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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1997

Automatic Jet Contrail Detection and Segmentation

Jet contrails are an important subset of cirrus clouds in the atmosphere, and thin cirrus are thought to enhance the greenhouse effect due to their semi-transparent nature. They are nearly transparent to the solar energy reaching the surface, but they reduce the planetary emission to space due to their cold ambient temperatures. Having 'seeded' the environment, contrails often elongate and widen into cirrus-like features. However, there is great uncertainty regarding the impact of contrails on surface temperature and precipitation. With increasing numbers of subsonic aircraft operating in the upper troposphere, there is the possibility of increasing cloudiness which could lead to changes in the radiation balance. Automatic detection and seg- mentation of jet contrails in satellite imagery is important because (1) it is impractical to compile a contrail climatology by hand, and (2) with the segmented images it will be possible to retrieve contrail physical properties such as optical thickness, effective ice crystal diameter and emissivity.

Weiss, J.↗
NASA NTRS1996

Capillary Movement in Granular Beds in Microgravity

Understanding the dynamics of capillary flow through unsaturated porous media is very important for the development of an effective water and nutrient delivery system for growing plants in microgravity and chemical engineering applications. Experiments were conducted on the Space Shuttle during the STS-63 mission using three experimental cuvettes called "Capillary Testbed-M." These experiments studied the effect of bead diameter on capillary flow by comparing the capillary flow in three different granular beds. It was observed that the speed of water propagation in the granular bed consisting of 1.5 mm diameter particles was less than that in the bed consisting of 1.0 mm. diameter particles. Such results contradict the existing theory of capillary water propagation in granular beds. It was found also that in microgravity water propagates independently in adjacent layers of a layered granular bed .

Yendler, Boris S.↗
NASA NTRS2002

Ion Engine and Hall Thruster Development at the NASA Glenn Research Center

NASA's Glenn Research Center has been selected to lead development of NASA's Evolutionary Xenon Thruster (NEXT) system. The central feature of the NEXT system is an electric propulsion thruster (EPT) that inherits the knowledge gained through the NSTAR thruster that successfully propelled Deep Space 1 to asteroid Braille and comet Borrelly, while significantly increasing the thruster power level and making improvements in performance parameters associated with NSTAR. The EPT concept under development has a 40 cm beam diameter, twice the effective area of the Deep-Space 1 thruster, while maintaining a relatively-small volume. It incorporates mechanical features and operating conditions to maximize the design heritage established by the flight NSTAR 30 cm engine, while incorporating new technology where warranted to extend the power and throughput capability. The NASA Hall thruster program currently supports a number of tasks related to high power thruster development for a number of customers including the Energetics Program (formerly called the Space-based Program), the Space Solar Power Program, and the In-space Propulsion Program. In program year 2002, two tasks were central to the NASA Hall thruster program: 1.) the development of a laboratory Hall thruster capable of providing high thrust at high power; 2.) investigations into operation of Hall thrusters at high specific impulse. In addition to these two primary thruster development activities, there are a number of other on-going activities supported by the NASA Hall thruster program, These additional activities are related to issues such as thruster lifetime and spacecraft integration.

Domonkos, Matthew T.↗
NASA NTRS2001

Next-Generation Ion Propulsion Being Developed

The NASA Glenn Research Center ion-propulsion program addresses the need for high specific-impulse systems and technology across a broad range of mission applications and power levels. One activity is the development of the next-generation ion-propulsion system as a follow-on to the successful Deep Space 1 system. The system is envisioned to incorporate a lightweight ion engine that can operate over 1 to 10 kW, with a 550-kg propellant throughput capacity. The engine concept under development has a 40-cm beam diameter, twice the effective area of the Deep Space 1 engine. It incorporates mechanical features and operating conditions to maximize the design heritage established by the Deep Space 1 engine, while incorporating new technology where warranted to extend the power and throughput capability. Prototype versions of the engine have been fabricated and are under test at NASA, with an engineering model version in manufacturing. Preliminary performance data for the prototype engine have been documented over 1.1- to 7.3-kW input power. At 7.3 kW, the engine efficiency is 0.68, at 3615-sec specific impulse. Critical component temperatures, including those of the discharge cathode assembly and magnets, have been documented and are within established limits, with significant margins relative to the Deep Space 1 engine. The 1- to 10-kW ion thruster approach described here was found to provide the needed power and performance improvement to enable important NASA missions. The Integrated In-Space Transportation Planning (IISTP) studies compared many potential technologies for various NASA, Government, and commercial missions. These studies indicated that a high-power ion propulsion system is the most important technology for development because of its outstanding performance versus perceived development and recurring costs for interplanetary solar electric propulsion missions. One of the best applications of a highpower electric propulsion system was as an integral part of a solar electric propulsion (SEP) stage to send a payload to outer planet targets. The IISTP studies showed that either trip time or launch vehicle class could be significantly reduced when compared with state-of-the-art systems.

Patterson, Michael J.↗
NASA NTRS2003

Performance Enhancement of Unsteady Ejectors Investigated Using a Pulsejet Driver

Unsteady ejectors are currently under investigation for use in some pulse detonation engine (PDE) propulsion systems. This is due primarily to their potential high performance in comparison to steady ejectors of similar dimensions relative to the source or driver jet. Although some experimental work has been done in the past to study thrust augmentation with unsteady ejectors, there is no proven theory by which optimal design parameters can be selected and an effective ejector constructed for a given pulsed flow. Therefore, an experimental facility was developed at the NASA Glenn Research Center to study the correlation between ejector design and performance, and to get a better understanding of the flow phenomena that result in thrust augmentation. A commercially available pulsejet was used for the unsteady driving jet. This was paired with a basic, yet flexible, ejector design that allowed parametric evaluation of the effects that length, diameter, and inlet radius have on performance.

Paxson, Daniel E.↗
NASA NTRS2008

Investigation of Condensing Ice Heat Exchangers for MTSA Technology Development

Metabolic heat regenerated Temperature Swing Adsorption (MTSA) technology is being developed for thermal, carbon dioxide (CO2) and humidity control for a Portable Life Support Subsystem (PLSS). Metabolically-produced CO2 present in the ventilation gas of a PLSS is collected using a CO2selective adsorbent via temperature swing adsorption. The temperature swing is initiated through cooling to well below metabolic temperatures. Cooling is achieved with a sublimation heat exchanger using water or liquid carbon dioxide (LCO2) expanded below sublimation temperature when exposed to low pressure or vacuum. Subsequent super heated vapor, as well as additional coolant, is used to further cool the astronaut. The temperature swing on the adsorbent is then completed by warming the adsorbent with a separate condensing ice heat exchanger (CIHX) using metabolic heat from moist ventilation gas. The condensed humidity in the ventilation gas is recycled at the habitat. The water condensation from the ventilation gas is a significant heat transfer mechanism for the warming of the adsorbent bed because it represents as much as half of the energy potential in the moist ventilation gas. Designing a heat exchanger to efficiently transfer this energy to the adsorbent bed and allow the collection of the water is a challenge since the CIHX will operate in a temperature range from 210K to 280K. The ventilation gas moisture will first freeze and then thaw, sometimes existing in three phases simultaneously. A NASA Small Business Innovative Research (SBIR) Phase 1 contract was performed to investigate condensing and icing as applied to MTSA to enable higher fidelity modeling and assess the impact of geometry variables on CIHX performance for future CIHX design optimization. Specifically, a design tool was created using analytical relations to explore the complex, interdependent design space of a condensing ice heat exchanger. Numerous variables were identified as having nontrivial contributions to performance such as hydraulic diameter, heat exchanger effectiveness, ventilation gas mass flow rate and surface roughness. Using this tool, four test articles were designed and manufactured to map to a full MTSA subassembly (the adsorbent bed, the sublimation heat exchanger for cooling and the condensing ice heat exchanger for warming). The design mapping considered impacts due to CIHX geometry as well as subassembly impacts such as thermal mass and thermal resistance through the adsorbent bed. The test articles were tested at simulated PLSS ventilation loop temperature, moisture content and subambient pressure. Ice accumulation and melting were observed. Data and test observations were analyzed to identify drivers of the condensing ice heat exchanger performance. This paper will discuss the analytical models, the test article designs, and testing procedures. Testing issues will be discussed to better describe data and share lessons learned. Data analysis and subsequent conclusions will be presented.

Padilla, Sebastian↗
NASA NTRS2009

Mirror Technology Development for the International X-ray Observatory Mission

The International X-ray Observatory (1x0) mission requires a large mirror assembly with an angular resolution of 5" half-power diameter and an effective area of 3 m2. We are developing a glass slumping technique that is coming close to meeting these requirements. In the last few years significant and steady progress has been made in mirror segment fabrication, metrology, and alignment and integration. In this paper, we will present a status update on the various components of the technology, including mirror fabrication, glass screening and strengthening, coating, mirror mount and metrology. alignment and integration. We will also present our plan and expectations for the next couple of years.

Zhang, William↗
NASA NTRS2006

Three-Dimensional Thermal Boundary Layer Corrections for Circular Heat Flux Gauges Mounted in a Flat Plate with a Surface Temperature Discontinuity

Three-dimensional Navier-Stokes computational fluid dynamics (CFD) analysis has been performed in an effort to determine thermal boundary layer correction factors for circular convective heat flux gauges (such as Schmidt-Boelter and plug type)mounted flush in a flat plate subjected to a stepwise surface temperature discontinuity. Turbulent flow solutions with temperature-dependent properties are obtained for a free stream Reynolds number of 1E6, and freestream Mach numbers of 2 and 4. The effect of gauge diameter and the plate surface temperature have been investigated. The 3-D CFD results for the heat flux correction factors are compared to quasi-21) results deduced from constant property integral solutions and also 2-D CFD analysis with both constant and variable properties. The role of three-dimensionality and of property variations on the heat flux correction factors has been demonstrated.

Kandula, M.↗
NASA NTRS2014

Combustion Stability Assessments of the Black Brant Solid Rocket Motor

The Black Brant variation of the Standard Brant developed in the 1960's has been a workhorse motor of the NASA Sounding Rocket Project Office (SRPO) since the 1970's. In March 2012, the Black Brant Mk1 used on mission 36.277 experienced combustion instability during a flight at White Sands Missile Range, the third event in the last four years, the first occurring in November, 2009, the second in April 2010. After the 2010 event the program has been increasing the motor's throat diameter post-delivery with the goal of lowering the chamber pressure and increasing the margin against combustion instability. During the most recent combustion instability event, the vibrations exceeded the qualification levels for the Flight Termination System. The present study utilizes data generated from T-burner testing of multiple Black Brant propellants at the Naval Air Warfare Center at China Lake, to improve the combustion stability predictions for the Black Brant Mk1 and to generate new predictions for the Mk2. Three unique one dimensional (1-D) stability models were generated, representing distinct Black Brant flights, two of which experienced instabilities. The individual models allowed for comparison of stability characteristics between various nozzle configurations. A long standing "rule of thumb" states that increased stability margin is gained by increasing the throat diameter. In contradiction to this experience based rule, the analysis shows that little or no margin is gained from a larger throat diameter. The present analysis demonstrates competing effects resulting from an increased throat diameter accompanying a large response function. As is expected, more acoustic energy was expelled through the nozzle, but conversely more acoustic energy was generated due to larger gas velocities near the propellant surfaces.

Fischbach, Sean↗
NASA NTRS2014

OCCAMS: Optically Controlled and Corrected Active Meta-Material Space Structures

Telescopes require sub-wavelength figure (shape) error in order to achieve acceptable Strehl ratios. Traditional methods of achieving this require rigid and therefore heavy mirrors and reaction structures as well as proportionally heavy and expensive spacecraft busses and launch vehicles. This effectively limits the diameter and therefore resolution and collecting area of space optics. Large diameter telescopes must either be heavy or actively controlled. Space telescopes of the size proposed for missions such as TPF (Terrestrial Planet Finder), TPI (Terrestrial Planet Imager), etc. will likely require large active primaries and structures and corrective optics to implement downstream wavefront control. We propose a novel viable enabling technology. High resolution space imaging requires the production of lightweight large aperture optics subject to design tradespace constraints based on nanometer physical tolerances, low system aerial density, high control authority, suitable thermal and mechanical properties, deployment capability, launch vehicle volume constraints, as well as production cost and schedule risk mitigation. Segmented systems impose additional requirements on segment alignment, wavefront phasing, and telescope mass with increased edge diffraction. Photons weigh nothing. Why must even small space telescopes "weigh" tons? Our team is working to demonstrate that they do not, by leveraging 15 years of effort and a novel advanced concept.The ultimate research goal is to refine technology to produce a mission capable ultra-lightweight membrane optic whose shape can be remotely controlled using a laser beam. Using our novel optically-controlled molecular actuators allows substitution of optically-induced control for rigidity and mirror mass. In analogy with noise-canceling headphones, this technique also potentially provides a way to excite vibratory modes to couple with and damp out normal modes of oscillation induced by slewing, other motion and thermal changes, thus allowing a robust response to repointing of a large aperture.

Astronomy↗
NASA NTRSDate not supplied

Impact Experiments into Granular Targets Containing Solitary Blocks of Varying Strength and Size

Crater scaling relationships provide a means to correlate dimensions of laboratory-scale impact experiments to naturally formed craters at planetary scales. For relatively larger impact events, where gravity is the dominant arresting force against crater growth, these scaling relations are comparatively simple. For smaller craters, however, the target properties have increasing influence over the cratering process. Further complexities are easily envisaged when considering realistic surfaces that contain small-scale heterogeneities in cohesive strength, density, porosity, friction, as these properties will each have unequal effects on the resultant crater morphometry. Even when produced under controlled laboratory conditions, understanding (and controlling) the entire relevant parameter space is daunting, and deconvolution of the relevant contributors can be complicated even in the best-case scenario. To this end, we have begun an extensive series of impact experiments that will provide a nascent framework that will aid in the interpretation of craters observed on complex natural surfaces throughout the solar system. To start with the simplest configuration, experiments were performed with cylindrical PVC buckets that were filled with quartz sand and contained a single cubic block of synthetic sandstone. The blocks varied in size (14-33 mm) and unconfined compressive strength (0.5-7.4 MPa) and were placed in/on the sand along the trajectory of the incoming impactor and buried to different depths. All experiments were conducted using the vertical gun located in the Experimental Impact Lab at NASA Johnson Space Center with alumina projectiles that were accelerated to ~1.53 km s^-1 under a vacuum of 1 torr. After the impact, target containers were removed from the chamber are morphometric data were extracted by using a Peel 2 3D-scanner in combination with the open-source software, CloudCompare. Initial results show that block strength is a secondary effect on crater diameter and depth, but when at least one edge of the block is exposed and the surface (partial burial) the strength will dictate the number of surviving block fragments around the crater, as well as how much disrupted block material is retained within the crater walls.

Christopher J. Cline II↗
NASA NTRS1972

An analytical investigation of the impingement of jets on curved deflectors.

Numerical solutions are obtained for the cases of straight circular jets impinging on axisymmetric curved surfaces, and plane jets impinging symmetrically on two-dimensional curved surfaces. These geometries are representative of some types of thrust reversers for transport aircraft. The solutions are based on the assumptions of incompressible and potential flow. The velocity field, pressure distribution at the deflector surface, and reverser effectiveness are predicted for deflector turning angles of 15 to 75 deg, deflector width to jet diameter ratios of 1.5-2.0, and ratios of deflector clearance to jet diameter of 1.0-3.0. Reverser effectiveness is found to be a maximum for a ratio of deflector clearance to jet diameter of about 2.0. The effect of back pressuring resulting from the presence of the deflector is predicted.

Schnurr, N. M.↗
NASA NTRS1991

Effect of the rotational-vibrational excitation on molecular diameters

The kinetic molecular diameters of rotationally and vibrationally excited diatomic molecules and molecular ions are derived as functions of the rotational and vibrational quantum numbers of the molecules. Typical molecular diameters are studied in two cases: in low-temperature gas, where the molecular diameter is independent of the degree of rotational-vibrational excitation of the molecules, and in high-temperature gas, where the molecular diameter depends on the degree of rotational-vibrational excitation of the molecules. The rotational-vibrational excitation of molecules is shown to have a meaningful effect on the collisional properties of gases. The effect is stronger in gases of weakly-bound molecules.

Kang, S. H.↗
NASA NTRS1975

Effect of number of lobes and length-diameter ratio on stability of tilted-lobe hydrodynamic journal bearings at zero load

Hydrodynamic journal stability tests were conducted with tilted-lobe bearings. The bearings had three, five, and seven lobes and length to diameter (L/D) ratios from 0.2 to 1.0. They were tested in water and MIL-L-7808G oil at 294 K (70 F) at speeds to 5400 rpm with zero load. Stability was not appreciably affected by the number of lobes and decreased with a decrease in L/D ratio. However, a three-tilted-lobe bearing with an offset factor of 0.76 and an L/D of 0.5 was more stable than a three centrally lobed bearing with an offset factor of 0.50 and an L/D of 1.0.

Schuller, F. T.↗
NASA NTRS2008

Arterial Structure and Function in Women and Men Following Long Duration Bed Rest

Orthostatic intolerance is a well-recognized consequence of space flight and bed rest (BR), with a greater incidence reported in women. We hypothesized that leg, but not arm, arterial structure and function would be altered following prolonged BR, as a model of space flight, and that women would be more susceptible to BR-induced deconditioning than men. METHODS: Ten volunteers (5 males, 5 females) completed 90 d of 6 head-down BR. Subjects participated in tests of brachial (BA) and anterior tibial (AT) artery endothelium-dependent (flow mediated dilation [FMD] following 5-7 min of arterial occlusion) and endothelium-independent (0.4 mg sublingual nitroglycerin [SN]) vasodilation before BR (PRE) and on days 7 (BR7), 21 (BR21), and 90 (BR90) of BR. Vessel diameter and intimal medial thickness (IMT) were measured by ultrasound. IMT, baseline diameter, and percent change in diameter from baseline during FMD and SN tests were compared across BR and between genders using repeated measures two-way ANOVA with Bonferroni post-hoc tests in which PRE and women were control conditions. RESULTS: Baseline vessel diameter was lower in women than in men in both the BA (p=0.005) and AT (p=0.01) across all days. Baseline AT diameter decreased during BR (p=0.01) and tended to be more profound in women (interaction, p=0.06). AT diameter was reduced in women at BR21 and BR90 (p<0.01) but not in men. In contrast, there was no BR effect on baseline BA diameter. IMT also decreased in the AT (p<0.001) but not in the BA during BR; AT IMT was reduced by BR21 (p<0.05). As a group, there was no effect of BR on AT FMD, BA FMD, and AT SN-dilation, although BA SN-dilation was significantly reduced on BR21 (p=0.01). Across all BR days, women exhibited higher AT FMD (p=0.03), BA FMD (p=0.02), and BA SN-dilation (p=0.01) and tended to demonstrate greater AT SN-dilation (p=0.11). CONCLUSIONS: These preliminary results suggest that arterial remodeling occurs during BR in the leg (decreased diameter and IMT), but not in the arm, and that women appear to be more responsive to BR than men. These changes in the leg, coupled with larger responses to direct and indirect stimulation of the arterial smooth muscle, may be related to the greater incidence of orthostatic intolerance in women after BR and space flight.

Lee, Stuart M. C.↗
NASA NTRS1972

Viking configuration pitch damping derivatives as influenced by support interference and test technique at transonic and supersonic speeds.

Experimental studies to determine the 140-deg spherically-blunted cone configuration single degree-of-freedom damping derivative included model sting interference effects at M = 1.76 to 3.0. Minimal sting influences are noted with sting/model diameter ratios of 0.183 and effective sting lengths of 3.55 of the reference length. Increasing the ratio of sting diameter to reference length to 0.53 influences damping considerably at angles of attack from 0 to 3 deg at all Reynolds numbers but shows little or no effect at higher angles. Free-flight model wake geometries (wake neck position and size) correlate well with those from captive model tests with the small diameter sting; this adds confidence to obtaining damping derivatives through captive model testing. The damping characteristics of an early Viking configuration obtained on 11.23 and 4.35% scale models using forced and free oscillation test methods, respectively, in two different test facilities are compared. The agreement is quite good under test conditions.

Steinberg, S.↗