Starfire (Direct Fusion Drive)
A compact fusion reactor design that would generate electricity for a spacecraft and also heat propellant into thrust, aimed at faster missions to the outer planets, Mars and beyond. It is a research program, not yet flight hardware.
Why it matters
Missions to the outer planets now take many years. PSS says an engine that delivered both thrust and megawatts of power would shorten trips and carry more science, and its NASA study described a Pluto orbiter and lander arriving in about 4 years.
How the technology works
Starfire builds on the Princeton Field-Reversed Configuration reactor developed at the Princeton Plasma Physics Lab. Propellant flows through the cooler outer layer of plasma around the hot fusion core (the scrape-off layer), picks up heat, and leaves through a magnetic nozzle to make thrust; the core also supplies electrical power.
PSS lists NASA NIAC and ARPA-E fusion awards among its government work.
Sources
Updated Oct 22, 2026 · How we source facts · Suggest a correction