NASA Homing in on Mission Design for Asteroid Relocation Excursion


HOUSTON — As NASA sifts through the results of the Orion deep-space capsule’s debut test flight, a parallel effort to develop a robotic asteroid relocation mission reaches a key decision point Dec. 16.

A team led by NASA Associate Administrator Robert Lightfoot will be briefed on the technical maturity, cost, risk, scientific appeal and other aspects of two ideas to relocate an asteroid into a high, retrograde lunar orbit, positioning it for a future Orion crew as well as for commercial entities and other countries interested in mining and exploration initiatives.

Plan A of the Asteroid Redirect Mission (ARM) entails capturing an asteroid small enough to fit inside a 15-by-12-meter inflatable bag. Once it is inside, the bag’s petals would close and an attached robotic spacecraft, outfitted with massive solar panels, would fire up its xenon ion engine. The asteroid’s path would be slightly diverted so that it would fly as close as about 100 kilometers from the Moon’s surface, picking up a gravitational bump to slingshot into a distant, stable retrograde lunar orbit.

Plan B would have the robotic spacecraft rendezvous with a larger asteroid, possibly hundreds of meters in diameter, and, after a preliminary scouting mission, land on its surface. A pair of robotic arms would deploy to pick up a 2- to 4-meter-wide boulder that would then be flown back toward the Moon and bounced out into a similar distant retrograde lunar orbit.

Both missions would take about three years.

“We trade efficiency for time,” Brian Muirhead, robotics manager at NASA’s Jet Propulsion Laboratory in Pasadena, California, told reporters at a Nov. 19 media day at the Johnson Space Center here.

“If we tried to do this mission with chemical propellants, we would need 20 times as much propellant,” he said.

Current mission designs include 10 tons of xenon for the spacecraft’s electric engine, compared with 200 tons of liquid oxygen and hydrogen. The ARM spacecraft is based on technology now being used by NASA’s Dawn probe, which is en route to its second destination in the asteroid belt, the dwarf planet Ceres. Dawn began its mission in 2007 with a half-ton of xenon.

NASA considers ARM primarily a technology demonstration mission for large, high-power solar arrays, such as what might be needed for future human missions to destinations beyond the international space station, which orbits about 418 kilometers above Earth.

A relocated asteroid also would serve as a target for a sample-return mission by astronauts on the first U.S. human excursions into deep space since the 1969-1972 Apollo program. That effort kicked off Dec. 5 with the debut test flight of NASA’s Orion capsule.

A third objective for ARM is to develop techniques that could be used to deflect a potentially hazardous asteroid. Overall, NASA is asking for about $1.25 billion for ARM, with Plan B running about $100 million more than Plan A. The mission could be launched on either a Delta 4 Heavy, which is what NASA used for the Dec. 4 Orion test flight, or NASA’s still-under-development Space Launch System rocket, which is expected to debut in November 2018.

ARM could launch as early as 2019 but more likely would not occur until 2020, Muirhead said. The asteroid would be expected to reach its cislunar orbit in 2023 or 2024 and possibly be a target for Orion’s Exploration Mission 2 flight.

So far, NASA has three targets if Plan A is selected and four for Plan B. Ground-based observatories worldwide are continuing the search. Technically, a decision would not have to be made until a year before launch, though the target could be identified in time for a mission review in 2016 or 2017.

Engineers have been testing prototypes for both Plan A and Plan B, with results to be presented to NASA headquarters in Washington for review Dec. 16. Scientists also will make their case for the value of returned samples for both mission designs and detail the benefits and shortfalls for planetary defense objectives. Also figuring into the decision about which path to pursue is how valuable the mission will be as a steppingstone to human expeditions to Mars, the ultimate goal of NASA’s human space program.