National Geographic : 1960 Jul
Some of the devices, O'Sullivan said, would gather sunlight and convert its heat into elec tricity for television and radio transmissions back to earth. "Fortunately we have up there an excellent source of energy," he commented. "Our stud ies indicate we can develop power in terms not just of watts, but of kilowatts." Plastic structures, though appealingly light, obviously would be limited to unmanned ve hicles. When scientists consider the design of safe, well-equipped ships for distant ex peditions, they find that conventional rocket propulsion won't do the job. The fuel load becomes hopelessly large. True, boosters and upper-stage rockets now in prospect will enable us to explore the moon.* We shall be able to fire instruments to the moon, easing them down with small retro-rockets, and even send men there and return them. But when astronauts visit Mars and Venus, they must be blasted through the void by some new means of propulsion. Atom Rocket Holds Boundless Promise That Jack-of-many-trades, the atom, may provide an answer. A nuclear reaction pro duces ten million times as much energy per pound of fuel as the best chemical rocket pro pellants, though only a fraction of this energy can be utilized. For some years the Atomic Energy Commission has been developing a nuclear rocket.t NASA now shares in this task, known as Project Rover. An atom rocket would use a reactor to heat a light gas such as hydrogen. Expelled, the raging gas would give thrust. Since a re actor's heat output is not dependent upon Cutaway Model Bares the Fuel Tanks of a Promising Experimental Rocket NASA is developing new and more powerful second- and third-stage rockets to mount atop the Atlas, Thor, and other boosters. With improved upper stages, the space agency can launch heavier payloads. Here scientists examine a model of a pro posed upper-stage rocket developed by Jet Propulsion Laboratory, a NASA contractor. Tanks would hold the oxidizer-nitrogen tetroxide-and the fuel-hydrazine. These chemicals, unlike most other liquid propel lants, can be stored in rockets for relatively long periods. KODACHROMEBY NATIONALGEOGRAPHICPHOTOGRAPHER BATES LITTLEHALES© N.G.S. combustion, there is no need for an oxidizer. As for hydrogen fuel, this type of rocket would consume only a third to a half as much as its chemical counterpart. Consider what this would mean during a voyage to Mars by two ships, one powered by chemical fuel, the other by nuclear energy. They begin their journey from an earth orbit, and both weigh 150,000 pounds at the start. The chemical rocket reaches Mars and sends back its final rocket stage, as the pay load, to earth. But this final stage can weigh only 3,000 pounds, too small for a human passenger. The nuclear system, however, re turns a 20,000-pound, man-carrying payload. Atomic rockets become even more attractive when scientists consider utilizing fusion, the process in which atoms join together rather * See "Reaching for the Moon," by Allan C. Fisher, Jr., NATIONAL GEOGRAPHIC, February, 1959. t See "You and the Obedient Atom," by Allan C. Fisher, Jr., NATIONAL GEOGRAPHIC, September, 1958.