Even as Los Angeles struggled with its auto-emissions problem, word came from Cambridge, Mass., about a more widespread future emissions problem: nitrogen oxides from the SST. During the 1971 debate that led to the cutting off of U.S. Government funds for the supersonic transport, environmentalists had voiced fears that nitrogen oxides in the exhaust of the 1,800-m.p.h. aircraft might weaken the ozone shield that protects the earth from an overdose of the sun's ultraviolet rays. The charge was serious, but was it true? The U.S. Department of Transportation commissioned researchers at the Massachusetts Institute of Technology to find out. After two years of study, M.I.T.'s experimental evidence indicates that the fears of '71 are justified in '74.
Using a mathematical model, the team simulated the effects on the earth's atmosphere of a projected fleet of 500 SSTs operating for eight hours a day.
Though that number seems high—only a prototype of the Anglo-French Concorde and two Soviet TU-144s are now flying—most aviation experts predict that at least 500 SSTs will be in service by the end of the century. If they all fly, the researchers warn, the nitrogen oxides generated would have a thinning effect on the ozone shield. Without this critical protection, people would run a much higher risk of going blind and of contracting skin cancer.
The M.I.T. investigators fed data into their computerized model of atmospheric conditions up to an altitude of 43 miles (SSTs fly at about 65,000 ft.).
The results, based on the emissions of the Concorde, showed that supersonic exhaust discharges in the general latitude of Paris and New York would deplete ozone by a risky 16% in the Northern Hemisphere. The ozone blanket would also be thinned significantly in the Southern Hemisphere, where the computer had assumed no SST flights.
The Concorde, say its manufacturers, is expected to start airline service in 1976. Even if the controversial plane does not win permission to land in the U.S., the numbers of supersonic craft jetting through the earth's upper atmosphere could be a threat to the well-being of Americans. It now seems clear that very high speeds at out-of-sight altitudes could drastically upset the whole planet's ecological balance.