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Fast cool-down Joule-Thomson cooler for IR-detectors are required for all missiles, which shall be operable within a very short time, like IR-missiles being fired from ground against fast approaching fighter aircrafts at low flight-levels. New IR-seeker developments with larger look-angles require often that the IR-sensor is placed on the pivoted gimbal system. Due to space nd weight limitations the fast cool-down cooler for the sensor often cannot be installed there. The way out is the here presented two-stage "Fast Cool-down Dual Gas Spray Cooler." This by patents protected new fast cool-down cooler for pivoted IR-detectors contains an additionally installed 2nd-stage heat exchange-cooler. It comprises at the rear side of the detector-plate a nozzle through which a highly pressurized and pre-cooled gas (e.g. Argon, Nitrogen) is depressurized and thereby cooled down to its boiling temperature. The resulting liquid/vapor gas-flow behind the nozzle acts then as a spray-cooler for the detector. The 1st-stage apparatus consitutes a Joule-Thomson cooler, driven by a gas with a high cooling efficiency, like Methane (CH4) or Tetrafluoromethane (CF4 ≡ R14) to cool down the gas within the 2nd-stage cooler up to the 1st-stage gas boiling temperature. This cooler concept can be rigidly installed within the IR-seeker in such a way that the gas-orifice from the 2nd-stage cooler is just behind the pivoted IR-sensor plate. This solution requires no direct mechanical connection (gas tube) to the detector-plate. No additional weight impacts nor mechanical forces are provided to the gimbal system and its detector except the small kinetic cooler gas flow forces. With such a "Fast Cool-down Dual Gas Spray Cooler-System" with Argon and CF4 or alternatively CH4 a fast-cool down of the IR-detector to 100K (-173°C) has been achieved within less than 2.3 seconds from an ambient soak temperature of 323 K (+50°C). Compared with single-stage Joule-Thomson coolers this concept provides an unsurpassed cool-down time with a high cooling efficiency even from high soak temperatures. Taking into account that the cooler provides no weight or mechanical impact to the movable detector on the gimbal system this concept is exceptionally.
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