US military tests space-based solar power device

Pentagon project is part of a race to build satellites that can beam energy to anywhere on Earth

Emissions from a coal-fired power plant are silhouetted against the setting sun, Monday, Feb. 1, 2021, in Independence, Mo. A United Nations report released on Thursday, Feb. 18, 2021 says humans are making Earth a broken and increasingly unlivable planet through climate change, biodiversity loss and pollution. So the world must make dramatic changes to society, economics and daily life. (AP Photo/Charlie Riedel)
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Scientists at the Pentagon tested a prototype solar device that could one day allow energy harvested in space to be beamed back to Earth.
The device, called the Photovoltaic Radio-frequency Antenna Module (Pram), was sent from the Pentagon's X-37B drone, a reusable unmanned spacecraft shrouded in secrecy.

Pram is currently orbiting Earth once every 90 minutes and is able to capture sunlight before it diffuses in the planet's atmosphere, making it much more effective at generating electricity than a terrestrial device.

"We're getting a tonne of extra sunlight in space just because of that," one of the project's developers, Paul Jaffe, told CNN.
Despite being the size of a pizza box, the test panel has so far been able to generate about 10 watts of energy, roughly the amount needed to power a tablet.
Once the stuff of science fiction, scientists hope the technology could one day be developed to power entire cities.
"The next logical step is to scale it up to a larger area that collects more sunlight," Mr Jaffe said.

"Some visions have space solar matching or exceeding the largest power plants today, multiple gigawatts, so enough for a city."
Solar energy collected in space could be sent to Earth as microwave or laser beams before being converted into usable electricity.

The technology could one day be used to send power to areas where it is badly needed, providing a possible solution during natural disasters or widespread power cuts such as those seen in Texas in recent weeks.
"The unique advantage the solar power satellites have over any other source of power is this global transmissibility," Mr Jaffe said.

"You can send power to Chicago and a fraction of a second later, if you needed to, send it instead to London or Brasilia."

The falling cost of sending objects into space is helping to bring ambitious projects within reach and the race is on to develop the first solar power system in space.

China plans to build a solar power station in space by 2035, and Japan's space agency, Jaxa, has been developing a space-based solar power system since 1998.
In 2015, Jaxa began testing the wireless transmission of power by microwaves and sent 1.8 kilowatts of power over a distance of more than 50 metres.
Nasa has been investigating ways to build an orbital solar power station since the 1970s, including whether one could be built using materials gathered from the Moon or mined from an asteroid.
Private companies are also in contention. On Wednesday, space infrastructure company Redwire announced it had acquired Deployable Space Systems, one of the world's leading suppliers of solar arrays for spacecraft, highlighting the growing interest in the technology.
With militaries around the world backing testing efforts, scientists are keen to make clear that fears of a Death Star-style weapon are unfounded.
Mr Jaffe said that turning solar energy gathered in orbit into a weapon would be "exceedingly difficult, if not impossible".