Search Results

The Near Infrared Camera and Multi Object Spectrometer (NICMOS) was installed aboard the Hubble Space Telescope in February 1997. This instrument contains a solid nitrogen dewar for cooling infrared detectors to a temperature of 58 K. Gaseous helium flowing through a small diameter tube internal to the cryogen tank was used to freeze the nitrogen. A sudden and significant increase in the dewar heat leak during instrument development resulted in a detailed study of the possible causes. This investigation lead to the conclusion that thermally driven acoustic oscillations caused the anomalous heat transfer.

One set of components in the Environmental Control and Life Support System (ECLSS) on Space Station Freedom is the Fluid Tank Sets (FTS). Development of the strategy for controlling the condition of the fluids in the FTS has involved optimizing the application of a limited amount of heater power in order to meet fluid delivery requirements. Refinement of the fluid delivery requirements has focused the selection of control methodology. In order to maintain the fluid pressure within a supercritical pressure band, the final control scheme includes a dual mode heater. Additional control functions are necessary for preventing over-pressurization and two-phase fluid conditions. Finally, controller software will include temperature and pressure limits on the heater for contingency and bleed-to-residual fluid delivery modes.

This paper describes the development and testing of a two-phase fluid reservoir for use in advanced thermal control systems designed for space applications. The aim of this development is to construct a highly reliable reservoir with the capability of controlling the saturation temperature of the system working fluid. The design considerations are described along with the methods of achieving the operational requirements. In addition, results from the initial testing of the prototype are presented.