Title:
Design to Delivery of Additively Manufactured Propulsion Systems for the SWARM-EX Mission
Design to Delivery of Additively Manufactured Propulsion Systems for the SWARM-EX Mission
Author(s)
Tong, Kevin
Hart, Samuel T.
Glaser, Mackenzie
Wood, Samuel
Hartigan, Mark C.
Lightsey, E. Glenn
Hart, Samuel T.
Glaser, Mackenzie
Wood, Samuel
Hartigan, Mark C.
Lightsey, E. Glenn
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Abstract
Recent progress in miniaturized spacecraft propulsion technology has allowed for the development of complex,
multi-vehicle missions which enable the cost-effective realization of science goals that would previously
have been prohibitively expensive. The upcoming NSF-funded Space Weather Atmospheric Reconfigurable
Multiscale EXperiment (SWARM-EX) mission leverages these swarm techniques to demonstrate novel autonomous
formation flying capabilities while characterizing the spatial and temporal variability of ion-neutral
interactions in the Equatorial Ionization Anomaly and Equatorial Thermospheric Anomaly. SWARM-EX
will fly a trio of 3U CubeSats in a variety of relative orbits with along-track separations ranging from 3 km
to 1300 km.
To achieve the required orbital variability, the mission uses a novel hybrid approach of differential drag
and an onboard cold gas propulsion system. Mission requirements necessitate a propulsion system that
provides each spacecraft with 15 m/s of ΔV and a maximum thrust greater than 5 mN in a volume of
roughly 0.7U (7 cm x 10 cm x 10 cm). Unlike many other CubeSat-scale cold gas propulsion systems which
are used to provide attitude control and perform reaction wheel desaturation burns, the primary objective
of the SWARM-EX propulsion system (SEPS) is to provide ΔV during maneuvers.
The Georgia Institute of Technology Space Systems Design Laboratory (SSDL) is conducting the design,
assembly, and testing of three identical SEPS. By leveraging additive manufacturing technology, the propellant
tanks, nozzle, and tubing are combined into a single structure that efficiently utilizes the allocated
volume. The propulsion system uses two-phase R-236fa refrigerant as a propellant, which allows for the
storage of the majority of propellant mass as a liquid to maximize volumetric efficiency. The final design
allows for 17 m/s of total ΔV per spacecraft and a measured maximum thrust of approximately 35 mN for
short pulse lengths at room temperature. Each individual propulsion system has a volume under 0.5U (489
cm3), making them among the smallest formation-flying CubeSat-scale propulsion systems developed thus
far. Owing to their two-phase propellant storage and single nozzle, the SEPS have a high impulse density
(total impulse provided per unit of system volume) of 176 N-s/L. Additionally, process improvements to
mitigate known failure modes such as propellant leaks and foreign object debris are implemented.
This paper describes the entire design-to-delivery life cycle of the SWARM-EX propulsion units, including
pertinent mission requirements, propulsion system design methodologies, assembly, and testing. Major
lessons learned for future small satellite propulsive endeavors are also detailed.
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Date Issued
2023-08
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