Engineering topics

Deininger, William D.

Publications and source records attributed to Deininger, William D..

33 records · Page 2

NASA NTRS1989

Patterning of dispenser cathode surfaces to a controlled porosity

A process to pattern slots approximately 1.25 microns in width into 25-micron-thick W films that have been deposited onto flat or concave surfaces is discussed. A 25-micron-thick W film with a high degree of (100) orientation is chemically vapor deposited (CVD) onto a flat or concave Mo mandrel. A 5-micron-thick Al film is deposited onto the CVD W, followed by 2 microns of photoresist. On concave cathodes, XeCl2 laser ablation or X-ray lithography is used to pattern the photoresist, whereas on flat cathodes deep UV lithography can be used. The patterned photoresist serves as the mask in a Cl ion-beam-assisted etching (IBAE) process to pattern the Al. An alternative process is to deposit Al2O3 films onto the W and pattern the Al2O3 using laser ablation. The W film is then patterned to 3-6-micron slot widths using IBAE + ClF3 with the patterned Al or Al2O3 as the mask. Finally, a sputter deposition step is required to close up the slots to approximately 1 micron. The process described is capable of patterning concave dispenser cathodes to a controlled and precise porosity.

Garner, Charles E.↗

NASA NTRS1988

Arcjet propulsion system for an SP-100 flight experiment

The design and performance of a arcjet nuclear electric propulsion spacecraft, suitable for use in a space reactor power system (SRPS) flight experiment, are outlined. The vehicle design is based on a 92-kW ammonia arcjet system operating at a specific impulse of 1050 s and an efficiency of 45 percent. The arcjet/gimbal system, power processing unit, and propellant feed system are described. A 100-kW SRPS is assumed and the spacecraft mass is baselined at 5250 kg, excluding the propellant and propellant feed system. A radiation/arcjet efflux diagnostics package is included in the performance analysis. This spacecraft, assuming a Shuttle launch from Kennedy Space Center, can perform a 35-deg inclination change and reach a final orbit of 35,860 km with a 120-day trip time, thus providing a four-month active load for the SRPS. Alternatively, a Titan IV launch could provide a mass margin of 120 kg to a 1000km, 58-deg final orbit in 74 days.

Deininger, William D.↗

NASA NTRS1988

Luminal surface fabrication for cardiovascular prostheses

A method is provided for forming a mold surface with microscopic upstanding pillars for molding the inside surface of a vascular prostheses (synthetic blood vessel). The mold article is formed from a quantity of Teflon (polytetrafluoroethylene) which has a polished, flat surface on which a gold film has been sputter deposited. A photoresist layer, which cannot adhere directly to Teflon, adheres to the gold. The photoresist is exposed and developed leaving a sputter resistant mask defining the desired pillar locations, and the resulting workpiece is ion etched to form the pillars in the Teflon. A synthetic blood vessel material is cast against the Teflon mold to form blind recesses on the inside of the synthetic blood vessel, with the recesses being of predetermined uniform cross section and present in a predetermined uniform pattern.

Deininger, William D.↗

NASA NTRS1988

High-Emissivity Coatings For High-Temperature Surfaces

Plasma-sprayed coatings increase cooling by thermal radiation. Coating of zirconium diboride on tungsten or molybdenum increases emissivity of surface to more than 0.6 at 2,000 degree C. Applied by plasma-arc spraying after surface cleaned and roughened to ensure adhesion.

Deininger, William D.↗

NASA NTRS1988

Detailed operating characteristics of a 30-kW ammonia arcjet engine with a contoured nozzle

Detailed experimental investigations were conducted to define the operating characteristics of a 30-kW type, arcjet engine with a contoured nozzle. The experiments were conducted in a fully instrumented facility with the engine mounted on a thrust stand. Engine performance was mapped over a power range of 10.6 to 23.0 kW with a mass flow range of 0.175 to 0.350 g/s. The data is presented in graphical form with the relationships between arc potential, arc current, power, thrust, specific impulse and thrust efficiency presented. This paper provides the first detailed accounting of arcjet operation with a contoured nozzle. Further theoretical and experimental work needs to be done to fully explain many of the features exhibited by the data.

Deininger, William D.↗

NASA NTRS1988

High-power, NH3 arcjet cathode lifetime evaluation experiments and plans

Preliminary experimental investigations were conducted to evaluate the effects of a modified cathode shape on ammonia arcjet engine performance. The experiments were conducted with a contoured nozzle arcjet in a fully-instrumented facility which included a thrust stand. The modified cathode tip had a reduced diameter and more acute conical tip with respect to the baseline cathode design. A uniform 15 percent decrease in arc voltage was demonstrated over a mass flow range of 0.175 to 0.350 g/s. A 4 percent improvement in thrust efficiency was noted at 22.0 kW. Plans for future cathode testing are discussed with the aim of developing a long-life, high-performance arcjet cathode.

Deininger, William D.↗

NASA NTRS1988

Spacecraft and mission design for the SP-100 flight experiment

The design and performance of a spacecraft employing arcjet nuclear electric propulsion, suitable for use in the SP-100 Space Reactor Power System (SRPS) Flight Experiment, are outlined. The vehicle design is based on a 93 kW(e) ammonia arcjet system operating at an experimentally measured specific impulse of 1031 s and an efficiency of 42.3 percent. The arcjet/gimbal assemblies, power conditioning subsystem, propellant feed system, propulsion system thermal control, spacecraft diagnostic instrumentation, and the telemetry requirements are described. A 100 kW(e) SRPS is assumed. The spacecraft mass is baselined at 5675 kg excluding the propellant and propellant feed system. Four mission scenarios are described which are capable of demonstrating the full capability of the SRPS. The missions considered include spacecraft deployment to possible surveillance platform orbits, a spacecraft storage mission, and an orbit raising round trip corresponding to possible orbit transfer vehicle (OTV) missions.

Deininger, William D.↗

NASA NTRS1988

Thermal design improvements for 30kWe arcjet engine

Two thermal design improvements for 30 kWe arcjet engines are described. A ZrB2 high temperature coating was used to increase the surface emissivity of the nozzle radiating surface, enabling lower temperature operation, which should lead to longer nozzle life. The ZrB2-coated engine operated 120 C cooler than the uncoated baseline engine indicating a 30 percent increase in the surface emissivity. An engine design which has fewer active seals than previous designs and operates at lower overall component temperatures is described. The nozzle on the engine operated at 1950 C at 30 kWe while the baseline engine nozzle reached 2000 C at 23 kWe. The back of the engine was more than a factor of two cooler when compared to the baseline engine.

Deininger, William D.↗

NASA NTRS1988

Electrode erosion in steady-state electric propulsion engines

The anode and cathode of a 30 kW class arcjet engine were sectioned and analyzed. This arcjet was operated for a total time of 573 hr at power levels between 25 and 30 kW with ammonia at flow rates of 0.25 and 0.27 gm/s. The accumulated run time was sufficient to clearly establish erosion patterns and their causes. The type of electron emission from various parts of the cathode surface was made clear by scanning electron microscope analysis. A scanning electron microscope was used to study recrystallization on the hot anode surface. These electrodes were made of 2 percent thoriated tungsten and the surface thorium content and gradient perpendicular to the surfaces was determined by quantitative microprobe analysis. The results of this material analysis on the electrodes and recommendations for improving electrode operational life time are presented.

Pivirotto, Thomas J.↗

NASA NTRS1988

Spacecraft and mission design for the SP-100 flight experiment

The design and performance of a spacecraft employing arcjet nuclear-electric propulsion, suitable for use in the SP-100 space-reactor power-system (SRPS) flight experiment, are outlined. The vehicle design is based on a 93-kWe ammonia arcjet system operating at an experimentally measured specific impulse of 1031 sec and an efficiency of 42.3 percent. The arcjet/gimbal assemblies, power conditioning subsystem, propellant feed system, propulsion system thermal control, spacecraft diagnostic instrumentation, and the telemetry requirements are described. A 100-kWe SRPS is assumed. The spacecraft mass is baselined at 5675 kg, excluding the propellant and propellant feed system. Four mission scenarios are described which are capable of demonstrating the full capability of the SRPS.

Deininger, William D.↗

NASA NTRS1987

Hollow cathode plasma source for active spacecraft charge control

A prototype plasma source spacecraft discharge device has been developed to control overall and differential spacecraft surface charging. The plasma source is based on a unique hollow cathode discharge, where the plasma generation process is contained completely within the cathode. This device can be operated on argon, krypton, or xenon and has a rapid cold start time of less than 4 s. The discharge system design includes a spacecraft-discharge/net-charge sensing circuit which provides the ability to measure the polarity, magnitude, pulse shape, and time duration of a discharging event. Ion currents of up to 325 microA and electron currents ranging from 0.02 to 6.0 A have been extracted from the device. In addition, the spacecraft discharge device successfully discharged capacitively biased plates, from as high as + or - 2500 V, to ground potential, and discharged and clamped actively biased plates at +5 V with respect to ground potential during ground simulation testing.

Deininger, William D.↗

NASA NTRS1987

Spacecraft and mission design for the SpaceNuclear PowerSystem Reference Mission

The design and performance of a spacecraft employing arcjet nuclear electric propulsion, suitable for use in the Space Nuclear Power System Reference Mission, are outlined. The vehicle design is based on a 92 kW ammonia arcjet system operating at an I(sp) of 1050 s and an efficiency of 45 percent. The arcjet/gimbal system, power processing unit, and propellant feed-system are described. A 100 kW(e) space nuclear power system is assumed and the spacecraft mass is baselined at 5250 kg excluding the propellant, propellent feed system, and integrated chemical boost engine. A radiation/arcjet efflux diagnostics package is included in the performance analysis. Three mission scenarios are described and are capable of demonstrating the full capability of the space nuclear power source. The missions considered include power system deployment to possible SDI platform orbits and a spacecraft storage mission to an orbit of three times geosynchronous (GEO) with return to GEO corresponding to Delta V's between 7400 m/s, and 7900 m/s. This spacecraft meets the Reference Mission constraint of low developmental risk and is scaleable to power levels projected for future space platforms.

Deininger, William D.↗

NASA NTRS1987

Design and performance of an arcjet nuclear electric propulsion system for a mid-1990's reference mission

The design and performance of an arcjet nuclear-electric-propulsion spacecraft, suitable for use in the Space Nuclear Power System (SNPS) reference mission, are outlined. The vehicle design was based on a 30-kW ammonia arcjet system operating at an Isp of 1050 s and an efficiency of 45 percent. The arcjet/gimbal system, power-processing unit, and propellant-feed system are described. A 100-kWe SNPS was assumed, and the spacecraft mass was baselined at 5250 kg (excluding the propellant-feed system). A radiation/arcjet efflux diagnostics package was included in the performance analysis. This spacecraft, assuming a Shuttle launch from KSC, can perform a 50-deg inclination change and reach a final orbit of 35,860 km with a 120-d trip time providing a 4-mo active load for the SNPS. Alternatively, a Titan IV launch would provide a mass margin of 120 kg to a 10,000-km, 58-deg final orbit in 74 d. This spacecraft meets the reference-mission constraint of low developmental risk, and is scalable to power levels projected for future space platforms.

Deininger, William D.↗

NASA NTRS1987

The design and operating characteristics of an advanced 30-kW ammonia arcjet engine

Experimental investigations were conducted to evaluate the effects of a contoured nozzle and modified cathode shape on ammonia arcjet engine performance. The contoured nozzle performance data were compared to the performance data of an arcjet which had a 38-deg included-angle, conical nozzle. Thrust improvements of up to 10 percent were demonstrated which corresponded to 3 percent improvements in specific impulse and 10 percent improvements in thrust efficiency. Performance characterizations for the modified cathode tip were conducted with the contoured nozzle arcjet. A uniform 15 percent decrease in arc voltage was demonstrated over a mass flow range of 0.175 to 0.350 g/s. A 4 percent improvement in thrust efficiency was noted at 22.0 kW.

Deininger, William D.↗

NASA NTRS1987

Luminal surface fabrication for cardiovascular prostheses

Methodology used for the production of highly ordered surfaces on polytetrafluoroethylene (PTFE) Teflon, for use of this material as a surface layer in small-diameter vascular prostheses, is described. Directed argon-ion beam sputter etching is used to produce highly ordered specific surface morphologies, and photolithographic techniques are used for pattern definition. The methodology also includes surface polishing of the samples, sputter deposition of the intermediary layer of gold to enhance photoresist adhesion and improve pattern resolution, and rotating of the sample to minimize the effects of ion-beam nonuniformity and asymmetry. Use of these techniques resulted in the formation of regular arrays of sharply defined hexagonal pillars with smooth vertical walls and large relief.

Deininger, William D.↗