Engineering Papers⌕ Search

Engineering topics

Medved, D. B.

Publications and source records attributed to Medved, D. B..

9 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Experiment S026: Ion wake measurement

Measurements of the ion-wake and electron-wake structure and other perturbations of the ambient medium produced by the Gemini spacecraft in orbit are reported. Thruster firings in the TDA-south configuration produced a decrease in the observed ion flux to the outboard ion sensor, an apparent increase in the ion flux to the inboard ion sensor, and an enhanced electron concentration to the outboard electron sensor. Visual inspection of strip-chart data was indicative that definitive wake-cone angles could be determined. It also was apparent for many cases that the electron distribution followed the ion depletion effects; this was indicative that the wake was a plasma, not an ion wake. Analysis of the data from the GATV orbits was indicative that electron and ion temperatures were higher than was estimated. The high electron temperature accounted for the sensor saturation observed during the mission. This temperature measurement was 0.3 electron volt at a 200-n. mi. altitude during daytime conditions. Spacecraft wake structure has been observed as far as 100 feet from the vehicle.

Medved, D. B.↗
NASA NTRS1971

Gemini experiment S026

The results of the reduction and analysis of data obtained from the S026 experiment from Gemini 10 and 11 flights are presented. The electron and ion sensors were continuously operative throughout both missions from shroud removal (about 6 minutes after Agena liftoff to power-down conditions one week later). Data on ion and electron currents, electron temperature, and vehicle potential were obtained at a sample rate of 32 times per second on positive ions for each of two ion sensors and once every 1.067 seconds for the electron sensor. Only the data reduction of the Gemini plasma wake measurements comprising roughly twenty minutes of data for six maneuvers programed for wake measurements are considered. The intermediate depletion zone, between 1 and 10 vehicle radii downstream from the object, is emphasized. The smallest characteristic radius of interest is 1.34 feet and the largest is 5 feet. This implies a separation span extending from approximately 1.5 feet at the closest approach to at least 50 feet into the far field.

Medved, D. B.↗
NASA NTRS1969

Concept for improved vacuum pressure measuring device

To measure vacuum pressures in the range of 5 times 10 to the minus 7 to 5 times 10 to the minus 16, a semiconductor resistor composed of sintered zinc oxide is used. Through the effect of surface absorbed gases on the resistance of the semiconductor material, very low pressures are measured.

Medved, D. B.↗