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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 271 records · Page 15
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NASA NTRS1994

The beetle Tribolium castaneum has a fushi tarazu homolog expressed in stripes during segmentation

The genetic control of embryonic organization is far better understood for the fruit fly Drosophila melanogaster than for any other metazoan. A gene hierarchy acts during oogenesis and embryogenesis to regulate the establishment of segmentation along the anterior-posterior axis, and homeotic selector genes define developmental commitments within each parasegmental unit delineated. One of the most intensively studied Drosophila segmentation genes is fushi tarazu (ftz), a pair-rule gene expressed in stripes that is important for the establishment of the parasegmental boundaries. Although ftz is flanked by homeotic selector genes conserved throughout the metazoa, there is no evidence that it was part of the ancestral homeotic complex, and it has been unclear when the gene arose and acquired a role in segmentation. We show here that the beetle Tribolium castaneum has a ftz homolog located in its Homeotic complex and expressed in a pair-rule fashion, albeit in a register differing from that of the fly gene. These and other observations demonstrate that a ftz gene preexisted the radiation of holometabolous insects and suggest that it has a role in beetle embryogenesis which differs somewhat from that described in flies.

NASA Discipline Developmental Biology↗
NASA NTRS2008

Defining Constellation Suit Helmet Field of View Requirements Employing a Mission Segment Based Reduction Process

Field of view has always been a design feature paramount to helmet design, and in particular space suit design, where the helmet must provide an adequate field of view for a large range of activities, environments, and body positions. For Project Constellation, a slightly different approach to helmet requirement maturation was utilized; one that was less a direct function of body position and suit pressure and more a function of the mission segment in which the field of view is required. Through taxonimization of various parameters that affect suited FOV, as well as consideration for possible nominal and contingency operations during that mission segment, a reduction process was able to condense the large number of possible outcomes to only six unique field of view angle requirements that still captured all necessary variables without sacrificing fidelity. The specific field of view angles were defined by considering mission segment activities, historical performance of other suits, comparison between similar requirements (pressure visor up versus down, etc.), estimated requirements from other teams for field of view (Orion, Altair, EVA), previous field of view tests, medical data for shirtsleeve field of view performance, and mapping of visual field data to generate 45degree off-axis field of view requirements. Full resolution of several specific field of view angle requirements warranted further work, which consisted of low and medium fidelity field of view testing in the rear entry ISuit and DO27 helmet prototype. This paper serves to document this reduction progress and followup testing employed to write the Constellation requirements for helmet field of view.

McFarland, Shane M.↗
NASA NTRS2009

Arc Second Alignment of International X-Ray Observatory Mirror Segments in a Fixed Structure

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc seconds. These mirror segments are 0.4mm thick, and 200 to 400mm in size, which makes it hard not to impart distortion at the subarc second level. This paper outlines the precise alignment, verification testing, and permanent bonding techniques developed at NASA's Goddard Space Flight Center (GSFC). These techniques are used to overcome the challenge of transferring thin mirror segments from a temporary mount to a fixed structure with arc second alignment and minimal figure distortion. Recent advances in technology development in addition to the automation of several processes have produced significant results. This paper will highlight the recent advances in alignment, testing, and permanent bonding techniques as well as the results they have produced.

Evans, Tyler C.↗
NASA NTRS2010

Large Telescope Segmented Primary Mirror Alignment

A document discusses a broadband (white light) point source, located at the telescope Cassegrain focus, which generates a cone of light limited by the hole in the secondary mirror (SM). It propagates to the aspheric null-mirror, which is optimized to make all the reflected rays to be normal to the primary mirror (PM) upon reflection. PM retro-reflects the rays back through the system for wavefront analysis. The point source and the wavefront analysis subsystems are all located behind the PM. The PM phasing is absolute (white light) and does not involve the SM. A relatively small, aspheric null-mirror located near the PM center of curvature has been designed to deliver the high level of optical wavefront correction. The phasing of the segments is absolute due to the use of a broadband source. The segmented PM is optically aligned independently and separately from the SM alignment. The separation of the PM segments alignment from the PM to the SM, and other telescope optics alignments, may be a significant advantage, eliminating the errors coupling. The point source of this concept is fully cooperative, unlike a star or laser-generated guide-star, providing the necessary brightness for the optimal S/N ratio, the spectral content, and the stable on-axis position. This concept can be implemented in the lab for the PM initial alignment, or made to be a permanent feature of the space-based or groundbased telescope.

Rud, Mayer↗
NASA NTRS2010

Fabrication of Glass Mirror Segments for the International X-Ray Observatory

As the next major X-ray astronomical mission of NASA, ESA, and JAXA, the International X-ray Observatory (IXO) requires a mirror assembly that has an unprecedented effective area and an angular resolution better than all past missions except Chandra. This mirror assembly consists of approximately 15,000 mirror segments, which need to be fabricated, measured, aligned and integrated. In this talk we will present the latest results from our effort of developing an efficient and fast process of making these mirror segments by slumping commercially available glass sheets. We will report on our progress both in terms of perfecting the slumping process as well as the metrology process. In particular, we will discuss what additional work needs to be done to fully facilitate the manufacture of these mirror segments, meeting both budgetary and schedule requirements.

Zhang, William W.↗
NASA NTRS2010

Arc-Second Alignment of International X-Ray Observatory Mirror Segments in a Fixed Structure

The optics for the International X-Ray Observatory (IXO) require alignment and integration of about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arc-seconds. These mirror segments are 0.4 mm thick, and 200 to 400 mm in size, which makes it hard not to impart distortion at the subare- second level. This paper outlines the precise alignment, verification testing, and permanent bonding techniques developed at NASA's Goddard Space Flight Center (GSFC). These techniques are used to overcome the challenge of transferring thin mirror segments from a temporary mount to a fixed structure with arc-second alignment and minimal figure distortion. Recent advances in technology development in addition to the automation of several processes have produced significant results. This paper will highlight the recent advances in alignment, testing, and permanent bonding techniques as well as the results they have produced.

Evans, Tyler C.↗
NASA NTRS2010

Fine alignment of a large segmented mirror

A system for aligning a segmented mirror includes a source of radiation directed along a first axis to the segmented mirror and a beamsplitter removably inserted along the first axis for redirecting radiation from the first axis to a second axis, substantially perpendicular to the first axis. An imaging array is positioned along the second axis for imaging the redirected radiation, and a knife-edge configured for cutting the redirected radiation is serially positioned to occlude and not occlude the redirected radiation, effectively providing a variable radiation pattern detected by the imaging array for aligning the segmented mirror.

Dey, Thomas William↗
NASA NTRS2011

Bonding Thin Mirror Segments Without Distortion for the International X-Ray Observatory

The International X-Ray Observatory (IXO) uses thin glass optics to maximize large effective area and precise low angular resolution. The thin glass mirror segments must be transferred from their fabricated state to a permanent structure without imparting distortion. IXO will incorporate about fourteen thousand thin mirror segments to achieve the mission goal of 3.0 square meters of effective area at 1.25 keV with an angular resolution of five arcseconds. To preserve figure and alignment, the mirror segment must be bonded with sub-micron movement at each corner. Recent advances in technology development have produced significant x-ray test results of a bonded pair of mirrors. Three specific bonding cycles will be described highlighting the improvements in procedure, temperature control, and precision bonding. This paper will highlight the recent advances in alignment and permanent bonding as well as the results they have produced.

Evans, Tyler C.↗
NASA NTRS2006

Improvement in Recursive Hierarchical Segmentation of Data

A further modification has been made in the algorithm and implementing software reported in Modified Recursive Hierarchical Segmentation of Data (GSC- 14681-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 51. That software performs recursive hierarchical segmentation of data having spatial characteristics (e.g., spectral-image data). The output of a prior version of the software contained artifacts, including spurious segmentation-image regions bounded by processing-window edges. The modification for suppressing the artifacts, mentioned in the cited article, was addition of a subroutine that analyzes data in the vicinities of seams to find pairs of regions that tend to lie adjacent to each other on opposite sides of the seams. Within each such pair, pixels in one region that are more similar to pixels in the other region are reassigned to the other region. The present modification provides for a parameter ranging from 0 to 1 for controlling the relative priority of merges between spatially adjacent and spatially non-adjacent regions. At 1, spatially-adjacent-/spatially- non-adjacent-region merges have equal priority. At 0, only spatially-adjacent-region merges (no spectral clustering) are allowed. Between 0 and 1, spatially-adjacent- region merges have priority over spatially- non-adjacent ones.

Tilton, James C.↗
NASA NTRS2006

Using Heaps in Recursive Hierarchical Segmentation of Data

A modification to increase processing speed has been made in the algorithm and implementing software reported in Modified Recursive Hierarchical Segmentation of Data (GSC-14681-1), NASA Tech Briefs, Vol. 30, No. 6 (June 2006), page 51. That software performs recursive hierarchical segmentation of data having spatial characteristics (e.g., spectral-image data). The segmentation process includes an iterative subprocess, in each iteration of which it is necessary to determine a best pair of regions to merge [merges being justified by one or more measure(s) similarity of pixels in the regions]. In the previously reported version of the algorithm and software, the choice of a best pair of regions to merge involved the use of a fully sorted list of regions. That version was computationally inefficient because a fully sorted list is not needed: what is needed is only the identity of the pair of regions characterized by the smallest measure of dissimilarity. The present modification replaces the use of a fully sorted list with the use of data heaps, which are computationally more efficient for performing the required comparisons among dissimilarity measures. The modification includes the incorporation of standard and modified functions for creating and updating data heaps

Tilton, James C.↗
NASA NTRS2005

Measuring Low-Order Aberrations in a Segmented Telescope

The in-focus PSF optimizer (IPO) is an algorithm for use in monitoring and controlling the alignment of the segments of a segmented-mirror astronomical telescope. IPO is so named because it computes wave-front aberrations of the telescope from digitized pointspread functions (PSFs) measured in infocus images. Inasmuch as distant astronomical objects that behave optically as point sources can typically be seen in almost any astronomical image, the main benefit afforded by IPO may be to enable maintenance of mirror-segment alignments without detracting from valuable scientific-observation time. IPO evolved from prescription-retrieval type algorithms. Prescription retrieval uses in-focus and out-of-focus PSFs to infer the state of an imaging optical system. The state, in this context, refers to the positions, orientations, and low-order figure errors of the optical elements in the system. Both prescription- retrieval and IPO use an iterative, nonlinear, least-squares optimizer to compute the optimal state parameters such that a digital computer-generated model image matches the digitized image acquired from the real system. The difference between IPO and prescription- retrieval algorithms is that IPO is specifically designed to utilize infocus images only. Although the restriction to in-focus images limits IPO to calculating only the lowest-order wave front aberrations, it also causes the resulting computation to take much less time because fewer degrees of freedom are included in the optimization process. In the prescription retrieval software developed at JPL, the model images are generated using the ray-trace/physical optics program, MACOS. IPO, on the other hand, uses a linear sensitivity matrix to compute the exit-pupil wave front from the system parameters; the wave front is then converted into a complex pupil field, which is then propagated to the image plane via a fast Fourier transform. This approach is computationally faster and requires less computer memory than is needed for prescription retrieval.

Ohara, Catherine↗
NASA NTRS2012

Magnetic Interface for Segmented Mirror Assembly

Newly developed magnetic devices are used to create an interface between adjacent mirror segments so that once assembled, aligned, and phased, the multiple segments will behave functionally equivalent to a monolithic aperture mirror. One embodiment might be a kinematic interface that is reversible so that any number of segments can be pre-assembled, aligned, and phased to facilitate fabrication operations, and then disassembled and reassembled, aligned, and phased in space for operation. The interface mechanism has sufficient stiffness, force, and stability to maintain phasing. The key to producing an interface is the correlated magnetic surface. While conventional magnets are only constrained in one direction -- the direction defined by their point of contact (they are in contact and cannot get any closer) -- correlated magnets can be designed to have constraints in multiple degrees of freedom. Additionally, correlated magnetic surfaces can be designed to have a limited range of action.

Stahl, H.↗
NASA NTRS2013

Segmented X-Ray Optics for Future Space Telescopes

Lightweight and high resolution mirrors are needed for future space-based X-ray telescopes to achieve advances in high-energy astrophysics. The slumped glass mirror technology in development at NASA GSFC aims to build X-ray mirror modules with an area to mass ratio of approx.17 sq cm/kg at 1 keV and a resolution of 10 arc-sec Half Power Diameter (HPD) or better at an affordable cost. As the technology nears the performance requirements, additional engineering effort is needed to ensure the modules are compatible with space-flight. This paper describes Flight Mirror Assembly (FMA) designs for several X-ray astrophysics missions studied by NASA and defines generic driving requirements and subsequent verification tests necessary to advance technology readiness for mission implementation. The requirement to perform X-ray testing in a horizontal beam, based on the orientation of existing facilities, is particularly burdensome on the mirror technology, necessitating mechanical over-constraint of the mirror segments and stiffening of the modules in order to prevent self-weight deformation errors from dominating the measured performance. This requirement, in turn, drives the mass and complexity of the system while limiting the testable angular resolution. Design options for a vertical X-ray test facility alleviating these issues are explored. An alternate mirror and module design using kinematic constraint of the mirror segments, enabled by a vertical test facility, is proposed. The kinematic mounting concept has significant advantages including potential for higher angular resolution, simplified mirror integration, and relaxed thermal requirements. However, it presents new challenges including low vibration modes and imperfections in kinematic constraint. Implementation concepts overcoming these challenges are described along with preliminary test and analysis results demonstrating the feasibility of kinematically mounting slumped glass mirror segments.

McClelland, Ryan S.↗
NASA NTRS2013

Buckling Design and Analysis of a Payload Fairing One-Sixth Cylindrical Arc-Segment Panel

Design and analysis results are reported for a panel that is a 16th arc-segment of a full 33-ft diameter cylindrical barrel section of a payload fairing structure. Six such panels could be used to construct the fairing barrel, and, as such, compression buckling testing of a 16th arc-segment panel would serve as a validation test of the buckling analyses used to design the fairing panels. In this report, linear and nonlinear buckling analyses have been performed using finite element software for 16th arc-segment panels composed of aluminum honeycomb core with graphiteepoxy composite facesheets and an alternative fiber reinforced foam (FRF) composite sandwich design. The cross sections of both concepts were sized to represent realistic Space Launch Systems (SLS) Payload Fairing panels. Based on shell-based linear buckling analyses, smaller, more manageable buckling test panel dimensions were determined such that the panel would still be expected to buckle with a circumferential (as opposed to column-like) mode with significant separation between the first and second buckling modes. More detailed nonlinear buckling analyses were then conducted for honeycomb panels of various sizes using both Abaqus and ANSYS finite element codes, and for the smaller size panel, a solid-based finite element analysis was conducted. Finally, for the smaller size FRF panel, nonlinear buckling analysis was performed wherein geometric imperfections measured from an actual manufactured FRF were included. It was found that the measured imperfection did not significantly affect the panel's predicted buckling response

composite structures↗
NASA NTRS2016

End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10^-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance. These efforts are combined through integrated modeling, coronagraph evaluations, and Exo-Earth yield calculations to assess the potential performance of the selected architecture. In addition, we discusses the scalability of this architecture to larger apertures and the technological tall poles to enabling it.

Feinberg, Lee↗
NASA NTRS2016

End-to-End Assessment of a Large Aperture Segmented Ultraviolet Optical Infrared (UVOIR) Telescope Architecture

Key challenges of a future large aperture, segmented Ultraviolet Optical Infrared (UVOIR) Telescope capable of performing a spectroscopic survey of hundreds of Exoplanets will be sufficient stability to achieve 10-10 contrast measurements and sufficient throughput and sensitivity for high yield Exo-Earth spectroscopic detection. Our team has collectively assessed an optimized end to end architecture including a high throughput coronagraph capable of working with a segmented telescope, a cost-effective and heritage based stable segmented telescope, a control architecture that minimizes the amount of new technologies, and an Exo-Earth yield assessment to evaluate potential performance.

Feinberg, Lee↗
NASA NTRS2018

Nasa's Launch Communications Ground Segment for the 21st Century Florida Spaceport

The National Aeronautics and Space Administration (NASA) Near Earth Network (NEN) Project is implementing a new launch communications ground segment to provide services for the next generation of human and robotic space exploration systems. It will deliver unique and advanced capabilities to accelerate the transformation of Kennedy Space Center into a multi-user spaceport in cooperation with the United States Air Force (USAF). The project has leveraged commercial technologies and remote operations concepts matured in NASAs orbiting satellite ground systems to achieve dramatic lifecycle cost efficiencies as compared to the space shuttle-era ground segment. The purpose of this paper is to discuss the development history, capabilities and anticipated use cases of the NEN Launch Communications Segment (NEN LCS).The NASA Kennedy Space Center is co-located with the USAF Eastern Launch Range at Cape Canaveral, Florida. The USAF operates two launch communications ground stations, but they are not designed to transmit voice, commands or other data to the launch vehicle or astronauts. The bi-directional uplink-downlink communications responsibility for human missions has historically resided with the Goddard Space Flight Center in Greenbelt, Maryland. Several market analyses and feasibility studies investigating concepts to provide NASAs next generation launch communications services were performed during the Constellation Program prior to its cancellation in 2009, and as part of the Kennedy Space Centers follow-on efforts to transform itself into a 21st century multi-user spaceport. In 2012, the Kennedy Space Center and the USAF 45th Space Wing jointly led a study to analyze the market needs of current and future launch systems and assess the operational deficiencies of the Eastern Range infrastructure. The study team issued several recommendations, two of which ultimately became driving operational capability requirements for the NEN LCS: increased telemetry data rates of at least 20 Mbps, and S-band uplink capability. Additional capabilities identified in the requirements development process include spread spectrum modulation support, LDPC 12 and 78 error correction codes, support for IRIG-106 and CCSDS data formats, automated best source selection, and Space Link Extension (SLE) services for data distribution. The NEN LCS is comprised of two permanent ground stations, the new Kennedy Uplink Station (KUS) and refurbished Ponce de Leon (PDL) station. Both stations are remotely operated from the Global Monitor and Control Center at Wallops Flight Facility. This core architecture is extensible through host-tenant arrangements with the U.S. Air Force and deployable assets, enabling agile, tailored and robust solutions to meet the needs of civil, commercial or military customers. The NEN LCS has three use cases:1.To provide agile, tailored and robust launch communications solutions to Florida spaceport customers2.To provide orbital communications services to near-earth customers 3.To provide an experimental proving ground for Space Mobile Network concepts and technologies The NEN LCS driving mission is to support the bi-directional link with the Orion crew capsule and two 20 Mbps telemetry links from the Space Launch System core stage on Exploration Mission-1, the first integrated flight of NASAs flagship human exploration systems.

Roberts, Christopher J.↗