FOR FURTHER INFORMATION CONTACT: IMMEDIATE RELEASE Barbara McGehan-NOAA PA Oct. 5, 1995 (303)497-6286
An international team of scientists has, for the first time, sampled the exhaust plume of a supersonic airliner that was flying in the stratosphere at speeds in excess of the speed of sound. These direct measurements will allow scientists to better judge the potential impact of gases and particles from such aircraft on the ozone layer. The number of particles measured in the exhaust plume was higher than expected from previous indirect estimates, a result that will be important new input to predictions of the impact of supersonic airliners on the ozone layer.
Scientists from the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the French Office National d'Etudes et Recherches Aerospatiales (ONERA), and many universities used instrumentation aboard a NASA ER-2 research plane to measure gases and particles in the exhaust trail of an Air France Concorde that was in flight at twice the speed of sound near New Zealand last October.
Principal author David Fahey from NOAA's Aeronomy Laboratory in Boulder, Colo., in a paper in the Oct. 6 issue of Science, described this accomplishment and noted that measurements taken will shed new light on the effect of supersonic transport aircraft on the ozone layer.
The research aircraft, loaded with scientific instruments, flew S-patterns along the Concorde flight track, encountering the exhaust plume several times. Its task was to "sniff the trail" of the Concorde by measuring carbon dioxide, water vapor, particles, and nitrogen-containing compounds in the plume of the aircraft.
Because carbon dioxide is the principal product of the jet fuel combustion, the scientists were able to compare the measured amounts of the emitted gases and particles directly with the amount of fuel burned by the Concorde engine. This allows scientists to use the known fuel loads of supersonic aircraft to estimate total emissions of gases and particles to the atmosphere.
Gases known as nitrogen oxides are a major concern because of their known role in depleting the ozone layer. The amounts found in the plume were consistent with previous lab tests of the Concorde engines, suggesting that pre-flight engine tests are likely to give good estimates of the actual in-flight emissions of new supersonic aircraft.
The finding of a higher number of particles in the airliner's plume than was expected is a result that will also affect predictions of the impact on the ozone layer. "The result that became evident in this study is that particles could alter the impact of nitrogen oxides on ozone," Fahey said.
Particles form when sulfur in the aircraft fuel is converted, either in the atmosphere or during combustion in the engine, to other forms. They contain a complex mixture of many substances, including sulfur-containing compounds.
From their particle measurements, the authors of the Science study calculate that a future possible fleet of 500 supersonic passenger aircraft will increase the surface area of particles in the atmosphere by an amount similar to that following small volcanic eruptions. In mid-latitude regions, such emissions have the possibility of increasing ozone loss above that expected for nitrogen oxide emissions alone. The increase in the number of particles may also affect the ozone-related processes occurring on wintertime polar stratospheric clouds (PSCs) in the polar regions. It is known that the antarctic ozone hole is caused by human-made chlorine and bromine compounds, whose ozone depletion is enhanced by the presence by PSCs in this polar region.
Further study will be needed to determine the ultimate effects on stratospheric ozone and to evaluate the effectiveness of possible options for controlling the sulfur content of aircraft fuel. But the first-of-a kind, direct measurements reported in Science will substantially improve the reliability of those studies.
This becomes significant when looking at some of the current proposals by countries to develop fleets of High Speed Civilian Transport (HSCT), similar to the Concorde. In the United States, the NASA-led High Speed Research Program (HSRP) is a high- priority national effort to develop advanced aircraft technologies. This program is also looking at the possible environmental effects a fleet of supersonic aircraft entering commercial service early in the next century, would have.
The Concorde study is an example of the effectiveness of international cooperation in the analysis of the atmospheric effects of aviation. Program managers and scientists at NOAA, NASA, ONERA and universities seized upon a unique opportunity posed by the timing of the Concorde charter flight and NASA's ER- 2 research plane. The Concorde and ER-2 pilots worked closely together to arrange details of the combined aircraft operation.
###Ed. Note: 8x10 glossy photographs of the two aircraft are available from Barbara McGehan, NOAA PA, 303-497-6286.
Listed below are other authors/contacts involved in the study:
Dr. Nicole Louisnard (co-author) Office National d'Etudes et Recherches Aerospatiales 33-1-46-235183 33-1-46-235061 (fax) Dr. Paul Wennberg (co-author) Dept. Of Chemistry Harvard 617-495-5922 James Barrilleaux (ER-2 pilot) NASA Ames Research Center 415-604-5340 Dr. Michael Kurylo Upper Atmosphere Research Branch NASA Headquarters 202-358-0237 Howard Wesoky NASA High Speed Research Program 202-358-4650