Asteroid Redirect Mission

Objectives

The main objective of the Asteroid Redirect Mission is to develop deep space exploration capabilities needed in preparation for a human mission to Mars and other Solar System destinations per NASA's Journey to Mars flexible pathways.

Mars precursor

Space tug missions, to disaggregate non-time-critical Mars logistics from crew, can reduce the costs by as much as 60% (if using advanced solar electric propulsion (ion engines)) and reduces overall mission risk by enabling on-site check-out of critical systems before the crew departs

Not only will the solar electric propulsion (SEP) technologies and designs be applied to future missions, but the ARRM spacecraft will be left in a stable orbit for reuse. The project has baselined any of multiple refueling capabilities; the asteroid-specific payload is at one end of the bus, for possible removal and replacement via future servicing, or as a separable spacecraft, leaving a qualified space tug in cislunar space.

Expanded and sustainable deep space operations

The robotic and crewed missions will demonstrate capabilities past Earth orbit, yet within a few days' return contingency. Lunar Distant Retrograde Orbit (DRO), encompassing Earth-Moon L1 and L2, is essentially a node for Earth system escape and capture. This is moreso if an Exploration Augmentation Module (EAM) is brought for extended human stays, possibly by an ARRM-like SEP module. On its return leg from Mars, a human mission may save tons of mass by capturing into DRO, and transferring to a parked Orion for Earth return and reentry.

Additional objectives

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

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 to increase mass ("enhanced gravity tractor").

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 and/or Phobos.

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 UltraFlex-style 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.

Even at a destination, the SEP system can be configured to provide power to maintain the systems or prevent propellant boil-off before the crew arrives. However, existing flight-qualified solar-electric propulsion is at levels of 1-5 kW. A Mars cargo mission would require ~100 kW, and a crewed flight ~150-300 kW.

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 crewed mission to the asteroid brought to lunar orbit could be launched in late 2026.

Target asteroid

As of January 2016 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 (1,300 ft) in diameter to pick up a single 4 m (13 ft) 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

NASA Administrator Robert Frosch testified to Congress on "asteroid retrieval to Earth" in July 1980. However, he stated that it was infeasible at the time.

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 15-metre (50 ft) capture bag capable of holding a small asteroid up to 8 m (26 ft) 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 (13 ft) 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 with claims that thousands of meteorites have already been analyzed and 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.

In May 2016, ASI (the Italian Space Agency) agreed to a joint study, and possible Italian participation.