How Space Junk is Like a Buzzard

From Wired

In a paper to be published in Acta Astronautica, physicist Philip Metzger of NASA's Kennedy Space Center and colleagues describe a technique to plot the paths and determine the densities of worrisome detritus kicked up during launch. This method could help flight engineers know instantly which pieces of debris threaten the spacecraft.

"We combined together two different types of software that can do on-site analysis," Metzger says. "In the future we can take video of the launch environment, and the software can automatically ... conclude what were the sources and the makeup of the debris." The paper was published online at arXiv.org on October 22.

"For manned missions, this is very important. I'm surprised it's not been done yet," comments Nilton Renno of the University of Michigan, who studies how rocket plumes from Mars landers affect the Martian surface. "It will improve our confidence in the assessment of potential damage, not just for the space shuttle but for any other future spacecraft."

In 2003, the Space Shuttle Columbia was damaged by a dislodged piece of insulation. The damage caused the shuttle to break apart upon reentry, killing all seven astronauts on board. The event showed how crucial it is to catch debris damage early.

The need for better tracking systems during launch was highlighted during the Space Shuttle Discovery launch in May 2008, when several thousand bricks blew out the end of the flame trench under the shuttle. Simultaneously, a mysterious piece of debris flew high into the air near the shuttle, apparently from the flame trench. Had the mystery object been a brick, it could have damaged the shuttle and put the crew at risk.

To identify the object, Metzger and colleagues took advantage of NASA's bird watching system. In 2005, during the first launch after the Space Shuttle Columbia disaster, a shuttle was threatened by another flying menace: a vulture that smacked into the external tank during takeoff.

Since then, engineers have tracked vultures as a routine part of launch by taking pictures of the launch area from two different angles. Combining the pictures gives a three-dimensional view of the region, so moving objects like birds and bricks can be found and followed. Metzger and colleagues have used similar measures to model how a rocket plume could scatter dust and boulders in the low-gravity environment of the moon, threatening nearby lunar outposts.

For the May 2008 Discovery launch, Metzger's team used images from the vulture-tracking system to plot the mystery object's trajectory, then did some simple ballistics analysis to figure out the object's density. Neither technique is complicated or new, but the combination of images and ballistics had never been used for launch analyses before.

Click here for more