The Phase Four Radio Frequency Thruster

Phase Four’s Maxwell propulsion systems rely on our proprietary radio frequency thruster (RFT) technology, which is designed with simplicity and mass-manufacturability in mind, to rise to the challenge of large constellations of satellites.

RF Thruster Performance Envelope

Maximum Thrust Point 33.7 mN 425 W
Maximum Specific Impulse Point 820 s 431 W

The Phase Four RFT operates by using RF electromagnetic fields to energize a plasma. A permanent magnet array surrounding the antenna-liner generates magnetic fields that direct the hot plasma out of the thruster, converting the kinetic energy of the plasma into thrust. This simple mechanism eliminates the high voltage electronics and electrodes that are challenging to manufacture in large quantities for traditional plasma thruster systems. Furthermore, the RFT is robust enough to be used with myriad propellants and has been tested on xenon, krypton, iodine, water vapor, nitrogen, oxygen and several other exciting advanced propellants. These innovations enable significant reductions in lead time and materials cost compared to legacy electric propulsion technologies like Hall Effect Thrusters. Furthermore, development of the RFT on advanced propellants can unlock currently impossible mission possibilities from very low Earth orbit to deep space exploration.

RF Thruster operational diagram
RF Thruster operational diagram
A 2nd gen RFT being manufactured for Phase Four’s Maxwell Block 2 engine

Photo: A 2nd generation RFT being manufactured for Phase Four’s Maxwell Block 2 Engine

2nd Gen RF Thruster firing in one of Phase Four’s R&D vacuum chambers
2nd Gen RF Thruster firing in one of Phase Four’s R&D vacuum chambers

In addition to propellant flexibility and ease of manufacturability, another unique aspect of the RFT is that it can maintain a stable plasma discharge across orders of magnitude of power and propellant flow rate. This gives the thruster a very broad performance envelope, compared to high voltage DC plasma thrusters. The Gen 2 RFT peak thrust and specific impulse points are shown in the table above. These points are only limited currently by our ground test hardware, not the physical limits of the thruster. Ultimately, this technology will unlock the ability for spacecraft operators to use a single thruster at very high thrust modes, very high specific impulse modes, and all the points in between, without needing multiple thruster technologies and different propellants.

*Intellectual Property Notice: The systems and processes discussed and disclosed herein are covered by one or all of the following patents: U.S. Pat. No. 11,067,065 and U.S. Pat. No. 11,231,023. Other systems and processes are patent pending in the U.S. and E.P.O.