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Results for “Shock Layer Radiation”

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 NTRS1979

Effects of probe shape change on flow phenomena during Jovian entry

The effects of probe shape change on the flow phenomena around a Jovian entry body is investigated. The initial body shapes considered are: 45-degree sphere cone, 35-degree hyperboloid, and 45-degree ellipsoid. The radiating shock-layer flow is assumed to be axisymmetric, inviscid, and in chemical and local thermodynamic equilibrium. The radiative transfer is calculated with an existing nongray radiation model that accounts for molecular band, atomic line, and continuum transitions. The results indicate that the shock-standoff distance, shock temperature and density, wall pressure distribution and radiative heating to the body are influenced significantly because of the probe shape change. The effect of shape change on radiative heating of the afterbody was considerably larger for the sphere cone and ellipsoid than for the hyperboloid. For the peak heating conditions, the net radiative heating to the body was found to be highest for the ellipsoid

Tiwari, S. N.↗
NASA NTRS1978

Radiative flux penetration through a blown shock layer for Jupiter entry conditions

A study is made of the radiative blockage due to carbonaceous ablation injection for a probe entering the Jupiter atmosphere. This is accomplished by calculating the stagnation-point blockage factors for three entry trajectories that account for variations in probe configuration, atmospheric gas composition, and entry conditions. The radiative blockage within the relatively cool ablation layer is shown to be large and to be primarily dependent upon the absorption of the C2 and C3 species. The C3 absorption is significant, particularly when the new experimental data for C3 spectral absorption properties are used. Also, the stagnation-point radiative blockage factors are shown to correlate well in terms of the no-injection radiative heating rates for various entry conditions.

Moss, J. N.↗
NASA NTRS1975

Finite-rate chemistry effects upon convective and radiative heating of an atmospheric entry vehicle

A mathematical model of the aerothermochemical environment along the stagnation line of a planetary return spacecraft using an ablative thermal protection system was developed and solved for conditions typical of atmospheric entry from planetary missions. The model, implemented as a FORTRAN 4 computer program, was designed to predict viscous, reactive and radiative coupled shock layer structure and the resulting body heating rates. The analysis includes flow field coupling with the ablator surface, binary diffusion, coupled line and continuum radiative and equilibrium or finite rate chemistry effects. The gas model used includes thermodynamic, transport, kinetic and radiative properties of air and ablation product species, including 19 chemical species and 16 chemical reactions. Specifically, the impact of nonequilibrium chemistry effects upon stagnation line shock layer structure and body heating rates was investigated.

Guillermo, P.↗
NASA NTRS1990

Supernovae and supernova remnants at low frequencies

The importance of low-frequency observations of the intrinsic radio emission from supernovae and their remnants is discussed, with special attention given to an example of a peculiarity at low frequencies of the 38-MHz 'flare' observed from Cas A in the mid-1970s. It is suggested that, for explosions from supernovae in a low-density wind, it may be possible to follow the absorption over a large range of shock front radii. Absorption local to the remnants can occur in H II regions created by the supernovae or their progenitors and in the cooling layers of radiative shock fronts, or in the ionized interstellar medium. Observations of emission as well as of absorption are necessary to determine the location of the ionized gas.

Chevalier, Roger A.↗
NASA NTRS1972

Radiative and convective heating during Venus entry.

Determination of the stagnation region heating of probes entering the Venusian atmosphere. Both convective and radiative heat-transfer rates are predicted, and account is taken of the important effects of radiative transport in the vehicle shock layer. A nongray radiative transport model is utilized which parallels a four-band treatment previously developed for air (Page et al., 1969), but includes two additional bands to account for the important CO(4+) molecular band system. Some comparisons are made between results for Venus entry and results for earth entry obtained using a viscous earth entry program.

Page, W. A.↗
NASA NTRS1972

An implicit finite-difference solution to the viscous shock layer, including the effects of radiation and strong blowing

An implicit finite-difference scheme is developed for the fully coupled solution of the viscous, radiating stagnation-streamline equations, including strong blowing. Solutions are presented for both air injection and injection of carbon-phenolic ablation products into air at conditions near the peak radiative heating point in an earth entry trajectory from interplanetary return missions. A detailed radiative-transport code that accounts for the important radiative exchange processes for gaseous mixtures in local thermodynamic and chemical equilibrium is utilized in the study. With minimum number of assumptions for the initially unknown parameters and profile distributions, convergent solutions to the full stagnation-line equations are rapidly obtained by a method of successive approximations. Damping of selected profiles is required to aid convergence of the solutions for massive blowing. It is shown that certain finite-difference approximations to the governing differential equations stabilize and improve the solutions. Detailed comparisons are made with the numerical results of previous investigations. Results of the present study indicate lower radiative heat fluxes at the wall for carbonphenolic ablation than previously predicted.

Garrett, L. B.↗
NASA NTRSDate not supplied

Impact of NASA’s Entry Systems Modeling Project on Planetary Mission Design

Planetary missions continue to grow larger and more complex. Furthermore, the current focus on human exploration of the Moon and Mars, as well as Mars Sample Return(MSR), place increas-ingly stringent requirements on the reliability of the entry, descent, and landing (EDL) system that ensures the safe delivery of payload or crew to their destination. Planetary EDL is an area in which mission designers are critically reliant on modeling and simulation to demonstrate the reliability of the system, as there are no ground facilities that are able to fully test these systems in a flight-relevant environment. NASA’s state-of-the-art modeling and simulation capability must continually evolve to meet the needs of the next generation of planetary EDL. To accomplish this aim, NASA’s Entry Systems Modeling (ESM) Project was formed in 2013and is funded bythe Space Technology Mission Directorate(STMD) and Science Mission Directorate (SMD). ESM is the Agency’s only cross-cutting effort for advancing entry systems modeling and simulation capabilities across a range of technical disciplines and Solar System destinations. ESM is a portfolio project covering a variety of mid-TRL research efforts within four core EDL-related areas of investment: (1) Thermal protection material modeling, (2) Shock layer kinetics and radiation, (3) Aerosciences, and (4) Guidance, navigation, and con-trol. The material modeling group creates detailed material response modelsof thermal protection systems (TPS)from the micro to macro scale, and at the fun-damental and engineering levels. Shock layer kinetics and radiation focuses on radiative heating of space-craft, quantum chemistry and benchmark experiments for validation.Aerosciences is a broad research area that impacts many aspects of entry systems, including parachutes, aerodynamics, and turbulent heating augmentation due to TPS roughness.The guidance, navigation,and control effort under ESM is expanding the capabilities of NASA’s main flight mechanics tool, POST2, for use on high-performance computing architectures and to generalize interoperability with external applications for more detailed end-to-end simula-tion.In addition, several focusedresearch topics have been approvedto augment ESM’s core portfolio. These include efforts for deep post-flight analysis of Mars 2020/MEDLI2 flight data; development ofTPS failure models; improvement of hypersonic wakeflow models; and a recently concluded effort to provide material response models for NuSil-coated PICA heat-shield material. This presentation will discuss each of these investment areas and demonstrate via real mission examples how advances to the state-of-the-art enabled by ESM are directly impacting the missions of today and tomorrow, including InSight, Mars 2020, Mars Sample Return, Orion, and Dragonfly.

Entry Systems Modeling↗
NASA NTRS1973

Nonequilibrium effects on shock-layer radiometry during earth entry.

Radiative enhancement factors for the CN violet and N2(+) first negative band systems caused by nonequilibrium thermochemistry in the shock layer of a blunt-nosed vehicle during earth entry are reported. The results are based on radiometric measurements obtained with the aid of a combustion-driven shock tube. The technique of converting the shock-tube measurements into predictions of the enhancement factors for the blunt-body case is described, showing it to be useful for similar applications of other shock-tube measurements.

Arnold, J. O.↗
NASA NTRS1978

Influence of precursor heating on viscous flow around a Jovian entry body

The influence of changes in precursor region flow properties (resulting from the absorption of radiation from the shock layer) on the entire shock layer flow phenomena is investigated. Axially symmetric case is considered for both the preheating zone (precursor region) and shock layer. The flow in the shock layer is considered to be viscous with chemical equilibrium but radiative nonequilibrium. Realistic thermo-physical and spectral models are employed and results are obtained by implicit finite difference and iterative procedures. The results indicate that precursor heating increases the radiative heating of the body by a maximum of 7.5% for a 116 KM entry conditions.

Tiwari, S. N.↗
NASA NTRS1979

Influence of precursor heating on viscous flow around a Jovian entry body

The influence of changes in precursor region flow properties (resulting from the absorption of radiation from the shock layer) on the entire shock layer flow phenomena was investigated. The axially symmetric case is considered for both the preheating zone (precursor region) and shock layer. The flow in the shock layer is assumed to be viscous with chemical equilibrium but radiative nonequilibrium. Realistic thermophysical and spectral models are employed, and results are obtained by implicit finite difference and iterative procedures. The results indicate that precursor heating increases the radiative heating of the body by a maximum of 7.5 percent for 116 km entry conditions.

Tiwari, S. N.↗