Abstract: A long-term thermally stable cryostat (40). The cryostat (40) pre-cools an incoming high-pressure gas, converts it to a cold liquid, contains the liquid, and cools an item by allowing the liquid to acquire heat from the item and boil into an exhaust gas, while maintaining an absolute pressure in the container to reduce thermal noise due to altitude-induced pressure changes. In specific embodiments, the cryostat (40) includes a hollow mandrel (52) disposed within a cooling volume (64) mounted within a dewar vacuum area (58). Pre-cooling fins (44) spiral around the hollow mandrel (52) within the cooling volume (64) and circulate an incoming high-pressure gas around the mandrel (52). A flow restrictor (60) receives the incoming gas from the pre-cooling fins (44) and releases it into the cooling volume (64), thereby converting the incoming gas into a cold liquid which can acquire heat from the item and boil into an exhaust gas.

Abstract: A dewar assembly has a wall contacting a liquefied gas within the interior of the dewar assembly. The dewar assembly is processed so as to remove the stable gaseous film boiling layer that is normally present between the liquefied gas and the wall. The processing is preferably accomplished by reducing the pressure on the liquefied gas to reduce its temperature and the temperature of the wall, and then returning the pressure over the liquefied gas to ambient to produce a temperature in the liquefied gas which is temporarily greater than that of the wall. The existing gaseous film boiling layer is removed, so that thermal and acoustic variations present in the system due to the presence of the film boiling layer are eliminated, and the liquefied gas attains a more direct contact with the wall.

Abstract: A short-term thermally stable cryostat (40). The cryostat (40) pre-cools an incoming high-pressure gas, converts the gas to a cold liquid, and cools an item by allowing the liquid to acquire heat from the item and boil into an exhaust gas, while maintaining a constant flow rate of the exhaust gas to reduce thermal noise due to flow rate modulation. The cryostat (40) includes an evacuated space (58) therein containing the item to be cooled and an inner cooling volume (64). Pre-cooling fins (44) spiral around a hollow mandrel (52) within the cooling volume (64) and circulate an incoming high-pressure gas around the mandrel (52). A flow restrictor (60) receives the incoming gas from the pre-cooling fins (44) and releases it into the cooling volume (64), thereby convening the incoming gas into a cold liquid which can acquire heat from the item and boil into an exhaust gas.

Abstract: An apparatus for decreasing stray radiation incident upon an infrared detector includes a concavely curved lens surface adjacent the detector, the center of curvature of which concave surface is located on the surface of the detector. This arrangement limits stray radiation originating rearward of the concave lens surface to black-body radiation emitted forward from the surface on which the detector is mounted, and the detector itself. That stray radiation may be reduced to a low value by decreasing the temperature and/or increasing the emissivity of the detector mounting surface and the detector itself. Stray radiation out of a desired wavelength band and originating forward of the rear concave lens surface may be attenuated by means of a spectrally selective filter.

Abstract: A retro reflection guidance and control system for a projectile, and a method of obtaining flight characteristics and controlling the projectile. A launch platform based transmitter/receiver and processor sends signals to a projectile, which signals are received at the back thereof. The transmitted signals are selectively reflected, to provide flight characteristic information to the transmitter/receiver, and detected to provide flight control information to the projectile.