Experimental Characterization of an NO 2 -Seeded Argon Laser-Thermal Thruster Powered by a Fiber Laser

Conventional propulsion falls short of the performance required for rapid interplanetary transits. Laser-thermal propulsion (LTP) is a promising candidate for such missions, utilizing laser energy from a ground- or orbit-based array to heat a propellant via laser-sustained plasma (LSP), generating both high thrust and high specific impulse. Propellant seeding with nitrogen dioxide (NO₂) is proposed as a solution to the fundamental problem of radiation loss in LTP systems. An experimental apparatus for a laboratory-scale NO₂-seeded argon laser-thermal thruster powered by a 300-W continuous-wave (CW), 3-kW quasi-continuous-wave (QCW) 1.07 μm fiber-optic laser is implemented and validated with direct pressure and thrust diagnostics. In the static configuration, a more than twofold gain in thermal efficiency is achieved with a 5% NO₂ partial pressure, from 14.7% in pure argon to 31.7% in seeded argon. In the flowing configuration, no improvement in performance is observed between the control and seeded cases due to the compact thruster geometry. With an achieved thermal efficiency of 33.0% and specific impulse of 39.0 s in pure argon providing a baseline, avenues to demonstrate gains in thruster performance in flowing CW operation with NO₂-seeded argon are presented.