“I was leading the X-33 program, and we gave up on it because our assessment was that it would cost more than we were willing to spend, and we were at the limit of our technological capabilities to actually do it,” says Livingston Holder, an aerospace engineer, former USAF astronaut and X-33 program manager, and now CTO of Radian Aerospace, a Seattle-based company he co-founded in 2016 to revive the SSTO dream.
“Things have changed drastically since the X-33 — we have composite materials that are lighter, stronger and can withstand a greater thermal range than we had back then. And the propulsion is better than anything we had, in terms of how efficiently it burns propellant and how much the systems weigh,” he says.