Armies have used visual obscurants for centuries to protect their personnel from observation by their enemies. Presently, with the advent of laser rangefinders operating at near infrared and thermal imaging systems at mid and far infrared frequencies, the need for obscurant counter-measures at these wavelengths has become a primary protective requirement. The need for obscurants at even longer wavelengths is a necessity because of the recent development of "smart" munitions with millimeter wave seekers.
Known obscurants at these wavelengths are comprised of solid particles. Thin flakes are used for the infrared wavelength detection devices. Small high-aspect ratio fibers are used as an obscurant against millimeter wave detection devices.
The problem with aerosolizing these solid particles to form an obscurant cloud is that these obscurants require a large amount of propelling air. The basic rule of thumb developed by prior art experience with these materials is 10 pounds of air required for each pound of particulate dispensed. In the past, the use of an air ejector, such as the Rutstein AP-83, partially reduced the problem. Operating at about 30 psig, the Rutstein ejector acts as a venturi nozzle to induce about 5 pounds of air flow for every pound of air delivered to it. However, even with the AP-83, to generate an obscurant cloud at a flow rate of 10 pounds per minute requires a primary air source at 20 pounds per minute. EQU 10 lb. air/1 lb. obscurant.times.10 lbs. obscurant.div.5 (ejector induced-to-primary air ratio)=20 lbs./MIN.
Prior art conventional air compressor with this capacity would be huge and not practical for a mobile fighting vehicle. A blower with the flow capacity will not provide the aforementioned required pressure.
All smoke generators presently under development with the capability to disseminate infrared and millimeter wave obscurants use the bleed air from a turbine as the air source for the air elector. Usually these smoke generators are mounted on a host vehicle, such as a High Mobility Multipurpose Wheeled Vehicle or an Armored Personnel Carrier. The problem with these obscurant disseminators using turbines is that turbines are sophisticated, expensive engines requiring special skills for maintenance and repair. Their durability in today's mobile army battlefield environment is questionable.
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