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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2017

Erosion Results of the MISSE 8 Polymers Experiment After 2 Years of Space Exposure on the International Space Station

Polymers and other oxidizable materials on the exterior of spacecraft in the low Earth orbit (LEO) space environment can be eroded due to reaction with atomic oxygen (AO). Therefore, in order to design durable spacecraft, it is important to know the LEO AO erosion yield (E(sub y), volume loss per incident oxygen atom) of materials susceptible to AO reaction. A spaceflight experiment, called the Polymers Experiment, which contained 42 samples, was developed to determine the effect of solar exposure on the AO E(sub y) of fluoropolymers flown in ram, wake, or zenith orientations. The Polymers Experiment was exposed to the LEO space environment on the exterior of the International Space Station (ISS) as part of the Materials International Space Station Experiment 8 (MISSE 8) mission. The MISSE 8 mission included samples flown in a zenith/nadir orientation for 2.14 years in the MISSE 8 Passive Experiment Container (PEC), and samples flown in a ram/wake orientation for 2.0 years in the Optical Reflector Materials Experiment-III (ORMatEIII) tray. The experiment included Kapton H (Registered Trademark) witness samples for AO fluence determination in each orientation. This paper provides an overview of the MISSE 8 mission, a description of the flight experiment with details on the polymers flown, the characterization techniques used, the AO fluence for each exposure orientation, and the LEO E(sub y) results. The E(sub y) of Teflon fluorinated ethylene propylene (FEP) samples flown in ram, wake, and zenith orientations have been compared, and the E(sub y) was found to be highly dependent on orientation and therefore environmental exposure. The FEP E(sub y) was found to directly correlate with the solar exposure/AO fluence ratio showing the effect of solar radiation and/or heating due to solar exposure on FEP erosion. In addition, back-surface carbon painted FEP (C-FEP) flown in the zenith orientation had a significantly higher E(sub y) than clear FEP or Al-FEP further indicating that heating has a significant impact on the erosion of FEP. This experiment provides valuable LEO flight data on the erosion of Teflon FEP, a commonly used spacecraft thermal insulation.

Teflon↗
NASA NTRS2002

A critical period for functional vestibular development in zebrafish

We have determined a critical period for vestibular development in zebrafish by using a bioreactor designed by NASA to simulate microgravity for cells in culture. A critical period is defined as the briefest period of time during development when stimulus deprivation results in long lasting or permanent sensory deficits. Zebrafish eggs were collected within 3 hours of being laid and fertilized. In experiment 1, eggs were placed in the bioreactor at 3, 24, 30, 36, 48, or 72 hours postfertilization (hPF) and maintained in the bioreactor until 96 hPF. In experiment 2, eggs were placed in the bioreactor immediately after they were collected and maintained in the bioreactor until 24, 36, 48, 60, 66, 72, or 96 hPF. Beginning at 96 hPF, all larvae had their vestibulo-ocular reflexes (VOR) evaluated once each day for 5 days. Only larvae that hatched from eggs that were placed in the bioreactor before 30 hPF in experiment 1 or removed from the bioreactor later than 66 hPF in experiment 2 had VOR deficits that persisted for at least 5 days. These data suggest a critical period for vestibular development in the zebrafish that begins before 30 hPF and ends after 66 hPF. To confirm this, zebrafish eggs were placed in the bioreactor at 24 hPF and removed at 72 hPF. VORs were evaluated in these larvae once each day for 5 days beginning at 96 hPF. These larvae had VOR deficits that persisted for at least 5 days. In addition, larvae that had been maintained in the bioreactor from 24 to 66 hPF or from 30 to 72 hPF, had only temporary VOR deficits. In a final experiment, zebrafish eggs were placed in the bioreactor at 3 hPF and removed at 96 hPF but the bioreactor was turned off from 24 hPF to 72 hPF. These larvae had normal VORs when they were removed from the bioreactor at 96 hPF. Taken as a whole, these data support the idea that there is a critical period for functional maturation of the zebrafish vestibular system. The developmental period identified includes the timeframe during which the vestibular primary afferent neurons are born, innervate their central and peripheral targets, and remodel their central projections. Copyright 2002 Wiley-Liss, Inc.

Non-NASA Center↗
NASA NTRS1992

Studies on penetration of antibiotic in bacterial cells in space conditions (7-IML-1)

The Cytos 2 experiment was performed aboard Salyut 7 in order to test the antibiotic sensitivity of bacteria cultivated in vitro in space. An increase of the Minimal Inhibitory Concentration (MIC) in the inflight cultures (i.e., an increase of the antibiotic resistance) was observed. Complementary studies of the ultrastructure showed a thickening of the cell envelope. In order to confirm the results of the Cytos 2 experiment, we performed the ANTIBIO experiment during the D1 mission to try to differentiate, by means of the 1 g centrifuge in the Biorack, between the biological effects of cosmic rays and those caused by microgravity conditions. The originality of this experiment was in the fact that it was designed to test the antibiotic sensitivity of bacteria cultivated in vitro during the orbital phase of the flight. The results show an increase in resistance to Colistin in in-flight bacteria. The MIC is practically double in the in-flight cultures. A cell count of living bacteria in the cultures containing the different Colistin concentrations showed a significant difference between the cultures developed during space flight and the ground based cultures. The comparison between the 1 g and 0 g in-flight cultures show similar behavior for the two sets. Nevertheless, a small difference between the two sets of ground based control cultures was noted. The cultures developed on the ground centrifuge (1.4 g) present a slight decrease in comparison with the cultures developed in the static rack (1 g). In order to approach the mechanisms of the increase of antibiotic resistance on bacteria cultivated in vitro in space, we have proposed the study on penetration of antibiotics in bacterial cells in space conditions. This experiment was selected for the International Microgravity Laboratory 1 (IML-1) mission.

Tixador, R.↗
NASA NTRS1992

Unsteady separation experiments on 2-D airfoils, 3-D wings, and model helicopter rotors

Information on unsteady separation and dynamic stall is being obtained from two experimental programs that have been underway at United Technologies Research Center since 1984. The first program is designed to obtain detailed surface pressure and boundary layer condition information during high amplitude pitching oscillations of a large (17.3 in. chord) model wing in a wind tunnel. The second program involves the construction and testing of a pressure-instrumented model helicopter rotor. This presentation describes some of the results of these experiments, and in particular compares the detailed dynamic stall inception information obtained from the oscillating wing with the unsteady separation and reverse flow results measured on the retreating blade side of the model rotor during wind tunnel testing.

Lorber, Peter F.↗
NASA NTRS2013

Comparison of Hyperthermal Ground Laboratory Atomic Oxygen Erosion Yields With Those in Low Earth Orbit

The atomic oxygen erosion yields of 26 materials (all polymers except for pyrolytic graphite) were measured in two directed hyperthermal radio frequency (RF) plasma ashers operating at 30 or 35 kHz with air. The hyperthermal asher results were compared with thermal energy asher results and low Earth orbital (LEO) results from the Materials International Space Station Experiment 2 and 7 (MISSE 2 and 7) flight experiments. The hyperthermal testing was conducted to a significant portion of the atomic oxygen fluence similar polymers were exposed to during the MISSE 2 and 7 missions. Comparison of the hyperthermal asher prediction of LEO erosion yields with thermal energy asher erosion yields indicates that except for the fluorocarbon polymers of PTFE and FEP, the hyperthermal energy ashers are a much more reliable predictor of LEO erosion yield than thermal energy asher testing, by a factor of four.

Flight tests↗
NASA NTRS1974

Report of the Plasma Physics and Environmental Perturbation Laboratory (PPEPL) working groups. Volume 2: Wave experiments working group

The area of wave experiments for the PPEPL is considered in broad terms. It was found that most experiments in this area can be classified typically by a few generalized experiments. These experiment possibilities are discussed in terms of advantages, disadvantages, and probable areas for future investigation. It was concluded that the areas where wave experiments have the most promise are wave sources, wave propagation, and nonlinear interactions and should be implemented in that order. It was recommended that the PPEPL facility remain sufficiently flexible to handle new ideas as they appear, and a continuing effort should be made to solicit new ideas and approaches. It was also felt that detailed investigations should begin as soon as possible in the areas of antennas, both conventional and particle types, and wave-particle interaction experiments. For Vol. 1, see N74-28169; for Vol. 3, see N74-28171.

Source record↗
NASA NTRS1974

Surface electrical properties experiment. Part 2: Theory of radio-frequency interferometry in geophysical subsurface probing

The radiation fields due to a horizontal electric dipole laid on the surface of a stratified medium were calculated using a geometrical optics approximation, a modal approach, and direct numerical integration. The solutions were obtained from the reflection coefficient formulation and written in integral forms. The calculated interference patterns are compared in terms of the usefulness of the methods used to obtain them. Scattering effects are also discussed and all numerical results for anisotropic and isotropic cases are presented.

Kong, J. A.↗
NASA NTRS1974

Data for NASA's AVE 2 pilot experiment. Part 1: 25-mb sounding data and synoptic charts

Tabulated rawinsonde data at 25-mb intervals from surface to 25 mb is presented for the 54 stations participating in the Atmospheric Variability Experiment 11 pilot experiment which began at 12 GMT on May 11, 1974, and ended at 12 GMT on May 12, 1974. Soundings were made at 3 hour intervals. A brief discussion is included on methods of processing and data accuracy, and synoptic charts prepared from the the data are presented. The area covered by the sounding stations is the eastern United States, east of approximately 105 deg west longitude.

Scoggins, J. R.↗
NASA NTRS1974

Reduction and error analysis of the AVE 2 pilot experiment data

The reduction techniques used to process data from the pilot experiment of the second NASA atmospheric variability experiment (AVE IIP), which was conducted during a 24 hour period beginning at 1200 GMT on May 11, 1974, and ending at 1200 GMT on May 12, 1974 are described. Each step of the data handling process is described through the presentation of computer flow charts, programs, equations, and narrative. An error analysis of the final output is presented, and results of the AVE IIP reduction process are compared with results from the National Weather Service. The AVE IIP sounding data contain more detail than National Weather Service data, but the two data sets may be used together without difficulty.

Fuelberg, H. E.↗
NASA NTRS1982

Special Report on the Data Collection Programs for the Ground Based Nitrogen Washout Experiment. Volume 2 - Detailed Program Descriptions, Listings, Examples and Hardware Specifications

Personal data input, decompression data, nitrogen washout, nitrogen data, and update computer programs are described. Input data and formats; program output, reports, and data; program flowcharts; program listings; sample runs with input and output pages; hardware operation; and engineering data are provided.

Source record↗
NASA NTRS1983

Analysis of unswept and swept wing chordwise pressure data from an oscillating NACA 0012 airfoil experiment. Volume 2: Data report

The analysis of the chordwise load distribution and its sensitivity to the various system parameters represents the next phase of the overall study and is the subject of the present two volume report. The present volume is a compilation of all of the time history response data obtained during the test program previously described. The data have been tabulated in the form of Fourier coefficients for reasons of compactness and for ease by the user to reproduce the unsteady component of the individual pressures and the complete (unsteady plus steady state components) integrated load results. This data volume contains the individual pressure response time histories along the chord followed by the corresponding integrated load results. A further description of these data tables can be found in the text that follows.

St.hilaire, A. O.↗
NASA NTRS1984

Evidence for material between Saturn's A and F rings from the Voyager 2 photopolarimeter experiment

The region in the Saturn system between the F ring and the outer edge of the A ring is an area that appears, in images from the imaging experiment, to be virtually devoid of material except for three small satellites. Near the orbit of 1980S28, Atlas - the innermost satellite - the Voyager Photopolarimeter Stellar Occultation data show a discontinuity in count rate which marks a boundary between the tenuous material near the outer edge of the A ring and the orbit of Atlas. The data pertaining to this region have been examined with the aid of statistics and models generated from other similar ring structures. It is concluded that the discontinuity is real, implying the existence of tenuous material of normal optical depth of 0.01 to 0.006 in this region.

Graps, A. L.↗
NASA NTRS1993

Flow interaction experiment. Volume 2: Aerothermal modeling, phase 2

An experimental and computational study is reported for the flow of a turbulent jet discharging into a rectangular enclosure. The experimental configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets are investigated to provide a better understanding of the flow field in an annular combustor. A laser Doppler velocimeter is used to measure mean velocity and Reynolds stress components. Major features of the flow field include recirculation, primary and annular jet interaction, and high turbulence. A significant result from this study is the effect the primary jets have on the flow field. The primary jets are seen to create statistically larger recirculation zones and higher turbulence levels. In addition, a technique called marker nephelometry is used to provide mean concentration values in the model combustor. Computations are performed using three levels of turbulence closures, namely k-epsilon model, algebraic second moment (ASM), and differential second moment (DSM) closure. Two different numerical schemes are applied. One is the lower-order power-law differencing scheme (PLDS) and the other is the higher-order flux-spline differencing scheme (FSDS). A comparison is made of the performance of these schemes. The numerical results are compared with experimental data. For the cases considered in this study, the FSDS is more accurate than the PLDS. For a prescribed accuracy, the flux-spline scheme requires a far fewer number of grid points. Thus, it has the potential for providing a numerical error-free solution, especially for three-dimensional flows, without requiring an excessively fine grid. Although qualitatively good comparison with data was obtained, the deficiencies regarding the modeled dissipation rate (epsilon) equation, pressure-strain correlation model, and the inlet epsilon profile and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems.

Nikjooy, M.↗