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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 1,531 records · Page 85
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Helium destruction and gamma-ray line emission in accreting neutron stars

The prevalent gamma-ray production channel of a neutron star - emission of 2.2-MeV photons from neutron-proton recombination - is reconsidered. The 2.2-MeV gamma-ray line flux and Compton-scattered continuum are calculated. The flux of gravitationally redshifted 2.2-MeV photons from the brightest accreting X-ray source Scorpius X-1 is about 10 exp -6 gamma/sq cm s, a factor of 20 below the sensitivities on the Compton Gamma-Ray Observatory. The destruction of accreted He-4 leads to significant abundances of lighter elements (D, H-3, He-3) in the upper atmosphere, which are determined. The destroyed He-4 is reformed through fusion reactions a few scale heights beneath the photosphere, and thus does not hamper H-ray bursts.

Bildsten, Lars↗
NASA NTRS1993

The rotation curve conspiracy and neutron star/asteroid models for Gamma Ray Bursts

Gamma Ray Bursts (GRB) were analyzed using new GRO/BATSE results in conjunction with older PVO and KONUS data. It is suggested that the distribution in space of the GRB sources must have an outer bounding surface which is approximately a sphere centered on the location. Neutron stars in some kind of extended halo around the Galaxy with the required mass of an infalling object of order about 10 exp 21 to 10 exp 23 gm are considered.

Salpeter, Edwin E.↗
NASA NTRS1930

Experiments with a Model Water Tunnel

This report describes a model water tunnel built in 1928 by the NACA to investigate the possibility of using water tunnels for aerodynamic investigations at large scales. The model tunnel is similar to an open-throat wind tunnel, but uses water for the working fluid.

Jacobs, Eastman N↗
NASA NTRS1937

Fuselage-drag tests in the variable-density wind tunnel: streamline bodies of revolution, fineness ratio of 5

Results are presented of the drag tests of six bodies of revolution with systematically varying shapes and with a fineness ratio of 5. The forms were derived from source-sink distributions, and formulas are presented for the calculation of the pressure distribution of the forms. The tests were made in the N.A.C.A. variable-density tunnel over a range of values of Reynolds number from about 1,500,000 to 25,000,000. The results show that the bodies with the sharper noses and tails have the lowest drag coefficients, even when the drag coefficients are based on the two-thirds power of the volume. The data shows the most important single characteristic of the body form to be the tail angle, which must be fine to obtain low drag.

Abbott, Ira H↗
NASA NTRS1938

Flow Observations with Tufts and Lampblack of the Stalling of Four Typical Airfoil Sections in the NACA Variable-density Tunnel

A preliminary investigation of the stalling processes of four typical airfoil sections was made over the critical range of the Reynolds Number. Motion pictures were taken of the movements of small silk tufts on the airfoil surface as the angle of attack increased through a range of angles including the stall. The boundary-layer flow also at certain angles of attack was indicated by the patterns formed by a suspension of lampblack in oil brushed onto the airfoil surface. These observations were analyzed together with corresponding force-test measurements to derive a picture of the stalling processes of airfoils.

Abbott, Ira H↗
NASA NTRS1945

Summary of Airfoil Data

The historical development of NACA airfoils is briefly reviewed. New data are presented that permit the rapid calculation of the approximate pressure distributions for the older NACA four-digit and five-digit airfoils by the same methods used for the NACA 6-series airfoils. The general methods used to derive the basic thickness forms for NACA 6 and 7-series airfoils together with their corresponding pressure distributions are presented. Detail data necessary for the application of the airfoils to wing design are presented in supplementary figures placed at the end of the paper. The report includes an analysis of the lift, drag, pitching-moment, and critical-speed characteristics of the airfoils, together with a discussion of the effects of surface conditions. Available data on high-lift devices are presented. Problems associated with lateral-control devices, leading-edge air intakes, and interference are briefly discussed, together with aerodynamic problems of application. (author)

Abbott, Ira H↗
NASA NTRS1932

Airship Model Tests in the Variable Density Wind Tunnel

This report presents the results of wind tunnel tests conducted to determine the aerodynamic characteristics of airship models. Eight Goodyear-Zeppelin airship models were tested in the original closed-throat tunnel. After the tunnel was rebuilt with an open throat a new model was tested, and one of the Goodyear-Zeppelin models was retested. The results indicate that much may be done to determine the drag of airships from evaluations of the pressure and skin-frictional drags on models tested at large Reynolds number.

Abbott, Ira H↗
NASA NTRS1933

The Elimination of Fire Hazard Due to Back Fires

A critical study was made of the operation of a type of back-fire arrester used to reduce the fire hazard of aircraft engines. A flame arrester consisting of a pack or plug of alternate flat and corrugated plates of thin metal was installed in the intake pipe of a gasoline engines; an auxiliary spark plug inserted in the intake manifold permitted the production of artificial back fires at will. It was found possible to design a plug which prevented all back fires from reaching the carburetor.

Theodorsen, Theodore↗
NASA NTRS1933

The NACA variable-density wind tunnel

This report describes the redesigned variable-density wind tunnel of the National Advisory Committee for Aeronautics; it supersedes a previous report that described the original tunnel. The operation of the balance and the method of testing are explained and the method of correcting and presenting airfoil data is described. A summary of the formulas for predicting the characteristics of finite wings from the airfoil section data as they are usually presented is also given.

Jacobs, Eastman N↗