Extendable Nozzle Exit Cones for Divert Thrusters

The design of divert thrusters for kill vehicles is a tradeoff between a large number of factors. To minimize induced moments, the thrusters are required to be located near the kill vehicle's center of gravity in a cruciform configuration. Forendo/exo-atmospheric kill vehicles, divert thruster nozzles cannot extend beyond the skin of the vehicle. For pure exo-atmospheric kill vehicles, the size of the nozzles is limited by the need to fit within the carrier missile's aeroshell. The requiredthrust levels combined with these packaging constraints, result in thrusters with short, low expansion ratio nozzles. Low expansion nozzles result in low efficiency, divert thruster performance, i.e., lower thrust and lower specific impulse (i.e., morepropellant is required). Significant thruster performance improvements are possible if the expansion ratios of the thrusters can be improved (i.e., getting more work out of the gases). Systima Technologies have teamed to offer a way to improve theexpansion ratio of divert thrusters (i.e., improve thruster performance) during exo-atmospheric maneuvers. This is achieved by means of an extendable rocket nozzle cone which increases the expansion ratio of the thruster propellant gases. Kill vehiclepackaging considerations typically require the use of short, low efficiency nozzles on the divert thrusters. The extendable nozzle divert thruster allows more efficient nozzles to be packaged in the radial space currently available for divert thruster.The divert thruster efficiency improvements are achieved by extending the rocket nozzles to more fully expand the thruster propellant gases (i.e., better utilize the energy in the thruster propellant gases). For a typical DACS nozzle, if the exitdiameter of the divert thruster rocket nozzles could be doubled, the performance of the nozzle would be increased by 10 percent. This would mean that it would be possible to achieve 10 percent more divert impulse from the same amount of propellant or theamount of propellant carried could be reduced by 10 percent. Either increasing the divert impulse capability with current tankage or reducing the DACS propellant system weight by will bring significant overall improvements to kill vehicle performance.