Engineering topics

Flatley, T. W.

Publications and source records attributed to Flatley, T. W..

16 records

NASA NTRS1985

Tetrahedron array of reaction wheels for attitude control and energy storage

A spacecraft subsystem, working in conjunction with a solar array, which provides 3-axis attitude control as well as some power system functions is described. Four flywheels, driven by variable-field d.c. motors and arranged in a tetrahedron configuration, are employed. In sunlight, the system provides voltage regulation while the wheels are accelerated to some maximum speed. In the dark, the motors become flywheel-driven generators which provide regulated power to other spacecraft electrical loads. A microprocessor is used to compute field current levels for each of the 4 motor/generators, based on measurements of the system voltage level, the flywheel speeds, and the attitude control torques desired.

Flatley, T. W.↗

NASA NTRS1981

SMM attitude control recovery

A description is given of the way in which the Modular Attitude Control System (MACS) onboard computer of the NASA Solar Maximum Mission (SMM) laboratory was reprogrammed, to restore attitude control for the SMM, after fuse failures permanently disabled all three of the MACS primary reaction wheels. Algorithms were developed which provided both a thermal- and power-safe, spin-stabilized mode and three-axis sun pointing, using the damaged primary wheels' backup skew wheel in a momentum-bias control scheme. Magnetic torquing was used in these algorithms for angular momentum vector magnitude and directional control.

Hoffman, H. C.↗

NASA NTRS1977

An active nutation damper for spacecraft

An active nutation damping device, consisting of an angular accelerometer, a dc motor driven flywheel, and associated electronics, was developed for spacecraft use. This damping system was used on the Lageos spacecraft, launched 4 May 1976, to control nutation buildup during the long coast period after the third stage separation. Of many electrical and mechanical design choices, an angular rather than linear accelerometer offered some advantages but problems developed in adapting the angular accelerometer to spacecraft use. The damper package was evaluated and proven on a three axis gas-bearing simulator that duplicated the Lageos spacecraft critical flight dynamics. A failure analysis of the damper assembly was performed. Performance of the damper during the Lageos flight has confirmed the preflight evaluation and analysis.

Abercrombie, R. A.↗

NASA NTRS1977

An active nutation damper for spacecraft

An active nutation damping device, consisting of an angular accelerometer, a dc-motor-driven flywheel, and associated electronics, was developed for spacecraft use. This damping system was used on the LAGEOS spacecraft, launched May 4, 1976, to control nutation buildup during the long coast period (approximately 75 minutes) after the third stage separation. Of the many electrical and mechanical design choices involved, the use of an angular rather than linear accelerometer offers some advantages. There are some problems of adapting the angular accelerometer to spacecraft use. The damper package was evaluated and proven on a three-axis gas-bearing simulator that duplicated the LAGEOS spacecraft critical flight dynamics. A failure analysis of the damper assembly was performed.

Abercrombie, R. A.↗

NASA NTRS1977

An active nutation damper for spacecraft

An active nutation damping device, consisting of an angular accelerometer, a dc-motor-driven flywheel, and associated electronics, developed for spacecraft use is described. This damping system was used on the LAGEOS spacecraft to control nutation buildup during the long coast period (approximately 75 minutes) after the third stage separation. The damper package was evaluated and proven on a three-axis gas-bearing simulator that duplicated the LAGEOS spacecraft critical flight dynamics. In addition, a failure analysis of the damper assembly was performed. Performance of the damper during the LAGEOS flight has confirmed the preflight evaluation and analysis.

Abercrombie, R. A.↗

NASA NTRS1971