Electrospray-Based Propulsive De-Orbit Module

ABSTRACT: Busek has successfully demonstrated key technical features of an autonomous, long-term storable, radiation tolerant propulsion module with no moving parts that is suitable for deorbiting small spacecraft. Critical properties of a new, high melting point, ionic liquid propellant were measured, confirming it as an excellent candidate for use in electrospray thrusters. The electrospray propellant selected was then operated in a 100µN-class electrospray thruster developed by Busek. Schematics were generated for an analog-based thruster fire control system and critical features, such as orbital and thruster fire timers, and pointing sensors, were validated. As part of the Phase II effort, Busek shall continue development of the deorbit module advanced under the Phase I. Additional thruster configurations will be tested for best performance, and a prototype thruster deliverable shall be fabricated, loaded, and delivered for additional testing. Remaining electronics for initiating and executing the deorbit maneuver will be fabricated and tested. The various subsystems shall be integrated to perform a single degree-of-freedom demonstration that includes: two 100µN-class electrospray thrusters, sun tracker, and breadboard control electronics. After the single axis validation test, mechanical designs shall be produced for the final deorbit module concept. BENEFIT: International consensus is forming around the need for orbital debris management, which poses risks to functioning space assets. It is likely that in the near future, international agreements will require provisions in spacecraft design to reposition satellites to disposal orbits, or to completely deorbit them. In recognition of this, legal frameworks developed by the United Nations and DoD Instruction 3100.12 (Space Support) require satellites in low earth orbit to de-orbit in fewer than 25 years. The propulsion system proposed here provides key features necessary to endure extended on-station storage and subsequent thruster firing for spacecraft deorbiting at the end of life. In addition to use as a deorbiting propulsion system, the electrospray thruster advanced here is applicable to primary and ACS propulsion on small satellites, and CubeSats in particular. The system has no moving parts, or pressurized propellant, and poses little risk to primary payloads when launched as a secondary payload. The propellant is stored as a solid during launch and is not a leakage risk. Furthermore, the lack of mechanisms enables significant miniaturization, enabling a high-deltaV propulsion system that resides within a fraction of a 1U CubeSat module.