X-37B testing beamed solar power from space

The U.S. Space Force’s X-37B mini-shuttle, presently in orbit for more than 300 days, is testing technology for capturing solar energy and beaming it back to Earth for use in the electricity grid.

Most of the robotic space drone’s duties on this mission, known as Orbital Test Vehicle-6 (OTV-6), are a tightly held secret. However, one known bit of research that the craft carries is the Photovoltaic Radio-frequency Antenna Module Flight Experiment, or PRAM-FX.

PRAM-FX is a Naval Research Laboratory (NRL) experiment that’s investigating transforming solar power into radio frequency (RF) microwave energy. PRAM-FX is a 12-inch (30.5 centimeters) square tile that collects solar energy and converts it to RF power.

Paul Jaffe, the innovation power beaming and space solar portfolio lead at NRL, said that PRAM-FX is not beaming microwave energy anywhere. Rather, the experiment is gauging the performance of sunlight-to-microwave conversion. To be measured is how the PRAM is performing from an efficiency standpoint and also from a thermal performance stance, he said.

The first results from PRAM were released in January, and showed an “8% total module efficiency,” which I think means it was able to beam down 8% of the solar energy that it gathered. This might seem poor, but if solar panels can provide that much of their energy for Earth use the pay-off could be quite large.

A much larger demonstration project will fly three different spacecraft in ’23 and ’24, each testing different components of the system.