Expert Systems Applied to Spacecraft Fire Safety Unclad Prepared for Lewis Research Center under Purchase Order C-32000-m
SUMMARY E x p e r t systems a r e p r o b l e m-s o l v i n g programs t h a t combine a knowledge base and a r e a s o n i n g mechanism t o s i m u l a t e a human " e x p e r t. " The development o f an e x p e r t system t o manage f i r e s a f e t y i n s p a c e c r a f t , i n p a r t i c u l a r t h e NASA Space S t a t i o n Freedom, i s d i f f i c u l t b u t c l e a r l y advantageous i n t h e l o n g-t e r m. The r e p o r t d i s c u s s e s some needs i n l o w-g r a v i t y f l a m m a b i l i t y c h a r a c t e r i s t i c s , v e n t i
Safety considerations in the design of manned spaceflight hardware
Some of the significant potential hazards affecting NASA's planned space-flight initiatives are discussed together with the safety design strategies they mandate. Attention is given to the role played by NASA's newly centralized safety organization during the design of manned space flight hardware and software. Prompt-effect/physical hazards include fire, explosions and depressurization, and natural and man-made space debris. Delayed-effect hazards include radiation and toxic contamination, microgravity effects, crew illness and injury, and isolation. Safety design considerations for software and hypersonic transatmospheric vehicles are evaluated.
Evolution of carbide precipitates in Hastelloy N joints during welding and post weld heat treatment
Abstract The effects of welding and post weld heat treatment (PWHT) on the morphology, composition and lattice parameter of the precipitates in the welding joints of Hastelloy N alloy have been investigated. Joint samples were prepared using a gas tungsten arc welding process with ERNiMo-2 fillers, and then solid-solution treated at 1100 °C for 20 min. After welding, eutectic M6C carbides can be observed in the heat affected zones (HAZ) and weld zones (WZ). These eutectic M6C carbides become spheroidized during the following PWHT. The concentration of Si decreases during the transformation from the primary ones to eutectic ones, and then increases during the spheroidizing process. The total concentration of Si + Cr in M6C carbides remains stable during welding and PWHT. At the same time, the heat leads to the outward diffusion of Mo from the M6C carbides, which results in a decrease of the lattice parameter.