This blog provides commentary on interesting geological events occurring around the world in the context of my own work. This work is, broadly, geological fluid dynamics. The events that I highlight here are those that resonate with my professional life and ideas, and my goal is to interpret them in the context of ideas I've developed in my research. The blog does not represent any particular research agenda. It is written on a personal basis and does not seek to represent the University of Illinois, where I am a professor of geology and physics. Enjoy Geology in Motion! I would be glad to be alerted to geologic events of interest to post here! I hope that this blog can provide current event materials that will make geology come alive.

Banner image is by Ludie Cochrane..

Susan Kieffer can be contacted at s1kieffer at gmail.com

Sunday, March 6, 2011

NASA Rocket Failure and Mount St. Helens

The NASA Glory rocket being loaded for launch
Photo from NASA
Earlier this week (March 4), NASA attempted to launch a new climate monitoring satellite, Glory, into orbit with a Taurus XL booster.  The Taurus XL is about 9 stories tall, and was lanuched from Vandenberg Air Force Base in California.  The Glory satellite had cost $424 million to develop and build. The nosecone cover, visible in the photo to the left, covered the satellite and failed to separate during the trip into orbit.  The rocket is believed to have crashed into the southern Pacific Ocean near the Antarctic.  This is the second launch failure of a Taurus rocket in two years.  In 2009 another climate satellite, the Orbiting Carbon Observatory, also ended up in the south Pacific.  The rocket is built by Orbital Sciences Corp. in Virginia.

A video of the launch is about half way down this WWW page.  It is worth watching for several reasons, the saddest one being the problem at the end. It has narration, the stage 1 separation comes at about 1:45, and at 2 minutes into the mission, all systems nominal.  The tape skips ahead to 5 minutes at 2:40 into the tape and the narrators indicate that the vehicle velocity is not correct and that it is likely that the fairing had not separated. In researching this, I found a site called "Space Launch Report" that appears to track space launches around the world.

Rockets work because of Newton's Third Law of Motion. Mass accelerates through the rocket engine and out of the rocket with a certain velocity and at a certain overpressure at the exit plane (overpressure is the difference between the pressure of the gas and local atmospheric pressure).  In response, the thrust force is applied to the engine in the opposite direction. A calculation of thrust has two terms: the first is the mass flux times the velocity, and the second is the overpressure times the area. Thrust changes continuously throughout a launch because the mass flux and velocity of the gas change, and because the overpressure changes as the rocket rises higher and higher into thin atmosphere.

It is easy to envision the overpressure change by watching the change of shape of the exhaust plume as the rocket rises (as shown on the two images above).  Near the surface of the earth, the plume tends to be fairly "straight," whereas it flares out in a very pronounced manner as the rocket rises into the near vacuum of space. You can see this change in plume shape on the video of the Gloria launch referenced above, worth going back for a second look!

In my next blog, I'll discuss how this rocket technology is relevant to volcanic eruptions, and particularly, to the eruption of Mount St. Helens in 1980.

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