New radar systems, saucer-like hull patch kits and new ceramic shielding are being brought into the effort and more exotic solutions are in the offing. The ideas include lining the walls of spacecraft and spacesuits with spider silk to absorb impacts, using ball bearings to plug punctures, sweeping debris aside with laser "brooms," or building robots to serve as roving garbage scows.
The problem is compounded as the amount of debris grows on its own. Larger pieces become many more smaller pieces as their orbits decay and debris collides with each other. Moreover, debris producing accidents with live spacecraft do occur, leaving enough material in orbit to concern spacecraft operators worldwide.
A NASA illustration referred to as the "beehive" depicts Earth shrouded by a swarm of catalogued debris that's pushing toward 10,000 items, and reflects the fact that millions more smaller items aren't precisely charted.
Last year, the International Space Station had to dodge a foot clamp dropped by astronaut Jim Voss during a spacewalk before it swung around the Earth again. The French military had to improvise a way to keep a satellite stable when its balance boom was sliced in half after colliding with the remains of one of their own Ariane rockets.
Still, no catastrophic crashes have occurred to threaten astronauts' lives, but the odds have so far been on our side, observes NASA's Nicholas Johnson, the resident space junk expert at the Johnson Spaceflight Center in Houston.
Johnson, however, downplays the panicked assessments of the danger from a junk belt surrounding our planet. He discounts the "lightning strike" analogy for debris collisions so often invoked by outsiders trying to convey the rarity of such crashes.
Lightning, he emphasizes, is far more common and it doesn't usually threaten an investment of hundreds of millions or even billions of dollars -- and repair crews aren't stuck hundreds of miles out of reach.
Eyes Wide Open
Erring on the side of caution, space agencies and private companies are working to eliminate risk. The first hurdle to overcome is a significant blind spot. At present, space agencies can steadily track only pieces of debris that stretch more than four inches (10 centimeters) across.
NASA will cast a cold snake eye on that problem in October when it makes use of the Cobra Dane Radar System on the Alaskan island of Shemya. Cobra Dane was designed to give early warning of ballistic missile attacks using an L-band phased array. That powerful hardware should bring detection levels down to two inches (5 centimeters), Johnson said.
The Japanese government and several nonprofit groups also are joining the effort, building two new near Earth orbit scanning facilities in Okayama, a prefecture better known for growing peaches. The stations are nearly complete and in many ways already operating.
The Kamisaibara Spaceguard Center uses radar to detect debris in LEO, while the Bisei Spaceguard Center uses 20-inch (50 centimeters) and 39-inch (one meter) optical telescopes for such observations. Next year, Japan's National Space Development Agency (NASDA) will start using its new Central Processing Station at the Tsukuba Space Center to crunch data collected by the spaceguard centers to calculate the orbits of registered debris.
European resources also are dedicated to the space junk hunt, including a new 39-inch (one-meter) telescope in the Canary Islands, but they and the Japanese rely on U.S. Space Command data for the safety of their launches, Johnson said.
"They will not track on a routine basis 10,000 objects like we do. The Russians have equipment to feed them routine information though. It's not quite as good as ours, but it's very, very close," Johnson said.
NASA also is able to take snapshots of orbital debris as small as eight-hundredths of an inch (two millimeters) across using a wide network of ground stations, but such objects can't be tracked consistently yet, Johnson said.
Instead, statistical modeling is used to calculate probable hot zones of debris and how forces like solar wind, molecular oxygen and magnetic fields push around those flecks. One bit of help in increasing NASA's knowledge base came from a surprising source – mirrored balls made by school children, which provided oodles of data on orbit decay caused by those influences.
All of these programs, however, still leave space voyagers nervous at the prospect of stepping into a vaguely understood spinning obstacle course of millions of small, bullet-like shards. Indeed, the International Space Station (ISS) is expected to be hit 100,000 times in its twenty-year life. The immediate urge is to simply make them all go away. One proposal called for "a classic garbage scowl.
"It's technically feasible but very difficult and very expensive – not cost effective at all," Johnson said.
A team of researchers from Massachusetts Institute of Technology and NASDA conceived robots that could be deployed from the space station, or an independent station, and using clamps and magnets remove dangerous debris. However, costs were much higher than maneuvering craft away from jeopardy, or passively surviving hits.
Build a Better Spacecraft
It was Fred Whipple, the renowned cometary astronomer, who came up with the idea for the spacecraft shielding that NASA devised decades ago. The design is simple – a bumper layer of aluminum absorbs impacts and turns that kinetic energy into heat. Small debris is thus turned into liquids and vapor before it can move onto the main hull of the craft.
Layers can be added to the basic design, and many spacecraft including the ISS supplement the shield with ceramic materials like Nextel and Kevlar, which is perhaps best known as the stuffing in bullet proof vests. After examining other concepts, the Japanese also chose the Whipple idea for their new Kibo ISS module set for attachment in 2004, NASDA engineer Kuniaki Shiraki told SPACE.com.
More exotic materials might also be used in the construction of future spacecraft. Carbon nanotubes have become a hot item of discussion across all fields of engineering because, in part, the cylinders constructed from hexagonal links of carbon atoms are believed to be perhaps the strongest manmade material.
One primary inventor of ways to synthesize them, Nobel Laureate Richard Smalley, is right down the road from Johnson Space Center at Rice University.
"We are certainly talking to them," Johnson said, but so far only tiny strands have been produced, and at great cost. It may be a decade before large scale manufacturing of carbon nanotubes is achieved.
A more bizarre possibility is that astronauts may one day owe their survival to spider silk.
Science Fact Meets Science Fiction
Nexia Biotechnologies made headlines a few years ago with its "Spider Goats" -- transgenic animals that can produce an approximation of spider silk in their mammary glands.
The proteins are marketed as BioSteel and the company continues to refine them to edge closer and closer to nature's product. The company also is researching ways to grow it in plants. Dragline spider silk – the kind used by the creatures to raise and lower themselves – has long filled engineers with envy because of its toughness.
"Spider silk is not as strong as Kevlar, but spider silk is two times "tougher" than Kevlar. Toughness refers to the ability to absorb kinetic energy," said Mark Kaufmann, vice president for of corporate development and biopharmaceuticals at Nexia.
While Kevlar can support more weight than spider silk, it's more brittle, he said. BioSteel would allow enough give to stop more debris without getting punctured.
What that means for mission planners, Kaufmann said, is that while in tight astronaut suits BioSteel wouldn't afford much protection. It might be great as a layer inside the space station walls -- it's too heat-sensitive for the exterior -- because there's enough room for a skin of it to stretch a bit on impact. However, like nanotubes, no one has produced BioSteel in sufficient quantity to seriously consider it for near-term projects.
Another approach, designed by Hidehiro Hata at the Kyushu Institute of Technology, is to fill a double hull with balls that would be sucked into a small breach like the proverbial Dutch boy's finger in the dyke. This invention wouldn't be a true defense or even an automatic repair job, but it would slow the gush of escaping air from seconds to minutes, giving astronauts time to escape.
"It's a very interesting idea but it's not ready yet for the Kibo," said Shiraki, who heads the module's shielding program.
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