A Solar-Powered Rocket Might Be Our Ticket to Interstellar Space

It might not sound like much, but Benkoski and his team just demonstrated solar thermal propulsion, a previously theoretical type of rocket engine that is powered by the sun’s heat. They think it could be the key to interstellar exploration.“It’s really easy for someone to dismiss the idea and say, ‘On the back of an envelope, it looks great, but if you actually build it, you're never going to get those theoretical numbers,’” says Benkoski, a materials scientist at the Applied Physics Laboratory and the leader of the team working on a solar thermal propulsion system. In APL’s mission design, the interstellar probe would pass just a million miles from its roiling surface.To put this in perspective, by the time NASA’s Parker Solar Probe makes its closest approach in 2025, it will be within 4 million miles of the sun’s surface and booking it at nearly 430,000 miles per hour. That’s more than hot enough to melt through the Parker Solar Probe’s heat shield, so Cheikh’s team at NASA found new materials that could be coated on the outside to reflect away thermal energy. But it’s also bad because we don’t have a lot of options.”The big takeaway from his research, says Cheikh, is there’s a lot of testing that needs to be done on heat shield materials before a solar thermal rocket is sent around the sun. But the important thing, says Benkoski, is that the data from the low temperature experiments matched the models that predict how an interstellar probe would perform on its actual mission once adjustments are made for the different materials. And now the second step is we start to substitute each of these components with the stuff that you would put on a real spacecraft for an Oberth maneuver,” Benkoski says.The concept has a long way to go before it’s ready to be used on a mission—and with only a year left in the Interstellar Probe study, there’s not enough time to launch a small satellite to do experiments in low Earth orbit.