Can solar power be beamed down from space? Yes. Is it commercially viable? Not yet

Caltech looks back on the highs and lows of the SSPD-1 project

A year after the launch of the Space Solar Power Demonstrator (SSPD-1), the California Institute of Technology (Caltech) is revealing the highs and lows of the mission.

SSPD-1 was the first space-borne prototype from Caltech's Space Solar Power Project (SSPP) and was designed to show that taking solar power gathered in orbit and transmitting it back to Earth was not just a concept popular with science fiction authors.

The testbed stopped communications with Earth on November 11, and while a commercially viable concept is still some way off, SSPD-1 has demonstrated that it does actually work.

Scientists used the Microwave Array for Power Transfer Low-orbit Experiment (MAPLE) to beam power back to Earth and to receivers in orbit. The hope is that one day, a constellation of spacecraft could turn sunlight into energy, convert it to microwaves, and transmit it to wherever it is needed.

In 2022, ESA conducted a study into space power and concluded that while the concept could work, the size and complexity – not least because of the need for technology that doesn't yet exist – made the project prohibitively expensive.

Other experiments onboard included the Deployable on-Orbit ultralight Composite Experiment (DOLCE), a 1.8 x 1.8-meter structure intended to demonstrate the architecture and packaging of technology that might go on to make up a kilometer-scale orbital power station constellation, and ALBA, a collection of 32 different types of photovoltaic cells for research into what works best in space.

DOLCE did not go exactly as planned. First, one of the wires in the deployment mechanism snagged, damaging the structure. Scientists resolved this by directly exposing the system to sunlight for warming.

Then another part of the structure jammed, requiring scientists to use DOLCE's actuators to clear the jam. Caltech said: "Lessons from the experience … will inform the next deployment mechanism."

Glitches aside, it's all been a tremendous success and a credit to the engineers and scientists involved.

"Solar power beamed from space at commercial rates, lighting the globe, is still a future prospect. But this critical mission demonstrated that it should be an achievable future," said Caltech President Thomas F Rosenbaum, the Sonja and William Davidow Presidential Chair and professor of physics.

The mission was partly funded by billionaire philanthropist Donald Bren, inspired by an article in Popular Science on the potential of space solar power. Northrop Grumman also contributed $12.5 million between 2014 and 2017 through a sponsored research agreement.

Bren said: "The hard work and dedication of the brilliant scien­tists at Caltech have advanced our dream of providing the world with abundant, reliable, and affordable power for the benefit of all humankind."

Noble words, although we can imagine that astronomers would be not happy with yet another constellation in orbit, playing havoc with their telescopes. Particularly one described as "kilometer-scale." ®

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