Engineering topics

Oyama, K. I.

Publications and source records attributed to Oyama, K. I..

5 records

NASA NTRS1987

Results from a series of tethered rocket experiments

This paper reports the results of three tethered rocket experiments conducted as part of a U.S.-Japan joint program under way since 1980. The major purpose of the experiments is to obtain technical and scientific data supporting the figure electrodynamic tethered subsatellite experiments by the Space Shuttle. Vehicle charging due to dc beam emission up to 80 mA in the 150-200 km altitude range was repeatedly measured by both Langmuir and floating probes, and was found to be usually less than 10 V. During the 80 mA emission, clear evidence for the ignition of a beam-plasma discharge was obtained. In a tether deployment experiment, it was found that the tether wire acted as an antenna whose impedance decreased with the extension of the wire both in high-frequency and very low-frequency bands. Substantial rocket charging was observed during periods of electron-beam very low-frequency pulsing.

Sasaki, S.↗

NASA NTRS1983

Nonthermal components of low energy electrons in the ionospheric E and F region

Rocket-borne instrument observations of very low energy electrons' energy distribution in the ionospheric E and F regions showed the regions to exist where an enhanced, high energy tail of thermal electrons appeared. One such appearance was amid a region of high electron temperature, T(e),associated with the Sq anomaly, where there were large T(e) deviations from the neutral temperature. The associated electron heating was most intense at 107 km, gradually decreasing toward 130 km, where both the T(e) and the excess high energy tail became small. In the second region, excess electrons appeared in the high energy tail at 135 km, reached an intensity peak at 150 km, and gradually decreased toward 210 km. It is suggested that the anomalously elevated T(e) and the enhanced energy tail in the first region were locally generated by some dynamo current-related mechanism distinct from Joule heating. The second region's high energy tail is also related to ionospheric currents.

Oyama, K. I.↗

NASA NTRS1982

Measurement of vehicle potential using a mother-daughter tethered rocket

The equipment, experimental design, and results of mother-daughter tethered probes for measuring the potential of a spacecraft are described. The object was to inject a probe into the ionosphere by rocket and then lower an impedance voltage monitor-equipped section of the probe by means of a highly insulated wire. The mother probe, also carrying voltage monitors, would inject charges into the plasma that would be measured at both ends of the tether. Instrumentation on the daughter probe included voltage current monitors and a Langmuir probe, while the mother payload also carried a charge probe, floating probe, a Langmuir probe, and an impedance probe. The first launch was from Japan in 1980, and operations confirmed that Langmuir probes with area ratios less than 400:1 can produce changes in the vehicle potential if probe voltages of more than 10 V are applied in the collection mode. A ratio of 200:1 was sufficient for the daughter probe with voltages of 5 V. The experiment is concluded to verify the tethered probe method of measuring vehicle potential.

Williamson, P. R.↗

NASA NTRS1981

Shuttle Orbiter tethered subsatellite for exploring and tapping space plasmas

Consideration is given to the possibilities for studies in space plasma physics offered by a subsatellite mechanically tethered above the Space Shuttle Orbiter by a long conducting wire. The proposed experiment, designated the Shuttle Electrodynamic Tether Systems (SETS) is based on the concept of collecting electrons at the subsatellite and ejecting them from the Orbiter, made possible by the emf generated by the motion of the tether across geomagnetic field lines. The power generated in this manner can be used both for practical purposes within the Orbiter and for the creation of large-amplitude plasma and electromagnetic waves within the surrounding plasma. For a conducting spherical subsatellite 30 m in diameter with a 10-km tether drawing 1 A, calculations show that emfs on the order of 1000-2000 V and energy dissipation of as much as 10,000 W can be obtained, accompanied by the generation of two regions of net electric charge in the ionosphere. Scientific studies considered for SETS include the measurement of MHD waves artificially generated in the ionosphere, the investigation of current-driven plasma instabilities, VLF wave generation and the simulation of electrodynamics associated with the motion of celestial bodies through plasma.

Banks, P. M.↗

NASA NTRS1980

Is T/e/ equal to T/n/ at the heights of 100 to 120 km

Low and midlatitude lower E-region electron temperature profiles which were obtained by means of an in situ probe were collected. Profiles which are discussed here cover the heights of 90-120 km and measurement reliability at these heights is discussed mainly in terms of electrode contamination and aerodynamical heating. Although measurement errors might exist in some of the electron temperature profiles, it is conclusively shown that daytime electron temperature is very often much higher than the possible neutral temperature and T(e) is rarely equal to T(n).

Oyama, K. I.↗