Noticing the excellent performance of liquid hydrogen-liquid oxygen (LH2/LOX) propulsion system, the Institute of Space & Astronautical Science (ISAS) has started the preliminary study in 1971, and since 1975, full-scale development program of the engine, which has the capability of 7ton thrust in vacuum, has been undertaken. Various development tests of the engine components (thrust chamber, turbopump, gas-generator and turbine spinner etc.) have been conducted at the Noshiro Testing Center of ISAS. Integration tests of the stage, comprised of thrust chamber, turbopump, gas-generator and tank, have been carried out from September through December in 1981 with fairy good results. In the present paper, major features and characteristics of this 7ton engine are summarized.
A series of of tests on the sealing characteristics of a number of gaskets and flanges against the superfluid helium below 2.17°K has been made. Commercially available aluminum Helicoflex with stainless steel and aluminum alloy flanges is tight to the normal liquid helium but leaks at the superfluid temperatures. However copper, silver and indium coated aluminum Helicoflex and Sureket (a gasket made of stai