The Artificial Satellite

The rocket-launching vehicle that will toss the U.S. earth satellite into its orbit is proving a tougher design job than some of the scientists thought. Last week Assistant Secretary of the Navy James H. Smith Jr., taking public notice of the fact, announced that the first satellite will not take to space until early in 1958.

As to problems of getting the satellite up into space, Milton Rosen of the Naval Research Laboratory, and technical adviser of the satellite project, told about some of the novel features of the launching vehicle. Any one of them might be a cause of failure if not designed with long, loving care. Each component will have to be tested, both separately and in combination with others, before the first launching vehicle can head for space.

Balloon Tanks. The vehicle, Rosen told the National Capital Astronomers, will be a three-stage rocket 72 ft. long and 45 in. in maximum diameter. It will have no fins, but will depend for steering on its movable rocket motor and an array of small gas-jets. The tanks holding the propellants (liquid oxygen and gasoline for the first stage, nitric acid and dimethyl-hydrazine for the second) will be thin-walled to save weight, and will have little strength when empty. When they are full and highly pressurized with helium, they will become as rigid as auto tires and strong enough to serve as the structure of the rocket, which will have no other outside skin. These "balloon tanks" are a new and tricky device. They should not be rushed.

The first-stage rocket, carrying stages 2 and 3 and the payload satellite, will be fired due east, to take advantage of the spin of the earth (1,340 ft. per second at the launching point. Cape Canaveral, Fla.). When it burns out and separates, 36 miles above the earth on a curving trajectory, the second stage will take over. After burning out in turn, it will coast upward, still attached to stage 3, to the 300-mile level. While it coasts, its mechanical brain will be reading its numerous instruments and telling little gas-jets how to turn it in space until its length is parallel with the surface of the earth. The new, untried gas-jets will also set the third stage spinning rapidly, to give it gyroscopic stability on the final orbit. All these orienting and spinning devices, as well as many of the instruments, will require much development and testing.

Final Spurt. When the vehicle reaches 300 miles up, it will be at orbital level, above nearly all the atmosphere and pointing in the right direction. But its speed will be only half the speed required (17,000 m.p.h.) to make the satellite stick safely to its orbit. Reaching orbital speed is the job of the third-stage rocket. The final rocket will be small and will use solid fuel, which requires no tricky pumps or valves. It will fire for 30-60 seconds, depending on how much accelera tion the delicate instruments in the satellite can take without damage. When the fuel is gone, the burned-out rocket will be on an orbit. Rosen figures that it will have enough speed to carry it around an ellipse whose apogee (highest point) will be 1.400 miles above the earth and whose perigee (lowest point) will not be below 200 miles. If the satellite (an instrument-packed ball 20 in. in diameter) is separated from the rocket, both will revolve around the earth as independent satellites.

This file is automatically generated by a robot program, so reader's discretion is required.