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  • SPACECRAFT PROPULSION AND POWER  (32)
  • 1990-1994  (30)
  • 1975-1979  (2)
  • 1
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    Numerical study of low-current steady arcs (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2011-08-24
    Beschreibung: The development of a high-efficiency CW YLF laser doped with Er,Tm,Ho: and featuring a strongly focusing resonator that collects a high density of pump power on the active crystal is described. The emission is investigated at 2.06 microns and a tuning range both at liquid-nitrogen (77 K) and at dry-ice (210 K) temperature. The noise characteristics and the long-term power stability of the laser is studied with an eye to employing this source for high-resolution spectroscopy in the 2-micron wavelength region. The detection of several absorption lines of NH3 at low pressure is described. The output power of the laser as a function of the power impinging on the crystal for different transmission of the output mirror is illustrated. The best result obtained is 1.46 W output for 3.2 W of argon pump. The minimum threshold achieved is 3.5 mW with a 1-percent transmission mirror. It is concluded that it is possible to develop a highly efficient Ho:YLF laser featuring low noise and sufficient tunability for high-resolution spectroscopy in the 2-micron region.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: Journal of Propulsion and Power (ISSN 0748-4658); 8; 5, Se; 1012-101
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 2
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    Low Earth orbital atomic oxygen micrometeoroid, and debris interactions with photovoltaic arrays (1991)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Polyimide Kapton solar array blankets can be protected from atomic oxygen in low earth orbit if SiO sub x thin film coatings are applied to their surfaces. The useful lifetime of a blanket protected in this manner strongly depends on the number and size of defects in the protective coatings. Atomic oxygen degradation is dominated by undercutting at defects in protective coatings caused by substrate roughness and processing rather than micrometeoroid or debris impacts. Recent findings from the Long Duration Exposure Facility (LDEF) and ground based studies show that interactions between atomic oxygen and silicones may cause grazing and contamination problems which may lead to solar array degradation.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: Space Photovoltaic Research and Technology Conference; 10 p
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 3
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    GaAs (AlGaAs)/CuInSe2 tandem solar cells. Technology status and future directions (1991)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: Mechanically stacked, high efficiency, lightweight, and radiation resistant photovoltaic cells based on a GaAs thin film top and CuInSe2 thin film bottom cells were developed, and are considered one of the most promising devices for planar solar array applications. The highest efficiency demonstrated so far using the 4 sq cm design is 23.1 pct. AM0, one sun efficiency when measured in four-terminal configuration. The current status of the GaAs(AlGaAs)/CuInSe2 tandem cell program is presented and future directions that will lead to cell efficiencies higher than 26 pct. Air Mass Zero (AM0). A new 8 sq cm cell design developed for a two terminal and voltage matched configuration to minimize wiring complexity is discussed. Optimization of the GaAs structure for a higher end-of-life performance and further improvement of tandem cells by utilizing AlGaAs as an top absorber are described. Results of environmental tests conducted with these thin film GaAs/CuInSe2 tandem cells are also summarized.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: NASA. Lewis Research Center, Space Photovoltiac Research and Technology Conference; 10 p
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 4
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    STME Hydrogen Mixer Study (1992)
    In:  CASI
    Details
    Publikationsdatum: 2013-08-31
    Beschreibung: The hydrogen mixer for the Space Transportation Main Engine is used to mix cold hydrogen bypass flow with warm hydrogen coolant chamber gas, which is then fed to the injectors. It is very important to have a uniform fuel temperature at the injectors in order to minimize mixture ratio problems due to the fuel density variations. In addition, the fuel at the injector has certain total pressure requirements. In order to achieve these objectives, the hydrogen mixer must provide a thoroughly mixed fluid with a minimum pressure loss. The AEROVISC computational fluid dynamics (CFD) code was used to analyze the STME hydrogen mixer, and proved to be an effective tool in optimizing the mixer design. AEROVISC, which solves the Reynolds Stress-Averaged Navier-Stokes equations in primitive variable form, was used to assess the effectiveness of different mixer designs. Through a parametric study of mixer design variables, an optimal design was selected which minimized mixed fuel temperature variation and fuel mixer pressure loss. The use of CFD in the design process of the STME hydrogen mixer was effective in achieving an optimal mixer design while reducing the amount of hardware testing.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: NASA. Goddard Space Flight Center, Tenth Workshop for Computational Fluid Dynamic Applications in Rocket Propulsion, Part 2; p 1093-1116
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 5
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    Experimental and analytical comparison of flowfields in a 110 N (25 Lbf) H2/O2 rocket (1991)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: A gaseous hydrogen/gaseous oxygen 110 N (25 lbf) rocket has been examined through the RPLUS code using the full Navier-Stokes equations with finite-rate chemistry. Performance tests were conducted on the rocket in an altitude test facility. Preliminary parametric analyses have been performed for a range of mixture ratios and fuel film cooling percentages. It is shown that the computed values of specific impulse and characteristic exhaust velocity follow the trend of the experimental data. Specific impulse computed by the code is lower than the comparable test values by about two to three percent. The computed characteristic exhaust velocity values are lower than the comparable test values by three to four percent. Thrust coefficients computed by the code are found to be within two percent of the measured values. It is concluded that the discrepancy between computed and experimental performance values could not be attributed to experimental uncertainty.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: AIAA PAPER 91-2283
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 6
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    Numerical study of high-area-ratio H2/O2 rocket nozzles (1991)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Calculations were made for high-area-ratio H2/O2 rocket nozzles by using the RPLUS code which employs an implicit finite volume, lower-upper symmetric successive over-relaxation scheme to solve the Navier-Stokes equations and the species equations in a coupled manner. The combustion processes of hydrogen and oxygen are modeled by an 8-species and 18-step reaction mechanism, and the turbulence is simulated by the Baldwin-Lomax turbulence model with a pressure gradient correction on the van Driest's damping constant in the inner-layer model. The calculated results for two different rocket nozzles are presented as contours, profiles, and performance values. The predicted specific impulse and thrust agree well with the experimental data and those from the industry standard code. It is demonstrated that the RPLUS code can be used for analysis of rocket nozzles.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: AIAA PAPER 91-2434
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 7
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    Calculations of gaseous H2/O2 thruster (1990)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Calculations were made for the gaseous H2/O2 thruster for the Space Station by using the RPLUS code which employs an implicit finite volume, LUSSOR scheme to solve the Navier-Stokes equations and the species equations. The combustion processes of hydrogen and oxygen are modeled by a 9 species and 18 step reaction mechanism and the turbulence is simulated by the Baldwin-Lomax turbulence model for the thruster wall boundary layer and the modified Prandtl's mixing length model for the reacting shear layer. Results are presented for different mixture ratios and fuel film cooling percents and compared with the experimental data. The calculated performance predictions for the thruster agree well with the experimental data and the results demonstrate that the RPLUS code can be used for design and analysis of thrusters and rockets.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: AIAA PAPER 90-2490
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 8
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    Heat transfer and pressure measurements and comparison with prediction for the SSME two-stage turbine (1992)
    In:  CASI
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: Time averaged Stanton number and surface pressure distributions are reported for the first stage vane row, the first stage blade row, and the second stage vane row of the Rocketdyne Space Shuttle Main Engine (SSME) two-stage fuel-side turbine. Unsteady pressure envelope measurements for the first blade are also reported. These measurements were made at 10 percent, 50 percent, and 90 percent span on both the pressure and suction surfaces of the first stage components. Additional Stanton number measurements were made on the first stage blade platform, blade tip, and shroud, and at 50 percent span on the second vane. A shock tube was used as a short duration source of heated and pressurized air to which the turbine was subjected. Platinum thin film heat flux gages were used to obtain the heat flux measurements, while miniature silicon diaphragm flush-mounted pressure transducers were used to obtain the pressure measurements. The first stage vane Stanton number distributions are compared with predictions obtained using a version of STAN5 and quasi-3D Navier-Stokes solution. This same quasi-3D N-S code was also used to obtain predictions for the first blade and the second vane.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: NASA-CR-190164 , NAS 1.26:190164 , CUBRC-6401
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
    BibTip Andere fanden auch interessant ...
    NASA TECHNICAL REPORTS
  • 9
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    Numerical study of low pressure nuclear thermal rockets (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The flowfields and performance of low pressure nuclear thermal rockets, which use hydrogen as a propellant, are studied by solving the Navier-Stokes equations and the species equations. A finite-rate chemistry model is used in the species equations, and the turbulence is simulated by the Baldwin-Lomax turbulence model with a modified van Driest's damping constant. The calculated results for the chamber temperatures of 3200 K and 4000 K with a chamber pressure range of 0.1 atm to 6 atm are presented as contours, centerline variations, and exit profiles. The performance values from the present calculations, such as the vacuum specific impulse and thrust, are compared with those from the 1D, inviscid equilibrium and frozen flow code.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: AIAA PAPER 92-3815
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
  • 10
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    Comparison of central axis and jet ring coolant supply for turbine disk cooling on a SSME-HPOTP model (1992)
    In:  Other Sources
    Details
    Publikationsdatum: 2019-06-28
    Beschreibung: The test facility, test methods and results are presented for an experimental study modeling the cooling of turbine disks in the blade attachment regions with multiple impinging jets, in a configuration simulating the disk cooling method employed on the Space Shuttle Main Engine oxygen turbopump. The study's objective was to provide a comparison of detailed local convection heat transfer rates obtained for a single center-supply of disk coolant with those obtained with the present flight configuration where disk coolant is supplied through an array of 19 jets located near the disk outer radius. Specially constructed disk models were used in a program designed to evaluate possible benefits and identify any possible detrimental effects involved in employing an alternate disk cooling scheme. The study involved the design, construction and testing of two full scale rotating model disks, one plane and smooth for baseline testing and the second contoured to the present flight configuration, together with the corresponding plane and contoured stator disks. Local heat transfer rates are determined from the color display of encapsulated liquid crystals coated on the disk in conjunction with use of a computer vision system. The test program was composed of a wide variety of disk speeds, flowrates, and geometrical configurations, including testing for the effects of disk boltheads and gas ingestion from the gas path region radially outboard of the disk-cavity.
    Schlagwort(e): SPACECRAFT PROPULSION AND POWER
    Materialart: AIAA PAPER 92-0255
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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    NASA TECHNICAL REPORTS
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