Rubicon Space Systems Delivers Green Propulsion System for NASA Mission

Rubicon Space Systems has successfully delivered the propulsion system for NASA's Green Propulsion Dual Mode (GPDM) technology demonstration mission, slated for launch in October. This mission will showcase both multimode propulsion—integrating chemical and electric thrusters—and ASCENT, the environmentally friendly propellant developed by the U.S. Air Force Research Laboratory.

The GPDM mission represents a significant step forward, marking the first combined chemical and electric propulsion system deployed in space and a pivotal test of ASCENT's capabilities. As Daniel Cavender, Rubicon director (a division of Plasma Processes), told SpaceNews, "It will be the first combined chemical and electric propulsion system in space and a key test of ASCENT."

NASA is evaluating ASCENT (Advanced Spacecraft Energetic Non-Toxic) due to its promise of a 50 percent increase in specific impulse density over hydrazine, alongside easier ground handling, as detailed in a NASA Marshall Space Flight Center briefing on GPDM.

Rubicon's ASCENT chemical propulsion module, dubbed Sprite, is integrated with Massachusetts Institute of Technology electrospray thrusters. These four electrospray thrusters, delivered to NASA in September, share Sprite's propellant tank, control valves, and feed system. The system is integrated into a six-unit cubesat.

The engineers involved learned from the challenges faced by NASA's Lunar Flashlight cubesat, which failed to reach lunar orbit in 2023 due to propellant line clogging. To prevent similar issues, Rubicon employed CT scanning to ensure Sprite's propellant lines were free of debris, and conducted a hot-fire test. Cavender noted, “We have certainly done our due diligence in addressing the FOD [foreign object debris] concern of Lunar Flashlight.”

This delivery is a crucial achievement for Huntsville, Alabama-based Rubicon. Cavender highlighted, “This is the first time that we’ve produced an integrated propulsion system. We’ve gone from being a component manufacturer to an integrated, functional product manufacturer.”

Cavender's experience with ASCENT dates back to the NASA Technology Demonstration Mission during the Green Propellant Infusion Mission (2019), where he also served as NASA Marshall’s Lunar Flashlight project manager. He emphasizes ASCENT's "big draw"—its specific impulse density. He explained, “For a small spacecraft that’s constrained on volume, you need higher efficiency to gain capability.”

ASCENT also offers significant safety advantages over hydrazine. Cavender stated, “you can fuel at your factory, you can fuel en route, you can fuel on the launch vehicle.”

The Defense Department also shows considerable interest in electrospray thrusters, as evidenced by the Defense Innovation Unit's October solicitation for proposals to further develop this technology, which generates thrust by accelerating charged particles.