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 You're resting comfortably in the passenger seat, so your
eyes glaze over as they observe one of the most typical sights of travel:
litter. A used toothbrush; black bags of various kinds of garbage; a lonely
glove; a broken camera; misplaced pliers and a wrench; many, many needles; a spatula;
some urine; a…tank of ammonia?
You reach for the fountain drink in the cup holder and just
as you throw it through the window-SPLASH! It rebounds off the glass and into
your lap, floating Diet Coke into your eyes, onto your clothes, and all over
the dashboard. Someplace, a
crying Indian begins to laugh.
In your daze you forget that you're in SpaceX, and the
rubbish you've witnessed is the result of nearly 75 years of littering, and the
aforementioned trash is just an example of some of the more indiscriminate
abandonment left floating in the 1,200 mile-high orbit around Earth. Also left
behind: burnt rocket stages, defunct satellites and broken spacecraft, all of
which have been left behind without a second thought.
 Much as the Keep American Beautiful campaign encouraged
Americans to take responsibility for their litter, a new campaign must be
envisioned to keep our low Earth orbit (LEO) clean. While the Earth can degrade
and decay many of the materials left in her streams and on her soils, our
thermosphere and exosphere cannot, and if we continue to cloud these resources,
we may never be able to explore beyond them.
Currently, NASA tracks about 19,000 separate pieces of space
debris, which is a small fraction of the estimated 500,000-600,000 items which
are larger than 1 cm. NASA tracks these items for two reasons: to prevent
misidentification as a foreign missile or spacecraft, and to prevent collisions
between debris and active satellites and spacecraft. On two occasions, flecks
of paint have severely damaged the windows on space shuttles, demonstrating the
catastrophic effects that even miniature debris can have fast-traveling
spacecraft. In 2009, the first hypervelocity collision between two full-sized
spacecraft occurred, when a telecommunications satellite and a Russian Space
Forces satellite collided at 42,170 mph. Over 2,000 pieces of large space
debris resulted from this collision and several times this debris has
interfered with other satellites or the International Space Station.
 What's more, debris in space experience what is known as
Kessler Syndrome. The most useful range of the exosphere is between 500 and 930
miles, which is where most artificial satellites are placed, and as a result
where the most space debris remains. This remaining junk continuously smashes
into other items, generating numerous smaller pieces of debris. As more
satellites enter this low Earth orbit and many older satellites are abandoned,
the chances of collisions increase exponentially. While atmospheric drag, lunar
perturbation and solar wind eventually force these items to reenter Earth's
lower atmospheres, this process can take thousands of years. In theory, the
density of small but perilous items in LEO could render it impassable.
This leaves Earth-bound scientists and engineers with a
question: how do we ensure space flight beyond LEO, when it's likely to be
cluttered beyond value in just a century?
Currently, DARPA is developing a robotic salvage satellite
called Phoenix, which will remove usable parts from abandoned satellites. Fortunately, DARPA has made a
rather dreary video on the project. For Phoenix's first test, it will
remove the antenna from an abandoned rocket stage and reattach the antenna to a
new type modular satellite. DARPA plans to raid 10 satellites for parts by the
end of 2015 to demonstrate the project's feasibility. So, at least some of the
solution comes from recycling components that are already in space, but that
does little in regards to already existing debris.
Several other solutions have been visualized for pieces of
junk. A "laser broom" consists of a high-power laser which pulses beams at
small pieces of small debris in  LEO. However, the laser broom would only alter
the path of the debris, not force it out of orbit, and would cost well over
$500 million. The laser may also further fragment some pieces of debris, which
would only compound the issue. Other proposed solutions include: capturing
clouds of debris together into large clusters composed of ice or aerogel;
inflatable balloons with large nets; electromagnets; or "maid" satellites which
will capture items of space debris and then eject them out of orbit, or place
them into graveyard orbits where they would eventually fall back to Earth. One
of the best-received ideas yet has been the Space Sweeper with Sling-Sat, or
4S, which is featured in the video at left. This solution is fuel efficient
and essentially bumps the debris into a more favorable orbit.
The eventual solution to space debris isn't in the near
future. A liberal estimate would place mankind's first serious attempts at
debris removal occurring by 2025. However, the international (intergalactic?)
laws of space have yet to be decided upon, meaning that many questions arise
over what to do with debris. Is it the owner's responsibility? What if they
oppose another group interfering with their property? Who is responsible if a
fatal accident occurs because of space trash? These are questions currently
beyond our scope of understanding, but for now we're "Sitting on the space junk,
what are [we] to do?"
Resources
Wikipedia - Space debris
NASA - Orbital debris FAQ
Space News - DARPA Lookin for 10 Retired Satellites...
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Re: Keep Low Earth Orbit Beautiful
