Search NASA⌕ Search

Engineering topics

Evans, H. E.

Publications and source records attributed to Evans, H. E..

16 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Magnetically suspended flywheel system study

A program to study the application of a graphite/epoxy, magnetically suspended, pierced disk flywheel for the combined function of spacecraft attitude control and energy storage (ACES) is described. Past achievements of the program include design and analysis computer codes for the flywheel rotor, a magnetically suspended flywheel model, and graphite/epoxy rotor rings that were successfully prestressed via interference assembly. All hardware successfully demonstrated operation of the necessary subsystems which form a complete ACES design. Areas of future work include additional rotor design research, system definition and control strategies, prototype development, and design/construction of a UM/GSFC spin test facility. The results of applying design and analysis computer codes to a magnetically suspended interference assembled rotor show specific energy densities of 42 Wh/lb (92.4 Wh/kg) are obtained for a 1.6 kWh system.

Kirk, J. A.↗
NASA NTRS1981

In-space inertial energy storage design

Flywheel energy storage is a means of significantly improving the performance of space power systems. Two study contracts have been completed to investigate the merits of a magnetically suspended, ironless armature, ring rotor 'Mechanical Capacitor' design. The design of a suitable energy storage system is evaluated, taking into account baseline requirements, the motor generator, details regarding the suspension design, power conditioning, the rotor, and an example design. It appears on the basis of this evaluation that the inertial (flywheel) energy storage design is feasible.

Studer, P. A.↗
NASA NTRS1978

Energy storage apparatus

A high efficiency, flywheel type energy storage device which comprises an electronically commutated d.c. motor/generator unit having a massive flywheel rotor magnetically suspended around a ring shaped stator is presented. During periods of low energy demand, the storage devices were operated as a motor, and the flywheel motor was brought up to operating speed. Energy was drawn from the device functioning as a generator as the flywheel rotor rotated during high energy demand periods.

Studer, P. A.↗
NASA NTRS1977

Low-loss energy storage flywheel

Magnetically-levitated, ironless-armature spokeless rotor is used. Ironless armature construction eliminates core losses due to hysteresis and eddy currents. Device combines features of homopolar salient poles and stationary ironless electronically commutated armature.

Evans, H. E.↗
NASA NTRS1976

Mechanical capacitor

A new energy storage system (the mechanical capacitor), using a spokeless magnetically levitated composite ring rotor, is described and design formulas for sizing the components are presented. This new system is configured around a permanent magnet (flux biased) suspension which has active servo control in the radial direction and passive control in the axial direction. The storage ring is used as a moving rotor and electronic commutation of the stationary armature coils is proposed. There is no mechanical contact with the rotating spokeless ring; therefore, long life and near zero rundown losses are projected. A 7-kW h system is sized to demonstrate feasibility. A literature review of flywheel energy storage systems is also presented and general formulas are developed for comparing rotor geometries.

Kirk, J. A.↗
NASA NTRS1975

In-flight friction and wear mechanism

A unique mechanism developed for conducting friction and wear experiments in orbit is described. The device is capable of testing twelve material samples simultaneously. Parameters considered critical include: power, weight, volume, mounting, cleanliness, and thermal designs. The device performed flawlessly in orbit over an eighteen month period and demonstrated the usefulness of this design for future unmanned spacecraft or shuttle applications.

Devine, E. J.↗
NASA NTRS1973

In-flight and laboratory vacuum-friction test results

Coefficient of friction measurements were made for six unlubricated metal couples exposed to the space environment aboard the OV-1-13 spacecraft and exposed to laboratory vacuum. Materials studied included mutually soluble, partially soluble, and insoluble metal combinations. Two samples of each material couple were tested in space and in the laboratory using the disk and rider technique. Linear velocity was 0.10 cm/s (2.5 in/min) and rider normal load was 4.45 N (1 lb) for the gold versus silver couples and 8.90 N (2lb) for the other combinations. Results showed that friction data obtained in a clean ion-pumped laboratory vacuum of 10 to the minus 10 power materials with low mutual solubility can be correlated to operation in the vicinity of a typical scientific spacecraft that is exposed to an ambient pressure as low as 10 to the minus 12 power torr. The expected increase in coefficient of friction with solubility was shown. Material couples with high mutual solubility present the hazard of unpredictable drastic friction increase in orbit which may not be evident in laboratory testing at levels down to 10 to the minus 10 power torr. It was also shown that gross cold welding of unlubricated metals exposed to a satellite environment does not occur.

Devine, E. J.↗