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At least 631 records · Page 35

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NASA NTRS1982

Scale-free models of galaxies. II - A complete survey of orbits

A complete set of orbits starting at over 400 distinct points spread out in the phase space of an oblate scale-free potential is investigated. Each orbit is followed for a time that corresponds to a Hubble time in a realistic galaxy potential suitable for an E5 or E6 galaxy. It is noted that none of the orbits in the survey is ergodic. All of the survey orbits are regular, visiting a region at least one dimension smaller than expected from the classical integrals of motion. Thus, for all practical purposes, they have an extra nonclassical isolating integral. Approximately 95% of the survey orbits are box orbits, the rest being pipes (formerly tubes). The survey exposes an ambiguity in the original classification scheme for orbits, which, it is noted, can be resolved on the basis of the topology of an orbit's surface of section. Nevertheless, the distinction between high order very convoluted pipes and boxes is probably artificial for practical purposes.

Richstone, D. O.↗

NASA NTRS1981

Optical studies of X-ray sources with the MASCOT - A charge-coupled device /CCD/-based astronomical instrument

The performance levels achieved by the MASCOT (MIT Astronomical Spectrometer/Camera for Optical Telescopes) on the 1.3-m telescope at the McGraw-Hill observatory in March 1981 are discussed along with preliminary data obtained in searches for optical counterparts to four 'empty-field' X-ray sources. In the W band (4000-7000 A), the MASCOT achieved a sky-limited sensitivity of +24.4 mag per sq arcsec in an 1800 s integration. The ability to flatten pictures to a level consistent with (sky + source) photon statistics and readout noise was demonstrated. For the four sources observed, an optical counterpart was established for one source (1413+13) based on positional coincidence (better than 1.8 arcsec), four possible candidates were detected in the error box of another source (1009?35) and upper sensitivity limits were established for optical counterparts in the error boxes for the other two sources (0920+39 and 0931-11).

Ricker, G. R.↗

NASA NTRS1983

Focal-Plane-Array Optical Proximity Sensors

Objects detected at beam axis intersections. Group of light sources or detectors is mounted in box at focal plane of lens. Box can therefore illuminate or view several axes, each corresponding to source or detector of group. Proximity sensing system developed to trigger braking system of automatically controlled car.

Johnston, A. R.↗

NASA NTRS1983

OSS-1/contamination monitor

A 20-cm high, 18-cm wide, and 30-cm long (8x7x12 inch) box weighing about 7 kg (15 lbs) and consuming about 7 watts of power was carried on the OSS-1 pallet to monitor the mass build-up or accretion of condensible, volatile materials on surfaces in the shuttle bay during all phases of ascent, on-orbit, and descent. Passively thermally controlled, the box holds two witness samples and four actively temperature controlled quartz crystal microbalances (TQCM) whose temperature can vary from -60 C to +80 C. Graphs show the accretion indicated by the TQCM during the launch and early orbital phase. Conditions during tail to the Sun, nose to the Sun, and bay to the Sun attitudes of the shuttle during STS-3 are reflected in temperatures indicated by the OSS-1 thermistor. These temperatures influence outgassing rates of various materials as well as measurements made by the contamination monitor package. The parameters that bear on TQCM measurements data are shown in graphs and discussed.

Kruger, R.↗

NASA NTRS1983

Autonomous navigation using lunar beacons

The concept of using lunar beacon signal transmission for on-board navigation for earth satellites and near-earth spacecraft is described. The system would require powerful transmitters on the earth-side of the moon's surface and black box receivers with antennae and microprocessors placed on board spacecraft for autonomous navigation. Spacecraft navigation requires three position and three velocity elements to establish location coordinates. Two beacons could be soft-landed on the lunar surface at the limits of allowable separation and each would transmit a wide-beam signal with cones reaching GEO heights and be strong enough to be received by small antennae in near-earth orbit. The black box processor would perform on-board computation with one-way Doppler/range data and dynamical models. Alternatively, GEO satellites such as the GPS or TDRSS spacecraft can be used with interferometric techniques to provide decimeter-level accuracy for aircraft navigation.

Khatib, A. R.↗

NASA NTRS1983

X-ray emission from the Pleiades cluster

The detection and identification of H0344+24, a new X-ray source located in the Pleiades cluster, is reported, based on observations made with HEAO A-2 low-energy detector 1 in the 0.15-3.0-keV energy band in August, 1977. The 90-percent-confidence error box for the new source is centered at 03 h 44.1 min right ascension (1950), near the center star of the 500-star Pleiades cluster, 25-eta-Tau. Since no likely galactic or extragalactic source of X-rays was found in a catalog search of the error-box region, identification of the source with the Pleiades cluster is considered secure. X-ray luminosity of the source is calculated to be about 10 to the 32nd ergs/sec, based on a distance of 125 pc. The X-ray characteristics of the Pleiades stars are discussed, and it is concluded that H0344+24 can best be explained as the integrated X-ray emission of all the B and F stars in the cluster.

Agrawal, P. C.↗

NASA NTRS1983

Integrated airframe/propulsion control system architectures (IAPSA) study

Three integrated airframe/propulsion control system (ACS) architectures have been developed and are discussed. The baseline is a state of the art design which integrates autonomous propusion control and airframe flight control systems. Two alternate ACSs for the 1990s using emerging technologies were developed and are compared with each other and the baseline. One of these, designated D/D, uses parallel distributed processing, while the other, designated C/D, centralizes the processing into two centrally located redundant electronics complex. The C/D system locates all redundant computing elements and interfacing electronics in two boxes with optical sensor and actuation devices optically connected to the two boxes. Evaluation reveals the C/D architecture to be better than the other two in five of ten categories; D/D is superior in only two of the ten.

Stern,, A. d.↗

NASA NTRS1984

Adaptive microwave reflector

As an interim step in going to the 100-meter reflector that was evaluated, a 5-meter reflector is proposed to test the electrostatic concept under space conditions. Some of the issues which require the space environment for evaluation are the following questions: Can deployment of a box ring structure with a thin film reflector attached be manually deployed? In the absence of humidity, can a 0.3-mil aluminized Kapton film reflector be formed by the electrostatic process suitable for antenna applications? Can the photogrammetric process be used to evaluate the reflector surface with pictures taken from the payload handling station? Can the space charging effect be evaluated with the 5-meter reflector attached to the Shuttle? Does the outgassing of moisture from 0.3-mil Kapton film affect its reflector capability? A box ring truss support structure and an automatic sequence deployment system are discussed.

Goslee, J. W.↗

NASA NTRS1984

The Solid Model Geometry Generator (SMGG)

The Solid Model Geometry Generator (SMGG) system provides the capacity to model complex solid objects through the composition of primitive parts. The parts are specified through input of dimension and orientation parameters. The parts may later be edited, the model may be displayed (through a variety of display options), and the resulting geometry formatted for subsequent analysis. The SMGG system was originally constructed for use in the preliminary stages of space station and other spacecraft design. Because the system models a design through the use of basic shapes common to many solid objects and provides limited capabilities for producing irregularly shaped parts, it can be used for a variety of applications. Currently, seven primitive parts may be specified and produced through SMGG. These include boxes, spheres, cones, paraboloids, tori, and translationally or rotationally swept parts. Each part may be specified by the user through input of basic part dimensions and a local orientation. For example, a box is specified by its length, width, height and orientation in space (rotation, translation, and scaling).

Jones, K. H.↗

NASA NTRS1984

Quantitative and experimental modelling of sapping networks

Development of drainage networks by erosion by emergent groundwater (sapping) is being modelled by a combination of laboratory experiments and theoretical modelling. Miniature drainage networks formed in fine-grained sediments share many morphologic characteristics of Martian and terrestrial networks suspected to be formed by sapping processes. A larger and better instrumented sapping box was constructed to further explore the processes of sapping and the morphology of resulting networks. The experiments to be conducted in the sapping box will investigate the roles of several factors in controlling network morphology. The mechanics of sapping of fine-grained sediments were investigated in experiments in a two-dimensional sapping chamber and through development of a theoretical model. Results of extensive tests on sapping erosion of fine-grained, cohesionless sediment were analyzed with a theoretical model of the mechanics of sapping erosion and transport.

Howard, A. D.↗

NASA NTRS1984

Effect of space exposure of some epoxy matrix composites on their thermal expansion and mechanical properties (A0138-8)

This experiment has three objectives. The first and main objective is to detect a possible variation in the coefficient of thermal expansion of composite samples during a 1-year exposure to the near-Earth orbital environment. A second objective is to detect a possible change in the mechanical integrity of composite products, both simple elements and honeycomb sandwich assemblies. A third objective is to compare the behavior of two epoxy resins commonly used in space structural production. The experimental approach is to passively expose samples of epoxy matrix composite materials to the space environment and to compare preflight and postflight measurements of mechanical properties. The experiment will be located in one of the three FRECOPA (French cooperative payload) boxes in a 12-in.-deep peripheral tray that contains nine other experiments from France. The FRECOPA box will protect the samples from contamination during the launch and reentry phases of the mission. The coefficients of thermal expansion are measured on Earth before and after space exposure.

Elberg, R.↗

NASA NTRS1984

Research in the design of high-performance reconfigurable systems

An initial design for the Bit Processor (BP) referred to in prior reports as the Processing Element or PE has been completed. Eight BP's, together with their supporting random-access memory, a 64 k x 9 ROM to perform addition, routing logic, and some additional logic, constitute the components of a single stage. An initial stage design is given. Stages may be combined to perform high-speed fixed or floating point arithmetic. Stages can be configured into a range of arithmetic modules that includes bit-serial one or two-dimensional arrays; one or two dimensional arrays fixed or floating point processors; and specialized uniprocessors, such as long-word arithmetic units. One to eight BP's represent a likely initial chip level. The Stage would then correspond to a first-level pluggable module. As both this project and VLSI CAD/CAM progress, however, it is expected that the chip level would migrate upward to the stage and, perhaps, ultimately the box level. The BP RAM, consisting of two banks, holds only operands and indices. Programs are at the box (high-level function) and system level. At the system level initial effort has been concentrated on specifying the tools needed to evaluate design alternatives.

Slotnick, D. L.↗

NASA NTRS1983

Large array VLSI filter

A 35 by 35 element pipelined convolutional kernel is being fabricated using VLSI chips, each containing a 5 by 1 segment of the kernel. Three levels of printed circuitry are used: the first level is used for the VLSI chips, the second level connects seven chips together on one platform, and the third level connects seven platforms with associated delay lines, all fitting on one board. Therefore, on each board there are seven rows of the kernel containing 245 multipliers and adders, and five such boards complete the kernel array. Each multiplier accepts an 8 bit picture element which is multiplied by a 16 bit weight. A truncated 22 bit product is added to a previously stored product sum and the results are shifted to the following multiplier as the next picture element is read in. The multiplier uses a modified Booth algorithm to reduce the number of shift add operations nearly in half. The filter box is presently configured as an ancillary box to a VAX 11/780, but can be connected to essentially any CPU. The I/O bandwidth is easily compatible with most CPU devices.

Nathan, R.↗

NASA NTRS1982

Advanced manufacturing development of a composite empennage component for L-1011 aircraft

This is the final report of technical work conducted during the fourth phase of a multiphase program having the objective of the design, development and flight evaluation of an advanced composite empennage component manufactured in a production environment at a cost competitive with those of its metal counterpart, and at a weight savings of at least 20 percent. The empennage component selected for this program is the vertical fin box of the L-1011 aircraft. The box structure extends from the fuselage production joint to the tip rib and includes front and rear spars. During Phase 4 of the program, production quality tooling was designed and manufactured to produce three sets of covers, ribs, spars, miscellaneous parts, and subassemblies to assemble three complete ACVF units. Recurring and nonrecurring cost data were compiled and documented in the updated producibility/design to cost plan. Nondestruct inspections, quality control tests, and quality acceptance tests were performed in accordance with the quality assurance plan and the structural integrity control plan. Records were maintained to provide traceability of material and parts throughout the manufacturing development phase. It was also determined that additional tooling would not be required to support the current and projected L-1011 production rate.

Alva, T.↗

NASA NTRS1985

Mapping Structures Characteristic of the Highland Boundary Scarp on Mars

In an effort to shed some light on the processes which have produced the highlands/lowlands boundary scrap on Mars, the global distributions of knobby terrain, detached and separated blocks and mesas, and craters larger than 10 km diameter were mapped. These data were represented as fractional areal percentages of the sample box, which is 2.5 deg high (latitude) along north-south profiles every 5 deg in longitude. The fractional area of crater interiors provides a way of quantitatively characterizing the boundary between cratered highlands and relatively uncratered plains. In the vicinity of the nomimal scarp there is generally good agreement between the dropoff in fractional area of craters and a drop-off in topography. Contoured versions of the fractional area of crater interiors, even at the low resolution imposed by the sample box, show good agreement with the geologic mapping. The most northerly occurrence of detached plateaus and knobby terrain were located in order to test the plausibility of the hypothesis that much of the present day highland boundary scrap is due to southward migration of a former boundary.

Frey, H.↗

NASA NTRS1985

A Description of the 64-meter Antenna Elevation Drive Gears and Their Strange Wear

The Deep Space Station (DSS) 64-m antenna elevation axis drive is executed by torquing two bull gears, concentric to the elevation axis, with the output pinions of four gear boxes. These gear boxes have functioned well during the 18 and 11 years, respectively, that the DSS 14, and the DSS 43 and DSS 63 antennas have been in service. A strange wear pattern gradually developed on the bull gears and driving pinions of all three antennas. These patterns were well developed after 8 years and apparently are intensifying in all instances. The elevation drive gears are described and their wear is compared to the wear of other antenna drive gears. The comparison is perplexing and satisfying explanations have not yet been made.

Mcginness, H. D.↗

NASA NTRS1985

Charge and energy dependence of the residence time of cosmic ray nuclei below 15 GeV/nucleon

The relative abundance of nuclear species measured in cosmic rays at Earth has often been interpreted with the simple leaky box model. For this model to be consistent an essential requirement is that the escape length does not depend on the nuclear species. The discrepancy between escape length values derived from iron secondaries and from the B/C ratio was identified by Garcia-Munoz and his co-workers using a large amount of experimental data. Ormes and Protheroe found a similar trend in the HEAO data although they questioned its significance against uncertainties. They also showed that the change in the B/C ratio values implies a decrease of the residence time of cosmic rays at low energies in conflict with the diffusive convective picture. These conclusions crucially depend on the partial cross section values and their uncertainties. Recently new accurate cross sections of key importance for propagation calculations have been measured. Their statistical uncertainties are often better than 4% and their values significantly different from those previously accepted. Here, these new cross sections are used to compare the observed B/C+O and (Sc to Cr)/Fe ratio to those predicted with the simple leaky box model.

Soutoul, A.↗

NASA NTRS1985

Spectral shape variation of interstellar electrons at high energies

The high energy electron spectrum analysis has shown that the electron intensity inside the H2 cloud region, or in a spiral arm, should be much lower than that outside it and the observed electron energy spectrum should flatten again at about 1 TeV. In the framework of the leady box model the recently established rigidity dependence of the escape pathlength of cosmic rays would predict a high energy electron spectrum which is flatter than the observed one. This divergence is explained by assuming that the leaky box model can only apply to cosmic ray heavy nuclei, and light nuclei and electrons in cosmic rays may have different behaviors in the interstellar propagation. Therefore, the measured data on high energy electrons should be analyzed based on the proposed nonuniform galactic disk (NUGD) mode.

Tan, L. C.↗