A pulsed plasma thruster (PPT) or as a plasma jet engine (PJE), is a form of electric spacecraft propulsion. PPTs are generally considered the simplest form of electric spacecraft propulsion and were the first form of electric propulsion to be flown in space, having flown on two Soviet probes (Zond 2 and Zond 3) starting in 1964. PPTs are generally flown on spacecraft with a surplus of electricity from abundantly available solar energy.
Pulsed Plasma Thrusters (PPT's) are not to be confused with the Pulsed Plasma Rocket (PPR) developed by Howe Industries, as the PPT is an electric propulsion system and the PPR is a nuclear propulsion system which uses a significantly different approach.
Operation
thumb|Schematic layout of a Pulsed Plasma Thruster
Most PPTs use a solid material (normally PTFE, more commonly known as Teflon) for propellant, although very few use liquid or gaseous propellants. The first stage in PPT operation involves an arc of electricity passing through the fuel, causing ablation and sublimation of the fuel. The heat generated by this arc causes the resultant gas to turn into plasma, thereby creating a charged gas cloud. Due to the force of the ablation, the plasma is propelled at low speed between two charged plates (an anode and cathode). Since the plasma is charged, the fuel effectively completes the circuit between the two plates, allowing a current to flow through the plasma. This flow of electrons generates a strong electromagnetic field which then exerts a Lorentz force on the plasma, accelerating the plasma out of the PPT exhaust at high velocity. By varying the time between each capacitor discharge, the thrust and power draw of the PPT can be varied allowing versatile use of the system. has been developed by CU Aerospace, L.L.C. on NASA Small Business Innovative Research (SBIR) funds and demonstrated to have an I<sub>SP</sub> > 3,500 s.
Advantages and disadvantages
PPTs are very robust due to their inherently simple design (relative to other electric spacecraft propulsion techniques). As an electric propulsion system, PPTs benefit from reduced fuel consumption compared to traditional chemical rockets, reducing launch mass and therefore launch costs, as well as high specific impulse improving performance.
A PPT was flown by NASA in November, 2000, as a flight experiment on the Earth Observing-1 spacecraft. The thrusters successfully demonstrated the ability to perform roll control on the spacecraft and demonstrated that the electromagnetic interference from the pulsed plasma did not affect other spacecraft systems.
An FPPT flight unit was qualified and integrated into CU Aerospace’s NASA-funded Dual Propulsion Experiment (“DUPLEX”) Subsequent in-space demonstration of the CU Aerospace FPPT-Fiber-fed Pulsed Plasma Thruster and MVP-Monofilament Vaporization Propulsion Thruster technologies is scheduled for early November 2025.
See also
- Vacuum arc thruster
- Rocket propulsion technologies (disambiguation)