Computer Science
Scientific paper
Jan 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002iaf..confe.815k&link_type=abstract
IAF abstracts, 34th COSPAR Scientific Assembly, The Second World Space Congress, held 10-19 October, 2002 in Houston, TX, USA.,
Computer Science
Scientific paper
The authors have previously shown that a micro-scale solar thermal engine, using storable monopropellants (e.g., water, ammonia, or hydrazine) and simplified subsystems, augments microsatellite capabilities by permitting velocity changes on the order of 1,500-3,000 m/s. Small satellites have long been seen as "confined" to limited roles in Low Earth Orbit (LEO). Adding significant propulsive capability opens up new roles and missions--among these, communications in geosynchronous earth orbit (GEO), as well as lunar orbit insertion and near-earth asteroid flybys. Transfer times range from as little as 30-40 days (for Geosynchronous Transfer Orbit to GEO) to 275 days for selected near-earth object encounters. This is accomplished by performing moderate thrust (~5 N) firings of the solar thermal engine at perigee and/or apogee. This paper will briefly review benchmark missions and preliminary design choices, concentrating on the selected detailed design and its ramifications for testing and spacecraft operational use. The solar thermal propulsion system is to be built as a proto-qualification/proto-flight unit (i.e., tested to qualification levels and subsequently used in on-orbit operations). This will minimize the number of experimental iterations prior to flight and reduce overall development cost. The testing program will include acoustic, sinusoidal, and random vibration tests, in line with Ariane 5's Ariane Structure for Auxiliary Payloads (ASAP) requirements. As several SSTL enhanced microsatellites have flown aboard Ariane, these figures represent excellent baseline values for the test campaign. Additionally, the solar thermal engine will be constructed so as to ensure compatibility with existing host spacecraft operational protocols. SSTL ground operations are "autonomous and self-checking," requiring the equivalent of only several operators per day to manage numerous small satellite passes. It is important that an advanced propulsion system not compromise the existing operational paradigm by requiring significantly increased oversight at the satellite ground station. Imposing significant requirements on the host satellite--stringent pointing, an added command and telemetry burden, substantial power augmentation, or severe structural modifications--could make a prima facie "useful" system worthless to the owner and/or operator. The authors will describe some of the creative solutions used to minimize these imposed requirements, simplifying the satellite designer's task. The result of this activity is a low-cost, two-year test program that is intended to result in a fully qualified flight-ready solar thermal engine, prepared for integration and launch no later than 2005. The views expressed in this article are those of the authors and do not reflect the official policy or position of the United States Air Force, Department of Defense, or the U.S. Government.
Gibbon Dave
Kennedy Gareth F.
Palmer Patrick
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