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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 307 records · Page 17
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NASA NTRS1986

Moderate spectral resolution observations of 3 micron absorption features in highly obscured objects

The 3 micron absorption spectra of sources seen in or behind molecular clouds generally show a variety of absorption features. Three separate absorptions are used to explain these features. The cooled-grating array spectrometer (CGAS) at the NASA Infrared Telescope Facility was used to obtain spectra of the late-type mass-loss star OH 0739-12 and the protostars MonR2 IRS-2 and IRS-3 (solid circles). The differences between the spectra are discussed.

Smith, R. G.↗
NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles. Moderate lift/drag (0.75-1.5). Volume 1A, part 1: Executive summary, phase 1

Activities and significant results of Phase 1 of a study to access aeroassisted orbit transfer vehicle (AOTV) system technology are summarized. Broad concept evaluations were performed and the technology requirements and sensitivities for ground based AOTV's over a range of vehicle hypersonic lift/drag (L/D) from 0.75 to 1.5 were systematically identified and assessed. The four major task areas included systems analysis, system/subsystem trades, technology payoff assessment and plan, and cost analysis. Findings indicate that substantial performance improvements and hence cost benefit can be obtained by developing enhanced technologies such as: (1) low thrust advanced expander LOX-hydrogen engines with specific impulse of 480 to 490 sec; (2) reducing the external thermal protection system weight and increasing the maximum allowable bond/structure temperature; and (3) reducing the structural shell weight by improving the quality of the design allowable data, or use of advanced structural materials. Results also show that use of mid L/D AOTV's provide significant aerodynamic plane change capability and control authority over trajectory dispersions and off-nominal atmospheres.

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NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles. Moderate lift/drag (0.75-1.5): Volume 1A, part 2: Executive summary, phase 2

Significant achievements and activities of Phase 2 of a study to assess aeroassisted orbit transfer vehicle (AOTV) system technology are summarized. Phase 2 was directed towards identification and prioritization of technology payoffs of representative space based mid lift/drag ratio (L/D) AOTV's and the cryofueled propulsion subsystem - configuration interactions. Enhancing technology areas were identified which could provide substantial transport cost reduction. These include: (1) improved lifetime of storable propellant engines; (2) avionics weight reduction; (3) external thermal protection system weight reduction; (4) decrease of uncertainties in aerodynamic and aerothermodynamic performance; electrical power subsystem weight reduction due to incorporation of advanced materials; and (6) structural shell weight reduction. Results indicated that advanced aerothermodynamic methodology and aft end configuring may provide an enlarged allowable zone for engine nozzle protrusions into the separated flow region. Payload manifesting and non-hydrogen propellant manifesting at the space station is recommended.

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NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles: Moderate lift/drag (0.75-1.5). Volume 3: Cost estimates and work breakdown structure/dictionary, phase 1 and 2

Technology payoffs of representative ground based (Phase 1) and space based (Phase 2) mid lift/drag ratio aeroassisted orbit transfer vehicles (AOTV) were assessed and prioritized. A narrative summary of the cost estimates and work breakdown structure/dictionary for both study phases is presented. Costs were estimated using the Grumman Space Programs Algorithm for Cost Estimating (SPACE) computer program and results are given for four AOTV configurations. The work breakdown structure follows the standard of the joint government/industry Space Systems Cost Analysis Group (SSCAG). A table is provided which shows cost estimates for each work breakdown structure element.

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NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles: Moderate lift/drag (0.75-1.5). Volume 2: Supporting research and technology report, phase 1 and 2

Technology payoffs of representative ground based (Phase 1) and space based (Phase 2) mid lift/drag ratio (L/D) aeroassisted orbit transfer vehicles (AOTV) were assessed and prioritized. The methodology employed to generate technology payoffs, the major payoffs identified, the urgency of the technology effort required, and the technology plans suggested are summarized for both study phases. Technology issues concerning aerodynamics, aerothermodynamics, thermal protection, propulsion, and guidance, navigation and control are addressed.

Source record↗
NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles: Moderate lift/drag (0.75-1.5),volume 1B, part 1, study results

Significant performance benefits can be realized via aerodynamic breaking and/or aerodynamic maneuvering on return from higher altitude orbits to low Earth orbit. This approach substantially reduces the mission propellant requirements by using the aerodynamic drag, D, to brake the vehicle to near circular velocity and the aerodynamic lift, L, to null out accumulated errors as well as change the orbital inclination to that required for rendezous with the Space Shuttle Orbiter. A study was completed where broad concept evaluations were performed and the technology requirements and sensitivities for aeroassisted Orbital Transfer Vehicles (AOTVs) over a range of vehicle hypersonic L/D from 0.75 to 1.5 were systematically identified and assessed. The AOTV is capable of evolving from an initial delivery only system to one eventually capable of supporting manned roundtrip missions to geosynchronous orbit. Concept screenings were conducted on numerous configurations spanning the L/D = 0.75 to 1.5 range, and several with attractive features were identified. Initial payload capability was evaluated for a baseline of delivery to GEO, six hour polar, and Molniya orbits with return and recovery of the AOTV at LEO. Evolutionary payload requirements that were assessed include a GEO servicing mission and a manned GEO mission.

Source record↗
NASA NTRS1985

System technology analysis of aeroassisted orbital transfer vehicles: Moderate lift/drag (0.75-1.5), Volume 1B, part 2, study results

A complete compilation of the results from Phase 2 of a study to identify and prioritize the technology payoffs of representative space based mid lift/drag ratio (L/D) aeroassisted orbit transfer vehicles (AOTV) and the cryofueled propulsion subsystem - configuration interactions is presented. Several combinations of basing and launch vehicle options, staging scenarios, missions (delivery, servicing, or manned round trip), and target orbits were considered. Space basing of an AOTV opens up numerous configuration opportunities. The size can exceed the launch vehicle cargo bay envelope by resorting to orbital assembly and the AOTV weight can exceed the launch vehicle capability. With the absence of fully fueled tanks during a ground based launch much lighter gossamer type structures are possible that may result in performance gains. At the Space Station, payload rearranging or manifesting may prove attractive. Several major conclusions regarding aerothermodynamics, aerodynamics, payload manifesting, the propulsion subsystem, and systems issues are discussed.

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NASA NTRS1986

System concept for a moderate cost Large Deployable Reflector (LDR)

A study was carried out at JPL during the first quarter of 1985 to develop a system concept for NASA's LDR. Major features of the concept are a four-mirror, two-stage optical system; a lightweight structural composite segmented primary reflector; and a deployable truss backup structure with integral thermal shield. The two-stage optics uses active figure control at the quaternary reflector located at the primary reflector exit pupil, allowing the large primary to be passive. The lightweight composite reflector panels limit the short-wavelength operation to approximately 30 microns but reduce the total primary reflector weight by a factor of 3 to 4 over competing technologies. On-orbit thermal analysis indicates a primary reflector equilibrium temperature of less than 200 K with a maximum gradient of about 5 C across the 20-m aperture. Weight and volume estimates are consistent with a single Shuttle launch, and are based on Space Station assembly and checkout.

Swanson, P. N.↗
NASA NTRS1986

Amplification of electromagnetic waves by a ring-beam distribution of moderately relativistic electrons

The possibility of a new mechanism for the excitation of unstable modes in cold background plasmas is indicated in this paper. These beam-cyclotron modes are excited by the presence of the ring-beam distribution of suprathermal electrons. The usual eigenmode excitation of a cold plasma is reviewed, and the new type of instability is examined using a single-harmonic approximation and multiharmonic treatment.

Shi, B. R.↗
NASA NTRS1987

The moderately interacting Algol binary RS Cephei

In agreement with previous observers, it is found that the eclipsing binary RS Cep is an Algol-type semidetached system. From IUE spectra and Lick Observatory optical scans, the spectral types of the components are determined as B9.7e V + G8 III-IV. The effective temperature of the primary star is found to be 9670 K (with an uncertainty of about 150 K). From the photometric elements, the spectral types, and the semidetached nature of the system, a satisfactory model of the system is developed, giving masses 2.4 and 0.4 solar mass, radii 2.3 and 7.6 solar radii, and separation of the components 32 solar radii. This model leads to a distance of 910 pc; the color excess is E(B - V) = 0.03 mag. Balmer emission lines are observed in the optical scans, so that the system is a Be star. An IUE spectrum obtained during the total primary eclipse reveals a number of UV emission lines, typical for interacting Algols and W Ser stars. Power emitted in these lines is about twice as high as that in TT Hya or U Cep, therefore, RS Cep is a relatively active Algol system. A broad 'bulge' of excess relative flux is observed roughly between wavelengths 210 and 270 nm in the totality spectrum, and interpreted as broad blends of emission lines of Fe II; the same Fe II lines, formed in a circumstellar shell or disk, cause additional absorption in the out-of-eclipse spectra.

Plavec, Mirek J.↗
NASA NTRS1987

The moderately interacting Algol-type eclipsing binary RY Geminorum

Ultraviolet spectra of the Algol-type semidetached system RY Geminorum, whose components can be described as A0 V and K0 IV, have been matched to the ultraviolet spectrum by Kurucz (1979) model atmospheres, and a best fit is found for T(eff) = 9150 K. Comparison with standard star spectra requires that this value be raised to 9400 K. The color excess of the system is determined to be no more than E(B-V) = 0.03 mag; the distance to the system is about 360 pc. The masses are approximately 2.36 and 0.38 solar masses, and the radii are 2.5 and 5.8 solar radii, respectively. The separation of the two centers is 26 solar radii. Evidence for a circumstellar line absorption is found in optical and ultraviolet spectrograms, and evidence is found in IUE spectra taken in partial eclipse for circumstellar emission lines of the type detected previously in the WS Serpentis stars and in several semidetected systems of the Algol type.

Plavec, Mirek J.↗
NASA NTRS1988

The carbon chemistry in interstellar clouds toward moderately reddened stars

New data for C2 toward X Per, HD 206267, HD 207198, and Gamma Cep, for CH and CN toward X Per, and for CO toward HD 207198 have been obtained. The column densities of CH, C2, CN, and CO toward the stars in the Cepheus OB2 association are similar to reddened directions in Perseus and in Ophiuchus, indicating a similarity in physical conditions for the foreground clouds. The available data for other directions have been analyzed and the resulting data applied to study the transition from a photochemical regime to a chemical regime. The data for N(CN), N(C2), and N(CO) have been plotted against N(CH) to elucidate the chemistry of carbon-bearing molecules more clearly. The observed trends for CN and C2 suggest a change in slope at N(CH) of roughly 5 x 10 to the 13th/sq cm. Below this value, photodestruction is predicted to dominate and the slope is determined by the photochemistry. For directions with more N(CH), a linear correlation consistent with destruction by chemical reactions is expected.

Federman, S. R.↗
NASA NTRS1989

Positive ion composition in the polar D and E regions measured during moderate ionospheric absorption

During the MAC/Epsilon campaign a mass spectrometer probe was flown on a rocket launched from Andoya (Norway) on 12 November 1987 at 0021 UT providing partial ion density profiles in the altitude range between less than 50 to 125 km. Due to the short sampling period of 0.17 seconds structural features could be observed at approx. 150 m height resolution in the regimes where metal ions occur and where cluster ions are dominant. The observations were made during stable ionospheric absorption of 1 to 1.5 dB. Preliminary results are presented and discussed.

Laemmerzahl, P.↗
NASA NTRS1988

On the feasibility of correlation tracking at moderate resolution

The measurement of photospheric surface flows via the correlation tracking of white-light intensity features at low resolution has been demonstrated using Solar Optical Universal Polarimeter data obtained from Spacelab-2. The data were artificially degraded, but still free of seeing distortion. It is suggested that apertures as small as 10-14 cm on a space-based platform can be used to measure large-scale horizontal motions.

Bogart, R. S.↗
NASA NTRS1988

Moderate resolution imaging spectrometer-nadir (MODIS-N) - Progress 1988

The paper describes progress made through 1987 in refining the required characteristics of the MODIS-N, which is one of two MODIS sensors being planned as a facility for the earth observing system. The MODIS-N will make it possible to observe new characteristics of the land and ocean surfaces and the troposphere at least once every three days over the entire globe for a decade following launch. Spatial resolutions of 1000 m or better are expected.

Salomonson, V. V.↗
NASA NTRS1988

Optical system design alternatives for the Moderate-Resolution Imaging Spectrometer-Tilt (MODIS-T) for the Earth Observing System (EOS)

The MODIS consists of two synergistic sensors with a total of 104 spectral bands in the 0.4-14.2-micron range. MODIS-T (Tilt) is one of these sensors. It is a 64-channel imaging spectrometer with a required 10 nm spectral resolution (FWHM) in the 400 to 1040 nm spectral range. The system will have a 1 km IFOV, a wide scan for global coverage in three days, and be capable of being pointed fore and aft of nadir by + or - 50 degrees.

Maymon, Peter W.↗
NASA NTRS1988

LDV surveys over a fighter model at moderate to high angles of attack

The vortex flowfield over an advanced twin-tailed fighter configuration has been studied in a low-speed wind tunnel at two angles of attack using LDV, along with laser light sheet and surface flow visualizations. At 15 deg angles of attack, the vortices generated by the wing leading edge extension (LEX) were found to be unburst over the model and to pass outboard of the vertical tail. At 25 deg angle of attack, the vortices were shown to burst in the vicinity of the wing-LEX intersection and to impact directly on the vertical tails.

Sellers, William L., III↗
NASA NTRS1988

Magnetospheric convection during quiet or moderately disturbed times

The processes which contribute to the large-scale plasma circulation in the earth's environment during quiet times, or during reasonable stable magnetic conditions are reviewed. The various sources of field-aligned current generation in the solar wind and the magnetosphere are presented. The generation of field-aligned currents on open field lines connected to either polar cap and the generation of closed field lines of the inner magnetosphere are examined. Consideration is given to the hypothesis of Caudal (1987) that loss processes of trapped particles are competing with adiabatic motions in the generation of field-aligned currents in the inner magnetosphere.

Caudal, G.↗