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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 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Application of LANDSAT-2 data to the implementation and enforcement of the Pennsylvania Surface Mining Conservation and Reclamation Act

The author has identified the following significant results. Evaluation of LANDSAT imagery indicates severe limitations in its utility for surface mine land studies. Image stripping resulting from unequal detector response on satellite degrades the image quality to the extent that images of scales larger than 1:125,000 are of limited value for manual interpretation. Computer processing of LANDSAT data to improve image quality is essential; the removal of scanline stripping and enhancement of mine land reflectance data combined with color composite printing permits useful photographic enlargements to approximately 1:60,000.

Russell, O. R.↗
NASA NTRS1979

Comparison of analysis and experiment for self-acting seals for liquid-oxygen turbopumps

Two LOX turbopump applications were analyzed over ranges of pressure differential and speed. Predictions were compared with test results. A small seal was analyzed up to 141 m/sec and 310 N/sq cm differential and a larger seal up to 147 m/sec and 448 N/sq cm. Tests confirmed analytical predictions of operation without rubbing contact. The seals evidently operated with mostly liquid in the pads and mostly gas across the dam although the best prediction of trends was based on assuming gas throughout the entire seal.

Allen, G. P.↗
NASA NTRS1980

A versatile tunnel acts as a flexible duct

Tunnel activated by cable assembly can be expanded, contracted, and bent similar to flexible duct without uncoupling at either end. Tunnel was developed to join reusable space vehicle with cargo module and could be modified to be used as hydraulic or pneumatic hose or duct connecting complex moveable joints in remote manipulators and earth moving machinery.

Brown, N. D.↗
NASA NTRS1980

Self-acting lift-pad geometry for circumferential seals: A noncontacting concept

A segmented circumferential seal with lift pads for hydrodynamic action was analyzed over ranges of speed and sealed pressure. Performance predictions, which predicted noncontact operation for speeds as high as 600 revolutions per second at sealed pressures to 86 N/sq cm, are discussed. Performance tests were performed on the seals and compared with the performance predictions.

Allen, G. P.↗
NASA NTRS1982

Fast-Acting Electrohydraulic Servo

Electrohydraulic servo controls moving elements of airflow valve. Position of moving element and attached piston is monitored by linear variable-differential transformer (LVDT). Single-stage servo valve lets fluid into and out of piston volume in response to feedback signals from the LVDT.

Webb, J. A. J.↗
NASA NTRS1981

Three-dimensional periodic disturbances acting upon airfoils in cascade

A theory is developed for three-dimensional periodic gusts interacting with loaded airfoils. The unsteady disturbances are linearized with respect to the mean potential flow of the airfoils. The vorticity transport equation is then integrated analytically in a Lagrangian form. The vorticity vector shows strong variations in its magnitude and wavelength as it interacts with the flowfield of a lifting airfoil. The streamwise component of the vorticity increases significantly with flow acceleration and flow turning. For simplicity the rectangular fan approximation is used and a single Helmholtz-like equation is derived to characterize the unsteady 3D flowfield. This is a new and significant result. The present theory is first applied to symmetric airfoils.

Atassi, H.↗
NASA NTRS1981

Three-dimensional periodic disturbances acting upon airfoils in cascade

A theory for three dimensional periodic gusts interacting with loaded airfoils was developed. The unsteady disturbances are linearized with respect to the mean potential flow of the airfoils. The vorticity transport equation is integrated analytically in a Lagrangian form. The vorticity vector shows strong variations in its magnitude and wavelength as it interacts with the flow field of a lifting airfoil. The streamwise component of vorticity increases significantly with flow acceleration and flow turning. The rectangular fan approximation is used and a single Helmholtz equation is derived that characterizes the unsteady three dimensional flow field.

Atassi, H.↗
NASA NTRS1982

Forces acting on free carriers in semiconductors of inhomogeneous composition I, II

An investigation shows that the extended Wannier-Slater theorem with its position-dependent effective mass m cannot be considered a viable description of a semiconductor with compositional changes. The correct description of the behavior of the electron or hole flow in semiconductors in which the chemical composition changes gradually from position to position is more difficult. It is necessary to find a model Hamiltonian. This model Hamiltonian is to some extent arbitry, but it must be representative of a homogeneous sample. The difference between the true and the model Hamiltonian should be small in the sense that this difference may be considered a perturbation. However, a Hamiltonian with the required specifications can always be found provided that the compositional inhomogeneities do not change drastically over the distances of interest.

Von Roos, O.↗
NASA NTRS1985

Gradually Acting Shaft Stop

Mechanism brakes rotation with minimal shock. Balls rising on spiral ramp generate large axial force on brake friction plates, thereby generating large braking torque. Counter triggers rise of ball. Brake used to automatically stop control mechanisms on aircraft and ships. Serves as spindle brake on machine tool. On robot, prevents overtravel of arm or holds it in fixed position.

Lang, D. J.↗
NASA NTRS1984

Lateral fluid forces acting on a whirling centrifugal impeller in vaneless and vaned diffuser

Fluid forces on a rotating centrifugal impeller in whirling motion were studied. A two dimensional impeller installed in a parallel-walled vaneless and vaned diffuser whirled on a circular orbit with various positive and negative angular velocities. It is shown that the fluid forces exert a damping effect on the rotor in most operating conditions, but become excitatory when the impeller operates at very low partial discharge while rotating far faster than the whirl speed. The fluid forces were expressed in terms of mass, damping and stiffness matrices. Impellers with the same geometry and whirl condition are calculated. Quantitative agreement is obtained especially in positive whirl.

Ohashi, H.↗
NASA NTRS1983

The GSFC Advanced Compton Telescope (ACT)

A new telescope is being developed at GSFC for the study of point sources of gamma rays in the energy range 1-30 MeV. Using the detection principle of a Compton scatter in a 2.5 cm thick NaI(Tl) detector followed by absorption in a 15 cm thick NaI(Tl) detector, the telescope uses a rocking collimator for field-of-view reduction and background subtraction. Background reduction techniques include lead-plastic scintillator shielding, pulse shape discrimination and Anger camera operation to both NaI detectors, as well as a time-of-flight measurement between them. The instrument configuration and status is described.

Hartman, R.↗
NASA NTRS1982

Computer program for post-flight analysis of rigid body moments acting on a launch vehicle first stage

A FORTRAN coded computer program and method for evaluation of the rigid body disturbing moments for a launch vehicle first stage based on post-flight measurements is described. The technique is a straightforward deterministic approach. Residual moments are computed to satisfy the equations of motion. Residuals are expressed in terms of altered vehicle characteristics; the aerodynamic coefficients, thrust misalignment, and control effectiveness. This method was used on the Scout launch vehicle and uncovered several significant differences between flight data and wind tunnel data. The computer program is written in FORTRAN IV for a CDC CYBER 173 computer system.

Knauber, R. N.↗
NASA NTRS1986

Aerospace Safety Advisory Panel report to the NASA acting administrator

The level of activity of the Aerospace Safety Advisory Panel was increased smewhat during 1985 in concert with the increased mission rate of the National Space Transportation System, the evolutionary changes in management and operation of that program, and the preparation of the Vandenberg Launch Site; the implementation of the Program Definition Phase of the Space Station Program; and the actual flight testing of the X-29 research aircraft. Impending payload STS missions and NASA's overall aircraft operations are reviewed. The safety aspects of the LEASAT salvage mission were assessed. The findings and recommendation of the committee are summerized.

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