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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The sterilization parameters for the Viking lander of D sub 125 C = 30 minutes and z = 21 C for the exposed bioburden were derived from the experimental findings of several laboratories conducting thermal inactivation studies on Bacillus subtilis var. niger by dry heat. The moisture constraint, that the sterilizing gas shall be less than 25 percent relative humidity at standard conditions of 0 C and 760 mm Hg pressure, was added in recognition of the profound influence of water vapor on the time and temperature required for thermal inactivation of these spores. Data is presented demonstrating that the application of the moisture parameter does not significantly change the D sub 125 C and z values of 30 minutes and 21 C, respectively. Data are presented also to show the maximum influence that could be expected by decreasing the humidity to near zero percent relative humidity at 105, 113, and 125 C.

Campbell, J. E.↗
NASA NTRS1972

Shock phenomena in interplanetary space

The performance of the solar wind near one astronomical unit is discussed. The solar wind is shown to act as a compressible, supersonic, magnetogasdynamic fluid. The creation of magnetogasdynamic shock waves by solar flares and other causes is analyzed. The observations of shock fronts and the flows behind these fronts are discussed and synoptic views of the observations are described. Theoretical concepts and models are summarized.

Burlaga, L. F.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

An experimental sterilization facility was developed to simulate conditions that will be encountered during terminal sterilization of space vehicles. The system consists of a temperature controlled oven with a nitrogen gas stream containing a known concentration of water. Moisture analyzers are utilized to monitor the gas flowing over spore samples contained in the oven. In its original configuration, no provision was made for the control of water vapor during the sterilization cycle. Because moisture profoundly influences the thermal inactivation of bacterial spores, an upper limit for the moisture content in the gas used to sterilize the space vehicle was established (25% RH at 0 C STP). Accordingly, a controller was developed and installed to provide these conditions in the experimental sterilization facility.

Wimsatt, J. C.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The thermal inactivation curve for Bacillus subtilis var. niger spores on the Viking lander is examined. Tests were conducted at 113 C and 25% RH, and over a wide range of temperatures using .001% RH and additions of P2O5 to dry the environment. Results show the 25% RH environment did not significantly reduce the survival curve, while the survival curves for spores treated under the drier .001% RH environment was reduced by a factor of 3.

Campbell, J. E.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Studies were made of atypical organisms found in Bacillus subtilis var. niger spore colonies. Efforts were aimed at: (1) determining the heat sensitivity of these atypical white spores treated under dry heat conditions and their influence on the nature of the survival curve, (2) preparing a new spore crop obtained from spore isolates by purification procedures, and (3) comparing spore crops obtained from Cape Kennedy (SSM-10) and Minnesota (Minn. sp. AAEF) with the old Cincinnati and new purified Cincinnati spore crop under dry heat conditions.

Campbell, J. E.↗
NASA NTRS1973

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The mechanism for thermal inactivation of bacterial spores under moist or dry heat was studied. Experimental conditions were established relating to spore loss of heat resistance and loss of optical density as a measure of the rate and extent of germination in spore suspensions. Events occurring during germination were correlated with phase darkening (refractility and non-refractility of spores), stainability characteristics of heat and non-heat treated spores, morphological characteristics, and studies on swelling of spores by an increase in packed cell volume.

Campbell, J. E.↗
NASA NTRS1974

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

The uses of scanning electron microscopy in assessing changes that occur in spores exposed to wet and dry heat cycles at elevated temperatures were examined. Several species of Bacillus and other nonspore-forming species of organisms were used for the experiment. Surface morphology of viable and nonviable organisms was clearly detectable by this method, making it a potentially useful technique for investigating microbial inactivation on space vehicle surfaces and components. Micrographs of the spores and bacterial cells are provided.

Campbell, J. E.↗
NASA NTRS1974

Bursts of relativistic electrons from Jupiter observed in interplanetary space with the time variation of the planetary rotation period

Bursts of Jovian electrons in the energy range 3 to 30 Mev have been detected to distances of the order of 1 AU from the planet. The duration of each burst was about two to three days, and the maximum intensity increased with increasing distance from the sun. These events could not be correlated with known solar activity. The conclusion that these electrons originated at Jupiter and were accelerated within the Jovian magnetosphere is based on observations of three of these bursts. The power spectrum of the temporal variations of the 6- to 30-MeV electron flux showed a persistent peak at Jupiter's rotation frequency (corresponding to the ten hour rotation period) out to distances greater than 100,000,000 km from the planet. The slope, or spectral index, of the differential energy spectrum measured as a function of time displayed the ten-hour cyclic variation in the value of the index, which was earlier found to be characteristic of the electrons within the Jovian magnetosphere.

Chenette, D. L.↗
NASA NTRS1974

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Dry heat sterilization of spacecraft was investigated by studying the production of spore crops, and thermal inactivation of the spores, and bacillus subtillus. Spore assays were made by conventional plate count methods, and survival curves for the spores are presented. The results indicate that the inherent resistance of spores from a parent cell can be maintained.

Campbell, J. E.↗
NASA NTRS1975

Calculations of the cosmic ray modulation in interplanetary space taking into account the possible dependence of the transport travel for the scattering of the particles and of the velocity of the solar winds on the angles they make with the helioequator plane: The case of isotropic diffusion

The modulation of galactic cosmic rays is studied by the magnetic heterogeneities stream on the assumption that the diffusion coefficient is reduced whereas the solar wind velocity is increased with the growth of the angle between the sun's rotation axis and the direction of solar plasma motion. The stationary plane problem of isotropic diffusion is solved as it applies to two cases: (1) with due account of particle retardation by the antiphermium mechanism; and (2) without an account of the above mechanism. This problem is solved by the grid method in the polar coordinate system. The results of the calculations are followed by a discussion of the method of solution and of the errors.

Dorman, L. I.↗
NASA NTRS1974

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

Dry heat inactivation characteristics were compared for 4-6 (B. brevis) spores and microbes from the Cincinnati soil samples at 105, 112, and 125. Characterized were the survival curves of 4-6 (B. brevis) spores at 112, 115, 118, 120, and 125 C, and 1.2 microgram of water per ml of headspace air (closed tin-can system), and the morphological characteristics of 4-6 (B. brevis), 6-12 (B. lentus), 7-11 (B. coagulans), and B. subtilis var. niger spores by scanning electron microscopy.

Reyes, A. L.↗
NASA NTRS1975

Ecology and thermal inactivation of microbes in and on interplanetary space vehicle components

A series of experiments was conducted to determine the dry heat resistance of microorganisms in soil obtained from Denver Colorado, Pasadena California, Kennedy Space Center Florida, and Cincinnati Ohio. The results of the KSC terminal sterilization cycle experiment are given in graphs. The average number of viable organisms per m1 was calculated for 18 replicate soil samples for each sample area and points plotted equivalent to 30 hr exposure at 112 C. The result showed a reduction of 3 logs from the initial population for both KSC and Cincinnati soil samples. Results from other areas are given in graphs.

Reyes, A. L.↗
NASA NTRS1975

Cosmic ray propagation in interplanetary space

The validity of the test-particle picture, the approximation of static fields, and the spatial-diffusion approximation are discussed in a general way before specific technical assumptions are introduced. It is argued that the spatial-diffusion equation for the intensity per unit energy has a much wider range of applicability than the kinetic (Fokker-Planck) equation it is derived from. This gives strong weight to the phenomenological propagation theory. The general success (and possible failure at small energies) of the phenomenological theory for the modulation of galactic cosmic rays and solar events is described. Apparent effects such as the 'free boundary' are given disproportionate weight since they establish the connection with the detailed plasma physics of the solar wind. Greatest attention is paid to the pitch-angle diffusion theory. A general theory is presented which removes the well-known secularities of the quasi-linear approximation. The possible breakdown of any pitch-angle diffusion theory at very small energies is perhaps connected with the observed 'turn up' of the spectrum at low energies. A first attempt to derive the spatial dependence of the diffusion coefficient in the solar cavity, using such a divergence free scattering theory, is described and compared with recent observations out to 5 AU.

Voelk, H. J.↗