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.
Joint strength of aluminum ultrasonic soldered under liquidus temperature of Sn–Zn hypereutectic solder
Abstract In order to obtain high-strength aluminum joints, ultrasonic soldering of 1070 aluminum was conducted under liquidus temperature of Sn–Zn hypereutectic solder. A device for ultrasonic soldering was assembled, which propagated ultrasonic vibrations in a direction perpendicular to joining surfaces. This device joined 1070-Al using quasi-melting Sn–Zn hypereutectic solder without using any artificial spacers. The strength of the solder joints was evaluated by tensile tests. The optimum joining conditions were determined, and the effects of solder compositions and soldering temperature on the joint strength and the solder layer thickness were examined. In this ultrasonic soldering process, the highest tensile strength was obtained for the solder joints fabricated at 220 °C for the Sn–23Zn and Sn–40Zn solder compositions. The joint strength was equivalent to that of 1070-Al heat treated at 220 °C. The sound joints were obtained at 300 °C using Sn–82Zn solder, the liquid phase volume fraction of which was theoretically only 0.24. The present work also revealed that the thickness of retained solder layer in the joint after ultrasonic soldering could be estimated. Accordingly, ultrasonic soldering under the liquidus temperature of Sn–Zn hypereutectic solder could be a spacer-free soldering method to obtain high-strength aluminum joints.