The International Space Station (ISS) isnt designed to move around on its own, which presents a problem when a bit ofspace debris is threatening to smack into the station. Thats exactly what happened a few days ago, but the ESAs Automated Transfer Vehicle (ATV) happened to be docked at the station with enough fuel to save the day.

Even small objects can be extremely dangerous in orbit. Even a paint chip can cause damage to a spacecraft when it impacts traveling at almost 30,000 km/h. Its enough of a problem that astronauts aboard the ISS have emergency protocols to follow when space junk threatens the station. These objects can be almost anything parts from rocket engines, screws from derelict satellites, or even tools lost by astronauts. Theyre all moving very fast and are very dangerous. Scary stuff.

Scientists have been musing on ways to clear some of this debris from orbit with everything from giant nets to lasers. In fact, objects of this size are one of the main targets of such research as they can go unnoticed by radar until shortly before impact. One Australian company says it will be able to blast junk of this size out of the sky with lasers in 10 to 20 years, but until then we need to be able to get out of the way.

Prior to 2012, they would huddle inside the stations Soyuz escape ship and hope the station wasnt hit. In the last few years it has been possible to sue Russias Progress supply ship to move the ISS out of harms way, but that craft wasnt docked when the most recent scare happened. Luckily, the ATV-5 was connected and flight engineers took a chance.

The threat turned out to be a piece of Russias Cosmos-2251 satellite, which broke up after colliding with a second satellite in 2009. The bit of debris was about the size of your hand, but that could easily blow a hole in the stations hull if it were to hit. The calculated path of the object was within 4 km of the station, which is close enough that action needed to be taken.

ATV Georges Lematre had docked several days previously to deliver 6.6 tons of supplies to the ISS. This is a non-reusable vehicle. After making the delivery, it is dropped into the atmosphere to burn up. However, it still had enough fuel in its tanks to change the stations trajectory to avoid the satellite debris. ATV mission control did the necessary calculations and managed to fire the ATVs thrusters for a boost of of 1.8 km/h. This increased the stations altitude by 1 km, which took it well outside of the danger zone.

The ESAs ATV spacecrafts have proven to be a robust and reliable way of moving cargo in low-Earth orbit, but thats just the beginning. NASAs next-generation Orion crew transport vehicle will use an ATV-based service module for power and propulsion (seen above), making it a critical part of future manned missions. Design work on this version of the ATV capsule is expected to be completed around 2017.

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ISS performs emergency maneuver to avoid space junk impact