Artist's conception of a robotic retrieval spacecraft approaching a target asteroid. (NASA)

The Great Asteroid Grab

Instead of astronauts going to the rock, the rock will come to them.

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The Keck study proposes that once the spacecraft reaches the asteroid, it would deploy a cylindrical fabric bag, move close to the asteroid, match its spin and gently capture it (see animation here). Then it will de-spin the asteroid and take it to the Moon. Lightfoot told reporters this week that NASA’s OSIRIS-REx mission to collect and return a sample of asteroid 1999RQ36, scheduled for launch in 2016, will serve as an important precursor.

With the asteroid in the bag and on its way to the Moon, planners must decide where to put it and how to organize a human spaceflight mission to rendezvous with it, study it and examine its potential for usable resources like water and rare earth minerals. The NASA budget has allotted $40 million next year to study this phase of the mission.

NASA briefers said they would use the agency’s new Orion spacecraft, currently under development, as the basic vehicle. Although the agency did not specify how it intended to accomplish the rendezvous, planners have acknowledged that they are considering at least two options.

The first, and simplest, would put the asteroid in lunar orbit and have Orion rendezvous with it there. If something went wrong and the asteroid destabilized, it would simply plunge to the surface of the Moon.

A more ambitious possibility is NASA’s so-called “Gateway” project to put Orion in orbit around Lagrange 2, a spot on the far side of the Moon where the gravitational pull of the Moon and the Earth cancel each other out. Orion would need far less fuel for station-keeping at L2 than in lunar orbit.

L2’s disadvantage is that objects there have a tendency to drift, and the asteroid could fall to Earth, although Friedman says it would most likely burn up in the atmosphere. NASA has been studying Gateway for almost two years, but has not yet made a decision how far to take the idea.

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