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Milder, N. L.

Publications and source records attributed to Milder, N. L..

11 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Optical radiation from regions downstream of mercury bombardment thrusters

A 0.5 meter focal length, plane grating monochromator was used to measure the radiance of spectral radiation emanating from regions downstream of a mercury bombardment thruster. The wavelength range investigated was 2800 A. This radiation was due primarily to the radiative decay of excited mercury atoms exhausted from the thruster. Radiance values ranged from 10 to the minus 11th power to 10 to the minus 9th power W/sq cm sr, varying with wavelength. For resonant radiation, the spectral radiance may exceed 10 to the minus 8th power W/sq cm sr. From such radiance measurements, it was concluded that the thruster background radiation should not interfere with the control functions of a star tracker viewing through the thruster exhaust, provided that the tracker is designed to operate with a sufficiently small field of view.

Milder, N. L.↗
NASA NTRS1972

Optical radiation from regions downstream of mercury bombardment thrusters.

Use of a 0.5-m focal length, plane grating monochromator to measure the radiance of spectral radiation emanating from regions downstream of a mercury bombardment thrustor in the wavelength range investigated was 2800 to 6000 A. This radiation was due primarily to the radiative decay of excited mercury atoms exhausted from the thrustor. Radiance values ranged from 10 to the minus 11th to 10 to the min scm/ster varying with wavelength. For resonant radiation, the spectral radiance may exceed 10 to the minus 8th W/sq cm/ster. From such radiance measurements, it was concluded that the thrustor background radiation should not interfere with the control functions of a star tracker viewing through the thrustor exhaust, provided that the tracker is designed to operate with a sufficiently small field of view. Problems may be encountered, however, during the spacecraft acquisition phase where a larger field of view may be required. Here the thrustor exhaust radiation may be comparable to the star light flux. This problem may be circumvented by locating the tracker view axis so as not to view downstream of the thrustor.

Milder, N. L.↗
NASA NTRS1972

Ion thruster diagnostics using spectral line amplitudes.

The optical radiation from the plasma discharge of an electron bombardment mercury ion thruster was investigated. This work extends and refines earlier measurements, correcting certain ambiguities that arose in the analysis of line amplitudes. Using the measured ratio of the Hg I line amplitude at 3655 A to that at 3650 A, a theory incorporating a bimodal electron distribution (Maxwell electrons plus primary electrons) was used to obtain the average electron temperature and primary electron fraction in the thruster ion chamber. The electron temperature ranged from about 1.2 eV to 6.6 eV; whereas the primary electron fraction varied from zero percent to about 5 percent. These values depended upon the discharge voltage and the radial location of the measurement. The percentage of doubly ionized mercury produced in the chamber was also determined as a function of discharge voltage.

Milder, N. L.↗
NASA NTRS1971

Characteristics of the optical radiation from Kaufman thrusters

The optical radiation from plasma discharges of electron-bombardment mercury-ion thrusters was investigated. Spectrographic measurements indicated that the discharge was composed primarily of mercury atoms and singly charged ions. Excitation spectra of doubly charged mercury ions was measured to obtain the fraction of such ions in the discharge. Accomplishments of spectroscopic measurements of a hollow cathode thruster included the identification of two diagnostic lines in the mercury spectrum and the interpretation of the spectral amplitudes in terms of a superposition of primary and Maxwellian electron distributions. Potential application of optical techniques to thruster control applications was also suggested by the measurements.

Milder, N. L.↗
NASA NTRS1971

Ion thruster diagnostics using spectral line amplitudes

The optical radiation from the plasma discharge of an electron bombardment mercury ion thrustor was investigated. Using the measured ratio of the Hg I line amplitude at 3655 A to that at 3650 A, a theory incorporating a bimodal electron distribution (Maxwell electrons plus primary electrons) was used to obtain the average electron temperature and primary electron fraction in the thruster ion chamber. The electron temperature ranged from about 1.2 eV to 6.6 eV; whereas the primary electron fraction varied from zero percent to about 5 percent. These values depended upon the discharge voltage and the radial location of the measurement. The percentage of doubly ionized mercury produced in the chamber was also determined as a function of discharge voltage.

Milder, N. L.↗