Science: Here to There, Accurately

On a blustery February morning in 1953, a B-29 took off from Massachusetts' Bedford airport and pointed its nose along the great-circle route to Los Angeles. There were eight people aboard the big bomber, but after take-off no one worked the controls. For two hours, a pilot sat watching the instruments. Then he got bored and let the plane fly itself. It did, making minor corrections for each gust of air. It rose to 21,000 ft. to traverse the Rockies, stayed on course through a 100-m.p.h. wind shift over Nevada. Finally, 13 hours and 2,520 miles from Bedford, the pilot took over, took the aircraft the remaining ten miles to Los Angeles International Airport. To the jubilant M.I.T. scientists aboard the plane, he lamented: "I've just lost my job."

Since that historic flight, kept secret until last week, Inertial Guidance—the gyroscopic navigational system that guided the B-29 without visual or electronic aid from earth or stars—has been an obvious choice to control the U.S.'s ultimate earth-to-earth weapon: the pilotless intercontinental ballistic missile (TIME, Jan. 30, 1956). Last week in Cambridge. Mass., a pudgy, square-faced engineer who presides over an aging red brick factory building (still labeled "Home of Whittemore Shoe Polishes," but listed on Massachusetts Institute of Technology records as the Instrumentation Laboratory) outlined the details of Inertial Guidance, just declassified.

Three Virtues. The great virtues of the new system for the 5,000-mile ICBMs, according to Dr. Charles S. Draper (TIME, Dec. 10), head of M.I.T.'s Department of Aeronautical Engineering: extreme accuracy, interference-proof operation (weather, sunspots and enemy jamming attempts have no effect), and radio silence (no signal is sent or received).

Like the gyrocompass, the gyroscopic ship stabilizer and the Mark 14 antiaircraft gun sight (developed by Dr. Draper and his associates at M.I.T. in 1941), Inertial Guidance is based on the familiar principle that keeps a child's gyroscopic top from falling: a rapidly spinning wheel will resist forces working to twist it from the plane in which it is revolving. A gyroscope sufficiently free of outside disturbances—e.g., friction—will maintain an unvarying spin axis in relation to the "fixed" stars—or any other points of reference—no matter on what path it is carried by the motion of a vehicle or the rotation of the earth. Such a gyroscope is one element of Inertial Guidance. The other element is an electronic "Schuler pendulum" that always points toward the center of the earth, regardless of an aircraft's acceleration (speeding up or slowing down).* The unchanging gyroscope line and the line of the plumb bob, which tells which way is down, form an angle that changes as the plane follows the earth's curved surface. This angle is the self-contained milepost by which Inertial Guidance determines and sets its course (see diagram).