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At least 1,531 records · Page 85

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NASA NTRS1988

The photons payload, G-494: A learning experience

PHOTONS (Photometric Thermospheric Oxygen Nightglow Study) is an optical remote sensing payload developed for Get Away Special (GAS) flight by the National Research Council of Canada. The device is extremely sensitive and is suitable for making measurements of low intensity, aeronomically generated atmospheric emissions in the nadir and the limb and of Shuttle ram glow. The unit uses a sealed canister and UV transmitting viewing ports. During the flight of STS 61-C, PHOTONS received one hour of operation and aeronomic observations were made. Good diagnostic data were obtained and the science part of the experiment malfunctioned. Post flight inspection revealed that the payload was in perfect working order except for total failure of the photomultiplier detectors. The experiment and the payload are described and the flight results are discussed along with the cause of the malfunctions. It is shown that enough was learned from the flight diagnostic data and about the cause of the malfunction to conclude that the engineering flight was successful and that subsequent flight of the PHOTONS payload will be productive.

Harris, F. R.↗

NASA NTRS1988

A payload for investigating the influence of convection on GaAs crystal growth

A comparative study of the influence of buoyancy driven fluid flow on gallium arsenide (GaAs) crystal growth was undertaken. Crystals will be grown from melts with different degrees of convective flow including growth in the microgravity environment of space. The space growth of GaAs will be performed in a Get Away Special payload. A well insulated growth furnace was designed for both Earth-based and space-based experiments. The self contained payload will carry two such furnaces in addition to a large battery power source and a microprocessor-based control and data acquisition system for regulating the growth process with high precision. The microcomputer will also monitor the growth conditions and measure and record the acceleration in 3 axes.

Bellows, Alfred H.↗

NASA NTRS1988

An advanced microcomputer design for processing of semiconductor materials

In the Get Away Special 330 payload two germanium samples doped with gallium will be processed. The aim of the experiments is to create a planar solid/liquid interface, and to study the breakdown of this interface as the crystal growth rate increases. For the experiments a gradient furnace was designed which is heated by resistive heaters. Cooling is provided by circulating gas from the atmosphere in the cannister through cooling channels in the furnace. The temperature along the sample are measured by platinum/rhodium thermocouples. The furnace is controlled by a microcomputer system, based upon the processor 80C88. A data acquisition system is integrated into the system. In order to synchronize the different actions in time, a multitask manager is used.

Bjoern, L.↗

NASA NTRS1988

Project Explorer takes its second step: GAS-608 in engineering development

An a continuation of its Project Explorer series, the Alabama Space and Rocket Center is sponsoring the development of two additional Get Away Special payloads. Details are given of GAS-608, including descriptions of its six experiments in organic crystal growth, roach eggs, yeast, radish seeds, bacterial morphology, and silicon crystals. A brief summary is also presented of GAS-105 and the Space Camp program for stimulating student first hand participation in space flight studies. GAS-608 will carry six student experiments, which will involve biology, crystal growth, and biochemistry in addition to a centralized package for electronics and power supply.

Kitchens, Philip H.↗

NASA NTRS1988

GAS 450: A space payload for the People Central Coast Student Experimenters

The Get Away Special 450 is described. This discussion includes the peoples efforts, the experiments, lessons learned, and a few powerful positive steps toward community involvement. The following is a list of experiment titles: Guppies in Space; Electrophoresis of Enzymes in Microgravity; Diffusion of Ions in Solution; Space Cement; Bubbles in Space; Small Particle Studies; and Liquid Separation in Microgravity.

Ray, Glen↗

NASA NTRS1988

The NORSTAR Program: Space shuttle to space station

The development of G-325, the first high school student-run space flight project, is updated. An overview is presented of a new international program, which involves students from space station countries who will be utilizing Get Away Special technology to cooperatively develop a prototype experiment for controlling a space station research module environment.

Fortunato, Ronald C.↗

NASA NTRS1988

Lightsats and their attraction to budget oriented Federal agencies

The term Lightsats refers to low volume, low mass, low Earth orbit, satellites suitable for launch from Get Away Special canisters, or as secondary payloads on expendable launch vehicles. New or existing technology that offers potential to improve the safety, capacity and efficiency of the National Airspace System is discussed. The discussion is presented from the point of view of an individual within a government agency who wants to see a new technology to enhance the mission of that agency.

Bonsall, Charles A.↗

NASA NTRS1988

GAS eleven node thermal model (GEM)

The Eleven Node Thermal Model (GEM) of the Get Away Special (GAS) container was originally developed based on the results of thermal tests of the GAS container. The model was then used in the thermal analysis and design of several NASA/GSFC GAS experiments, including the Flight Verification Payload, the Ultraviolet Experiment, and the Capillary Pumped Loop. The model description details the five cu ft container both with and without an insulated end cap. Mass specific heat values are also given so that transient analyses can be performed. A sample problem for each configuration is included as well so that GEM users can verify their computations. The model can be run on most personal computers with a thermal analyzer solution routine.

Butler, Dan↗

NASA NTRS1988

On the dynamic estimation of relative weights for observation and forecast in numerical weather prediction

The problem of merging direct and remotely sensed (indirect) data with forecast data to get an estimate of the present state of the atmosphere for the purpose of numerical weather prediction is examined. To carry out this merging optimally, it is necessary to provide an estimate of the relative weights to be given to the observations and forecast. It is possible to do this dynamically from the information to be merged, if the correlation structure of the errors from the various sources is sufficiently different. Some new statistical approaches to doing this are described, and conditions quantified in which such estimates are likely to be good.

Wahba, Grace↗

NASA NTRS1988

General-aviation's view of progress in the aviation weather system

For all its activity statistics, general-aviation is the most vulnerable to hazardous weather. Of concern to the general aviation industry are: (1) the slow pace of getting units of the Automated Weather Observation System (AWOS) to the field; (2) the efforts of the National Weather Service to withdraw from both the observation and dissemination roles of the aviation weather system; (3) the need for more observation points to improve the accuracy of terminal and area forecasts; (4) the need for improvements in all area forecasts, terminal forecasts, and winds aloft forecasts; (5) slow progress in cockpit weather displays; (6) the erosion of transcribed weather broadcasts (TWEB) and other deficiencies in weather information dissemination; (7) the need to push to make the Direct User Access Terminal (DUAT) a reality; and (7) the need to improve severe weather (thunderstorm) warning systems.

Lundgren, Douglas J.↗

NASA NTRS1987

Threat expert system technology advisor

A prototype expert system was developed to determine the feasibility of using expert system technology to enhance the performance and survivability of helicopter pilots in a combat threat environment while flying NOE (Nap of the Earth) missions. The basis for the concept is the potential of using an Expert System Advisor to reduce the extreme overloading of the pilot who flies NOE mission below treetop level at approximately 40 knots while performing several other functions. The ultimate goal is to develop a Threat Expert System Advisor which provides threat information and advice that are better than even a highly experienced copilot. The results clearly show that the NOE pilot needs all the help in decision aiding and threat situation awareness that he can get. It clearly shows that heuristics are important and that an expert system for combat NOE helicopter missions can be of great help to the pilot in complex threat situations and in making decisions.

Kurrasch, E. R.↗

NASA NTRS1987

Search for ultraviolet Shuttle glow

In January 1986, the Space Shuttle Columbia carried two ultraviolet experiments (UVX) in an attempt to observe very weak diffuse emission from various astronomical sources at wavelengths below 3200 A with moderate spectral resolution. The experiment attested to the feasibility of low cost astronomy from the Space Shuttle using Get Away Special canisters. Emissions from O2, O, and NO were detected and shown to be consistent with an atmospheric origin.

Tennyson, P. D.↗

NASA NTRS1987

Light echoes - Type II supernovae

Type II supernovae (SNs) light curves show a remarkable range of shapes. Data have been collected for the 12 Type II SNs that have light curve information for more than four months past maximum. Contrary to previous reports, it is found that (1) the decay rate after 100 days past maximum varies by almost an order of magnitude and (2) the light curve shapes are not bimodally distributed, but actually form a continuum. In addition, it is found that the extinctions to the SNs are related to the light curve shapes. This implies that the absorbing dust is local to the SNs. The dust is likely to be part of a circumstellar shell emitted by the SN progenitor that Dwek (1983) has used to explain infrared echoes. The optical depth of the shell can get quite large. In such cases, it is found that the photons scattered and delayed by reflection off dust grains will dominate the light curve several months after peak brightness. This 'light echo' offers a straightforward explanation of the diversity of Type II SN light curves.

Schaefer, Bradley E.↗

NASA NTRS1987

Neutron tori and the origin of r-process elements

It is shown here that if an accretion disk gets hotter than a few MeV, nuclei in the infalling matter are dissociated into their constituent neutrons and protons. Neutrons released by dissociation of matter falling at high accretion rates into a black hole or neutron star accumulate in a dense 'neutron torus'. The occurrence of the classical rapid or r-process nucleosynthesis in such a torus is investigated.

Hogan, C. J.↗

NASA NTRS1988

Effect of joint damping and joint nonlinearity on the dynamics of space structures

Analyses of the effect of linear joint characteristics on the vibrations of a free-free, three-joint beam model show that increasing joint damping increases resonant frequencies and increases modal damping but only to the point where the joint gets 'locked up' by damping. This behavior is different from that predicted by modeling joint damping as proportional damping. Nonlinear analyses of the three-joint model with cubic springs at the joints show all the classical single DOF nonlinear response behavior at each resonance of the multiple DOF system: nondoubling of response for a doubling of forcing amplitude, multiple solutions, jump behavior, and resonant frequency shifts. These properties can be concisely quantified by characteristic backbone curves, which show the locus of resonant peaks for increasing forcing amplitude.

Bowden, Mary↗

NASA NTRS1988

The mechanism of intrusion of the Inyo Dike, Long Valley Caldera, California

The dike geometry of the 11-km-long Inyo Dike at the margins of the Long Valley calderas in eastern California is explained here in terms of the interaction between tectonic stresses and local variations in host rock rheology. Relationships between tectonic and magmatic stresses are evaluated, and the magnitude of magmatic pressure at the depth necessary to get the dike to the surface is estimated. The application of the model to other volcanoes is also discussed.

Reches, Zeev↗

NASA NTRS1988

A small solar electric ion propulsion spacecraft for lunar science

A lightweight spacecraft design concept has been developed which employs solar-electric ion propulsion to conduct a lunar science mission. The design relies on off-the-shelf technology to achieve high reliability and near-term launch readiness status. Overall project costs are kept to a minimum through the concentration of mission objectives, as well as through the minimization of payload launch costs by resort to the Space Shuttle's Get-Away Special canister. Attention is given to the spacecraft's instrumentation configuration.

Salazar, R. P.↗

NASA NTRS1988

Trajectory design for a Mars Rover/Sample Return mission

This paper discusses two of the orbit design problems faced in the design of a Mars Rover/Sample Return mission, which is currently being studied at the Jet Propulsion Laboratory. The first is the problem of interplanetary transfer - what is the best trajectory for getting equipment to Mars and a sample back. Several kinds of trajectories are examined before the conclusion is made that straightforward direct transfers are best. The second orbit design problem is what kind of orbit around Mars is best for making high-resolution maps of sites where the rover could land and gather samples, and how can the same orbiter be used as a relay between a rover on Mars and ground stations on Earth. This question is examined in the context of alternate mission options being considered, and the answer depends on the requirements of the particular mission option.

Sweetser, Theodore H.↗