Caltech Space Based Solar Power Cubesat Demo Flying December 2021

Dr. Rich Madonna gave a talk on Caltech’s SSPP (Space based solar power project) this past week.

Attendees of his talk are the leaders in the Space Based Solar Power community.

· Dr. Paul Jaffe (UMD)
· John Bucknell (Virtus Solis)
· Dr. Al Globus (UC San Jose)
· Skylar Hoffert (student)
· Dr. John Mankins (ex-NASA SSP head)
· Dr. Naoki Shinohara (Kyoto University)
· Dr. Xinbin Huo (China Academy of Space Technology)
· Dr. John Olds (Spaceworks)
· Charles Hall (Spaceworks)
· Jeff Madonna
· Rian Moriarty
· Michael Sanders (USNA)
· Haroon Oqab (Kepler Space Institute)
· Darel Preble (Space Solar Power Institute)
· Takayuki MATS
· Keith Henson

John Bucknell summarized Rich Madonna talk. Rich described progress since 2019.

Maintaining ‘membrane’ deploying concept – prior concept with deployable parabolic concentrators and antenna too expensive to manufacture

Switch to thin-film GaAs PV (Alta Devices/MicroLink)

Transparent conductor, PV, Ground Plane, RF/Power electronics and antenna layers about 1000microns thick

Improved deployment with a pneumatic inflator of membrane

Update power beaming from 2.45GHz to 10GHz

CMOS IC power amplifier, phase shifter, 16 antennas (3x3mm) now in 8th generation

Built and testing printed flexible 256 antenna transmitter

SW compensation for shape of the antenna, based upon exciting one antenna and rest receiving to triangulate the position

System Engineering

Improved availability of power transmission from 45% to 75%+ by moving to dual face operation (PV or RF from both sides of membrane)

LCOE-based analysis of engineering assumptions

Evaluated GEO and MEO orbital constellations, recognizing GEO is crowded

15 year life assumed

Orbital demo at end of year (2021). It is a rideshare on Momentus Vigoride demo mission (6 month duration).

Satellite Today reported that Momentus would launch the Caltech Space based solar mission.

Momentus has a contract for its second customer on its hosted payload service, and will host a payload from the California Institute of Technology (Caltech), called SSPD-1 at the end of next year. SSPD-1, which will demonstrate a wireless power transmission and a new deployable structure, is set to launch on Momentus’ Vigoride orbital transfer vehicle in December of 2021, and operate onboard the vehicle for about six months.

The hosted payload service is a new offering from Momentus, which is gearing up for the first flight of its orbital transfer vehicle, Vigoride, on SpaceX’s upcoming rideshare mission in 2021.

The Caltech space-based solar concept is based on the modular assembly of ultralight, foldable, 2D integrated elements. Integration of solar power and RF conversion in one element avoids a power distribution network throughout the structure, further reducing weight and complexity. This concept enables scalability and mitigates local element failure impact on other parts of the system.

In May 2017, Caltech had the first ultralight integrated prototype collecting solar power and wirelessly transmitting it is demonstrated at Caltech. The prototype has an aeral density of 1.5 kg/m2, more than 10x lighter than previous examples. This modular element can be repeated over an arbitrary area to form a large aperture which could be placed in orbit to collect sunlight and transmit power to any location.

In December 2017, Caltech had the second iteration functional prototype is demonstrated at Caltech. This prototype was 33% lighter than the first version, achieving areal density of less than 1 kg/m2. It integrates photovoltaics and power transfer circuitry and incorporates beam steering.

Dr Richard Madonna published a June 2019 summary of the Space Solar Power Initiative. He gave a talk at the National Space Society International Space Development Conference in 2019.

Caltech/Northrop Grumman Space Solar Power Initiative (SSPI) was a three-year effort to mature technological concepts associated with an innovative, ultra-light weight design for a satellite capable of converting solar energy to radiofrequency energy and beaming it to earth to power electrical grids. The presentation summarizes these efforts and describes how the lessons learned help shape the current Caltech Space Solar Power Project.

SOURCES- Caltech, Google Groups Space Based Solar Power, Satellite Today
Written By Brian Wang,

24 thoughts on “Caltech Space Based Solar Power Cubesat Demo Flying December 2021”

  1. Molniya orbits struck me as a good compromise, assuming you can get a customer on both sides of the rotation.

    Longer transmittal windows than MEO, with good coverage of the northern hemisphere. Much easier to boost into than GEO.

    Smaller microwave arrays needed than GEO.

  2. The mines are very similar to the remote military base situation. Bases need very small power level, but they really need it. Mines need large power level, but don't move and yet are still remote from energy. I suggest power beaming from the North energy areas, if they have gas or coal to burn there. Also, rectennae are easy, just poles in the ground and a wire mesh, no need for very smooth, unlike the transmitters. Farm or live under them.

    The advantages of In Space Mfg, ISM are so great that we will be wondering why we didn't start earlier. Check out the Criswell link I have on this blog, different comment. The lunar radar for LSP is quite a deal, very huge but scattered all about so it only *looks* continuous from the Earth's direction, and a small surrounding Space. I even question whether the LSP material should not be mined on Moon, sent to Space on mass driver, ISMd, then returned to Moon surface, rather than try to mfg on Moon. Examine your mines for evidence of g, it is every where!

  3. Thanks – interesting stuff. Mines in the north are an interesting candidate for this eventually, as they have large, consistent power needs, and sometimes have few options from other alternative energy sources. Having existing surface disturbance, few neighbors, and lots of heavy equipment to prepare ground for a rectannae cheaply might make things easier as well.

    What you are saying about the focusing radar makes sense. I find it hard to imagine the frail modular things having a real-world application due to their cost and complexity. Figuring out how to build cheap sheets of solar film on the moon and having one giant antenna does seem more practical. Maybe there is some way to have the initial manufacturing facilities designed to serve as an antenna?

  4. The IEEE paper from the earlier Space Solar blog has focus details, a very complex subject as the basic tech works but they are doing all sorts of improvements that are engineering rather than simple Physics. Many engineering improvements is a very good sign. "From the Moon" works if the load is so large that the needed bigger focus radars are also needed for that load alone, and thus the added distance is suddenly free rather than a huge obstacle. The basic problem of being too far North is solved by power beaming redirectors, which can reflect power beams whether from Earth or Space, where most collection will be near celestial equator. Without redirector sats, you need to make longer rectennae, as the video shows for the MEO plan they present. Also, more generally, not all loses are the same. If you lose 2/3 power in a steam turbine after burning coal, that is a bad loss. Losing 2/3 power from sunlight in Space is not as bad. The sunlight is free.

  5. Can these integrated circuits really create a power beam focused enough to hit a target on earth without huge loses (and from the moon)? It just seems impossibly hard to control, but I certainly know nothing about radio transmission… Lots of mines in the north have few good alternate energy options, compared to their current diesel generators. How far north do you think the grouped satellites in elliptical orbits can service effectively?

  6. If you can money doing it now, by all means. Neither effort should wait for anything. Launch of product v launch of factory and launch of material v lunar material are various way of extracting gold from them thair hills. Energy is just energy. If you get the right price, anything you do in Space will have far more likelihood of future growth.

  7. K, the other blog is full, but sunlight is free, as are deer, if you need very few:

    Actually, the solar sunlight we are talking about is free as I describe. You are free to heat up an object in the sunlight in Space in the solar system to your heart's content. Thus, the sunlight energy is free for that. It is thus free. Further processing into electricity is a *service*, not free. You may be distracted by the fact that there is little in Space and nothing on Earth that is actually free like sunlight in the solar system. So it follows unusual rules. When you look up on a clear night, and see the stars, is there sunlight there?

  8. Sure, I definitely see it as the long-term solution. I just don't think there's any need to wait for it, in this case. It'd be economical just launching everything from Starship.

    The book *The Case for Space Solar Power* does detailed cost engineering. They figured 15 cents/kWh at scale, but that was pre-SpaceX pricing. I plugged in Starship costs and got 4 cents/kWh. At that level launch isn't even the major cost, it's mostly manufacturing, and 0.7 cents/kWh for the ground station.

  9. Existing pipelines, refineries, and chemical plants in Louisiana, and east Texas make the area a natural for huge rectenna farms. Only 30 degrees from the equator, so easily served from high equatorial orbits.
    Spaceport is at 25 degrees north. Run starships on solar energy stored in methane.

  10. "A (relatively) small CH4 leak led to fire on engine 2 & fried part of avionics, causing hard start attempting landing burn in CH4 turbopump."

    Thanks, Captain Obvious. I figured that out just watching the launch videos. Nice of them to come out and say it, though.

    They really need to eliminate those leaks, the only place stuff is supposed to come out of that engine is the bottom. And the Raptors have been suffering these small CH4 leaks from the beginning, you can see one or more engines on fire in almost all the launch videos.

  11. Near the end of the main video, he clearly sez "kilowatts per hour" several times, when "kilowatt hours"would clearly be appropriate. Also, can math guy verify min 13 math? distance has to be greater than? Seems like that would only be a problem if real close, going out of view to the sides. Is he saying there is a maximum dia to radars even if small apparent angle?

  12. The RF transparent PV may be the very thing that makes Criswell LSP the clear winner, altho it was not given as a possibility in the listing in the video, in case you did not notice. The reflecting screens in LSP can now be coated both sides with PV and perhaps become additional transmitters, instead of merely reflecting. Perfect enhancement for low sun. I know everyone knows this by heart, but it perhaps should be added to the list. Not my first request to NSS on this matter, btw. Keep a copy for future reference!

  13. Yes, ISM with launched raw material, or ready to form material, could still be far better than launched product, even far lighter total. It also makes adding In Space Resource much easier, having tested the factory.

  14. You are fighting with DARPA on this, who sees the clear advantage of ISM over launch. See all the effort going into folding and the not having a flat surface when there. The weight to withstand launch forces is also gone. May be things can only be done in 0 g. Given that the materials will be coming from Space, mostly, there is little choice or reason to not do all you can ISM. Will computer chips be launched? Only until they realize how much easier computer chips are to make in Space. Think long term, start now. Cheap launch -> easier to launch factories. Free fusion will be too expensive, turbine plus distribution more than even Earth solar! Use existing fusion, it runs at higher temp, gives better light.

  15. Until you're putting enough stuff in space that it becomes economic to move manufacturing there. Space does have potential for things like large scale vacuum sputtering, and you should be able to save on a lot of things by not requiring them to be able to survive launch accelerations or endure an oxidizing atmosphere.

  16. Once you've got such a double sided array, I should think you'd optimize its orientation for transmission purposes.

    The back side can be fed light regardless of sun direction by means of a large thin film mirror. You might even make a wavelength selective mirror, so as to reduce the heat load on the array; No point in sending light to it that won't be converted to power, after all.

    I'm not concerned with crowding in geosynch, it's fairly easy to just run a tether around the orbit, or sections of it, anchored by SPS at each end, and spare the satellites station keeping needs. That allows considerably closer spacing.

  17. I don't know, these things look pretty lightweight, and nontrivial to manufacture. At Starship prices it probably makes sense to just launch from Earth.

    Sourcing from space is fantastic for bulk materials, but for complex manufacture you need all the infrastructure that takes you the whole way from raw materials to refined elements to all sorts of components to finished product. If we wait for all that before we doing SPS, we might get cheap fusion first.

  18. "Update power beaming from 2.45GHz to 10GHz" Don't know if that is for this one project, or big news for all Space Solar.
    Collectors, rectennae, are everywhere/anywhere a 200 MWe power plant is desired.
    Poor people can use labor and local materials to build collectors, and thus own them. These are 50 to perhaps 80 % of the cost. Poor people will be the first customers, as the need is great to have a little, and so they can even pay more per KWe-h , but will use very little compared to Americans. That little means lights and refrigerators, however, a big deal.
    For next two, see the IEEE paper.
    Yes, they must be built from lunar or asteroid material, at least mostly. ISM will turn out to be a huge advantage over launch for many big reasons, and after that whether the material is launched or mined from Moon is a simple cost compare.
    I could not agree more that we need to focus on this. Global heating/warming/weirding as well as the sheer scale of the pretty simple project, after all, seem to make it a logical next step. Now, this is a gold rush, folks. The biggest ever. Forget normal business models. I'm very serious about that. Can I hop a ride?

  19. In theory, I like the idea of space-based solar, but the devil is in the details.
    Exactly how will it transmit this energy back to Earth?
    Where will the power collectors be located?
    Will poor countries get any of the energy?
    How will all this (microwave) energy affect existing satellites as it travels down to the surface?
    How efficient can we get?
    Can we build the arrays by mining space?

    I understand this is just an early test, but we need to be thinking of these things as we move forward.

  20. Bucknell seems to prefer triple sets of sats in Molnyia orbits as a solution, which might work out in favor of double sided membrane sat designs.

    One alternative to the flat face pointing availability problem might be the HESPeruS designs, which use what looks like a wind spinner arrangement to allow sandwich modules.

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