Capturing an Asteroid: How NASA Could Do It
Credit: Rick Sternbach/Keck Institute for Space Studies

NASA's bold plan to drag an asteroid into orbit around the moon may sound like science fiction, but it's achievable with current technology, experts say.


The plan aims to place a roughly 23-foot-wide (7 meters) space rock into a stable lunar orbit, where astronauts could begin visiting it as soon as 2021 using NASA's Space Launch System rocket and Orion capsule, Nelson said.


"Return of a near-Earth asteroid of this size would require today’s largest launch vehicles and today’s most efficient propulsion systems in order to achieve the mission," Lewicki, who served as flight director for NASA's Spirit and Opportunity Mars rovers and surface mission manager for the agency's Phoenix Mars lander, wrote in a blog post Sunday (April 7).

"Even so, capturing and transporting a small asteroid should be a fairly straightforward affair," Lewicki added. "Mission cost and complexity are likely on par with missions like the [$2.5 billion] Curiosity Mars rover."

Spurring solar system exploration

NASA's idea is similar to one proposed last year by scientists based at Caltech's Keck Institute for Space Studies in Pasadena.



The mission would also help develop asteroid-mining technology, advocates say, and advance scientists' understanding of how our solar system took shape more than 4.5 billion years ago.

Asteroids "probably represent samples of the earliest matter that was made available to form our solar system and our Earth," Caltech's Paul Dimotakis, a member of the Keck study team, told in February.

"We learned a lot about the moon by analyzing the moon rocks that Apollo astronauts brought back," he added. [NASA's 17 Apollo Moon Missions in Pictures]

Earth Causes Asteroid-Quakes
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Asteroid Basics: A Space Rock Quiz
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A challenging mission

Unmanned probes have successfully rendezvoused with asteroids in deep space multiple times. Japan's Hayabusa craft even snagged pieces of the near-Earth asteroid Itokawa in 2005, sending them back to our planet for study.


For example, the target asteroid will be spinning, which doesn't make for a smooth ride to lunar orbit. After the spacecraft captures the asteroid and brings it into a hold of sorts, the space rock will have to be de-spun, likely with thrusters, Dimotakis said.

"You might use reaction jets to take out most of it [the spin]," he said. "You would give you yourself a lot of time to do this, because there's no second chance in any of this."



"My guess is that all of these are not insurmountable challenges, and you would be able to calibrate yourself after you snagged it and adjust your controls," Dimotakis said.

Choosing a target


The Keck study recommends going after a carbonaceous asteroid packed full of water and other volatiles. Carbonaceous asteroids can be very dark, and it's tough to spot and characterize a 23-foot asteroid in the vast depths of space whatever its color.

So both Lewicki and Dimotakis stressed the importance of searching for potential asteroid targets sooner rather than later. Planetary Resources plans to begin launching a line of small prospecting space telescopes in 2014 or 2015, and these "Arkyd-100" craft could aid NASA's mission, Lewicki wrote.

Dimotakis, for his part, is engaged in a follow-up to the Keck study that's looking for potential targets in observations made by current telescopes.

"We are developing software in collaboration with JPL [NASA's Jet Propulsion Laboratory] that is going to exploit the observational digital record and essentially flag things that could be of interest and might be in this class," he said. "This has never happened before."

Still, mission scientists and engineers shouldn't just sit on their hands until an asteroid selection is made, he added.

It's important "to start developing the spacecraft before you even know where you're going," Dimotakis said. "If you do these things in parallel, then the mission timeline shrinks."
