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The purpose of this paper is to discuss the status of refractory metal thermocouples and recent efforts toward solving the problems associated with thermoelements, insulators, and sheathing in high temperature applications. Because of the continuing research in this field and the rapid advance of the state of the art, the author cautions that all concerned with specific applications should maintain contact with these programs so that variables associated with their problems may be considered in prescribing proper use of these elements.

System level design studies of space applications ranging in power from 77 kWt to 200 MWt have indicated no practical limit to the thermal power that can be reliably generated by a space reactor system based on the technologies being developed in the SP-100 program. These technologies include uranium nitride fuel, PWC-11/rhenium bonded fuel cladding, PWC-11 structural material for the lithium coolant boundary, electromagnetic coolant pumps, safety and reactivity control drive mechanisms, sensors, shielding materials, etc. at operating temperatures up to 1400K. The physical arrangements and characteristics of the nuclear reactor materials are described. The physical size of components and the arrangement of components change, but the basic technologies required are generally the same, irrespective of the total power output.

Recent Generic Flight System (GFS) updates have necessitated revisions in the initial startup and restart control strategies. The design changes that have had the most impact on the control strategies are the addition of the Auxiliary Cooling and Thaw (ACT) system for preheating the lithium filled components, changes in the reactivity worths of the reflectors and safety-rods such that initial cold criticality is achieved with only a small amount of reflector movement following the withdrawal of the safety-rods, and the removal of the scram function from the reflectors. Revised control and operating strategies have been developed and tested using the SP-100 dynamic simulation model, ARIES-GFS. The change in the total reactivity worths of the reflectors and safety-rods has eliminated the need for the use of fast and slow reflector drive speeds during the initial on-orbit approach to criticality.

To facilitate the development of the Space Reactor Power System (SRPS) controller, a rapid prototyping and multi-phased development methodology is being utilized. The rapid prototyping environment used in the development models both the controller and the system being controlled. Since the validation of the SRPS control strategies is a long lead activity to ensure the required safety and control features, the SRPS controller development is carried out in phases, starting with normal modes of operation and followed by transient and off-normal modes. In every phase, the rapid prototyping of the control strategies is used (1) to establish well-defined controller requirements, (2) to perform fast identification of changes and refinement of the strategies, and (3) to conduct in-phase correction and optimization of the strategy and component development.

An acceleration of metal replacement to reinforce thermoplastic composites is positioned to impact the transportation markets through a joint venture between PPG Industries and GE Plastics, called AZDEL, Inc. The strength of both companies' strong technological base in glass and engineering thermoplastic resins is the key. The resulting long continuous glass thermoplastic composites have high strength to weight ratios, provide tough durable products, facilitate combining functions in design, and because of its high speed manufacturing processes, is cost effective. In addition, these materials can be post fabricated during the assembly phase, easily repaired and conveniently recycled. Value added secondary operations for both the captive or custom molders provide another avenue for cost reductions.

The approach that was utilized to start up and requalify manufacture of the thermoelectric unicouple devices for the Cassini RTG (Radioisotope Thermoelectric Generator) program are described in this paper. Key elements involved in this effort were: engineering review of specifications; training of operators; manufacturing product verification runs; and management review of results. Appropriately, issues involved in activating a fabrication process that has been idle for nearly a decade, such as upgrading equipment, adhering to updated environmental, health, and safety requirements, or approving new vendors, are also addressed. The cumulative results of the startup activities have verified that a production line for this type of device can be reopened successfully.

Aircraft starting and generating systems heretofore have been largely the result of joining together available components. Recent studies have demonstrated that substantial benefits in weight, cost, size, and performance may be realized through a total system approach. This paper identifies the types of information required, and the methods of system analysis employed, to design an optimized system.

Previous studies had demonstrated the economic and technical feasibility of producing high-quality forgings for aircraft turbine engine parts from hot-isostatically pressed (HIP) Rene 95 powder billets. The present program was aimed at developing a production practice for making HIP + forged turbine discs. The major goal was improved product fabricability and reliability with minimum cost. The program was conducted using argon atomized Rene 95 powder. Experimental studies were conducted to evaluate the effect of powder characteristics, HIP parameters, preform design, and forging conditions on forgeability, microstructure, and mechanical properties. The results of these studies were incorporated into a pilot production run in which 10 disc forgings were made and evaluated. The selected process involved the consolidation of -60 mesh powder to full density by hot-isostatic pressing at a temperature above the γ' solvus temperature.

Initial preliminary development phases of two distinct SP-100 control drive assembly bearing test programs were successfully completed at elevated temperature in vacuum. The first was for the reflector drive line spherical self-aligning bearings. Each bearing consisted of a carbon-graphite ball mounted on an aluminum oxide-coated Ta-10%W shaft, captured by an aluminum oxide-coated Ta-10%W socket. One set of these bearings was exposed to temperatures up to 1180K (1665°F) at 1.33x10-6 Pa (1x10-8 torr) and subjected to 38000 cycles of motion. Friction coefficients were found to be between 0.11 and 0.25 over the full range of operation. Overall performance of the bearings was excellent, with only slight wear observed. The second test program was for the safety rod slider bearing. Zirconium carbide coated Nb-1%Zr bearing pads were stroked inside a molybdenum tube at temperatures up to 1422K (2100°F) at ∼1.33x10-6 Pa with a normal load of 1.02 Kg between each sliding surface.