China's Tiangong-1 satellite is a reminder of space junk on us

Orbital debris, not functional satellites, make up 95 percent of the objects in this computer-generated illustration of objects in low Earth orbit.

NASA

Out of control The Chinese space station Tiangong-1 will fall to Earth in the coming weeks, but it is unlikely to cause much damage if it reaches the surface of the planet. However, there are a number of disturbing dangers among the thousands of pieces of space debris that orbit our heads and we would not like to fall in our direction in the short term.

Around 23,000 traceable objects currently orbit around the planet, according to the latest issues of the European Space Agency. Last year Harvard astronomer Jonathan McDowell analyzed more than 18,000 such objects as part of an informal "space debris census" that he presents during classes.

According to his count, around 1,500 objects that float around the Earth are currently active. Think of satellites and spacecraft. Putting it in perspective, less than ten percent of the tracking objects currently in orbit are useful to us.

Almost 3,000 pieces of space debris are dead satellites, spacecraft and other payloads that we send to orbit but are no longer in use.

Some of them are quite worrisome.

A breakdown of space debris currently tracked.

Jonathan McDowell

Among the pieces of space junk that would not want to bump into it or see it tear through the atmosphere anytime soon there are almost 2,000 rocket stages, more than a dozen nuclear reactor cores and at least 50 liquid freaky metallic stains of nuclear reactor coolant.

"I think the worst is the most important thing, the dead payloads and the rocket stages," McDowell told me. "Worst of all are rocket stadiums with residual propellant, which can then explode."

Of course, there are also reasons to sweat the little things.

Although they are likely to burn out completely if they re-enter the atmosphere, it is estimated that around 166 million spatial fragments less than one centimeter in size are circulating above. All these debris can orbit the earth at several thousand miles per hour, acting as small projectiles that can threaten the integrity of operational satellites.

The more debris occupy space in orbit, the greater the chances of some kind of catastrophe the collision with a space station that drives the plot in the 2013 film "Gravity." A possible scenario of the worst case is something called "Kessler Syndrome" in which collisions in low Earth orbit lead to a cascade of more impacts and a proliferation of so much space junk that access to space becomes impossible.

Given our dependence on satellite technology, this could be a big blow to society that could possibly delay us technologically for decades or worse.

Our problem of space debris worsened considerably in 2007 when a Chinese anti-satellite weapon was tested in orbit on a Chinese weather satellite. The space missile destroyed its objective and created thousands of new pieces of debris in the process. Only two years later, a collision in 2009 between a defunct and uncontrolled Russian satellite and an active Iridium commercial satellite was added to the waste account.

Unfortunately, space debris is a problem that will only get worse; some researchers have even come to warn that it could accidentally trigger the war .

It's not all bad, though. If you ever find yourself shaking in a future space station mission, you may be able to recover one of the three dozen insulating blankets that McDowell estimates are in orbit to heat the interior of your spacecraft.

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