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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 361 records · Page 20

A Preliminary Investigation of the Effect of Bumpers as a Means of Reducing Projectile Penetration

The results of an investigation to determine the effect of bumpers on projectile penetration indicate that for impact velocities up to 12,500 feet per second, the penetration of 0.062-inch-diameter copper projectiles in to aluminum targets can be definitely reduced by using a properly selected bumper spaced a short distance in front of the main target surface. Bumpers and main targets were made of 2024-T4 aluminum alloy, and spherical projectiles made of 0.062-inch-diameter copper were used in all tests.

Funkhouser, John O.↗

Optical modeling of agricultural fields and rough-textured rock and mineral surfaces

Review was made of past models for describing the reflectance and/or emittance properties of agricultural/forestry and geological targets in an effort to select the best theoretical models. An extension of the six parameter Allen-Gayle-Richardson model was chosen as the agricultural plant canopy model. The model is used to predict the bidirectional reflectance of a field crop from known laboratory spectra of crop components and approximate plant geometry. The selected geological model is based on Mie theory and radiative transfer equations, and will assess the effect of textural variations of the spectral emittance of natural rock surfaces.

Suits, G. H.↗

Pointing control for the International Comet Mission

The design of the pointing control system for the proposed International Comet Mission, intended to fly by Comet Halley and rendezvous with Comet Tempel-2 is presented. Following a review of mission objectives and the spacecraft configuration, design constraints on the pointing control system controlling the two-axis gimballed scan platform supporting the science instruments are discussed in relation to the scientific requirements of the mission. The primary design options considered for the pointing control system design for the baseline spacecraft are summarized, and the design selected, which employs a target-referenced, inertially stabilized control system, is described in detail. The four basic modes of operation of the pointing control subsystem (target acquisition, inertial hold, target track and slew) are discussed as they relate to operations at Halley and Tempel-2. It is pointed that the pointing control system design represents a significant advance in the state of the art of pointing controls for planetary missions.

Leblanc, D. R.↗

Astronomical and statistical algorithms used in the Space Telescope guide star selection system

The construction of the Space Telescope Guide Star Catalog from digitized Schmidt survey plates covering the entire sky is described. In order to provide sufficient pointing information, the Guide Star Selection System has to contain a catalog of 20 million guide star candidates in the range of 9.0 to 14.5 visual magnitudes. An image inventory process extracts the relevant object data; after photometric and astrometric calibration the data are screened to arrive at suitable guide star candidates. The selection process for a given target takes into account geometric and photometric parameters of the field, scheduling information, and acquisition probabilities for each guide star pair.

Jenkner, H.↗

Low P sub T hadron-nucleus interactions

The possibility of describing hadron-nucleus (hA) interactions is discussed in terms of a number of independent collisions of the projectile inside the target nucleus. This multiple rescattering may occur on a particle or quark parton level. To investigate the characteristics of hA interactions as a function of antineutrinos advantage is taken of the correlation between the average number antineutrinos of collisions of the projectile inside the nucleus and the number Ng of fast protons ejected from the struck nucleus. The relation antineutrinos vs Ng obtained in antineutrinos was used. For a given target nucleus this allows the selection of interactions occurring at different impact parameters.

Holynski, R.↗

Arcjet component conditions through a multistart test

A low power, dc arcjet thruster was tested for starting reliability using hydrogen-nitrogen mixtures simulating the decomposition products of hydrazine. More than 300 starts were accumulated in phases with extended burn-in periods interlaced. A high degree of flow stabilization was built into the arcjet and the power supply incorporated both rapid current regulation and a high voltage, pulsed starting circuit. A nominal current level of 10 A was maintained throughout the test. Photomicrographs of the cathode tip showed a rapid recession to a steady-state operating geometry. A target of 300 starts was selected, as this represents significantly more than anticipated (150 to 240), in missions of 10 yr or less duration. Weighings showed no apparent mass loss. Some anode erosion was observed, particularly at the entrance to the constrictor. This was attributed to the brief period during startup the arc mode attachment point spends in the high pressure region upstream of the nozzle. Based on the results obtained, startup does not appear to be performance or life limiting for the number of starts typical of operational satellite applications.

Curran, Frank M.↗

Arcjet component conditions through a multistart test

A low power, dc arcjet thruster was tested for starting reliability using hydrogen-nitrogen mixtures simulating the decomposition products of hydrazine. More than 300 starts were accumulated in phases with extended burn-in periods interlaced. A high degree of flow stabilization was built into the arcjet and the power supply incorporated both rapid current regulation and a high voltage, pulsed starting circuit. A nominal current level of 10 A was maintained throughout the test. Photomicrographs of the cathode tip showed a rapid recession to a steady-state operating geometry. A target of 300 starts was selected, as this represents significantly more than anticipated (150 to 240), in missions of 10 yr or less duration. Weighings showed no apparent mass loss. Some anode erosion was observed, particularly at the entrance to the constrictor. This was attributed to the brief period during startup the arc mode attachment point spends in the high pressure region upstream of the nozzle. Based on the results obtained, startup does not appear to be performance or life limiting for the number of starts typical of operational satellite applications.

Curran, Frank M.↗

Atomic data for opacity calculations. XI - The carbon isoelectronic sequence

Close-coupling calculations are carried out for radiative processes in neutral carbon and a number of carbon-like ions; energy levels, oscillator strengths, and photoionization cross sections have been computed for all bound states of the type 2 s(j)2p(k)nl with n not above 10 and 1 not above 3. The R-matrix method is employed to solve the coupled equations with a ten-state eigenfunction expansion for the parent ion C II and an eight-state expansion for the other boron-like target ions. A number of selected results for oscillator strengths are presented and compared with earlier data, as well as for photoionization cross sections with autoionizing resonance structures. Isoelectronic trends are discussed. The present results for the oscillator strengths of C I and N II are found to differ significantly from some earlier theoretical works for a number of transitions. However, the present C I f values are in excellent agreement with recent calculations and experimental results.

Luo, D.↗

LOLA: The lunar operations landing assembly

Because the President of the United States has begun the Space Exploration Initiative (SEI), which entails a manned mission to Mars by the year 2016, it is necessary to use the Moon as a stepping stone to this objective. In support of this mission, unmanned scientific exploration of the Moon will help re-establish man's presence there and will serve as a basis for possible lunar colonization, setting the stage for a manned Mars mission. The lunar landing platform must provide support to its payload in the form of power, communications, and thermal control. The design must be such that cost is held to a minimum, and so that a wide variety of payloads may be used with the lander. The objectives of this mission are (1) to further the SEI by returning to the moon with unmanned scientific experiments, (2) to demonstrate to the public that experimental payload missions are feasible, (3) to provide a common lunar lander platform so select scientific packages could be targeted to specific lunar locales, (4) to enable the lander to be built from off-the-shelf hardware, and (5) to provide first mission launch by 1996.

Abreu, Mike↗

EOS workstation

This final report summarizes the work done from mid-1989 until January 1992 to develop a prototype set of tools for the analysis of EOS-type images. Such images are characterized by great multiplicity and quantity. A single 'snapshot' of EOS-type imagery may contain several hundred component images so that on a particular pixel, one finds multiple gray values. A prototype EOS-sensor, AVIRIS, has 224 gray values at each pixel. The work focused on the ability to utilize very large images and continuously roam through those images, zoom and be able to hold more than one black and white or color image, for example for stereo viewing or for image comparisons. A second focus was the utilization of so-called 'image cubes', where multiple images need to be co-registered and then jointly analyzed, viewed, and manipulated. The target computer platform that was selected was a high-performance graphics superworkstation, Stardent 3000. This particular platform offered many particular graphics tools such as the Application Visualization System (AVS) or Dore, but it missed availability of commercial third-party software for relational data bases, image processing, etc. The project was able to cope with these limitations and a phase-3 activity is currently being negotiated to port the software and enhance it for use with a novel graphics superworkstation to be introduced into the market in the Spring of 1993.

Leberl, Franz↗

Orbital docking system centerline color television camera system test

A series of tests was run to verify that the design of the centerline color television camera (CTVC) system is adequate optically for the STS-71 Space Shuttle Orbiter docking mission with the Mir space station. In each test, a mockup of the Mir consisting of hatch, docking mechanism, and docking target was positioned above the Johnson Space Center's full fuselage trainer, which simulated the Orbiter with a mockup of the external airlock and docking adapter. Test subjects viewed the docking target through the CTVC under 30 different lighting conditions and evaluated target resolution, field of view, light levels, light placement, and methods of target alignment. Test results indicate that the proposed design will provide adequate visibility through the centerline camera for a successful docking, even with a reasonable number of light failures. It is recommended that the flight deck crew have individual switching capability for docking lights to provide maximum shadow management and that centerline lights be retained to deal with light failures and user preferences. Procedures for light management should be developed and target alignment aids should be selected during simulated docking runs.

Mongan, Philip T.↗

Structure of Pseudoknot PK26 Shows 3D Domain Swapping in an RNA

3D domain swapping provides a facile pathway for the evolution of oligomeric proteins and allosteric mechanisms and a means for using monomer-oligomer equilibria to regulate biological activity. The term "3D domain swapping" describes the exchange of identical domains between two protein monomers to create an oligomer. 3D domain swapping has, so far, only been recognized in proteins. In this study, the structure of the pseudoknot PK26 is reported and it is a clear example of 3D domain swapping in RNA. PK26 was chosen for study because RNA pseudoknots are required structures in several biological processes and they arise frequently in in vitro selection experiments directed against protein targets. PK26 specifically inhibits HIV-1 reverse transcriptase with nanomolar affinity. We have now determined the 3.1 A resolution crystal structure of PK26 and find that it forms a 3D domain swapped dimer. PK26 shows extensive base pairing between and within strands. Formation of the dimer requires the linker region between the pseudoknot folds to adopt a unique conformation that allows a base within a helical stem to skip one base in the stacking register. Rearrangement of the linker would permit a monomeric pseudoknot to form. This structure shows how RNA can use 3D domain swapping to build large scale oligomers like the putative hexamer in the packaging RNA of bacteriophage Phi29.

Lietzke, Susan E↗

Novel Receptor-Based Countermeasures to Microgravity-Induced Bone Loss

The biological actions mediated by the estrogen receptor (ER), vitamin D receptor (VDR) and Ca(sup 2+) (sub o) -sensing receptor (CaR) play key roles in the normal control of bone growth and skeletal turnover that is necessary for skeletal health. These receptors act by controlling the differentiation and/or function of osteoblasts and osteoclasts, and other cell types within the bone and bone marrow microenvironment. The appropriate use of selective ER modulators (SERMS) which target bone, vitamin D analogs that favor bone formation relative to resorption, and CaR agonists may both stimulate osteoblastogenesis and inhibit osteoclastogenesis and the function of mature osteoclasts, should make it possible to prevent the reduction in bone formation and increase in bone resorption that normally contribute to the bone loss induced by weightlessness. Indeed, there may be synergistic interactions among these receptors that enhance the actions of any one used alone. Therefore, we proposed to: 1) assess the in vitro ability of novel ER, VDR and CaR agonists, alone or in combination, to modulate osteoblastogenesis and mature osteoblast function under conditions of 1g and simulated microgravity; 2) assess the in vitro ability of novel ER, VDR and CaR agonists, alone or in combination, to modulate osteoclastogenesis and bone resorption under conditions of lg and simulated microgravity; and 3) carry out baseline studies on the skeletal localization of the CaR in normal rat bone as well as the in vivo actions of our novel ER- and VDR-based therapeutics in the rat in preparation for their use, alone or in combination, in well-established ground-based models of microgravity and eventually in space flight.

OMalley, Bert W.↗

Engineering Documentation and Data Control

Mississippi Space Services (MSS) the facility services contractor for NASA's John C. Stennis Space Center (SSC), is utilizing technology to improve engineering documentation and data control. Two identified improvement areas, labor intensive documentation research and outdated drafting standards, were targeted as top priority. MSS selected AutoManager(R) WorkFlow from Cyco software to manage engineering documentation. The software is currently installed on over 150 desctops. The outdated SSC drafting standard was written for pre-CADD drafting methods, in other words, board drafting. Implementation of COTS software solutions to manage engineering documentation and update the drafting standard resulted in significant increases in productivity by reducing the time spent searching for documents.

Matteson, Michael J.↗

Pancam Imaging of the Mars Exploration Rover Landing Sites in Gusev Crater and Meridiani Planum

The Mars Exploration Rovers carry four Panoramic Camera (Pancam) instruments (two per rover) that have obtained high resolution multispectral and stereoscopic images for studies of the geology, mineralogy, and surface and atmospheric physical properties at both rover landing sites. The Pancams are also providing significant mission support measurements for the rovers, including Sun-finding for rover navigation, hazard identification and digital terrain modeling to help guide long-term rover traverse decisions, high resolution imaging to help guide the selection of in situ sampling targets, and acquisition of education and public outreach imaging products.

Bell, J. F., III↗

The Training Process of the Organization Development and Training Office

The Organization Development and Training Office provides training and development opportunities to employees at NASA Glenn Research Center, as a division of the Office of Human Resources and Workforce Planning. Center-wide required trainings, new employee trainings, workshops and career development programs are organized by the OD&TO staff. They also arrange all academic, non-academic, headquarters, fellowship and learning center sponsored courses. They also service organizations wishing to work more effectively by facilitating teambuilding exercises. Equal Opportunity programs and upward mobility programs such as the STEP and GO programs for administrative staff. In working with my mentor I am very involved with Cuyahoga Community College classes, mandatory supervisory training and administrative staff workshops. My largest tasks are in the secretarial training category. The Supporting Organizations And Relationships workshop for administrative personnel, commonly known as SOAR, began last year and continued this summer with follow-up workshops. Months before a workshop or class is brought to Glenn, a need has to be realized. In this case, administrative staff did not feel they had an opportunity to receive relevant training and develop skills through teambuilding, networking and communication. A Statement of work is then created as several companies are contacted about providing the training. After the company best suited to meet the target group s needs is selected, the course is announced with an outline of all pertinent information. A reservation for a facility is made and applications or nominations, depending on the announcement s guidelines, are received from interested employees. Confirmations are sent to participants and final preparations are made but there are still several concluding steps. A training office staff member also assists the facilitator with setting up the facility and introducing the class. After the class, participants evaluations are read and summarized to determine the effectiveness of the class and instructor. In addition to the SOAR workshops, I have several projects and daily tasks to complete. Coding training applications, which require me to be familiar with Glenn s budgetary allocations and policies on training, is an ongoing process. It also requires verifying information reported by an employee via her C-478 form, more commonly known as the training application. I am also the point of contact for the Cuyahoga Community College Advising Sessions held here at NASA Glenn which involves coordinating counselors visits with employees schedules. Two databases had to be created. The first database holds information on administrative staff, and the other tracks supervisors training histories. Through these assignments I gained experience in Microsoft Access 2002 and spreadsheet creation, communicating with co-workers, and successfully facilitating a training to serve specific purposes. With trainings and evaluations to assessment them, the Organization Development and Training Office can assure a quality product and continued customer satisfaction.

Johnson, Melissa S.↗

The WIRED Survey. IV. New Dust Disks from the McCook & Sion White Dwarf Catalog

We have compiled photometric data from the Wide-field Infrared Survey Explorer All Sky Survey and other archival sources for the more than 2200 objects in the original McCook & Sion Catalog of Spectroscopically Identified White Dwarfs. We applied color-selection criteria to identify 28 targets whose infrared spectral energy distributions depart from the expectation for the white dwarf photosphere alone. Seven of these are previously known white dwarfs with circumstellar dust disks, five are known central stars of planetary nebulae, and six were excluded for being known binaries or having possible contamination of their infrared photometry. We fit white dwarf models to the spectral energy distributions of the remaining ten targets, and find seven new candidates with infrared excess suggesting the presence of a circumstellar dust disk. We compare the model dust disk properties for these new candidates with a comprehensive compilation of previously published parameters for known white dwarfs with dust disks. It is possible that the current census of white dwarfs with dust disks that produce an excess detectable at K-band and shorter wavelengths is close to complete for the entire sample of known WDs to the detection limits of existing near-IR all-sky surveys. The white dwarf dust disk candidates now being found using longer wavelength infrared data are drawn from a previously underrepresented region of parameter space, in which the dust disks are overall cooler, narrower in radial extent, and/or contain fewer emitting grains.

Dwarf↗

Assessment of the Spectral Stability of Libya 4, Libya 1, and Mauritania 2 Sites Using Earth Observing One Hyperion

The objective of this paper is to formulate a methodology to assess the spectral stability of the Libya 4, Libya 1, and Mauritania 2 pseudo-invariant calibration sites (PICS) using Earth Observing One (EO-1) Hyperion sensor. All the available Hyperion collections, downloaded from the Earth Explorer website, were utilized for the three PICS. In each site, a reference spectrum is selected at a specific day in the vicinity of the region of interest (ROI) defined by Committee on Earth Observation Satellites (CEOS). A series of ROIs are predefined in the along-track direction with 196 spectral top-of-atmosphere reflectance values in each ROI. Based on the reference ROI spectrum, the spectral stability of these ROIs is evaluated by average deviations (ADs) and spectral angle mapper (SAM) methods in the specific ranges of time and geo-spatial locations. Time and ROI location-dependent SAM and AD results are very stable within +/- 2 deg and +/-1.7% of 1sigma standard deviations. Consequently, the Libya 4, Mauritania 2, and Libya 1 CEOS selected PICS are spectrally stable targets within the time and spatial swath ranges of the Hyperion collections.

average deviation↗