Engineering topics

Rovang, Richard D.

Publications and source records attributed to Rovang, Richard D..

6 records

NASA NTRS1995

Composite heat pipe development status: Development of lightweight prototype carbon-carbon heat pipe with integral fins and metal foil liner

This report discusses development and proof-of-concept testing of a new lightweight carbon-carbon (C-C) space radiator heat pipe, carried out under the NASA Civil Space Technology Initiative (CSTI) High Capacity Power Program. The prototype heat pipe, equipped with a niobium-zirconium foil liner, was filled with potassium working fluid and tested for 11 hours, including startup from ambient temperature with the working fluid initially in the frozen state to near 700 K condenser temperature. Steady-state heat pipe input power during testing was facility limited to about 300 watts. Post test inspection showed the heat pipe to be in excellent condition after eight thermal cycles from ambient to steady-state operating temperature. Utilization of other liner materials and working fluids would greatly extend the spectrum of service temperatures for this technology, with potential applications ranging from small spacecraft heat rejection to aircraft and terrestrial uses.

Juhasz, Albert J.↗

NASA NTRS1994

Carbon-Carbon Heat Pipe Testing and Evaluation

This report discusses development and proof-of-concept testing of a new lightweight carbon-carbon (C-C) space radiator heat pipe developed under the NASA Civil Space Technology Initiative (CSTI) High Capacity Power Program. The heat pipe was filled with potassium working fluid and tested for 11 hours including startup from ambient temperature with the working fluid initially in the frozen state to near 700 K condenser temperature. Steady-state heat pipe input power during testing was facility limited to about 300 watts, representing about 50 percent of the design input power. Post test inspection showed the heat pipe to be in excellent condition after eight thermal cycles from ambient to steady-state operating temperature. Potential applications, ranging from small spacecraft heat rejection to aircraft and terrestrial uses, are discussed.

Juhasz, Albert J.↗

NASA NTRS1992

Fabrication of carbon-carbon heat pipes for space nuclear power applications

Significant advancements have been made in the development of lightweight, high performance, carbon-carbon heat pipes for space nuclear power applications. The subject program has progressed through the concept definition and feasibility analysis stages to the current test article component fabrication and assembly phase. This concept utilizes a carbon-carbon tube with integrally woven fins as the primary structural element and radiative surface, Nb-1Zr liners to contain a potassium working fluid, and welded end caps and fill tubes. Various tests have been performed in the development of suitable liner bonding techniques and in the assessment of material stability.

Rovang, Richard D.↗

NASA NTRS1991

Dynamic Isotope Surface Power Systems

The Dynamic Isotope Power Systems (DIPS) demonstration program, sponsored by the U.S. Department of Energy (DOE) with support funding from the National Aeronautics and Space Administration (NASA), is currently focused on the development of a standardized 2.5 kWe portable generator for multiple applications on the lunar or Martian surface. A variety of potential remote and mobile applications has been identified by NASA including surface rovers for both short and extended duration missions, remote power to science packages, and backup to central base power. Recent work focused on refining the 2.5 kWe design including assessing compatibility with the Martian environment to assure the design is suitable while imposing only a minor mass penalty on lunar operations. Additional work included a study performed to compare the DIPS with regenerative fuel cell systems for lunar mobile and remote power systems. Power requirements were reviewed and a modular system chosen for the comparison. Finally, a plan and cycle schematic were generated for an early demonstration of a prototypic isotope power Brayton system using the Antarctic as the test bed.

Hunt, Maribeth E.↗

NASA NTRS1991

Multimegawatt potassium Rankine power for nuclear electric power

A cermet fueled potassium rankine power system concept has been developed for various power ranges and operating lifetimes. This concept utilizes a single primary lithium loop to transport thermal energy from the reactor to the boiler. Multiple, independent potassium loops are employed to achieve the required reliability of 99 percent. The potassium loops are two phase systems which expand heated potassium vapor through multistage turboalternators to produce a 10-kV dc electrical output. Condensation occurs by-way-of a shear-flow condenser, producing a 100 percent liquid potassium stream which is pumped back to the boiler. Waste heat is rejected by an advanced carbon-carbon radiator at approximately 1000 K. Overall system efficiencies of 19.3 percent to 20.5 percent were calculated depending on mission life and power level.

Rovang, Richard D.↗

NASA NTRS1991

SP-100 high-temperature advanced radiator development

The development of an advanced radiator concept design meeting SP-100 thermoelectric requirements is reported. Carbon-carbon heat pipes are used to produce this lightweight, high-performance radiator. Two feasibility problems had to be solved to enable the design: the production of a carbon-carbon heat pipe tube with integral fins, and the development of a coating that protects the carbon-carbon substrate from 875-K potassium working fluid. Carbon-carbon tubes with integral fins were successfully produced using a T-300 fiber, an angle interlocking weave architecture, and pitch densification. A barrier coating to protect the inside diameter of these tubes which employed the CVD of niobium over a thin rhenium interlayer was developed. The rhenium interlayer proved to be critical to the success of this coating technique by providing a gradation in the coefficient of thermal expansion, carrying a portion of the induced stress load, improving coating adhesion, and providing a partial carbon diffusion barrier.

Rovang, Richard D.↗