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 at 10's of nN noise. Thrust can be throttled over >25x, to a scalable maximum of 10's of uN. These traits, combined with >1200s 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 with integrated firmware, presently gating the technology. Phase I will focus on establishing a baseline set of data and methodologies permitting detailed verification of the technology and definition of development gaps. The output of existing designs will be scaled to target ACS applicable performance in Task 1, culminating in assembly of two thrusters. A precisely measured performance map including thrust range, resolution and noise will be measured in Task 2 from both thruster heads. Those data will permit PPU system requirements to be defined and will feed development of control laws to be evaluated, in Task 3, using a hardware-in-the-loop precision pointing test apparatus. Electronics requirements will be assessed against existing single-axis architectures and new HV converter measurements in Task 4, along with identification of thruster head development needs; establishing a path towards a full system development in Phase II.

NASA's 2015 technology roadmap recognizes the importance of electrospray propulsion to attitude control, formation flight and positioning of small spacecraft. Specific applications benefiting from precision pointing include astronomical missions, planetary (including earth) observations, laser communications and space situational awareness. The greatly improved body pointing afforded by the proposed technology would present designers with previously unobtainable levels of stability and resolution; permitting both lower cost/complexity realization of existing needs and enabling new objectives in these fields. Applications benefiting from highly precise position control include formation flights and missions requiring disturbance free flight. This include drag-compensation enabling enhanced mission durations at low orbit altitudes below 350km. The proposed work would allow small spacecraft, CubeSats and larger, to benefit from precision control in a manner akin to the NASA Disturbance Reduction System (DRS), featuring Busek thrusters, aboard the LISA Pathfinder mission. Developing a highly featured PPU and controller would also enable other DRS sub-components, such as GSFC contributed control algorithms, to be applied over a wider NASA mission portfolio. Moreover, through obviating the need for reaction wheels and their de-saturation RCS, the proposed work would decrease the size/complexity and therefore cost of missions.

Compact propulsion systems that are scalable in both thrust and deltaV without loss of performance are an enabling technology for CubeSat missions and therefore have numerous commercial applications. Potential non-NASA customers include, international partners (such as ESA), the DoD and commercial EO missions. The modular nature of the proposed technology would enable customized applications that simultaneously meet customer needs in precision pointing and disturbance compensation; therefore, maximizing the commercial applicability of the technology. The virtual elimination of vibrational jitter while superseding reaction wheel precision presents a clear competitive advantage. The proposed system would be applicable to a myriad of CubeSat sizes from ~3U to >25kg; the market size is therefore large and includes rapidly growing platforms. Commercial applications may include optical communication alignment for high bandwidth up/downlinks or precision pointing during EO missions in low orbits. De-orbiting applications are particularly relevant to new LEO EO and telecommunication initiatives. International consensus is forming around the need for orbital debris management, which poses risks to functioning space assets. The proposed system could enable precision attitude control and a de-orbit means from a single integrated system; thus reducing the burden of integrating a de-orbit system.

This is early/mid-stage (TRL 4) — the most realistic path in is NASA SBIR/STTR, which funds small businesses and research institutions to develop technology aligned with NASA's needs (equity-free, phased funding). Check whether a current SBIR/STTR solicitation topic overlaps with this project's technology area, or contact the project directly (above) to ask.

None of these are guaranteed paths for this specific project — TechPort itself doesn't have an "apply" button. Reaching out to the contact(s) above with a specific question is usually the fastest way to find out what's actually open.