The effect on ozone depletion by supersonic transports is still a hotly debated issue. But most scientists accept that ozone depletion by nitrous oxides is caused by the following mechanisms in order of importance.

• Cruise altitude. For a given rate of N0^ injection into the atmosphere the rate of ozone deple­tion will go up nearly linearly with altitude from altitudes between 15 and 20 km.

• Combustor entry conditions. The higher the combustor entry temperature and pressure the higher the formation of N0^.

• Fuel Efficiency. The higher the fuel consumption the higher the formation of NOg.

Though the lower wing loading contributes to a higher cruise altitude, this effect is almost completely offset by the reduction in parasite drag. The reduced parasite drag will lead to a lower cmise lift coefficient and therefore a lower cruise altitude. Because the effect of fuel efficiency is less important than lowering the combustor entry conditions, the power plant effi* cicncy will be penalized by very strict ozone depletion standards After all elements were taken into account we did not find a significant difference in the ozone depiction of conventional wing-body aircraft and the oblique flying wing when the same cruise Mach number was consid­ered. The effect OFW’s improved fuel efficiency was canceled by its somewhat increased flight altitude. According to the Chang model, the impact of a fleet of Mach 1.6 OFW’s replacing the current fleet of B747’s on the ozone layer will be less than the 2.5 reduction of the ozone col­umn proposed by NASA. This is about one fourth of the impact of Mach 2.4 conventional trans­port and ten times the impact of the current subsonic fleet.

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