Richard D. Rovang

Testing of a Liquid Metal Carbon‐Carbon Heat Pipe

Proof‐of‐concept testing of a potassium‐filled, carbon‐carbon (C–C) heat pipe with integrally woven fins has been completed. The objectives of these tests were to verify mechanical stability of the pipe through multiple thermal cycles and to assess heat pipe performance. The heat pipe was operated for 11 h, starting at ambient temperature with the potassium working fluid in a frozen state. Smooth transition to steady‐state conditions was achieved; however, maximum power was limited by the electrical heater capability. Heat pipe output power, as measured by a water calorimeter, was 300 W at 700 K, which represents approximately 50% of the maximum design power. Additional testing at higher power levels and temperatures are planned. Posttest inspection of the heat pipe showed the C‐C structure to be in excellent condition after eight thermal cycles from ambient temperature. No evidence of liner debonding or deformation was observed and containment of potassium within the niobium‐1% zirconium (Nb‐lZr) boundar...

Carbon‐carbon heat pipe assembly

A progress review of current efforts to develop a high performance, carbon‐carbon, potassium heat pipe is presented. The heat pipe architecture consisting of the carbon‐carbon structural support tube, metallic liner, wick, end caps, and fill tubes is described. Tests and analysis performed to select the final design are also discussed. These include wick selection, based on heat pipe performance modeling and materials considerations, and braze alloy selection supported by wettability, stability, and strength testing. The final architecture selected consists of a carbon‐carbon tube with 2.5 cm integrally woven fins, silver‐based braze, Nb‐1% Zr liner, perforated foil wick, end caps, and fill tubes. All these elements have been fabricated and assembly into final test articles initiated. A heat pipe cleaning and filling method which utilizes a potassium flow‐through process, with intermediate soaking periods to remove as much free oxygen and other contaminants as possible from the system prior to sealing, wa...

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.

A near-term dynamic isotope power system for the space exploration initiative

The development of a modular, closed Brayton cycle (CBC) dynamic isotope power system (DIPS) for early deployment within the Space Exploration Initiative is the current focus of the U.S. Department of Energy sponsored DIPS Demonstration Program. The work is currently focused on the development of a standardized 2.5‐kWe portable generator for multiple applications on the lunar or Martian surface. The DIPS is based on the flight qualified, plutonium‐fueled general purpose heat source (GPHS) modules flown in the Galileo and Ulysses radioisotope thermoelectric generators (RTGs), and on the CBC power conversion technology demonstrated in previous government programs. An examination of the current planning for the First Lunar Outpost (FLO) was completed, which included both power requirements and lunar outpost configurations under development by NASA. Applications pertinent to DIPS were identified, and a technology roadmap designed to deliver two 2.5‐kWe portable DIPS generators for launch late in 1999 was developed.The development of a modular, closed Brayton cycle (CBC) dynamic isotope power system (DIPS) for early deployment within the Space Exploration Initiative is the current focus of the U.S. Department of Energy sponsored DIPS Demonstration Program. The work is currently focused on the development of a standardized 2.5‐kWe portable generator for multiple applications on the lunar or Martian surface. The DIPS is based on the flight qualified, plutonium‐fueled general purpose heat source (GPHS) modules flown in the Galileo and Ulysses radioisotope thermoelectric generators (RTGs), and on the CBC power conversion technology demonstrated in previous government programs. An examination of the current planning for the First Lunar Outpost (FLO) was completed, which included both power requirements and lunar outpost configurations under development by NASA. Applications pertinent to DIPS were identified, and a technology roadmap designed to deliver two 2.5‐kWe portable DIPS generators for launch late in 1999 was deve...

2.5 kWe dynamic isotope power system for the space exploration initiative including an Antarctic demonstration

The current focus of the Dynamic Isotope Power Systems (DIPS) Demonstration Program is 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 the National Aeronautics and Space Administration (NASA). Included among these are surface rovers for both short and extended duration missions, remote power to science packages, and backup to central base power. Several power levels were investigated to determine the optimum level for the identified applications. Operational concerns were of a primary concern. Recent work focused on refining the 2.5‐kWe design to assure compatibility with the Martian environment while imposing only a minor mass penalty on Lunar operations. A plan and cycle schematic were generated for an early demonstration of a prototypic isotope powered Brayton system using the Antarctic as the test bed. This plan included a schedule and cost and a determination of the impact...

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 developed under the NASA Civil Spqce 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% 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.

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.

A Potassium Rankine Multimegawatt Nuclear Electric Propulsion Concept

Multimegawatt (MMW) nuclear electric propulsion (NEP) has been identified as a potentially attractive option for future space exploratory missions [1], [2]. This paper describes a liquid metal cooled reactor, potassium Rankine power system that is being developed by Rockwell International and which is ideally suited to fulfill this application. The key features of the nuclear power system are described and system characteristics are provided for various potential NEP power ranges and operational lifetimes. The results of recent mission studies are then presented to illustrate some of the potential benefits to future space exploration to be gained from high power NEP.

Potassium‐Rankine nuclear electric propulsion for Mars cargo missions

A system study was performed to determine the optimum initial mass to low Earth orbit (IMLEO), trip time, and power requirements for a Mars cargo mission utilizing a nuclear electric propulsion (NEP) spacecraft. The selected architecture consisted of parallel SP‐100 type reactors, potassium‐Rankine power conversion assemblies, and argon ion thrusters. Parametric potassium‐Rankine cycle optimizations were performed to determine the operating state points, radiator area, and mass as a function of power level. NEP specific masses were determined over the anticipated power range, which then allowed missiono ptimizations to be completed, trading off IMLEO, trip time, and power level. These analyses resulted in a 5.5‐MWe power system, 225 tonne IMLEO and a 480‐day outbound trip to Mars.

Liner protected carbon–carbon heat pipe concept

A lightweight, high performance radiator concept using carbon–carbon heat pipes is being developed to support space nuclear power applications, specifically the SP‐100 system. Carbon–carbon has been selected as an outer structural tube member because of its high temperature and strength characteristics; however, this material must be protected from the potassium heat pipe working fluid. A metallic liner approach is being taken to provide this fluid barrier. Feasibility issues associated with this approach include materials compatibility, fabricastion of the thin‐walled liner, bonding the liner to the carbon–carbon tube, mismatch of coefficient of thermal expansion (CTE), carbon diffusion, and end cap closures. To resolve these issues, a series of test coupons have been fabricated and tested, assessing various liner materials, braze alloys, and substrate precursors. These tests will lead to a final heat pipe architecture, material selection, and component assembly.