Issue 10 Volume 41 May 16, 2003

20030038806 NASA Langley Research Center, Hampton, VA, USA
Dynamics and Control of Attitude, Power, and Momentum for a Spacecraft Using Flywheels and Control Moment
Gyroscopes
Roithmayr, Carlos M.; Karlgaard, Christopher D.; Kumar, Renjith R.; Seywald, Hans; Bose, David M.; April 2003; 87 pp.;
In English; Original contains black and white illustrations
Contract(s)/Grant(s): RTOP 706-25-02-33
Report No.(s): NASA/TP-2003-212178; NAS 1.60:212178; L-18277; Copyright; Avail: CASI; A05, Hardcopy
Several laws are designed for simultaneous control of the orientation of an Earth-pointing spacecraft, the energy stored
by counter-rotating flywheels, and the angular momentum of the flywheels and control moment gyroscopes used together as
an integrated set of actuators for attitude control. General, nonlinear equations of motion are presented in vector-dyadic form,
and used to obtain approximate expressions which are then linearized in preparation for design of control laws that include
feedback of flywheel kinetic energy error as a means of compensating for damping exerted by rotor bearings. Two flywheel
steering laws are developed such that torque commanded by an attitude control law is achieved while energy is stored or
discharged at the required rate. Using the International Space Station as an example, numerical simulations are performed to
demonstrate control about a torque equilibrium attitude, and illustrate the benefits of kinetic energy error feedback. Control
laws for attitude hold are also developed, and used to show the amount of propellant that can be saved when flywheels assist
the CMGs. Nonlinear control laws for large-angle slew maneuvers perform well, but excessive momentum is required to
reorient a vehicle like the International Space Station.
Author
Spacecraft Control; Attitude Control; Control Moment Gyroscopes; Flywheels; Control Systems Design; Control Simulation;
Control Theory; Equations Of Motion
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GROUND SUPPORT SYSTEMS AND FACILITIES (SPACE)
Includes launch complexes, research and production facilities; ground support equipment, e.g., mobile transporters; and test chambers
and simulators. Also includes extraterrestrial bases and supporting equipment. For related information see also 09 Research and
Support Facilities (Air).
20030032429 NASA Kennedy Space Center, Cocoa Beach, FL, USA
Space Based Communications
Simpson, James; Denson, Erik; Valencia, Lisa; Birr, Richard; [2003]; 9 pp.; In English; Space Congress, 29 Ap. - 1 May 2003,
Cape Canaveral, FL, USA; Original contains black and white illustrations
Report No.(s): KSC-2003-024; No Copyright; Avail: CASI; A02, Hardcopy
Current space lift launches on the Eastern and Western Range require extensive ground-based real-time tracking,
communications and command/control systems. These are expensive to maintain and operate and cover only limited
geographical areas. Future spaceports will require new technologies to provide greater launch and landing opportunities,
support simultaneous missions, and offer enhanced decision support models and simulation capabilities. These ranges must
also have lower costs and reduced complexity while continuing to provide unsurpassed safety to the public, flight crew,
personnel, vehicles and facilities. Commercial and government space-based assets for tracking and communications offer
many attractive possibilities to help achieve these goals. This paper describes two NASA proof-of-concept projects that seek-to
exploit the advantages of a space-based range: Iridium Flight Modem and Space-Based Telemetry and Range Safety (STARS).
Iridium Flight Modem uses the commercial satellite system Iridium for extremely low cost, low rate two-way communications
and has been successfully tested on four aircraft flights. A sister project at Goddard Space Flight Center’s (GSFC) Wallops
Flight Facility (WFF) using the Globalstar system has been tested on one rocket. The basic Iridium Flight Modem system
consists of a L1 carrier Coarse/Acquisition (C/A)-Code Global Positioning System (GPS) receiver, an on-board computer, and
a standard commercial satellite modem and antennas. STARS uses the much higher data rate NASA owned Tracking and Data
Relay Satellite System (TDRSS), a C/A-Code GPS receiver, an experimental low-power transceiver, custom built command
and data handler processor, and digitized flight termination system (FTS) commands. STARS is scheduled to fly on an F-15
at Dryden Flight Research Center in the spring of 2003, with follow-on tests over the next several years.
Author
Spacecraft Launching; Satellite Communication; Flight Tests; Command And Control; Ground Support Systems; Spacecraft
Tracking; Space Surveillance (Spaceborne); Spacecraft Landing
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