Satellites in space harvesting sunlight and transforming solar energy into usable energy for applications on Earth is an idea that has been studied for decades. But even though the United States was a pioneer in this technology, government interest in taking it from the laboratory to orbit has been lukewarm at best.
The US military is now trying to revive the effort. The Naval Research Laboratory launched an experiment in 2020 aboard the Air Force’s X-37B spaceplane that successfully tested hardware to capture sunlight and convert it to direct current electrical power.
The NRL experiment, however, was only a demonstration in space and was not intended to return the power captured in space to the ground. This capability will be attempted by the Air Force Research Laboratory, if all goes as planned, in a $100 million experiment slated for launch in 2025.
The AFRL’s mission, dubbed Arachne, was designed in response to a military logistical challenge: securing reliable energy sources on austere bases devoid of infrastructure. Today, the fuel used to operate field generators must be transported by truck, turning these convoys into targets for adversaries. AFRL believes that access to solar power from space could help reduce this vulnerability.
The lab also argues that increased government support for this technology would send a signal to commercial industry and investors, which would expand market opportunities.
“Like the Global Positioning System, which started as a military asset and evolved into a technology now used by people all over the world, this solar energy radiation system could transition to wider use, providing solar power regardless of weather, time of day or latitude,” AFRL said.
Arachne took a leap forward last month when AFRL and Northrop Grumman engineers at a lab in Linthicum, Maryland demonstrated a so-called “sandwich tile.”
The tile is an essential element that allows the collection and conversion of energy, explained James Winter, AFRL program manager. One side of the slab has a panel of photovoltaic cells that receive solar energy. The electronics in the middle convert direct current into radio frequency signals, and the other side of the tile has an antenna to transmit the power.
Now that the tile has been demonstrated, Winter said, the next step will be to figure out how to encapsulate a set of nine tiles in a rocket fairing so it can be launched into orbit on a Northrop Grumman ESPAStar – a bus that can roll. as a secondary payload on large national security rockets. Once the satellite is deployed, the RF energy will be transmitted to a receiving station on the ground, and a rectifier antenna will then convert the RF into usable power.
Winter said the 2020 experience aboard the X-37B provided useful information about the sandwich module, which is applied to Arachne.
Jay Patel, vice president of remote sensing programs at Northrop Grumman, pointed out that photovoltaic and RF conversions are well-understood technologies. “But what we’ve been able to do is translate them into the environment we want them to operate in,” he added. “Arachne isn’t much of an invention, but an innovation in how we translate some of these proven technologies into a mission that’s really going to open up different avenues.”
Space solar power received a major endorsement in a November report released by the US Space Force, Defense Innovation Unit and AFRL. “Integrating space-based solar power into the U.S. space and climate agenda could not only provide another arrow in the quiver to fight climate change, but provide new ways to engage industry, the public and international partners,” the report said.
But despite military advocacy and technological advances, space solar power is facing a surge.
“Proponents described it as the smartest, most comprehensive energy solution available, while detractors saw it as an incredibly expensive program that will never work,” Aerospace Corp noted. in a recent study.
As is usually the case with these arguments, the reality lies somewhere in between. But as scientists working on the Arachne mission point out, we will never know the true potential of this technology until the United States invests enough resources to discover it.
Sandra Erwin covers military space for SpaceNews. She is a veteran national security reporter and former editor of National Defense magazine.
“On National Security” appears in every issue of SpaceNews magazine. This column originally appeared in the January 2022 issue.
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