NASA Asteroid Mission May Test Earth Defense Too
In this concept image, the robotic vehicle descends to the surface of a large asteroid to collect a boulder that it can redirect to a distant retrograde lunar orbit.
On April 10, 2013, the White House and NASA released details of the US space agency's budget for the 2014 fiscal year. Included in the budget was a request for over $100 million to begin work on the Asteroid Retrieval and Utilization Mission. The mission would see a robotic spacecraft rendezvous with a small asteroid, which would then steer the space rock to the Earth-moon libration point (EML2) -- a region of gravitational stability beyond the far side of the moon. A manned mission would then meet the "tamed" asteroid to carry out science in-situ. It has been determined that such a mission would optimize the scientific gains while reducing risk and cost. On Wednesday, NASA released an animation detailing the stages of asteroid capture, here are the highlights.
Although its exact configuration has yet to be established, the robotic asteroid capture spacecraft will likely be solar powered and be propelled by an advanced ion drive. Optimistic estimates put a 2017 launch window on the first phase of the mission.
When approaching the asteroid, the spacecraft will jettison the hatch covering the folded asteroid "capture bag." According to the Keck Institute study that the mission is based on, the asteroid will be approximately 7 meters wide and have a mass of 550 tons.
The capture bag will expand like an accordion's bellows in preparation for asteroid capture.
The spacecraft will likely carry out an automated docking maneuver with the asteroid. Seen here, a laser is emitted by the spacecraft, guiding it in.
When fully expanded, and centered, the capture bag will envelop the space rock.
A draw-string-like mechanism will allow the capture bag's opening to be closed around the asteroid, securely mating spacecraft with asteroid.
Once secured, the spacecraft will "de-spin" the asteroid and begin steering it toward the Earth-moon system. This will mark the first time in human history that we have ever changed the trajectory of a natural object in space.
Meanwhile, preparations will be underway for a manned expedition to the captured asteroid. Seen here, NASA's future Space Launch System (SLS) rocket blasts off.
NASA's Orion space capsule will take a team of astronauts to the asteroid's parking orbit at EML2.
The Orion capsule will perform a docking maneuver with the robotic asteroid capture spacecraft after several days transit.
With the asteroid secure, astronauts will have the freedom (and time) to carry out extensive studies during extravehicular activity (EVA).
With the science done and samples collected, the Orion capsule returns to Earth.
The entire mission will culminate in the spashdown of the Orion capsule with astronauts on board. The asteroid will remain parked at EML2 for further study by followup missions to the lunar farside. You can watch the whole video on the NASA website:http://www.nasa.gov/multimedia/videogallery/index.html?media_id=161659311
NASA's bold plan to park an asteroid near the moon may also test out a new way to protect Earth from dangerous space rocks.
Last year, the agency announced that it intends to tow a near-Earth asteroid into a stable lunar orbit, where it could be visited repeatedly by astronauts for research and exploration purposes. NASA officials are still ironing out the details of the mission, which may bag up an entire small space rock or snag a boulder off the surface of a large asteroid.
If NASA decides to go with the boulder option, the asteroid-capture mission will also include a planetary-defense demonstration, providing the first in-space test of a so-called "enhanced gravity tractor," officials said. [Images: NASA's Asteroid-Capture Mission]
Given enough lead time, asteroids on a collision course with Earth can be safely deflected using a handful of methods. One of these is the gravity tractor technique, in which a robotic probe flies alongside a space rock for months or years, gradually nudging it off course via a slight gravitational tug.
The greater the shepherding probe's mass, the stronger its gravitational pull is. And poaching a boulder off a potentially hazardous asteroid would allow a deflection mission to increase its mass significantly without having to pay any additional launch costs.
"We'd go into this enhanced gravity tractor position after we retrieve the boulder and demonstrate that we have even more gravity attraction capability by doing that," Lindley Johnson, program executive for NASA's Near-Earth Object (NEO) observations program, told reporters in March.
NASA has identified about a dozen promising candidates for the asteroid-capture mission, Johnson added — six or so for each of the two options. The best target for the boulder-grab mission may be Itokawa, a 1,750-foot-long (530 meters) space rock that was visited by Japan's Hayabusa probe in 2005.
The space agency wants astronauts to visit the redirected asteroid by 2025, to meet an exploration deadline set by the White House. In 2010, President Barack Obama directed NASA to get people to a near-Earth asteroid by 2025 and then on to the vicinity of Mars by the mid-2030s.
The asteroid-capture mission remains in a "preformulation" phase at the moment, as NASA is still gathering data and sorting through ideas. The space agency hopes to have a basic mission concept in place by around the end of the year, officials have said.
In addition to the gravity tractor method, incoming space rocks could also be knocked off course with a direct hit by a "kinetic impactor," researchers say. (These techniques could also be combined in two coordinated space missions, slamming an asteroid with an impactor probe and then sending a gravity tractor out to finish the job.)
More extreme measures might be necessary for extremely large asteroids and space rocks detected with little warning time. In such cases, a nuclear bomb might be humanity's best — and perhaps only — option.
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