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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 865 records · Page 48
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

An Adaptable Power System with Software Control Algorithm

A low cost, flexible and modular spacecraft power system design was developed in response to a call for an architecture that could accommodate multiple missions in the small to medium load range. Three upcoming satellites will use this design, with one launch date in 1999 and two in the year 2000. The design consists of modular hardware that can be scaled up or down, without additional cost, to suit missions in the 200 to 600 Watt orbital average load range. The design will be applied to satellite orbits that are circular, polar elliptical and a libration point orbit. Mission unique adaptations are accomplished in software and firmware. In designing this advanced, adaptable power system, the major goals were reduction in weight volume and cost. This power system design represents reductions in weight of 78 percent, volume of 86 percent and cost of 65 percent from previous comparable systems. The efforts to miniaturize the electronics without sacrificing performance has created streamlined power electronics with control functions residing in the system microprocessor. The power system design can handle any battery size up to 50 Amp-hour and any battery technology. The three current implementations will use both nickel cadmium and nickel hydrogen batteries ranging in size from 21 to 50 Amp-hours. Multiple batteries can be used by adding another battery module. Any solar cell technology can be used and various array layouts can be incorporated with no change in Power System Electronics (PSE) hardware. Other features of the design are the standardized interfaces between cards and subsystems and immunity to radiation effects up to 30 krad Total Ionizing Dose (TID) and 35 Mev/cm(exp 2)-kg for Single Event Effects (SEE). The control algorithm for the power system resides in a radiation-hardened microprocessor. A table driven software design allows for flexibility in mission specific requirements. By storing critical power system constants in memory, modifying the system code for other programs is simple. These constants can be altered also by ground command, or in response to an anomolous event. All critical power system functions have backup hardware functions to prevent a software or computer glitch from propagating. A number of battery charge control schemes can be implemented by selecting the proper control terms in the code. The architecture allows the design engineer to tune the system response to various system components and anticipated load profiles without costly alterations. A design trade was made with the size, weight and power dissipation of the electronics versus the performance of the power bus to load variations. Linear, fine control is maintained with a streamlined electronics design. This paper describes the hardware design as well as the software control algorithm. The challenges of closing the system control loop digitally is discussed. Control loop margin and power system performance is presented. Lab measurements are shown and compared to the system response of a hardware model running actual flight software.

Castell, Karen↗
NASA NTRS1995

SPITFIRE-1

The purpose of this effort is to develop low-cost rapid forming superplastic aluminum that will be evaluated in pilot production trials for automotive SPF components. The alloy development study conducted under SPITFIRE-1 showed that the addition of CU or Mn to the base 5083 aluminum alloy refined the grain size, leading to enhanced superplastic properties. In SPITFIRE-2, these alloy variants will be further refined and studied to meet the target properties established earlier in the program. Mechanical properties, component forming and post-forming properties will be evaluated. Also, the alloy production process, including thermomechanical processing (TMP) optimization to reduce production cost, will be investigated during SPITFIRE-2. After identifying preferred compositions and production processing, the most promising alloy will be manufactured into production coils for verification during SPITFIRE-3. Components will be produced from these coils in SPITFIRE-4, and the process and component performance will be assessed.

Ryntz, Edward F.↗
NASA NTRS1967

Adjustable, self-locking ladder includes optional work platform

Height-adjustable ladder with a self-locking platform at its top makes elevated locations more accessible, increases the quantity and size of tools handled there, and decreases the risk of disturbance or damage to components. The retractable platform adapts the ladder to normal use.

Webster, R. E.↗
NASA NTRS1971

Flammability testing of components

Flammability testing of components in the design of Apollo spacecraft is discussed. The purpose of component flammability testing was to determine the flammability characteristics of a variety of different sizes, shapes, and configurations of nonmetallic materials of similar or different types that make up a functional assembly, subsystem, or system in a spacecraft. The test criteria and requirements for the nonmetallic materials are presented.

Primeaux, G. R.↗
NASA NTRS1976

Petrographic and ferromagnetic resonance studies of the Apollo 15 deep drill core

Detailed petrographic grain size, and ferromagnetic resonance studies were performed on a representative suite of samples from the Apollo 15 deep drill core. Petrographic analyses of the 90-150 micron size fraction show a subtle upward increase in the ratio of mare to highland components. The agglutinate content at the FMR intensity normalized to FeO show that the soils in the core are generally immature to submature. The most striking feature shown by the maturity indices is a systematic decrease in maturity from the lunar surface to a depth of about 40 cm. Although other mechanisms are possible, the downward decrease in maturity can be attributed to in situ reworking over a time span of 400 m.y. at a 50% probability.

Heiken, G. H.↗
NASA NTRS1978

Fabrication of stainless steel clad tubing

The feasibility of producing stainless steel clad carbon steel tubing by a gas pressure bonding process was evaluated. Such a tube product could provide substantial chromium savings over monolithic stainless tubing in the event of a serious chromium shortage. The process consists of the initial assembly of three component tubesets from conventionally produced tubing, the formation of a strong metallurgical bond between the three components by gas pressure bonding, and conventional cold draw and anneal processing to final size. The quality of the tubes produced was excellent from the standpoint of bond strength, mechanical, and forming properties. The only significant quality problem encountered was carburization of the stainless clad by the carbon steel core which can be overcome by further refinement through at least three different approaches. The estimated cost of clad tubing produced by this process is greater than that for monolithic stainless tubing, but not so high as to make the process impractical as a chromium conservation method.

Kovach, C. W.↗
NASA NTRS1979

Photopolarimetry of scattering surfaces and their interpretation by computer model

Wolff's computer model of a rough planetary surface was simplified and revised. Close adherence to the actual geometry of a pitted surface and the inclusion of a function for diffuse light resulted in a quantitative model comparable to observations by planetary satellites and asteroids. A function is also derived to describe diffuse light emitted from a particulate surface. The function is in terms of the indices of refraction of the surface material, particle size, and viewing angles. Computer-generated plots describe the observable and theoretical light components for the Moon, Mercury, Mars and a spectrum of asteroids. Other plots describe the effects of changing surface material properties. Mathematical results are generated to relate the parameters of the negative polarization branch to the properties of surface pitting. An explanation is offered for the polarization of the rings of Saturn, and the average diameter of ring objects is found to be 30 to 40 centimeters.

Wolff, M.↗
NASA NTRS1978

Evaluation of worn SSME low pressure liquid oxygen turbopump bearing

The larger of two ball bearings used to support the rotor of the low pressure liquid oxygen turbopump in each of the shuttle main engines was analyzed to identify the cause of severe internal wear. The actual operating loads were calculated along with their direction and length of time at each load based on the size and location of the race contact paths. It is suggested that the engine component design be modified to reduce bearing stress and enhance lubrication.

Dufrane, K. F.↗
NASA NTRS1980

A stratospheric aerosol increase

Large disturbances were noted in the stratospheric aerosol content in the midlatitude Northern Hemisphere commencing about 7 months after the eruption of La Soufriere and less than 1 month after the eruption of Sierra Negra. The aerosol was characterized by a very steep size distribution in the 0.15 to 0.25 micron radius range and contained a volatile component. Measurements near the equator and at the South Pole indicate that the disturbance was widespread. These observations were made before the May 18 eruption of Mt. St. Helens.

Rosen, J. M.↗
NASA NTRS1980

Prototype microprocessor controller

A microcomputer controller for STDN antennas was developed. The microcomputer technology reduces the system's physical size by the implementation in firmware of functions. The reduction in the number of components increases system reliability and similar benefit is derived when a graphic video display is substituted for several control and indicator panels. A substantial reduction in the number of cables, connectors, and mechanical switches is achieved. The microcomputer based system is programmed to perform calibration and diagnostics, to update the satellite orbital vector, and to communicate with other network systems. The design is applicable to antennas and lasers.

Zarur, J.↗
NASA NTRS1983

Space Station Energy Sizing

A general schematic for a space station power system is described. The major items of interest in the power system are the solar array, transfer devices, energy storage, and conversion equipment. Each item will have losses associated with it and must be utilized in any sizing study, and can be used as a checklist for itemizing the various system components.

Rice, R. R.↗
NASA NTRS1984

The detection and location of lightning from space

A lightning mapper sensor was conceived for detecting and locating lightning over large areas of the earth's surface, taking into account also a measurement of the radiant energy and a recording of the time of lightning occurrence. The considered device will basically be a calibrated lightning imager. The type of information provided is currently not available on a large scale basis. By using the mapper, scientists will, for the first time, be able to study the electrosphere from scales on the order of the earth's diameter down to the size of individual storms (10 km). Attention is given to details regarding the sensor components, and questions of sensor performance.

Christian, H. J.↗
NASA NTRS1986

Design method for four-reflector type beam waveguide systems

Discussed is a method for the design of four reflector type beam waveguide feed systems, comprised of a conical horn and 4 focused reflectors, which are used widely as the primary reflector systems for communications satellite Earth station antennas. The design parameters for these systems are clarified, the relations between each parameter are brought out based on the beam mode development, and the independent design parameters are specified. The characteristics of these systems, namely spillover loss, crosspolarization components, and frequency characteristics, and their relation to the design parameters, are also shown. It is also indicated that design parameters which decide the dimensions of the conical horn or the shape of the focused reflectors can be unerringly established once the design standard for the system has been selected as either: (1) minimizing the crosspolarization component by keeping the spillover loss to within acceptable limits, or (2) minimizing the spillover loss by maintaining the crossover components below an acceptable level and the independent design parameters, such as the respective sizes of the focused reflectors and the distances between the focussed reflectors, etc., have been established according to mechanical restrictions. A sample design is also shown. In addition to being able to clarify the effects of each of the design parameters on the system and improving insight into these systems, the efficiency of these systems will also be increased with this design method.

Betsudan, S.↗
NASA NTRS1993

An alternative representation of the ice canopy for calculating microwave brightness temperatures over a thunderstorm

Passive microwave brightness temperatures (TBs) at 92 and 183 GHz from an aircraft thunderstorm overflight are compared with values calculated from radar-derived hydrometeor profiles and a modified proximity sounding. Two methods for modeling particles in the ice canopy are contrasted. The first is a 'traditional' approach employing Marshall-Palmer ice spheres. The second, or 'alternative', method partitions 20 percent of the ice water content into a Marshall-Palmer component for graupel and hail, and 80 percent into a modified gamma spherical particle size distribution function representing ice crystals. Results from the alternative approach are superior to those from the traditional method in the anvil and mature convective core. In the decaying convective region, the traditional approach yields better agreement with observed magnitudes. Neither method, however, matches the geometry of the observed TB depression associated with the decaying convective core. This is likely due to the presence of graupel, which is not detected as a special signature in radar reflectivity, but does diminish TBs through scattering. Brightness temperatures at the relatively high microwave frequencies considered are shown to be very sensitive to the ice-particle size distribution.

Muller, Bradley M.↗
NASA NTRS1957

Aerodynamic Characteristics of Missile Configurations with Wings of Low Aspect Ratio for Various Combinations of Forebodies, Afterbodies, and Nose Shapes for Combined Angles of Attack and Sideslip at a Mach Number of 2.01

An investigation has been made in the Langley 4-by-4-foot supersonic pressure tunnel to determine the aerodynamic characteristics of a series of missile configurations having low-aspect-ratio wings at a Mach number of 2.01. The effects of wing plan form and size, length-diameter ratio, forebody and afterbody length, boattailed and flared afterbodies, and component force and moment data are presented for combined angles of attack and sideslip to about 28 degrees. No analysis of the data was made in this report.

Robinson, Ross B↗
NASA NTRS1994

Hard X-rays from NGC 4151: A thermal origin?

We present a model for explaining the recent combined X-ray and low-energy gamma-ray observations of the Seyfert galaxy NGC 4151. According to this model, soft photons become Comptonized in a hot spot producing simultaneously the low-energy power law as observed by Ginga and the high-energy cutoff observed by the Oriented Scintillation Spectrometer Experiment (OSSE). Implementing recently developed theoretical calculations toward a generalized theory of Comptonization, we were able to find fits to the observations using only two parameters which characterize the physical quantities of the emission region: the plasma cloud optical depth and its temperature. We find that there is no need for additional nonthermal, reflection, or higher temperature thermal components to fit the aforementioned OSSE and Ginga observations. We derive in addition the size of the photon region and the temperature of the upscattered soft photons. We should emphasize, also, that any attempt at fitting only the high-energy parts of the spectrum (photon energies greater than 60 keV) by the Sunyaev & Titarchuk (1980) nonrelativistic Comptonization model leads to an underestimate of the Comptonization parameter y (or, equivalently, to an overestimation of the X-ray power-law spectral slope) and leads, as a result, to incorrect proportions between the low-energy and high-energy parts of the spectrum.

Titarchuk, Lev↗
NASA NTRS1995

Process Makes Thermoplastic Prepreg Ribbon

Manufacturing process produces ribbon of composite material (prepreg) consisting of continuous lengthwise fibers impregnated with thermoplastic resin. Ribbon can later be cut into sheets of required sizes and shapes, stacked, then heated under pressure to form composite-material structural components. Process accommodates variety of thermoplastic resins and variety of fibers.

Wilson, Maywood L.↗
NASA NTRS1999

Fabrication and Assembly of High-Precision Hinge and Latch Joints for Deployable Optical Instruments

Descriptions are presented of high-precision hinge and latch joints that have been co-developed, for application to deployable optical instruments, by NASA Langley Research Center and Nyma/ADF. Page-sized versions of engineering drawings are included in two appendices to describe all mechanical components of both joints. Procedures for assembling the mechanical components of both joints are also presented. The information herein is intended to facilitate the fabrication and assembly of the high-precision hinge and latch joints, and enable the incorporation of these joints into the design of deployable optical instrument systems.

Phelps, James E.↗