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No sign of ozone loss from launches.

Environmental groups have recently voiced concern that exhaust from the space shuttle and other rockets could harm the protective ozone layer. But measurements taken by satellites after shuttle launches do not show any sign of stratospheric ozone destruction, atmospheric scientists report.

Solid-propellant motors used to loft some rockets pose a potential threat to the ozone layer because their exhaust contains chlorine, which in some forms can destroy ozone. Indeed, a scientific flight through a rocket's exahust plume in the 1970s detected a 40 percent decrease in ozone levels in the plume, reports Steven Aftergood of the Washington, D.C.-based American Federation of Scientists in the Sept. 20 JOURNAL Of GEOPHYSICAL RESEARCH. Aftergood suggests that launches may produce local ozone "holes" that persist for several hours.

In the same journal, Richard McPeters of NASA's Goddard Space Flight Center in Greenbelt, Md., and his colleagues respond to Aftergood's comments by examining satellite measurements of ozone in the shuttle launch area. They find no detectable ozone decrease after several launches.

This week, the American Institute of Aeronautics and Astronautics released a report examining the issue of launches and atmospheric problems such as ozone depletion, acid rain and global warming. "There is no pressing need to change the propellants of current launch systems," the report concludes. Any localized ozone loss resulting from launches would dissipate within a few hours and should not significantly affect the Earth's surface because the rockets fly in a slanted trajectory through the atmosphere, says Jerry Grey, the institute's director. On a vertical trajectory could create a local ozone "hole" through which harmful ultraviolet radiation could penetrate.

According to the report, model calculations suggest that 15 launches a year -- a number that exceeds the current launch frequency -- could decrease ozone levels over the northern midlatitudes by up to 0.1 percent. While such small changes pose no threat now, they could grow important over time, especially if launch frequency increased substantially, Grey says. The report also calls on scientists to improve on the rudimentary models currently used to aasess ozone loss.
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Title Annotation:space rocket launches
Publication:Science News
Date:Oct 12, 1991
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