Alternative solid hydrocarbons as propellants for electrothermal plasma radio-frequency thrusters

Area of Science:

• Spacecraft Propulsion
• Plasma Physics
• Materials Science

Background:

• Onboard propulsion is crucial for extending CubeSat mission durations.
• Existing electrothermal plasma thrusters primarily use gaseous propellants.
• Solid propellants remain largely unexplored for this application.

Purpose of the Study:

• Investigate the thrust performance of solid hydrocarbon propellants.
• Evaluate naphthalene, adamantane, camphor, and borneol in an RF electrothermal thruster.
• Benchmark solid propellant performance against gaseous argon.

Main Methods:

• Utilized a prototype radio-frequency (RF) electrothermal thruster.
• Conducted direct thrust measurements using a calibrated thrust balance.
• Tested propellants in both unpowered (cold-gas) and powered (plasma) modes.

Main Results:

• Solid propellants yielded lower cold-gas thrust due to lower exhaust velocities.
• Plasma thrust significantly increased due to molecular dissociation and RF heating.
• Achieved up to 1.1 mN thrust and 37 s specific impulse at ~45 W RF power.

Conclusions:

• Sublimating solid propellants are a viable alternative for CubeSat propulsion.
• Solid propellants offer comparable performance to argon without complex storage.
• This approach is suitable for mass- and volume-constrained missions.