Two-Fault Tolerant Cold Gas Propulsion System for Spacecraft-Inspection CubeSat

Abstract

The Human/Robotics/Vehicle Integration and Performance Lab at the University of California, Davis is developing a 3U CubeSat to autonomously inspect the exterior of a spacecraft. The CubeSat will be propelled by a cold gas propulsion system specifically designed to meet stringent safety and reliability standards set by NASA in order to operate near high-value targets such as the International Space Station. Multi-staged valves provide two-fault tolerance while the corresponding plenum stages mitigate the amount of uncontrolled impulse upon valve-open failure. Initial tests of a 3D printed plenum design demonstrate the ability to use commercial off-the-shelf 3D printer technology to rapidly construct pressure vessels capable of storing gas well above 100 psig before failing. Preliminary test results of a 0.6 mm nozzle supplied with CO2 at 100 psig show good agreement with theoretical models for steady-state mass flow rate and dynamic pressure changes. Startup flow was unexpectedly low, so further work must be done to characterize and model the startup characteristics for a single plenum discharge.