Gas Guidance

To casual kibitzers at Cape Canaveral, the Polaris missile that took off from a dry-land pad and soared successfully downrange may have represented simply one more test shot. To U.S. Navy technicians, the deadly bird signaled the start of a new era in U.S. rocketry. A revolutionary new control system guided its second stage.

Standard weapon of U.S. nuclear submarines, the Polaris burns solid fuel, and it cannot be steered, as liquid-fuel rockets are, by swiveling the whole combustion chamber. Instead, Polarises now at sea use jetavators--movable nozzles inserted in their jet streams to deflect them and thus keep the rocket on course. No one likes jetavators; they are inherently troublesome, and their drag on the fast-moving jet stream soaks up precious thrust power even when they are not in use.

The new Polaris is equipped with nozzles that have no obstructions and no moving parts. For directional control, a small amount of freon gas is shot into the side of the hot exhaust stream, deflecting it just as if the nozzle had been turned. The system is light, and since it is not exposed to high heat or pressure, it is potentially trouble-free. Many missilemen are confident that solid-propellant rockets, already an important U.S. specialty, will be even more valuable when brief blasts of freon are used to twitch their fiery tails.

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