By 
January 17th, 2024
Image credit: Caltech/SSPP
The Caltech Space Solar Power Project is developing the technology that will be needed to one day harvest solar power in space and beam it down to Earth.
It has been a year ago that demonstrator technology was placed into Earth orbit. On location, the SSPD-1 technology tried out three technological innovations deemed needed to make space solar power a reality.
The SSPD-1’s mission in space has now concluded, notes a Caltech statement on the Space Solar Power Project (SSPP).
It was launched on January 3, 2023, aboard a Momentus Vigoride spacecraft.
Image credit: Caltech/SSPP
Main experiments
The in-space testing of SSPD-1 consisted of a trio of main experiments, each evaluating a different technology:
DOLCE (Deployable on-Orbit ultraLight Composite Experiment): a structure measuring 1.8 meters by 1.8 meters that demonstrates the novel architecture, packaging scheme, and deployment mechanisms of the scalable modular spacecraft that will eventually make up a kilometer-scale constellation to serve as a power station.
ALBA: a collection of 32 different types of photovoltaic (PV) cells to enable an assessment of the types of cells that can withstand punishing space environments.
MAPLE (Microwave Array for Power-transfer Low-orbit Experiment): an array of flexible, lightweight microwave-power transmitters based on custom integrated circuits with precise timing control to focus power selectively on two different receivers to demonstrate wireless power transmission at distance in space.
Image credit: Caltech/SSPP
Not all according to plan
“Though all of the experiments aboard SSPD-1 were ultimately successful, not everything went according to plan,” the Caltech statement adds.
“The space test has demonstrated the robustness of the basic concept, which has allowed us to achieve a successful deployment in spite of two anomalies,” says Caltech’s Sergio Pellegrino, professor of aerospace and civil engineering and co-director of SSPP.
Meanwhile, the space solar power project team continues work in the lab, studying the feedback from SSPD-1 “to identify the next set of fundamental research challenges for the project to tackle,” the Caltech statement concludes.
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Posted in Space News
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.
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.
The only reason Caltech is doing this is that a really rich person with delusions gave them 100 million dollars to research space based solar power: https://www.caltech.edu/about/news/caltech-announces-breakthrough-100-million-gift-to-fund-space-based-solar-power-project . They know as well as anyone with a bit of RF experience that what they’re doing isn’t really increasing the TRL of space based solar power transmission. It’s just humoring the donor for the money.
The best that can be said is that it’s the first flex pcb RF system in orbit. That’s kind of cool but as a person looking to be inspired and improve things it seems like a significant waste of money. It’s not like high power RF transmitters haven’t been tested in vacuum in LEO before. There have been many, many radar satellites.
They should’ve been spending they $100 million attempting to make coherent kilometer scale transmitting apertures on Earth and actually demo something that’d prove the feasibility of space based solar power transmission.
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