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Results for “IMPACT PRESSURE”

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 91 records · Page 5

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NASA NTRS1950

Investigation of High-Subsonic Performance Characteristics of a 12 Degree 21-Inch Conical Diffuser, Including the Effects of Change in Inlet-Boundary-Layer Thickness

Investigations were conducted of a 12 degree 21-inch conical diffuser of 2:l area ratio to determine the interrelation of boundary layer growth and performance characteristics. surveys were made of inlet and exit from, longitudinal static pressures were recorded, and velocity profiles were obtained through an inlet Reynolds number range, determined From mass flows and based on inlet diameter of 1.45 x 10(exp 6) to 7.45 x 10(exp 6) and a Mach number range of 0.11 to approximately choking. These investigations were made to two thicknesses of inlet boundary layer. The mean value, over the entire range of inlet velocities, of the displacement thickness of the thinner inlet boundary layer was approximately 0.035 inch and that of the thicker inlet boundary layer was approximately six times this value. The loss coefficient in the case of the thinner inlet boundary layer had a value between 2 to 3 percent of the inlet impact pressure over most of the air-flow range. The loss coefficient with the thicker inlet boundary layer was of the order of twice that of the thinner inlet boundary layer at low speeds and approximately three times at high speeds. In both cases the values were substantially less than those given in the literature for fully developed pipe flow. The static-pressure rise for the thinner inlet boundary layer was of the order of 95 percent of that theoretically possible over the entire speed range. For the thicker inlet boundary layer the static pressure rise, as a percentage of that theoretically possible, ranged from 82 percent at low speeds to 68 percent at high speeds.

Copp, Martin R.↗

NASA NTRS1972

Exhaust flow and propulsion characteristics of a pulsed MPD arc thruster

An experimental investigation of the near-field megawatt, single-shot exhaust is presented for the self-field and auxiliary field cases (0-2 T). Plasma impact pressure and number density are correlated to provide velocity profiles (30,000 to 70,000 m/sec), thrust (10 to 120 N), impulse (3 to 16 N-sec) and mass accounting. The data agree with Hugel's self-field theory for the case where thrust is produced entirely by electromagnetic force. The data show that the thrust monotonically increases with auxiliary field.

Michels, C. J.↗

NASA NTRS1972

Mean and fluctuating velocity contours and acoustic characteristics of subsonic and supersonic jets.

Mean and fluctuating velocity contours were determined for a convergent nozzle from surveys with impact pressure and piezoelectric pressure gauge probes, at Mach numbers of 0.6 to 1.4. For supersonic Mach numbers of 1.2 and 1.4, the length of the supersonic region increased as the square of the Mach number, and the peak pressure fluctuations occurred close to the sonic velocity contour. For subsonic Mach numbers of 0.6 to 1.0, the peak pressure fluctuations occurred in a toroidal region located approximately 4 to 6 diameters from the nozzle. The normalized sound power spectra for subsonic Mach numbers were similar, and for supersonic Mach numbers the power spectra shifted to the higher frequencies.

Nagamatsu, H. T.↗

NASA NTRS1972

Measurement of mass, momentum and energy distributions in a quasi-steady MPD discharge.

Piezoelectric impact pressure measurements in the exhaust flow of a quasi-steady MPD accelerator are used to compute the profile of momentum flux 25.4 cm downstream of a 2.8 MW discharge. The integral of this profile is in good agreement with the sum of calculated electromagnetic and measured electrothermal thrust components. Velocity vector profiles obtained by a time-of-flight technique reveal a radial variation of velocity ranging from 31,000 m/sec on the centerline to 11,000 m/sec at a radius of 20 cm. When combined with the momentum flux profiles, these velocities yield information on the distribution of mass and energy in the plasma exhaust.

Clark, K. E.↗

NASA NTRS1972

Exhaust flow and propulsion characteristics of a pulsed MPD arc thruster.

Experimental investigation of the near-field, megawatt, single-shot exhaust for the self-field and auxiliary field cases (0 to 2 tesla) for a pulsed MPD arc thrustor. Plasma impact pressure and number density are correlated to provide velocity profiles (30,000 to 70,000 m/sec), thrust (10 to 120 N), impulse (3 to 16 N-sec) and mass accounting. The data agree with Hugel's self-field theory for the case where thrust is produced entirely by electromagnetic force. The data show that the thrust monotonically increases with auxiliary field.

Michels, C. J.↗

NASA NTRS1973

Pulsed electromagnetic acceleration

Direct measurements of the power deposited in the anode of a multimegawatt MPD accelerator using thermocouples attached to a thin shell anode reveal a dramatic decrease in the fractional anode power from 50% at 200 KW input power to less than 10% at 20 MW power. The corresponding local power flux peak at a value of 10,000 W/sq cm at the lip of the anode exhaust orifice, a distribution traced to a corresponding peak in the local current density at the anode. A comparison of voltage-current characteristics and spectral photographs of the MPD discharge using quartz, boron nitride and plexiglas insulators with various mass injection configurations led to the identification of different voltage modes and regions of ablation free operation. The technique of piezoelectric impact pressure measurement in the MPD exhaust flow was refined to account for the effects due to probe yaw angle.

Jahn, R. G.↗

NASA NTRS1976

A flight instrumentation system for acquisition of atmospheric turbulence data

A flight instrumentation system for the acquisition of atmospheric turbulence data is described. Airflow direction transducers and an impact pressure transducer are the primary instruments for measuring vertical and lateral gust velocity, and a sensitive incremental pressure transducer is used to measure longitudinal gust velocity. Airplane motions, sensed by an inertial platform, are subtracted from the primary measurements during postflight data reduction to yield true gust velocity time histories. Salient engineering features of the instrumentation are discussed, and a complete description of the instrumentation is presented.

Meissner, C. W., Jr.↗

NASA NTRS1977

Effect of simulated Earth reentry exposure on mechanical properties of several oxide dispersion strengthened and superalloy sheet materials

The effects of simulated multiple reentry into the earth's atmosphere on the mechanical properties of several high temperature metallic sheet materials were evaluated. The materials included five tin-gage (nominally 0.025- or 0.037-cm) oxide dispersion strengthened (ODS) alloys and two thin-gage (nominally 0.037-cm) superalloys. Multiple reentry conditions were simulated through cyclic Plasma Arc Tunnel (PAT) exposure. PAT exposure generally consisted of 100 cycles of 600 second duration at 1255, 1366, or 1477 K in a Mach 4.6 airstream with an impact pressure of nominally 800 N/m2. PAT exposure generally produced a uniform oxide scale, oxide pits or intergranular oxidation, Kirkendall porosity, and alloy depletion zones except for the aluminum-containing ODS alloys. Only a uniform oxide scale was formed on the aluminum-containing ODS alloys. PAT exposure did not significantly affect the mechanical properties of the thin-gage (nominally 0.025- or 0.037-cm) alloys evaluated. Thus it appears that the microstructural changes produced by Plasma Arc Tunnel exposure has little influence on mechanical properties.

Whittenberger, J. D.↗

NASA NTRS1979

Effects of soft foam insulation impact

High temperature reusable surface insulation (HTRSI) tiles were impacted by a variety of foam insulation materials typical of the debris expected to strike the shuttle orbiter during the initial phases of flight. Failure of the HIRSI coating was strongly dependent on the density and size of the projectile. The failure threshold was as low as 140 ft/sec for rubber and as high as 740 ft/sec for styrofoam. In addition, the impact pressure was measured for a variety of debris materials as a function of velocity.

Rand, J. L.↗

NASA NTRS1981

Unsteady Newton-Busemann flow theory. Part 2: Bodies of revolution

Newtonian flow theory for unsteady flow past oscillating bodies of revolution at very high Mach numbers is completed by adding a centrifugal force correction to the impact pressures. Exact formulas for the unsteady pressure and the stability derivatives are obtained in closed form and are applicable to bodies of revolution that have arbitrary shapes, arbitrary thicknesses, and either sharp or blunt noses. The centrifugal force correction arising from the curved trajectories followed by the fluid particles in unsteady flow cannot be neglected even for the case of a circular cone. With this correction, the present theory is in excellent agreement with experimental results for sharp cones and for cones with small nose bluntness; gives poor agreement with the results of experiments in air for bodies with moderate or large nose bluntness. The pitching motions of slender power-law bodies of revulution are shown to be always dynamically stable according to Newton-Busemann theory.

Hui, W. H.↗

NASA NTRS1983

Spherical micro-glass particle impingement studies of thermoplastic materials at normal incidence

Light optical and scanning electron microscope studies were conducted to characterize the erosion resistance of polymethyl methacrylate (PMMA), polycarbonate (PC), polytetrafluoroethylene (PTFE) and ultra-high-molecular-weight-polyethylene (UHMWPE). Erosion was caused by a jet of spherical micro-glass beads at normal impact. During the initial stages of damage, the surfaces of these materials were studied using a profilometer. Material buildup above the original surface was observed on PC and PMMA. As erosion progressed, this buildup disappeared as the pit became deeper. Little or no buildup was observed on PTFE and on UHMWPE. UHMWPE and PTFE are the most resistant materials and PMMA the least. Favorable properties for high erosion resistance seem to be high values of ultimate elongation, and strain energy and a low value of the modulus of elasticity. Erosion-rate-versus-time curves of PC and PTFE exhibit incubation, acceleration and steady state periods. A continuously increasing erosion rate period was observed however for PMMA instead of a steady state period. At early stages of damage and at low impact pressure material removal mechanisms appear to be similar to those for metallic materials.

Rao, P. V.↗

NASA NTRS1984

Spherical microglass particle impingement studies of thermoplastic materials at normal incidence

Veerabhadra Rao, P.↗

NASA NTRS1992

Multishock Shield Against Meteoroids And Debris

Two documents discuss "multi-shock shielding" concept, according to which multiple spaced, very thin layers of material protects spacecraft against impacts by meteoroids, orbiting debris, or other projectiles traveling at hypervelocities. According to concept, incoming projectile broken up upon impact on first (outermost) layer, and fragments further broken up by subsequent layers. At each successive surface, impact pressure heats fragments, eventually melting and/or vaporizing them.

Cour-Palais, Burton G.↗

NASA NTRS1954

Measurement of Heat Transfer in the Turbulent Boundary Layer on a Flat Plate in a Supersonic Flow and Comparison with Skin Friction Results

Local heat-transfer rates on the surface of a heated flat plate at zero incidence to an air stream flowing at Mach numbers of 1.69 and 2.27 are presented. The Reynolds number range for both Mach numbers was 1 million to 10 million. Surface temperatures were maintained near recovery temperature. It was found that the variation of heat transfer with Mach number was in agreement with previously reported variations of directly measured skin friction with Mach number on unheated bodies. The variation with Mach number of the average skin coefficient, as determined from impact-pressure surveys, was in agreement with that from other momentum loss measurements but differed from the variation obtained from directly measured skin friction as reported by others. (author)

Pappas, C C↗

NASA NTRS1957

Exploratory Investigation of Boundary-Layer Transition on a Hollow Cylinder at a Mach Number of 6.9

The Reynolds number for transition on the outside of a hollow cylinder with heat transfer from the boundary layer to the wall has been investigated at a Mach number of 6.9 in the Langley 11-inch hypersonic tunnel. The type of boundary layer was determined from impact-pressure surveys and optical viewing. From a correlation of results obtained from various sources at lower Mach numbers (in the range 2.0 to 4.5) and data from the present tests with variable Reynolds number per inch, leading-edge thickness and free-stream Reynolds number per inch appear to be important considerations in flat-plate transition results. At a given Mach number, it appears that the Reynolds number based on leading-edge thickness is an important parameter that must be considered in comparisons of flat-plate transition data from various installations.

Bertram, Mitchel H↗

NASA NTRS1933

Results of extended tests of the Focke-Wulf F 19a "ente," a tail-first airplane

These investigations consisted chiefly of measurements of the take-off distance under various starting conditions and with the c.g. in different positions; of the climbing speed as a function of the impact pressure and location of the c.g.; of the longitudinal stability and fore-and-aft controllability and of the determination of the elevator forces and characteristics of the elevator control.

Hubner, Walter↗

NASA NTRS1991

The 1991 version of the plume impingement computer program. Volume 2: User's input guide

The Plume Impingement Program (PLIMP) is a computer code used to predict impact pressures, forces, moments, heating rates, and contamination on surfaces due to direct impingement flowfields. Typically, it has been used to analyze the effects of rocket exhaust plumes on nearby structures from ground level to the vacuum of space. The program normally uses flowfields generated by the MOC, RAMP2, SPF/2, or SFPGEN computer programs. It is capable of analyzing gaseous and gas/particle flows. A number of simple subshapes are available to model the surfaces of any structure. The original PLIMP program has been modified many times of the last 20 years. The theoretical bases for the referenced major changes, and additional undocumented changes and enhancements since 1988 are summarized in volume 1 of this report. This volume is the User's Input Guide and should be substituted for all previous guides when running the latest version of the program. This version can operate on VAX and UNIX machines with NCAR graphics ability.

Bender, Robert L.↗

NASA NTRS2000

Integrated Design and Analysis Overview

The objectives of the project this viewgraph presentation summarizes (integrated design and analysis) include the following: (1) Develop methodology for assessing the effects of manufacturing defects; (2) Develop damage tolerance criteria and damage tolerance database for reusable launch vehicle cryogenic tank structures, including impact, pressure leakage, cryogenic permeation, and validated damage prediction tools; and (3) Develop repair technology.

Gates, Tom S.↗