Colloid Micro-Newton Thrusters for the space technology 7 mission

Abstract

Two flight-qualified clusters of four Colloid Micro-Newton Thruster (CMNT) systems have been delivered to the Jet Propulsion Laboratory (JPL) and subsequently delivered to ESA for spacecraft integration. The clusters will provide precise spacecraft control for the drag-free technology demonstration mission, Space Technology 7 (ST7). The ST7 mission is sponsored by the NASA New Millennium Program and will demonstrate precision formation flying technologies for future missions such as the Laser Interferometer Space Antenna (LISA) mission. The ST7 disturbance reduction system (DRS) is a payload on the ESA LISA Pathfinder spacecraft along with the European gravitational reference sensor (GRS) as part of the ESA LISA Technology Package (LTP). To achieve the nanometer-level precision spacecraft control requirements, each of eight thruster systems is required to provide thrust between 5 and 30 µN with resolution ≤0.1 µN and thrust noise ≤0.1 µN/vHz. Developed by Busek Co. Inc., with support from JPL in design and testing, the CMNT has been developed over the last six years into a flight-ready and flight-qualified microthruster system, the first of its kind. Recent flight-unit qualification tests have included vibration and thermal vacuum environmental testing, as well as performance verification and acceptance tests. All tests have been completed successfully prior to delivery to JPL. Delivery of the first flight unit occurred in February of 2008 with the second unit following in May of 2008. Since arrival at JPL, the units have successfully passed through mass distribution, magnetic, and EMI/EMC measurements and tests as part of the integration and test (I&T) activities including the integrated avionics unit (IAU). Flight software sequences have been tested and validated with the full flight DRS instrument successfully to the extent possible in ground testing, including full functional and 72 hour autonomous operations tests. In the summer of 2009 the cluster assemblies were delivered to ESA along with the IAU for integration into the LISA Pathfinder spacecraft. Spacecraft-level testing will include magnetics, acoustic, and thermal vacuum environmental testing with a planned launch and flight demonstration in April 2012. 1 2