Space is
littered with millions of bits of orbiting garbage leftover from missions. The
flying flotsam can delay launches and could potentially smash into spacecraft. Now
some creative ideas are emerging for how to sweep up the junk. One idea even involves
an oversized NERF ball.
The
graveyard of ghostly scraps from satellites and other craft continues to grow.
Last year, the intentional destruction of China's Fengyun-1C
weather satellite sent at least 150,000 bits of orbital debris less than a
half-inch (one centimeter) across and larger into space, according to NASA's
Orbital Debris Program.
On Feb. 20,
another load of debris was scattered into space when the U.S. Navy shot down a wayward
spy satellite above the Pacific Ocean. Some 3,000 scraps spewed into space,
each no larger than a football in size, adding to the cosmic clutter.
The
trashiest region of space lies within low Earth orbit, located at 1,243 miles
(2,000 kilometers) above the Earth's surface. Space junk can also be found to a
lesser degree in geosynchronous orbit—situated higher at 22,235 miles (35,785
km) above the Earth.
The U.S.
Space Surveillance Network is tracking about 18,000 orbiting objects of debris
about two inches (five centimeters) in diameter and larger.
The space
around our planet is also polluted by millions to tens of millions of smaller,
marble-sized pieces of debris. In order to officially catalog derelict debris,
scientists involved need to identify each object's size, the mission it's
attached to and its orbit.
Because the
trash zips around the planet at around 4 to 5 miles per second (7 to 8
kilometers per second) at least in low Earth oOrbit, the physical makeup of space
debris — especially those pieces that are five centimeters and larger — is
not really important.
"It could
be made out of Jell-O or foam or stainless steel. When it's that big, it
travels at orbital velocities and it hits something else, it's going to be a
bad day," said Nicholas Johnson, program manager and chief scientist of the
NASA Orbital Debris Program Office at the Johnson Space Center in Houston,
Texas.
Ideas for
tidying up space range from the mundane, such as space tethers, to the exotic,
such as trash-truck-like craft. Johnson says, however, that none of the
proposals are feasible as yet.
Trash
pile-up
Rather than
clogging up waterways and landfills like Earthly litter does, space debris has
the potential to bang up working spacecraft along with their crews.
To
date, there is only one recorded incident of a collision in which the debris
was large enough to track. In 1996, a French satellite called CERISE was struck
by a piece of a French rocket that had exploded 10 years earlier.
Normally,
spacecraft can use information from tracking systems to dodge and avoid these
collisions with larger objects. But small pieces of orbital
debris routinely smash into and ding spacecraft, such as the space shuttle.
"It's
not a near-term operational issue," Johnson said. "But it is
something that, like any environmental problem, if you ignore it, it will get
much worse and it could get to the point where remediating the environment is
much more difficult and expensive than simply preventing it from becoming so
bad."
To make
matters worse, debris eventually begets more debris. Bits of space junk
constantly collide with their neighbors, with the current smash-ups involving
small pieces hitting larger vehicles and producing little extra debris. But
that could change.
"It's
a regeneration process that is going to happen," Johnson told SPACE.com.
"The only way to prevent it would be to go up there and start removing these
large derelict spacecraft and launch vehicles."
Litter
bugs
Debris
collisions are just a piece of the trash pie. Accidental explosions of old
rocket bodies and other vehicles are the main contributors to debris in space.
While not the primary litterbugs, spacecraft at the end of their lives can
contribute to cosmic trash. Currently, the international space community has
followed guidelines for preventing accidental explosions as well as for
end-of-life disposal. That means removal of spacecraft from low Earth orbit
within 25 years of their launch. Craft in geosynchronous orbit nearing old age
get bumped into a higher orbit, where they won't interfere with other geosynchronous-orbiting satellites.
Even so,
last year set a new record for the amount of space debris.
"The
principle reason was the Chinese anti-satellite test," Johnson said.
"That event alone far exceeded the debris generated in any other year,
ever. Unfortunately, it's very long-lived debris; it will be up there for
decades or even a century or more."
Cosmic
collectors
The
international space community, Johnson said, has brainstormed and experimented
in efforts to concoct a way to clean up the graveyard
of space for the past 20 years or so. "We haven't found a single
concept which is both technically feasible and economically viable,"
Johnson said. "In the future if launch costs go down dramatically, which
we always hope will happen but never does, or if we come up with new
technology, the equation may change and all of a sudden a previous concept that
was not viable could become viable."
Johnson is
co-author of a new report set for publication next year that details a review
of "clean-up concepts." Ideas range from the relatively mundane to the exotic,
though none "meet all the requirements for a viable remediation
technique," Johnson said.
One of his
favorite ideas involves launching a giant NERF ball spanning a mile (1.6 km)
across, which would sort of field the orbiting debris. As small particles pass
through the foamy ball, they would lose energy and fall back to Earth more
quickly.
Raining on
this sporty idea, however, are technical issues. "The NERF ball itself
would fall out of orbit pretty quickly, because it's so lightweight relative to
its size; and it's non-discriminatory, so it could accidentally run into
operational spacecraft and that's not a good idea," Johnson said.
Some
other ideas
Ground-based
or space-based lasers could also perturb orbits and push the junk to lower
altitudes so they would fall back to Earth quicker. (The glitch: Lasers are
very expensive and limited in the number of objects they can interact with.)
Trash-collector
vehicles could rendezvous with a chunk of debris and latch onto it before
dragging it into a lower orbit, or higher orbit, depending on its current
location.
Specially-designed
vehicles could rendezvous with old rocket bodies, for instance, and attach a
propulsion system or so-called drag augmentation device onto the object. The
result would quicken the debris' descent to Earth. "That vehicle could
attach that device to an old satellite and then maneuver to another satellite
and attach another device, etc., etc," Johnson said. (The glitch: The vehicles
and operation would be complicated and costly.)
Or, long,
thin wires called tethers
could help to bring down objects. The most promising tether concept involves
attaching the tether to a spacecraft prior to launch. (The glitch: Even though
tethers work on paper, "unfortunately, we haven't had a successful
demonstration yet," Johnson said.)
To date,
most of the remediation research and experimenting has involved only academic
institutions and national space agencies.
"There
is not a business base yet for doing this," Johnson said. Though he
doesn't expect truly feasible ideas for remediation, and the associated
business opportunities, in the near-term, "that doesn't mean we're not
going to keep looking and trying."
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