Engineering topics
Publications and source records attributed to Freeman, J..
An understanding of the structural and compositional controls on the Raman features of the major types of phyllosilicates is presented. Additional information is contained in the original extended abstract.
A Raman survey on a flat-sawn rock slab provides the major mineralogy of martian meteorite Los Angeles. Three unreported accessory minerals and seven terrestrial alteration products and contaminants (organic and inorganic) were also found. Additional information is contained in the original extended abstract.
This document contains preliminary concepts for mining and beneficiation of lunar regolith from a 50 metric ton/day mine. Assumptions for the design are outlined below. Lunar regolith is the material to be mined. Since it is already a fine-grained material, the two steps of crushing and breakup from a rock surface are eliminated. The size of the operation was set at 50 metric tons of regolith/day for a three-year period. Operations will occur around the clock to make most efficient use of equipment, thus we assume 24 hr/day. For simplicity we have assumed that the lunar regolith has a uniform density of 1.68 and that it can be mined to a depth of 6 m. No research was done on power supply or distribution. It was left to others to consider the various trade-offs between nuclear and solar power and to design the needed utility system.
Brief discriptions of the following 13 experiments are included: ultrahigh vacuum petrology facility; artificial comet free flyer; artificial comet (tethered); cosmic dust detector; cosmic dust collector; dust collection using tethered satellites; artificial magnetosphere; microgravity petrological studies; slitless ultraviolet spectrometer; orbital determination and capture experiment (ODACE); high velocity sputtering of amorphous silicates; particle release experiments; and calibration of gamma and X-ray remote sensingprobes.
A photometer sensitive at the 584 A line of He 1, incorporating a helium gas resonance absorption cell, was flown on the Apollo-Soyuz Test Project in July 1975. The instrument observed much of the night-time sky, and returned 42 min of usable data. The data were analyzed by fitting to a model of resonant scattering of solar 584 A flux from nearby interstellar helium. Good model fits were obtained for an interstellar gas bulk velocity vector pointing toward alpha = 72 deg, delta = +15 deg, with speed 20 km/s, with interstellar medium temperatures from 5000 to 20,000 K and with neutral interstellar helium density (8.9 plus or minus 10 to the -3rd/cu cm). In the context of theoretical studies of the interstellar medium by McKee and Ostriker (1977), the results may indicate that the sun lies in the warm, partially ionized periphery of a cold interstellar cloud, surrounded by a high-temperature gas heated by old supernova remnants.
An upper bound for the number density of neutral helium in the local interstellar medium of 0.004 + or - 0.0022 per cu cm was previously reported, based on extreme-ultraviolet telescope observations at 584 A made during the 1975 Apollo-Soyuz Test Project. A variety of evidence is found which indicates that the 584-A sensitivity of the instrument declined by a factor of 2 between the last laboratory calibration and the time of the measurements. The upper bound on the helium density is therefore revised to 0.0089 + or - 0.005 per cu cm.
During the Apollo-Soyuz Test Project, an extreme-ultraviolet photometer with a cyclically operated helium gas-absorption cell observed the daytime sky from an orbital altitude of 225 km. When the line of sight pointed more than 60 deg from the sun, the instrument detected 2 to 70 rayleighs of flux scattered from neutral geocoronal helium at wavelengths from 504 to 584 A. The instrument also detected other radiation in the band 500-700 A of similar spatial distribution to the helium flux, which was definitely not due to the He I 584-A spectral line and which has not been detected by previous experimenters in data from 400 km altitude. Possible sources of this radiation are discussed.
Evidence for an extreme-ultraviolet source in the constellation Pavo is presented. The potential source, which was observed in the 500-780-A band, has an intensity of 35 + or - 9 mJy. Positional overlap suggests possible identification with the ultraviolet-intense star HD 192273 and/or the high-galactic-latitude X-ray source 3U 1959-69.
During the Apollo-Soyuz Test Project, an extreme-ultraviolet telescope observed the region of the sky from which the interstellar medium approaches the sun. The instrument had a tin filter whose bandpass included the 584-A line of neutral helium. The observations set an upper bound for the number density of neutral helium in the local interstellar medium of 0.004 + or - 0.0022 per cu cm, which is significantly lower than previously reported. The stated error is dominated by the present uncertainty in the solar 584-A flux, which is taken to be approximately 200 million photons/sq cm per sec at earth's orbit. The result is not consistent with previous resonant-scattering Ly-alpha observations of interstellar hydrogen passing through the solar system, which generally yield a hydrogen number density of about 0.1 per cu cm, unless interstellar helium is locally depleted below its cosmic abundance. The result is consistent with cosmic abundances if the much lower average hydrogen densities inferred from recent column-density measurements to nearby hot stars are in fact representative of the immediate solar neighborhood.
A four-channel photometer sensitive to two solar EUV lines which are resonantly scattered by helium gas was developed for flight on the Apollo-Soyuz Test Project. Two channels observed the 58.4-nm line of He I and used helium gas resonant absorption cells to determine the intensities of the center and wings of that line. The other two channels observed the 30.4-nm line of He II. The instrument surveyed much of the celestial sphere during a series of slow rolling maneuvers by the Apollo spacecraft. The experiment operated properly, and usable data were obtained. Study of the distributions of flux seen, and of the ratio 58.4-nm fluxes seen with gas cells full and empty, will refine current understanding of several poorly known properties of the local interstellar medium. Study of the 30.4-nm flux distribution will refine present knowledge of the structure of the earth's plasmasphere.
Results are reported for observations of solar 584-A flux resonantly scattered by the 1s(2)-1s2p transition of neutral interstellar helium. A photometer equipped with a helium gas-absorption cell and flown aboard a sounding rocket to a peak altitude of 185 km was employed to observe the sky in Perseus. The data reduction procedure is described, including subtraction of the terrestrial atmospheric background, calculation of the solar flux, and reduction of the number density of scatters to a function of phase-space parameters of the local interstellar medium. The ratio of 584-A fluxes observed with the gas cell full and empty is computed and compared with numerical models of the interstellar-helium flow through the solar system. The results show that the bulk speed of the distant interstellar medium with respect to the sun is unlikely to be less than 10 to 15 km/s, at the 2-sigma level. Since this value is inconsistent with results obtained from Lyman-alpha observations, it is suggested that either the total ionization rate for helium is variable or present models of the behavior of the local interstellar medium need further refinement.
A photometer sensitive in the 584-A line of He I, incorporating a helium-gas absorption cell, has been developed. The helium is confined at a pressure of 0.2 torr between thin-metal-foil broad-band ultraviolet filters. The cell contains sufficient helium to absorb 584-A radiation scattered from atmospheric helium. The ratio of fluxes seen with the cell full and empty provides a valuable datum for fitting models of the local interstellar medium, which is independent of solar 584-A flux, interstellar helium density, and photometer sensitivity.-
The Apollo Soyuz Test Project Interstellar Helium Glow Experiment (MA-088) studied the motion of helium in the local interstellar medium as that medium passed through the solar system to determine several poorly known properties of the local interstellar gas. The instrument used was a photometer sensitive to two solar extreme ultraviolet spectral lines that are resonantly scattered by helium gas. The instrument surveyed the entire celestial sphere during a series of slow, rolling maneuvers by the Apollo spacecraft. The equipment operated properly, and usable data were obtained.