Those who think the air is rarefied in the ivory towers where most academics work should consider the research of a group of Harvard atmospheric scientists.

Paul O. Wennberg '88 and Weld Professor of Atmospheric Chemistry James G. Anderson are part of a team that performed chemical research in a converted spy plane 70,000 feet above the earth's surface, seeking new answers to the problem of ozone depletion.

With the aid of colleagues from across the United States, the Harvard group recently published a research article in Science reporting their work on the impact of supersonic aircraft emissions on the ozone layer.

Their article takes the story that scientists traditionally tell to explain how chemical emissions affect the earth's atmosphere, and stands it on its head.

"The fundamental tenet of atmospheric chemistry is that ozone depletion is controlled by nitrogen oxide radicals and the hydrogen oxide and halogen radicals play a much smaller part," Anderson says. "We have experimentally shown that in the lower ozone layer, the hydrogen oxide radicals are on top and the halogen radicals are dominant. The nitrogen oxide radicals play the smallest role at less than 20 percent."

The group's work was supported by the National Aeronautics and Space Administration [NASA] High Speed Research Program. Howard L. Wesoky, manager of atmospheric effects of aviation at NASA Headquarters, says that the research is a key part of a comprehensive study of the ozone layer.

"The research may have helped us to understand the photo chemistry [of ozone depletion], but we don't know the dynamics," Wesoky says.

"NASA has two programs that sponsor upper atmosphere research," Wesoky says. "We are funding studies to understand the effects of chlorofluoro carbons [CFCs] on the Antarctic ozone layer as well as studies to understand the impact of a fleet of supersonic aircraft on ozone depletion."

"NASA is funding a 150-million-dollar, 12-year study to understand the atmospheric effects of subsonic and supersonic aircraft," Wesoky adds. "Anderson's group is looking at only one element of six areas, but it is the most expensive and complex one."

Jet engine exhaust deposits nitrogen oxides into the atmosphere, where they can chemically react with and deplete ozone.

Supersonic aircraft, which currently include the Concorde and some military planes, produce these nitrogen radicals in their engines. "Estimates show that a 50 percent increase in nitrogen radicals [in the lower ozone layer] is expected from a fleet of supersonic aircraft," Wennberg says.

Supersonic Aircraft

In a speech given in December 1992, NASA Administrator Daniel S. Goldin called high speed civil transport (HSCT) research NASA's first priority for the aeronautics industry. The proposed HSCT will carry 300 people over a range of 6000 miles at almost two and a half times the speed of sound (Mach 2.4).

"This HSCT would go twice as far [as the current Concorde can] with three times as many people at one-10th the ticket price and not damage the ozone layer," Goldin said. "And with its speed, it could do twice the work of a subsonic aircraft."

The Concorde is the only civil supersonic aircraft that currently exists. Boeing is considering whether to build its own supersonic aircraft after extensive further research.

"Boeing is actively studying HSCTs," says Randy Harrison, spokesperson for the Boeing HSCT program. "We first proposed supersonic transports in the 1970s, and we had to stop our program when federal funding was canceled, but we kept a few people to continue to work on the issues."