A Seattle-area startup called Radian Aerospace is fine-tuning the design of its orbital space plane, with an eye toward building a subscale prototype as early as this year.
The company is also in the midst of a fresh round of fundraising, following up on $27.5 million in investment that was announced in 2022, according to Livingston Holder, Radian’s co-founder and chief technology officer. “That round will be larger,” Holder told GeekWire.
Over the past two years, Radian has made progress on an ambitious plan to create a reusable winged space plane that would be launched toward low Earth orbit by a rocket-propelled sled and its own rocket engines. The single-stage-to-orbit concept, or SSTO, has been called a “holy grail” for cheap access to space.
Holder knows the challenges well: In the 1990s, he was part of the Boeing team that was involved in an SSTO project for NASA called the X-33 — a project that was terminated in 2001. For more than a decade, Holder hung onto his hopes for the holy grail, and got his chance to renew the quest when he and other aerospace industry veterans founded Radian in 2016.
“Materials have improved significantly on the composite side,” he said. “There’s been a lot of learning. I’ve been around for a long time, but the learning is accelerating as we have more tools for analysis, and smarter people to do the analysis.”
The company’s space plane, dubbed Radian One, will be built out of carbon matrix composites and beefed up with a thermal protection system that’s already begun to undergo testing in partnership with NASA’s Glenn Research Center in Ohio. Radian One is designed to carry up to five crew members to low Earth orbit, with as much as 5,000 pounds of payload going up and 10,000 pounds going down.
The plans for Radian One’s propulsion system have been revised to go with methane and liquid oxygen as propellants, instead of the LOX-kerosene mix that had been previously planned. The earlier design had three rocket engines on the space plane, but the newly released design provides for five engines. Holder declined to specify how powerful those engines would be, except to say that they’d pack more than the 200,000 pounds of thrust specified in the earlier design. The engines are to be built in partnership with a company yet to be named publicly.
Three additional rocket engines on Radian One’s sled launcher would provide an initial push lasting roughly 20 seconds. When engines on the space plane near the end of their operating life, they could be swapped out for use on the sled. “We don’t have to have the tip-top performance of going all the way to orbit,” Holder explained. “It gives us a good way to use the older engines for that sled system.”
Radian’s first-generation rocket engines were tested at a facility in Bremerton, Wash., and Holder said that facility could be used for next-generation testing as well. Other Pacific Northwest connections have to do with carbon-composite construction: Holder said a prototype propellant tank was built using a robotic system at the University of Washington’s Advanced Composites Center, in partnership with Janicki Industries and Electroimpact.
Technically speaking, Radian considers Renton, Wash., to be its current base of operations — but its workforce is widely distributed. Holder said the company’s staff has risen to about two dozen, “and when we start looking at the subcontracts team and folks we’re leveraging, the headcount would go up to about 50 FTE [full-time-equivalent employees].”
Once Radian completes its next fundraising round, it’s likely to expand its footprint in the Seattle area. “We’re looking for a design experience center, where we’ll bring some of our larger hardware pieces together and start integrating that hardware,” Holder said.
Holder hinted that Radian’s work may not remain behind closed doors for long. “Something that will pop up on the horizon, probably a little bit later this year, is a prototype vehicle that we’re going to fly,” he said. “It’s a subscale unit. It’ll have the correct shape of our vehicle and will give us our first insight to the true flight characteristics of this system. It’s subsonic. It’s not going to be too fancy. But it’s a good learning opportunity for us.”
The company aims to put the full-scale Radian One through its first flight by 2030, which is prime time for NASA’s transition from the International Space Station to a new generation of commercial space stations. Those orbital outposts could include Axiom Station and Starlab — as well as Orbital Reef, a project planned by Jeff Bezos’ Blue Origin space venture, Sierra Space, Boeing and other partners. (For what it’s worth, one of the early investors in Radian was Dylan Taylor, chairman and CEO of Voyager Space, which is one of the partners in the Starlab space station project.)
Holder said Radian One could also play a part in Defense Department missions relating to intelligence, surveillance, reconnaissance and space domain awareness. The space plane concept is meant to support on-demand launch within 90 minutes, the capability to land on any runway that’s long enough, and a 48-hour mission turnaround time.
“It helps us quickly get a system in orbit that can observe something that may have just popped up on the world stage right away,” Holder explained.
Of course, Radian isn’t the only private venture going after the market for orbital transport. Better-known companies — such as SpaceX, Boeing and Lockheed Martin — are widely thought to have the inside track. But Holder argued that Radian Aerospace could still find a profitable niche in the future orbital ecosystem.
He pointed to the evolution of terrestrial transportation systems as a precedent. “When you build a building, you have big 18-wheelers that bring up large pieces, panel vans that bring up the sheetrock, and pickup trucks and automobiles that bring the workforce. All of these different elements are needed in the future space transportation architecture, because they each have a specific role to play,” he said.
“I think we’re more of a system that brings fewer workers and a little bit of the cargo, as opposed to the big infrastructure,” Holder said. “Once you get that big infrastructure up, you’re going to need folks to service it. So, you’re not going to drive an 18-wheeler to bring the work crew. You’ll bring us.”
