In November 1968, Peter Glaser of Arthur D. Little published a two-page paper in Science titled "Power from the Sun: Its Future." He proposed putting photovoltaic arrays in geostationary orbit — where sunlight is 36% stronger than at Earth's surface and available 99% of the time — and beaming the energy down as microwaves to ground-based rectennas. He got U.S. Patent 3,781,647 for it in 1973. NASA and the Department of Energy took him seriously.

Between 1975 and 1979 they spent about $20 million producing the SPS Concept Development and Evaluation Program Reference System Report. The numbers were staggering. Each satellite: a photovoltaic array 5 km × 10 km, mass ~35,000 tons, output 5 gigawatts continuous. Constellation: sixty satellites in GEO, providing ~300 GW baseload — roughly half of U.S. peak demand in 1979. Downlink: 2.45 GHz microwave beam to a 10 km × 13 km rectenna on the ground, held under 23 mW/cm² (below the FCC exposure limit) with a phased-array pointing accuracy of 3 arcseconds. Rectenna DC-to-microwave conversion efficiency measured in the lab was already 85%.

The showstopper was launch. The Reference System required a heavy-lift vehicle putting 400+ tons to LEO at under $100/kg (1977 dollars). NASA's own HLLV concept was a fully reusable two-stage rocket dwarfing Saturn V. The Shuttle, then in development, was going to cost about $10,000/kg. Every "SPS is impossible" argument in 1979 reduced to we don't have that rocket.

In 1980 the National Academy of Sciences review concluded the program needed 20 more years of R&D at ~$1 trillion total. The incoming Reagan administration killed the DOE portion in 1981; NASA's died shortly after. Glaser's satellite constellation was defunded before a single kilogram flew.

Then the individual objections started falling:

• Launch cost. SpaceX Falcon Heavy is at ~$1,500/kg. Starship, if it hits its numbers, targets $100/kg or less — exactly the 1977 Reference System assumption.
• Photovoltaics. 1979 silicon cells: ~12% efficient, ~500 W/kg at panel level. Modern thin-film multi-junction cells: 34% efficient, 1000+ W/kg. Specific power has improved roughly 5×.
• Beaming. In June 2023, Caltech's MAPLE experiment aboard the SSPD-1 satellite transmitted power wirelessly in orbit and, for the first time, beamed a detectable microwave signal from space to a receiver on the Caltech rooftop. Small — milliwatts — but the physics was proven end-to-end.
• Political will elsewhere. JAXA has been funding SSPS research continuously since 1998 and demonstrated 1.8 kW transmission over 55 m in 2015. China's Bishan facility is targeting a GEO pilot in the early 2030s. ESA funded SOLARIS in 2022. AFRL's SSPIDR/Arachne is on the manifest.

What died in 1980 wasn't the physics — the physics was fine. What died was the launch economics. Forty-five years later, the launch economics are arriving, and every serious spacefaring nation is dusting off Glaser's 1968 proposal. The Reference System's core insight — that continuous baseload solar is a matter of altitude, not chemistry — was correct the whole time. It just needed a rocket nobody had yet built.