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At least 937 records · Page 52

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NASA NTRSDate not supplied

Validation of Universal Cryogenic Flow Boiling Correlations in Thermal Desktop for Liquid Hydrogen

Developing accurate models of two-phase cryogenic flow will reduce risk and reduce margins for future NASA vehicles such as the Nuclear Thermal Propulsion (NTP) system. Currently there is a need for more accurate, direct cryogenic data-anchored models for various boiling and two-phase phenomena. The focus of the current work is on modeling steady state cryogenic flow boiling in the transfer line that connects a propellant storage tank to an engine or customer receiver tank. This paper presents Thermal Desktop model validation results against several historical liquid hydrogen (LH2) heated tube experiments that cover a wide range of inlet conditions, mass flux, and heat flux. New universal cryogenic flow boiling correlations were recently developed and anchored to the largest cryogenic flow boiling database assembled in the world to-date. The new universal correlations are patched together and implemented into Thermal Desktop to compare model performance against the built-in flow boiling correlations. Axial wall temperature predictions as a function of preponderant parameters like heat flux, mass flux, inlet pressure, inlet quality, tube diameter, etc. using the two sets of flow boiling correlations are compared against the experimental data. Overall, the Thermal Desktop model with the new universal cryogenic flow boiling correlations demonstrates an improvement in predictive performance over the Thermal Desktop model using built-in correlations for both wall temperature and location of critical heat flux compared to the data for LH2 flow boiling in heated tubes.

cryogenic propellant transfer↗

NASA NTRS2025

Lyotropic Liquid Crystalline Phase Behavior of Boron Nitride Nanotube Aqueous Dispersions

Boron nitride nanotubes (BNNTs) are gaining significant interest due to their outstanding mechanical and thermal properties, as well as their potential to serve as a model nanorod system. Processing BNNT liquid crystalline (LC) dispersions enables precise control over BNNT orientation in macroscopic assemblies, while their low absorption in the visible spectrum facilitates studying LCs at exceptionally high concentrations. Here, we investigate the behavior of BNNTs in aqueous solutions stabilized by the surfactant sodium deoxycholate (SDC), examining the effect of BNNT purity and BNNT−SDC concentrations on lyotropic LC formation. We disperse up to 15wt% BNNT in SDC solutions and use polarized light microscopy to detail the transition from an isotropic state to a biphasic regime, where isotropic and nematic domains coexist due to phase separation, to a single fully nematic phase. Cryogenic electron microscopy provides direct evidence of BNNT alignment within nematic domains. Our results show that enhanced depletion-induced attractions, driven by increased surfactant concentration, lower the threshold concentration of BNNT required to form nematic domains. In contrast, low surfactant concentrations relative to BNNT result in insufficiently coated nanotube surfaces, leading to poor dispersions and BNNT aggregation. Additionally, we fabricate well-aligned BNNT films from aqueous LC dispersions. Our findings advance the understanding of BNNT LCs, offering insight into controlling their orientation and highlighting their potential for high-performance materials.

Joe Khoury↗

NASA NTRS1982

Development status of the small community solar power system

The development status and test results for the Small Community Solar Thermal Power Experiment are presented. Activities on the phase 2 power module development effort are presented with emphasis on the receiver, the plant control subsystem, and the energy transport subsystem. The components include a single prototype power module consisting of a parabolic dish concentrator, a power conversion assembly (PCA), and a multiple-module plant control subsystem. The PCA consists of a cavity receiver coupled to an organic Rankine cycle engine-alternator unit defined as the power conversion subsystem; the PCA is mounted at the focus of a parabolic dish concentrator. At a solar insolation of 100 W/sq m and ambient temperature of 28 C (82 F), the power module produces approximately 20 kW of 3-phase, 3 kHz ac power, depending on the concentrator employed. A ground-mounted rectifier to the central collection site where it is supplied directly to the common dc bus which collects the power from all modules in the plant.

Pons, R. L.↗

NASA NTRS1998

The Effects of Ground and Space Processing on the Properties of Organic, Polymeric, and Colloidal Materials

In recent years, a great deal of interest has been directed toward the use of organic materials in the development of high-efficiency optoelectronic and phototonic devices. There is a myriad of possibilities among organic materials which allow flexibility in the design of unique structures with a variety of functional groups. The use of nonlinear optical (NLO) organic materials as thin film wave-guides allows full exploitation of their desirable qualifies by permitting long interaction lengths and large susceptibilities allowing modest power input. There are several methods in use to prepare thin films such as Langmuir-Blodgett (LB) and self-assembly techniques, vapor deposition, growth from sheared solution or melt, and melt growth between glass plates. Organic-based materials have many features that make them desirable for use in optical devices, such as high second-and third-order nonlinearity, flexibility of molecular design, and damage resistance to optical radiation. However, their use in devices has been hindered by processing difficulties for crystals and thin films. We discuss the potential role of microgravity processing of a few organic and polymeric materials. It is of interest to note how materials with second-and third-order NLO behavior may be improved in a diffusion-limited environment and ways in which convection may be detrimental to these materials. We focus our discussion on third-order materials for all-optical switching, and second-order materials for frequency conversion and electrooptics. The goal of minimizing optical loss obviously depends on processing methods. For solution-based processes, such as solution crystal growth and solution photopolymerization, it is well known that thermal and solutal density gradients can initiate buoyancy-driven convection. Resultant fluid flows can affect transport of material to and from growth interfaces and become manifest in the morphology and homogeneity of the growing film or crystal. Likewise, buoyancy-driven convection can hinder production of defect-free, high-quality crystals or films during crystal and film growth by vapor deposition.

Frazier, Donald O.↗

NASA NTRS1996

High Temperature Superconducting Magnets with Active Control for Attraction Levitation Transport Applications

A research program, involving 3 British universities, directed at quantifying the controllability of High Temperature Superconducting (HTS) magnets for use in attraction levitation transport systems will be described. The work includes measurement of loss mechanisms for iron cored HTS magnets which need to produce a flux density of approx. 1 tesla in the airgap between the magnet poles and a ferromagnetic rail. This flux density needs to be maintained and this is done by introducing small variations of the magnet current using a feedback loop, at frequencies up to 10 Hz to compensate for load changes, track variation etc. The test magnet assemblies constructed so far will be described and the studies and modelling of designs for a practical levitation demonstrator (using commercially obtained HTS tape) will be discussed with particular emphasis on how the field distribution and its components, e.g., the component vector normal to the broad face of the tape, can radically affect design philosophy compared to the classical electrical engineering approach. Although specifically aimed at levitation transport the controllability data obtained have implications for a much wider range of applications.

Jones, Harry↗

NASA NTRS2002

Pulse Detonation Rocket MHD Power Experiment

A pulse detonation research engine (MSFC (Marshall Space Flight Center) Model PDRE (Pulse Detonation Rocket Engine) G-2) has been developed for the purpose of examining integrated propulsion and magnetohydrodynamic power generation applications. The engine is based on a rectangular cross-section tube coupled to a converging-diverging nozzle, which is in turn attached to a segmented Faraday channel. As part of the shakedown testing activity, the pressure wave was interrogated along the length of the engine while running on hydrogen/oxygen propellants. Rapid transition to detonation wave propagation was insured through the use of a short Schelkin spiral near the head of the engine. The measured detonation wave velocities were in excess of 2500 m/s in agreement with the theoretical C-J velocity. The engine was first tested in a straight tube configuration without a nozzle, and the time resolved thrust was measured simultaneously with the head-end pressure. Similar measurements were made with the converging-diverging nozzle attached. The time correlation of the thrust and head-end pressure data was found to be excellent. The major purpose of the converging-diverging nozzle was to configure the engine for driving an MHD generator for the direct production of electrical power. Additional tests were therefore necessary in which seed (cesium-hydroxide dissolved in methanol) was directly injected into the engine as a spray. The exhaust plume was then interrogated with a microwave interferometer in an attempt to characterize the plasma conditions, and emission spectroscopy measurements were also acquired. Data reduction efforts indicate that the plasma exhaust is very highly ionized, although there is some uncertainty at this time as to the relative abundance of negative OH ions. The emission spectroscopy data provided some indication of the species in the exhaust as well as a measurement of temperature. A 24-electrode-pair segmented Faraday channel and 0.6 Tesla permanent magnet assembly were then installed on Marshall Space Flight Center's (MSFC's) rectangular channel pulse detonation research engine. Magnetohydrodynamic (MHD) electrical power extraction experiments were carried out for a range of load impedances in which cesium hydroxide seed (dissolved in methanol) was sprayed into the gaseous oxygen/hydrogen propellants. Positive power extraction was obtained, but preliminary analysis of the data indicated that the plasma electrical conductivity is lower than anticipated and the near-electrode voltage drop is not negligible. It is believed that the electrical conductivity is reduced due to a large population of negative OH ions. This occurs because OH has a strong affinity for capturing free electrons. The effect of near-electrode voltage drop is associated with the high surface-to-volume ratio of the channel (1-inch by 1-inch cross-section) where surface effects play a dominant role. As usual for MHD devices, higher performance will require larger scale devices. Overall, the gathered data is extremely valuable from the standpoint of understanding plasma behavior and for developing empirical scaling laws.

Litchford, Ron J.↗

NASA NTRS2004

Development of Columbia Leading Edge Reconstruction System

After the loss of Columbia in 2003, the Columbia Accident Investigation Board and NASA KSC directed personnel at the Launch Equipment Test Facility (LETF) to design and build high fidelity mock-ups of Columbia's left wing leading edges. These leading edge segments, constructed of reinforced carbon-carbon, were a major point of inquiry by the investigation team. The LETF engineers developed a concept of building a clear Lexan panel with an aluminum support structure ten percent larger than the original panel. The leading edge debris are attached to the Lexan panels and both the front and back side of each panel are visible for inspection. The entire assembly can be rotated, to provide visual access to the entire panel. Six carts were fabricated to support the thirteen panels. These carts could be set up in order, next to each other, to provide the desired inspection access. The carts and attached debris are currently located in the Vehicle Assembly Building at KSC.

Trautwein, John↗

NASA NTRS2016

Propulsion Wheel Motor for an Electric Vehicle

A wheel assembly for an electric vehicle includes a wheel rim that is concentrically disposed about a central axis. A propulsion-braking module is disposed within an interior region of the wheel rim. The propulsion-braking module rotatably supports the wheel rim for rotation about the central axis. The propulsion-braking module includes a liquid cooled electric motor having a rotor rotatable about the central axis, and a stator disposed radially inside the rotor relative to the central axis. A motor-wheel interface hub is fixedly attached to the wheel rim, and is directly attached to the rotor for rotation with the rotor. The motor-wheel interface hub directly transmits torque from the electric motor to the wheel rim at a 1:1 ratio. The propulsion-braking module includes a drum brake system having an electric motor that rotates a cam device, which actuates the brake shoes.

Figuered, Joshua M.↗

NASA NTRS1988

A TEOM (tm) particulate monitor for comet dust, near Earth space, and planetary atmospheres

Scientific missions to comets, near earth space, and planetary atmospheres require particulate and mass accumulation instrumentation for both scientific and navigation purposes. The Rupprecht & Patashnick tapered element oscillating microbalance can accurately measure both mass flux and mass distribution of particulates over a wide range of particle sizes and loadings. Individual particles of milligram size down to a few picograms can be resolved and counted, and the accumulation of smaller particles or molecular deposition can be accurately measured using the sensors perfected and toughened under this contract. No other sensor has the dynamic range or sensitivity attained by these picogram direct mass measurement sensors. The purpose of this contract was to develop and implement reliable and repeatable manufacturing methods; build and test prototype sensors; and outline a quality control program. A dust 'thrower' was to be designed and built, and used to verify performance. Characterization and improvement of the optical motion detection system and drive feedback circuitry was to be undertaken, with emphasis on reliability, low noise, and low power consumption. All the goals of the contract were met or exceeded. An automated glass puller was built and used to make repeatable tapered elements. Materials and assembly methods were standardized, and controllers and calibrated fixtures were developed and used in all phases of preparing, coating and assembling the sensors. Quality control and reliability resulted from the use of calibrated manufacturing equipment with measurable working parameters. Thermal and vibration testing of completed prototypes showed low temperature sensitivity and high vibration tolerance. An electrostatic dust thrower was used in vacuum to throw particles from 2 x 10(exp 6) g to 7 x 10(exp -12) g in size. Using long averaging times, particles as small as 0.7 to 4 x 10(exp 11) g were weighted to resolutions in the 5 to 9 x 10(exp -13) g range. The drive circuit and optics systems were developed beyond what was anticipated in the contract, and are now virtually flight prototypes. There is already commercial interest in the developed capability of measuring picogram mass losses and gains. One area is contamination and outgassing research, both measuring picogram losses from samples and collecting products of outgassing.

Source record↗

NASA NTRS2002

Three Dimensional CFD Analysis of the GTX Combustor

The annular combustor geometry of a combined-cycle engine has been analyzed with three-dimensional computational fluid dynamics. Both subsonic combustion and supersonic combustion flowfields have been simulated. The subsonic combustion analysis was executed in conjunction with a direct-connect test rig. Two cold-flow and one hot-flow results are presented. The simulations compare favorably with the test data for the two cold flow calculations; the hot-flow data was not yet available. The hot-flow simulation indicates that the conventional ejector-ramjet cycle would not provide adequate mixing at the conditions tested. The supersonic combustion ramjet flowfield was simulated with frozen chemistry model. A five-parameter test matrix was specified, according to statistical design-of-experiments theory. Twenty-seven separate simulations were used to assemble surrogate models for combustor mixing efficiency and total pressure recovery. ScramJet injector design parameters (injector angle, location, and fuel split) as well as mission variables (total fuel massflow and freestream Mach number) were included in the analysis. A promising injector design has been identified that provides good mixing characteristics with low total pressure losses. The surrogate models can be used to develop performance maps of different injector designs. Several complex three-way variable interactions appear within the dataset that are not adequately resolved with the current statistical analysis.

Steffen, C. J., Jr.↗

NASA NTRS2002

Three Dimensional CFD Analysis of the GTX Combustor

The annular combustor geometry of a combined-cycle engine has been analyzed with three-dimensional computational fluid dynamics. Both subsonic combustion and supersonic combustion flowfields have been simulated. The subsonic combustion analysis was executed in conjunction with a direct-connect test rig. Two cold-flow and one hot-flow results are presented. The simulations compare favorably with the test data for the two cold flow calculations; the hot-flow data was not yet available. The hot-flow simulation Indicates that the conventional ejector-ramjet cycle would not provide adequate mixing at the conditions tested. The supersonic combustion ramjet flowfield was simulated with frozen chemistry model. A five-parameter test matrix was specified, according to statistical design-of-experiments theory. Twenty-seven separate simulations were used to assemble surrogate models for combustor mixing efficiency and total pressure recovery. Scramjet injector design parameters (injector angle, location, and fuel split) as well as mission variables (total fuel mass flow and freestream Mach number) were included in the analysis. A promising injector design has been identified that provides good mixing characteristics with low total pressure losses. The surrogate models can be used to develop performance maps of different injector designs. Several complex three-way variable interactions appear within the dataset that are not adequately resolved with the current statistical analysis.

Steffen, C. J., Jr.↗

NASA NTRS2008

The Next Giant Leap: NASA's Ares Launch Vehicles Overview

The next chapter in NASA's history also promises to write the next chapter in America's history, as the Agency makes measurable strides toward developing new space transportation capabilities that wi!! put astronauts on course to explore the Moon as the next giant leap toward the first human footprint on Mars. This paper will present top-level plans and progress being made toward fielding the Ares I crew launch vehicle in the 2013 timeframe and the Ares V cargo launch vehicle in the 2018 timeframe. It also gives insight into the objectives for the first test flight, known as the Ares I-X, which is scheduled for April 2009. The U.S. strategy to scientifically explore space will fuel innovations such as solar power and water recycling, as well as yield new knowledge that directly benefits life on Earth. For the Ares launch vehicles, NASA is building on heritage hardware and unique capabilities; as well as almost 50 years of lessons learned from the Apollo Saturn, Space Shuttle, and commercial launch vehicle programs. In the Ares I Project's inaugural year, extensive trade studies and evaluations were conducted to improve upon the designs initially recommended by the Exploration Systems Architecture Study, resulting in significant reduction of near-term and long-range technical and programmatic risks; conceptual designs were analyzed for fitness against requirements; and the contractual framework was assembled to enable a development effort unparalleled in American space flight since the Space Shuttle. The Exploration Launch Projects team completed the Ares I System Requirements Review (SRR) at the end of 2006--the first such engineering milestone for a human-rated space transportation system in over 30 years.

Cook, Stephen A.↗

NASA NTRS2002

Charter and activities of the SIRTF in-orbit checkout focus integrated products team and optical performance of the CTA

We describe a strategy to determine the initial mirror spacing by quantitatively evaluating the shapes of the images formed by the telescope using the Infrared Array Camera and other science instruments. We show that this information can be used to predict the direction and magnitude of the secondary mirror move that will result in the telescope best focus. The tools used to evaluate focus position and optical quality of the in orbit CTA have been qualified during the BRUTUS test are here described.

Integrated↗

NASA NTRS2021

Operational Modal Analysis of the Space Launch System Mobile Launcher on the Crawler Transporter ISVV-010 Rollout

NASA is developing an expendable heavy lift launch vehicle capability, the Space Launch System, to support lunar and deep space exploration. To support this capability, an updated ground infrastructure is required including modifying an existing Mobile Launcher system. The Mobile Launcher is a very large heavy beam/truss steel structure designed to support the Space Launch System during its buildup and integration in the Vehicle Assembly Building, transportation between the Vehicle Assembly Building and launch pad 39B by the Crawler Transporter, and provides the launch platform at the launch pad. As part of the Verification and Validation of the Mobile Launcher and Crawler Transporter, two rollouts of the Mobile Launcher transported by the Crawler Transporter, Integrated System Verification and Validation (ISVV) 005 and 010, have been performed to demonstrate the Crawler Transporter’s ability to transport the Mobile Launcher. ISVV-005 occurred in September 2018 and ISVV-010 occurred in late June 2019. ISVV-005 and ISVV-010 also provided the opportunity to gather data that can be used identify the Mobile Launcher on the Crawler Transporter rollout modal characteristics and refine the estimates of the Artemis I integrated launch vehicle rollout forcing functions. While the rollout environment has historically produced relatively small launch vehicle structural loads for the Saturn/Apollo and Space Shuttle programs in comparison to launch and ascent loads, these relatively small structural loads are inputs to structural fatigue analyses. The same holds true for the Space Launch System. Because the rollout forces acting on the Mobile Launcher and the Crawler Transporter are not directly measurable, Operational Modal Analysis techniques, instead of traditional Experimental Modal Analysis techniques, provide an empirical means to identify the Mobile Launcher on the Crawler Transporter rollout modal characteristics. The ISVV-010 rollout modal characteristics provide important supplemental modal information, which along with the Mobile Launcher modal test that was performed in June 2019 immediately prior to ISVV-010 rollout, combine to reduce uncertainty in the test correlated Mobile Launcher on the Crawler Transporter finite element model. A well test correlated finite element model will play a key role in the Building Block approach the Space Launch System program has implemented as part of its certification process for the Artemis I flight and in refining the Artemis I rollout forcing functions. At the time of the ISVV-005 rollout in September 2018, the Mobile Launcher was still undergoing construction, and therefore its modal characteristics are not directly comparable to those of the Mobile Launcher during the June 2019 Mobile Launcher modal test and subsequent ISVV-010 rollout. Hence the ISVV-005 rollout modal characteristics will not be looked at in this paper. This paper will briefly describe the Mobile Launcher and Crawler Transporter physical characteristics, ISVV-010 rollout data collection, the challenges in implementing Operational Modal Analysis techniques due in part to the Crawler Transporter harmonics, and how these challenges were overcome to obtain the ISVV-010 Mobile Launcher on the Crawler Transporter rollout modal characteristics.

Apollo↗

NASA NTRS1977

Shuttle payload minimum cost vibroacoustic tests

This paper is directed toward the development of the methodology needed to evaluate cost effective vibroacoustic test plans for Shuttle Spacelab payloads. Statistical decision theory is used to quantitatively evaluate seven alternate test plans by deriving optimum test levels and the expected cost for each multiple mission payload considered. The results indicate that minimum costs can vary by as much as $6 million for the various test plans. The lowest cost approach eliminates component testing and maintains flight vibration reliability by performing subassembly tests at a relatively high acoustic level. Test plans using system testing or combinations of component and assembly level testing are attractive alternatives. Component testing alone is shown not to be cost effective.

Stahle, C. V.↗

NASA NTRS2001

A Model for Macromolecular Crystallization

Macromolecular crystallization is a complex process. involving a system which typically has 5 or more components (macromolecule, water, buffer + counter ion, and precipitant). Whereas small molecules have only several well defined contacts in the crystal lattice, macromolecules generally have 10's or even 100's of contacts between molecules. These can range from hydrogen bonds (direct or water-mediated), through van der Waals, hydrophobic, salt bridges, and ion-mediated contacts. The latter interactions are stronger and require some specificity in the molecular alignment, while the others are weaker, more prevalent, and more promiscuous, i.e., can often be readily broken and reformed between other sites. Formation of a consistent, ordered, 3D structure may be impossible in the absence of any or presence of too many strong interactions. Further complicating the process is the inherent structural asymmetry of monomeric single chain macromolecules. The process of crystal nucleation and growth involves the ordered assembly of growth units into a defined 3D lattice. We suggest that for many macromolecules, particularly those that are monomeric, this involves a preliminary solution-phase assembly process into a growth unit having some symmetry prior to addition to the lattice, recapitulating the initial stages of the nucleation process. If this model is correct then fluids and crystal growth models assuming a strictly monodisperse nutrient solution need to be revised. Experimental evidence, based upon face growth rate, AFM, and fluorescence energy transfer data, for a postulated model of the nucleation of tetragonal lysozyme crystals and how it transitions into crystal growth will be presented.

Pusey, Marc L.↗

NASA NTRSDate not supplied

Operational Modal Analysis of the Space Launch System Mobile Launcher on the Crawler Transporter ISVV-010 Rollout

Apollo↗

NASA NTRS1987

Dual motion valve with single motion input

A dual motion valve includes two dual motion valve assemblies with a rotary input which allows the benefits of applying both rotary and axial motion to a rotary sealing element with a plurality of ports. The motion of the rotary sealing element during actuation provides axial engagement of the rotary sealing element with a stationary valve plate which also has ports. Fluid passages are created through the valve when the ports of the rotary sealing element are aligned with the ports of the stationary valve plate. Alignment is achieved through rotation of the rotary sealing element with respect to the stationary valve plate. The fluid passages provide direct paths which minimize fluid turbulence created in the fluid as it passes through the valve.

Belew, Robert↗