Science: The Largest Load

A perfect takeoff erased all the embarrassments of delay. One tiny plug carelessly left in an oxygen line had delayed the launch for 48 hours. Poised on the pad, the big bird had to wait impatiently while Air Force planes tracked down the noisy radio of a ship slogging along offshore. But now Saturn SA-5, biggest and most powerful rocket ever fired aloft, was rising above Cape Kennedy as routinely as any operational missile.

Trailing a muffled bellow from its eight engines, Saturn seemed to rise with unnatural slowness. During the first ten seconds it climbed less than twice its own length, then it quickly gathered speed and rumbled behind a low-flying cloud. At 48 miles’ altitude, the massive first-stage booster shut off and separated. The hydrogen-burning second stage took over, and it burned perfectly for eight minutes. When it was 1,300 miles downrange and 375 miles north of Antigua Island, the triumphant announcement came: Saturn had reached orbiting speed. The new satellite weighs 38,000 Ibs., and 20,000 Ibs. of it is payload. The weightiest Russian satellites, Sputniks 7 and 8, 1961, weighed only 14,292 Ibs. Only six years ago, the U.S. tried and failed to get a 3-lb. Vanguard into orbit.

Crewless Liner. The success of the Saturn SA-5, which puts the U.S. far ahead of the Russians, is more than mere astronautical muscle-flexing. It was achieved by almost incredible complexity and sophistication. The first-stage booster, built by Chrysler, gets its 1,500,000 Ibs, of thrust from eight H-l engines originally developed by North American for the Atlas and other mis siles. Their tangle of auxiliary plumbing is like a jam session of snakes, and it gives most engineers the shudders.

The four center engines are immovable and canted outward to reduce the yawing effect if one of them should cut out. The four outer engines are on gimbals so they can be switched from side to side to give directional control. They get their kerosene and liquid oxygen fuel through flexible tubing, from nine tanks interconnected so that if one engine fails, the others will use its share of fuel and burn longer. Backing up the engines is an incredible array of pumps, valves, gas generators, high-pressure tanks and cables. Saturn SA-5 is as complicated as a crewless ocean liner operated by flash-quick automatons.

Saturn’s second stage, built by Douglas Aircraft Co., is even more sophisticated because of its uncomfortable fuel, liquid hydrogen. Space engineers admire LH2 because it provides better than one-third more thrust than kerosene, but it is hell to handle. It is so light (7% the weight of water) that it requires enormous tanks, elaborately insulated to keep the hydrogen from flashing to vapor. A long list of new materials had to be developed that would not lose their strength at the chilling touch of LH2.

Bootstrap Engine. The Pratt & Whitney RL-10 engines, each developing 15,000 Ibs. of thrust, are the first hydrogen engines ever to fly. Unlike most liquid-fuel rocket engines, they have no separate power source to drive their fuel pumps. Instead, the touchy LH² flows through the jacket of the combustion chamber. The heat that it absorbs as it keeps the chamber from fusing turns it to high-pressure gas that spins the pumps and forces more fuel into the chamber. The system’s many moving parts have to be made so precisely that they can run dry; no known lubricant works dependably at liquid hydrogen’s —423°. Despite its ambitious “bootstrap” action, the RL-10 has proved remarkably efficient and reliable. As Saturn SA-5 climbed into the sky, its radios reported everything from battery voltages to temperatures on the tail skirts. A TV camera watched the separation of the two stages and sent its pictures back “in real time” (instantaneously). Eight motion picture cameras recorded other views of the great rocket, including the sloshing of the fuel inside the tanks. Just before separation, they were all parachuted into the sea in waterproof capsules. Seven of them were quickly recovered.

Thrust for Apollo. Last week’s Saturn was the fifth successful launch of the Stage One booster, which was designed by Dr. Wernher von Braun’s team at Huntsville, Ala. Large clusters of liquid-fuel engines, though admittedly complicated, are now considered reliable. Far more critical was the test of the hydrogen stage. The whole Apollo moon program depends on liquid hydrogen, without which the monstrous rockets now under development would not have enough thrust to accomplish their mission.

Of the five Saturns now under preparation, three will put in orbit unmanned models of the Apollo command and service modules to test their space and aerodynamic behavior. Two more will orbit large instrumental satellites to measure meteoroid danger. Later, a modified Saturn with a more powerful hydrogen second stage will put the first manned Apollo unit into earth orbit.

The much larger Saturn C-5 that will carry three astronauts to the moon will be 281 ft. tall, will have five F-l rocket engines with a total of 7,500,000 Ibs. of thrust in its first stage. These engines have not been flight-tested yet, but last week’s flight left U.S. spacemen feeling uncommonly confident. They had fired the biggest known rocket, put the biggest payload in orbit, proved out liquid hydrogen and the tricky cluster concept. They had come a long way since Oct. 4, 1957, when the first Russian Sputnik shocked the world.