Sunday, February 28, 2010

Commercial Space: Falcon 9

First flight of the Falcon 9 will take place in the next few months. This hydrocarbon fueled rocket introduced by the Space Exploration Technologies Corporation (informally, Space-X) is expected to be able to place about 5 metric tons into LEO. The propellants for Falcon 9's nine engines are conventional kerosene (RP-1) and liquid oxygen; important emissions include water vapor, carbon dioxide, and soot. A heavy lift version of Falcon 9 is planned. Kerosene fueled rocket engines emit about 3 times more carbon dioxide (per unit mass delivered to orbit) than standard solid rocket motors.

Sunday, February 21, 2010

Three Interesting Plume Phenomena

This video of a recent Atlas V launch well illustrates a few of the many interesting ways that the exhaust plume of a kerosene fueled rocket engine interacts with the atmosphere.

First, notice the contrail that begins to form at 1:41 (video time) and continues for about the next 10 seconds. This is a typical aircraft type "linear contrail" consisting of ice particles.

Second, notice that the classic rocket plume "flame" (the radiant plume) shrinks with altitude. By 2:30, with the rocket well into the upper stratosphere, the radiant plume has become small and a wide and faint white-bluish plume, likely soot particles from the RD-180 rocket engines, becomes prominent.

Third, this video shows the acoustic waves that propagate from the vehicle and modify the surrounding cirrus cloud particles. In this video you can also see the faint soot trail behind the Atlas V rocket.

These localized plume phenomenon hint at the cumulative and global impacts of rocket emissions.

Thursday, February 11, 2010

Commercial Space Transport and Science

The Next-Generation Suborbital Researchers Conference will be held next week. The idea here is that the science community can buy into the emerging suborbital space tourism sector. Instead of launching expendable sounding rockets, researchers would buy rides into the upper stratosphere, mesosphere, and lower thermosphere on reusable tourism vehicles. There is good potential for new data from little known regions of the atmosphere and more science at lower cost. Should the scientific community also investigate how the cumulative emissions from these vehicles will affect climate and ozone?

Monday, February 8, 2010

Sulfuric Acid Seduction

So-called "geoengineering" is a popular thing to discuss, even in polite company. The idea is simple: inject sulfur dioxide gas into the lower stratosphere and add a little bit - a few percent - to the natural sulfuric acid cloud layer there. The man made sulfuric acid particles would reflect a little bit more sunlight back into space than normal, thus cooling the planet. Massive volcanoes do this every decade or so and we think we understand how gases turn into particles and reflect sunlight and so on......

This plot is from a paper by Keith, Parker, and Morgan (Nature, 436, 2010) called "Research On Global Sunblock Needed Now". This idea is seductive. Relatively cheap and quick. But there are problems. First in line: this "purposeful pollution" of the stratosphere would cause a lot of ozone depletion, maybe 20%. Maybe more.

Second: It is sort of like a drug; each sulfur dioxide injection is temporary so once you start you can't stop. Look at the plot.

So where is the trade a good one? How much global ozone loss can we accept for a given amount of global cooling? Who decides?