National Geographic : 1964 Mar
IN THE CLEAN ROOM, so named because air filters trap 95 percent of microscopic dust, the cabin sect on of an early Gemini spacecraft comes off the McDonnell assembly line. One crew installs metal shingles; another in the interior completes the electronic systems. This particular craft will be mated to a Titan II launch vehicle (opposite) when NASA astronauts attempt the first Gemini two-man flight into space. One of the most critical periods from the standpoint of astronaut safety begins with launch and continues until the rocket is out of the atmosphere. Should a malfunction oc cur in the booster, the crew must be whisked away from it, and almost instantaneously, because it may explode. Mercury met this problem with a rocket powered escape tower capable of pulling the capsule free for a parachute descent. In Gemi ni the technique is quite different. The astro nauts can jettison the hatches and blow them selves and their seats out of the capsule, as they would from a jet aircraft, and descend by individual parachutes. They would do this only if an emergency occurred below 70,000 feet. Above that altitude they would free Gemini from the second-stage booster, fire Gemini's rockets to pull away, then ride the capsule down to the ground, as in a Mer 364 cury escape, or jump when well within the atmosphere. Ejection seats, though a tried-and-true escape tech nique, could pot be used with Mercury. Atlas engines burn kerosene and liquid oxygen, and an extensive blast and fireball are haracteristic of these propellants if the boost er explodes. Had any done so in the Mercury program, the men would have needed the protection of their capsules. Titan II, on the other hand, burns one of the "exotic" fuels, a combination of hydrazine and unsymmetrical dimethyl hydrazine, with nitrogen te troxide as the oxidizer. Their blast effect and flame would P. BLAIR © NG. be confined to a lesser area. Thanks largely to these new propellants, the countdown for a Titan II launch is much shorter than for an Atlas. Fuel and oxidizer burn instantly on contact. This eliminates need for an ignition system. Moreover, they may be kept in the rocket without deterioration, ready for instant use. In contrast, the Atlas's liquid oxygen vapor izes and must be replenished periodically. A shortened count, increased simplicity, reliability... these will be mandatory for Gemini. Lift-off must be on schedule. Ren dezvous requires accurate celestial marks manship; precise timing is all important. The mission begins when an Atlas blasts off from the Kennedy Space Center and thrusts a 32-foot-long Agena target vehicle into a nearly circular orbit 185 miles above the earth. About 24 hours later Agena again will approach the point east of the space center where it entered orbit.