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Measurements are reported of the pressure recovery of straight-channel, symmetric, single-plane-divergence diffusers with inlet Mach numbers between 0.2 and choking for an aspect ratio of 5.0. The data reported cover a range of length-to-throat width ratios L/W1 and divergence angles 2θ for diffuser geometries near peak recovery. These data complement data previously reported for AS = 0.25 and 1.0. Diffuser performance maps are given that show pressure recovery Cp as a function of diffuser geometry for fixed values of throat Mach number Mt, throat blockage B, and aspect ratio AS for the range of variables tested. Of significant importance to the designer is the alteration in the shape of the pressure recovery contours on the performance maps with variations in Mt, B, and AS. Also reported are data on the effect of changes in diffuser inlet Reynolds number, asymmetric distribution of inlet blockage around the throat periphery, and the influence of rounded throat corners on the pressure recovery behavior of the straight-channel diffuser. These data have underscored the necessity of understanding the cumulative effects of a number of secondary parameters on pressure recovery. The importance to the designer of a knowledge of how diffuser performance depends upon the diffuser geometric and inlet parameters is discussed.

This paper presents a description of the Hubble Space Telescope (HST) Near Infrared Camera and Multi Object Spectrometer (NICMOS) Cooling System (NCS), the evolution of the cutting edge technology involved, a comparison of predicted versus on-orbit thermal performance, as well as possible future space applications. The NCS hardware consists of the NICMOS Cryogenic Cooler (NCC), an Electronics Support Module (ESM), a Capillary Pumped Loop (CPL)/Radiator assembly, and associated interface harnessing. The NCC is a state-of-the-art reverse Turbo-Brayton cycle mechanical cooler employing micro turbo machinery, driven by advanced power conversion electronics, operating at speeds up to 450,000 revolutions per minute to remove heat from the NICMOS instrument. The ESM provides command, control, and power distribution to the NCS, as well as providing the primary interface to the existing HST electronics. A two-phase CPL system removes heat from the NCC and transfers it to the radiator mounted externally on the HST aft shroud. The system was installed during Servicing Mission 3B via extravehicular activities in March 2002. The NCS revived the NICMOS instrument, which experienced a reduced operational lifetime due to an internal thermal short in its dewar structure, and restored HST scientific infrared capability to operational status.

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