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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Broadband adaptively-controlled polarization-separation network

A broadband adaptively-controlled frequency-reuse system has been developed and demonstrated. The system is designed to operate at 11 GHz and above, where polarization deorthogonalization due to rain effects is a problem. Direct analog control is used to continually correct for varying cross polarization conditions. Two cancellation networks are presented; an electro-mechanical RF waveguide network, and an all-electronic IF network; each adaptively controlled using pilot signals, detecting the amount of cross polarized pilot in each channel, and nulling the signal. Cancellations of cross polarization to greater than 35 dB below the copolarized signal are demonstrated.

Gianatasio, A. J.↗
NASA NTRS1979

Dual hybrid mode feed horn

Antenna feed horn is combination of corrugated, round, and tapered waveguide configurations that are dimensioned to excite He sub 11 and He sub 12 modes to illuminate reflector antenna more uniformly than antenna horns excited only in He sub 11 mode. Horn is adaptable to both symmetrical and asymmetrical Cassagrainian antennas.

Bathker, D. A.↗
NASA NTRS1979

Measuring the permittivity of gases and aerosols

Two-coupler microwave technique measures complex permittivity utilizing waveguide which encloses gas or aerosol. Using technique, blower continuously circulates substances to keep them homogeneous.

Trett, W. J.↗
NASA NTRS1979

X-band slotted array test panel and test fixture

Data from the development of the X-band slotted array test band, X-band array test fixture, and the X/L-band test fixture for the Support Instrumentation Requirements program are documented. An X-band array was built and installed with an existing L-band module in such a way as to permit antenna pattern measurements in a series of nonplanar configurations that might simulate the thermal effects of nonuniform solar illumination on the array in a space environment. This was accomplished with eight X-band subpanels mounted adjacently on individually adjusted supports which were then co-mounted to a larger frame which served to mount and physically distort the existing L-band module. The L-band module is a heavy electrical breadboard array section that was fabricated to demonstrate the performance capabilities of a slotted waveguide array at L-band frequencies. Drawings, mechanical analysis, and descriptions of test configurations are presented.

Source record↗
NASA NTRS1979

Extraterrestrial processing and manufacturing of large space systems, volume 1, chapters 1-6

Space program scenarios for production of large space structures from lunar materials are defined. The concept of the space manufacturing facility (SMF) is presented. The manufacturing processes and equipment for the SMF are defined and the conceptual layouts are described for the production of solar cells and arrays, structures and joints, conduits, waveguides, RF equipment radiators, wire cables, and converters. A 'reference' SMF was designed and its operation requirements are described.

Miller, R. H.↗
NASA NTRS1979

Extraterrestrial processing and manufacturing of large space systems. Volume 3: Executive summary

Facilities and equipment are defined for refining processes to commercial grade of lunar material that is delivered to a 'space manufacturing facility' in beneficiated, primary processed quality. The manufacturing facilities and the equipment for producing elements of large space systems from these materials and providing programmatic assessments of the concepts are also defined. In-space production processes of solar cells (by vapor deposition) and arrays, structures and joints, conduits, waveguides, RF equipment radiators, wire cables, converters, and others are described.

Miller, R. H.↗
NASA NTRS1977

Measured results of polarization crosstalk cancellation using LMS control

This paper discusses the use of wideband decoupling networks for the cancellation of polarization crosstalk in dual-polarized communication links. Measured cancellation performance for an all-electronic IF network and an RF electro-mechanical waveguide network are presented. Each of these networks utilizes LMS-type adaptive control techniques to adjust the cancellation network.

Baird, C. A.↗
NASA NTRS1978

An integrated optical preprocessor for multichannel analog data

As a precursor to the construction of a 16-channel device, a 3-channel integrated optical data preprocessor has been fabricated and tested. The device, which is fabricated in an outdiffused LiNbO3 waveguide, provides a signal related to the channel-by-channel difference between a prerecorded reference set and an incoming data set which is presented in the form of parallel analog voltages. The data are impressed upon the guided wave as a set of electrooptically induced phase shifts, and the comparison to the reference set is performed by holographic subtraction. The reference set can either be introduced as a separate operation or it can be 'learned' by the preprocessor during operation.

Verber, C. M.↗
NASA NTRS1979

Fiber optic rotation sensor /FORS/ signal detection and processing

The recent development of low-loss single-mode optical fiber waveguides for light has made possible a new class of inertial reference devices built on the principle of a closed loop interferometer. Light circulating through the loop in both directions experiences a relative phase delay proportional to rotation rate about the loop axis. This paper derives the phase delay and discusses signal detection, signal processing techniques and error sources. It is concluded that synchronous modulation and demodulation and an active gain control at the signal calculation level are required to eliminate drift errors. Potential performance is extraordinarily good; rotation rate sensitivity of a few milli-arc seconds per second and angular position random walk errors of an arc second per square root hour appear feasible.

Goss, W. C.↗
NASA NTRS1979

A reflected-wave ruby maser with K-band tuning range and large instantaneous bandwidth

A novel maser concept is outlined and a unique design described which permits wide bandwidth and waveguide tuning range by employing four stages cascaded via cryogenically cooled circulators. Theoretical considerations for gain, bandwidth, gain ripple, and noise temperature are included. Operated on a closed-cycle helium refrigerator with a superconducting persistence-mode magnet, the four-stage amplifier is tunable from 18.3 to 26.6 GHz with 30 dB of net gain and achieves 240 MHz of 3-dB bandwidth near the center of this band. The measured noise temperature is 13 + or - 2 K referred to the room-temperature input flange. Applications are foreseen utilizing cooled parametric downconverters and upconverters with this amplifier at IF to extend the low-noise performance up to millimeter frequencies and down to L-band for radio astronomy and planetary spacecraft communications.

Moore, C. R.↗
NASA NTRS1978

Theory of crossed-beam diffraction gratings

The operation of crossed-beam gratings is analyzed in terms of diffraction efficiency and beam quality, following Solymar's method's. General solutions for arbitrary beam widths, general beam profiles, and illumination with two beams are derived. A scheme for improving the beam quality of these gratings is proposed. The analysis should be useful in integrated optics for designing beam expanders, beam contractors, and mirrors, and for analyzing waveguide interferometers.

Kenan, R. P.↗
NASA NTRS1979

Fabrication and testing of a three-channel integrated optical data preprocessor

As a precursor to the construction of a 16-channel device, a 3-channel integrated optical data preprocessor has been fabricated and tested. The device, which is fabricated in an outdiffused LiNbO3 waveguide, provides a signal related to the channel-by-channel difference between a prerecorded reference set and an incoming data set which is presented in the form of parallel analog voltages. The data are impressed upon the guided wave as a set of electrooptically induced phase shifts, and the comparison to the reference set is performed by holographic subtraction. The reference set can either be introduced as a separate operation or it can be 'learned' by the preprocessor during operation.

Verber, C. M.↗
NASA NTRS1980

Dual-frequency bidirectional antenna

Simultaneous two-way communication at 20 and 30 GHz is possible with versatile paraboloid-dish antenna. Developed for two-way communications between Space Shuttle and ground station, antenna includes parabolic reflector, feed horn, waveguide network, and single-axis gimbal mounting. System resolution and accuracy are better than 1 percent.

Kummer, W. H.↗
NASA NTRS1981

Antenna feed for linear and circular polarization

Antenna system ransmits linearly-polarized microwave radio signal, yet circularly-polarized incoming signal is received without polarization-mismatch losses. Network uses only hybrid junctions, diplexer, and four-probe antenna; no waveguide switches are required. Other circuit arrangements are possible, using additional transmitters and receivers.

Bathker, D. A.↗
NASA NTRS1981

Tunable pulsed carbon dioxide laser

Transverse electrically-excited-atmosphere (TEA) laser is continuously tunable over several hundred megahertz about centers of spectral lines of carbon dioxide. It is operated in single longitudinal mode (SLM) by injection of beam from continuous-wave, tunable-waveguide carbon dioxide laser, which serves as master frequency-control oscillator. Device measures absorption line of ozone; with adjustments, it is applicable to monitoring of atmospheric trace species.

Megie, G. J.↗
NASA NTRS1980

A high resolution soil moisture radiometer

The design of an L-band high resolution soil moisture radiometer is described. The selected system is a planar slotted waveguide array at L-band frequencies. The square aperture is 74.75 m by 74.75 m subdivided into 8 tilted subarrays. The system has a 290 km circular orbit and provides a spatial resolution of 1 km. The aperture forms 230 simultaneous beams in a cross-track pattern which covers a swath 420 km wide. A revisit time of 6 days is provided for an orbit inclination of 50 deg. The 1 km resolution cell allows an integration time of 1/7 second and sharing this time period sequentially between two orthogonal polarization modes can provide a temperature resolution of 0.7 K.

Dod, L. R.↗
NASA NTRS1980

Investigation of direct integrated optics modulators

Direct modulation techniques applicable to integrated optics data preprocessors were investigated. Several methods of modulating a coherent optical beam by interaction with an incoherent beam were studied. It was decided to investigate photon induced conductivity changes in thin semiconductor cladding layers on optical waveguides. Preliminary calculations indicate significant changes can be produced in the phase shift in a propagating wave when the conductivity is changed by ten percent or more. Experimental devices to verify these predicted phase changes and experiments designed to prove the concept are described.

Batchman, T. E.↗