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At least 109 records · Page 6

Environmental Effects of Space Shuttle Solid Rocket Motor Exhaust Plumes

The deposition of NOx and HCl in the stratosphere from the space shuttle solid rocket motors (SRM) and exhaust plume is discussed. A detailed comparison between stratospheric deposition rates using the baseline SRM propellant and an alternate propellant, which replaces ammonium perchlorate by ammonium nitrate, shows the total NOx deposition rate to be approximately the same for each propellant. For both propellants the ratio of the deposition rates of NOx to total chlorine-containing species is negligibly small. Rocket exhaust ground cloud transport processes in the troposphere are also examined. A brief critique of the multilayer diffusion models (presently used for predicting pollutant deposition in the troposphere) is presented, and some detailed cloud rise calculations are compared with data for Titan 3C launches. The results show that, when launch time meteorological data are used as input, the model can reasonably predict measured cloud stabilization heights.

Hwang, B.↗

Effect of the Shuttle contaminant environment on a sensitive infrared telescope

A sensitive IR telescope on the Space Shuttle Orbiter will be limited in its performance by fluctuations in the IR radiation from the natural environment and the contaminant atmosphere. Models of the Orbiter's contaminant atmosphere were used to predict its spectral radiance from 3 to 300 microns. At 350 km, statistical fluctuations in the radiation from a water vapor column, and a noise equivalent power were measured. This noise is somewhat smaller than the expected contribution from zodiacal light from 5 to 30 microns. The column density of all IR emitting molecules can be kept low only if restrictions on rocket firings and liquid vents are maintained. The relatively low frequency of particle sightings from Skylab, coupled with improvements in Orbiter venting techniques, indicate that sightings of particles 2 microns and larger in radius will not seriously hamper telescope performance provided that liquid vents and rocket firings are properly restricted.

Simpson, J. P.↗

Space Shuttle Plume Simulation Effect on Aerodynamics

Technology for simulating plumes in wind tunnel tests was not adequate to provide the required confidence in test data where plume induced aerodynamic effects might be significant. A broad research program was undertaken to correct the deficiency. Four tasks within the program are reported. Three of these tasks involve conducting experiments, related to three different aspects of the plume simulation problem: (1) base pressures; (2) lateral jet pressures; and (3) plume parameters. The fourth task involves collecting all of the base pressure test data generated during the program. Base pressures were measured on a classic cone ogive cylinder body as affected by the coaxial, high temperature exhaust plumes of a variety of solid propellant rockets. Valid data were obtained at supersonic freestream conditions but not at transonic. Pressure data related to lateral (separation) jets at M infinity = 4.5, for multiple clustered nozzles canted to the freestream and operating at high dynamic pressure ratios. All program goals were met although the model hardware was found to be large relative to the wind tunnel size so that operation was limited for some nozzle configurations.

Hair, L. M.↗

Environmental effects on space shuttle reusable surface insulation coated with reaction cured glass

Sample titles of the space shuttle reusable surface insulation was subjected alternately to simulated mission heating and either real or simulated environmental exposure for up to 34 cycles. The coating cracked as a result of exposure to high temperature and moisture conditions, and insulation with cracked coatings absorbed significant quantities of water in the launch-pad environment. Cracking was a complex function of time, temperature, and moisture exposure. Cracked coatings remained adherent to the insulation for up to 24 cycles past initial cracking.

Ransone, P. O.↗

Effects of space shuttle launches STS-1 through STS-9 on terrestrial vegetation of John F. Kennedy Space Center, Florida

Space Shuttle launches produce a cloud containing hydrochloric acid (HCl), aluminum oxide (Al203), and other substances. Acidities of less than 0.5 pH have been measured routinely in association with the launch cloud. In an area of about 22 ha regularly exposed to the exhaust cloud during most Shuttle launches, acute vegetation damage has resulted from the first nine Shuttle launches. Changes include loss of sensitive species, loss of plant community structure, reduction in total cover, and replacement of some species by weedy invaders. Community level changes define a retrogressive sequence. One-time impacts to strand and dune vegetation occurred after launches of STS-8 and STS-9. Acute vegetation damage occurred especially to sensitive species. Within six months, however, recovery was nearly complete. Sensitivity of species to the launch cloud was partially predicted by previous laboratory studies. Far-field acidic and dry fallout from the cloud as it rises to stabilization and moves with the prevailing winds causes vegetation spotting. Damage from this deposition is minor; typically at most 1% to 5% of leaf surface area is affected. No plant mortality or community changes have occurred from far-field deposition.

Schmalzer, P. A.↗

Commercialization of Kennedy Space Center Instrumentation Developed to Improve Safety, Reliability, Cost Effectiveness of Space Shuttle Processing, Launch, and Landing

Priorities and achievements of the Kennedy Space Center (KSF) Instrumentation Laboratories in improving operational safety and decreasing processing costs associated with the Shuttle vehicle are addressed. Technologies that have been or are in the process of technology transfer are reviewed, and routes by which commercial concerns can obtain licenses to other KSF Instrumentation Laboratory technologies are discussed.

Helms, William R.↗

STS-9 Shuttle grow - Ram angle effect and absolute intensities

Visible imagery from Space Shuttle mission STS-9 (Spacelab 1) has been analyzed for the ram angle effect and the absolute intensity of glow. The data are compared with earlier measurements and the anomalous high intensities at large ram angles are confirmed. Absolute intensities of the ram glow on the shuttle tile, at 6563 A, are observed to be about 20 times more intense than those measured on the AE-E spacecraft. Implications of these observations for an existing theory of glow involving NO2 are presented.

Swenson, G. R.↗

Life sciences in the Shuttle era

The effect of the Shuttle program on life science research and the life science research community is examined. Responses to a NASA invitation to participate in planning the life sciences program in space are considered. The development of life science space equipment is surveyed.

Deutsch, S.↗

Effect of step and/or gap tile misalignment on shuttle transition

The effect of tile misalignment, simulating both step type and gap type misalignment was determined on transition locations in the plane of symmetry of the shuttle orbiter. Data were obtained in a closed circuit hypersonic tunnel with a 50-in. diameter test section providing a Mach number of 8 over a range of pressure levels from 345,000 N/sq m (50 psi) to 620 million N/sq m (900 psi). The stagnation temperature is sufficient to avoid air liquefaction in the test section.

Bertin, J. J.↗

Multiple dielectric layer effects on the space shuttle orbiter S-band quad antennas

A mathematical tool is developed for evaluation of antenna radiation pattern effects on the shuttle orbiter S band quad antennas. A ray optics approach is used which includes multiple internal reflections with special consideration to reflection from the metallic orbiter skin. Significant depolarization may occur as the angle from the normal increases. The effect of changing tile thickness on the beamwidth of the upper quads versus the lower quads results in a small increase in the lower quad beamwidth compared with the beamwidth in the upper quads. The optimization and evaluation of the S band quads and the computer tool developed may be used to evaluate other shuttle orbiter antennas.

Lindsey, J. F.↗

Determination of effective aerodynamic characteristics for entry of External Tank /Space Shuttle/ debris

The effective aerodynamic characteristics for the debris resulting from the Space Shuttle External Tank (ET) are required for estimating the impact points of the debris. The paper develops a methodology that determines the effective values of the aerodynamic parameters required for performing the less complex three-degree-of-freedom (DOF) debris impact analyses. For all of the debris types, 6-DOF mass property and aerodynamic data are computed. From many 6-DOF trajectory simulations, standard deviation range values are calculated. With 3-DOF trajectory matching, these range values are used to determine the effective ballistic coefficient and the range of lift-to-drag ratios for each of the ET debris types defined.

Bonson, S. P.↗

The effects of flow separation on shuttle dynamics and aeroelastic stability

The effects of flow separation on the dynamic and aeroelastic stability of various shuttle configurations have been investigated. Flow separation is shown to affect the aeroelastic stability of the 747/Orbiter yaw modes, the orbiter dynamic stability and possibly the aeroelastic stability of the wing torsional mode, and to dominate both the dynamic and aeroelastic stability of the launch configuration. Limit cycle oscillations of certain launch configuration modes are the result of sudden flow separation. The limit cycle oscillations threaten the structural integrity in two ways: (1) by outright overstressing of the structure due to large modal deflection, (2) by fatigue due to the continued flexing of the structure. Fatigue is a more significant consideration for the reusable (100 flights) shuttle than it has been for previous space boosters.

Reding, J. P.↗

Effect of Clouds on Shuttle Imaging

This report describes the results of the AMU's task for determining the effect of clouds on optical imaging of the Space Shuttle launch vehicle during its ascent phase from lift-off to Solid Rocket Booster (SRB) Separation. This effort was motivated by Recommendation R3.4-1 from the Columbia Accident Investigation Board Report. The AMU developed a 3-dimensional (3D) model to forecast the probability that at any time from lift-off to SRB separation, at least three of the ascent imaging cameras would have a view of the Shuttle unobstructed by cloud. Because current observational and modeling capabilities do not permit accurate forecasts of cloud morphology and location, the AMU simulated obscuration of the lines-of-sight (LOS) from a network of cameras to the Shuttle by idealized cloud-fields placed randomly within the 3D domain. For each random realization of numerous cloud-field scenarios the number of simultaneous views of the Shuttle was computed from the LOS data between lift-off and SRB separation. The percent of time with 3 simultaneous views was averaged from 100 random realizations of each scenario. Analyses of the percent of time viewable were made to determine its sensitivity to cloud amount, cloud base height, cloud thickness, cloud horizontal dimensions, and an upgrade of the camera network.

Short, David A.↗

In-space technology development: Atomic oxygen and orbital debris effects

Earlier Shuttle flight experiments have shown atomic oxygen within the orbital environment can interact with many materials to produce surface recession and mass loss and combine catalytically with other constituents to generate visible and infrared glows. In addition to these effects, examinations of returned satellite hardware have shown many spacecraft materials are also susceptible to damage from high velocity impacts with orbital space debris. These effects are of particular concern for large, multi-mission spacecraft, such as Space Station and SDI operational satellites, that will operate in low-Earth orbit (LEO) during the late 1990's. Not only must these spacecraft include materials and exterior coatings that are resistant to atomic oxygen surface interactions, but these materials must also provide adequate protection against erosion and pitting that could result from numerous impacts with small particles (less than 100 microns) of orbital space debris. An overview of these concerns is presented, and activities now underway to develop materials and coatings are outlined that will provide adequate atomic protection for future spacecraft. The report also discusses atomic oxygen and orbital debris flight experiments now under development to expand our limited data base, correlate ground-based measurments with flight results, and develop an orbital debris collision warning system for use by future spacecraft.

Visentine, James T.↗

Grooming the Shuttle for cost-effective access to space

An assessment is made of the performance of the Space Shuttle-based Space Transportation System (STS) from the initial flights in 1981 to the present, which has involved the launching of 12 satellites and the retrieval of two. It is expected that the STS will soon be able to schedule 24 routine missions/year, upon the achievement of full operational status for the full fleet of four Space Shuttles and the completion of support facilities at both the Kennedy Space Center and Vandenberg Air Force Base. The prospects for space industrialization efforts based on STS are noted.

Moore, J. W.↗