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At least 1,567 records · Page 87
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Dynamic environments for space shuttle payloads

Payload bay dynamic data from the first two space shuttle flights are summarized and evaluated. Development of dynamic environment design and test criteria for shuttle payloads from measured flight data is discussed. Factors that must be considered are flight to flight variations, spatial variations, temporal variations, measurement bias errors and the degree of confidence desired that a predicted environment will not be exceeded in flight. Summary and conclusion reports will be published after STS-4 and at appropriate intervals thereafter. The nature of these future reports and their impact on the user community is discussed.

Kern, D. L.↗
NASA NTRS1982

An equation for bolt clampup relaxation in transient environments

An equation for bolt clampup relaxation for transient temperature-moisture (T-M) conditions was derived starting with a relaxation equation for steady-state conditions, and then using an incremental time approach that exploits the superposition principle for linear viscoelasticity. The resulting equation uses the initial T-M condition (at the time of clamping), the T-M history after clamping, and elastic clampup coefficients for temperature and moisture changes. For a given material and joint configuration, the clampup coefficients are constants that can be calculated by elastic analyses. The clampup equation was used to calculate the changes in clampup occurring in a T300/5208 graphite/epoxy joint exposed to a one-year history of temperature and moisture. Two cases were considered: one was a dry joint exposed to a relatively humid environment and the other was a nearly saturated joint exposed to an arid environment.

Shivakumar, K. N.↗
NASA NTRS1981

The unusual dynamical environment of Phobos and Deimos

A three-dimensional numerical model is used to study the dynamical environment of Phobos and Deimos. Surface gravity, escape speeds, and ejecta impact contours are calculated both for the satellites at their present orbit distances, and for orbit distances they may have had in the past. Impact loci for Stickney ejecta are also calculated and compared with the observed groove locations in order to evaluate a possible secondary-impact origin for the grooves on Phobos. Attention is also given to the possible influence of the dynamical environment on shaping the satellites' surfaces.

Davis, D. R.↗
NASA NTRS1982

Effect of physical training in cool and hot environments on +Gz acceleration tolerance in women

Acceleration tolerance, plasma volume, and maximal oxygen uptake were measured in 15 healthy women before and after submaximal isotonic exercise training periods in cool and hot environments. The women were divided on the basis of age, maximal oxygen uptake, and +Gz tolerance into three groups: a group that exercised in heat (40.6 C), a group that exercised at a lower temperature (18.7 C), and a sedentary control group that functioned in the cool environment. There was no significant change in the +Gz tolerance in any group after training, and terminal heart rates were similar within each group. It is concluded that induction of moderate acclimation responses without increases in sweat rate or resting plasma volume has no influence on +Gz acceleration tolerance in women.

Brock, P. J.↗
NASA NTRS1982

Worst case earth charging environment

The Applications Technology Satellite-6 (ATS-6) geosynchronous satellite charged up to -2200 V in sunlight on day 178, 1974. This event, being the highest known spacecraft charging event in sunlight, is used to estimate a worst case geosynchronous plasma environment for predicting the spacecraft potential in eclipse. The advantage of using this sunlight spectrum as opposed to an eclipse case is that the ion and electron fluxes to the detectors are shifted only slightly due to the spacecraft potential. After correcting the available data for satellite potential and missing data above 81 KeV, it is found that the plasma can be characterized by a single Maxwellian approximation having an electron density of 1.22/cu cm, electron temperature of 16 KeV, hydrogen ion density of 0.24/cu cm, and hydrogen ion temperature of 29 KeV. In eclipse the spacecraft would have charged up to -28 kV, the highest estimated potential to date in the earth's plasma environment.

Deutsch, M.-J. C.↗
NASA NTRS1983

An Assessment of Potential Detectors to Monitor the Man-made Orbital Debris Environment

Observations using NORAD radar showed that man made debris exceeds the natural environment for large objects. For short times (a few days to a few weeks) after solid rocket motor (SRM) firings in LEO, man made debris in the microparticle size range also appears to exceed the meteoroid environment. The properties of the debris population between these size regimes is currently unknown as there has been no detector system able to perform the required observations. The alternatives for obtaining data on this currently unobserved segment of the population are assessed.

Reynolds, R. C.↗
NASA NTRS1983

Use of the VAS for analysis of a prethunderstorm environment

The information content of the VAS radiances can be converted to meteorological parameters useful for analyzing a severe weather environment. The method by which the VAS variances are converted to vertical profiles of temperature, dewpoints, and equivalent potential temperature involves a basic regression technique using the most local radiosonde data available for establishing a correlation matrix. The results indicate that mesoscale features apparent within images of the radiances can be converted to usable temperature and moisture fields using regression when surface temperature and dewpoint observations are included within the total data base. In addition, results indicate that surface data are very important for better defining lower tropospheric structure that the VAS radiances alone cannot properly resolve. Analyses of these retrievals distinctly show mesoscale structure in the temperature and moisture fields derived with VAS radiances collected every 3 hours, and 0000 GMT. The retrievals capture the moisture structure. More important, convective instability is clearly detected immediately before the onset of convection. The results indicate that the VAS is capable of providing valuable mesoscale information suitable for analyzing a preconvective environment that is generally clear.

Uccellini, L. W.↗
NASA NTRS1983

Aerothermal environment in control surface gaps in hypersonic flow: An overview

Experimental and analytical research to develop an understanding of the fluid and thermal environment in control surface gaps such as the spanwise gap of the wing elevon and chordwise gap of a split elevon configuration typical of the Space Shuttle are summarized. Although the experimental and analytical studies were initiated too late to significantly impact the Shuttle design they do provide a fundamental understanding of the basic fluid/thermal environment in control surface gaps and help to establish a firm data base for vehicle design.

Wieting, A. R.↗
NASA NTRS1983

Loads environment for payload/cargo integration

Space Shuttle users are required to design their payload to the Shuttle loads environment. This loads environment covers mission phases from prelaunch to landing. Transient response loads analyses are required for lift-off and landing events. Other mission events are analyzed statically because they result in payload loads that either change slowly or are lower than lift-off and landing loads. Response data from flight instrumentation located on the orbiter and payloads have been compared to preflight design conditions and to nominal predictions. The results have verified that the design loads envelop flight responses.

Frederick, D. H.↗
NASA NTRS1983

Vibration and acoustic environments for payload/cargo integration

Shuttle orbiter launch vibration and acoustic environments for cargo bay/payload interfaces are predicted. Data acquired during Shuttle flight tests are compared with the preflight estimates. Vibration response data for payload attachment locations are presented, along with acoustic data in the form of noise-level spectra measured at various locations in the cargo bay and space averages of the noise levels. It is shown that the payload-bay vibration and acoustic environments are generally less severe than predicted.

Hill, R. E.↗
NASA NTRS1983

The electromagnetic environment for the Space Shuttle orbiter

The electromagnetic environment of the Shuttle orbiter is discussed with respect to the electromagnetic compatibility of the orbiter and its cargo. Effects on payloads of the orbiter's Ku-band antenna are considered, along with the effects of unintentional emissions in the cargo bay, the magnetic fields produced by the orbiter and various payloads, lightning-produced magnetic fields, and noise and transients in the AC and DC power buses. Special EMI testing is described that was carried out to substantiate the orbiter's electromagnetic compatibility. It is concluded that the orbiter presents a very benign electromagnetic environment for cargo except for payloads or experiments that use very sensitive receivers or instruments that can measure low magnetic or electric fields.

Giffin, B. L.↗
NASA NTRS1981

Stability of magnetically suspended optics in a vibration environment

The improving resolution capabilities of large spaceborne optical experiments are placing ever-increasing demands on platform stability in a vibration environment. The present paper discusses the principles of magnetic suspension systems as a promising alternative to conventional methods. The disadvantages of various conventional pointing mount geometrics are discussed, including the CG-mount approach and end-mount pointing, and advantages of a system whereby the payload has a high degree of isolation from the carrier in translation are pointed out. The Annular Suspension and Pointing System Vernier System is then presented as a hardware realization of a complete magnetic suspension system consisting of six magnetic bearing assemblies controlling six degrees of freedom of payload motion in a standardized end-mount configuration. A model of a simplified two-degrees-of-freedom isolation and pointing unit is considered and the transfer function from carrier translation to payload pointing is derived. The function is evaluated for several degenerate cases corresponding to conventional mounting techniques and magnetic suspension. Analytical performance predictions show a stability of better than 0.01 arcsec for a wide range of payloads in the worst-case shuttle disturbance environment.

Hamilton, B. J.↗
NASA NTRS1983

Aerothermal environment in control surface gaps in hypersonic flow - An overview

Experimental and analytical research by the NASA Langley Research Center to develop an understanding of the fluid and thermal environment in control surface gaps such as the spanwise gap of the wing elevon and chordwise gap of a split elevon configuration typical of the Space Shuttle are summarized. Although the experimental and analytical studies were initiated too late to significantly impact the basic Shuttle design they do provide a fundamental understanding of the basic fluid/thermal environment in control surface gaps and help to establish a firm data base for future vehicle design.

Wieting, A. R.↗
NASA NTRS1983

Materials processing in the reduced-gravity environment of space

Studies of the effects of gravitation on the behavior of fluids and the shapes of materials for the years 1977-1982 are reviewed, with a focus on ground-based research which complements and gives direction to experimentation in the reduced-gravity environment of space. Fluid-behavior topics discussed include crystal growth from melts and from vapor, dendritic solidification and casting, multiphase alloy solidification, electrophoresis, convection behavior, and special heat-flow considerations characteristic of the space environment. With regard to solids, such subjects as containerless positioning technology and its applications (in glass preparation, liquid drop and shell studies, nucleation experiments, and measurements of fundamental properties of molten reactants), liquid floating zones, solid self-deformation, and sedimentation and buoyancy effects are considered and illustrated.

Carruthers, J. R.↗
NASA NTRS1983

Calculation of Shuttle Base Heating Environments and Comparison with Flight Data

The techniques, analytical tools, and experimental programs used initially to generate and later to improve and validate the Shuttle base heating design environments are discussed. In general, the measured base heating environments for STS-1 through STS-5 were in good agreement with the preflight predictions. However, some changes were made in the methodology after reviewing the flight data. The flight data is described, preflight predictions are compared with the flight data, and improvements in the prediction methodology based on the data are discussed.

Greenwood, T. F.↗
NASA NTRS1984

The effects of the space environment on damping materials and damping designs on flexible structures

The effects of space environments on damping materials and damping designs on flexible structures were investigated. The following items were examined: damping of flexible spacecraft appendages; composite loss factor (n sub s) vs. time in high vacuum for damped test beams and damping of flexible structures. The STEP experiments show inherent damping of flexible structures in space effective possible damping design configurations for space structures, effects of passively damped components on the system loss factor of flexible structures and the effect of space environment on properties of damping materials.

Kluesener, M. F.↗
NASA NTRS1983

Acoustic environments for JPL shuttle payloads based on early flight data

Shuttle payload acoustic environmental predictions for the Jet Propulsion Laboratory's Galileo and Wide Field/Planetary Camera projects have been developed from STS-2 and STS-3 flight data. This evaluation of actual STS flight data resulted in reduced predicted environments for the JPL shuttle payloads. Shuttle payload mean acoustic levels were enveloped. Uncertainty factors were added to the mean envelope to provide confidence in the predicted environment.

Oconnell, M. R.↗
NASA NTRS1984

Space environment effects on fiber optics systems

The performance survivability of hardened fiber optic data link design for application in future spacecraft systems was assessed. The effects of space environmental conditions on link performance was analyzed. The integration and operation of new fiber optic link components exhibiting increased hardening to radiation environments is emphasized. The opportunity to expose operational fiber optic data links to an actual space environment for 6 months or longer and to retrieve the data links for analysis are discussed. Reliable design criteria for future spacecraft application, relative to the long term low dose space radiation effects as a function of temperature are outlined.

Taylor, E. W.↗