Since the dawn of the space age, humans have launched amazing pieces of advanced technology to orbit. In the process, we've also created a whole lot of space junk. 。

Expendable rocket stages, defunct satellites and random bits of metal traveling at more than 17,000 miles per hour litter the space above Earth, threatening functioning satellites and people living in orbit. 。

Space junk also takes more than just a broom to clean up. A Japanese experiment expected to deploy last week was designed to test out a 70 meter electromagnetic tether that could be used to drag junk down, allowing the material to re-enter Earth's atmosphere, where it would harmlessly burn up.。

That experiment -- called the Kounotori Integrated Tether Experiment (KITE) -- failed, however, according to media reports.
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The experiment traveled to space aboard Japan's uncrewed Kounotori 6 HTV spacecraft, which also delivered thousands of pounds of supplies including food, water and hardware to the International Space Station when it docked in mid-December.。

After the HTV left the Space Station on Jan. 27, KITE was expected to deploy, but the experiment hit an unknown snag that prevented the tether from unfurling it in the week between undocking from the station and re-entering Earth's atmosphere.。

"We believe the tether did not get released," KITE researcher Koichi Inoue said, according to AFP.。

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"It is certainly disappointing that we ended the mission without completing one of the main objectives."。

These kinds of experiments are important for the future of spaceflight.。

At the moment, there are millions of bits of debris speeding around Earth. If one of those pieces of metal slams into a functioning satellite or a crew-carrying spacecraft in orbit, it could create serious --- even deadly -- issues. Even a tiny piece of space debris could damage or destroy critical equipment when it's moving at extreme speeds. 。

The scale of the problem is staggering. At the moment, NASA tracks about 500,000 pieces of space junk the size of a marble or larger to make sure these pieces of debris don't threaten any needed satellites or spacecraft in space. There are still thousands of other bits of space junk too small to track circling Earth now.
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Sometimes, the Space Station actually needs to change its orbit in order to avoid a large piece of space junk that comes too close to it. Occasionally a small piece of debris does hit the station, though that doesn't always spell disaster.。

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But other spacecraft haven't been so lucky.。

For example, in 2009, a dead Russian satellite collided with an operational U.S. satellite, producing about 700 pieces of space junk in the process.。