Milliarcsecond Small Spacecraft Attitude Control System

Busek proposes to develop a highly modular attitude control system (ACS) which will provide orders of magnitude improvements over state-of-the-art alternative ACS for CubeSats. The low inertia of CubeSats combined with vibrational disturbances and resolution limitations of state-of-the-art ACS presently limit body-pointing and position control accuracy. Busek’s electrospray thrusters aboard the ESA LISA Pathfinder spacecraft recently demonstrated precision control at nm scales; this work extends that success to CubeSat platforms. Passively fed electrospray thrusters are highly compact, including fully integrated propellant supplies, and are capable of ~100nN thrust control at 10’s of nN noise. Thrust can be throttled over >30x, to a scalable maximum of 10’s of uN. These traits, combined with >900s Isp enable these systems to replace traditional reaction wheel ACS; improving pointing error from arcsecs to 10’s of milliarcsec. This work addresses critical development gaps, in both thruster-heads and a multi-axis power processing unit, presently gating the technology. Phase I established a thorough baseline dataset, which confirmed critical performance metrics, and established development gaps. Phase II will emphasize total impulse goals and thruster system maturation. Task 1 will execute design modifications developed in Phase I and augment existing test capabilities. Task 2 will identify and address impulse limiting mechanisms. Task 3 will develop and validate solutions to known mechanical risks and incorporate evolved requirements into a low-mass engineering-model thruster module. Task 4 will focus on power processing development, targeting a control architecture which maximizes the precision control capabilities of the technology and serves multiple thruster heads. These efforts will converge in Task 5 where engineering model thruster performance will be rigorously evaluated over a complete life demonstration.