The International Space Station and other spacecraft that fly relatively close to Earth have a new orbital road hazard — a cloud of more than 500 pieces of debris caused by the explosion last month of a Russian upper-stage rocket.

The orbital explosion of a Briz-M rocket motor was Russia’s third since 2007. The rocket motors were left stranded in elliptical orbits that overlapped where the space station and numerous other satellites fly.

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The latest debacle also left behind two fully fueled spacecraft, notes NASA in its latest issue of Orbital Debris Quarterly News.

“The launch malfunction occurred when the Briz-M upper stage, carrying the Telkom 3 and Express MD2 spacecraft, shut down shortly after the start of the third of its planned four maneuvers (on Aug. 6). At the time, the stage was in an orbit of 265 km (165 miles) by 5,015 km (3,116 miles) with an inclination of 49.9 degrees (relative to the equator). Both spacecraft were later autonomously released from the stage,” NASA noted.

As feared, the rocket motor exploded mid-October, creating a new cloud of space debris.

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The Russian news agency Interfax reported that the explosion generated about 500 pieces of debris. The previous Briz-M explosions each produced about 100 pieces of debris, according to NASA’s orbital debris program office.

Another Briz-M upper stage from a botched August 2011 launch is still in orbit and has not yet ruptured.

In all, there are more than 21,000 pieces of orbital debris larger than 10 cm ( about 4 inches). Scientists estimate there are about 500,000 pieces of debris between 1 and 10 centimeters (about 0.4 inches to 4 inches) and more than 100 million pieces of space junk smaller than 1 centimeter.

Images: Top: File photo of a Briz-M upper-stage rocket motor which broke apart Oct. 16. Credit: Khrunichev. Credit: NASA.