Asteroid Redirect Mission



The Asteroid Redirect Mission (ARM), also known as the Asteroid Retrieval and Utilization (ARU) mission and the Asteroid Initiative, is a potential future space mission proposed by NASA. Still in the early stages of planning and development, the spacecraft would rendezvous with a large near-Earth asteroid and use robotic arms with anchoring grippers to retrieve a 6-meter boulder from the asteroid.

The spacecraft will characterize the asteroid and demonstrate at least one planetary defense technique before transporting the boulder to a stable lunar orbit, where it could be further analyzed both by robotic probes and by a future manned mission. If funded, the mission would be launched in December 2021, with the additional objectives to test a number of new capabilities needed for future human expeditions to deep space, including advanced ion thrusters.

Objective
The main objective is to develop the required technology to bring a small near-Earth asteroid into lunar orbit. There, it could be analyzed by the crew of the Orion EM-5 or EM-6 mission in 2026.

Additional objectives
Additional mission aims include demonstrating planetary defense techniques able to protect the Earth in the future - such as using robotic spacecraft to deflect potentially hazardous asteroids. Under consideration for deflecting an asteroid are: grabbing the asteroid and directly moving it, as well as employing gravity tractor techniques after collecting a boulder from its surface.

The mission would also test the performance of advanced solar electric propulsion (ion engines) and broad-band laser communication in space. These new technologies will help send the large amounts of cargo, habitats, and propellant to Mars in advance of a human mission to Mars.

Spacecraft overview


The vehicle would land on a large asteroid and grippers on the end of the robotic arms would grasp and secure a boulder from the surface of a large asteroid. The grippers will dig into the boulder and create a strong grip. An integrated drill will be used to provide final anchoring of the boulder to the capture mechanism. Once the boulder is secured, the legs will push off and provide an initial ascent without the use of thrusters.

Propulsion
The spacecraft would be propelled by advanced solar electric propulsion (SEP) (possibly a Hall effect thruster, see Ion thruster). Electricity will be provided by high efficiency ring-shaped solar panels (50 kW).

The advanced ion engine uses 10 times less propellant than equivalent chemical rockets, it can process three times the power of previous designs, and increase efficiency by 50%. It will use the Hall-effect, which provides low acceleration but can fire continuously for many years to thrust a large mass to high speed. Hall effect thrusters trap electrons in a magnetic field and use them to ionize the onboard xenon gas propellant. The magnetic field also generates an electric field that accelerates the charged ions creating an exhaust plume of plasma that pushes the spacecraft forward. The spacecraft concept would have a dry mass of 5.5 tons, and could store up to 13 tons of xenon propellant.

Each thruster will have a 30- to 50-kilowatt power level, and several thrusters can be combined to increase the power of an SEP spacecraft. This engine, which is scalable to 300 kilowatts and beyond, is being researched and developed by Northrop Grumman with Sandia National Laboratories and the University of Michigan. NASA Glenn Research Center is managing the project.

Proposed timeline
Originally planned for 2017, then 2020, the mission was recently pushed to December 2021 within a constant budget cap of $1.25 billion. The launch vehicle could be either a Delta IV Heavy, SLS or Falcon Heavy. The boulder should arrive in lunar orbit by late 2025. If the Asteroid Redirect Mission and the Space Launch System or an equivalent heavy launch vehicle are both completed on schedule, a manned mission to the asteroid brought to lunar orbit could be launched in late 2026.

Target asteroid
more than 1,600 new near-Earth asteroids have been discovered by various search teams and catalogued as potentially hazardous objects. NASA has yet to select a target for ARM, but for planning purposes it is currently using a near Earth asteroid named (341843) 2008 EV5 of about 400 m in diameter to pick up a single 4 m boulder from it. Other candidate parent asteroids are Itokawa, Bennu, and Ryugu. The decision on the target asteroid will be announced in 2019, allowing additional time to find alternative targets.

The carbonaceous boulder to be captured by NASA (maximum 6 meter diameter, 20 tons) is too small to harm the Earth because it would burn up in the atmosphere. Redirecting the asteroid mass to a distant retrograde orbit around the Moon will ensure it will not hit Earth and also leave it in a stable orbit for future studies.

History
The ARU mission, excluding any manned missions to an asteroid which it may enable, was the subject of a feasibility study in 2012 by the Keck Institute for Space Studies. The mission cost was estimated by the Glenn Research Center at about $2.6 billion, of which $105 million was funded in 2014 to mature the concept. NASA officials emphasized that ARM was intended as one step in the long-term plans for a human mission to Mars.

The two options studied to retrieve a small asteroid were Option A and Option B. Option A would deploy a large 50 ft capture bag capable of holding a small asteroid up to 8 m in diameter, and a mass of up to 500 tons. Option B, which was selected in March 2015, would have the vehicle land on a large asteroid and deploy robotic arms to lift up a boulder up to 4 m in diameter from the surface, transport it and place it into lunar orbit. This option was identified as more relevant to future rendezvous, autonomous docking, lander, sampler, planetary defense, mining, and spacecraft servicing technologies.

The crewed portion to retrieve asteroid samples from the Moon orbit (Orion EM-3) has been criticized as an unnecessary part of the mission, as thousands of meteorites have already been analyzed, and by claiming that the technology used to retrieve one boulder does not help develop a crewed mission to Mars. The plans were not changed despite the NASA Advisory Council suggested on 10 April 2015 that NASA should not carry out its plans for ARM, and should instead develop solar electric propulsion and use it to power a spacecraft on a round-trip flight to Mars.

In January 2016 contracts were awarded by NASA’s Jet Propulsion Laboratory (JPL) for design studies for a solar-electric-propulsion-based spacecraft for the agency's Asteroid Redirect Robotic Mission (ARRM). The robotic ARRM mission is the first phase of ARM. The contracts were won by Lockheed Martin Space Systems, Littleton, Colorado; Boeing Phantom Works, Huntington Beach, California; Orbital ATK, Dulles, Virginia; and Space Systems/Loral, Palo Alto, California.