Space Junk

[Jamie]

Thousands of nuts, bolts, gloves and other debris from space missions form an orbiting garbage dump around Earth, presenting a hazard to spacecraft. Some of the bits and pieces scream along at 17,500 mph.

When these objects fall back into Earth's atmosphere, which they inevitably do, they behave just like any other meteor, lighting up the sky.

A 1999 study estimated there are some 4 million pounds of space junk in low-Earth orbit, just one part of a celestial sea of roughly 110,000 objects larger than 1 centimeter -- each big enough to damage a satellite or space-based telescope.

Some of the objects, baseball-sized and bigger, could threaten the lives of astronauts in a space shuttle or the International Space Station. As an example of the hazard, a tiny speck of paint from a satellite once dug a pit in a space shuttle window nearly a quarter-inch wide.

Aware of the threat, the U.S. Space Command monitors space debris and other objects, reporting directly to NASA and other agencies whenever there's threat of an orbital impact.

As of June 21 2000, the agency counted 8,927 man-made objects in the great above and beyond; some are there more or less permanently. Of the total, 2,671 are satellites (working or not), 90 are space probes that have been launched out of Earth orbit, and 6096 are mere chunks of debris zooming around the third planet from the Sun. The United States leads the former Soviet Union in the total quantity of orbital junk, but some companies and other organizations contribute significantly to the count.

But there are more objects up there.

The Space Command's electronic eyes can spot a baseball-sized object up to about 600 miles high, officials say. But at 22,300 miles up, where geostationary satellites roam -- providing weather images used by forecasters -- an object has to be as big as a volleyball to be seen. These object, moving in fixed perches with the rotating Earth, may remain in place for centuries, experts say.

And even with more than a dozen of these electronic eyes arrayed around the planet, the agency admits to not being able to see the entire sky all around the world.

Danger of getting hit on the head?

The threat to satellites and Earth-orbiting deep-space telescopes from orbiting debris is clear. But how much of this junk falls back into the sky? Does this poses a risk to the species responsible for putting the stuff up there in the first place?

In the first six months of 1999, 57 of the tracked objects re-entered Earth's atmosphere, according to Major Michael Birmingham of the U.S. Space Command. Birmingham said that 91 objects fell into the atmosphere in all of 1998, and 69 in 1997.

The most spectacular re-entry in the short history of the phenomenon was Skylab. Launched in 1973 (two years after Russia put its first space station into orbit), the first and only U.S. space station stumbled home six years later, part of it splashing into the Indian Ocean and another portion ending up in Australia.

"Most objects that re-enter the Earth's atmosphere burn-up or re-enter over water," Birmingham said, noting that nearly three-quarters of the planet is wet and a great majority of what's dry is uninhabited. "Since the space surveillance mission began, almost 17,000 objects that we track re-entered the Earth's atmosphere. Catastrophic re-entries such as Skylab are rare and the exception."

Cool space junk facts

The oldest debris still on orbit is the second US satellite, the Vanguard I, launched on 1958, March, the 17th, which worked only for 6 years.

In 1965, during the first american space walk, the Gemini 4 astronaut Edward White, lost a glove. For a month, the glove stayed on orbit with a speed of 28,000 km / h, becoming the most dangerous garment in history.

More than 200 objects, most of them rubbish bags, were released by the Mir space station during its first 10 years of operation.

The most space debris created by a spacecraft's destruction was due to the upper stage of a Pegasus rocket launched in 1994. Its explosion in 1996 generated a cloud of some 300,000 fragments bigger than 4 mm and 700 among them were big enough to be catalogued. This explosion alone doubled the Hubble Space Telescope collision risk.

http://www.space.com/spacewatch/space_junk.html

[FLO]

I find that both sad and scary :?

[Astroman]

Not a lot you can do about it, just keep your eyes open.

BTW, the second sentence is in error-actually all of it has to orbit at 17,500 mph or faster, or it would fall back to Earth sooner.

[Jamie]

Yes but the point being made is that its not all just floating about.

Some of it IS falling back to earth.

Which makes me think its not all traveling at the said speed or faster.

If it were it would never re-enter earths atmosphere.

[FLO]

Some of it IS falling back to earth.

So, instead of a tiny asteroid ending its journey across space in a blaze of glory .... it could be a bolt

[Jamie]

You got it in one mate.

[MartinB]

Just like the high seas which are full of containers which have fallen off or even dumped. A real hazard to small vessels.

[Ant]

A friend of mine saw something land in his property - he owns a rather large plot of land in Hawkwell...

When he went out and found it, it turned out to be a peice of melted Aluminium - fairly common, and most likely fell of a satalite at some point in the past.

Would have hurt if it hit you! I saw it and it wasn't small.

Ant

[The Warthog]

Interesting that some of the meteors we see may be space debris.

Based on some of the things I've read in the past, a chunk of meteor isn't moving all that fast, and isn't all that hot, when it reaches ground level. As it's only the surface of the meteorite that is burned away, the bulk of the material remains cold, and the air resistance reduces the speed of a meteorite to something that would be equivalent to being hit with an object dropped from a very tall building, or an airplane, so it may kill you, but that isn't a certainty.

I believe there is a case of an American woman being hit by a meteorite, and several houses that have been struck. The woman survived.

[FLO]

Do you suppose that the colour of the light trail is a clue ... rock burning at a different temperature/colour than steel or aluminium?

[Ant]

Without a doubt Steve, the chemical composition determins the colour.

Not sure which chemical's give rise to which colours though.

Ant

[The Warthog]

Pennies from heaven would probably be greenish-blue.

[FLO]

[Astroman]

Pennies from heaven would probably be greenish-blue.

LOL Excellent!