Thursday, March 25, 2010

Rocket Smoke is Like Cigarette Smoke

This image of a Soyuz rocket plume was taken far downrange from the launch site and shows the second stage of the Soyuz, which burns liquid oxygen and kerosene, in the upper stratosphere or lower mesosphere. The visible plume here is sunlight reflected from soot generated in the engine. The size of these soot particles has never been measured and is not well known but the particles likely have a diameter of about 0.1 micron. This is the same size as smoke from a cigarette which also has a bluish cast, for the same reason. The tiny soot particles preferentially scatter blue light.

What does soot from rocket engines do in the stratosphere? It absorbs sunlight and heats the surrounding air a little bit. Is it significant? Climate models must be run to answer this question.

Thursday, March 4, 2010

What Might Have Been Thursdays

The Space Transportation System. The end of the Space Shuttle program is 4 or 5 flights away. I was just graduating from the University of Michigan when the first Space Shuttle was launched in 1981. Much has been written about Nixon's decision to press ahead with the Shuttle and the economic arguments that were based on projections of about 50 launches per year. That's a launch rate about an order of magnitude higher than what the Shuttle actually managed over the life of the program. Which means, of course, an order of magnitude larger emissions into the stratospheric each year.

By the time we appreciated how chlorine compounds and particles control stratospheric ozone, it was already clear that the Shuttle would never fly once a week. So global models for 50 launches per year were never run. How would 50 Shuttle launches per year affect ozone and climate? We will never know.