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Hallgren, D. S.

Publications and source records attributed to Hallgren, D. S..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Magellan - A balloon-borne collection technique for large cosmic dust particles

The paper describes a balloon-borne system for collecting large (50 to a few hundred micrometers in the major dimension) solid particles falling through the atmosphere at an altitude of about 30 km which are postulated to be fragments of larger cosmic particles or bodies which disintegrate on entering the atmosphere. The major component of the system is the collection surface - a funnel, 7.2 m in diameter, fabricated from mylar, 12 microns thick, and lightly coated with aluminum. Also described is the sample collector, which collects the particles gathered in the apex of the cone. Two successful flights of short duration using zero-pressure balloons have been achieved. Some examples of particles collected are shown. Mg, Al, Si, S, K, Ca, Ti, and Fe have been detected in these particles by energy dispersive X-ray analysis.

Wlochowicz, R.↗
NASA NTRS1976

Micrometeorite penetration effects in gold foil

Penetration structures revealed by a Skylab experiment dealing with exposure of single and double layers of 500-800 A thick gold foil to micrometeorites are examined. Examination of all double-layered gold foils revealed that particles producing holes of any type greater than 5 microns in diameter in the first foil break up into many fragments which in turn produce many more holes in the second foil. Evidence of an original particle is not found on any stainless steel plate below the foils, except in one instance. A precise relationship between the size of the event and the mass of the particle producing it could not be determined due to the extreme morphological variety in penetration effects. Fluxes from gold foil and crater experiments are briefly discussed.

Hallgren, D. S.↗
NASA NTRS1974

Near-earth cosmic dust results from S-149

Three space exposures (34, 46 and 33 days) of thin films and polished metal plates with a total area of 0.12 sq m per exposure were carried out during Skylab via the S-149 experiment. Study of the materials recovered indicates that the S-149 experiment contains important information concerning cosmic dust in the near-earth vicinity. Craters and penetration holes have been found ranging from 135 micron diameter to less than 0.5 micron. A cosmic dust flux curve in the mass range from 10 to the minus 16th to 10 to the minus 7th grams is presented. Evidence is given concerning the directional characteristics of the particles and their breakup in near-earth space is presented.

Hemenway, C. L.↗
NASA NTRS1973

Preliminary results from the noctilucent sampling from Kiruna in 1970.

On Aug. 8, 1970 at 0148 and 0354 local time, two Pandora sounding rocket payloads were launched from the ESRO range in Kiruna, Sweden, during a noctilucent cloud display. Large numbers of particles were collected, many of which appear to be micrometeorites coated with a low density material. Typical electron micrographs are shown, and numerical densities as a function of altitude are given. Particle composition information has been obtained by use of dispersive X-ray analysis equipment attached to our Philips EM 300 electron microscope.

Hallgren, D. S.↗
NASA NTRS1973

Noctilucent cloud sampling by a multi-experiment payload.

Two multi-experiment payloads were launched into noctilucent cloud displays above Kiruna, Sweden, on the nights of July 31 and Aug. 1, 1971. The payloads were part of the continuing Pandora II cosmic dust collection series and included: (1) Pandora 2 dust collection with in-flight shadowing photoelectric polarimeters to measure scattered light at 4100 and 5400 A, a plasma detector and an ion probe, and piezoelectric microphones. These payloads attempted to investigate noctilucent clouds by four simultaneous and independent techniques. The photometric data indicate that the first payload passed through a cloud, while the second payload did not. These results are confirmed by the particle collection experiment which indicates a higher collection on the first payload. Analysis of the chemical composition of the collected particles indicates an unusual amount of high atomic number elements.

Hallgren, D. S.↗
NASA NTRS1973

Do some of the sub-micrometer cosmic dust particles come from the sun.

Studies of cosmic dust particles collected at altitudes of 80 to 120 km over White Sands, New Mexico, and at times of noctilucent clouds over Kiruna, Sweden, indicate that an anomalously high atomic weight contribution is present within those particles collected at Kiruna. The elements observed are inconsistent with an origin due to atomic bomb fallout, meteoroidal crumbling, lunar ejecta, or comets. Many of these heavy elements may be stable in particulate form at the relatively high temperatures found in the coolest regions of the solar atmosphere. Some implications of the sun as the source of a significant component of cosmic dust are discussed.

Hemenway, C. L.↗
NASA NTRS1972

Stardust.

Rocket experiments were conducted to collect particles from noctilucent clouds at Kiruna, Sweden. The Pandora II inflight shadowing technique considered by Hallgren and Hemenway (1971) was used in the experiments. This technique makes it possible to study the collected particles as a function of time and altitude intervals. The particles observed consisted of an irregular electron-opaque core surrounded by a rounded, low density material. X-ray and electron opacity data suggest that the abundances of the heavy elements, such as Hf and Ta, in the particles are comparable to those of the light elements, such as Al and Si.

Hemenway, C. L.↗
NASA NTRS1972

Preliminary examination of Surveyor 3 components for impact phenomena

Two pieces of the Surveyor 3 spacecraft recovered during the Apollo 12 mission were examined for secondary lunar ejecta and micrometeorite impacts. One piece was section E of the aluminum strut; the other was the nickel-coated beryllium television camera mirror.

Hallgren, D. S.↗
NASA NTRS1971

Experiment S012: Micrometeorite collection

The micrometeorite activity in a near-earth environment and the effect of the environment on microorganisms were studied by exposure of polished metal and plastic surfaces to the environment outside the Gemini spacecraft. Preliminary results are summarized as follows: (1) The cumulative influx rate in the size ranges from 10 to the minus 15th power to 10 to the minus 14th power gram was approximately 2 particles/ sq m/sec, as determined on the Gemini 12 mission; (2) The cumulative influx rate in the same mass range, as determined by the data from the Gemini 9 mission was almost 200 particles/ sq m/sec; and (3) The large particle cumulative influx rate was about 3 x 0.00001 particle/ sq m/sec, with a mass of the order of 10 to the minus 7th power gram. No living organisms could be found on the sterile collecting surfaces after recovery and handling.

Hemenway, C. L.↗
NASA NTRS1968

Survival of micro-organisms in space.

Survival of Penicillium roqueforti Thom, Coliphage T-1, Bacillus subtilis and tobacco mosaic virus exposed to space on Gemini flights

Hallgren, D. S.↗