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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 451 records · Page 25

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NASA NTRS1976

High energy density capacitors for vacuum operation with a pulsed plasma load

Results of the effort of designing, fabricating, and testing of a 40 joules/lb (88.2 joules/Kg) high voltage energy storage capacitor suitable for operating a pulsed plasma thruster in a vacuum environment for millions of pulses are presented. Using vacuum brazing and heli-arc welding techniques followed by vacuum and high pressure helium leak tests it was possible to produce a hermetically sealed relatively light weight enclosure for the dielectric system. An energy density of 40 joules/lb was realized with a KF-polyvinylidene fluoride dielectric system. One capacitor was D.C. life tested at 4 KV (107.8 joules/lb) for 2,000 hours before it failed. Another exceeded 2,670 hours without failure at 38.3 joules/lb. Pulse life testing in a vacuum exceeded 300,000 discharges with testing still in progress. The D.C. life test data shows a small decrease in capacitance and an increase in dissipation factor with time. Heat transfer from the load to the capacitor must also be considered besides the self-heat generated by the capacitor.

Guman, W. J.↗

NASA NTRS1976

Aerospike thrust chamber program

An existing, but damaged, 25,000-pound thrust, flightweight, oxygen/hydrogen aerospike rocket thrust chamber was disassembled and partially repaired. A description is presented of the aerospike chamber configuration and of the damage it had suffered. Techniques for aerospike thrust chamber repair were developed, and are described, covering repair procedures for lightweight tubular nozzles, titanium thrust structures, and copper channel combustors. Effort was terminated prior to completion of the repairs and conduct of a planned hot fire test program when it was found that the copper alloy walls of many of the thrust chamber's 24 combustors had been degraded in strength and ductility during the initial fabrication of the thrust chamber. The degradation is discussed and traced to a reaction between oxygen and/or oxides diffused into the copper alloy during fabrication processes and the hydrogen utilized as a brazing furnace atmosphere during the initial assembly operation on many of the combustors. The effects of the H2/O2 reaction within the copper alloy are described.

Campbell, J., Jr.↗

NASA NTRS1976

Brayton-cycle heat exchanger technology program

The following five tasks designed to advance this development of heat exchanger systems for close loop Brayton cycle power systems are presented: (1) heat transfer and pressure drop data for a finned tubular heat transfer matrix. The tubes are arranged in a triangular array with copper stainless steel laminate strips helically wound on the tubes to form a disk fin geometry; (2) the development of a modularized waste heat exchanger. Means to provide verified double containment are described; (3) the design, fabrication, and test of compact plate fin heat exchangers representative of full scale Brayton cycle recuperators; (4) the analysis and design of bellows suitable for operation at 1600 F and 200 psia for 1,000 cycles and 50,000 hours creep life; and (5) screening tests used to select a low cost braze alloy with the desirable attributes of a gold base alloy. A total of 22 different alloys were investigated; the final selection was Nicrobraz 30.

Killackey, J. J.↗

NASA NTRS1976

High reliability cathode heaters for ion thrusters

A number of space missions have been proposed which will utilize 30-cm mercury bombardment ion thrusters and also will require a large number of thruster restarts. A test program was carried out to determine thermal cycle life of several different cathode heater designs. Plasma/flame sprayed heaters and swaged type heaters were tested. Four of the five plasma/flame sprayed heaters tested failed in a comparatively short time. Four tantalum swaged heaters that were brazed to the tantalum cathode tube were successfully tested and met the goals that were set at the start of the test.

Mueller, L. A.↗

NASA NTRS1977

Production

The manufacturing tasks and life support systems that would pertain to a space habitat located at the Lagrange equilibrium point L5 are examined. Aluminum and titanium could be obtained from the moon minerals anorthosite and ilmenite, respectively. Although hydrogen required for purifying the metals would probably have to be imported from earth, the L5 project should have abundant energy for the processing. Methods of utilizing various glasses and ceramics common in the moon are being investigated. Manufacturing processes, such as capillary brazing, ceramic melting, laser welding, and other techniques, are considered with respect to their suitability at zero gravity and in a vacuum. With regard to life support, high-intensity agriculture is discussed, with attention to the use of a mirror system to provide continuous illumination.

Hibbs, A. R.↗

NASA NTRS1978

Effects of fabrication and joining processes on compressive strength of boron/aluminum and borsic/aluminum structural panels

Processes for forming and joining boron/aluminum and borsic/aluminum to themselves and to titanium alloys were studied. Composite skin and titanium skin panels were joined to composite stringers by high strength bolts, by spotwelding, by diffusion bonding, by adhesive bonding, or by brazing. The effects of the fabrication and joining processes on panel compressive strengths were discussed. Predicted buckling loads were compared with experimental data.

Royster, D. M.↗

NASA NTRS1980

A tool for installation and removal of cylindrical baffles

Simple tool based on principle of automobile oil wrench slips over cylindrical thread-on baffle to install or remove it from baffle assembly. Tool consists of curled metal sheet brazed onto handgrip. Handgrip is adapted to be driven by wrench, ratchet, extension, torque wrench, or some other convenient tool. Clockwise twist of handgrip, tightens metal sheet around baffle to advance it into threaded joint. Counterclockwise twist loosens sheet for repositioning or tool removal.

Pessin, R.↗

NASA NTRS1979

Composite seal for turbomachinery

A gas path seal suitable for use with a turbine engine or compressor is provided. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor protects the rotor blades. A compliant backing surrounds the shroud. The backing may be made of corrugated sheets or the like with adjacent layers having off-set corrugations, with axes of the folds parallel to the rotor axis. The sheets may be bonded together at points of contact by brazing, welding or the like. In another embodiment a compliant material is covered with a thin ductile layer. A mounting fixture surrounds the backing.

Bill, R. C.↗

NASA NTRS1979

Evaluation of a Brayton cycle recuperator after 21,000 hours of ground testing

A metallographic examination was conducted on a Brayton cycle recuperator and associated ducting after 21,000 hours of ground testing in air. At the hot (turbine) end, the recuperator operated at a nominal temperature of 675 C. The type 347 stainless-steel recuperator performed satisfactorily in the ground test even though the primary working fluid leaked to the atmosphere periodically. The leakage path was located at plate-bar braze joints which cracked as a result of thermal stresses. The welded type 347 stainless steel ducting a type 347/Hastelloy X bellows survived the ground test with no apparent loss of ductility or integrity. Some apparent aging embrittlement was observed in the Hastelloy X ducting but the serviceability was not affected.

Moore, T. J.↗

NASA NTRS1977

Ceramic/metal seals

Design criteria are discussed for a hermetic seal capable of withstanding the 450 C operating temperature of a lithium-metal sulfide battery system. A mechanical seal consisting of two high strength alloy metal sleeves welded or brazed to a conductor assembly and pressed onto a ceramic is described. The conductor center passes through the ceramic but is not sealed to it. The seal is effected on the outside of the taper where the tubular part is pressed down over and makes contact.

Bredbenner, A. M.↗

NASA NTRS1977

Cell cases for Discus 3

Batteries designed for the defense satellite communications system were modified to meet increased power requirements. A stainless steel case for the cell, approximately 4 inches wide, 4 1/2 inches high and 1 inch thick, with a weld down a narrow edge, has 12 mil 304-L stainless steel side walls and a 19 mil 304-L stainless bottom. A dip-brazed 60-61 aluminum retainer is electrically separated from the steel case by 15 mils of potting compound. The thickness of the compound varies from 10 to 20 mils, except at the bottom, where it is 20 to 30 mils thick. Pressure test results are discussed.

Thierfelder, H.↗

NASA NTRS1979

The evolution of apparatus for materials processing on Skylab

The following topics are discussed: (1) the inception of space processing; (2) earth-based experimental activities prior to Skylab (drop tower and research aircraft experiments); (3) preliminary experiments in space (Apollo and sounding rocket experiments); and (4) Skylab experimental facilities. Apparatus for contained materials processing; for brazing in space; and containerless processing are presented and discussed. The Skylab materials processing system and miscellaneous design considerations are also discussed.

Source record↗

NASA NTRS1979

Metallurgical processing

The metallurgical processing experiments on Skylab were chosen to: (1) elucidate the unknown effects of a low gravity environment on certain processes; (2) determine to what extent nongravitational driven flows operate in the processes; and (3) explore the possibilities of containerless solidification. Welding and brazing experiments were conducted to provide an understanding of solidification mechanics in a weightless environment.

Source record↗

NASA NTRS1978

Ceramic-metal seals for advanced battery systems

The search for materials which are electrochemically compatible with the lithium sulfur and sodium sulfur systems is discussed. The use liquid or braze alloys, titanium hydrite coatings, and tungsten yttria for bonding beryllium with ceramic is examined.

Reed, L.↗

NASA NTRS1980

Easily-assembled helical heater

Rugged, compact heater is made from 0.1 mm diameter Inconel wire (125 ohms per meter). Heating element is enclosed in PTFE heat-shrink sleeve. Ends of coal pass through small ceramic spools and are silver-brazed to lead wires. Junctions are potted in epoxy or silicon and covered with crimp sleeves and heat-shrink tubing.

Pizzeck, D. E.↗

NASA NTRS1980

Detecting contaminants by ultraviolet photography

Relatively high ultraviolet absorptivity of most organics as compared to metal is suggested as basis for detecting traces of contamination. By photographing metal surface in ultraviolet light, contaminants that might otherwise interfere with adhesion of surface coatings, or with welding or brazing, could be detected and removed. Real time monitoring of cleaning process is also possible if ultraviolet sensitive television camera is used instead of photographic film.

Neiswander, D. W.↗

NASA NTRS1980

Test fittings for dimensionally critical tubes

Method using lightweight fitting protects tubes and tube stubs during testing and through to final welding. Fitting does not interfere with final welding or brazing like temporary test fittings, and is not heavy like machined-on integral fittings with face-seal 0-rings. Fitting approach is adaptable to many types of components, including valves, transducers, and filters.

Hagler, R.↗

NASA NTRS1981

Reduced gravity favors columnar crystal growth

In zero gravity, alined columnar microstructures form at expense of equiaxed growth. Preferential crystal growth occurs in solidification chamber consisting of semicylindrical copper chill block brazed to stainless steel top plate. Method is best utilized in castings where directional dependence of physical properties is beneficial, as in turbine blades.

Kattamis, T. Z.↗