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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 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Orbital debris policy issues: Battelle involvement and some personal observations

The possible hazards presented by orbital debris have been a matter of concern since the early 1960s. The area of initial concern was the potential hazard of the Earth from reentering debris. In the very early days of the space program, it was believed that only specially protected objects would survive reentry. Subsequent events showed this to be incorrect. The recognition of the potential hazard of orbital debris to orbiting objects did not occur until the late 1970s. Concern over this potential hazard has increased, and has also given rise to a number of policy issues. These issues are, at present, largely unresolved.

Edgecombe, D. S.↗
NASA NTRS1985

Seven-wavelength pyrometer for determining surface temperature of ablation materials

Results which were achieved by a seven-wavelength pyrometer last year are reported in this paper. These studies are directed toward the development of a method for determining the real surface temperature of thermal protection materials and for evaluating its emittance under varieties of reentry environment. A description of the data processing method and apparatus is also included.

Yi, H.↗
NASA NTRS1985

A 3-dimensional Navier-Stokes-Euler code for blunt-body flow computations

The shock-layer flowfield is obtained with or without viscous and heat-conducting dissipations from the conservative laws of fluid dynamics equations using a shock-fitting implicity finite-difference technique. The governing equations are cast in curvilinear-orthogonal coordinates and transformed to the domain between the shock and the body. Another set of equations is used for the singular coordinate axis, which, together with a cone generator away from the stagnation point, encloses the computation domain. A time-dependent alternating direction implicit factorization technique is applied to integrate the equations with local-time increment until a steady solution is reached. The shock location is updated after the flowfield computation, but the wall conditions are implemented into the implicit procedure. Innovative procedures are introduced to define the initial flowfield, to treat both perfect and equilibrium gases, to advance the solution on a coarse-to-fine grid sequence, and to start viscous flow computations from their corresponding inviscid solutions. The results are obtained from a grid no greater than 28 by 18 by 7 and converged within 300 integration steps. They are of sufficient accuracy to start parabolized Navier-Stokes or Euler calculations beyond the nose region, to compare with flight and wind-tunnel data, and to evaluate conceptual designs of reentry spacecraft.

Li, C. P.↗
NASA NTRS1985

Computer simulation studies in fluid and calcium regulation and orthostatic intolerance

The systems analysis approach to physiological research uses mathematical models and computer simulation. Major areas of concern during prolonged space flight discussed include fluid and blood volume regulation; cardiovascular response during shuttle reentry; countermeasures for orthostatic intolerance; and calcium regulation and bone atrophy. Potential contributions of physiologic math models to future flight experiments are examined.

Source record↗
NASA NTRS1985

Simulation of a G-tolerance curve using the pulsatile cardiovascular model

A computer simulation study, performed to assess the ability of the cardiovascular model to reproduce the G tolerance curve (G level versus tolerance time) is reported. A composite strength duration curve derived from experimental data obtained in human centrifugation studies was used for comparison. The effects of abolishing automomic control and of blood volume loss on G tolerance were also simulated. The results provide additional validation of the model. The need for the presence of autonomic reflexes even at low levels of G is pointed out. The low margin of safety with a loss of blood volume indicated by the simulation results underscores the necessity for protective measures during Shuttle reentry.

Solomon, M.↗
NASA NTRS1984

Numerical computation of space shuttle orbiter flow field

The complete inviscid viscous real gas flow around the Space Shuttle Orbiter was computed. Real gas effects are important in predicting the reentry environment around the Orbiter because the high temperatures within the shock layer cause the air to dissociate and ionize, thus invalidating the perfect gas assumption. It is shown that real gas effects has a significant influence on the Orbiter aerodynamics. The approach utilizes a time dependent Navier-Stokes code to compute the subsonic nose portion of the flow field. This nose solution provides the initial conditions for the parabolized Navier-Stokes (PNS) code.

Tannehill, J. C.↗
NASA NTRS1985

Procedure for estimating orbital debris risks

A procedure for estimating the potential orbital debris risk to the world's populace from payloads or spent stages left in orbit on future missions is presented. This approach provides a consistent, but simple, procedure to assess the risk due to random reentry with an adequate accuracy level for making programmatic decisions on planned low Earth orbit missions.

Crafts, J. L.↗
NASA NTRS1980

Results of tests on a specimen of the SRB aft skirt heat shield curtain in the MSFC LRLF

A full scale segment of the actual Solid Rocket Booster aft skirt heat shield curtain was tested in the Large Radiant Lamp Facility (LRLF) at Marshall Space Flight Center. The curtain was mounted in the horizontal position in the same manner as it is to be mounted on the SRB. A shaker rig was designed and used to provide a motion of the curtain, simulating that to be caused in flight by vehicle acoustics. Thermocouples were used to monitor curtain materials temperatures. Both ascent and reentry heat loads were applied to the test specimen. All aspects of the test setup performed as expected, and the test was declared successful.

Dean, W. G.↗
NASA NTRS1982

Results of tests of MTA-2 TPS on the SRB hold-down bolt blast container

The four solid rocket booster (SRB) hold-down posts are fastened to the mobile launch platform (MLP) with four large nuts. At liftoff the nuts are split with explosive changes to release the SRB/Shuttle. A blast container is placed over the nuts to protect the vehicle from flying debris. The blast container is a reusable part and has to be protected from aerodynamic heating during flight. The thermal protection system (TPS) used to protect these blast containers is cork. Fitting the flat cork sheet to this hemispherical shaped blast container is both time consuming and expensive. Another problem is removing the charred cork and epoxy glue from the blast containers. Replacements of this cork with another TPS material such as MTA-2 was examined. Heating rates along the centerline of the forward facing areas of the blast container were determined. The feasibility of using 1/2 in. MTA-2 on the SRB blast containers for protection from ascent, plume impingement and reentry heating is demonstrated.

Dean, W. G.↗
NASA NTRS1979

SRB thermal protection systems materials test results in an arc-heated nitrogen environment

The external surface of the Solid Rocket Booster (SRB) will experience imposed thermal and shear environments due to aerodynamic heating and radiation heating during launch, staging and reentry. This report is concerned with the performance of the various TPS materials during the staging maneuver. During staging, the wash from the Space Shuttle Main Engine (SSME) exhust plumes impose severe, short duration, thermal environments on the SRB. Five different SRB TPS materials were tested in the 1 MW Arc Plasma Generator (APG) facility. The maximum simulated heating rate obtained in the APG facility was 248 Btu/sq ft./sec, however, the test duration was such that the total heat was more than simulated. Similarly, some local high shear stress levels of 0.04 psia were not simulated. Most of the SSME plume impingement area on the SRB experiences shear stress levels of 0.02 psia and lower. The shear stress levels on the test specimens were between 0.021 and 0.008 psia. The SSME plume stagnation conditions were also simulated.

Wojciechowski, C. J.↗
NASA NTRS1984

Pioneer to Venus - The multiprobe and orbiter missions

The missions of the Pioneer multiprobe and orbiter spacecraft to Venus are surveyed and illustrated with drawings, photographs, maps, and diagrams. The general characteristics of Venus and the pre-Pioneer missions are reviewed; the developmental history of the Pioneer project is traced; the spacecraft and their orbits and deployment are described; and the scientific findings on the planet surface, atmosphere, and ionosphere are summarized. The experiments planned for the extended mission of the orbiter (through reentry in 1992) are briefly characterized, includidng solar-wind-interaction studies, comet detection, ionosphere and aeronomy investigations, global lightning survey, optical observations, gamma-ray-burst detection, radar mapping, gravity measurements, and observations of Halley's Comet during February, 1986.

Craig, R. A.↗
NASA NTRS1984

A correlation of scale model and flight aeroacoustic data for the Space Shuttle vehicle

A correlation is presented between aeroacoustic data acquired in the early Space Shuttle flights and in the various scale model tests from which the Shuttle vibroacoustic design environments were derived. These are the external acoustic data on the vehicle elements at liftoff, during the transonic and maximum dynamic pressure period of ascent flight, and during spent SRB reentry. The maximum external acoustic environment on the Shuttle elements in a given 1/3-octave frequency band comes from one of these critical flight regimes. The data correlation is seen to be good, testifying to adequate scale model measurement and test techniques. Some of the more salient features of the scale model test programs are described.

Dougherty, N. S.↗
NASA NTRS1985

Application of axisymmetric analogue for calculating heating in three-dimensional flows

A rapid, approximate method has been developed for calculating the heating rates on three-dimensional vehicles such as the Space Shuttle Orbiter and other advanced reentry configurations. The method is based on the axisymmetric analogue for three-dimensional boundary layers. It uses information obtained from a three-dimensional inviscid flowfield solution, such as HALIS, to calculate inviscid surface streamlines along which approximate heating rates are calculated independent of what happens along other streamlines. Three-dimensional effects are included through the metric coefficient that describes the divergence or convergence of streamlines. Boundary-layer edge properties are obtained from the inviscid flowfield solution by interpolating in the inviscid flowfield at a distance equal to the boundary-layer thickness away from the wall. This accounts, approximately, for the variable boundary-layer edge entropy. Using this method, heating calculations can be made along a typical streamline in a few seconds. This method has been used to accurately predict heating rates for simple shapes such as a spherically blunted cone and more complex shapes such as the Shuttle Orbiter for a variety of wind-tunnel and flight conditions. A unique feature of the method is its ability to accurately predict heating rates on the Shuttle Orbiter wing.

Hamilton, H. H.↗
NASA NTRS1985

Analytical modeling of circuit aerodynamics in the new NASA Lewis Altitude Wind Tunnel

Rehabilitation and extention of the capability of the altitude wind tunnel (AWT) was analyzed. The analytical modelling program involves the use of advanced axisymmetric and three dimensional viscous analyses to compute the flow through the various AWT components. Results for the analytical modelling of the high speed leg aerodynamics are presented; these include: an evaluation of the flow quality at the entrance to the test section, an investigation of the effects of test section bleed for different model blockages, and an examination of three dimensional effects in the diffuser due to reentry flow and due to the change in cross sectional shape of the exhaust scoop.

Towne, C. E.↗
NASA NTRS1983

Simulation of cardiovascular response to acceleration stress following weightless exposure

Physiological adjustments taking place during space flight tend to reduce the tolerance of the crew to headward (+Gz) acceleration experienced during the reentry phase of the flight. This reduced tolerance to acceleration stress apparently arises from an adaptation to the microgravity environment of space, including a decrease in the total circulating blood volume. Countermeasures such as anti-g garments have long been known to improve the tolerance to headward g-force, but their effectiveness in space flight has not been fully evaluated. The simulation study presented in this paper is concerned with the response of the cardiovascular system to g-stress following cardiovascular deconditioning, resulting from exposure to weightlessness, or any of its ground-based experimental analogs. The results serve to demonstrate the utility of mathematical modeling and computer simulation for studying the causes of orthostatic intolerance and the remedial measures to lessen it.

Srinivasan, R.↗
NASA NTRS1985

Improving the breed - Shuttle development

An evaluation is made of design improvements that have been made to the Space Shuttle System, and the performance gains obtained; the most important of these stem from efforts to refine procedures for rendezvous with stricken satellites, in order to repair them. Ascent performance has been improved through Space Shuttle Main Engine thrust improvements and external tank weight reductions. On-orbit living convenience has been enhanced by the addition of small sleeping compartments and a galley. Greater flexibility has been obtained for reentry and landing maneuvers. Attention is given to problems which continue to be posed by the thermal protection tiles.

Brand, V.↗
NASA NTRS1985

Transitional, hypervelocity aerodynamic simulation and scaling in light of recent flight data

Simulation and scaling procedures applicable to maneuvering vehicles for the transitional hypervelocity flow regime are discussed with reference to certain discrepancies between lifting reentry flight data and predicted results. Low-density hypervelocity wind-tunnel data are compared with CFD and in-flight measurements. A general correlation parameter for transitional flow is produced by incorporation of a new geometric term into a form of Reynolds number. It is shown that normalized drag coefficients of a variety of shapes, including spheres, blunt-nosed cones, lifting bodies, and an STS orbiter are correlated by the parameter. A provisional bridging formula for the coefficients is presented.

Potter, J. L.↗
NASA NTRS1985

Monte Carlo simulations in support of the Shuttle upper atmospheric mass spectrometer experiment

This paper presents the results of calculations obtained with a Direct Simulation Monte Carlo (DSMC) method that describes both the external flow about the nose region of the Shuttle Orbiter and the internal flow in an inlet tube that provides the initial path between the shock-processed gases and a mass spectrometer mounted inside the Orbiter. A dedicated, three-dimensional version of the DSMC was developed during this study for the internal flow simulation along with the procedure for interfacing the external and internal flows. The calculations span the 140 to 95 km altitude range, which includes most of the hypersonic transitional flow encountered during reentry. All calculations were for a multicomponent gas mixture consisting of five chemical species while simulating the effects of transitional, rotational, vibrational, and chemical nonequilibrium. The results of the calculations show that within the entry region of the inlet tube where the gas has equilibrated with the sidewall tube temperature, the pressure is substantially less than the pressure at the external surface. This pressure correction for the entry region is significant for all conditions investigated and increases with altitude. The results highlight the structure of both the external and internal flow. Results of parametric studies show the sensitivity of the equilibrated inlet sidewall pressure to mass flow rates, gas-surface reflection model, tube side-wall temperature variations, and surface recombinations.

Moss, J. N.↗