NASA SBIR 2006 Solicitation


PROPOSAL NUMBER: 06-2 S7.01-8584
SUBTOPIC TITLE: Guidance, Navigation and Control Beyond Low Earth Orbit (LEO)
PROPOSAL TITLE: Reaction Wheel Disturbance Model Extraction Software

SMALL BUSINESS CONCERN (Firm Name, Mail Address, City/State/Zip, Phone)
Nightsky Systems, Inc.
3916 Lauriston Road
Raleigh, NC 27616 - 8612
(919) 261-0936

PRINCIPAL INVESTIGATOR/PROJECT MANAGER (Name, E-mail, Mail Address, City/State/Zip, Phone)
Carl Blaurock
3916 Lauriston Rd
Raleigh, NC 27616 - 8612
(919) 261-0936

TECHNICAL ABSTRACT (Limit 2000 characters, approximately 200 words)
Reaction wheel mechanical noise is one of the largest sources of disturbance forcing on space-based observatories. Such noise arises from mass imbalance, bearing imperfections, and other sources. It takes the form of a number of discrete harmonics of the wheel speed, often also with a broadband noise component. Jitter problems can arise when harmonics sweep across observatory modes, and can be exacerbated by gyroscopically coupled spin-rate-dependent wheel structural modes that dynamically amplify the tonal and broadband disturbances. For a well-balanced wheel, higher harmonic forces can be on the same order as the fundamental, therefore when there is a jitter problem it can occur at very low wheel speed. These higher harmonics are generally less well-characterized than the fundamental. The proposed Reaction Wheel Disturbance Model Extraction Software (RWDMES) is a tool for fitting a hybrid physical/empirical model to wheel induced-vibration data. The physical model captures the wheel structure including gyroscopic effects, while the empirical model captures the harmonic forcing and broadband noise. The Phase I effort demonstrated the ability to fit a highly accurate harmonic/broadband/structural model, including 43 harmonics up to 14.63 times the fundamental, to measured wheel disturbance data in a point-and-click environment in about 2 hours. The benefits of the technology include reduced program effort to produce wheel disturbance models, leading to more accurate jitter prediction earlier in a mission. This in turn allows jitter problems to be mitigated at the design stage when changes are relatively inexpensive.

POTENTIAL NASA COMMERCIAL APPLICATIONS (Limit 1500 characters, approximately 150 words)
The Earth observing community would benefit from the RWDMES technology, as would any spacecraft with tight pointing requirements for a three axis stabilized spacecraft. Other applications would include ground-based systems that are sensitive to mechanism induced disturbances, for example large ground based telescopes with rotating mechanisms such as filter wheels. The CELTCO Thirty Meter Telescope (TMT) is one specific example.

POTENTIAL NON-NASA COMMERCIAL APPLICATIONS (Limit 1500 characters, approximately 150 words)
Any three-axis-stabilized pointing instrument would benefit from a reliable reaction wheel disturbance modeling capability. Such a capability would greatly simplify the analysis of pointing performance. A short list includes the James Webb Space Telescope (JWST), Terrestrial Planet Finder Interferometer (TPF-I), Single Aperture Far Infrared Observatory (SAFIR), Vision Mission – Stellar Interferometer (VM-SI), Thirty Meter Space Telescope (TMST), Fourier-Kelvin Stellar Interferometer (FKSI), and the Space Infrared Interferometric Telescope (SPIRIT). All of these missions pose the challenge of a large, lightweight aperture with extremely tight pointing requirements.

NASA's technology taxonomy has been developed by the SBIR-STTR program to disseminate awareness of proposed and awarded R/R&D in the agency. It is a listing of over 100 technologies, sorted into broad categories, of interest to NASA.

Controls-Structures Interaction (CSI)

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