Expandable ice-prevention and cleanliness-preservation (EIP-CP) chambers have been proposed to prevent the accumulation of ice or airborne particles on quick-disconnect (QD) fittings, or on ducts or tubes that contain cryogenic fluids. In the original application for which the EIP-CP chambers were conceived, there is a requirement to be able to disconnect and reconnect the QD fittings in rapid succession. If ice were to form on the fittings by condensation and freezing of airborne water vapor on the cold fitting surfaces, the ice could interfere with proper mating of the fittings, making it necessary to wait an unacceptably long time for the ice to thaw before attempting reconnection. By keeping water vapor away from the cold fitting surfaces, the EIP-CP chambers would prevent accumulation of ice, preserving the ability to reconnect as soon as required.

Basically, the role of an EIP-CP chamber would be to serve as an enclosure for a flow of dry nitrogen gas that would keep ambient air away from QD cryogenic fittings. An EIP-CP chamber would be an inflatable device made of a fabric-like material. The chamber would be attached to an umbilical plate holding a cryogenic QD fitting. The chamber would include inner and outer subchambers that would be inflated with gaseous nitrogen through separate supply tubes. The outer subchamber would resemble a small tire tube. The inner chamber would be perforated on its innermost circle to allow nitrogen to flow onto and around the QD surfaces. When deflated, the EIP-CP would be about 1 in. ( ≈2.5 cm) thick.

When not in use, the EIP-CP would be kept deflated, flat against the umbilical plate. Before disconnecting the QD fitting, the two subchambers of the EIP-CP would be pressurized with nitrogen. As disconnection proceeded, the pressurized outer tube would expand to follow the moving umbilical plate of the mating fitting, up to a maximum axial thickness (corresponding to a tire width) of about 6 in. (≈15 cm). The subchambers would be shaped so that once maximum expansion was reached and the chamber could no longer seal against the receding umbilical plate of the mating fitting, the opening on the exposed end of the chamber would narrow to a small hole. The purge flow of nitrogen would keep ambient air out of the chamber.

To prepare for reconnection, the umbilical plate of the mating fitting would be brought into contact with the EIP-CP chamber and the supply of nitrogen would be turned off. Then a vacuum pump would be used to deflate the nitrogen from the outer chamber, so that the chamber could be pressed flat against its umbilical plate and the mating QD connectors pushed together.

This work was done by Ivan I. Townsend III of Dynacs, Inc., For further information contact the Technology Programs and Commercialization Office at (321) 867-8130 for Kennedy Space Center.

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NASA Tech Briefs Magazine

This article first appeared in the February, 2004 issue of NASA Tech Briefs Magazine.

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