Re: ROCKET TOXICS

[Lenny Siegel <lsiegel@igc.org>]

AIR FORCE STUDY CALCULATES OZONE DEPLETION
FROM ROCKET LAUNCHES

 NASA continues to play down the environmental impact of solid
rocket motors - particularly their release of ozone-depleting chlorine in the
stratosphere. However, , the Los Angeles-based Space and Missile Systems
Center, a branch of the Air Force Materiel Command, is taking the issue
seriously. In November it released a report, prepared by the Aerospace
Corporation, on "Stratospheric Ozone Reactive Chemicals Generated by
Space Launches Worldwide." Based upon the known characteristics of
existing launch vehicles, Aerospace has calculated the chlorine deposition of
a typical launch for each type of vehicle. Liquid-fueled rockets, such as the
Russian Proton and Energia and the Chinese Long March, are not profiled,
because they do not release chlorine.

 Chlorine release (tons) by altitude
Launch Vehicle 0-15 km 15-60 km 0-60 km

Titan IV 78 48 126
Titan IV with SRMU 90 55 145
Delta II 17 8 25
Atlas IIAS 6 3 9
MX na 6 na
MinuteMan III na 2 na
Pegasus/Taurus 0/10 4 4/14
Shuttle 147 79 226
Ariane 5 50 57 107
H1 6 3 9
H2 22 11 33

Aerospace also calculates the aluminum oxide releases per launch, but its
impact on the ozone layer is unknown.

 The report also develops annual and long-term profiles of the chlorine
loading from solid-rocket launches based upon anticipated launch rates. It
says, "Worldwide space launches contribute over 800 tons of chlorine and
1000 tons of alumina particles to the stratosphere annually. This represents
.25% of the total inorganic chlorine produce in the stratosphere which meets
with ozone."

 Aerospace carefully compares the timing of the impact of rocket
exhaust and terrestrial releases of ozone-depleting substances, such a
chlorofluorocarbons (CFCs): "CFCs released at sea level require one to two
years to reach the stratosphere. CFCs have lifetimes of 50 to 100 years, so the
active chlorine generated by this CFC-release will continue to build up for
several years. Subsequent releases will further increase the atmospheric
chlorine. If releases cease, the atmospheric chlorine will fall to half the peak

level in 50 to 100 years. CFCs have been released for several decades at an 
increasing rate, so the atmospheric levels of inorganic chlorine from this
source have already accumulated. IN CONTRAST, INORGANIC
CHLORINE RELEASED IN THE STRATOSPHERE BY A ROCKET
RESULTS IN AN IMMEDIATE INCREASE IN ORGANIC CHLORINE."
[emphasis added]

 Aerospace documents the continuing decrease in the use of ozone-
depleting compounds such as CFCs, listing actual and projected use (not
releases) for the Space and Missile Systems Center (SMC); the Air Force
Materiel Command (AFMC), including the SMC; and a slightly dated global
estimate from the World Meteorological Organization. Please note that this
table does not present the weighted ozone-depleting potential, just a raw
measure of releases.

 Use of Ozone-Depleting Compounds (tons)
Year SMC AFMC World

1991 1,400 2,019,000
1992 29 1,120 2,049,000
1993 51 700 1,639,000
1994 51 100 1,639,000
1995 24 24 1,081,500
1996 8 8 1,081,500
1997 8 8 731,500
1998 8 8 731,500
1999 8 8 731,500
2000 0 0 320,000

 Aerospace concludes, "Because the atmospheric lifetime of a typical
CFC is 50-100 years, the backlog of accumulated CFCs in the atmosphere
will continue to contribute close to 300,000 tons of inorganic chlorine
annually well into the next century. This annual contribution is not projected
to drop to half its current level until between 2050 and 2100. This means
that projected launch-generated inorganic chlorine will rise to a level
approaching 0.5 percent of the annual level introduced by the backlog of
accumulated CFC. However, new anthropogenic releases of chlorine, while
still a small fraction of what is stored in the atmosphere, will soon be
dominated by launch-generated inorganic chlorine."

 That is, the U.S. Air Force and its contractor are warning: As the
world cuts back on the use and release of CFC's, solid-rocket launches will
soon become dominant new source of chlorine in the stratosphere.