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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 NTRS1972

Analytical evaluation of jet noise source location technique utilizing an acoustically hard baffle with aperture

An analytical investigation was conducted on the experimental technique that uses shielding by an acoustically hard baffle to determine the location of noise sources in a jet. The jet exhausts through a circular hole in the baffle and the radiated acoustic power is considered to be generated by a distributed source along the jet axis. It is found that the effect of the baffle on the radiated power can be neglected only when the size of the source is on the order of a wavelength of the emitted sound or larger. Since noise sources in a jet are compact, the experimental technique is insufficient to identify these sources.

Norum, T. D.↗
NASA NTRS1974

Spaceborne synthetic aperture radar pilot study

A pilot study of a spaceborne sidelooking radar is summarized. The results of the system trade studies are given along with the electrical parameters for the proposed subsystems. The mechanical aspects, packaging, thermal control and dynamics of the proposed design are presented. Details of the data processor are given. A system is described that allows the data from a pass over the U. S. to be in hard copy form within two hours. Also included are the proposed schedule, work breakdown structure, and cost estimate.

Source record↗
NASA NTRS1972

The design, construction and testing of the optics for a 147-cm-aperture telescope

Geodetic optics research for the Air Force Cambridge Research Laboratories (AFCRL) is described. The work consisted mainly of the fabrication of the optical components for a telescope with a 152-cm-diam (60-in.) primary mirror masked down to 147-cm-diam for use by the AFCRL for a lunar ranging experiment. Among the achievements of this contract were the following: completion of the primary and secondary mirrors for a high-quality 147-cm-diam telescope system in eight months from the start of edging the primary; manufacture and testing of a unique center mount for the primary according to an AFCRL design that allowed for a thin-edged and therefore less-massive mirror; and development of a quantitative analysis of the wire test for calculating the departure of the mirror figure from the design figure quickly and accurately after each polishing step. This analysis method in conjunction with a knowledge of polishing rates for given weights and diameters of tools, mirror, and polishing materials should considerably reduce the polishing time required for future large mirrors.

Buchroeder, R. A.↗
NASA NTRS1975

Study of Synthetic Aperture Radar (SAR) imagery characteristics

Sources of geometric and radiometric fidelity errors in AN/APQ-102A radar imagery are discussed, along with a digital computer program to correct the distortions. The major effort, a computer program which will process digitalized recorded AN/APQ-102A phase histories into imagery, is described. All computer programs are listed.

Source record↗
NASA NTRS1974

A stabilized large-aperture far-infrared telescope gondola

Description of a recently developed balloon-borne 1-m far-infrared telescope designed to carry out astronomical observations and to map radiation from selected areas of the sky. The telescope optical system consists of a conventional Cassegrain arrangement with an f/2 aluminum primary mirror, spherically figured, which feeds a pyrex secondary mirror to produce an f/13.8 beam at the focal plane with a scale of 15.2 arc sec/mm. Three focal planes are provided. The infrared detectors consist of an array of four gallium-doped germanium bolometers fitted within a two-liter helium dewar. An altitude-azimuth mount design is used for attitude control, with the pointing objectives being achieved in two steps. The azimuth control system is capable of operation in a position mode, in which the sensing element is a servo-driven null magnetometer always pointed north, and in an inertial mode, in which the gyro is uncaged and becomes the azimuth reference. The elevation system also operates in both position and inertial modes. An auxiliary position control, powered by an independent battery and controlled by a separate tone command system, is provided in case of a primary system difficulty.

Hazen, N. L.↗
NASA NTRS1975

A balloon-borne ionization spectrometer with very large aperture for the detection of high energy cosmic rays

A balloon experiment which was used to determine the chemical composition of very high-energy cosmic rays up to and beyond 100 GeV/nucleon is described. The detector had a geometric factor of 1 sq m sr and a total weight on the balloon of 2100 kg. The apparatus consisted of an ionization spectrometer, spark chambers, and plastic scintillation and Cherenkov counters. It was calibrated at CERN up to 24 GeV/c protons and at DESY up to 7 GeV/c electrons. In October 1972 it was flown successfully on a stratospheric balloon.

Atallah, K.↗
NASA NTRS1976

Analysis of synthetic aperture radar imagery

The author has identified the following significant results. Average radar response for L-band like polarized system appeared to be related to the watershed runoff coefficients when the viewing angle was approximately 42 deg off nadir. Four requirements for radar systems used to verify applications of active microwave for water resources were identified: (1) first generation digital data will be required; (2) radar should be calibrated both internally and externally; (3) new systems should avoid radom use; and (4) images should be geometrically rectified prior to delivery to the user.

Blanchard, B. J.↗