Tape for Space

Abstract

* RED TAPE has been one of the greatest hindrances to the U.S. space program, but without another kind of tape-the magnetic variety-space research would have ground to a halt years ago. During the first 20 minutes of a typical space shot, for example, three times as many 'words as there are in the entire Encyclopedia Britannica must be recorded on tape. Actually these are not words as such but their equivalent in digital bits, the language of electronic computers. The Library of Congress estimates that about 30 bits are the equivalent of an average English word. The first data from a pilotless flight was recorded by a much more austere system. In 1929, Dr. Robert Goddard, the father of modern rocketry, built a small rocket in which he mounted a thermometer and a barometer. Facing the meterological data acquisition system, as it would probably be called today, was a camera. When the rocket had climbed to a height of 100 feet, the camera shutter was automatically tripped. Afterwards the rocket floated back to earth with its prize. Magnetic tape has given data handling a much more complicated rolein fact, it now has three roles. Briefly, they are monitoring the condition of the spacecraft, giving it operational instructions, and recording the information that it collects on its mission. As space missions have expanded since Goddard's pioneering experiments, new problems have cropped up, some of them almost unheard of only a few years ago. One problem, especially with longdistance flights, is that data must be sent back to earth slowly. Since the small power supplies permissible on space vehicles produce only small voltages for the playing back of data, transmissions from spacecraft must be kept to a very narrow band of frequencies. Otherwise the available power would be too diluted to do any good. The result of all this is that only so much data can be pushed through to earth in a given time. This is the reason Mariner 4's photos of Mars took only minutes to record but days to play back. These difficulties beset only one of magnetic tape's three jobs. Back on earth, where millions of dollars worth of electronic computers carry on twoway data-talks with their spacecraft, magnetic tape has had no such stumbling blocks. Development has gone on unfettered at a prodigious rate, and the United States' ribbon of tape grows longer, and longer, and longer.