Engineering topics

Williams, Donald E.

Publications and source records attributed to Williams, Donald E..

3 records

NASA NTRS1990

Earth observations during Space Shuttle mission STS-34 - 18-23 October 1989

An overview is presented of the 31st Space Shuttle mission, whose major objective was to deploy the Galileo spacecraft. Color images are presented of photos taken by the four videocameras in the payload bay, one 16-mm Arriflex in the cabin, a videocamcorder, three 35 mm cameras, two 70 mm cameras, and an IMAX camera. In addition, descriptions of visual observations by the mission astronauts are given. The most significant STS-34 earth photography for the major geographical regions is discussed. Individual highlights of this mission include observation of the apparent recovery of the water level of Lake Nasser to conditions similar to those during the second Space Shuttle mission of 1981; the documentation of the impact of the Yucatan forest blowdown and fires after the passage of Hurricane Gilbert; and the confirmation of the high value of space photography under low and very low sun angle conditions for geomorphological and geological analyses.

Helfert, Michael R.↗

NASA NTRS1988

Solar ultraviolet irradiances on December 7, 1983, and December 10, 1984

The full-disk absolute solar irradiance was measured on Dec. 7, 1983, and Dec. 10, 1984. The first flight obtained data over the wavelength interval 150-260 nm, while the second obtained data from 150 to 340 nm. Absolute accuracy of the measurements varied from + or - 3 to + or - 9 percent, depending on the flight and the particular wavelength. Between 200 and 240 nm the results reported here are higher than previously reported irradiances, but there is good agreement over the other wavelength intervals. Near 150 nm the change in the solar flux between these two flights did not exceed 7 percent. Aove 200 nm the change in the solar irradiance was not larger than the error bars of the measurement.

Mentall, James E.↗

NASA NTRS1976

Dual mode solid state power switch

A solid state amplifier has an output transistor stage and an input transistor stage interconnected as a Darlington circuit. An interstage transistor interconnecting the collectors of the two stages of the Darlington circuit is connected with the first stage transistor in a compound configuration. When the load current furnished by the amplifier is less than a predetermined value, the output stage operates as a simple saturated switch with its base drive current flowing through the emitter-base junction of the first stage which produces no collector current because the base-emitter junction of the interstage transistor is reverse-biased. When the load current exceeds said predetermined value, the interstage transistor begins to conduct allowing the input and output stages to operate as a Darlington amplifier and diverting a significant portion of the base drive current of the output transistor back into the load.

Maus, Louis C.↗