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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Computational equations for radiating and ablating shock layers

The computational equations governing the shock-layer flowfield over a blunt body dominated by radiation and ablation are derived. The flowfield considered is that expected around the vehicles entering the atmosphere of the planet Mars or the earth on return from Mars on a sprint-type manned mission. To determine the appropriate method of approach, the radiative transfer calculations are made first using the existing computer code RASLE (Nicolet et al., 1978), which uses the assumption of equilibrium and a coarse spectral band model for radiative transfer, and the code NONEQ which accounts for thermochemical nonequilibrium and carries out line-by-line calculation of radiation. By comparing the results, it is concluded that a thermochemical nonequilibrium model and a line-by-line spectral model must be used.

Park, Chul↗
NASA NTRS1992

A three-dimensional axisymmetric photochemical flow model of the cometary 'inner' shock layer

Assuming the Newtonian thin layer approximation to describe the structure of the shock layer between the cometary 'ionopause' and the inner shock, a 3D axisymmetric photochemical flow model of this layer is constructed. While sources of ions in this layer are the flow across the inner shock and photoionization of neutrals within it, the sinks are the flow into the flanks and dissociative recombination, the latter being the dominant one. For Halley's comet at the time of the Giotto encounter, the calculated thickness of the layer is very small, typically about 100 km for expected values of the dissociative-recombination coefficient. This is not inconsistent with the observations. The lateral flow speed near the point of encounter (inbound) is about 0.9 km/s, while the sonic line is at an angle of about 50 deg to the sun-comet line. Testing the validity of this model will have to await a cometary rendezvous mission such as the proposed CRAF/Cassini mission.

Damas, M. C.↗
NASA NTRS2005

On Nonequilibrium Radiation in Hydrogen Shock Layers

The influence of thermochemical nonequilibrium in the shock layer over a vehicle entering the atmosphere of an outer planet is examined qualitatively. The state of understanding of the heating environment for the Galileo Probe vehicle is first reviewed. Next, the possible reasons for the high recession in the frustum region and the low recession in the stagnation region are examined. The state of understanding of the nonequilibrium in the hydrogen flow is then examined. For the entry flight in Neptune, the possible influence of nonequilibrium is predicted.

Park, Chul↗
NASA NTRS1991

An approximate viscous shock layer approach to calculating hypersonic flows about blunt-nosed bodies

An approximate axisymmetric method has been developed which can reliably calculate fully viscous hypersonic flows over blunt-nosed bodies. By substituting Maslen's second order pressure expression for the normal momentum equation, a simplified form of the viscous shock layer (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the shock layer without a starting solution for the shock shape. Since the method is fully viscous, the problems associated with coupling a boundary-layer solution with an inviscid-layer solution are avoided. This procedure is significantly faster than the parabolized Navier-Stokes (PNS) or VSL solvers and would be useful in a preliminary design environment. Problems associated with a previously developed approximate VSL technique are addressed. Surface heat transfer and pressure predictions are comparable to both VSL results and experimental data. The present technique generates its own shock shape as part of its solution, and therefore could be used to provide more accurate initial shock shapes for higher-order procedures which require starting solutions.

Cheatwood, F. MCN.↗
NASA NTRS1991

An approximate viscous shock layer technique for calculating chemically reacting hypersonic flows about blunt-nosed bodies

An approximate axisymmetric method was developed which can reliably calculate fully viscous hypersonic flows over blunt nosed bodies. By substituting Maslen's second order pressure expression for the normal momentum equation, a simplified form of the viscous shock layer (VSL) equations is obtained. This approach can solve both the subsonic and supersonic regions of the shock layer without a starting solution for the shock shape. The approach is applicable to perfect gas, equilibrium, and nonequilibrium flowfields. Since the method is fully viscous, the problems associated with a boundary layer solution with an inviscid layer solution are avoided. This procedure is significantly faster than the parabolized Navier-Stokes (PNS) or VSL solvers and would be useful in a preliminary design environment. Problems associated with a previously developed approximate VSL technique are addressed before extending the method to nonequilibrium calculations. Perfect gas (laminar and turbulent), equilibrium, and nonequilibrium solutions were generated for airflows over several analytic body shapes. Surface heat transfer, skin friction, and pressure predictions are comparable to VSL results. In addition, computed heating rates are in good agreement with experimental data. The present technique generates its own shock shape as part of its solution, and therefore could be used to provide more accurate initial shock shapes for higher order procedures which require starting solutions.

Cheatwood, F. Mcneil↗