A Stored Gas Actuator Unit for the TOW Missile 650338
The paper to be presented is a discussion of the design features of an integrated actuator unit for positioning the aerodynamic fins of the TOW missile. The unit comprises a high pressure nitrogen/helium container, explosively actuated cutter, pressure reducer with relief, die cast housing with distribution manifold, four high response solenoids, 3-way valves, and four actuators. The unit is designed for high reliability, low cost, and light weight consistent with its application in a missile which must be carried by the troops and which must be manufactured in large quantities.
There are a number of aspects of the design of this actuator unit which are without precedent for such a missile application. The use of a die cast housing with sections which have burst pressure requirements of 17,000 psi; a one-piece nitrogen container which increases the reliability and reduces the inspection necessary to establish a 5-year storage capability; an explosively-operated cutter which has a precisely controlled activation delay and high post-firing resistance; and overall actuator responses under load of less than six milliseconds are all features of the design to be discussed in this paper.
The most exacting requirement, when the weight, cost, and reliability factors are taken into account, is that of matching actuator extend and retract positions at any instant of operation. To limit the possible missile rolling moment, as well as errors in corrective pitching and yawing moments, the extend motion of each actuator is caused to be within one millisecond of the time for associated actuators to achieve the same motion, on both extend and retract. Similarly the extend and retract of a given actuator must be so matched.
Acceleration, shock, and vibration conditions associated with the system operation are extremely high. The operating time is quite short. The entire package satisfying the above requirements is only slightly above two pounds in weight.