however, is unable to produce any measurable ozone depletion effect (e.g., see Fig. 7). In fact, the 1970 MIT Summer Study concluded that SST effects on ozone concentration were almost certain to be negligible. Excessive dispersion of particulate matter in the stratosphere This possibility was first raised by the 1970 MIT Summer Study. The fear was that engine exhaust particulates could reach high stratospheric concentrations, resulting in severe earth-surface temperature changes which have heretofore only been observed after cataclysmic volcanic eruptions. This fear was engendered by measurements of a 60- 8° C increase in stratospheric temperature, which were attributed to particles from the Mt. Agung volcanic eruption in March 1963. The accuracy of this association has been subject to question, since there is substantial evidence that the Mt. Agung dust produced only local temperature changes, and that it dissipated in the characteristic fallout time of about 1-1/2 years; the disputed 6° -8° C temperature rise was measured 6 years after the eruption on the opposite side of the Earth. Although most indications are that the particulate effect on the Earth's heat budget due to the SST has been overestimated, the possibility that it may prove to be a problem must be considered. Since the bulk of the permanent SST external particulate matter is composed of sulfates, however (soot and hydrocarbons are virtually nonexistent at cruise conditions), substantial reductions in fuel sulfur content (by about 80%) can be made, at somewhat greater fuel cost for this cleaner fuel. The resulting 80% reduction in particulates would have a high probability of eliminating the problem. Introduction of carbon dioxide and gaseous pollutants (carbon monoxide, nitrogen oxides, sulfur oxides, and hydrocarbons) into the stratosphere. The relative fraction of pollutants contributed by aircraft engines has always been very small (see Fig. 8). Further, recent engine modifications such as improved combustion recirculation will make the SST engines far "cleaner" than any of today's operational engines; in fact, the 1970 MIT Summer Study concluded that the SST would probably pose no problems in this area. The "greenhouse" effect (warming of the Earth due to increased carbon dioxide levels in the stratosphere) was also considered in the the Summer Study, and it was decided References: (a) Baade, F., "The Race to the Year 2000," Doubleday & Co., 1962. (b) Swihart, J. M., SAE Preprint No. 71-0320, Feb. 1971. that the maximum predicted long-term increases due to SST fleet operations would almost certainly not cause any signifi cant change in temperatures. Introduction of pollutants into the air in airport neighborhoods. Although it is well recognized that cruising turbojet engines are highly efficient, and contribute only a tiny fraction of our present air pollutants (see Fig. 8, cited earlier), there has been some concern about the high pollution level in airport neighborhoods caused by inefficient engine idling, taxiing, and takeoff operations. This is a valid criticism, but it is certainly no more serious for the SST than for any of today's aircraft. In summary, whereas the final conclusions as to the potential extent of various stratospheric pollution factors cannot be made until results are obtained from the proposed analytical and experimental research program, there is a fairly high level of confidence that SST fleet operations will cause no significant ecological effects. Since foreign SST's will operate whether or not the U. S. program continues, and since the atmosphere is a supra-national entity, the proposed stratospheric research program is urgently required. The United States' SST prototype test phase is an important part of that program, and should not be curtailed, stretched out, or eliminated. Further, it can be stated with full confidence that flight operations of the two prototype SST's will not cause any equilibrium changes in the environment. There are two basic points about SST financing which are often misunderstood: First, the government is helping to finance only the prototype program basically a research and development project -- which is to culminate in 1973 with the building and testing (up to 100 hours) of two prototype aircraft. Subsequent costs, and especially the funds needed to build the production aircraft which will eventually be sold, are expected to be financed by private capital. Second, the government money going into the SST prototypes is invested in the full economic sense - because the government gets it - all back, with interest, when the airplane goes into production. The United States receives a royalty of about $4 million on each aircraft sold, recovering almost its entire $1.3 billion investment for development of the prototypes with the sale of the first 300 planes, and receives an additional billion dollars, as interest, when a total of 500 airplanes have been sold (the conservative market estimate by 1990), plus additional royalties on any subsequent aircraft sales. It is of particular interest to consider the actual amount of money which would be saved by cancelling the prototype SST |