NASA officials today said they have picked the specific asteroid mission and offered new details for that mission which could launch in the 2020 timeframe.
Specifically, NASA’s associate administrator Robert Lightfoot said the Asteroid Redirect Mission (ARM) will rendezvous with the target asteroid, land a robotic spacecraft on the surface, grab a 4 meter or so sized boulder and begin a six-year journey to redirect the boulder into orbit around the moon for exploration by astronauts.
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There had been a discussion about grabbing an entire asteroid and bringing it back to Lunar orbit but that proved to be more complicated and costly – about $100 million more than the boulder-grabbing scheme, Lightfoot said.
Lightfoot said NASA has so far identified three valid asteroid candidates for the mission: Itokawa, Bennu and 2008 EV5, though it is focusing on the 2008EV 5 asteroid for now. Lightfoot said EV5 has a number of attractive qualities, namely it not been visited by other spacecraft missions, it has been extensively observed, its orbit is well known and it is a carbonaceous asteroid – the most common type of asteroid and contains a number of elements scientists are interested in studying up close.
Lightfoot said though that the space agency doesn’t need to select an asteroid to land on till a year before launch. The agency expects to identify one or two additional candidates each year leading up to the mission.
While the asteroid grabbing part of the work will garner the most attention, the ARM mission will try to demonstrate a few other major technologies.
First NASA expects the ARM spacecraft to be powered by Solar Electric Propulsion (SEP), a system that converts sunlight to electrical power through solar arrays and then uses the resulting power to propel charged atoms to move a spacecraft.
NASA says this propulsion system can move massive cargo very efficiently. While slower than conventional chemical rocket propulsion, SEP-powered spacecraft require significantly less propellant and fewer launches to support human exploration missions, which could reduce costs.
The idea is that future SEP-powered spacecraft could pre-position cargo or vehicles for future human missions into deep space.
The Arm spacecraft will also test planetary defense techniques to help mitigate potential asteroid impact threats in the future.
“Once Arm leaves the surface of the asteroid it will go into a halo orbit around asteroid. The idea is that such an orbit can influence the movement of the larger asteroid by doing that,” Lightfoot said. “ We are trying to demonstrate that we can influence a very large mass with a very small mass.”
NASA describes this technique as a “gravity tractor.” From NASA: “All mass exerts and experiences gravity and, in space, the gravitational attraction even between masses of modest size can significantly affect their motion. This means that by rendezvousing with the asteroid and holding a halo orbit in the appropriate direction, the ARM robotic spacecraft can slowly pull the asteroid without touching it. The effectiveness of this maneuver is increased, moreover, if mass is moved from the asteroid to the spacecraft by the capture of a boulder.”
The mission also depends on the successful development and deployment of the Orion spacecraft and the agency’s Space Launch System rocket, which would be carrying astronauts on the part of the mission that would meet up ARM and explore the asteroid mass. The current concept for the human crewed component of ARM is a two-astronaut, 24-25 day mission, NASA said.
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