is identical to the M10 engine developed for the arzay by Thiokol. As a result of this sinilariry, no development test program was required on toe engine it- self. The exgine unit is 16 inches ia dixoerer, 77.5 inches in length, and weighs approximarely 730 pounds. It develops approximately 35,000 pounds of thrust for 2.6 seconds. A sacually operated arm-safe device provides a means of shorting =:t the electrically operated squibs in the igniter. When in tie "safe" position, the ignition uit is also physically blocked off from the main propellant charge so that, eves if the igniter were fired, the main ‘propellant charge would oot be ignited. The If-52 engine has a high resistance to all types of auverse environment and, aside from stamiard procedures for solid fuel propellants, mo special precautions are necessary in handling or storage. This, together with the inherent simplicity of the solid fuel engine, made it ideal for this application. The skirt-fin assembly fits over the engine nozzle and is bolted co a boss on the engine at Che aft ead of the fuel chamber. The four fins are bolted to the skirt in a manner which permits adjustment of the fin angle anywhere between approximately 1/2 and 1-1/2 degrees to provide the desired roll rate. is accurately set by use of a specially designed aligning jig. Fin angle Since altitrcde is controlled largely by control of vehicle weight, fins, sidsection, and launching slippers asy be made of either steel or aluminua, as weight of the confizguration requires. Engine and tail assembly for the booster on the two-stage vehicle are identical to those on both the single-stage vehicle ami the second stage. A cone- shaped interstage adapter which fits into the nozzle of the second-stage unit is bolted to the front end of the booster engine. At the high angles of firing necessary to this program, the second stage needed only to be set on the coneShaped adapter on the booster; na further physical connections between the two stages were required. feo stages. At burnout of the booster, norzal drag separates the Spin rockets are used cn the two-stage vehicles. These rockets are attached to the interstage adapter on the booster and are fired by a switch on the aft end of the booster as it clears the launcher, os? 77