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Appel, M. A.

Publications and source records attributed to Appel, M. A..

8 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Iridium-coated rhenium thrusters by CVD

Operation of spacecraft thrusters at increased temperature reduces propellant requirements. Inasmuch as propellant comprises the bulk of a satellite's mass, even a small percentage reduction makes possible a significant enhancement of the mission in terms of increased payload. Because of its excellent high temperature strength, rhenium is often the structural material of choice. It can be fabricated into free-standing shapes by chemical vapor deposition (CVD) onto an expendable mandrel. What rhenium lacks is oxidation resistance, but this can be provided by a coating of iridium, also by CVD. This paper describes the process used by Ultramet to fabricate 22-N (5-lbf) and, more recently, 445-N (100-lbf) Ir/Re thrusters; characterizes the CVD-deposited materials; and summarizes the materials effects of firing these thrusters. Optimal propellant mixture ratios can be employed because the materials withstand an oxidizing environment up to the melting temperature of iridium, 2400 C (4350 F).

Harding, J. T.↗
NASA NTRS1984

Rhenium Prevents Corrosion

Rhenium layer inside carbon-composite thrust chamber prevents corrosion when liquid fluorine/hydrazine rocket engine is fired. Liner also eliminates erosion of solid propellant carbon nozzels.

Appel, M. A.↗
NASA NTRS1984

High-temperature gaseous oxygen/hydrogen thrusters for space station

Efforts to determine the critical technologies necessary for the development of a high-temperature GO2/GH2 thruster are reviewed, for space station applications. Two types of thrust chambers are evaluated: one operable at high temperature and the other incorporating regenerative cooling. The high temperature chamber made of rhenium requires minimum cooling of the chamber wall, however, an oxidation barrier should be incorporated to prevent the rhenium thruster from readily oxidizing. The use of rhenium brought about a lower cost, lower weight, and simplicity of fabrication. The igniter-injector, the chamber, the test facility, and the test program are discussed. It is found that an obtained flow split of 58/42 increased the thruster performance from 3893 N-s/Kg to 4030 N-s/Kg for the same chamber pressure and overall mixture ratio. An increase in performance is also observed when the core mixture ratio is lowered. The thruster was tested for 1.9 hrs with no well degradation.

Dowdy, M. W.↗
NASA NTRS1983

Liquid fluorine/hydrazine rhenium thruster update

The status of a fluorine/hydrazine thruster development program is discussed. A solid rhenium metal sea-level thrust chamber was successfully fabricated and tested for a total run duration of 1075 s with 17 starts. Rhenium fabrication methods are discussed. A test program was conducted to evaluate performance and chamber cooling. Acceptable performance was reached and cooling was adequate. A flight-type injector was fabricated that achieved an average extrapolated performance value of 3608 N-s/kg (368 lbf-s/lbm). Altitude thrust chambers were fabricated. One chamber incorporates a rhenium combustor and nozzle with an area ratio of 15:1, and a columbium nozzle extension with area ratios from 15:1 to 60:1. The other chamber was fabricated completely with a carbon/carbon composite. Because of the attributes of rhenium for use in high-temperature applications, a program to provide the materials and processes technology needed to reliably fabricate and/or repair vapor-deposited rhenium parts of relatively large size and complex shape is recommended.

Appel, M. A.↗
NASA NTRS1981

Aeosol lasts up to six minutes

Simple aerosol generator catalytically converts hydrogen peroxide to super-heated steam and then mixes steam with dye. Highly visible mist lasts for 6 minutes and can be used to study aerodynamic turbulence. Method does not depend on formation of ice crystals at cold high altitudes and is environmentally safe.

Appel, M. A.↗
NASA NTRS1980

Technology status of a liquid fluorine-hydrazine rocket engine for a planetary spacecraft propulsion system

This paper discusses the current status of a fluorine-hydrazine rocket engine development program. Incorporation of a thin rhenium inner liner successfully eliminated corrosion of the carbon/carbon composite thrust chamber wall experienced during a previous test program. The results of hot-fire tests utilizing reworked and new injectors which provide increased fuel film cooling showed that thrust chamber head-end temperatures could be maintained at an acceptable level. As expected, the accompanying specific impulse performance loss requires optimizing the amount of film cooling to minimize the loss. The efforts to refine the rhenium liner vapor deposition process culminated in a carbon/carbon composite thrust chamber total test duration of 1008 seconds. Tasks presently in process include: (1) fabrication of two carbon/carbon composite thrust chambers incorporating 60:1 expansion ratio nozzles; (2) injector tests to optimize performance and cooling; (3) additional refinements to the rhenium lining process; and (4) fabrication and test of a freestanding rhenium thrust chamber.

Appel, M. A.↗
NASA NTRS1980

Fluorine-Hydrazine Propulsion Technology update

The current status of the fluorine hydrazine propulsion system development is discussed. Progress on the components, rocket engine, and system design is presented. A detailed look at a fluorine hydrazine system as a potential propulsion option for the Galileo Project (Jupiter orbiter) is delineated and the results of safety and technical reviews which were accomplished to verify the feasibility of this option are summarized.

Bond, D. L.↗