Scientist: Space weapons pose debris threat

Thousands of potentially dangerous pieces of debris are already in orbit.

(CNN) -- The use of weapons in space could leave so much debris in orbit that low-flying satellites could not safely operate, according to a prominent astrophysicist. But military and other officials dismissed the claim as overblown.

The Pentagon's missile defense program envisions the possibility that powerful lasers or other weapons in orbit could help protect against enemy missile attacks.

Joel Primack of the University of California, Santa Cruz, contends that such high-tech defenses could transform low-Earth orbits into a wasteland for decades or longer.

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"Even one war in space will [encase] the entire planet in a shell of whizzing debris that will thereafter make space near the Earth highly hazardous for peaceful as well as military purposes," Primack wrote in a report presented weeks ago to an international conference on science and spirituality.

However, one of the foremost experts on space junk, Donald Kessler, has mixed thoughts about the issues raised by Primack.

"Everything he says in (his report) has truth in it, but it's exaggerated," the retired NASA scientist said. "What he is talking about is technically correct, but from a practical or economic standpoint, it is not likely to happen."

Kessler conducted groundbreaking research in the 1970s on the threat of orbital debris to satellites. His mathematical predictions that collisions would cascade into more and more collisions became known as the Kessler effect.

He was one of the first people to sound the alarm about space junk. In fact, Kessler and others think there is enough junk now to pose significant risks to spacecraft in low-Earth orbits, a contention supported by returning space shuttles, which often have dings and window cracks.

Other space dignitaries lend support to Primack, a Stanford University-trained particle physicist who helped develop the theory that dark matter helps structure the universe.

Sydney Van Den Bergh, a physicist with the National Research Council of Canada, said he raised similar concerns years ago at an international conference on space law.

And in April, astronaut Sally Ride, the first U.S. woman in space, gave a speech in which she said that anti-satellite weapons would be "disastrous."

She said debris created by their use could damage satellites traveling in low-Earth orbits, a particularly popular zone of real estate between 150 and 400 miles high that includes the space shuttle, the international space station and reconnaissance satellites.

U.S. Air Force officials said such fears are unwarranted. Lt. Col. Rick Lehner, spokesman for the Ballistic Missile Defense Organization at the Pentagon, said that the budget request for space-based programs was minimal compared with other parts of the proposed missile defense system.

"The current missile defense program is not space-based. There's some low-level research going on with space-based lasers and other space-based defenses, but the emphasis now and for many years to come is ground-based, air-based and possibly sea-based missile defense systems," he said.

Still, Primack argues that even a low-tech prelude to a high-tech space battle could prove catastrophic. An enemy could deliver giant loads of rock or metal pellets into space.

"No actual space war even has to be fought," Primack said. "Any country that felt threatened by America's starting to place lasers or other weapons in space would only have to launch the equivalent of gravel to destroy the sophisticated weaponry."

Such mini-missiles could do serious damage, going at speeds as high as 17,000 mph (27,000 km/h), 10 times faster than a rifle bullet. A marble at that speed could hit a satellite with as much force as a one-ton safe dropped three stories.

As they pulverize existing space junk and satellites, they would create even more debris and set off a chain reaction that eventually renders the orbital zone unusable, Primack said.

That scenario would likely never succeed or even happen in the first place, other space experts said.

Military satellites are hardened to resist impacts from debris already in space and future orbiters will likely become even more protected as the technology improves, said Michael Kucharek, spokesperson for the U.S. Air Force Space Command. The Colorado-based outpost tracks almost 10,000 thousands of pieces of space junk four inches (10 cm) in diameter or larger.

Moreover, such an attack would be technologically and economically daunting.

"Very few nations could do that today. Even If you were to put tens of thousands of particles out there, it would pale in comparison to what is already out there," said Nick Johnson of NASA's Orbital Debris Program Office, which monitors the threat of small space debris to spacecraft.

"We've looked at so-called chain reaction scenarios and it would require an exceptionally large number of particles," Johnson said.