Boil-off of cryogenic propellants is an issue of concern in any space mission. There could be boil-off of liquid propellants in the cryogenic storage tank, transfer line or in the space vehicle external tank itself due to heat leak. The current insulation technology uses a multilayered thermal protective coating of 304 Stainless Steel and Welded Invar, which allows the propellant to withstand the extreme internal and external temperature variations generated during pre-launch, launch, and flight operations, which does not provide for zero boil-off (ZBO). Usage of a cryocooler to prevent propellant boil-off would potentially reduce the launch costs. Owing to its attractive features like simplicity, compactness and rapid cool-down characteristics, an innovative concept of using Joule-Thomson (JT) cryocoolers for prechilling, densification and ZBO applications of cryogenic propellants is focused upon. The liquid oxygen propellant transfer line at NASA Kennedy Space Center is considered for demonstration of the above concept. Various thermodynamic cycle parameters are optimized for the cryocooler to make the demonstration possible. Cycle optimization is done also taking into account the feasibility to develop some crucial components for the JT cryocooler like a micro channel heat recuperator and cold heads. Current state of developments in the heat exchanger is briefly described. Some advantages of using miniaturized cryocoolers in launch vehicle operations are also discussed.

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