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ARM Option B at asteroid
A NASA illustration of Option B of the Asteroid Redirect Mission, with the ARM spacecraft on the surface of an asteroid to grab a boulder. (credit: NASA)

NASA rearms in its battle with mission skeptics

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Nearly two years ago, NASA announced plans for what is known today as the Asteroid Redirect Mission, or ARM. The concept, unveiled in the agency’s fiscal year 2014 budget request, called for sending a robotic mission to a near Earth asteroid and nudging it onto a trajectory to be captured into orbit around the Moon. Astronauts would then go to captured asteroid, collecting samples and demonstrating technologies NASA argued were critical for future human missions beyond Earth orbit.

As audacious as ARM sounded—shifting the orbit of an asteroid—the mission concept has struggled to win over skeptics in industry, the scientific community, an on Capitol Hill. They wondered exactly how such a mission was the logical next step on a long-term path towards Mars. Now, ARM has taken a somewhat different form, a change that, to many, is not particularly surprising. However, that change in ARM doesn’t appear likely to win over those critical of the mission concept.

Option B for boulder

NASA had planned to announce in December which of two options it planned to pursue for the robotic portion of ARM. One, known as Option A, was in essence the original ARM concept: send a spacecraft to an asteroid up to ten meters in diameter, grapple it (including, perhaps, wrapping it in a “bag”), and then redirecting it into lunar orbit. It was similar to a concept published in 2012 by Caltech’s Keck Institute for Space Studies.

“I’m going to have multiple targets when I get there. That’s what it boils down to,” Lightfoot said of Option B.

NASA, though, had also been looking at an alternative called, logically enough, Option B. Instead of moving an entire asteroid, Option B called for sending a spacecraft to a larger near Earth asteroid, perhaps several hundred meters across, whose surface is strewn with boulders. Once there, the spacecraft would land and grab a boulder up to four meters across for return to lunar orbit.

After a meeting at NASA Headquarters in mid-December, though, NASA announced it was delaying the decision (see “Deferred decision”, The Space Review, December 22, 2014). The rationale at the time was that the agency wanted more time to study the two options.

However, NASA associate administrator Robert Lightfoot, who has been leading the ARM effort, hinted then that Option B seemed like the better approach. “It’s the complexity associated with taking the boulder off the asteroid versus the technology development you get by doing that that is extensible,” he said December 17 when announcing the delay. If NASA could get more comfortable with that complexity as well its additional cost—Option B cost about $100 million more than Option A—the agency seemed open to selecting it.

That delay was, back in December, supposed to take just a few weeks, suggesting a decision would come in, say, mid-January. But January and February passed without an announcement. In early March, NASA administrator Charles Bolden, asked about the status of ARM, said a decision should be forthcoming in the next month. “We’re just looking through this, making sure we thought of everything,” he said.

That decision finally came last week. At a media teleconference held March 25 on just a few hours’ notice, Lightfoot announced that NASA has completed a mission concept review for ARM and was indeed proceeding with Option B.

Lightfoot indicated that the technologies offered by Option B, including the ability to land on the asteroid and grapple boulders, were more extensible for future exploration than Option A. “Those are the kinds of things we know we need when we go to another planetary body,” he said. “That was really important for me.”

He also indicated that another factor that supported Option B was a greater prospect of mission success. One challenge facing ARM was the limited number of target asteroids, particularly for Option A. Detecting asteroids that small is difficult, and ensuring that they are of suitable size and shape is also not easy. With Option A, NASA ran the risk of sending a robotic spacecraft to a target asteroid, only to find it was perhaps too big for the spacecraft to redirect.

With Option B, the potential targets are better understood. Spacecraft reconnaissance of asteroids in this size class suggests their surfaces are covered with small boulders, allowing spacecraft operators to choose the best asteroid—and to try another if their first choice is unsuitable for some reason. “I’m going to have multiple targets when I get there. That’s what it boils down to,” Lightfoot said.

Option B also allows for a test of a planetary defense technology called a “gravity tractor.” Once the spacecraft has grabbed the boulder and moved away from the larger asteroid, it will hold a position near the asteroid; its gravity will provide a very slight, but detectable, change in the asteroid’s orbit. That concept has been previously proposed as one way to deflect threatening asteroids without the need to use impactors or nuclear explosives.

Option B still costs about $100 million more than Option A, but Lightfoot added it fit within a cost cap of $1.25 billion, half the estimated cost of the original Keck study. That figure, though, does not include the cost of launching the robotic mission, nor the cost of the later crewed mission once the boulder is returned to a distant retrograde orbit around the Moon.

“There’s the cost of the mission and then there’s the price of the mission,” Lightfoot said. “If folks can come in as partners, it offsets the overall price that I have to pay from an agency perspective.”

For now, NASA is using as the notional target for ARM the asteroid 2008 EV5. That near Earth asteroid, about 400 meters in diameter, has not been visited by other spacecraft, but Lightfoot said he expected its surface to have a large number of suitable boulders based on observations of similarly-sized asteroids. This asteroid has been proposed as a target for other asteroid missions, including Japan’s Hayabusa 2 and Europe’s MarcoPolo-R.

Under NASA’s current schedule, the robotic ARM mission would launch in December 2020 and arrive at the asteroid about two years later. Lightfoot noted that NASA could wait until as late as 2019 to select a target for the mission if it decided not to go to 2008 EV5. Once at the asteroid, the spacecraft would spend from 200 to 400 days there, collecting the boulder and performing gravity tractor tests. The spacecraft and boulder would arrive in lunar orbit in late 2025.

NASA will develop more detailed cost and schedule estimates for the robotic ARM mission as part of work on “Phase A” of the project, which formally started with the completion of the mission concept review last week. Lightfoot said NASA will also carry out an acquisition strategy meeting in July to determine what parts of the mission the agency should develop in-house and which can be procured commercially.

ARM Option B returns
In this NASA illustration, the ARM spacecraft is returning to cislunar space carrying a boulder captured from the surface of a larger asteroid. (credit: NASA)

An alternative stepping-stone to Mars

At the media teleconference, Lightfoot indicated there was greater commercial interest in partnerships in Option B. “We felt like Option B offered us more of an opportunity to engage more folks” from the commercial sector, he said.

Option B, he later argued, also appeared to offer more opportunities for international partnership. Speaking at a symposium on asteroid research in Washington the day after the announcement, Lightfoot said there was strong interest from several countries, which he didn’t name, in participating in ARM in one manner or another.

“It’s our international partners participating with us on the International Space Station and some of our science missions,” he said at the symposium, held by the Universities Space Research Association and George Washington University’s Space Policy Institute. “They've offered to bring those kinds of talents to what we need to go do.”

That partnership, he said, could defray some of NASA’s costs. “There’s the cost of the mission and then there’s the price of the mission,” he said. “If folks can come in as partners, it offsets the overall price that I have to pay from an agency perspective.”

But while ARM Option B appeared to offer greater commercial and international roles, it hasn’t shown signs of swaying skeptics of the overall mission concept. “I don’t understand what a boulder does for us in terms of helping us get to Mars,” said MIT planetary sciences professor Richard Binzel at last week’s symposium.

“What does ARM, or what does picking a boulder up from the surface of an asteroid, have to do with placing an astronaut on the surface of Mars?” Binzel asked.

Binzel has previously been critical of ARM: at a meeting last summer of the Small Bodies Assessment Group, he called ARM to a “stunt,” likening it to something he illustrated with a slide for a fictional mission called the Far Away Robotic sandCastle Experiment (FARCE) (see “Feeling strongARMed”, The Space Review, August 4, 2014). At last week’s symposium, he was no more complimentary of ARM now that NASA selected a mission option.

“What does ARM, or what does picking a boulder up from the surface of an asteroid, have to do with placing an astronaut on the surface of Mars?” he asked. “If you’re dumbfounded, you’re not the only one.”

Binzel said he’s not opposed to having astronauts visit near Earth asteroids as one step towards going to Mars. “If we want to get to Mars someday, we have to be able to get out of the Earth-Moon system,” he said. Near Earth asteroids, he said, do serve as “stepping-stones” towards later missions to Mars.

However, he argued that it made more sense to send astronauts to near Earth asteroids in their “native” orbits, noting that astronomers had only catalogued a very small fraction of asteroids that could be accessed by human missions. “There are an abundance of natural objects accessible very nearly, but not as easily, as ARM,” he said. “Near Earth space is, in fact, very accessible, and it is not a giant leap from the Earth-Moon system to an asteroid.”

Binzel proposed that what NASA is currently spending on its overall asteroid initiative—about $220 million in its fiscal year 2016 budget proposal, including ARM itself and related activities—be refocused on the development of a space-based survey telescope to help discover more asteroids that could be potential targets for later human missions.

“A survey should be at the core of the asteroid initiative,” he said. A survey mission, he suggested, could be competed among various existing proposals in the public and private sectors, with a cost likely to be similar to NASA’s New Frontiers medium-class planetary missions, which have a cost cap of on the order of $1 billion.

Such a mission would not only detect potential targets for human exploration missions, but also help complete a Congressionally-mandated survey of potentially hazardous objects at least 140 meters across, as well as find objects that could be of interest to commercial interests. “Imagine of we had a catalog of the 100 or 1,000 most accessible near Earth asteroids,” he said. “It’s the gateway to in-space resource utilization.”

Binzel acknowledged that this approach would likely push back the date of a human asteroid mission into the 2030s. Others at the symposium, though, worried that not having a mission like ARM in place by the mid-2020s, around the time the International Space Station is likely to be retired, could harm human spaceflight in general.

“If NASA is not on its way to human spaceflight in deep space by the mid-2020s, and you can say ARM enables that to happen,” said former astronaut Tom Jones, “then you have stretched out the advance of NASA astronauts, human spaceflight, into deep space by such a long period that what I fear is people will lose interest in that.”

“You’ll wind up shutting things down to the point where people will get used to the fact that all we have is a space station near the end of its life and nothing more ambitious,” he warned, “because Mars will still be too far a stretch.”

“If you’re going to spend $1.25 billion plus launch vehicle costs to do something,” said Squyres, “and you get the most important things by not going after the rock, don’t go after the rock.”

However, Binzel argued that deferring a human asteroid mission doesn’t mean that NASA can’t do other human missions in cislunar space, including testing some of the technologies planned for ARM. For example, he said NASA could use solar electric propulsion—one of the major technologies NASA said ARM will demonstrate—to place a cargo spacecraft into lunar orbit to be later visited by astronauts.

NASA officials have also dropped hints in recent months that ARM could still be considered a success even if the spacecraft doesn’t redirect an asteroid into lunar orbit by demonstrating those technologies. That has led others, including those on the agency’s own advisory team, to suggest NASA not do ARM at all.

“If you’re going to spend $1.25 billion plus launch vehicle costs to do something,” said Steven Squyres, chairman of the NASA Advisory Council, at a meeting of the council in January, “and you get the most important things by not going after the rock, don’t go after the rock.”

Bolden, discussing ARM with the council at that January meeting, was put on the defensive by comments like those. “Give me a break,” he said. “We’re trying to do a lot of different things and satisfy a lot of people who want us to do a lot of different things, and we thought we found a way that would get a lot of these previously disconnected things put together.”

It does not appear, though, that Bolden or the rest of the agency will get much of a break from critics, on Capitol Hill and elsewhere, simply by choosing one option for the robotic part of ARM. The agency will still have to justify how ARM, on whatever form, makes the most sense as NASA’s next step in human spaceflight on the long journey to Mars.