Low-Leakage Dynamic Seal to Space

A space power-system, turbine-shaft seal capable of restricting the leakage of mercury vapor and of oil to the space environment is described. This seal was designed to permit use of oil-lubricated bearings in the turbine-alternator assembly of a mercury Rankine cycle. In the intended application it is located between the turbine and the adjacent bearing. The seal uses slinger-pump, visco-pump, and molecular-pump elements. The role and limitations of each element are discussed. Test rigs were used to determine the adequacy of each seal element. The significance of the resulting data is discussed. Two additional test rigs were built for evaluation of the complete seal. Leakage rates of less than 1 lb per year were measured. This seal, a part of the SNAP-8 power-conversion system, is believed to be the first successful development of a functional dynamic seal to space.Copyright © 1965 by ASME