Since Aug. 17, NASA’s massive Space Launch System (SLS) moon rocket has stood silent on pad 39B at the Kennedy Space Center, towering over the Florida swamps. By any measure it’s a beautiful machine; by any measure it’s a promising machine; and by any measure it’s been a troubled machine—especially over the past two weeks. On Aug. 29 and again on Sept. 3, the rocket’s six engines were supposed to light, generating a record 8.8 million lbs. (4 millionkg) thrust to lift the hardware stack off of the pad. Had things gone according to NASA’s plans, the SLS’s Orion crew capsule would be in the early stages of a mission to the moon by now. The space agency’s Artemis program, which aims to have American astronauts back on the lunar surface by 2026, would have officially kicked off.
But that hasn’t happened yet. Both of the planned launches were cancelled. The first was called off after being plagued by a handful of problems—the worst of them a faulty sensor that falsely indicated that one of the main engines had failed to be cooled sufficiently for ignition. Lack of adequate cooling might have caused the engine bell to crack or even shut down. A liquid hydrogen leak prevented rocket fuelling properly. This caused the second stoppage. Engineers have now fixed the fuel leak issue on the launch platform. However, the rocket will need to be rolled back to the Vehicle Assembly Building hangar in order to replenish the batteries which were depleted during the lengthy wait and to check for any other leakages. The launch will be delayed until at least October.
“We’ll go when it’s ready. We don’t go until then,” said NASA Administrator Bill Nelson in a statement to the press after the second stand-down. “This is part of our space program: Be ready for the scrubs.”
The SLS is ambitious and hugely successful, despite all the disappointments. Until now, the Apollo program’s Saturn 5 held the record for the most powerful rocket ever launched. They produced 7.75 million lb when the five engines were ignited Nov. 9, 1967. The thrust of the engines produced 7.5 million lb (3.49 million kilograms) and rattled the television press boxes. Plaster dust also flung from the roof of the launch control centre. In the five years that followed, nine Saturn 5s carried astronaut crews to the Moon.
SLS is bigger than it should be. It takes all that propellant power to lift the crew capsule and other payloads for the return-to the-moon program. The mission will send astronauts out to the Moon for just a few days, but it will be used later to launch permanent crews. Camping out on a celestial body that’s only three days from home is seen as an essential first step to learning how to live off the extraterrestrial land—a critical rehearsal for later journeys to Mars which, at minimum, is an eight-month trip each way.
“The SLS is the start of a generational effort to return us to deep space and keep us there,” says John Honeycutt, NASA’s SLS program manager. “It has got tremendous capability.”
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The SLS has a rich history, and it faces a difficult future. This was even before the recent problems with its launch. It has taken 18 years to get a new moon rocket built, at a cost so far of $23 billion just from 2012 to 2022 and a per-launch price tag of $4.1 billion, according to a 2021 report by NASA’s Office of the Inspector General. “Relying on such an expensive, single-use rocket system will, in our judgment, inhibit if not derail NASA’s ability to sustain its long-term human exploration goals to the moon and Mars,” Inspector General Paul Martin told told Congress in March.
That warning is especially persuasive in an era in which the private sector is competing with NASA to bring down per-launch costs and, regarding SpaceX, safely land and reuse boosters, rather than simply throwing them away after a single use—as was done with the Saturn 5 and remains the case with the SLS.
“The architecture we’ve chosen doesn’t allow for reusability,” says Jim Free, NASA’s associate administrator for exploration systems. “Disposing of it is the best way to go, and that’s what we’ve chosen.”
The SLS, despite its shortcomings, is still a remarkable and huge machine and NASA’s bet on the future of human space exploration. The first flight—whenever it happens—will help determine if that bet will pay off.
The Long and Strange Journey
SLS’s roots can be traced back to January 14, 2004 when President George W. Bush declared that the entire space shuttle fleet would be retiring. NASA plans to replace the space shuttle fleet with a new heavy lift rocket and crew capsule that can be used for mission to Mars, as well as missions to the Moon.
Skeptics dismissed the move as little more than a bit of election-year candy, designed to appeal to NASA-heavy constituencies in Texas, Bush’s home state, and Florida, the swingiest of swing states, which gave Bush the presidency by a razor-thin margin in the 2000 election. Bush knew business was in order and funds began to flow for Ares V moon rocket. It would have plans to send astronauts back on board the moon by 2015.
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The Ares V will not be designed entirely from scratch, as was the Saturn 5, but it would at least partially use components from the off-the-shelf. Its core stage—the backbone, and largest section, of the rocket—would be powered by six RS-68 engines—the same engines used by the private-sector Delta IV rocket. Two solid rocket boosters from NASA would sit atop the core stage. The rocket’s second stage—which sits atop the first—would be a newly designed, upgraded version of the Saturn 5’s second stage. The Orion capsule, which is Apollo-like in appearance, would be able to travel the remainder of its journey into space. It will then reach the moon. Bush proposed to pay for the entire program, which was called Constellation, by reallocating $11 billion from NASA’s cumulative five-year budget of $86 billion—a bargain, as space hardware goes.
But things didn’t work out that way. By the time the Bush Administration left office in 2009, the Constellation program was grossly over budget and behind schedule—with a Government Accountability Office report that year revealing that a return to the moon, and a follow-on mission to Mars, would, by NASA’s own estimates, cost $230 billion by 2025. Constellation was canceled by President Barack Obama.
Congress was resolute. In the summer of 2010, Nelson was a Democratic senator from Florida, and chairman of the Senate’s space subcommittee. With less than 24 hours left before Congress’ August recess, the Senate had unanimously approved authorization for a massive new rocket that would replace Ares V, keeping NASA’s dream of deep-space travel alive and, not incidentally, providing a wealth of jobs for the engineers and other workers who would build the new machine. It was up to Nelson to convince Steny Hoyer—then, as now, Democratic Majority Leader of the House of Representatives—to pass the bill in the House.
Nelson recalls that Hoyer wasn’t too pleased with the arm-twisting by the upper chamber of Congress at the very last minute. “He was cussing at me,” Nelson recalls. “He told me, ‘I don’t like it that the Senate always makes the House take your position at the last minute. I don’t have time to take it up.’” Hoyer nonetheless agreed to try, and not long before midnight, the rocket passed the House easily, with over three-quarters of the chamber’s members voting aye.
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SLS was the official name for the heavy-lift rocket. This is to indicate practicality and the promise that prices would drop. Obama was under pressure from both Capitol Hill and the private sector, which, like Nelson, was mindful of the jobs the SLS and Orion would provide, and so he went along—on the condition that costs would come down.
The SLS had to be completely redesigned. First, it was decided to eliminate the second stage. In its place would go a proven—and existing—upper stage already used by the Delta IV, to be purchased from private manufacturer United Launch Alliance. It would also eliminate the six core engines. NASA will instead use engines already in place: The same engines NASA used for the launch of the spacecraft. After the destruction of the shuttles, NASA found that the engines in stock were just gathering dust.
“There were 18 main shuttle engines already in the pipeline,” says Free. “So using them saves money.” The shuttle-derived solid rockets flanking the core stage would be retained from the Ares V, contributing to the muscle the shuttle’s main engines would provide, and rounding out the rocket’s overall 8.8 million lb. of thrust.
To the Moon
The mission that NASA hopes to fly in October—dubbed Artemis 1—will be a 42-day affair that will see the Orion spacecraft make two wide loops around the moon, before returning home and splashing down in the Pacific Ocean off the coast of San Diego. NASA plans to launch Artemis 2 in 2024. It will consist of four astronauts flying a shorter circumlunar mission covering 4,600 miles. (7,400 km) beyond the far side of the moon—though not going into lunar orbit—and then returning home. Artemis 3 will be the next lunar landing under the Artemis program in 2025, 2026.
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In order for astronauts to set foot on the moon, they need not just an SLS to get them into space and an Orion spacecraft to put them in lunar orbit, but also what NASA calls a Human Landing System (HLS)—a spacecraft like the Apollo lunar module, capable of descending to the moon’s surface. In April 2021, NASA selected SpaceX to provide the HLS in the form of the company’s Starship spacecraft, a 164-ft. (47 m) stainless steel craft that will be launched aboard SpaceX’s new Super Heavy booster. Starship will uncrewed fly to the Moon, meeting the Orion crew. One of four crewmembers from Starship will fly the HLS to the moon, and the two remaining remain aboard Orion in lunar orbit. They will stay on the surface for 6 and 1/2 days. The moon walkers will then return to Orion’s orbit and rendezvous once more with Orion. In a fixed orbit around the sun, the Starship that was abandoned will be destroyed.
That’s the plan, at least, but thus far, a crew-rated Starship spacecraft has not even been built, much less tested in space. Nelson professes to have few concerns, pointing to SpaceX’s multiple crew launches to the International Space Station, as well as the 173 successful launches of its workhorse Falcon 9 rocket, serving both the government and the private sector.
“Look at the success of SpaceX,” Nelson says. “[The company]NASA has set milestones for the entire team. … They’ve had phenomenal success.”
Even if SpaceX does prove capable of delivering the goods, there’s still the matter of money—despite the supposed cost-cutting redesign. Here too, Nelson is sanguine, insisting that as NASA ultimately launches what it hopes to be one SLS per year, the price will be slashed “dramatically,” as he puts it—though he does not cite a dollar figure.
The lion’s share of the savings Nelson cites should come from the simple fact that research and development costs will no longer be included in the overall price tag; with that design and testing work complete, the rockets could be built faster, too. What’s more, NASA is already in discussions with prime contractors Boeing and Northrop Grumman for moon missions extending as far as Artemis 9, with an option to extend that deal to Artemis 14. It could be cheaper to build and fly in bulk, which can also reduce costs.
However, not all passengers are on board. “This reminds me of the arguments that were made at the beginning of the shuttle era, that with repeated launches the cost would come down. That never happened,” says John Logsdon, professor emeritus and founder of the George Washington University Space Policy Institute. He does agree that economies of scale can lower future launch costs. “It makes sense that the cost will come down,” he says, “but it may not be by very much.”
Pricey or not, the SLS is NASA’s ride of choice for this decade and beyond. And the space agency will have more disposable cash come 2030, when the Space Station is deorbited—freeing up the $4 billion per year it costs the U.S. to operate and maintain it. NASA should be able to fulfill its long-term Mars and near-term plans much more easily. Half a century ago, America is committed to making humans a multiworld species. That journey is being started by the SLS, which we are looking forward to.
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