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The purpose of this paper is to discuss the selection of a low-temperature coolant used to support Space Station Freedom Active Thermal Control System (SSF ATCS) qualification testing. SSF ATCS testing will use liquid nitrogen (LN2) to reduce the temperature of an intermediate coolant to as low as −78°C; the coolant will then interface with the ATCS working fluid to simulate the heat sink conditions of space. Selection of the intermediate coolant required investigation of the following coolant properties: low freezing point, low viscosity at low temperatures, very low to no toxicity and flammability, and low to moderate vapor pressure at room temperature. Of the four refrigerants that were initially considered, R-124 appeared to be the most attractive. A test was performed to verify the freezing point of R-124. The R-124 test results and a comparison of the four refrigerants are described in detail in this paper.

This paper describes two simple laser instruments which the automotive engineer can use in vibrational studies of diesel engines. The first is a ‘normal surface velocity’ instrument which the engineer can hand hold and simply ‘point’ at the target surface for measurement. Field tests have shown it to be quick and easy to use with excellent accuracy and reliability. It is a particular time-saver in test cell use where the necessity for many accelerometer fittings is removed. The second is a laser torsional vibrometer which can measure the torsional oscillation of rotating machinery parts. This has shown itself to be superior to the more standard techniques of slotted discs and slip rings, etc. and provides advantages of higher frequency response, greater accuracy and non-contact measurement. Conclusions drawn herald a step forward in measurement techniques and demonstrate the great potential of laser technology in heavy engineering applications.