Description: In cooperation with ROCCOR LLC, Busek seeks to develop thruster heads integrated with deployable booms. The high resolution, low quiescence and extreme throttling capabilities of Busek electrospray propulsion, combined with the customizable moment arms afforded by ROCCORs compact deployables will ensure the system is applicable to a wide variety of mission concepts. A preliminary performance map was obtained for the BET-1mN thruster, demonstrating hundreds’ of µN’s of thrust from a single emitter. Time of flight measurements indicated mixed mode operation (droplets/ions), indicating that updated thrust control algorithms may be necessary, as present implementations focus on droplet or ion dominated emission. Thrust modulations were demonstrated via control of flow rate and beam voltage, demonstrating deep throttling and operation over a wide range of conditions. Size, Weight, and Power (SWaP) for two integrated BET-1mN thruster systems were provided to the ROCCOR LLC and used to develop requirements for the boom. A notional 2m deployable boom design was developed and static load modeling performed to identify deflection. Under the Phase II effort, Busek shall update test setups to include in-situ mass flow measurement during direct thrust measurement in order to fully assess thruster performance. Additional thruster characterization shall focus on completing parameterized thruster performance while also measuring thrust noise, stability, and capturing electrospray plume sweeps. Updated thrust control algorithms will be implemented in hardware/firmware and commanded thrust control demonstrated as part of an integrated test with the BET-1mN thruster. Deployable boom requirements will be updated and a prototype boom fabricated and tested. Static load testing will be performed to validate Phase I modeling results.

Benefits: The proposed technology has numerous applications NASA missions improving both scientific and practical capabilities. Precision pointing applications include astronomical science objectives, such as exoplanet observations or other space-telescopes, laser communications and space situational awareness. In all cases, the greatly improved pointing over existing SoA (e.g reaction wheels) afforded by the proposed technology would both enhance pointing accuracy/stability and reduce the need for complex vibration and control accuracy mitigation strategies such as the use of active optics (e.g. fast steering mirrors). Laser communication benefits are particularly relevant with active NASA programs pursuing, for example, optical communication for Mars missions. Space situation awareness and identification of solar system objects would benefit from an ability to precisely track commanded attitude profiles while holding target positions <1 pixel. In this manner, long integration times can be facilitated permitting resolution of extremely dim (small) objects. The system developed here also applications to highly precise position control including formation flight missions and those requiring disturbance free flight. Disturbance reduction has been recently demonstrated in space by Busek's colloid thrusters, larger than those proposed here, on the NASA ST-7/ESA LISA Pathfinder mission.

Potential non-NASA customers include, international partners (such as ESA), the DoD and commercial EO missions. The readily configurable nature of the proposed technology would enable customized applications to simultaneously meet customer needs in precision pointing and disturbance compensation; therefore, maximizing the commercial applicability of the technology. Furthermore, the ability to scale both thrust output and boom moment arm, by virtue of Busek and ROCCOR's respective scalable technologies, enables rapid customization of the system. Commercial EO applications may include optical communication pointing supporting high bandwidth up/downlinks or precision pointing in earth orbit for earth observation organizations. With strong links to the now TRL-7 electrospray system Busek demonstrated on the LISA Pathfinder mission; the time is now right for other organizations to embrace this technology.