, just the itsy-bitsy tip-of-the-tip of what is possible. Possible — I might add — with stuff we have here, now, today, ubiquitously. The only thing(s) really missing are SCALE, FUNDING and SPONSORSHIP.

      So, think big people. Thing big, big, big!!! Space power is a thing and will eventually become so darn ubiquitous in practice that we won’t even be surprised by any of it.

      So Sayth I.

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