As I’ve noted earlier, the U S. SST program was canceled in part because of environmental concents. The Concorde'(economics have been greatly affected by being prohibited from supersonic High! over most land areas, and by the cost of fuel Ihc environmental, and thereby political, barriers to a successful SST arc: energy consumption, sonic bang, atmospheric impact, and airport noise.
1.6.1 Energy Consumption
The fuel consumed by SSTs per passenger mile is several times that of subsonic transports Supersonic flight entails a new penalty, that of wave drag. Lift has to equal, and sometimes exceed, weight if there is to be air travel. Wave drag due to lilt is inescapable except for an infinitely long swept wing, best approximated by the way. by an oblique wing Volume can be moved through the air supersonically with no wave drag, but at considerable expense in skin friction drag from extra surfaces.
Sixty countries have ratified a treaty that commits them to better manage their generation of greenhouse gases J16). Developed countries arc to provide plans by the end of this century that show how they will return to 1990 levels of greenhouse gas generation Does this argue against an SST? As Secretary of Transportation Coleman said in his decision to let the Concorde operate: "It would border on hypocrisy to choose the Concorde as the place to set an example… (for energy efficiency) while ignoring the inefficiency of private jets, cabin cruisers, or an assortment of energy profligates of American manufacture’* |5J.
The Concorde achieves 17 scat miles per gallon and. at 679fr load factor, is equivalent to a car w ith only the driver, achieving 12 miles per gallon But the Concorde’s passengers arc going more than twenty times as fast and follow ing nearly a straight line to their destination. A future SST should not be rejected because of energy considerations. However, its economics and thereby its market, are more sensitive to fuel costs than its subsonic counterparts and these are not only variable, but jet fuels may eventually be taxed for their carbon content