http://www.space.com/13164-killer-asteroids-deflection-humanity-cooperation.html
http://www.wired.com/wiredscience/2011/10/asteroid-moving/
PASADENA, Calif. — The biggest obstacle in deflecting a killer asteroid away from Earth may be humanity's inability to get along.
We already have the technological know-how to prevent dangerous space rocks from barreling into our planet, provided we detect them in time. But this vital job would require a great deal of international cooperation, experts say, and history has shown that working together is not our species' strong suit.
"Somebody's got to make the decision to actually mount the deflection, and do it," said former astronaut Rusty Schweickart, chairman of the B612 Foundation, a group dedicated to predicting and preventing catastrophic asteroid impacts on Earth.
"That is not technical, but it's the toughest problem of all," Schweickart said here at the California Institute of Technology on Sept. 28, during a panel discussion called "Moving an Asteroid."Not if, but when
Our planet has always been pummeled by space rocks. A 6-mile (10-kilometer) asteroid slammed into Earth 65 million years ago, for example, wiping out the dinosaurs.
A potentially civilization-ending asteroid will bear down on Earth at some point, panelists stressed. It's a question of when, not if — and it could happen uncomfortably soon, they said.
Over the eons, asteroids big enough to cause serious damage today (not necessarily the extinction of our species, but disruptions to the global economy and civilizations around the world) have struck Earth every 200 to 300 years, Schweickart said. [5 Reasons to Care About Asteroids]
While the dinosaurs were helpless victims of this death from the sky, 21st-century humans don't have to be.
"What's cool is, we can do something about it," said panelist Bill Nye, executive director of the Planetary Society and former host of the science-themed TV show "Bill Nye the Science Guy."
Giving asteroids a push
Humanity has the technical skills to move asteroids in several different ways, panelists said. We can hurl a large body into them, for example, changing their orbit with one dramatic impact.
NASA did just that in 2005, sending a small probe careening into the comet Tempel 1 to determine the icy wanderer's composition. The goal in that case was science rather than planetary defense, but the key is that humanity knows how to do it with today's technology.
Asteroid deflection could also work in more subtle ways.
Scientists could sidle an unmanned spacecraft up next to a potentially dangerous asteroid, then let the duo cruise through space together for months or years. Over time, the probe's modest gravity would tug the asteroid into a different, more benign orbit, Schweickart said.
This so-called "gravity tractor" technique would allow for precise deflection, making it perhaps the most attractive option, provided we have enough lead time.
Scientists know how to do this, too. Various robotic missions have met up with asteroids over the years, with some even landing on or touching the space rocks. Japan's Hayabusa spacecraft even plucked some pieces off one in 2005, then sent the samples back to Earth for analysis.
If we didn't have very much warning time, and if the threatening space rock was too big to just knock around with an impactor, we could try to blast it apart with a nuclear missile. But this option should only be employed as a last resort, as it may end up doing more harm than good, panelists said.
"Momentum is conserved," Nye said. "If you blow it up, then the whole giant spray of rocks is coming at the Earth instead of one."
Global cooperation needed
A potential asteroid strike would represent a global problem that the world would most likely have to tackle together, Schweickart said.
Cost is one issue that would bring nations together, though likely not the main one. A deflection missionmight cost $500 million to $1 billion, Schweickart estimated. So it wouldn't exactly break the bank of the United States or another world power, but fairness would still seem to dictate that the costs be shared.
But many countries would want to be involved to make sure their own voices were being heard, and their own interests were being protected.
Say, for example, that an asteroid appeared to be headed for impact in the north Atlantic Ocean. Russia or China might push for a plan to nudge the asteroid to the west, away from them. The goal, of course, would still be to divert the asteroid away from Earth entirely — but Asia might be spared if the mission moved the asteroid a little, but not enough.
Conversely, the United States and Canada might want to move the asteroid in the other direction. [Natural Disasters: Top 10 U.S. Threats]
"That's why this geopolitical issue is very, very sticky," Schweickart said. "We've got to have agreement between nations."
Starting early
Such agreement might be tough to come by, especially since an effective deflection mission would have to be initiated early to have the best chance of success. We'd need lots of lead time, for example, to launch a gravity tractor spacecraft and give it time to tug on the asteroid.
In fact, we'd have to launch the mission before we were absolutely sure that the space rock in question was actually going to strike Earth, according to Schweickart.
"If you wait until you know, it's too late to act," he said.
Schweickart is pushing hard to raise awareness of the asteroid threat, and to convince people of the need to plan accordingly. He's afraid that the world will have a hard time pulling the trigger on a potentially civilization-saving mission.
"The likelihood is, we're going to end up with a big international debate until the day it hits," Schweickart said. "That's the most likely scenario."
The Plan to Bring an Asteroid to Earth
By Adam Mann
PASADENA, Calif. — Send a robot into space. Grab an asteroid. Bring it back to Earth orbit.
This may sound like a crazy plan, but it was discussed quite seriously last week by a group of scientists and engineers at the California Institute of Technology. The four-day workshop was dedicated to investigating the feasibility and requirements of capturing a near-Earth asteroid, bringing it closer to our planet and using it as a base for future manned spaceflight missions.
This is not something the scientists are imagining could be done some day off in the future. This is possible with the technology we have today and could be accomplished within a decade.
A robotic probe could anchor to an asteroid made mostly of nickel-iron with simple magnets or grab a rocky asteroid with a harpoon or specialized claws (see video below) and then push the asteroid usingsolar-electric propulsion. For asteroids too big for a robot to handle, a large spacecraft could fly near the object to act as a gravity tractor that deflects the asteroid’s trajectory, sending it toward Earth.
“Once you get over the initial reaction — ‘You want to do what?!’ — it actually starts to seem like a reasonable idea,” said engineer John Brophy from NASA’s Jet Propulsion Laboratory, who helped organize the workshop.
In fact, many of these ideas have been on the drawing board for years as part of NASA’s planetary defense program against large space-based objects that might threaten Earth. And there’s no shortage of potential targets. NASA estimates there are 19,500 asteroids at least 330 feet wide — large enough to detect with telescopes — within 28 million miles of Earth.
Though rearranging the heavens may seem an excessive undertaking, the mission has its merits. The Obama administration already plans to send astronauts to a near-Earth asteroid, a mission that would coop them up in a tiny capsule for three to six months, and involve all the risks of a long deep-space voyage. Instead, robots could shoulder some of that burden by bringing an asteroid close enough for astronauts to get there in just a month.
Parking an asteroid in a gravitationally neutral spot between the Earth and the sun, known as a Lagrange point, would provide a stationary base from which to launch missions further into space. There are several advantages to this. For one, launching materials from Earth requires a lot of power, fuel, and consequently money, to get out of our planet’s deep gravity well. Resources mined from an asteroid with very little gravitational pull could be easily shuttled around the solar system.
And many asteroids have a lot to offer. Some are full of metals such as iron, which can be used to build space-based habitats while others are up to one-quarter water, which would be either used for life-support or broken down into hydrogen and oxygen to make fuel. As well, asteroid regolith placed around a spaceship hull would shield it against radiation from deep space, allowing safer travel to other planets.
An asteroid could be an alternative to setting up camp on the moon, or complement a moon base with more resources for heading further out in the solar system, said engineer Louis Friedman, cofounder of the Planetary Society and another co-organizer of the Caltech workshop.
There’s also the potential for mining asteroid materials to bring back to Earth. Even a small asteroid contains roughly 30 times the amount of metals mined over all of human history, with an estimated worth of $70 trillion. And astronomers would have the chance to get a close-up look at one of the solar system’s earliest relics, generating important scientific data.
Though technically feasible, budging such a hefty target — with a mass in excess of a million tons — would not be easy.
“You’re moving the largest mother lode imaginable,” said former astronaut Rusty Schweickart, cofounder of the B612 Foundation, an organization dedicated to protecting Earth from asteroid strikes.
Most asteroids are irregular chunks of rock that spin chaotically along irregular axes. Engineers would need to be absolutely certain they could control such a potentially dangerous object. “It’s the opposite of planetary defense; if you do something wrong you have a Tunguska event,” said engineer Marco Tantardini from the Planetary Society, referring to the powerful 1908 explosion above a remote Russian region thought to have been caused by a meteoroid or comet. Of course, any asteroid brought back under the proposed plan would be too small to cause a repeat of such an event.
Still, these obstacles are like catnip to engineers, who love to go over every potential difficulty in order to solve it. Actually executing the asteroid retrieval plan would help demonstrate and greatly expand mankind’s space-based engineering capabilities, said Friedman. For instance, the mission would teach engineers how to capture an uncooperative target, which could be good practice for future planetary defense missions, he added.
And if the challenges for a large asteroid seem too daunting, researchers could always start with a smaller asteroid, perhaps six to 30 feet across. Gradually larger objects could be part of a campaign where engineers learn to deal with progressively greater complications.
Last year, Brophy helped conduct a study at JPL to look at the feasibility of bringing a 6.5-foot, 22,000-pound asteroid — of which there might conceivably be millions — to the International Space Station. This mission would help astronauts and engineers learn how to process asteroid materials and ores in space.
The JPL study suggested the asteroid could be captured robotically in something as simple as a large Kevlar bag and then flown to the space station or placed in a Lagrange point. Of course, such a small object might not have the same emotional impact as a larger destination. “NASA isn’t going to want to go to something that is smaller than our spaceships,” said engineer Dan Mazanek from NASA’s Langley Research Center.
No matter the size of the asteroid, these plans would require hefty investments. Even capturing a small asteroid would consume at least a billion dollars and anything larger would be a multi-billion-dollar endeavor. Convincing taxpayers to foot such a bill could be tricky.
Considering the resources available in any asteroid, private industry might be interested in getting involved. One possible mission would be to simply execute the first part of the plan — pushing the asteroid to near-Earth orbit — and then convene a commercial competition inviting anyone who wants to develop the capabilities to reach and mine the object.
Though the undertaking might be scientifically exciting, this wouldn’t be the primary motivation. An asteroid would provide great insight into the solar system’s formation, it’s not enough to justify the expense of bringing one to Earth. Any interesting science can be done much cheaper with an unmanned robotic spacecraft, said chemist Joseph A Nuth from NASA’s Goddard Spaceflight Center.
“Ultimately, we would be developing this target in order to help move out into the solar system,” Brophy said.
Though they did not reach a consensus on all the details, the group will reconvene in January to hammer out further specifications and potentially get the interest of NASA.
In the end, many agreed that bringing an asteroid back to Earth could create an interesting destination for repeated manned missions and that the undertaking would help build up experience for future jaunts into space.
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