On Sept. 17, a small vehicle lifted off under rocket power at a test site in Washington state. It rose to an altitude of nearly 10 meters, hovered, then descended to a landing, concluding a 15-second flight.
The short flight was a big milestone for startup Stoke Space. That vehicle, called Hopper2, was a prototype for the upper stage of a reusable launch vehicle, and the company called the flight the “icing on the cake” of a successful test campaign. “It was kind of the last, final thing to do,” said Andy Lapsa, chief executive of Stoke Space.
Hopper2 is also the latest vehicle that can trace its lineage back 30 years to Delta Clipper Experimental, or DC-X, a vehicle built by McDonnell Douglas for the Strategic Defense Initiative Organization. In August 1993, DC-X lifted off and landed vertically under rocket power at White Sands, New Mexico, demonstrating the feasibility of vertical landings.
The DC-X kicked off a wave of interest in reusable launch vehicles by space advocates and entrepreneurs at a time when NASA was focused on flying the shuttle and the Air Force on developing a new generation of expendable rockets. New ventures announced plans to develop reusable vehicles inspired either directly by the DC-X or, more generally, by its vision of rapidly reusable launch. Most of those efforts, including NASA’s own X-33 and X-34 programs, didn’t get very far at the time.
Among those inspired by the DC-X was Dave Masten, who founded Masten Space Systems two decades ago to work on vertical-takeoff, vertical-landing rockets. Over the years, the company developed vehicles that performed hundreds of low-altitude test flights, winning a NASA prize competition in the process. But the company ran into financial problems trying to build a lunar lander for NASA and filed for Chapter 11 bankruptcy last year.
That company’s vehicles — and Masten himself — are back. Astrobotic bought Masten Space Systems’ assets, repurposing them as its new Propulsion and Test Department. Xodiac, a vehicle that had performed more than 100 flights before the bankruptcy, returned to flight in September, beginning a new campaign of test flights for NASA and other customers.
Dave Masten, now chief engineer of Astrobotic’s Propulsion and Test Department, said they have picked up where they have left off with Xodiac before the bankruptcy. “We’re pretty much back to flying it, maintaining it, flying it again,” he said. Work has also resumed on a larger vehicle, Xogdor.
“In some ways, we’ve done a lot more than I’ve expected,” he said, looking back on the last 20 years, “and in other ways, we’re not where I had hoped to be.”
One of Masten’s biggest contributions might have been influencing Elon Musk. After seeing a video of a Masten flight where the vehicle turned off and then reignited its rocket engine in flight, Musk forwarded the video to SpaceX engineers with a question: “Why can’t we do this?” Not long after that, the company started working on propulsive landings of Falcon 9 boosters, said Masten, who heard that account from people within SpaceX.
That changed the trajectory of spaceflight. SpaceX eventually mastered the ability to land boosters and reuse them — the current record is 17 flights — enabling a much higher launch rate at lower costs. Others are pursuing the same approach, from Blue Origin and Rocket Lab to Relativity Space and Stoke Space.
All that links back to the DC-X. Dave Masten attended a recent 30th anniversary reunion of the DC-X team, and he said those who worked on that program are happy about what SpaceX and others have now achieved with vertical landings and reuse. “I think everybody’s really excited to see that we’re reusing that technology and that it’s becoming more commonplace.”
And there is still a thrill, as there was 30 years ago, of seeing a rocket take off and land, as Stoke Space’s Lapsa said of seeing Hopper2’s brief flight. “There is a very real emotional crescendo to a program like this to actually go and fly.”
This article originally appeared in the October 2023 issue of SpaceNews magazine.
