On Saturday the The U.S. Air Force is expected to launch its secret X-37B spacecraft for a long-term mission in near-Earth orbit. The robot orbiter looks like a smaller version of the space shuttle and has spent almost eight years in space in the past 10 years trying to carry out classified experiments for the military. Almost nothing is known about what the X-37B is doing up there, but before its sixth launch, the Air Force released some rare details about its cargo.
In addition to its usual suite of secret military technologies, the X-37B will perform some unclassified experiments while in space. NASA is sending two experiments to study the effects of radiation on seeds, and the U.S. Air Force Academy is using the spacecraft to deploy a small research satellite. However, the real star of the show is a small solar panel that was developed by the physicists of the Naval Research Lab and with which the first orbital experiment with space-based solar energy is carried out.
“This is a big step forward,”
Space-based solar energy is about bringing solar energy to earth regardless of the weather and time of day. The basic idea is to convert the solar energy into microwaves and radiate it downwards. In contrast to terrestrial solar collectors, satellites in a sufficiently high orbit may only experience darkness for a few minutes a day. If this energy could be captured, it could be an inexhaustible source of energy no matter where you are on the planet.
This idea was invented by science fiction author Isaac Asimov in the 1940s. Since then, beam power experiments have been successfully tested on Earth several times. However, the X-37B experiment will be the first time that the core technologies behind microwave solar energy will be tested in orbit.
“The science of microwave power radiation is fully understood. The technical challenges of scaling known technologies to an unprecedented size in orbit are what we need to advance, ”said Ian Cash, director of the International Electric Company Limited, which is developing a space solar platform called CASSIOPeiA. “But every undertaking has to start with a first step.”
He calls the experiment that Jaffe and his colleagues at the NRL created a “sandwich” module. It is a three-stage system for converting sunlight into electricity and then converting electricity into microwaves. Typically, the conversion system is located between a high performance solar panel and the antenna used for power transmission. But for this mission, Jaffe and his colleagues will not radiate the energy from space to Earth because the radio signal would interfere with other experiments at the spatial level. Instead, the sandwich module sends the radio signals over a cable so that researchers at the NRL can examine the system’s performance.
The entire NRL experiment could fit into a pizza box and not produce enough energy to power a light bulb. However, according to Jaffe, the experiment is a crucial step towards a free-flying space-based energy satellite. “A lot of work was done on studies and analyzes and much less on the actual prototyping,” says Jaffe. “This is not necessarily the most sophisticated version of what could be achieved, but the main goal was to get into space with a proof of concept.”