Description: The design, construction, and testing of a variety of electrical heaters for small-diameter Subterrene penetrators has been pursued. The incompatibility of refractory materials at the required operating temperatures of ~2000 deg K and the large heat-flux requirements posed the most difflcult design problems. Heat fluxes of up to 2.0 MW/m/sup 2/ were obtained from pyrolytic-graphite radiant heattransfer elements and were as high as 2.5 MW/m/sup 2/ when this type of heater was combined with a lithium heat-pipe assembly. Penetrators using radiant heaters produced both vertical and horizontal holes of 50 mm dia up to lengths of 25 m, whereas holes of up to 64 mm dia and 0.5 m long were produced in basalt and other rock samples in the laboratory. (auth)
Date: February 1, 1974
Creator: Armstrong, P.E.
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