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Proceedings Paper

Orbital Express fluid transfer demonstration system
Author(s): Scott Rotenberger; David SooHoo; Gabriel Abraham
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Paper Abstract

Propellant resupply of orbiting spacecraft is no longer in the realm of high risk development. The recently concluded Orbital Express (OE) mission included a fluid transfer demonstration that operated the hardware and control logic in space, bringing the Technology Readiness Level to a solid TRL 7 (demonstration of a system prototype in an operational environment). Orbital Express (funded by the Defense Advanced Research Projects Agency, DARPA) was launched aboard an Atlas-V rocket on March 9th, 2007. The mission had the objective of demonstrating technologies needed for routine servicing of spacecraft, namely autonomous rendezvous and docking, propellant resupply, and orbital replacement unit transfer. The demonstration system used two spacecraft. A servicing vehicle (ASTRO) performed multiple dockings with the client (NextSat) spacecraft, and performed a variety of propellant transfers in addition to exchanges of a battery and computer. The fluid transfer and propulsion system onboard ASTRO, in addition to providing the six degree-of-freedom (6 DOF) thruster system for rendezvous and docking, demonstrated autonomous transfer of monopropellant hydrazine to or from the NextSat spacecraft 15 times while on orbit. The fluid transfer system aboard the NextSat vehicle was designed to simulate a variety of client systems, including both blowdown pressurization and pressure regulated propulsion systems. The fluid transfer demonstrations started with a low level of autonomy, where ground controllers were allowed to review the status of the demonstration at numerous points before authorizing the next steps to be performed. The final transfers were performed at a full autonomy level where the ground authorized the start of a transfer sequence and then monitored data as the transfer proceeded. The major steps of a fluid transfer included the following: mate of the coupling, leak check of the coupling, venting of the coupling, priming of the coupling, fluid transfer, gauging of receiving tank, purging of coupling and de-mate of the coupling.

Paper Details

Date Published: 15 April 2008
PDF: 9 pages
Proc. SPIE 6958, Sensors and Systems for Space Applications II, 695808 (15 April 2008); doi: 10.1117/12.783948
Show Author Affiliations
Scott Rotenberger, Northrop Grumman Corp. (United States)
David SooHoo, Northrop Grumman Corp. (United States)
Gabriel Abraham, Northrop Grumman Corp. (United States)


Published in SPIE Proceedings Vol. 6958:
Sensors and Systems for Space Applications II
Richard T. Howard; Pejmun Motaghedi, Editor(s)

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