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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1968

Orbiting Geophysical Observatory Attitude Control Subsystem Design Survey. NASA/ERC Design Criteria Program, Guidance and Control

This design survey summarizes the history of the Orbiting Geophysical Observatories' (OGO) Attitude Control Subsystem (ACS) from the proposal phase through current flight experience. Problems encountered in design, fabrication, test, and on orbit are discussed. It is hoped that the experiences of the OGO program related here will aid future designers.

Mc Kenna, K. J.↗
NASA NTRS1972

Absolute stability analysis of attitude control systems for large boosters.

A method for performing absolute stability analyses of attitude control systems for large launch vehicles is presented. Absolute stability of these systems is shown in a finite region of the state space. The regions are computed by using the Lur'e-Postnikov Liapunov function. This function is chosen to provide additional information about the exponential property of absolute stability. Significant advantages of the method proposed in this paper are: it is independent of the order of the system; algebraic operations involved in the computations are relatively simple and convenient for machine implementation; and the obtained results are valid not only for a particular nonlinearity but also for an entire class of nonlinear characteristics that satisfy certain general conditions. A system model representing the Saturn V launch vehicle is used to illustrate the method.

Seltzer, S. M.↗
NASA NTRS1973

Attitude control of a large flexible spacecraft using three-axis mass expulsion control.

A study of the elastic effects of large area solar arrays on attitude control of a spacecraft was conducted. It is demonstrated for sufficiently low structural frequencies that excitation of certain modes can induce instability in the pitch axis. Stiffening the arrays can eliminate the instability. However, a severe weight penalty is associated with such modification. A more efficient means of minimizing the structural interaction effects is to change the shape of the array. For stable configurations, another problem may be encountered. This is the imposition of high rates on the spacecraft bus by oscillation of the solar arrays. Since low rates are required to obtain accurate science experiment results, it is imperative that the high rate problem be resolved. This also is possible by changing the solar array configuration.

Marsh, E. L.↗
NASA NTRS1974

Skylab thruster attitude control system

Preflight activities and the Skylab mission support effort for the thruster attitude control system (TACS) are documented. The preflight activities include a description of problems and their solutions encountered in the development, qualification, and flight checkout test programs. Mission support effort is presented as it relates to system performance assessment, real-time problem solving, flight anomalies, and the daily system evaluation. Finally, the detailed flight evaluation is presented for each phase of the mission using system telemetry data. Data assert that the TACS met or exceeded design requirements and fulfilled its assigned mission objectives.

Wilmer, G. E., Jr.↗
NASA NTRS1976

Design study for LANDSAT D attitude control system

A design and performance evaluation is presented for the LANDSAT D attitude control system (ACS). Control and configuration of the gimballed Ku-band antenna system for communication with the tracking and data relay satellite (TDRS). Control of the solar array drive considered part of the ACS is also addressed.

Iwens, R. P.↗
NASA NTRS1990

Attitude control requirements for various solar sail missions

The differences are summarized between the attitude control requirements for various types of proposed solar sail missions (Earth orbiting; heliocentric; asteroid rendezvous). In particular, it is pointed out that the most demanding type of mission is the Earth orbiting one, with the solar orbit case quite benign and asteroid station keeping only slightly more difficult. It is then shown, using numerical results derived for the British Solar Sail Group Earth orbiting design, that the disturbance torques acting on a realistic sail can completely dominate the torques required for nominal maneuvering of an 'ideal' sail. This is obviously an important consideration when sizing control actuators; not so obvious is the fact that it makes the standard rotating vane actuator unsatisfactory in practice. The reason for this is given, and a set of new actuators described which avoids the difficulty.

Williams, Trevor↗
NASA NTRS1993

Robust attitude control for Cassini spacecraft flying by Titan

This paper summarizes a few years attitude control design work on Cassini spacecraft with emphasis on the mission of Titan flyby. The study consists of modeling of the spacecraft dynamics, fuel sloshing, aerodynamic disturbance, controller design, nonlinear simulation, and establishing geometric command profiles. Both classical bang-bang control and modern robust H-infinity control have been designed and evaluated in nonlinear simulation to access the system tracking performance. Design procedures as well as their critical design issues are discussed in detail. Full model nonlinear simulations indicate that a simple 12-state H-infinity controller achieves better radar tracking performance than the classical bang-bang controller with less fuel throughout the flyby mission. Detailed robustness analysis of both designs will be published elsewhere.

Chiang, R.↗
NASA NTRS1976

Attitude control of Mariner Jupiter-Saturn spacecraft

A major challenge of the Mariner Jupiter-Saturn '77 spacecraft was devising a suboptimal attitude controller that could meet the demanding mission requirements. The challenge was met by implementing a discrete stochastic controller for a specially designed onboard computer. The paper describes the design and operation of the controller, based on a simple model of spacecraft dynamics. Two types of cruising modes are considered: inertial cruise, where spacecraft attitude is determined from gyro position outputs, and celestial cruise, where position information is obtained from sun sensors and a star tracker. These two cruise modes under conditions of disturbances were simulated on computer, and the results showed that the controller maintained the spacecraft attitude with low rates. An appendix gives details on the single-step predictor.

Bahrami, K. A.↗
NASA NTRS1994

Venusian atmospheric and Magellan properties from attitude control data

Results are presented of the study of the Venusian atmosphere, Magellan aerodynamic moment coefficients, moments of inertia, and solar moment coefficients. This investigation is based upon the use of attitude control data in the form of reaction wheel speeds from the Magellan spacecraft. As the spacecraft enters the upper atmosphere of Venus, measurable torques are experienced due to aerodynamic effects. Solar and gravity gradient effects also cause additional torques throughout the orbit. In order to maintain an inertially fixed attitude, the control system counteracts these torques by changing the angular rates of three reaction wheels. Model reaction wheel speeds are compared to observed Magellan reaction wheel speeds through a differential correction procedure. This method determines aerodynamic, atmospheric, solar pressure, and mass moment of inertia parameters. Atmospheric measurements include both base densities and scale heights. Atmospheric base density results confirm natural variability as measured by the standard orbital decay method. Potential inconsistencies in free molecular aerodynamic moment coefficients are identified. Moments of inertia are determined with a precision better than 1 percent of the largest principal moment of inertia.

Croom, Christopher A.↗
NASA NTRS1962

Measured Steady-State Performance of Water Vapor Jets for Use in Space Vehicle Attitude Control Systems

Measurements have been made in a vacuum environment to determine the steady-state performance of several nozzles having thrusts up to 1000 dynes for use in space vehicle attitude control systems. Water vapor was used as a propellant. The results indicate that the trend of the variation of specific impulse and thrust coefficient with expansion ratio is predicted by calculations based on one-dimensional isentropic flow. The level of these quantities, however, is dependent upon the nozzle diameter. The specific impulse, for example, varies from about 30 percent to 80 percent of the theoretical value as the nozzle thrust is increased from about 10 to 1000 dynes.

JET↗