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Rockets and Missiles

Guidance Systems

At one time, the methods used to guide a missile to its target were relatively simple. One of the most primitive of these systems was the use of a conducting wire trailed behind the missile and attached to a ground monitoring station. The person controlling the missile's flight could make adjustments in its path simply by sending electrical signals along the trailing wire. This system could be used, of course, only at a distance equal to the length of wire that could be carried by the missile, a distance of about 984 ft (300 m).

The next step up from the trailing wire guidance system is one in which a signal is sent by radio from the guidance center to the missile. Although this system is effective at much longer ranges than the trailing wire system, it is also much more susceptible to interference (jamming) by enemy observers. Much of the essence of the missile battles that took place on paper during the Cold War was between finding new and more secure ways to send messages to a missile, and new and more sophisticated ways to interrupt and "jam" those signals.

Some missile systems carry their own guidance systems within their bodies. One approach is for the missile to send out radio waves aimed at its target and then to monitor and analyze the waves that are reflected back to it from the target. With this system, the missile can constantly make adjustments that keep it on its path to the target. As with ground-directed controls, however, a system such as this one is also subject to jamming by enemy signals.

Another guidance system makes use of a TV camera mounted in the nose of the missile. The camera is pre-programmed to lock in on the missile's target. Electronic and computer systems on board the missile can then keep the rocket on its correct path.

Resources

Books

Collinson, Charles. "Missile." McGraw-Hill Encyclopedia of Science & Technology. 7th ed. Vol. 11. New York: Mc-Graw-Hill Book Company, 1992.

"Missile," and "Rocket." In The Illustrated Science and Invention Encyclopedia. Vols. 12 and 15. Westport, CT: H. S. Stuttman, Inc., Publishers, 1982.

Sutton, George P. "Rocket Propulsion." In McGraw-Hill Encyclopedia of Science & Technology. 7th ed. Vol. 15. New York: McGraw-Hill Book Company, 1992.


David E. Newton

KEY TERMS

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Ballistic missile

—A missile that travels at a velocity less than that needed to place it in orbit and which, therefore, follows a trajectory back to the Earth's surface.

Grain

—The fuel in a solid propellant.

Hypergolic system

—A propellant system in which the components ignite spontaneously upon coming into contact.

Monopropellant

—A system in which fuel and oxidizer are combined into a single component.

Specific impulse

—The thrust provided to a rocket by a fuel as measured in pounds of payload lifted per pound of fuel per second.

Additional topics

Science EncyclopediaScience & Philosophy: Revaluation of values: to Sarin Gas - History And Global Production Of SarinRockets and Missiles - History, Scientific Basis Of Rocketry, Rocket Propulsion, Solid Fuel Rockets, Specific Impulse, Multistage Rockets