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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Wideband infrared heterodyne receiver front-end

A 10.6 micron infrared heterodyne receiver front end was developed for use in a wideband CO2 laser communications link. The infrared receiver employs an 850 MHz response PV HgCdTe photomixer which is mounted in a space quality housing, a low-noise 5 to 1500 MHz IF preamplifier, and a remote control panel. The receiver was designed to handle + or - 750 MHz of Doppler shift while providing an instantaneous information bandwidth of 400 MHz. The measured receiver sensitivity NEP was 1.0 x 10 to the 19th power W/Hz for a photomixer temperature of T sub m = 77 K and an IF beat frequency of 20 MHz and degraded to 1.75 x 10 to the 19th power W/Hz for T sub m = 130 K.

Peyton, B. J.↗
NASA NTRS1977

Optimize out-of-core thermionic energy conversion for nuclear electric propulsion

Current designs for out of core thermionic energy conversion (TEC) to power nuclear electric propulsion (NEP) were evaluated. Approaches to improve out of core TEC are emphasized and probabilities for success are indicated. TEC gains are available with higher emitter temperatures and greater power densities. Good potentialities for accommodating external high temperature, high power density TEC with heat pipe cooled reactors exist.

Morris, J. F.↗
NASA NTRS1977

An interstellar precursor mission

A mission out of the planetary system, with launch about the year 2000, could provide valuable scientific data as well as test some of the technology for a later mission to another star. Primary scientific objectives for the precursor mission concern characteristics of the heliopause, the interstellar medium, stellar distances (by parallax measurements), low energy cosmic rays, interplanetary gas distribution, and mass of the solar system. Secondary objectives include investigation of Pluto. Candidate science instruments are suggested. Individual spacecraft systems for the mission were considered, technology requirements and problem areas noted, and a number of recommendations made for technology study and advanced development. The most critical technology needs include attainment of 50-yr spacecraft lifetime and development of a long-life NEP system.

Jaffe, L. D.↗
NASA NTRS1979

Gallium-doped germanium, evaluation of photoconductors, part 1

Gallium-doped germanium far infrared detectors were evaluated at low temperatures and low background simulating the space environment. Signal and noise characteristics were determined for detector temperatures in the 2K to 4K range. Optimum performance occurs at about 2.5K for all devices tested. The minimum average NEP in the 40-130 micron region was found to be approximately 4 x 10 to the minus 17th power watt Hz(-1/2) at a frequency of 1 Hz.

Moore, W. J.↗
NASA NTRS1978

Reactor design and integration into a nuclear electric spacecraft

One of the well-defined applications for nuclear power in space is nuclear electric propulsion (NEP). Mission studies have identified the optimum power level (400 kWe). A single Shuttle launch requirement and science-package integration have added additional constraints to the design. A reactor design which will meet these constraints has been studied. The reactor employs 90 fuel elements, each heat pipe cooled. Reactor control is obtained with BeO/B4C drums in a BeO reflector. The balance of the spacecraft is shielded from the reactor with LiH. Power conditioning and reactor control drum drives are located behind the LiH with the power conditioning. Launch safety, mechanical design and integration with the power conversion subsystem are discussed.

Phillips, W. M.↗
NASA NTRS1979

Nuclear electric power and propulsion system for earth orbital and solar system exploration applications

This paper discusses the design of a Nuclear Electric Propulsion (NEP) system, selection of thrusters and propellant. Outer planet exploration requirements are compared to earth orbital power requirements and a nuclear electric power system with a power level of 200 to 250 kWe is recommended. Current technology appears capable of accomplishing the early missions and growth potential exists for accomplishing more difficult later missions without significant changes in the basic system.

Phillips, W. M.↗
NASA NTRS1980

Infrared heterodyne radiometer for airborne atmospheric transmittance measurements

An infrared heterodyne radiometer (IHR) was used to measure atmospheric transmittance at selected hydrogen fluoride (2.7 micrometer) and deuterium fluoride (3.8 micrometer) laser transitions. The IHR was installed aboard a KC-135 aircraft for an airborne atmospheric measurements program that used the sun as a backlighting source for the transmission measurements. The critical components are: a wideband indium antimonide (1nSb) photomixer, a CW HF/DF laser L0, a radiometric processor, and a 1900 K blackbody reference source. The measured heterodyne receiver sensitivity (NEP) is 1.3 x 10 to the -19th power W/Hz, which yields a calculated IHR temperature resolution accuracy of delta I sub S/-3 sub S = 0.005 for a source temperature of 1000 K and a total transmittance of 0.5. Measured atmospheric transmittance at several wavelengths and aircraft altitudes from 9.14 km (30,000 ft) to 13.72 km (45,000 ft) were obtained during the measurements program and have been compared with values predicted by the AFGL Atmospheric Line Parameter Compilation.

Wolczok, J. M.↗
NASA NTRS1980

Extending the operating temperature, wavelength and frequency response of HgCdTe heterodyne detectors

Near ideal optical heterodyne performance was obtained at GHz IF frequencies in the 10 micrometer wavelength region with liquid nitrogen cooled HgCdTe photodiodes. Heterodyne NEP's as low as 2.7 x 10 to the minus 20th power W/Hz at 100MHz, 5.4 x 10 to the minus 20th power W/Hz at 1.5 GHz, and 9.4 x 19 to the minus 20th power W/Hz at 3 GHz were achieved. Various physical phenomena which occur within a photodiode and affect heterodyne operation were examined in order to assess the feasibility of extending the operating temperature, wavelength, and frequency response of these HgCdTe photomixers.

Spears, D. L.↗
NASA NTRS1980

Lithium iodate, intracavity upconversion

The paper describes an internal CW parametric upconverter which uses a lithium iodate crystal and a CW argon laser. The upconversion reported demonstrates a noise equivalent power (NEP) of 5 x 10 to the -14th W/Hz to the 1/2th at 3.39-micron wavelength. Noise properties of the upconverter are outlined.

See, Y. C.↗
NASA NTRS1981

Multimission nuclear electric propulsion system for outer planet exploration missions

The conceptual design configuration of a nuclear electric propulsion system (NEP) with a multimission capability for both earth orbital and electric propulsion missions is discussed. Two basic types of space reactor power system concepts are analyzed emphasizing conduction coupled and radiation coupled systems, and a radiation coupled thermoelectric panel concept is schematically represented and described in detail. A nuclear-powered 100-kWe surveillance spacecraft concept is presented and the developmental phases are given including cost estimates. In addition, a system is described that seems to have the capability to perform all the outer planet missions.

Mondt, J. F.↗
NASA NTRS1982

Near-infrared linear array spectrometer for space applications

A 128-element InSb linear detector array read out with a field effect transistor (FET) multiplexing scheme has been developed at the Jet Propulsion Laboratory. State-of-the-art NEP, uniform response, on-detector charge integration, and very low focal plane heat load compared to that of discrete detector arrays allows this type of array to open new possibilities for spaceborne near-infrared imaging spectrometers. Large number of cooled detector elements are feasible with the new technology, making it practical to design sensitive spectrometers even for spinning spacecraft where simultaneous wavelength coverage is necessary to avoid confusion of spatial with spectral variations.

Apt, J.↗
NASA NTRS1983

Performance and materials aspects of Ge:Be photoconductors

Ge:Be photoconductors were developed for low photon background applications in the 30 to 50 MM wavelength region. These detectors provide higher responsivity and lower noise equivalent power (NEP) than the Ge:Ga detectors currently operating in this wavelength range. Beryllium doped single crystals were grown by the Czochralski method from a carbon susceptor under a vacuum of approx. one million torr. An optimum detective quantum efficiency of 46% at a background flux of 1.5 x 10 to the 8th power photons/second (7 x 10 to the 13th power W) was reported. Ge:Be detector performance is strongly influenced by the absolute concentrations and the concentration ratio of residual shallow donors and shallow acceptors.

Haegel, N. M.↗
NASA NTRS1983

Performance and materials aspects of Ge:Be photoconductors

Ge:Be photoconductors have been developed for low photon background applications in the 30 - 50 micron wavelength region. These detectors provide higher responsivity and lower noise equivalent power (NEP) than the Ge:Ga detectors currently operating in this wavelength range. Beryllium-doped single crystals were grown by the Czochralski method from a carbon susceptor under a vacuum of approximately 10 to the -6th torr. An optimum detective quantum efficiency of 46 percent at a background flux of 1.5 x 10 to the 8th photons/second (7 x 10 to the -13th W is reported. Ge:Be detector performance is strongly influenced by the absolute concentrations and the concentration ratio of residual shallow donors and shallow acceptors.

Haegel, N. M.↗
NASA NTRS1984

Bolometers - Ultimate sensitivity, optimization, and amplifier coupling

Theoretical expressions for Johnson noise and thermal noise in bolometers are considered, and optimization with respect to thermal conductivity and bias power is performed. Numerical approximations are given for the ultimate NEP of bolometers as a function of material parameters and compared with photon noise including photon correlations. A resonating capacitor is shown to improve the coupling to an amplifier, so that the amplifier need not limit performance even for very low temperature bolometers.

Mather, J. C.↗
NASA NTRS1984

Monolithic silicon bolometers

A new type of bolometer detector for the millimeter and submillimeter spectral range is described. The bolometer is constructed of silicon using integrated circuit fabrication techniques. Ion implantation is used to give controlled resistance vs temperature properties as well as extremely low 1/f noise contacts. The devices have been tested between 4.2 and 0.3 K. The best electrical NEP measured is 4 x 10 to the -16th W/Hz to the 1/2 at 0.35 K between 1- and 10-Hz modulation frequency. This device had a detecting area of 0.25 sq cm and a time constant of 20 msec at a bath temperature of 0.35 K.

Downey, P. M.↗
NASA NTRS1984

Integrating amplifiers using cooled JFETs

It is shown how a simple integrating amplifier based on commercially available JFET and MOSFET switches can be used to measure photocurrents from detectors with noise levels as low as 1.6 x 10 to the -18th A/root Hz (10 electrons/sec). A figure shows the basic circuit, along with the waveform at the output. The readout is completely nondestructive; the reset noise does not contribute since sampling of the accumulated charge occurs between resets which are required only when the stored charge has reached a very high level. The storage capacity ranges from 10 to the 6th to 10 to the 9th electrons, depending on detector parameters and linearity requirements. Data taken with an Si:Sb detector operated at 24 microns are presented. The responsivity agrees well with the value obtained by Young et al. (1981) in the transimpedance amplifier circuit. The data are seen as indicating that extremely low values of NEP can be obtained for integration times of 1 sec and that longer integrations continue to improve the SNR at a rate faster than the square root of time when background noise is not present.

Low, F. J.↗
NASA NTRS1984

Bolometers operated at 0.1 K and 0.2 K cooled by adiabatic demagnetization

The construction of bolometers operating at temperatures of 0.1 K and 0.2 K and cooled by adiabatic demagnetization is reported. The electrical noise-equivalent power (NEP) of the bolometers was found to be 1.8 and 6.6 x 10 to the -16th W/sq rt Hz, respectively. These values are within a factor of two of the expected performance based upon bolometer theory. The thermistor material used was gallium-doped single-crystal germanium, for which a resistivity temperature dependence is found.

Lesyna, L.↗
NASA NTRS1985

Ion propulsion technology requirements for planetary mission applications

Integrating a clustered, four engine ion propulsion system to the Mariner Mark II spacecraft is shown to reduce total trip time for the five proposed Mariner Mark II missions by fifteen years. In addition, this advanced Solar Electric Propulsion (SEP) system enables rendezvous encounters with five main belt asteroids rather than one. A precursor Advanced Capability Explorer (ACE) technology demonstration vehicle is proposed to investigate SEP spacecraft interaction and control requirements in support of these future mission opportunities. It is shown that the ACE spacecraft could be assembled from existing residual hardware, protoflight equipment and commercially available flight tested components. The ion propulsion system requirements to support ambitious Nuclear Electric Propulsion (NEP) missions are also examined and specific technology development objectives presented.

Aston, G.↗