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Lightsey,
E. Glenn
Lightsey,
E. Glenn
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ItemDevelopment and Testing of a 3-D-Printed Cold Gas Thruster for an Interplanetary CubeSat(Georgia Institute of Technology, 2018-03) Lightsey, E. Glenn ; Stevenson, Terry ; Sorgenfrei, MatthewThis paper describes the development and testing of a cold gas attitude control thruster produced for the BioSentinel spacecraft, a CubeSat that will operate beyond Earth orbit. The thruster will reduce the spacecraft rotational velocity after deployment, and for the remainder of the mission it will periodically unload momentum from the reaction wheels. The majority of the thruster is a single piece of 3-D-printed additive material which incorporates the propellant tanks, feed pipes, and nozzles. Combining these elements allows for more efficient use of the available volume and reduces the potential for leaks. The system uses a high-density commercial refrigerant as the propellant, due to its high volumetric impulse efficiency, as well as low toxicity and low storage pressure. Two engineering development units and one flight unit have been produced for the BioSentinel mission. The design, development, and test campaign for the thruster system is presented.
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ItemCupid's Arrow: A Small Satellite Concept to Measure Noble Gases in Venus' Atmosphere(Georgia Institute of Technology, 2018-03) Sotin, Christophe ; Avice, Guillaume ; Baker, John ; Freeman, Anthony ; Madzunkov, Stojan ; Stevenson, Terry ; Arora, Nitin ; Darrach, M. R. ; Lightsey, E. Glenn ; Marty, B.Getting reliable measurements of noble gases in Venus’ atmosphere with a CubeSat-derived mission concept is very challenging. But if feasible it could change how we make this fundamental geochemical measurement in planetary atmospheres and other gaseous environments (e.g., plumes emanating from icy moons or dwarf planets) across the solar system. Venus poses the most urgent and nearby target for such measurements, to fill in a key piece of the puzzle of Venus’ origin, evolution, and divergence from Earth’s geophysical history. Understanding Venus’ geophysical evolution is also key to interpreting observations of “Earth-like” exoplanets in order to assess whether they are Earth-like or Venus-like, which has obvious implications for their habitability potential. Noble gases are tracers of the evolution of planets. They trace processes such as the original supply of volatiles from the solar nebula, delivery of volatiles by asteroids and comets, escape rate of planetary atmospheres, degassing of the interior, and its timing in the planet’s history. However, a major observational missing link in our understanding of Venus’ evolution is the elementary and isotopic pattern of noble gases and stable isotopes in its atmosphere, which remain poorly known [1]. The concentrations of heavy noble gases (Kr, Xe) and their isotopes are mostly unknown, and our knowledge of light noble gases (He, Ne, Ar) is incomplete and imprecise. The Cupid’s Arrow mission concept would measure those quantities below the homopause where gas compounds are well mixed.
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ItemDesign and Operation of a Thrust Test Stand for University Small Satellite Thrusters(Georgia Institute of Technology, 2018-01) Stevenson, Terry ; Lightsey, E. GlennA small, low cost thrust test stand was developed at the Georgia Institute of Technology to support ongoing small spacecraft propulsion research. The test stand is a torsional pendulum with a low natural frequency, designed to respond to thruster pulses in the range of milliseconds to hundreds of milliseconds as if they were instantaneous impulses. The stand displacement is measured by an LVDT, and the magnitude of the oscillation resulting from the thrust is used to determine the impulse delivered. The stand is not actively damped, and is operated with less time between impulses than the oscillations take to decay. A postprocessing method was developed to separate the oscillation caused by an impulse from the previous oscillations, by fitting a damped oscillator equation before and after the impulse, and determining the instantaneous angular velocity change across the impulse. The stand was used to test a thruster developed at Georgia Tech for the NASA BioSentinel mission.
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ItemPerformance Characterization of a Cold Gas Propulsion System for a Deep Space Cubesat(Georgia Institute of Technology, 2017-02) Sorgenfrei, Matt ; Stevenson, Terry ; Lightsey, E. GlennOne challenge facing the developers of CubeSats that operate in deep space is that magnetic torque rods cannot be used for unloading the momentum stored in reaction wheels. Rather, this task is performed by a system of thrusters. While a wide variety of attitude control thrusters have been deployed on larger spacecraft, there remain very few examples of such systems being used on CubeSats. The upcoming BioSentinel mission, under development at NASA Ames Research Center, is an example of a CubeSat-class spacecraft that requires thrusters for momentum management. A new 3D-printed cold gas thruster was developed for this application. This paper will describe the test campaign that was completed for the engineering development unit (EDU), and will present a variety of preliminary results describing the performance characteristics of the thruster. The test campaign for the propulsion system EDU was carried out in partnership with members of the In-Space Propulsion Branch at Glenn Research Center in Cleveland, OH.
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ItemDesign and Characterization of a 3D-Printed Attitude Control Thruster for an Interplanetary 6U CubeSat(Georgia Institute of Technology, 2016-08) Stevenson, Terry ; Lightsey, E. GlennThis paper describes the design and testing of a miniature, 3D-printed cold gas attitude control thruster for the NASA Ames Research Center BioSentinel mission, an interplanetary small spacecraft that will be launched on the Em-1 flight of SLS. Earth-orbiting small satellites typically use magnetic torque rods for momentum unloading, but these cannot be employed in interplanetary space due to the lack of a strong external magnetic field. ACS thrusters can be used to unload reaction wheels or used directly for attitude control, regardless of the external environment. By 3D printing the propellant tanks, pipes, and nozzles into a single component, the complexity and cost of the thruster are reduced. The use of 3D printing also allows the thruster to better utilize its allocated volume to store more propellant. This is especially important for strictly volume-constrained spacecraft, such as CubeSats. The thruster has seven nozzles that are printed directly into the surface of the structure. The BioSentinel thruster has been tested at the Georgia Institute of Technology by the Space Systems Design Lab. The thrust of each nozzle has been measured to be approximately 50 milliNewtons, with a specific impulse of approximately 31 seconds.
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ItemConsiderations for Operation of a Deep Space Nanosatellite Propulsion System(Georgia Institute of Technology, 2016-02) Sorgenfrei, Matt ; Stevenson, Terry ; Lightsey, E. GlennA distinguishing feature of deep space CubeSats is that they require some form of propulsion system, either for orbital maneuvering operations, spacecraft momentum management, or both. However, the comparatively short lifecycle for these missions, combined with the mass and volume restrictions that are attendant with the CubeSat form factor, make the integration of propulsion systems one of the highest-risk aspects of the entire mission. There are a limited number of facilities around the country that can support accurate testing of thruster systems that generate milli-Newtons of thrust, and the cost associated with handling and transportation of traditional propellants can be prohibitive for many CubeSat mission budgets. As a result, many deep space CubeSats are considering propulsion systems that are either at a fairly low technology readiness level or which will be integrated after a truncated test campaign. This paper will describe the propulsion system architecture selected for the BioSentinel mission, a six-unit CubeSat under development at NASA Ames Research Center. Bio-Sentinel requires a propulsion system to support detumble and momentum management operations, and this paper will discuss the integration of a third-party propulsion system with an Ames-built CubeSat, as well as the test campaign that is underway for both quality control and requirements verification purposes.