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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

An extension of the dual magnetometer method for use on a dual spinning spacecraft

A method of estimating and correcting for the magnetic field of a dual spinning spacecraft has been developed by employing an extension of the dual magnetometer technique of Ness et al. (1971). This new method is useful for those situations in which a magnetometer boom of modest length (7-10 m) is attached to the spinning part of a large spacecraft (800-1000 kg). The purpose of using a dual spinning spacecraft is to accommodate two types of instruments: (1) imaging and similar 'pointed' remote sensing systems on the stationary platform and (2) fields, particles, and other in situ measuring instruments on the spinning portion. Present-day imaging systems are well known to exhibit large magnetic moments, sometimes displaced from the spacecraft center by a significant amount. The new method assumes that the stationary part of the spacecraft possesses a magnetic field which is represented by a combination of a dipole and a quadrupole field.

Lepping, R. P.↗
NASA NTRS1979

Extension, validation and application of the NASCAP code

Numerous extensions were made in the NASCAP code. They fall into three categories: a greater range of definable objects, a more sophisticated computational model, and simplified code structure and usage. An important validation of NASCAP was performed using a new two dimensional computer code (TWOD). An interactive code (MATCHG) was written to compare material parameter inputs with charging results. The first major application of NASCAP was performed on the SCATHA satellite. Shadowing and charging calculation were completed. NASCAP was installed at the Air Force Geophysics Laboratory, where researchers plan to use it to interpret SCATHA data.

Katz, I.↗
NASA NTRS1979

Extensions to the classical calculation of the effect of mutual shadowing in diffuse reflection

The classical method for accounting for the mutual shadowing among closely packed particles in multiple scattering calculations is extended in the following ways. (1) By modeling the particle distribution by a Poisson process with a varying density parameter, a 'Van der Waals' type approximation allows extension to a greater fractional volume density, D. In this case it is only required that D squared be much less than 1 instead of D being much less than 1. (2) In the case that the particle distribution is not uniform the classical calculation may be weighted by the pair correlation function of the distribution. (3) The use of the Markov chain formalism for radiative transfer allows inclusion of the effect of shadowing for two orders of scattering. For conditions such as might apply in Saturn's rings, the inclusion of this effect makes less than a 0.1% difference in the calculated phase curves, compared to previous calculations which have included shadowing only in the first scattering. The latter are thus shown to be quite accurate.

Esposito, L. W.↗
NASA NTRS1979

Global operators for delta functions - Extension to scattering states and the inclusion of spin

The paper presents an extension of the identities of Hiller, Sucher, and Feinberg for the evaluation of bound-state matrix elements of delta function operators, to scattering states. Attention is given to the technical difficulties encountered in the application of the scattering-state identities and how they can be overcome, including infrared singularities which arise if Coulomb forces are present and the velocity of the incident particle is small. In addition, both the scattering and bound-state identities are generalized to include spin-dependent contact interactions and spin-dependent Hamiltonians. Finally, it is stressed that the identities can be used to improve the accuracy of calculations of interest for diverse physical phenomena, ranging from positron annihilation to hyperfine structure.

Sucher, J.↗
NASA NTRS1979

The extension of the concept of the cosmic-ray path-length distribution to nonrelativistic energies

The concept of the cosmic-ray path-length distribution is examined. The corresponding cosmic-ray propagation calculational procedure has been justified theoretically at relativistic energies (Ginzburg and Syrovatskii, 1964) where the effects of ionization energy loss are negligible. The present paper extends the use of the path-length distribution concept in cosmic-ray propagation calculations to nonrelativistic energies. Sufficient constraints to effect this extension are presented. The solution of the cosmic-ray propagation equations in terms of a Green's function approach is also investigated and is used to provide a formulation of the path-length distribution at nonrelativistic as well as relativistic energies in terms of the cosmic-ray source distribution and the propagation characteristics of the interstellar medium. The leaky-box model of cosmic-ray propagation is also examined.

Lezniak, J. A.↗
NASA NTRS1979

A power extension package /PEP/ for the Shuttle Orbiter

A concept for solar array augmentation of the power normally provided by the Shuttle Orbiter fuel cells in support of payloads is discussed. Justification for the use of solar arrays rather than additional cryogenic fuel kits for extension of on-orbit stay time is presented. This is followed by a description of the array power system and an examination of its interfaces with the existing Orbiter fuel cell system. The system produces 29 kW total with 14 kW allocated to the Orbiter and 15 kW to payloads and permits an increase in on-orbit mission duration from 6 to approximately 20 days at 21 kW with four cryo kits. It is capable of producing full output in diverse vehicle orientations since the array is deployed and oriented by the Orbiter remote manipulator system (RMS). Power produced by the arrays is reduced to 32.25 to 32.5 volts by pulse-width-modulated buck voltage regulators to force the Orbiter fuel cells into an idle mode during the sunlighted portions of the orbit.

Ness, H. C.↗
NASA NTRS1979

Signature extension methods in crop area estimation

The Procedure B multispectral processing system is both multisegment and multistratum. It uses data from several LACIE-sized segments together and makes a proportion estimate for the entire group of segments as well as for the individual segments. In the clustering of data features, Procedure B produces multiple classes or strata rather than just two strata (as in Procedure 1), and performs stratified sampling on each of these mutliple strata in order to make a proportion estimate. Tests results for the components and for the overall performance of Procedure B are presented, and conclusions that can be drawn from these tests are discussed. The rationale for signature extension for crop area estimation is summarized.

Kauth, R. J.↗
NASA NTRS1980

Orbital Transfer Vehicle (OTV) engine study phase A, extension

The current Phase A-Extension of the OTV engine study program seeks to provide additional expander and staged combustion cycle data that will lead to design definition of the OTV engine. The proposed program effort will optimize the expander cycle engine concept (consistent with identified OTV engine requirements), investigate the feasibility of kitting the stage combustion cycle engine to provide extended low thrust operation, and conduct in-depth analysis of development risk, crew safety, and reliability for both cycles. Additional task will address costing of a 10k thrust expander cycle engine and support of OTV systems study contractors.

Sobin, A. J.↗
NASA NTRS1980

Orbital Transfer Vehicle (OTV) engine study. Phase A: Extension

The current Phase A-Extension of the OTV engine study program aims to provide additional expander and staged combustion cycle data that will lead to design definition of the OTV engine. The proposed program effort seeks to optimize the expander cycle engine concept (consistent with identified OTV engine requirements), investigate the feasibility of kitting the staged combustion cycle engine to provide extended thrust operation, and conduct in-depth analysis of development risk, crew safety, and reliability for both cycles. Additional tasks address the costing of a 10/K thrust expander cycle engine and support of OTV systems study contractors.

Sobin, A. J.↗
NASA NTRS1980

High-speed T-38A landing gear extension loads

Testing of T-38A landing gear extension at high speed and high altitude is described. The mechanisms are shown together with peak hydraulic pressure data during landing gear deployment with active and inactive strut door flaps. Results of strain gage measurements of stress on various structural members are included.

Schmitt, A. L.↗
NASA NTRS1980

Space Shuttle power extension package

A modification kit for the Space Transportation System (STS) Orbiter is proposed to provide more power and mission duration for payloads. The power extension package (PEP), a flexible-substrate solar array deployed on the Space Shuttle Orbiter remote manipulator system, can provide as much as 29 kW total power for durations of 10 to 48 days. The kit is installed only for those flights which require enhanced power or duration. The PEP is made possible by development of the flexible-substrate array technology and, in itself, contributes to the technology base for the use of large area solar cells. Modifications to the Orbiter thermal control and life support systems to improve heat balance and to reduce consumables are proposed. The changes consist of repositioning the Orbiter forward radiators and replacing the lithium hydroxide scrubber with a regenerable solid amine.

Loftus, J. P., Jr.↗
NASA NTRS1980

Method for estimating crack-extension resistance curve from residual strength data

A method is presented for estimating the crack extension resistance curve (R curve) from residual strength (maximum load against initial crack length) data for precracked fracture specimens. The method allows additional information to be inferred from simple test results, and that information is used to estimate the failure loads of more complicated structures. Numerical differentiation of the residual strength data is required, and the problems that it may present are discussed.

Orange, T. W.↗
NASA NTRS1981

Orbit Transfer Vehicle (OTV) engine study, phase "A" extension 2

The operation of the Advanced Expander Cycle OTV engine was evaluated at high mixture ratios, and intermediate and low thrust levels to establish the impact upon the engine design and costs, and/or operating characteristics. The engine operation was analyzed at tank head and pumped idle conditions with the nozzle extension retracted. The engine performance, weight, and envelope parametrics data were expanded to include mixture ratios of 7.5 and 8.0.

Christensen, K. L.↗
NASA NTRS1981

Extension of oblique incidence method to photo-orthotropic-elasticity

With the interpretation of isochromatic and isoclinic fringes in transparent, birefringent, orthotropic composites established, efforts were in progress to determine the individual values of the principal stresses or strains. Several methods utilize the photoelastic results only partially and rely on numerical procedures. Others attempt to obtain the required information based entirely on experimental data. The classical oblique incidence technique as applied to transversely isotropic birefringent composites, is presented. The proposed extension is verified by applying it to the problem of an orthotropic half-plane subjected to an edge-load.

Prabhakaran, R.↗
NASA NTRS1981

Comparative radiation testing of solar cells for the shuttle power extension package

The Power Extension Package (PEP) is the prime focus of a development program to produce low cost solar cells. The PEP is a 32 kilowatt flexible substrate, retrievable, solar array system for use on the Space Shuttle. Solar cell cost will be reduced by increasing cell area and simplifying cell and coverglass fabrication processes and specifications. The cost goal is to produce cells below $30 per watt. Two and ten ohm-cm silicon cells were investigated. This paper describes a unique radiation damage test and side-by-side comparison of candidate cell types with pre-and post-irradiation airplane calibration of outer space short-circuit current.

Baraona, C. R.↗
NASA NTRS1981

A validation of LTRAN2 with high frequency extensions by comparisons with experimental measurements of unsteady transonic flows

A high frequency extension of the unsteady, transonic code LTRAN2 was created and is evaluated by comparisons with experimental results. The experimental test case is a NACA 64A010 airfoil in pitching motion at a Mach number of 0.8 over a range of reduced frequencies. Comparisons indicate that the modified code is an improvement of the original LTRAN2 and provides closer agreement with experimental lift and moment coefficients. A discussion of the code modifications, which involve the addition of high frequency terms of the boundary conditions of the numerical algorithm, is included.

Hessenius, K. A.↗
NASA NTRS1982

On the application and extension of Harten's high resolution scheme

Extensions of a second order high resolution explicit method for the numerical computation of weak solutions of one dimensonal hyperbolic conservation laws are discussed. The main objectives were (1) to examine the shock resoluton of Harten's method for a two dimensional shock reflection problem, (2) to study the use of a high resolution scheme as a post-processor to an approximate steady state solution, and (3) to construct an implicit in the delta-form using Harten's scheme for the explicit operator and a simplified iteration matrix for the implicit operator.

Yee, H. C.↗
NASA NTRS1980

Introducing remote sensing to county-level agencies in Michigan through the Cooperative Extension Service

State and regional planning agencies in Michigan are aware of remote sensing technology, however, many agencies at the county and township level have not been introduced to its potential. This paper describes an educational effort undertaken by the MSU Remote Sensing Project and the Michigan Cooperative Extension Service aimed at reaching local decision makers. Remote sensing materials and a questionnaire were used to elicit interest and aid in planning the program. A series of seven workshops were held throughout Michigan for governmental officials and the staff of public agencies from 38 counties. Emphasis was placed on the characteristics, availability and usefulness of remotely-sensed data through a series of successful applications conducted in the state. The workshops were highly successful and many local decision makers are not aware of a new tool to call upon in their responses to land use and natural resource concerns.

Enslin, W. R.↗