# Space-based solar power: Techniques

Giant mirror satellites, flat arrays and tiny test craft

Source page: https://www.materialinsights.org/energy/e_space_solar/techniques/

What this tab covers The methods used to capture this energy: how each works, and how they compare on efficiency, cost, life-cycle emissions, maturity and scale.

One technique with several design variants: large geostationary satellites beaming microwaves to kilometre-scale ground antennas, and small low-orbit demonstrators, some using lasers. Only small demonstrations have flown.

#### Comparison

| Method | Efficiency | Cost | Life-cycle emissions | Maturity | Scale |
|---|---|---|---|---|---|
| **Geostationary microwave satellite with reflectors (NASA RD1, CASSIOPeiA-type)**^[1](https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf)^[2](https://editor.fnc.co.uk/media/fi4pvbgv/space-based-solar-power-final-report.pdf)^[3](https://www.fnc.co.uk/media/ae2eadpi/fnc-004456-51624r-phase-2-economic-feasibility-issue-1-1.pdf) | About 13% sunlight to grid (calculated); 99.7% capacity factor. | NASA baseline USD 610/MWh (FY2022 dollars), 12 to 31 times projected 2050 terrestrial renewables; USD 30-40/MWh if all optimistic assumptions hold. UK study: GBP 50/MWh p50 (GBP 35-79, 2018 prices). ESA study: EUR 106-206/MWh for a first unit at a 20% hurdle rate. | 26.6 g CO2e/kWh baseline (about 3.8-3.9 optimistic), excluding upper-atmosphere launch effects. | research | None built. Designs deliver about 1.4 to 2 GW each. |
| **Geostationary planar microwave satellite (NASA RD2)**^[1](https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf) | Same conversion chain; 60% capacity factor. | NASA baseline USD 1,590/MWh (FY2022 dollars); USD 80/MWh optimistic. | 40.4 g CO2e/kWh baseline (4.3 optimistic). | research | None built. |
| **Low-orbit demonstrators (Caltech MAPLE, Japan OHISAMA, Aetherflux)**^[5](https://www.space.com/space-solar-power-satellite-beams-energy-1st-time)^[6](https://www.notebookcheck.net/Space-based-solar-power-Japan-s-OHISAMA-project-aims-to-beam-solar-energy-to-Earth.1025860.0.html)^[7](https://techcrunch.com/2025/04/02/space-solar-startup-aetherflux-raises-50m-to-launch-first-space-demo-in-2026)^[10](https://www.japanearthobserver.com/jeo-20-news-roundup-16-sept-2026/)^[11](https://www.cowboyspace.com/news/reason-1-takes-flight)^[12](https://highways.today/2026/10/01/cowboy-space-orbital-power-beaming/) | Not reported for demonstrations. | Aetherflux raised USD 60 million in total by April 2025. | No life-cycle study found. | pilot | Milliwatts to watts demonstrated; kilowatt-class tests pending. |

Cost estimates differ more than tenfold: NASA's 2024 study puts baseline costs at USD 610-1,590/MWh, while the UK and ESA studies, assuming cheap reusable launch and learning, find about GBP 50/MWh and EUR 89-206/MWh. The gap is driven mostly by launch cost (71-77% of NASA's system cost) and hurdle rates. Baseline emissions of 27-40 g CO2e/kWh sit within NASA's range for terrestrial renewables (13-43).

#### How each method works
**Geostationary microwave satellite with reflectors (NASA RD1, CASSIOPeiA-type)**

Mirrors concentrate sunlight onto solar panels on a satellite 35,786 km up, above one point on Earth. A phased array forms a 2.45 GHz microwave beam aimed at a ground rectenna, a field of small antennas and diodes that turns it back into electricity.^[1](https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf)^[2](https://editor.fnc.co.uk/media/fi4pvbgv/space-based-solar-power-final-report.pdf)^[3](https://www.fnc.co.uk/media/ae2eadpi/fnc-004456-51624r-phase-2-economic-feasibility-issue-1-1.pdf)
**Geostationary planar microwave satellite (NASA RD2)**

A flat solar array without mirrors transmits at 5.8 GHz to five 4 km ground sites. Simpler, but with a lower capacity factor.^[1](https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf)
**Low-orbit demonstrators (Caltech MAPLE, Japan OHISAMA, Aetherflux)**

Small satellites test the key steps. Caltech's MAPLE (launched January 2023) beamed power to receivers about a foot away and sent a detectable signal to a Caltech roof. Japan's 180 kg OHISAMA aims to beam about 1 kW of 5.8 GHz microwaves from about 400 km to Suwa, Nagano; as of September 2026 it had not launched (target FY2026). Aetherflux, renamed Cowboy Space in May 2026, launched its kilowatt-class laser satellite Reason-1 on 1 October 2026; no results had been reported by October 2026.^[5](https://www.space.com/space-solar-power-satellite-beams-energy-1st-time)^[6](https://www.notebookcheck.net/Space-based-solar-power-Japan-s-OHISAMA-project-aims-to-beam-solar-energy-to-Earth.1025860.0.html)^[7](https://techcrunch.com/2025/04/02/space-solar-startup-aetherflux-raises-50m-to-launch-first-space-demo-in-2026)^[10](https://www.japanearthobserver.com/jeo-20-news-roundup-16-sept-2026/)^[11](https://www.cowboyspace.com/news/reason-1-takes-flight)^[12](https://highways.today/2026/10/01/cowboy-space-orbital-power-beaming/)

#### Sources

1. [Space-Based Solar Power (Office of Technology, Policy, and Strategy)](https://www.nasa.gov/wp-content/uploads/2024/01/otps-sbsp-report-final-tagged-approved-1-8-24-tagged-v2.pdf) NASA, 2024
2. [Space-Based Solar Power: final report (cost-benefit study for ESA SOLARIS)](https://editor.fnc.co.uk/media/fi4pvbgv/space-based-solar-power-final-report.pdf) Frazer-Nash Consultancy, 2022
3. [Space Based Solar Power as a Contributor to Net Zero, Phase 2: Economic Feasibility](https://www.fnc.co.uk/media/ae2eadpi/fnc-004456-51624r-phase-2-economic-feasibility-issue-1-1.pdf) Frazer-Nash Consultancy for UK BEIS, 2021
4. [Scientists beam solar power to Earth from space for 1st time ever](https://www.space.com/space-solar-power-satellite-beams-energy-1st-time) Space.com, 2023
5. [Space-based solar power: Japan's OHISAMA project aims to beam solar energy to Earth](https://www.notebookcheck.net/Space-based-solar-power-Japan-s-OHISAMA-project-aims-to-beam-solar-energy-to-Earth.1025860.0.html) Notebookcheck, 2025
6. [Space solar startup Aetherflux raises $50M to launch first space demo in 2026](https://techcrunch.com/2025/04/02/space-solar-startup-aetherflux-raises-50m-to-launch-first-space-demo-in-2026) TechCrunch, 2025
7. [JEO 20: News Roundup, 16 Sept 2026 (OHISAMA status)](https://www.japanearthobserver.com/jeo-20-news-roundup-16-sept-2026/) Japan Earth Observer, 2026
8. [Our First Mission Takes Flight (Reason-1)](https://www.cowboyspace.com/news/reason-1-takes-flight) Cowboy Space (formerly Aetherflux), 2026
9. [Cowboy Space puts orbital power beaming to the test with Reason-1](https://highways.today/2026/10/01/cowboy-space-orbital-power-beaming/) Highways Today, 2026

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_space_solar/index.md)
- [Overview](https://www.materialinsights.org/energy/e_space_solar/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_space_solar/correlation/index.md)
- [Efficiency](https://www.materialinsights.org/energy/e_space_solar/efficiency/index.md)
- [Resources and labour](https://www.materialinsights.org/energy/e_space_solar/resources/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_space_solar/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_space_solar/links/index.md)