SNAP PROGRAMS, TASKS 2, 3, 5 AND 6 QUARTERLY PROGRESS REPORT No. 2, JANUARY TO MARCH 31, 1960

System Design. A chem-milled outer skin, an improved thermoelectric element adjustment and access plug, a flexible stainless steel-aluminum joint welded via ultrasoric techniques, a flexible hot shoe assembly, and thermal hydrauilc heat dump system were incorporated into the design of the environmental and ground test generators. Materials Analysis. Burnup studies on fuel forms were continued with CeF/sub 3/ and CeO/sub 2/. SiC/sub 2/ appeared to be the most promising addition to CeO/sub 2/. Tests showed that the Allegheny Ludlum alloy S-818 alloy is resistant to attack by CeO/sub 2/ and CeF/sub 3/, but is attacked by Ce metal. Hazards Analysis Analyses of launch abort impact zones for the open core and of aerodynamic burnup for near orbital injection on two types of Mo fuel cores continued. Manufacturing. Fabrication and assembly of the first electrically heated generator was completed. System and Component Test. It was found that lead telluride couples increased in resistivitg after heating to l000 deg F and masked resistivity changes because of radiation. Inconel X cores were heated to approximately 15O0 deg and impacted on either granite or water tatgets. All of thr cerium-metal loaded cores ruptured. Cores loaded with lavite pellets were recovered intact. Heat transfer mockup teats were completed with a revised twolayer stainless steel heat shield. SNAP-III. The 3MlG3 thermoelectric generator was repaired and parametric testing resumed. The power output of ths second SNAP-III unit was measured and proof of thermoelectric generator operation for at least a period of a year wae demonstrated. SNAP-III. The performance characteristics of a second SHAP-IIIA generator of completely new design were only marginally better than the original. Tests were performed on metal-encased and ribbon-emitter types of tubes. A wire-wound ceramic heater and a tungsten-wire radiation heater were fabricated and tested. Work wse continued on the molybdenum collector used in conjunction with a Type B impregnated tungsten emitter. Low Power Thermionic Generator. Work on improved heat transfer between the emitter holder and the heat source revealed that a layer of Mo powder between the two surfaces gives a lower film drop and more consistent results. Creep tests on sapphire spacers (Al/sub 2/O/sub 3/) showed that some creep takes place above 1200 deg C, and above 1300 deg C, the strength of the sapphire falls off rapidly. A device for measuring the thermal expansion of CeO/ sub 2/ fuel pellets while in a hot cell was fabricated. Thermoelectric 2- to 5- Watt Generator. Altitude chamber tests of the generators were successfully completed. A shock-wave test proved the capsule can survive missile propellant detonation. Power output versus time plots were developed for both the cerium- and polonium-fueled systems. (M.C.G.