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At least 847 records · Page 47
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NASA NTRS2018

Light Extinction Tomography for Measurement of Ice Crystals and Other Small Particles

A tomography duct for wind tunnels includes a plurality of light sources and sensors displaced around a support structure. The light sources are cycled and sensor measurements are made from sensors opposite the light sources. Tomographic algorithms are used to determine an extinction map from the sensor measurements. The extinction map provides details about particles in a cross-section of the air flow through the tomography duct.

Bencic, Timothy J.↗
NASA NTRS2018

Advanced Mirror Technology Development (AMTD) II Modal Test of A 1.5 m Glass Slumped Mirror

The Advanced Mirror Technology Development (AMTD) project is in Phase 2 of a multiyear effort initiated in Fiscal Year 2012 to mature toward the next technology readiness level critical technologies required to enable 4-m-or-larger monolithic or segmented ultraviolet, optical, and infrared (UVOIR) space telescope primary-mirror assemblies for general astrophysics and ultra-high-contrast observations of exoplanets. As part of AMTD II, a free-free modal test was performed of a light weighted slumped 1.5 m mirror made of Corning Ultra Low Expansion (ULE®) material. The test article and support structure were suspended via bungee to simulate a free-free environment. Modes were excited by roaming an instrumented modal test hammer and responses were measured. Predicted and measured frequencies are presented as well as Modal Assurance Criteria (MAC) results to compare the mode shapes. The finite element mirror model used for pre-test predictions and posttest comparisons was provided by the mirror vendor, Harris Corporation. The mirror FEM included deformations of the ribs that were a result of the slumping process. Modal test frequencies matched predictions within the 5% target with the exception of one mode and that pair differed by 5.2%. Of the seven modes measured and predicted, four had MAC values meeting the target of ≥ 0.90, one was just under and two were notably below the target.

Knight, J. Brent↗
NASA NTRS2018

Optothermal Stability of Large ULE and Zerodur Mirrors

Marshall Space Flight Center's (MSFC) X-ray and Cryogenic Test Facility (XRCF) has tested the optothermal stability of two low-CTE, large-aperture mirrors in a thermal vacuum chamber. The mirrors deformed from several causes such as: thermal gradients, thermal soaks, coefficient of thermal expansion (CTE) gradients, CTE mismatch, and stiction. This paper focuses on how the aforementioned conditions affected the surface figure of the large optics while in vacuum at temperatures ranging from 230 to 310 K (-43 to 37 ˚C). The presented data, conclusions, and taxonomy are useful for designing mirrors and support structures for telescopes. The data is particularly useful for telescopes that require extreme dimensional stability or telescopes that operate at a temperature far from ambient.

Brooks, Thomas E.↗
NASA NTRS2017

Transformers for Lunar Extreme Environments: Ensuring Long-Term Operations in Regions of Darkness and Low Temperatures: II - Phase

This report shows how solar power could enable robotic operations in permanently shaded regions at lunar poles, to extract water ice and further produce liquid hydrogen and oxygen (LH2/LO2) propellant. The power needs are derived from an Architecture for Human Exploration of Mars based entirely on lunar propellant. The extraction of 10 metric tons of water per day (at 10% water in regolith) requires approx. 0.6 MW thermal power. Additional approx. 2 MW electric power are required to produce 7.5 metric tons of LH2/LO2 propellant per day, as needed by the architecture. To provide power to processing equipment inside Shackleton Crater, optimal locations are determined on the crater rim, from which several reflecting TransFormers (TFs) would redirect sunlight, achieving a combined period of illumination of approx. 99% of the year. A single 40-m diameter reflector could provide up to 1 MW solar power. Inflatable rigidizable tower support structures raise reflectors above ground for better solar exposure. There are trade-offs: e.g., two reflectors at ground level would provide the same combined total illumination as a single tower approx. 100-m tall. Such a TF based on a 100-m tower made with inflatable 2-m beams and 40-m diameter reflectors would be of similar dimensions as an MSL-class rover (approx. 1000 kg, 10 m(exp 3)). A TF-prospector rover combo could be designed and deployed in a Discovery-class mission searching for water. The TransFormers would be nodes of a Lunar Utilities Infrastructure that provides solar power year-round in the proximity of the pole, as well as local data transmission andintermittent direct to earth communications. This infrastructure would be instrumental infacilitating the development of a lunar economy.

fuel↗
NASA NTRS2019

Partnering with Industry: Lessons Learned from the Wide Field Instrument on the Wide Field InfraRed Survey Telescope Mission

Through most of the project formulation prior to Phase A, the Wide Field InfraRed Survey Telescope (WFIRST) project was developed as a Goddard Space Flight Center (GSFC) in house mission with one secondary instrument developed by JPL and an existing telescope donated from elsewhere in the federal government and managed by the original industry vendor. GSFC was responsible for the spacecraft bus, the instrument supporting structure and the Wide Field Instrument (WFI), which provides the primary science for the mission. Shortly before the beginning of Phase A, NASA codified its acquisition strategy for WFIRST to explore a more substantial role for industry in the mission. The project decided to have a large portion of the WFI be co-developed by industry. This paper describes lessons learned and recommendations for bringing potential industry partners into a project at later stages of conceptual design and presents viewpoints from both the vendor and customer on the experience with WFIRST.

Peabody,Hume L.↗
NASA NTRS2019

Advanced Cryogenic Insulation Systems

New materials in recent decades have enabled advances in thermal insulation systems for storage and transfer of cryogens. To preserve the cold and achieve efficient cryogenic systems, a combination of materials, testing, and engineering is required. The total heat leak into any cryogenic assembly is comprised of three main parts: 1) heat leak through the insulation, 2) heat leak through the support structures, and 3) heat leak attributed to piping penetrations and feedthroughs (and their negative effects on the insulation). This "cold triangle" approach provides a basis for evaluating performance benefits of new materials and analyzing the cost effectiveness in overall system design. Provided are thermophysical data for aerogels, aerogel composites, novel multilayered composites, and glass bubbles for standard test conditions of 293 K and 78 K under conditions from high vacuum to ambient pressure. Examples of cryogenic storage tanks show the relative importance of both insulation and structural materials for achieving designs of highest energy efficiency.

Multilayer Insulation↗
NASA NTRS2019

Overview of the Optomechanical Design of the LUVOIR Instruments

The Large Ultraviolet/Optical/Infrared Surveyor (LUVOIR) is a space telescope being submitted for review to the 2020 Decadal Survey in Astronomy and Astrophysics. Its science objectives include both direct imaging and spectral characterization of habitable exoplanets around sun-like stars, the study of planet, star, and galaxy formation, the transfer of matter between different galaxies, and the remote sensing of objects within the Solar System. Two architectures have been designed: a 15 m diameter on-axis telescope (LUVOIR-A) and an 8 m off-axis telescope (LUVOIR-B). This paper discusses the opto-mechanical design of the three LUVOIR instruments: the High Definition Imager (HDI), the LUVOIR UV Multi-object Spectrograph (LUMOS), and the Extreme Coronagraph for Living Planetary Systems (ECLIPS). For both the LUVOIR-A and LUVOIR-B variants of each instrument, optical design specifications are presented including first-order constraints, packaging requirements, and optical performance metrics. These factors are used to illustrate the final design of each instrument and LUVOIR as a whole. In addition to the optical designs, mechanical models are presented for each instrument showing the optical mounts, mechanisms, support structure, etc.

Decadal Study↗
NASA NTRSDate not supplied

Fusion of Test and Analysis: Artemis I Booster to Mobile Launcher Interface Validation

NASA is in the midst of bold and exciting next steps in human exploration and spaceflight. The designs of the new Space Launch System (SLS), the Orion spacecraft and the Exploration Ground Systems (EGS) for vehicle processing and launch are essentially complete and there has been significant progress in manufacturing and assembly of specific hardware for the Artemis I and Artemis II missions. Equally as important, the program level and integrated system level testing and analyses are also well underway to support integrated verification, validation, and Certificate of Flight Readiness (CoFR) for Artemis I. Testing and analysis are key to addressing technical challenges faced by the Artemis missions. Building block approaches are required that provide the right balance between component, element, and/or system level testing that satisfies verification and validation objectives where uncertainties are quantified and minimized. Artemis I is a system of systems that requires a fusion of test and analysis that adeptly characterizes critical interfaces between major program elements. An example of this fusion involves characterizing the interface between the SLS booster and the Mobile Launcher (ML) Vertical Support Post (VSP) interfaces. Proper characterization of this interface represents a number of challenges beginning with the fact that it is a mating of ground support structure in the form of a civil structure to flight hardware. Both sides of the interface are built to different construction standards, but are governed by interface requirements to ensure compatibility when mated. From past program experience, the flexibility at the booster to ML interface is critical in developing accurate prelaunch stacking and cryogenic preloads, squat loads, and pad separation release of preloads and squat loads. This same premise holds for Artemis I. To characterize the asymmetric characteristics at this interface, careful consideration of static forces due to gravity loading with the commensurate effects due to leveling during booster stacking (i.e., spacing and shimming) and nonlinear geometric forces are necessary for inclusion in pre-test assessments. This paper will look at these issues for the upcoming Booster Pull Test in which two boosters will be installed on the ML and one of these boosters will undergo static lateral loading followed afterwards with dynamic excitation into resonance and free-decay. This paper evaluates the booster to ML interface characteristics by characterizing the interface flexibility between the booster aft skirt and the ML VSP interfaces. Furthermore, this paper methodically evaluates the effect of the following on the test outcome: gravitational effects on the booster and ML, the effects of VSP leveling, spacing, and shimming under gravitational loading during booster stacking, the effect of geometric nonlinear follower force due to cg offset as booster is laterally displaced, and the system coupling between the booster under test, ML, and the second booster. Simulated results for a static load pull and dynamic excitation provide insight into the differences in measurement responses when boundary conditions and geometric conditions are included and not included.

Joel W Sills Jr.↗
NASA NTRS2020

An Initial Concept for a JUMP Mating Mechanism

Lunar landers currently under development for crew and cargo missions to the Moon are limited by the available boosters to launch them from Earth. Most landers are being developed for commercial launch vehicles (CLVs) in the Falcon Heavy / Vulcan / New Glenn / Atlas V class, limiting their performance with many lunar surface studies consequently restricted to 5-10 metric ton payloads. The JUMP Lander (Joinable Undercarriage to Maximize Payload) attempts to overcome this limitation by performing an in-space mating, linking multiple landers together. This research provides an initial proof of concept demonstration that two or more CLV-launched lunar landers can be mated in-space to produce a larger lander with greater payload capacity. Multiple rockets have been connected hundreds if not thousands of times in spaceflight history. An example is the space shuttle. The External Tank-Orbiter interface is an example where the 100-ton Orbiter is bolted to the side of the External Tank. This example serves as a concept metaphor for JUMP where a system of bolts is used as the mating system. This paper performs a high-level sizing analysis of the bolt, including the structural connection to each lander and the physical dimensions of the bolt, given the projected lander and payload masses. It sizes the necessary motors to perform the in-space mating and describes the motor to bolt integration. It describes the mounting and translation for the bolt-motor assembly, including structural supports, physical stops, and range of travel. It discusses active-active and active-passive implementations for the mating system and post-mating options to jettison no-longer-needed components of the assembly, including a discussion of benefits of jettisoning or not jettisoning. Finally, forward work for the mating mechanism and overall JUMP Lander concept is described.

Lunar Lander↗
NASA NTRS2020

On the Maximum Stellar Rotation to Form a Black Hole without an Accompanying Luminous Transient

The collapse of a massive star with low angular momentum content is commonly argued to result in the formation of a black hole without an accompanying bright transient. Our goal in this Letter is to understand the flow in and around a newly-formed black hole, involving accretion and rotation, via general relativistic hydrodynamics simulations aimed at studying the conditions under which infalling material can accrete without forming a centrifugally supported structure and, as a result, generate no effective feedback. If the feedback from the black hole is, on the other hand, significant, the collapse would be halted and we suggest that the event is likely to be followed by a bright transient. We find that feedback is only efficient if the specific angular momentum of the infalling material at the innermost stable circular orbit exceeds that of geodesic circular flow at that radius by at least≈20%. We use the results of our simulations to constrain the maximal stellar rotation rates of the disappearing massive progenitors PHL293B-LBV and N6946-BH1, and to provide an estimate of the overall rate of disappearing massive stars. We find that about a few percent of single O-type stars with measured rotational velocities are expected to spin below the critical value before collapse and are thus predicted to vanish without a trace.

Scott C Noble↗
NASA NTRS2004

Inflatable space structures technology development for large radar antennas.

There has been recent interest in inflatable space-structures technology for possible applications on US. Department of Defense (DOD) missions because of the technology's potential for high mechanical-packaging efficiency, variable stowed geometry, and deployment reliability. In recent years, the DOD-sponsored Large Radar Antenna Program (LRA) applied this new technology to a baseline concept: an inflatablehigidizable (lU) perimeter-truss structure supporting a meshhet parabolic-reflector antenna. The program addressed (a) truss concept development, (b) rigidizable materials concepts assessment, (c) meshhet concept selection and integration, and (d) developed potential mechanical-system p erformance estimates. Critical and enabling technologies were validated, especially orbital radiation durable rigidized materials, and high modulus, inflatable-deployablet russ numbers.

Willis, Paul↗
NASA NTRS1994

Economical 10-Meter-Class Ground-Based Receiver for Deep-Space Optical Communications

Modifications to an existing radiofrequency telescope are described which would enable it to operate as an R&D optical receiver terminal for deep-space communications. The low overall cost of the telescope is due to the unique process of fabricating the 10.4 meter primary mirror and its support structure, the lightweight of the primary (10-11 kg/m 2 ), and the requirement that the telescope act only as a photon bucket, which lowers the cost of optically figuring and polishing the mirror. The entrie optical ground terminal facility is estimated to cost approximately $10M to construct.

deep-space↗
NASA NTRS2017

Development of a Turn Key Cryogenic Cooling Module for Space Flight Based on a Commercial Cryocooler

Commercial cryocoolers have significant price and lead time advantages over coolers built exclusively for the space market, but there are many challenges that must be overcome before using a COTS cooler for flight. The initial cost advantage is significantly narrowed by the cost of adapting the COTS cooler for flight. JPL is developing a “turnkey” cryogenic cooling solution based on a commercial cryocooler with the intention that it can become a standard product. The goal is to develop a complete, fully redundant cryogenic cooling solution based on the Thales 9310. The system includes the cooler, brackets to provide mounting and cooling, supporting structures, vibration isolation, thermal straps, thermal switches, and drive electronics. This paper discusses qualification of the various components for flight, including launch vibration and thermal performance testing, as well as a full up testing of the completed assembly.

Ramsey, Perry G.↗
NASA NTRS2017

Development of a Turn Key Cryogenic Cooling Module for Space Flight Based on a Commercial Cryocooler

Commercial cryocoolers have significant price and lead time advantages over coolers built exclusively for the space market, but there are many challenges that must be overcome before using a COTS cooler for flight. The initial cost advantage is significantly narrowed by the cost of adapting the COTS cooler for flight. JPL is developing a “turn key” cryogenic cooling solution based on a commercial cryocooler with the intention that it can become a standard product. The goal is to develop a complete, fully redundant cryogenic cooling solution based on the Thales 9310. The system includes the cooler, brackets to provide mounting and cooling, supporting structures, vibration isolation, thermal straps, thermal switches, and drive electronics. This paper discusses qualification of the various components for flight, including launch vibration and thermal performance testing, as well as a full up testing of the completed assembly.

Ramsey, Perry G.↗
NASA NTRSDate not supplied

Ceramic Heat Pipe for Thermal Management of a High Frequency Inductor

As the power density of electric machines and power electronics continues to increase to meet the demands of more electric aircraft, the thermal management of these devices becomes increasingly important. Ideally, the thermal management solution of the device should have high thermal conductivity and be electrically insulating so that it can be directly integrated with the device in question. Technical ceramics are a class of materials that meet these two requirements. Direct liquid cooling by submerging electric components in a dielectric fluid is an alternate option, but adds system complexity and may incur pumping loss. In this work, the thermal management solution for a high frequency inductor is presented. A conventional wicked heat pipe is designed that is made from a solid ceramic case with a sintered ceramic wick. This heat pipe can provide structural support for the core and windings and is electrically insulating, so it does not incur any additional eddy current losses from the high frequency magnetic fields. It does not require additional pumping power, because conventional wicked heat pipes are passive devices. In this paper, the manufacturing process of the ceramic heat pipe is also presented. It is shown that the sintering of large diameter spherical ceramic particles is difficult due to their high specific surface area and low surface free energy. To overcome this difficulty, a flux material was used to initiate liquid phase sintering. The results of the sintering trials show that for the 120 μm diameter α-Al2O3powder selected for the wick, the combination of 1650°C sintering temperature and the addition of 5 wt% talc sintered the porous matrix together sufficiently for use as a heat pipe wic

High-frequency Inductor↗
NASA NTRSDate not supplied

Ceramic Heat Pipe for Thermal Management of a High Frequency Inductor

As the power density of electric machines and power electronics continues to increase to meet the demands of more electric aircraft, the thermal management of these devices becomes increasingly important. Ideally, the thermal management solution of the device should have high thermal conductivity and be electrically insulating so that it can be directly integrated with the device in question. Technical ceramics are a class of materials that meet these two requirements. Direct liquid cooling by submerging electric components in a dielectric fluid is an alternate option, but adds system complexity and may incur pumping loss. In this work, the thermal management solution for a high frequency inductor is presented. A conventional wicked heat pipe is designed that is made from a solid ceramic case with a sintered ceramic wick. This heat pipe can provide structural support for the core and windings and is electrically insulating, so it does not incur any additional eddy current losses from the high frequency magnetic fields. It does not require additional pumping power, because conventional wicked heat pipes are passive devices. In this paper, the manufacturing process of the ceramic heat pipe is also presented. It is shown that the sintering of large diameter spherical ceramic particles is difficult due to their high specific surface area and low surface free energy. To overcome this difficulty, a flux material was used to initiate liquid phase sintering. The results of the sintering trials show that for the 120 μm diameter α-Al2O3 powder selected for the wick, the combination of 1650°C sintering temperature and the addition of 5 wt% talc sintered the porous matrix together sufficiently for use as a heat pipe wick.

High frequency inductor↗
NASA NTRSDate not supplied

Computational Aerodynamic Analysis in Support of the CRM Tail Cone Thruster Configuration Wind Tunnel Test

NASA’s Advanced Air Transport Technology (AATT) project is breaching the boundaries of aircraft design in pursuit of eco-friendly solutions that are compatible with urban noise comfort levels. Boundary layer ingesting (BLI) propulsion systems promise to reduce fuel burn with additional potential benefits in noise reduction. Type-II BLI systems of the STARC-ABL type are the subject of a test campaign planned for fiscal year 2022 in the National Transonic Facility (NTF), for which a CRM-based model with a retrofitted tail cone thruster (TCT) has been designed. The present work is a precursor to the NTF test, where the 240 cases planned for the experiment were simulated using the Launch, Ascent and Vehicle Aerodynamics (LAVA)computational framework. Solution sensitivity to angle of attack, engine operating conditions, and the presence of the supporting structure (sting) in the wind tunnel test are analyzed in the extensive dataset. The main flow features contributing to the inlet distortion are identified as the vertical tail wake, wing downwash and fuselage upsweep vortices, with the latter two experiencing the greatest sensitivity to angle of attack. Finally, results from an inlet-guide-vane(IGV) design/integration study are presented. The LAVA team and the turbomachinery design team at NASA’s Ames and Glenn Research Centers are collaborating in an effort to reduce flow distortion upstream of the fan by means of integrating an IGV system into the CRM-TCT model. A significant improvement in flow distortion metrics has been achieved since the initial design iteration. Results employing an actuator zone model with realistic radially-varying thrust profiles to simulate first-order fan effects within LAVA are presented.

AATT↗