Jason DavisNov 02, 2016

The flexible path to Mars: SLS, Orion and NASA’s Asteroid Redirect Mission

It takes just 25 minutes to drive from Bourbon Street in downtown New Orleans, Louisiana, out to NASA's Michoud Assembly Facility, which is wedged between Lake Ponchartrain and Lake Borgne. Here, in a 43-acre factory, the agency has been building rockets since the Apollo era.

I visited Michoud in September with two of my Planetary Society colleagues, where we met Steve Doering, the stages manager for NASA's new Space Launch System rocket. In a cavernous high bay called the Vertical Assembly Center, we stood before a 16-story welding tool that fuses together the rocket's giant, cylindrical fuel tanks.

Nestled within four, blue towers was the silver liquid hydrogen tank that will be used on the first flight of SLS in 2018. 

"We just finished the last weld on this tank last night," Doering said, as we stood gawking at the scene for a few moments. The tank measures 64.6 meters tall and 8.4 meters wide, yet it's just one piece of a vehicle that will tower 30 stories.

"It's going to be huge," Doering said. "It blows my mind every time I look at it—the sheer scale."

Finishing touches on a SLS hydrogen tank
Finishing touches on a SLS hydrogen tank Welders put the finishing touches on the inner side of an SLS hydrogen fuel tank. This particular tank is a qualification unit built for testing.Image: NASA / Michoud / Steve Seipel

Need to catch up on our Horizon Goal series?

Part 1: How The Columbia Tragedy Shifted NASA's Sights To The Moon
Part 2: 'Apollo on Steroids': The Rise and Fall of NASA's Constellation Moon Program
Part 3: Space in transition: How Obama's White House charted a new course for NASA
Part 4: To Mars, with a monster rocket: How politicians and engineers created NASA's Space Launch System

In part four of our Horizon Goal series, we learned how a messy tangle of politics and rocket science created SLS, the heavy lift rocket at the center of NASA's plans to send humans to an asteroid and Mars. In two years, it will blast the Orion crew capsule on a three-week shakedown cruise around the moon.

Since the end of the space shuttle program in 2011, a once-in-a-generation transformation has been sweeping through the agency's human spaceflight centers. How have the SLS and Orion programs fared? And what first steps is NASA taking as it prepares for the journey to Mars?


When SLS was announced back in 2011, Michoud's Vertical Assembly Center didn't exist. Instead, two, vertical cells—used to enclose space shuttle external fuel tanks while their rust-colored insulation was applied—stood where the giant SLS welding tool now stands.

By 2013, contractors had stripped the cells to their foundation, and a year later, the VAC was built and open for business. A tower misalignment problem briefly halted operations, but Boeing, which is building the SLS core stage, implemented a relatively quick fix. 

This metamorphic theme can be found throughout all of NASA's southern U.S. facilities, where infrastructure built for the shuttle and Constellation programs is being overhauled for SLS and Orion.

At Kennedy Space Center, a former shuttle stacking bay inside the iconic Vertical Assembly Building has been gutted and equipped with SLS access platforms. New fuel tank stress-testing stands dot the treeline at Marshall Space Flight Center in Huntsville, Alabama. And at Mississippi's Stennis Space Center, engineers are refurbishing a historic Saturn V test stand for an SLS core stage firing in late 2017. 

In addition to the physical transformation, a generational transition is also in progress.

Jackie Nesselroad is the director of manufacturing and assembly operations for Boeing at Michoud. She said the SLS program came online just in time to ensure that the current industrial workforce, which cut its teeth on the shuttle program, will be able to train the next crop of engineers.

"It's our responsibility to train and mentor the younger generation," she said. 

The knowledge transfer also works in the opposite direction.

"The kids of today have grown up with technology that I never had when I was in high school or in college," said Nesselroad. "They give us new breath—new energy and new ideas—to do things differently."

Insert rocket here
Insert rocket here New SLS work platforms line the inside of a former space shuttle bay in the Vehicle Assembly Building at NASA’s Kennedy Space Center. SLS will be stacked in the middle, and the platforms will slide together to enclose the rocket’s core stage and solid rocket boosters.Image: NASA / Bill White

At what cost?

When the Space Launch System was formally announced in September 2011, NASA said internal and external audits estimated it would take $18 billion to get SLS, Orion and the associated ground infrastructure ready for a test flight at the end of 2017. Adjusted for inflation, that number is $19.3 billion today.

An analysis of NASA budgets estimates that by October 2017, the program will have spent roughly $23.4 billion—a cost overrun of about 18 percent. The first flight, meanwhile, has slipped a year to late 2018, and the first crewed Orion flight could be delayed up to two years from 2021 to 2023.

A similar calculation in part two of our series pegged the Constellation program's cost overrun through 2009 at about 26 percent. Depending on your chosen timeline, Constellation was delayed between one and three years. That put its budget and schedule slips on par with the development of the space shuttle.

By those metrics, SLS and Orion are doing better than their predecessors—slightly.

But there are other signs the programs are healthy. NASA's human spaceflight division now uses a statistical model called the Joint Confidence Level, or JCL, to predict the likelihood a program will meet particular milestones based on funding expectations.

Under the JCL model—which is also used by the agency's science division—programs entering their final design and fabrication phases must formally commit to cost and schedule estimates that have a 70 percent chance of being correct. 

The SLS, Orion and ground systems programs all cleared those checkpoints in 2014 and 2015. Since then, there have been no major cost overruns or schedule slips.

Booster testing
Booster testing NASA and Orbital ATK test a Space Launch System solid rocket booster in mid-2016.Image: Jason Davis / The Planetary Society

Tough budgets

According to the U.S. Government Accountability Office, the bulk of a large space project's costs occur during the development phase, when testing and evaluation reveal unanticipated challenges.

Efficient programs, then, receive a budget bump up front that trails off over time as the project moves into operations.

Unlike some historic NASA programs like Apollo, SLS and Orion have not received significant funding increases during development. Their budgets are flat—a reference to what a line graph of time versus dollars spent looks like. 

Under those constraints, program managers are often forced to push non-critical development tasks—such as Orion's in-flight abort test—into the future. It's like paying off a large credit card debt over time, rather than all at once: short-term costs are lower, but overall costs and the time required to pay are higher.

Todd May, the current director of Marshall Space Flight Center and former SLS program manager, said that despite these challenges, SLS managed to complete a key milestone known as the critical design review in the same amount of time it typically takes a NASA science mission to reach the same milestone. 

In the case of SLS, this was less than four years.

"A spacecraft that might fit on a conference room table at one of the (NASA) centers versus something the size of that Statue of Liberty that has a gross liftoff mass of a million pounds—it's pretty amazing," he told me.

The flat budget also amplifies a problem familiar to many government programs: year-to-year funding uncertainties.

As we described in part four of our series, the White House proposes NASA's initial budget. Congress weighs in by passing bills that authorize programs and allocate funding. The President gets a final say by either signing or vetoing those bills.

Since the scuffle over NASA's human spaceflight program in 2010 and 2011, the White House and Congress have consistently disagreed on how much money SLS and Orion should get each year. 

The White House always asks for less money than Congress is willing to give, due to either differing priorities, a calculated political strategy, lingering resentment from 2010 and 2011, or some combination of all three. 

An analysis of those offsets shows that over five years, Congress has increased the SLS, Orion and ground systems budgets by about $3.2 billion.

Despite those increases, in the case of Orion, a recent Government Accountability Office report notes "the basic flatness" of the budget has not changed. Worse yet, budget battles now routinely drag into subsequent fiscal years. 

As a result, from 2012 through 2016, Orion received its funding between four and eight months late—a cumulative delay of 26 months. 

This can disrupt the programs' already precarious timelines, said the GAO.

"NASA and contractor staff have spent significant time developing contingency plans to ensure continuity of operations," the report said. "...in 2015 and 2016 management delayed some purchases and made multiple individual purchases rather than purchasing in bulk. Officials estimated these measures increased costs by 10 to 25 percent. For example, Program officials approved a year-long delay in purchasing a full set of valves for the life support system for EM-2 (the first crewed SLS-Orion flight) and delayed purchases related to the heat shield and propulsion thrusters for the mission to keep expenses within funding targets."

Orion at the moon
Orion at the moon An artist's rendering of the Orion spacecraft in lunar orbit.Image: NASA

First steps

As work on SLS and Orion ramped up, NASA also started strategizing how to fulfill President Obama's goal of visiting a near-Earth asteroid and Mars.

Those destinations were announced in a 2010 speech by the president that came as the administration fended off charges it had left the agency adrift after cancelling the return-to-the-moon Constellation program.

Sending humans to a near-Earth asteroid was mentioned in a 2009 presidential committee report exploring a "flexible path" to Mars, which laid out a variety of stepping-stone missions beyond Earth orbit.

But visiting a typical near-Earth asteroid is no trivial matter. Some studies indicate the round-trip journey could take up to 9 months, making it an ambitious mission that would require an add-on astronaut habitat, an upgraded SLS upper stage, and perhaps more importantly—practice.

Visiting a near-Earth asteroid in its native orbit, then, seemed like a big first step. Was it too big?

"Some people thought a near-Earth asteroid was the first step because it's near Earth and interplanetary," said Lou Friedman, the executive director emeritus of The Planetary Society. "But it turns out that even it was beyond the first step."

Sun propulsion

NASA also looked at key technologies needed to send heavy cargo to Mars ahead of humans, including food, water, shelters, landers, and ascent vehicles.

One possible solution is solar-electric propulsion. SEP engines convert sunlight into electricity, and use that electricity to strip electrons off an inert gas like xenon, creating ions. These ions are pushed out of a spacecraft, creating thrust.

SEP thrusters lack the quick punch of chemical rockets, but they can operate continuously for years at a time. In the long run, they can reach higher speeds, push heavier cargo and perform more difficult orbital maneuvers—providing you have the time to wait.

There's just one catch: A SEP engine powerful enough to push tons of cargo to Mars needs to be much more powerful than anything in use today. 

John Brophy was the project element manager for the SEP engine on Dawn, the NASA spacecraft that has used years of thruster burns to reach both Vesta and Ceres in the main asteroid belt. 

During a recent phone interview, Brophy told me Dawn's thruster input power is just two-and-a-half kilowatts—about two orders of magnitude less than what might be needed for Mars missions.

"You need a big, high-power electric propulsion system—something maybe on the order of 150 kilowatts to a few hundred kilowatts," he said.

In September 2011, the day before the design of SLS was revealed, NASA announced they had picked six companies to develop concepts for a 30-kilowatt SEP demonstration. This could serve as a stepping stone between Dawn's engine and Mars-class thrusters.

But an in-space demonstration has yet to occur. 

"Every time (NASA) did a cost estimate to demonstrate what they needed to demonstrate, they couldn't afford it," Brophy said.

Keck ARM concept
Keck ARM concept The original Asteroid Redirect Mission concept, as envisioned by the Keck Institute, uses a large capture bag to enclose a small asteroid. NASA has since opted for a claw mechanism that would pluck a small boulder off the surface of a larger asteroid.Image: Rick Sternbach / Keck Institute for Space Studies

One bird, two stepping stones?

NASA found itself with two stepping stones on its hands: the need for a midrange SEP demonstration, and a desire to get some deep-space practice before heading all the way to an asteroid.

What if—in a reversal of the old idiom—the agency could kill two stones with one bird? And knock off the president's asteroid goal while they were at it? 

Enter the Asteroid Redirect Mission—ARM.

NASA has formally studied the idea of capturing a small asteroid and bringing it back to lunar or Earth orbit since 2007, around the time John Brophy waved goodbye to Dawn as it launched on its mission to the asteroid belt.

In 2011, the Keck Institute for Space Studies, a Caltech think tank associated with NASA's Jet Propulsion Laboratory, funded a study to investigate the feasibility of retrieving an asteroid. The study was co-led by Brophy, Friedman, and Caltech's Fred Culick.

The final report, issued in April 2012, found that a 40-kilowatt SEP-powered spacecraft could capture a 500-ton asteroid and haul it back to lunar orbit. There, it could be visited by a crew of astronauts.

The concept caught NASA's attention. 

"We managed to get a presentation up to significantly high levels of NASA," Friedman said. "It hit at the right time, just at the point where SLS and Orion were looking for a mission for the astronauts."

In April 2013, when NASA released its next budget, it announced the formulation of the Asteroid Redirect Mission.

The rocky road

In a discussion with the press when ARM was announced, NASA CFO Elizabeth Robinson estimated the total cost of the mission's robotic portion would be less than $2.6 billion, a number derived by the agency's Glenn Research Center that was published in the Keck study.

Robinson also said the crewed portion of the mission could take place "perhaps as early as 2021"—meaning, on the first astronaut flight of Orion. 

To Robinson's credit, the cost of the robotic portion of the mission is currently pegged at $1.4 billion—up from an earlier estimate of $1.25 billion, but still much lower than the original Glenn prediction.

On the other hand, the crewed visit is now expected to occur no earlier than 2026.

Responses to the mission have been mixed. In a 2014 presentation to NASA's Small Bodies Assessment Group, MIT planetary scientist Richard Binzel argued the science benefits of ARM do not justify human risk. He also believes more intensive ground surveys could identify asteroids closer to Earth, such as 10-meter objects that whizz through cislunar space on a frequent basis. 

In 2015, the NASA Advisory Council suggested NASA test SEP technology without redirecting an asteroid, and claimed the science and planetary defense benefits did not outweigh the mission's cost.

Lamar Smith, a Texas congressional representative, has roundly criticized the mission during House hearings, calling the mission "uninspiring" earlier this year.

Asteroid scientists, however, have warmed up to the idea. NASA's Small Bodies Assessment Group recently worked with with the agency's human spaceflight division to maximize ARM's potential science return, and findings from a June 2016 meeting say the group "supports the plan as presented" to fly science payloads on the mission.

Friedman agreed, while also pointing to the benefits of the mission's timeline.

"Yes, bringing a 20-ton asteroidal boulder to lunar orbit will offer some terrific science opportunities, but more importantly it will enable human exploration on a celestial object and steps to Mars to be taken sooner than would be possible in any other way," he said.

ARM robotic mission concept
ARM robotic mission concept NASA’s revised Asteroid Redirect Mission concept envisioned a spacecraft grappling a small boulder from a larger asteroid.Image: NASA

The future

As we've seen throughout our series, presidential administrations can drastically alter NASA's trajectory—though not always as intended. Congress also gets a say, and no single directive unilaterally decides future space policies.

Less than one week from today, the United States will elect its next president. 

The new administration will have to decide whether to retain Mars as the agency's horizon goal, and if a near-Earth asteroid still fits into that plan. There are also a dizzying array of decisions to be made regarding commercial crew companies, the International Space Station, and how to lay out a more concrete roadmap for Mars.

In our sixth and final Horizon Goal installment, we'll try to make some sense of NASA's future, as the agency prepares to send humans beyond low-Earth orbit for the first time in a half-century.

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