Needed: a huge vacuum cleaner that can roam around in low Earth orbit.

While the danger of catastrophic collisions in space is rising steadily, cost and feasibility issues mean development and deployment of any space vehicle to remove deadly orbiting debris won’t occur soon, an expert NASA official said.

"Technically, you could do that," said Nicholas L. Johnson, chief scientist for orbital debris at Johnson Space Center, home of Mission Control. "But the problem is, it’s very, very costly. If you were to launch one vehicle like that to go latch onto one old rocket body and bring it back, that’s a tremendously expensive operation."

He spoke in an interview with Space & Missile Defense Report.

What might be more cost-effective, as far as the average price of each piece of dangerous space junk removed from orbit, would be a space vehicle that could round up many pieces of space junk or dead satellites and shove them into a self-destruct trajectory, to burn up on reentry into the atmosphere, Johnson said.

"If you could have a vehicle that could go up and collect a couple of dozen and bring them back, that maybe is a little more attractive," he indicated.

"So we’re looking at it, but we really haven’t found the solution yet," he explained. "It is a very, very difficult problem." That would be true even if the goal is merely to send the objects into the atmosphere to burn up, rather than placing them in a space vehicle that would bring them down to Earth unharmed, he said.

He spoke after a hearing of the House Science and Technology Committee space and aeronautics subcommittee that probed the increasing danger of collisions in space. (Please see full story in this issue.)

Just to snag these lethal, useless hunks of junk and shove them down near the top of the atmosphere is "a tremendous energy challenge," Johnson observed.

First one must launch the clean-up vehicle from Earth into orbit, he said.

Then it would have to latch onto the debris, and shove it down toward a fiery reentry.

And then the clean-up vehicle would have to repeat that process, over and over, he said.

True, "there are lots of different ways of doing it with conventional propellant," he said. Or NASA might use "what we call electrodynamic tethers, which don’t have as many needs for resources. But we haven’t actually perfected that technique yet."

A space tether involves a long wire that can be attached to an orbiting object. The tether interacts with the magnetic field around Earth, the magnetosphere, to provide propulsion for a space vehicle or, in this case of space junk, to provide drag that slows the junk until it falls out of orbit and hits the atmosphere, burning up on reentry.

With a tether, there would not be "a need for as many resources, but we haven’t actually perfected that technique yet," Johnson said.

Even then, this would involve major money, with no multi-year cash payoff such as one might have by spending the same amount to launch a commercial telecommunications satellite.

"The vehicle has to have not only the propulsion system, it’s got to have an attitude control system, it’s probably going to have to have a communications system, it’s got to have a power system, so this little thing now is a little bigger," and more expensive.

All this doesn’t mean that one should completely lose hope of ridding space of lethal junk, he said. "It’s not impossible, but try to find something which is economically viable, is the real challenge," he said.

So the time may not yet have arrived to develop and launch a space vacuum cleaner. "Not yet, but maybe one of these days," Johnson said.

It remains to be seen whether that system would involve a vehicle that would maneuver around in orbit, attaching shock cords or plastic loops (such as those on soft-drink six- packs) to pieces of space junk, then taking the bound-together mass of trash, attaching it to a thruster, and aiming it back into the atmosphere.