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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Spatial distribution of Ar-40/Ar-39 ages in lunar breccia 14301.

The distribution of stable and radioactive argon isotopes in a lunar breccia has been measured in situ by laser probe mass spectrometry. This new technique determines the spatial distribution of Ar-40/Ar-39 ages on less than .1 milligram of material. Calculated Ar-40/Ar-39 ages of clasts within this breccia are 3.7 and 2.9 b.y. Parentless radiogenic Ar-40 exists within the fine-grained matrix and appears to have been trapped simultaneously with solar argon. This 'atmosphere' of ambient gas appears to have been incorporated into the rock by an impact event not more than 3 b.y. ago.

Megrue, G. H.↗
NASA NTRS1979

Radioactive and magnetic investigations

Age and growth pattern determination of manganese nodules were explored. Two methods are discussed: (1) measurement of the presence of radioactive iodine isotopes; which is effective only up to 3.105 years, and (2) measurements of magnetism. The growth rates of three nodules were determined. The surface of the nodule was recent, and the overall age of the nodule could be determined with accuracy of better than 30%. Measurement of paleomagnetic effect was attempted to determine wider age ranges, however, the measured sign changes could not be interpreted as paleomagnetic reversals.

Heye, D.↗
NASA NTRS1986

Cosmogenic nuclei

Cosmogenic nuclei, nuclides formed by nuclear interactions of galactic and solar cosmic rays with extraterrestrial or terrestrial matter are discussed. Long lived radioactive cosmogenic isotopes are focused upon. Their uses in dating, as tracers of the interactions of cosmic rays with matter, and in obtaining information on the variation of primary cosmic ray flux in the past are discussed.

Raisbeck, G. M.↗
NASA NTRS1987

Measurement of Human Blood and Plasma Volumes

Report reviews techniques for measuring blood-plasma volume in humans. Common technique of using radioactive iodine isotope to label plasma albumin involves unwarranted risks from low-level radiation. Report emphasizes techniques using Evans-blue-dye (T-1824) labeling of albumin, hematocrit or hemoglobin/hematocrit measurements, or blood densitometry. In Evans-blue-dye technique, plasma volume determined from decrease in dye concentration occurring after small amount of dye solution injected into circulatory system. Subjection of Evans blue dye to test for carcinogenicity gave negative results.

Greenleaf, J. E.↗
NASA NTRS1987

Origin and transport of high energy particles in the galaxy

The origin, confinement, and transport of cosmic ray nuclei in the galaxy was studied. The work involves interpretations of the existing cosmic ray physics database derived from both balloon and satellite measurements, combined with an effort directed towards defining the next generation of instruments for the study of cosmic radiation. The shape and the energy dependence of the cosmic ray pathlength distribution in the galaxy was studied, demonstrating that the leaky box model is not a good representation of the detailed particle transport over the energy range covered by the database. Alternative confinement methods were investigated, analyzing the confinement lifetime in these models based upon the available data for radioactive secondary isotopes. The source abundances of several isotopes were studied using compiled nuclear physics data and the detailed transport calculations. The effects of distributed particle acceleration on the secondary to primary ratios were investigated.

Wefel, John P.↗
NASA NTRS2004

Measurement of the Abundance of Radioactive Be-10 and Other Light Isotopes in Cosmic Radiation Up to 2 GeV /Nucleon with the Balloon-Borne Instrument Isomax

The Isotope Magnet Experiment (ISOMAX), a balloon-borne superconducting magnet spectrometer, was designed to measure the isotopic composition of the light isotopes (3 les than or = Z less than or = 8) of cosmic radiation up to 4 GeV/nucleon with a mass resolution of better than 0.25 amu by using the velocity versus rigidity technique. To achieve this stringent mass resolution, ISOMAX was composed of three major detector systems: a magnetic rigidity spectrometer with a precision drift chamber tracker in conjunction with a three-layer time-of-flight system, and two silica-aerogel Cerenkov counters for velocity determination. A special emphasis of the ISOMAX program was the accurate measurement of radioactive Be-10 with respect to its stable neighbor isotope Be-9, which provides important constraints on the age of cosmic rays in the Galaxy. ISOMAX had its first balloon flight on 1998 August 4-5 from Lynn Lake, Manitoba, Canada. Thirteen hours of data were recorded during this flight at a residual atmosphere of less than 5 g/sq cm. The isotopic ratio at the top of the atmosphere for Be-10/Be-9 was measured to be 0.195 +/- 0.036 (statistical) +/- 0.039 (systematic) between 0.26 and 1.03 GeV/nucleon and 0.317 +/- 0.109(statistical) +/- 0.042(systematic) between 1.13 and 2.03 GeV/nucleon. This is the first measurement of its kind above l GeV/nucleon. ISOMAX results tend to be higher than predictions from current propagation models. In addition to the beryllium results, we report the isotopic ratios of neighboring lithium and boron in the energy range of the time-of-flight system (up to approx. 1 GeV/nucleon). The lithium and boron ratios agree well with existing data and model predictions at similar energies.

Hams, T.↗
NASA NTRSDate not supplied

Noble Gases in Individual Particles From Bennu: Investigating the Origin of Gas-Rich Asteroidal Material

One of the driving hypotheses of the OSIRIS-REx mission [1] is that B-type asteroid Bennu formed beyond the snow line by accretion of material of the protoplanetary disk. Hence Bennu is expected to be rich in highly volatile elements. Among them, noble gases are chemically inert and their abundances and isotope compositions are shaped by physical processes such as radioactivity, irradiation, and isotope fractionation [2]. Hence studying the noble gas composition of Bennu's grains can contribute to testing Hypotheses 4 (formation beyond the snow line), 5 (geological activity), and 6 (catastrophic disruption) of the OSIRIS-REx mission [1]. Here we report preliminary data obtained on particles from asteroid Bennu using our all-noble-gas (He to Xe) analytical system installed at the Centre de Recherches Pétrographiques et Géochimiques (CRPG) Nancy (France) [3]. A companion presentation presents nitrogen-Ne-Ar data [4].

B. Marty↗
NASA NTRS2002

Potential Operating Orbits for the SAFE-400

Safety must be ensured during all phases of space fission system design, development, fabrication, launch, operation, and shutdown. One potential space fission system application is fission electric propulsion (FEP), in which fission energy is converted into electricity and used to power high efficiency (Isp is greater than 3000s) electric thrusters. For these types of systems it is important to determine which operational scenarios ensure safety while allowing maximum mission performance and flexibility. Space fission systems are essentially non-radioactive at launch, prior to extended operation at high power. Once high power operation begins, system radiological inventory steadily increases as fission products build up. For a given fission product isotope, the maximum radiological inventory is typically achieved once the system has operated for a length of time equivalent to several half-lives. After that time, the isotope decays at the same rate it is produced, and no further inventory builds in. For an FEP mission beginning in Earth orbit, altitude and orbital lifetime increase as the propulsion system operates. Two simultaneous effects of fission propulsion system operation are thus (1) increasing fission product inventory and (2) increasing orbital lifetime. Phrased differently, as fission products build up, more time is required for the fission products to naturally convert back into non-radioactive isotopes. Simultaneously, as fission products build up, orbital lifetime increases, providing more time for the fission products to naturally convert back into non-radioactive isotopes. Operational constraints required to ensure safety can thus be quantified.

Houts, Mike↗
NASA NTRS1972

Search for extinct natural radioactivity of Pb205 via thallium-isotope anomalies in chondrites and lunar soil.

Thallium and Pb204 contents were determined by stable-isotope-dilution analysis in 16 chondrites, one achondrite, and Apollo 11 and 12 lunar fines. Meteoritic thallium contents vary over a large range, 0.02 to 100 ppb, corresponding to the fact that thallium is a highly fractionated volatile element. Lunar thallium contents are less than 5 ppb. The Tl205/Tl203 ratio was determined in most of the samples, with precision ranging from 0.03% to several percent depending mainly on the amount of thallium present. No variations from the terrestrial ratio were observed. The chondritic isochron slope for Pb205 (13.8-m.y. half-life) is less than or equal to 0.00009 (99% confidence level), corresponding to an interval of at least 60 m.y. and possibly exceeding 120 m.y. between the termination of s-process nucleosynthesis and the lead-thallium fractionations.

Huey, J. M.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Isotopes in Meteorites

The session"Isotopes in Meteorites" consisted of the following presentations:The Common Property of Isotopic Anomalies in Meteorites; Revised Production Rates for 22Na and 54Mn in Meteorites Using Cross Sections Measured for Neutron-induced Reactions; Modeling of 14C and 10Be Production Rates in Meteorites and Lunar Samples; Investigating Xenon Isotopic Fractionation During Rayleigh-type Distillation; The Mean Life Squared Relationship for Abundances of Extinct Radioactivities; and Magnesium Isotopic Fractionation of Forsterite During Evaporation from Different Crystallographic Surfaces.

Source record↗
NASA NTRS1983

Cosmic-ray isotopic composition

The 'age' of the cosmic rays and the origin of cosmic ray source matter are discussed. General approaches to the interpretation of the abundances of secondary radioactive nuclides are reviewed using Be-10 as an illustration. The present state of Be-10 based cosmic ray age determinations are summarized, briefly mentioning some recent results based on the isotope Al-26. The effects of nonhomogeneous propagation models on the interpretation of the radioactive isotope observations are mentioned. The cosmic ray source isotopic composition is discussed, emphasizing the neon composition. Mass histogram findings on the abundance of various elements in cosmic rays are described and possible reasons for some abundance enhancements are considered.

Wiedenbeck, M. E.↗