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SLS core stage
The core stage of the first SLS at Michoud Assembly Facility after the installation in early November of its four RS-25 engines. (credit: NASA/Jude Guidry)

Seeking a bigger role for a big rocket

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Earlier this month, NASA announced the newest milestone in the development of its long-awaited (and long-delayed) Space Launch System. At the Michoud Assembly Facility in New Orleans, workers completed installation of the four RS-25 engines into the rocket’s core stage. With those engines in place, the core stage will soon be ready for shipment to the nearby Stennis Space Center for testing, including a “Green Run” test around the middle of next year where those four engines will fire for eight minutes, just as they will on an SLS launch.

“If NASA focuses on the investment in the ongoing SLS with the EUS, Orion, and ground system developments, there is a better chance of making an earlier date,” Cooke said.

The SLS has been a key part of NASA’s exploration plans since the language in the 2010 NASA authorization act that directed the agency to develop it. While the plans themselves have changed, the agency has maintained that the SLS will nonetheless be essential for human spaceflight beyond Earth orbit, despite cost and schedule issues that have pushed back its first launch to at least late 2020, and more likely 2021. NASA has held firm despite criticisms that it would be better off adopting commercial alternatives, such as (but certainly not limited to) SpaceX.

Recently, though, NASA is getting criticism from the opposite direction. Some members of Congress have suggested that NASA isn’t using SLS enough: that is, NASA is relying too much on those commercial options in its current exploration architecture, when the SLS, particularly its Block 1B variant with the more powerful Exploration Upper Stage (EUS), could handle it with fewer launches.

That criticism, interestingly, is coming from members of the administration’s own party in Congress. “Every space exploration study conducted over the last 40 years indicated that the most optimal architectures for exploring the Moon and Mars require a heavy-lift launch vehicle similar to SLS,” said Rep. Brian Babin (R-TX), ranking member of the House Science Committee’s space subcommittee, during a hearing last week on NASA’s exploration plans.

He raised that point in criticism of NASA’s Human Landing System (HLS) procurement, which sought proposals for commercially developed lunar landers that NASA could use to land humans on the Moon. Those landers would be launched, as NASA originally envisioned, on commercial vehicles (the final version did allow companies to propose launching them on the SLS, provided they worked with NASA and its contractors to get a cost estimate for a cargo version of the SLS.)

“While I share the frustration and delays to the SLS program, switching horses midstream is not a wise move at this point,” he continued.

He and others at the hearing questioned NASA’s approach that, in their view, minimizes the use of the SLS to launching Orion spacecraft. Under NASA’s current architecture, elements of the lunar Gateway would be launched commercially, as well as logistics spacecraft to support the Gateway. The lunar landers would also use commercial launches (save for those that did propose using SLS): as many as three launches per lander, one each for the ascent module, descent module, and transfer stage that would move the lander from the Gateway to low lunar orbit.

That is, for some, way too many launches. “The fewer launches and critical operations per mission, the higher the probability of mission success,” said Doug Cooke, a former NASA associate administrator for exploration and now an industry consultant, during a September hearing by the same House subcommittee. (Cooke’s clients include Boeing, prime contractor for the SLS core stage, although many in the space community note he held similar views long before working with Boeing.)

“If you don’t have a big booster, you’re not going to make it,” Stafford said of returning to the Moon.

“SLS is not being used for what it was designed to do, other than carry Orion,” he continued. “If NASA focuses on the investment in the ongoing SLS with the EUS, Orion, and ground system developments, there is a better chance of making an earlier date.” He said a lunar landing could be achieved with two SLS missions, one carrying Orion and the other an integrated lander, with the two rendezvousing in lunar orbit—no Gateway required.

At last week’s hearing, the two invited witnesses, former astronaut Tom Stafford and retired aerospace executive Tom Young, backed up that assessment. Rep. Frank Lucas (R-OK), the ranking member of the full committee, asked them about the effect of multiple launches on commercial vehicles on mission safety.

“The mission I did accomplished the whole thing with one launch,” Stafford, a member of the Apollo 10 crew, responded. He then referred to Cooke’s earlier testimony that concluded there was only a 50 percent chance of mission success with the current multiple-launch approach. “I cannot disagree with it.”

“But with eight launches, I’ll have to go with Mr. Cooke: your probability of success goes down to about 50 percent,” he concluded.

“Oh my,” Lucas responded with a sigh.

Stafford, earlier in the hearing, was adamant about the importance of a heavy-lift launch vehicle. “If you don’t have a big booster, you’re not going to make it,” he said. “You have to have a big shroud, which leads you to a big, wide-diameter booster. If you don’t have it, you’re not going to make it.”

Young, in his testimony, didn’t specifically address the use of SLS versus commercial rockets, but did criticize what he called “experiments” in procurement. “Managing and contracting experiments must be excluded from the Mars-Moon program,” he said. Asked later for an example of such an experiment, he brought up the HLS program.

“A management experiment in my view would be to buy seats for crews to fly to the surface of the Moon,” he said. “I personally think that these should be government-acquired assets under the leadership and direction of NASA.”

He also said that NASA should drop some of its programs related to human spaceflight. “The plate is really full today,” he said. “I personally think that the leadership is going to have to, number one, prioritize, but number two is probably to eliminate some of the things that are currently being done that will interrupt having any opportunity of 2024, or I would say even 2028.”

One thing Young would push off NASA’s plate is the Gateway. “I do not really see a required role for the Gateway in the lunar program,” he said, although it could later support preparations for human missions to Mars. “There’s not a compelling argument to me for the Gateway for the lunar program.”

Bridenstine expects to produce three SLS rockets through 2024. “Adding an additional SLS into the mix could—I’m not confident that could happen.”

Last week’s hearing, though, was not the first time that Republican members of Congress questioned NASA’s use—or unwillingness to use—the SLS. At a hearing last month of the House appropriations subcommittee that funds NASA, Rep. Robert Aderholt (R-AL), ranking member of the subcommittee, pushed for greater use of SLS.

“I understand there is a growing confidence among the prime contractors for SLS to be able to produce two rockets a year starting in 2024,” he said, including the first Block 1B. “What do you think?”

“It depends on what Boeing is willing to invest, quite frankly,” responded NASA administrator Jim Bridenstine, noting that there wasn’t funding to support that increased production rate, even if it is possible.

“We haven’t seen the performance yet that would indicate that we’re guaranteed the second core we’d need for a Moon landing in 2024,” added Ken Bowersox, the acting associate administrator for human exploration and operations at NASA and the other witness at the hearing.

At current rates, Bridenstine said, there will be three SLS rockets produced by 2024: one for the uncrewed Artemis 1 test flight, the second for the first crewed Orion flight, Artemis 2 in 2022, and then the Artemis 3 mission in 2024 that would take astronauts to the lunar Gateway, and from there to the surface of the Moon. “Adding an additional SLS into the mix could—I’m not confident that could happen.”

Aderholt returned to the issue later in the hearing. “What commercial launch vehicles exist today or that are in development that can or will be able to launch the HLS and get to the Moon to accomplish the goal of US boots on the Moon by 2024?”

Bridenstine responded that SLS is the only vehicle for launching humans. But for the landers, he and Bowersox listed several, including the Falcon Heavy and Starship from SpaceX, Vulcan from United Launch Alliance, New Glenn from Blue Origin, and Northrop Grumman’s OmegA.

“There could be an SLS-derived commercial solution,” Bridenstine added. “We’re not shutting the door on that opportunity. Of course, that would require some investment from Boeing to achieve.”

“What is the contingency if, for some reason, those commercial rockets are not available by 2024,” Aderholt asked. Bridenstine noted that the Falcon Heavy is, in fact, in service today, unlike the other commercial vehicles—or SLS.

“But if commercial’s not available, what’s the contingency plan?” Aderholt asked again.

“I think, Mr. Ranking Member, that would put us in a position to make landing in 2024 very, very difficult,” Bridenstine said. “If we don’t have the additional rockets, then we’re not going to be able to achieve the goal. Btu we’re confident we’ll have those rockets.”

“If this forces NASA to reassess its schedule for returning to the Moon, it would provide an opportunity to ensure that they are developing the ideal architecture that maximizes mission success and minimizes risk,” Babin said of potential spending shortfalls for Artemis.

Aderholt then turned to the issue of using larger numbers of smaller rockets, citing Cooke’s past testimony and a separate op-ed. Bridenstine acknowledged that more launches raised the risk of mission failure, but that the overall architecture needs to be assessed before concluding an approach with more launches was riskier than one with fewer launches.

“We’re not specifying to any of the commercial providers for the Human Landing System how their systems ought to be developed,” Bridenstine said. “We’re waiting to have them tell us what their approach is, and then we’ll assess their approaches.”

Boeing is one of the companies bidding on the HLS program, and confirmed that its approach makes use of the SLS. In a statement released November 5, the day the proposals were due to NASA, it said it submitted a proposal that would involve the launch of an integrated lander on an SLS Block 1B.

“Using the lift capability of NASA’s Space Launch System Block 1B, we have developed a ‘Fewest Steps to the Moon’ approach that minimizes mission complexity, while offering the safest and most direct path to the lunar surface,” Jim Chilton, senior vice president for space and launch at Boeing Defense, Space, and Security, said in that statement.

The only other entity to confirm it has bid on HLS is the “national team” led by Blue Origin that includes Draper, Lockheed Martin, and Northrop Grumman. The companies have not disclosed how many of Blue Origin’s New Glenn vehicles would be needed to launch the three-element lunar lander. (SpaceX is widely believed to have submitted a proposal based on its Starship vehicle, but the company has declined to publicly confirm that.)

NASA’s plans, though, depend on getting sufficient funding. Neither the House nor the Senate have provided all the money NASA requested in its $1.6 billion budget amendment in May that the agency says is essential to keeping Artemis on track. At that October appropriations hearing, Rep. José Serrano (D-NY), chairman of the subcommittee, was skeptical it would be forthcoming without more information about the overall cost of the Artemis program that NASA has yet to disclose.

“It’s hard to justify any extra spending on this effort in the current fiscal year when we don’t know the costs down the road,” Serrano said. He suggested pushing back the date of a human return to the Moon to 2028, the goal prior to this March, “in order to have a successful, safe and cost-effective mission for the benefit of the American people and the world.”

Babin referred to those comments at last week’s hearing, concluding that the odds of getting full funding for Artemis in fiscal year 2020 were ”dwindling.”

“If this forces NASA to reassess its schedule for returning to the Moon, it would provide an opportunity to ensure that they are developing the ideal architecture that maximizes mission success and minimizes risk,” he said. “This could be done by developing landers that leverage the investments already made by the taxpayers in national capabilities like SLS and Orion.”

Others, though, might argue that any reassessment of NASA’s architecture for returning humans to the Moon promoted by a funding shortfall should also include revisiting SLS and Orion themselves.

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