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Luedke, E. E.

Publications and source records attributed to Luedke, E. E..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Heat pipe life and processing study

The merit of adding water to the reflux charge in chemically and solvent cleaned aluminum/slab wick/ammonia heat pipes was evaluated. The effect of gas in the performance of three heat pipe thermal control systems was found significant in simple heat pipes, less significant in a modified simple heat pipe model with a short wickless pipe section. Use of gas data for the worst and best heat pipes of the matrix in a variable conductance heat pipe model showed a 3 C increase in the source temperature at full on condition after 20 and 246 years, respectively.

Antoniuk, D.↗
NASA NTRS1978

CTS-type variable conductance heat pipes for SEP FM/PPU

The development effort for, and the fabrication and testing of, six CTS-type variable conductance heat pipes is described. The heat pipes are constructed of stainless steel, use methanol as a working fluid, and a nitrogen/helium mixture as the control gas. The wicking structure consists of interior wall grooves, a metal-felt diametral slab wick, and two wire-mesh arteries. The heat pipes are used to cool two Functional Model/Power Processing Units in a Solar Electric Propulsion prototype BIMOD thruster subsystem assembly. The Power Processing Units convert the electric power from a spacecraft solar array system to the voltages required to operate the electric thrusters which are part of the BIMOD assembly.

Antoniuk, D.↗
NASA NTRS1978

Extended Development of Variable Conductance Heat Pipes

A high-capacity vapor-modulated heat pipe was designed and tested. In 1977, a program was undertaken to use the aforementioned heat pipe to study protection from freezing-point failure, increase control sensitivity, and transient behavior under a wide range of operating conditions in order to determine the full performance potential of the heat pipe. A new concept, based on the vapor-induced-dry-out principle, was developed for passive feedback temperature control as a heat pipe diode. This report documents this work and describes: (1) the experimental and theoretical investigation of the performance of the vapor-modulated heat pipe; and (2) the design, fabrication and test of the heat pipe diode.

Antoniuk, D.↗
NASA NTRS1978

Thermal radiative properties of solar sail film materials

Techniques have been developed for controlling the temperature and enhancing the performance of metallized, ultrathin polymer film used as the sail material for the proposed Halley's Comet rendezvous solar sail vehicle. The coating technology development is described whereby film emissivity is increased sufficiently on one side to a point where the sail, in its cranking orbit, could go to a heliocentric distance of 0.25 AU and still operate within the temperature limits of the basic film material. This capability resulted in significant improvement in several mission performance parameters; e.g., a lengthened launch period through increased vehicle performance and more latitude in the selection of basic film candidates.

Rowe, W. M.↗
NASA NTRS1976

Flight data analysis and further development of variable-conductance heat pipes

The work focuses on the mathematical modeling of three critical mechanisms of heat-pipe operation: (1) the effect that excess liquid has on heat-pipe performance; (2) the calculation of the dryout limit of circumferential grooves; (3) an efficient mathematical model for the calculation of the viscous-inertial interaction in the vapor flow. These mathematical models are incorporated in the computer program GRADE II, which is described.

Eninger, J. E.↗
NASA NTRS1976

Flight data analysis and further development of variable-conductance heat pipes

Continuing efforts in large gains in heat-pipe performance are reported. It was found that gas-controlled variable-conductance heat pipes can perform reliably for long periods in space and effectively provide temperature stabilization for spacecraft electronics. A solution was formulated that allows the control gas to vent through arterial heat-pipe walls, thus eliminating the problem of arterial failure under load, due to trace impurities of noncondensable gas trapped in an arterial bubble during priming. This solution functions well in zero gravity. Another solution was found that allows priming at a much lower fluid charge. A heat pipe with high capacity, with close temperature control of the heat source and independent of large variations in sink temperature was fabricated.

Enginer, J. E.↗
NASA NTRS1976

Heat Pipe Materials Compatibility

An experimental program to evaluate noncondensable gas generation in ammonia heat pipes was completed. A total of 37 heat pipes made of aluminum, stainless steel and combinations of these materials were processed by various techniques, operated at different temperatures and tested at low temperature to quantitatively determine gas generation rates. In order of increasing stability are aluminum/stainless combination, all aluminum and all stainless heat pipes. One interesting result is the identification of intentionally introduced water in the ammonia during a reflux step as a means of surface passivation to reduce gas generation in stainless-steel/aluminum heat pipes.

Eninger, J. E.↗
NASA NTRS1975

Vapor-modulated heat pipe report. Flight data analysis and further development of variable-conductance heat pipes

The design and testing of a heat pipe for spacecraft application is presented. The application in mind calls for heat loads up to 20 watts, a set-point temperature of 294K, and a sink that varies from -220K to nearly as high as the set-point. The overall heat pipe length is 137 cm. Two basically different mechanisms of achieving variable conductance in the pipe by vapor-flow throttling were studied. In one, the thermal resistance between the heat source and sink is due to a saturation-temperature drop corresponding to the vapor-pressure drop developed across the valve. In the other, the pressure difference across the valve induces capillary groove and wick dry out in an evaporation region, and thus results in an increased thermal resistance. This mechanism was selected for fabrication and testing. The pipe is a stainless-steel/methanol two-heat-pipe system. Results are presented and discussed. Engineering drawings and specifications of the pipe are shown.

Eninger, J. E.↗
NASA NTRS1973

Effects of cesium ions and cesium vapor on selected ATS-F samples

Thermal control coating samples were subjected to cesium ion beam and vapor exposures. Degradation of solar absorptance and infrared emittance were measured. Solar cells and samples selected from surfaces on the ATS-F spacecraft likely to experience ion or vapor impingement were bombarded by 10-volt cesium ions. Other samples were subjected to high levels of cesium vapor. Aluminum and white paint were backsputtered by 550-volt cesium ions onto selected samples. For direct bombardment, the threshold for ion-induced property changes was above five-thousand trillion ions/sq cm. With material sputtered from a 450-sq cm target onto samples 36 cm distant, the threshold for noticeable effects was above 5 times 10 to the 17-th power ions/sq cm.

Kemp, R. F.↗
NASA NTRS1973

Electrostatic propulsion beam divergence effects on spacecraft surfaces, volume 3

Tests were conducted to determine the effects of electrostatic propulsion beam divergence effects on spacecraft surfaces. The subjects discussed are: (1) sensitive surfaces on the ATS 6 spacecraft, (2) the cesium ion source and testing facility, (3) cesium ion effects on thermophysical properties, and (4) simulated charge-exchange ion exposure. The compatibility of the ATS 6 ion engine experiment with the engineering subsystems and other experiments aboard the ATS 6 spacecraft was analyzed.

Kemp, R. F.↗
NASA NTRS1972

Damage of thermal control coating properties by energetic mercury ion bombardment.

The thermophysical properties (absorptance and emittance) of five commonly used spacecraft thermal control coatings have been measured in situ after exposure to 1.5 and 3 KeV mercury ions. Sample temperature was varied from 20 to 150 C. The results showed negligible change in emittance but significant degradation of the solar absorptance at fluences of 10 to the 17th power ions/sq cm. Plots of absorptance as a function of ion fluence are presented, along with pre- and post-exposure ex situ spectral absorptance measurements. The widely used Z93 white paint exhibited quantitative degradation from mercury ions similar to that reported by other experimenters for hydrogen and helium ions.

Kelley, L. R.↗
NASA NTRS1972

Effects of electrostatic rocket material deposited on solar cells.

If solar arrays on solar-electric spacecraft protrude into the exhaust hemisphere of the electric thrusters, they will receive fluxes (usually small) of both propellant and accelerator grid atoms. Unlike propellants, grid materials have low vapor pressures and will not reevaporate. An analysis is presented of degradation in the optical, thermal, and electrical performance of solar cells resulting from thin deposits of grid material (aluminum and molybdenum) on various array surfaces. The classical optical theory of thin films, heat balance equations, and a typical relationship for solar cell efficiency vs temperature are used to compute curves showing optical properties, temperature, and power output as functions of film thickness. The results compare favorably with available experimental data. It is shown that a few monolayers of metal deposition on the illuminated surface will seriously degrade cell performance. A means of estimating the arrival rate of these materials is provided.

Kemp, R. F.↗