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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Segmented Hexagonal Antenna Reflector Concentrically Stacked Using Shape Memory Composite Tubular Hinges

A new architecture for solid surface reflector antennas scalable to sizes greater than 10 m is presented. The design combines the compact, lightness and simplicity characteristics of advanced deployable structures to create sub-reflectors that can be assembled in space into larger units using a robotic arm and operations under development by a related parallel project. The seven-panel hexagonal sub-reflector is divided into hexagonal panels of that efficiently stack concentrically and vertically. The central panel is connected to each side panel on the back side by a pair of tubular shape memory composite hinges that enable the required deployment kinematics. A secondary mechanism ultimately closes the interpanel gap. The focus of the paper is on the development of the sub-reflector elements, namely the tubular hinges that use embedded heaters and sensors for actuation, the actuation mechanisms, and the lightweight sandwich construction panels. A finite element analysis parametric study assessed how design features of the hinge affect its stowage and deployment dynamics. The component fabrication and testing plans for the two-panel assembly breadboard model are outlined.

deployable reflectors↗
NASA NTRS1986

Composite tubes for the Space Station truss structure

The reference configuration of NASA's Space Station includes a large truss structure to support the various modules and solar arrays. This truss structure will be constructed from tubular members approximately 2 in. in diameter and up to 23 ft in length. The important design considerations for this structure are light weight, high stiffness, dimensional stability, and long-term durability. Continuous graphite fiber reinforced polymer matrix composite materials can meet the structural requirements, and are leading candidates for the tubular truss members. However, there are concerns regarding the durability of composites during the long-term exposure to atomic oxygen and thermal cycling that will be encountered during the Space Station service life. This paper discusses space environmental factors and their effect on composite materials, and provides estimates of the changes in mechanical and thermal properties of composites exposed to long-term Space Station conditions. The effect of low velocity impact and handling damage on composite tube properties is also discussed.

Bowles, David E.↗
NASA NTRS2008

Preliminary Structural Design Considerations and Mass Efficiencies for Lunar Surface Manipulator Concepts

The mass and sizing characteristics of manipulators for Lunar and Mars planetary surface applications are investigated by analyzing three structural configurations: a simple cantilevered boom with a square tubular cross-section; a hybrid cable/boom configuration with a square tubular cross-section support structure; and a hybrid cable/boom configuration with a square truss cross-section support structure. Design procedures are developed for the three configurations and numerical examples are given. A new set of performance parameters are developed that relate the mass of manipulators and cranes to a loading parameter. These parameters enable the masses of different manipulator configurations to be compared over a wide range of design loads and reach envelopes (radii). The use of these parameters is demonstrated in the form of a structural efficiency chart using the newly considered manipulator configurations. To understand the performance of Lunar and Mars manipulators, the design procedures were exercised on the three manipulator configurations assuming graphite/epoxy materials for the tubes and trusses. It is also assumed that the actuators are electric motor, gear reduction systems. Numerical results for manipulator masses and sizes are presented for a variety of manipulator reach and payload mass capabilities. Results are presented that demonstrate the sensitivity of manipulator mass to operational radius, tip force, and actuator efficiency. The effect of the value of gravitational force on the ratio of manipulator-mass to payload-mass is also shown. Finally, results are presented to demonstrate the relative mass reduction for the use of graphite/epoxy compared to aluminum for the support structure.

Dorsey, John T.↗
NASA NTRS1998

Flashback Arrestor for LPP, Low NOx Combustors

Lean premixed, prevaporized (LPP) high temperature combustor designs as explored for the Advanced Subsonic Transport (AST) and High Speed Civil Transport (HSCT) combustors can achieve low NO(x), emission levels. An enabling device is needed to arrest flashback and inhibit preignition at high power conditions and during transients (surge and rapid spool down). A novel flashback arrestor design has demonstrated the ability to arrest flashback and inhibit preignition in a 4.6 cm diameter tubular reactor at full power inlet temperatures (725 C) using Jet-A fuel at 0.4 less than or equal To phi less than or equal to 3.5. Several low pressure loss (0.2 to 0.4% at 30 m/s) flashback arrestor designs were developed which arrested flashback at all of the test conditions. Flame holding was also inhibited off the flash arrestor face or within the downstream tube even velocities (less than or equal to 3 to 6 m/s), thus protecting the flashback arrestor and combustor components. Upstream flow conditions influence the specific configuration based on using either a 45% or 76% upstream geometric blockage. Stationary, lean premixed dry low NO(x) gas turbine combustors would also benefit from this low pressure drop flashback arrestor design which can be easily integrated into new and existing designs.

Kraemer, Gil↗
NASA NTRS1982

Development of a preprototype times wastewater recovery subsystem

A three-man wastewater recovery preprototype subsystem using a hollow fiber membrane evaporator with a thermoelectric heat pump to provide efficient potable water recovery from wastewater on extended duration space flights was designed, fabricated, and tested at one-gravity. Low power, compactness and gravity insensitive operation are featured in this vacuum distillation subsystem. The tubular hollow fiber elements provide positive liquid/gas phase control with no moving parts, and provide structural integrity, improving on previous flat sheet membrane designs. A thermoelectric heat pump provides latent energy recovery. Application and integration of these key elements solved problems inherent in all previous reclamation subsystem designs.

Roebelen, G. J., Jr.↗
NASA NTRSDate not supplied

Segmented Solid Surface Reflector Concentrically Stacked With Tubular Shape Memory Composite Hinges

A new architecture for solid surface reflector antennas scalable to sizes greater than 10 m is presented. The design uses compact, light, and simple advanced deployable structures to create sub-reflectors that can be assembled in space into larger units using a robotic arm. The seven-panel hexagonal sub-reflector is divided into hexagonal panels that stack concentrically and vertically. The central panel is connected to each side panel on the back side by a pair of tubular shape memory composite hinges that enable the required deployment kinematics with controlled dynamics. A secondary mechanism closes the interpanel gap. The focus of the paper is on the development of the sub-reflector elements, namely the tubular hinges that use embedded heaters and sensors for triggering and control, the actuation mechanisms, and the lightweight sandwich construction reflector panels. A parametric study using finite element analyses was conducted to assess how design features of the hinge affect its stowage and deployment dynamics. The preliminary component fabrication and testing results for the two-panel assembly breadboard model are outlined. Finally, the results of the test campaign with the brassboard reflector model are presented. A comparison of deployed reflector surface deviation between the measured surface after the stowage and deployment process and the pre-test scans and the nominal surface revealed root mean square errors of less than 1 mm, as required by X-band radiofrequency transmission.

gravity offloading↗
NASA NTRS1993

Weld joint concepts for on-orbit repair of Space Station Freedom fluid system tube assemblies

Because Space Station Freedom (SSF) is an independent satellite, not depending upon another spacecraft for power, attitude control, or thermal regulation, it has a variety of tubular, fluid-carrying assemblies on-board. The systems of interest in this analysis provide breathing air (oxygen and nitrogen), a working fluid (two-phase anhydrous ammonia) for thermal control, and a monopropellant (hydrazine) for station reboost. The tube assemblies run both internally and externally with respect to the habitats. They are found in up to 50 ft. continuous lengths constructed of mostly AISI 316L stainless steel tubing, but also including some Inconel 625 nickel-iron and Monel 400 nickel-copper alloy tubing. The outer diameters (OD) of the tubes range from 0.25-1.25 inches, and the wall thickness between 0.028-.095 inches. The system operational pressures range from 377 psi (for the thermal control system) to 3400 psi (for the high pressure oxygen and nitrogen supply lines in the ECLSS). SSF is designed for a fifteen to thirty year mission. It is likely that the tubular assemblies (TA's) will sustain damage or fail during this lifetime such that they require repair or replacement. The nature of the damage will be combinations of punctures, chips, scratches, and creases and may be cosmetic or actually leaking. The causes of these hypothetical problems are postulated to be: (1) faulty or fatigued fluid joints--both QD's and butt-welds; (2) micro-meteoroid impacts; (3) collison with another man-made object; and (4) over-pressure strain or burst (system origin). While the current NASA baseline may be to temporarily patch the lines by clamping metal c-sections over the defect, and then perform high pressure injection of a sealing compound, it is clear that permanent repair of the line(s) is necessary. This permanent repair could be to replace the entire TA in the segment, or perhaps the segment itself, both alternatives being extremely expensive and risky. The former would likely require extensive EVA to release TA clamps and pose great risk to other engineering subsystems, and the latter would require major de-servicing of the Station.

Jolly, Steven D.↗
NASA NTRS1988

Mathematical modeling of solid oxide fuel cells

Development of predictive techniques, with regard to cell behavior, under various operating conditions is needed to improve cell performance, increase energy density, reduce manufacturing cost, and to broaden utilization of various fuels. Such technology would be especially beneficial for the solid oxide fuel cells (SOFC) at it early demonstration stage. The development of computer models to calculate the temperature, CD, reactant distributions in the tubular and monolithic SOFCs. Results indicate that problems of nonuniform heat generation and fuel gas depletion in the tubular cell module, and of size limitions in the monolithic (MOD 0) design may be encountered during FC operation.

Lu, Cheng-Yi↗
NASA NTRS2004

Self-Inflatable/Self-Rigidizable Reflectarray Antenna

A report describes recent progress in a continuing effort to develop large reflectarray antennas to be deployed in space. Major underlying concepts were reported in two prior NASA Tech Briefs articles: Inflatable Reflectarray Antennas (NPO- 20433), Vol. 23, No. 10 (October 1999), page 50 and Tape-Spring Reinforcements for Inflatable Structural Tubes (NPO-20615), Vol. 24, No. 7 (July 2000), page 58. To recapitulate: An antenna as proposed would include a reflectarray membrane stretched flat on a frame of multiple tubular booms that would be deployed by inflation. The instant report discusses design concepts and relevant basic mechanical principles. Among the concepts are alternative configurations of booms for holding the reflectarray membrane and its radio-frequency feed horn and the use of catenaries and constant-force springs to stretch the reflectarray membrane on the frame at the required tension. Some emphasis is placed on the need to keep the deployed frame rigid without depending on maintenance of inflation in the presence of impinging micrometeors that could cause leaks: for this purpose, the booms could be made as spring-tape-reinforced aluminum laminate tubes like those described in the second-mentioned prior article.

Fang, Houfei↗
NASA NTRS2004

Micro-Tubular Fuel Cells

Micro-tubular fuel cells that would operate at power levels on the order of hundreds of watts or less are under development as alternatives to batteries in numerous products - portable power tools, cellular telephones, laptop computers, portable television receivers, and small robotic vehicles, to name a few examples. Micro-tubular fuel cells exploit advances in the art of proton-exchange-membrane fuel cells. The main advantage of the micro-tubular fuel cells over the plate-and-frame fuel cells would be higher power densities: Whereas the mass and volume power densities of low-pressure hydrogen-and-oxygen-fuel plate-and-frame fuel cells designed to operate in the targeted power range are typically less than 0.1 W/g and 0.1 kW/L, micro-tubular fuel cells are expected to reach power densities much greater than 1 W/g and 1 kW/L. Because of their higher power densities, micro-tubular fuel cells would be better for powering portable equipment, and would be better suited to applications in which there are requirements for modularity to simplify maintenance or to facilitate scaling to higher power levels. The development of PEMFCs has conventionally focused on producing large stacks of cells that operate at typical power levels >5 kW. The usual approach taken to developing lower-power PEMFCs for applications like those listed above has been to simply shrink the basic plate-and-frame configuration to smaller dimensions. A conventional plate-and-frame fuel cell contains a membrane/electrode assembly in the form of a flat membrane with electrodes of the same active area bonded to both faces. In order to provide reactants to both electrodes, bipolar plates that contain flow passages are placed on both electrodes. The mass and volume overhead of the bipolar plates amounts to about 75 percent of the total mass and volume of a fuel-cell stack. Removing these bipolar plates in the micro-tubular fuel cell significantly increases the power density.

Kimble, Michael C.↗
NASA NTRS1979

Parametric study of potential early commercial MHD power plants

Three different reference power plant configurations were considered with parametric variations of the various design parameters for each plant. Two of the reference plant designs were based on the use of high temperature regenerative air preheaters separately fired by a low Btu gas produced from a coal gasifier which was integrated with the power plant. The third reference plant design was based on the use of oxygen enriched combustion air preheated to a more moderate temperature in a tubular type metallic recuperative heat exchanger which is part of the bottoming plant heat recovery system. Comparative information was developed on plant performance and economics. The highest net plant efficiency of about 45 percent was attained by the reference plant design with the use of a high temperature air preheater separately fired with the advanced entrained bed gasifier. The use of oxygen enrichment of the combustion air yielded the lowest cost of generating electricity at a slightly lower plant efficiency. Both of these two reference plant designs are identified as potentially attractive for early MHD power plant applications.

Hals, F. A.↗
NASA NTRS1956

Turbojet-engine Starting and Acceleration

From considerations of safety and reliability in performance of gas-turbine aircraft, it is clear that engine starting and acceleration are of utmost importance. For this reason extensive efforts have been devoted to the investigation of the factors involved in the starting and acceleration of engines. In chapter III it is shown that certain basic combustion requirements must be met before ignition can occur; consequently, the design and operation of an engine must be tailored to provide these basic requirements in the combustion zone of the engine, particularly in the vicinity of the ignition source. It is pointed out in chapter III that ignition by electrical discharges is aided by high pressure, high temperature, low gas velocity and turbulence, gaseous fuel-air mixture, proper mixture strength, and-an optimum spark. duration. The simultaneous achievement of all these requirements in an actual turbojet-engine combustor is obviously impossible, yet any attempt to satisfy as many requirements as possible will result in lower ignition energies, lower-weight ignition systems, and greater reliability. These factors together with size and cost considerations determine the acceptability of the final ignition system. It is further shown in chapter III that the problem of wall quenching affects engine starting. For example, the dimensions of the volume to be burned must be larger than the quenching distance at the lowest pressure and the most adverse fuel-air ratio encountered. This fact affects the design of cross-fire tubes between adjacent combustion chambers in a tubular-combustor turbojet engine. Only two chambers in these engines contain spark plugs; therefore, the flame must propagate through small connecting tubes between the chambers. The quenching studies indicate that if the cross-fire tubes are too narrow the flame will not propagate from one chamber to another. In order to better understand the role of the basic factors in actual engine operation, many investigations have been conducted in single combustors from gas-turbine engines and in full-scale engines in altitude tanks and in flight. The purpose of the present chapter is to discuss the results of such studies and, where possible, to interpret these results qualitatively in terms of the basic requirements reported in chapter III. The discussion parallels the three phases of turbojet engine starting: (1) Ignition of the fuel-air mixture (2) Propagation of flame throughout the combustion zone (3) Acceleration of the engine to operating speed.

Mc Cafferty, R. J.↗
NASA NTRS1978

NaOH-based high temperature heat-of-fusion thermal energy storage device

A material called Thermkeep, developed as a low-cost method for the storage of thermal energy for solar electric power generating systems is discussed. The storage device consists of an insulated cylinder containing Thermkeep in which coiled tubular heat exchangers are immersed. A one-tenth scale model of the design contains 25 heat-exchanger tubes and 1500 kg of Thermkeep. Its instrumentation includes thermocouples to measure internal Thermkeep temperatures, vessel surface, heated shroud surface, and pressure gauges to indicate heat-exchanger pressure drops. The test-circuit design is presented and experimental results are discussed.

Cohen, B. M.↗
NASA NTRS1986

A design study of hydrazine and biowaste resistojets

A generalized modeling program was adapted in BASIC on a personal computer to compare the performance of four types of biowaste resistojets and two types of hydrazine augmenters. Analyzed biowaste design types were: (1) an electrically conductive ceramic heater-exchanger of zirconia; (2) a truss heater of platinum in cross flow; (3) an immersed bicoiled tubular heater-exchanger; and (4) a nonexposed, refractory metal, radiant heater in a central cavity within a heat exchanger case. Concepts 2 and 3 are designed to have an efficient, stainless steel outer pressure case. The hydrazine design types are: (5) an immersed bicoil heater exchanger and (6) a nonexposed radiant heater now with a refractory metal case. The ceramic biowaste resistojet has the highest specific impulse growth potential at 2000 K of 192.5 (CO2) and 269 s (H2O). The bicoil produces the highest augmenter temperature of 1994 K for a 2073 K heater giving 317 s at .73 overall efficiency. Detailed temperature profiles of each of the designs are shown. The scaled layout drawings of each are presented with recommended materials and fabrication methods.

Page, R. J.↗
NASA NTRS1940

The Strength of Shell and Tubular Spar Wings

The report is a survey of the strength problems arising on shell and tubular spar wings. The treatment of the shell wing strength is primarily confined to those questions which concern the shell wing only; those pertaining to both shell wing and shell body together have already been treated in TM 838. The discussion of stress condition and compressive strength of shell wings and tubular spar wings is prefaced by several considerations concerning the spar and shell design of metal wings from the point of view of strength.

Ebner, H↗
NASA NTRS1974

Advanced beaded and tubular structural panels. Volume 2: Fabrication

A study was conducted to exploit the efficiency of curved elements in the design of lightweight structural panels under combined loads of axial compression, inplane shear, and bending. A summary of the total program (analysis, fabrication and test) is presented in document NASA CR-2514. Detailed descriptions of the analysis effort and of the panel tests are contained in supplementary documents NASA CR-132460 and NASA-CR-132515 respectively. Data are also given on the development of economical fabrication techniques to minimize the effects of fabrication limitations on optimum panel designs.

Musgrove, M. D.↗
NASA NTRS1993

A multi-zone muffle furnace design

A Multi-Zone Muffle-Tube Furnace was designed, built, and tested for the purpose of providing an in-house experience base with tubular furnaces for materials processing in microgravity. As such, it must not only provide the desired temperatures and controlled thermal gradients at several discrete zones along its length but must also be capable of sustaining the rigors of a Space Shuttle launch. The furnace is insulated to minimize radial and axial heat losses. It is contained in a water-cooled enclosure for purposes of dissipating un-wanted residual heat, keeping the outer surfaces of the furnace at a 'touch-safe' temperature, and providing a rugged housing. This report describes the salient features of the furnace, testing procedures and results, and concluding remarks evaluating the overall design.

Rowe, Neil D.↗
NASA NTRS1999

Stress Analysis and Permeability Testing of Cryogenic Composite Feed Line

For the next generation Single-Stage-To-Orbit (SSTO) Reusable Launch Vehicle (RLV), the use of advanced composite materials is highly desirable and critical to the success of the mission. NASA Marshall Space Flight Center (MSFC) has been working with the aerospace industry for many years to develop and demonstrate the cryogenic composite propellant tanks and feed lines technologies. A 50.8-mm diameter composite feed line for the Clipper Graham (DCY.A) was developed and tested. The purpose of the program is to demonstrate the LH2 permeability, composite to composite and metal joints, as well as composite flange interface of the composite feed line. Stress analysis and permeability testing have been performed on this article. Recently, a larger composite feed line design is being investigated and developed at MSFC for potential use in future RLV. The diameter of the feed line is 203 mm and the overall length is approximately 2.2 meters. This one piece unlined feed line consists of three straight tubular sections joined by two 90 degree elbows. The material chosen is IM7/977-3 prepreg fabric. The lay-up pattern is [0/90, plus or minus 45]s and is built up to 18 plies to the flanges at both ends. A preliminary stress analysis has been conducted to identify potential critical stresses and to develop the finite element analysis (FEA) capability of composite feed lines. As expected, the critical stresses occurred at the rims of some flange holes and the onset of the tapered tubular sections. Further analysis is required to determine the loads, flange deflection, vibration, and combined maximum loads. Two permeability-testing apparatuses were also designed for both flat panel specimens and curved feed line sections after impact damage. A larger permeant gas exposed area is required to accurately determine the effect of impact damage on the permeability of the feed line materials. The flat panel tester was fabricated and assembled. Three test coupons were made of graphite/epoxy plain weave prepreg and unidirectional prepreg. The flow rate was calculated by measuring the change of manometer fluid height per unit time. The permeability of the coupons is then calculated according to Darcy's Law. The pressure increase due to the head rise in the manometer was not considered for the initial estimation. The result of the unidirectional composite coupon agreed with that obtained from the DC-XA feed line testing of a similar material. Further improvement on the design may be required to improve the accuracy and efficiency of permeability testing.

Chu, Tsuchin Philip↗