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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Plume Impingement to the Lunar Surface: A Challenging Problem for DSMC

The President's Vision for Space Exploration calls for the return of human exploration of the Moon. The plans are ambitious and call for the creation of a lunar outpost. Lunar Landers will therefore be required to land near predeployed hardware, and the dust storm created by the Lunar Lander's plume impingement to the lunar surface presents a hazard. Knowledge of the number density, size distribution, and velocity of the grains in the dust cloud entrained into the flow is needing to develop mitigation strategies. An initial step to acquire such knowledge is simulating the associated plume impingement flow field. The following paper presents results from a loosely coupled continuum flow solver/Direct Simulation Monte Carlo (DSMC) technique for simulating the plume impingement of the Apollo Lunar module on the lunar surface. These cases were chosen for initial study to allow for comparison with available Apollo video. The relatively high engine thrust and the desire to simulate interesting cases near touchdown result in flow that is nearly entirely continuum. The DSMC region of the flow field was simulated using NASA's DSMC Analysis Code (DAC) and must begin upstream of the impingement shock for the loosely coupled technique to succeed. It was therefore impossible to achieve mean free path resolution with a reasonable number of molecules (say 100 million) as is shown. In order to mitigate accuracy and performance issues when using such large cells, advanced techniques such as collision limiting and nearest neighbor collisions were employed. The final paper will assess the benefits and shortcomings of such techniques. In addition, the effects of plume orientation, plume altitude, and lunar topography, such as craters, on the flow field, the surface pressure distribution, and the surface shear stress distribution are presented.

Lumpkin, Forrest↗
NASA NTRSDate not supplied

Applications of PLIF within Supersonic/Hypersonic Flows relevant to Space Technology and Exploration

We summarize two recent applications of planar laser-induced fluorescence using seeded nitric oxide (NO-PLIF) within two different large-scale facilities for space technology and exploration. The first measurement campaign described is the NO-PLIF measurements performed within the 31-in Mach 10 air tunnel at NASA Langley Research Center for flow visualization, velocity, and temperature measurements of the wake produced by a hypersonic blunt-body. PLIF within this wake-flow was performed to support the developments of HIAD (hypersonic inflatable aerodynamic decelerator) technology, including the recent LOFTID flight mission. The second campaign is the NO-PLIF measurements performed within a 20-ft vacuum chamber at the NASA Marshall Space Flight Center for flow visualization of a Mach 5 plume impinging on a flat plate under rarefied and continuum conditions. PLIF within this supersonic flow was performed to support future lunar and Martian lander missions by investigating the plume impingement behavior. While both of these measurement campaigns were performed using 10 Hz PLIF laser systems, current efforts include utilization of tunable high-repetition-rate lasers for NO-PLIF measurements up to kHz-MHz rates.

Planar laser-induced fluorescence↗
NASA NTRS1976

Vaporization of graphite in the temperature range of 4000 to 4500 K

The vaporization of graphite under intense laser radiation is considered both theoretically and experimentally. Under intense radiation, the mass-loss rate can be high enough to cause the flow in the laser plume to be supersonic. It is shown that under these conditions the vaporization process is coupled to the plume gasdynamics and the mass-loss rate for graphite is 62% of the free vaporization rate. Experimental results are presented for surface temperatures from 3985 to 4555 K and mass-loss rates from 0.56 to 27.0 g per sq cm sec. The results are used to determine the vapor pressure of graphite in a pressure range of 2 to 11 atm, and the values are shown to be in agreement with the JANAF vapor pressure curve.

Lundell, J. H.↗
NASA NTRS1975

Test data from solid propellant plume aerodynamics test program in Ames 6 x 6 foot supersonic wind tunnel (shuttle test FA7) (Ames test 033-66)

The aerodynamic effects of plumes from hot combustion gases in the presence of a transonic external flow field were measured to advance plumes simulation technology, extend a previously acquired data base, and provide data to compare with the effects observed using cold gas plumes. A variety of underexpanded plumes issuing from the base of a strut-mounted ogive-cylinder body were produced by combusting solid propellant gas generators. The gas generator fired in a short-duration mode (200 to 300 msec). Propellants containing 16 percent and 2 percent A1 were used, with chamber pressures from 400 to 1800 psia. Conical nozzles of 15 deg half-angle were tested with area ratios of 4 and 8. Pressures were measured in the gas generator combustion chamber, along the nozzle wall, on the base, and along the body rear exterior. Schlieren photographs were taken for all tests. Test data are presented along with a description of the test setup and procedures.

Hair, L. M.↗
NASA NTRS1976

Interactive analysis of thermal imagery

Necessary knowledge is presented on data acquisition and preparation for analysis of thermal imagery of power plant heated discharges remotely sensed from an aircraft, with special emphasis on analog to digital conversion of analog tapes acquired during scanning and to geometrical scaling. The central element in the interactive analysis of thermal imagery is an interactive graphics computer terminal which allows an interpreter to effectively interact with a large-scale computer, providing decisions or data as computations are carried out. A temperature calibration is performed, which the interpreter may test anywhere on the image. When satisfied that calibration is correct, the portion of the image to be analyzed is outlined. Printed and microfiche analyses of the plume are produced. The flow chart of programs for analysis of thermal imagery is presented and discussed in some detail.

Madding, R. P.↗
NASA NTRS1980

The direct observation of unidirectional solidification as a function of gravity level

A saturated solution of NH4 Cl-H2O was solidified unidirectionally on earth at 1 g and in a suborbital rocket at 0.001 g. In the 1 g experiment, extensive fluid flow was apparent, creating plumes which carry numerous crystallites vertically above the interface in a manner associated with freckling in castings. During growth the interface grew into the liquid at the same rate as the individual dendrites. When solidified in low g, the interface grew at a slower rate than the individual dendrites. No plumes of liquid carrying crystals were seen, but several crystals did appear and grow ahead of the interface. Growth rates, dendrite morphologies and preferred crystallographic orientations are compared for the two experiment conditions. Results indicate that solidification in low gravity produces more uniform dendrite arm spacings, and tends to be controlled by diffusion and crystallographic orientation.

Johnston, M. H.↗
NASA NTRS1981

Microwave radiometer measurement of tidally induced salinity changes off the Georgia coast

A quasi-synoptic survey of tidally induced salinity changes off the Georgia coast was performed by using a L band microwave radiomater onboard a NASA aircraft. Salinity maps were obtained for ebb and flood conditions in order to define the salinity distributions near rivers and sounds and major changes that occur from ebb flow to flood flow. The Savannah River plume dominated the salinity regime and extended out from the Savannah River mouth about 12 km during ebb tidal conditions. The plume merged into a band of low salinity water extending along the Georgia-South Carolina coast which was produced by the many river sources of freshwater entering the coastal waters. The changes in salinity observed offshore of the river plume area were consistent with estimates of the changes that would occur over a typical tidal excursion perpendicular to the observed gradient.

Kendall, B. M.↗
NASA NTRS1988

Evaluation of the communications impact of a low power arcjet thruster

The interaction of a 1 kW arcjet thruster plume with a communications signal is evaluated. A two-parameter, source flow equation has been used to represent the far flow field distribution of the arcjet plume in a realistic spacecraft configuration. Modelling the plume as a plasma slab, the interaction of the plume with a 4 GHz communications signal is then evaluated in terms of signal attenuation and phase shift between transmitting and receiving antennas. Except for propagation paths which pass very near the arcjet source, the impacts to transmission appear to be negligible. The dominant signal loss mechanism is refraction of the beam rather than absorption losses due to collisions. However, significant reflection of the signal at the sharp vacuum-plasma boundary may also occur for propagation paths which pass near the source.

Carney, Lynnette M.↗
NASA NTRS1988

Evaluation of the communications impact of a low power arcjet thruster

The interaction of a 1 kW arcjet thruster plume with a communications signal is evaluated. A two-parameter, source flow equation has been used to represent the far flow field distribution of the arcjet plume in a realistic spacecraft configuration. Modelling the plume as a plasma slab, the interaction of the plume with a 4 GHz communications signal is then evaluated in terms of signal attenuation and phase shift between transmitting and receiving antennas. Except for propagation paths which pass very near the arcjet source, the impacts to transmission appear to be negligible. The dominant signal loss mechanism is refraction of the beam rather than absorption losses due to collisions. However, significant reflection of the signal at the sharp vacuum-plasma boundary may also occur for propagation paths which pass near the source.

Carney, Lynnette M.↗
NASA NTRS1992

Exhaust plumes and their interaction with missile airframes - A new viewpoint

The present, novel treatment of missile airframe-exhaust plume interactions emphasizes their simulation via a formal solution of the Reynolds-averaged Navier-Stokes (RNS) equation and is accordingly able to address the simulation requirements of novel missiles with nonconventional/integrated propulsion systems. The method is made possible by implicit RNS codes with improved artificial dissipation models, generalized geometric capabilities, and improved two-equation turbulence models, as well as by such codes' recent incorporation of plume thermochemistry and multiphase flow effects.

Dash, S. M.↗
NASA NTRS1998

Numerical Simulation of the Generation of Axisymmetric Mode Jet Screech Tones

An imperfectly expanded supersonic jet, invariably, radiates both broadband noise and discrete frequency sound called screech tones. Screech tones are known to be generated by a feedback loop driven by the large scale instability waves of the jet flow. Inside the jet plume is a quasi-periodic shock cell structure. The interaction of the instability waves and the shock cell structure, as the former propagates through the latter, is responsible for the generation of the tones. Presently, there are formulas that can predict the tone frequency fairly accurately. However, there is no known way to predict the screech tone intensity. In this work, the screech phenomenon of an axisymmetric jet at low supersonic Mach number is reproduced by numerical simulation. The computed mean velocity profiles and the shock cell pressure distribution of the jet are found to be in good agreement with experimental measurements. The same is true with the simulated screech frequency. Calculated screech tone intensity and directivity at selected jet Mach number are reported in this paper. The present results demonstrate that numerical simulation using computational aeroacoustics methods offers not only a reliable way to determine the screech tone intensity and directivity but also an opportunity to study the physics and detailed mechanisms of the phenomenon by an entirely new approach.

Shen, Hao↗
NASA NTRS1976

Radiative Vaporization of Graphite in the Temperature Range of 4000 to 4500 deg K

The vaporization of graphite under intense laser radiation is considered both theoretically and experimentally. Under intense radiation, the mass-loss rate can be high enough to cause the flow in the laser plume to be supersonic. Under these conditions, the vaporization process is coupled to the plume gasdynamics. Experimental results are presented for surface temperatures of 3985 to 4555 K and mass-loss rates from 0.52 to 27.0 g/sq cm sec. The data are used to determine the vapor pressure of graphite in a range of 2 to 11 atm, and the results are shown to be in good agreement with the JANAF vapor pressure curve, if the vaporization coefficients are unity. The assumption of unity vaporization coefficients is shown to be reasonable by a comparison of the present results with other recent vapor pressure results for graphite.

Lundell, John H.↗
NASA NTRS2011

Orion Launch Abort Vehicle Attitude Control Motor Testing

Current Orion Launch Abort Vehicle (LAV) configurations use an eight-jet, solid-fueled Attitude Control Motor (ACM) to provide required vehicle control for all proposed abort trajectories. Due to the forward position of the ACM on the LAV, it is necessary to assess the effects of jet-interactions (JI) between the various ACM nozzle plumes and the external flow along the outside surfaces of the vehicle. These JI-induced changes in flight control characteristics must be accounted for in developing ACM operations and LAV flight characteristics. A test program to generate jet interaction aerodynamic increment data for multiple LAV configurations was conducted in the NASA Ames and NASA Langley Unitary Plan Wind Tunnels from August 2007 through December 2009. Using cold air as the simulant gas, powered subscale models were used to generate interaction data at subsonic, transonic, and supersonic test conditions. This paper presents an overview of the complete ACM JI experimental test program for Orion LAV configurations, highlighting ACM system modeling, nozzle scaling assumptions, experimental test techniques, and data reduction methodologies. Lessons learned are discussed, and sample jet interaction data are shown. These data, in conjunction with computational predictions, were used to create the ACM JI increments for all relevant flight databases.

Murphy, Kelly J.↗
NASA NTRS2016

Inviscid and Viscous CFD Analysis of Booster Separation for the Space Launch System Vehicle

This paper presents details of Computational Fluid Dynamic (CFD) simulations of the Space Launch System during solid-rocket booster separation using the Cart3D inviscid and Overflow viscous CFD codes. The discussion addresses the use of multiple data sources of computational aerodynamics, experimental aerodynamics, and trajectory simulations for this critical phase of flight. Comparisons are shown between Cart3D simulations and a wind tunnel test performed at NASA Langley Research Center's Unitary Plan Wind Tunnel, and further comparisons are shown between Cart3D and viscous Overflow solutions for the flight vehicle. The Space Launch System (SLS) is a new exploration-class launch vehicle currently in development that includes two Solid Rocket Boosters (SRBs) modified from Space Shuttle hardware. These SRBs must separate from the SLS core during a phase of flight where aerodynamic loads are nontrivial. The main challenges for creating a separation aerodynamic database are the large number of independent variables (including orientation of the core, relative position and orientation of the boosters, and rocket thrust levels) and the complex flow caused by exhaust plumes of the booster separation motors (BSMs), which are small rockets designed to push the boosters away from the core by firing partially in the direction opposite to the motion of the vehicle.

Viscous↗
NASA NTRS2020

Model Design and Pre-Test CFD Analysis for a Supersonic Retropropulsion Wind Tunnel Test

Future Mars human lander missions will require using powered descent beginning at supersonic conditions, something which has never been done before at Mars. Significant aerosciences challenges exist due to interactions between the retrorocket exhaust plumes and the freestream flow that alter the aerodynamic behavior of the powered descent vehicle. Historically, wind tunnel tests have been used to study supersonic retropropulsion with inert gas exhaust simulants. Also, SpaceX has successfully decelerated the Falcon 9 first stage numerous times by using powered flight at supersonic conditions. On the computational side, Reynolds-Averaged Navier-Stokes flowfield simulations are regularly completed at full-scale conditions. However, the available ground and flight data do not provide a basis for calibrating the computational uncertainties for aerodynamic interference forces and moments on proposed Mars descent vehicles, either because of insufficient data or dissimilar vehicles geometries and/or conditions. Thus, additional ground testing is needed to continue addressing the aerosciences risks for large-scale human Mars landers. To that end, a retropropulsion wind tunnel test will be conducted in the NASA Langley Unitary Plan Wind Tunnel in 2020. The test is designed to improve upon similar past tests, both in terms of model design and measured data. The test campaign will use subscale model geometries derived from the two current NASA powered descent reference vehicles: a blunt low lift-to-drag vehicle and a more slender geometry. This paper covers the reference vehicles, test objectives, model design, scaling parameters, test matrix, and computational analysis to date.

Karl T Edquist↗