Micro-Cathode Arc Thruster (μCAT) System Development

The objective of this project is to develop a highly reliable smallsat class micro propulsion guidance, navigation, and control (GN&C) actuator that will be used as a component of the Goddard science-class SmallSats. To achieve this objective, we will partner with the George Washington University to jointly advance the technology readiness level of their Micro-Cathode Arc Thruster (μCAT) system. A version of the μCAT, jointly developed by the GWU/GSFC team, will be flying on the CANYVAL-X cubesat mission in the summer of 2017. The system is a modified version of the 1^st test unit flown by USNA on the BRICSAT mission. These μCAT units are protoflight units intended to provide basic on-orbit performance data, but are not designed for reliable, long duration, precision applications. We propose to build upon the performance data collected during these flight demonstrations to develop a fully-functional, flight-ready μCAT that meets the specific needs of proposed Goddard science-class SmallSats. Specific goals of this research will be to improve reliability, thrust to power efficiency, scalable architectures for higher thrust levels, and precision of impulse bits. Our team will be leveraging our experience developing the CANYVAL-X unit and our relationship with GWU to develop a flight system to meet the needs of many proposed GSFC SmallSat missions.  

The μCAT is a novel variation of a vacuum arc thruster. The thruster exhaust is plasma, an ionized electrically neutral gas. The μCAT works similar to a spark plug creating an electric arc between an anode and cathode. The arc forms a localized region of high temperature plasma at the “cathode spot”. A magnetic coil is used to cause the cathode spot to follow a circular path along the circumference of the cathode, resulting in uniform burning of the cathode over the operational life. The electric arc ablates some of the material off the cathode as high velocity plasma providing efficient, low-thrust. Each charge-discharge pulse of the electric arc creates a plasma exhaust or “impulse bit”. Thrust levels are controlled by increasing or decreasing the number of pulses each second. μCAT protoflight units have ~1 mN impulse bit, and 25 mN thrust per head.

The μCAT is a scalable technology and thrusters can be utilized in point configurations or combined in various array configurations for primary propulsion. The μCAT propulsion system includes the thruster, an inductive power processing unit (PPU) and a control unit. The thruster geometry is a simple concentric design using a spring-driven cathode feed, making it highly reliable and efficient. The cathode is the propellant, and can be any conductive or even semi-conductive material. Using the cathode as propellant reduces thruster mass and eliminates build-up of discharge by-products associated with other vacuum arc propulsion technologies. Continuous thruster tests over several weeks indicate a cathode of 6cm length operating at 10 pulses-per-second would last about a year.

The following tasks will be required for this effort

• Task 1: Develop scalable and efficient μCAT architectures that can be easily customized to meet performance requirements for proposed SmallSat constellation, and precision formation flying (PFF) design reference missions (DRM). For DSM-PFF this will include precision low-thrust for maneuvering, precision alignment, and formation acquisition and control in planned Earth orbit and deep space regimes.
• Task 2: Develop a reliable, fully functional, scalable, and configurable μCAT system to meet requirement of various DRM.  Long life and high radiation environment capability with be investigated.
• Task 3: Environmental testing and thrust performance characterization of μCAT system.
• Task 4: Investigate methods to improve the thrust to power efficiency