SAN FRANCISCO - Rubicon Space Systems has emerged from the fiery trials of hot-fire testing with its Velox 5-newton ASCENT monopropellant thruster, which means it's now ready for the real heat: production and, eventually, actual spaceflight. The company announced that the thruster is moving into flight production, with on-orbit operations slated for 2027.
“The program demonstrated performance beyond our design objectives,” Rubicon Director Daniel Cavender told SpaceNews, in the way test directors do when they've just watched something not explode. “We are now transitioning the thruster into flight production.”
The Velox thruster, which runs on ASCENT - a hydrazine replacement that's about as exciting as propellants get - was put through its paces in Rubicon's vacuum altitude test chamber in Huntsville, Alabama. Over the course of weeks, the team tested it across feed pressures from 25% above nominal down to 25% of nominal, and duty cycles from 1% to 100%. Cavender reported that they now know exactly where the thruster's performance margins are, where its behavior begins to change, and what to expect as it accumulates life - which is more than most of us can say about our own aging processes.
With the testing campaign wrapped up, Rubicon is moving the Velox into production for three undisclosed customers - because who doesn't love a little mystery with their spacecraft hardware? The first delivery is scheduled for early 2027, with a flight later that year, and additional flights are planned for 2028.
Through the hot-fire testing, Rubicon qualified the thruster for nearly 14 kilograms of propellant throughput. "From what's been publicly reported, no other manufacturer has demonstrated this much throughput in a 5-newton class or 1-newton class ASCENT monopropellant thruster," Cavender said, adding that every extra kilogram of propellant translates to more mission capability and flexibility. So, basically, their thruster can go the distance - or at least keep burning longer than the competition.
ASCENT, which stands for Advanced Spacecraft Energetic Non-Toxic Propellant, is nearly 50% more dense than hydrazine, giving it a clear advantage in the density department. Rubicon's testing showed a specific impulse of 255 seconds, which is nearly 10% higher than any hydrazine thruster. This combination of high throughput and high performance, Cavender noted, will enable "mission capability beyond what you could do with current state-of-the-art hydrazine." Cavender would know, having worked on ASCENT missions in previous roles at NASA.
ASCENT was developed by the U.S. Air Force Research Laboratory in the 1990s, so it's been kicking around for a while, but it's finally getting its moment in the spotlight. Rubicon also snagged a NASA contract in 2025 to develop a 110-newton ASCENT thruster prototype, and the company has already delivered the propulsion system for NASA's Green Propulsion Dual Mode technology demonstration mission, which is scheduled to launch later this year.
Rubicon, founded in 2022, is a division of Plasma Processes. So, if you're keeping track: a young company, a non-toxic propellant, and a whole lot of hot gas - what could possibly go wrong?