Formidable design problems are encountered in the development of a reciprocating power unit for use in space research programmes. One of the most severe of such problems met with by the Vickers Inc. Division of Sperry Rand Corporation in developing a lightweight hydrogen-oxygen internal combustion engine (shown on the right) concerned the selection of materials for the oxygen injector valve. As this valve, operating at very high speed, handles gaseous oxygen at high temperatures, it must be made of a material that will resist oxidation and also maintain adequate strength and impact characteristics.

Tests were carried out on austenitic stainless steel, a nickel-chomium-molybdenum alloy and 10 per cent rhodium-platinum alloy for the poppet valve face, and on stainless steel, 10 per cent rhodium-platinum and the latter alloy flame-plated with alumina for the valve seat. The best combination was found to be a rhodium-platinum poppet face against a flame-plated rhodium-platinum seat. This combination has endured several hours of operation without leakage or deterioration of the plating surfaces and with good ability to compensate for minor misalignment.