Original Date: 05/17/1993
Revision Date: 01/18/2007
Best Practice : Spectral and Radiometric Measures of Flare Intensity in a Dynamic Environment
To reduce the overall expense and time cycle for infrared decoy flare development, the Crane Division-Naval Surface Warfare Center has designed, built, and extensively tested a sophisticated measurement facility capable of simulating the high velocity airflow experienced during decoy launch while measuring the spectral and radiometric output of the flare under evaluation. The infrared decoy flare is used by aircraft for protection against heat seeking missiles. These devices quickly produce a high intensity heat source that diverts the incoming missile away from the aircraft. Static tests, used in preliminary development phases to measure color and relative intensity, produce intensity measurements up to an order of magnitude greater than the decoy would produce on aircraft launch. A high velocity wind shear environment test or simulation is therefore critical to accurately evaluate the performance capabilities of a particular decoy flare.
Typically, flight effectiveness tests are performed by launching decoy flares from an aircraft. These flight tests are logistically difficult to arrange and very expensive to perform. The cost of a typical flight test, during which up to 30 flares can be launched and evaluated, is approximately $100,000, exclusive of post-flight data reduction and analysis expense.
The measurement facility is based on the Transient Velocity Windstream Test Apparatus that can simulate decoy launches from MACH 0.1 to 1.2 speeds. The apparatus consists of a series of air compressors used to pump air from one to four, 1,250-gallon tanks to a pressure of 200 psi. The pressurized air is then discharged through a computer-controlled, pneumatic butterfly valve and nozzle to provide a high velocity airflow across the pyrotechnic device. Rapid cycle times of less than six minutes are achieved by this state-of-the-art system. Both variable velocity airflows, representative of non-thrusted flares subjected to drag effects after launch, and constant velocity airflows, representative of thrusted decoys, can be simulated through valve control. Pyrophoric devices can be tested in the Transient Windstream by using the Simulated Aircraft Test Fixture.
The instrumentation used for measuring the flare characteristics includes a circular variable filter spectroradiometer, large dynamic range calibrated super frame thermal imagers, and several infrared banded radiometers. The instrumentation was designed to duplicate the instrumentation used for both ground-to-air and air-to-air flight effectiveness tests. Thus, the windstream test facility data can be easily correlated, without instrumentation variance, to both types of flight test measurements. Through the use of the Transient Velocity Windstream Test Apparatus, candidate flare concepts which performed well during preliminary development static tests can be evaluated cost effectively for down-selection. The most promising designs can then be optimized and reevaluated, through several iterations, prior to performing expensive flight effectiveness tests. Through the elimination of costly flight tests, it is estimated that dynamic testing results in an annual savings of over $1 Million with an additional savings of $1.08 million through dynamic testing for lot acceptance.
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