NASA's revised plans to send astronauts back to the moon are quickly taking shape.

On Feb. 27, NASA Administrator Jared Isaacman revealed a new vision for the Artemis program, and the missions the agency hopes will establish a long-term human presence on the lunar surface. The shuffle includes updated mission goals for Artemis 3 and beyond, a shorter cadence between launches of the Space Launch System (SLS) rocket, and an SLS redesign that is now coming into focus.

Under the previous program architecture, the SLS "Block 1" variant, which used the Interim Cryogenic Propulsion Stage (ICPS) as its upper stage, would launch Artemis 1 through Artemis 3, while Artemis 4 and beyond would fly with SLS Block 1B and Block 2, which featured the more powerful Exploration Upper Stage (EUS). Now, however, NASA is scrapping those upgrades for a "standardized" SLS configuration.

At the time of the Feb. 27 announcement, NASA did not indicate what the standardized SLS version would look like, or what its vision was for the SLS upper stage. But a concurrent image release illustrating the new Artemis framework showed the program's Orion crew capsule flying on a vehicle that was unmistakably neither the ICPS or EUS.

Instead, Orion and its service module were pictured burning under the power of what appears to be a Centaur V — the upper stage for United Launch Alliance's (ULA) new Vulcan rocket.

This fueled speculation at the time, which was confirmed on March 6, when the government's System for Award Management (SAM.gov) website listed the "Vulcan Centaur V Upper Stage for Space Launch System" contract opportunity.

The opportunity originated from NASA's Marshall Space Flight Center in Alabama, and was described as "a sole source contract" for ULA to supply "next-generation upper stages for use in Space Launch System (SLS) Artemis IV and Artemis V."

"No Other Supplies or Services Will Satisfy Agency Requirements due to the highly specialized nature of this requirement," agency officials added in the SAM.gov posting.

Centaur V has a proven flight record on Vulcan, which debuted in 2024 and has four successful launches under its belt (with a notable few issues, unrelated to Centaur). Its predecessors, Centaurs III and IV, flew using the same RL10 engine and relied on much of the same technology built into Centaur V to fulfill nearly 170 launches aboard ULA's Delta IV and Atlas rockets.

Additionally, a variant similar to Centaur, the Delta Cryogenic Second Stage, supported Orion on the spacecraft's Exploration Flight Test-1 in December 2014, when a ULA Delta Heavy launched the capsule into space for the first time. That mission sent an uncrewed Orion to Earth orbit and back.

Centaur V is powered by two RL10 engines and is the largest, most advanced of the ULA Centaur line. It holds about twice as much fuel as the ICPS and is nearly the same diameter as Orion and its service module.

"ULA’s Centaur (with minor modifications) is the only existing in-space propulsion stage capable of meeting the SLS upper stage design parameters and performance characteristics, while also meeting NASA’s schedule," NASA said in a submitted document justifying awarding the contract to ULA without competition.

That schedule was also part of the shift in Artemis' architecture. Artemis 2, which is on track for a possible launch attempt as early as April 1, remains unchanged. Each mission after that, however, has been repurposed and accelerated.

Artemis 2 will launch a crew of four astronauts on a 10-day mission to fly a single loop around the moon and back to Earth. Artemis 3 was originally designed as the program's first lunar landing, targeted for 2028, but has been transformed into a 2027 test flight with Orion and one or more Artemis lunar landers in low Earth orbit. (Both SpaceX's Starship and Blue Origin's Blue Moon landers were selected under Artemis' Human Landing Services contract, and NASA has indicated that Artemis 3 will utilize either or both, depending on their readiness.)

Artemis 4 is now the first mission in the lineup with the objective of landing astronauts on the lunar surface, which NASA still hopes to accomplish in 2028, with a follow-up landing on Artemis 5 potentially occurring that same year.

With the Artemis 2 SLS stacked and nearly ready for launch, and the Artemis 3 SLS already outfitted to accommodate ICPS, Artemis 4 and 5 are only the two missions confirmed to launch Orion with the standardized SLS configuration and Centaur V upper stage, according to NASA's contract specifications. which don't mention any missions beyond Artemis 5.

What will carry Orion to orbit beyond Artemis 5 may be mere speculation at this point. The SLS has experienced numerous delays and cost overruns during its long development, spurring criticism from many who view its continued funding as more of a jobs program fueled by the U.S. Senate than as a sustainable space program. And some in the space industry are asking about the viability of SpaceX's Super Heavy booster — the first stage of the Starship megarocket, which remains in development — to support Orion launches, or possibly even Starship stepping in as Artemis' crew transport vehicle for Artemis 6 and beyond.

NASA Administrator Jared Isaacman recently announced a significant restructuring of the Artemis program, and how the agency intends to return astronauts to the moon.

The new plan shortens the time between missions and redraws the map of which launches will achieve various program milestones. Nothing will change for Artemis 2, which may lift off in a matter of weeks, carrying four astronauts on a 10-day flight around the moon and back to Earth. Every mission after Artemis 2, however, has been adjusted.

The programmatic shuffle is rendering parts of the old Artemis plan obsolete, leaving major ground hardware half-built and an uncertain future for the Gateway moon-orbiting space station under development.

Isaacman announced the changes during a press conference on Feb. 27, citing unacceptable wait times between missions for Artemis' Space Launch System (SLS) rocket and an increased risk of relying on unproven technologies to carry out mission-critical objectives like landing astronauts safely on the lunar surface.

The Artemis 2 SLS is currently undergoing repairs in the Vehicle Assembly Building (VAB) at NASA's Kennedy Space Center in Florida, with a potential rollback to its launch pad in time for a launch window that opens April 1. Artemis 2 will bethe first crewed flight of the Orion spacecraft and the first return of astronauts to lunar space in more than half a century. Under the previous framework, it was meant to be followed by Artemis 3 in 2028, which would carry out the program's first moon landing with astronauts aboard SpaceX's Starship vehicle.

For Artemis 4, NASA planned to upgrade to the SLS Block 1B, which features a design powerful enough to launch elements of the Gateway space station intended for lunar orbit. Beginning with Artemis 4, NASA aimed to use the Gateway outpost around the moon for deep-space science and as an orbital layover stop where Orion and the program's lunar lander could dock to transfer crews headed down to the surface. Gateway, however, is nowhere to be found in any of NASA's recent Artemis updates.

Under NASA's new plan, there will be no SLS Block 1B. In the hope of shortening launch cadences from the current 3.5-year interval to the desired 10 months, SLS is being standardized into a single configuration. Instead of relying on SLS' current Interim Cryogenic Propulsion upper stage, NASA is reportedly considering converting United Launch Alliance's Centaur V upper stage for use on SLS for all Artemis launches after Artemis 3.

The revised Artemis program is now targeting 2027 for the launch of Artemis 3, but instead of landing on the moon, the mission will fly to low Earth orbit for rendezvous and docking maneuvers with either or both of the Artemis program's contracted moon landers — SpaceX's Starship and Blue Origin's Blue Moon spacecraft — depending on their relative readiness for orbital missions.

NASA partnered with SpaceX for Starship to serve as the lander for Artemis 3 and 4 and contracted Blue Moon for Artemis 5. But the agency is now signaling that it's ready to fly Artemis 3 with whichever lander can be made safely available when launch time rolls around.

With Artemis 3 turned into a lunar landing stepping stone around Earth, Artemis 4 has been tapped as the program's first crewed landing on the moon, which NASA still hopes to accomplish in 2028, with a possible second moon landing that same year on Artemis 5.

It's a major reshaping of Artemis' original mission progression, but the plan has been purposed to maximize both crew safety and NASA's chances of success, according to Isaacman. The shakeup doesn't come without some sacrifice, though.

Gateway's fate remains undetermined under NASA's new plan. Many components of Gateway are already in various states of assembly, but there is now no rocket to launch some of them once they're ready and no missions yet assigned to rendezvous with the proposed outpost. Congress advanced a revised NASA authorization bill on Wednesday (March 4) that supports many of Isaacman's proposed changes to the Artemis program, but only requires he brief lawmakers on Gateway's status within a few months' of the bill's passing.

If Gateway is on the chopping block, as seems likely, there is potential for its existing hardware to be repurposed for use in a possible base on the lunar surface, which has been a longstanding component of the Artemis program's goals and NASA's vision for a sustained human presence on the moon. One of the revisions in the authorization bill even grants the NASA administrator the freedom to "repurpose, reprogram, reconfigure, or reassign existing programs, platforms, modules, or hardware originally developed for other programs" in order to ensure that the space agency's Artemis goals are successful.

Canceling future SLS upgrades also has implications for some of Artemis' ground infrastructure, which is being built to support the larger rocket variant. To transfer the 322-foot-tall (98 meters) SLS Block 1 from the VAB to its launch pad, NASA uses the huge Crawler-Transporter 2 vehicle to traverse the distance with the rocket standing on its mobile launch platform (MLP). The MLP contains the SLS launch tower, which helps secure the rocket in place and provides the umbilicals that help fuel SLS before liftoff.

Previous block upgrades to SLS were substantial enough to require a separate MLP (Mobile Launcher 2) be built, rather than upgrading the existing platform. But in an update on March 3, NASA confirmed that "the agency is no longer planning to use the Exploration Upper Stage or Mobile Launcher 2."

The contract for Mobile Launcher 2 was awarded in 2019, and has cost about $1.6 billion to date, about 98% of which has already been paid. Seven years later, the Mobile Launcher 2 is currently nearing completion outside the VAB, but it now may never realize its originally intended purpose. And relying on a single MLP to support Artemis launches less than a year apart could cause a schedule jam. The SLS MLP required refurbishment from damage caused after the Artemis 1 launch in November 2022.

Preparing the existing mobile launcher for an Artemis 4 flight with a new Centaur V-based upper stage could take a year or more, because the work would go beyond normal post-launch refurbishment. Engineers would have to reconfigure upper-stage umbilicals, fluid and electrical interfaces, and control systems, then complete testing to certify the update for launching SLS.

Potentially losing Gateway, or having to halt construction and/or repurpose the hardware from Mobile Launcher 2, isn't necessarily a total loss for NASA or the Artemis program, though. The agency has a long history of repurposing or evolving massive hardware for use on new or revised missions. Elements from both could be utilized to support Artemis or other future missions as NASA's plans continue to evolve.

NASA has revealed a huge shakeup to its Artemis program of crewed moon exploration.

The announcement came last week, just after the agency's Artemis 2 rocket was rolled back to the hangar for repairs. What was expected as an update to the timeline for Artemis 2's mission ended up being an explanation of the restructuring of the Artemis program itself.

The plan for Artemis 2 remains the same: Launch a crew of four astronauts on a 10-day journey around the moon and back to Earth aboard NASA's Orion spacecraft. With maintenance already underway, NASA is hoping the repairs to the Artemis 2 rocket can be made in time to meet a launch window that opens April 1. Until now, the mission had been billed as the precursor to an actual landing on the lunar surface on Artemis 3 in 2028, but that is no longer the case. NASA hasn't changed its goal of returning astronauts to the moon in 2028, but Artemis 3 won't be the mission to carry it out.

Instead, that task will fall to Artemis 4, with Artemis 3 launching sooner with a different mission framework, and with a potential second crewed lunar landing on Artemis 5 in late 2028. The approach mirrors that of NASA's early Apollo program, which launched incremental, quick-succession missions to test and prove the technologies necessary to safely land astronauts on the moon.

"We didn't go right to Apollo 11," said NASA Administrator Jared Isaacman during a Feb. 27 press conference. "We had a whole Mercury program, Gemini [and] lots of Apollo missions before we ultimately landed."

In contrast, Artemis' architecture previously outlined a jump from Orion's first uncrewed mission to the moon in 2022, a crewed lunar flyby on the upcoming Artemis 2 mission and a moon landing on Artemis 3 in 2028. But three or more years between missions, and a leap from lunar space to the lunar surface without at least one test-run with Orion and its landing vehicle left too many "firsts" for Artemis 3 to take on and posed a significant safety risk, according to a recent report from the NASA Aerospace Safety Advisory Panel (ASAP).

"The numerous and unprecedented mission objectives — many being attempted for the first time within a single flight — result in a compounded level of technical and safety risk," the ASAP report said.

Indeed, under its original design, the success of Artemis 3 depended on a lot of things going right. The mission's moon lander, SpaceX's Starship spacecraft, is expected to need more than a dozen refueling flights in Earth orbit in order to complete its objectives of rendezvousing and docking with Orion in orbit around the moon, landing astronauts on the lunar surface and launching them back to orbit to rendezvous and dock again with Orion, which will safely ferry the astronauts home.

Artemis 3's success was not only dependent on all of those things going exactly right for the first time, but also on a number of operational milestones SpaceX has yet to demonstrate during Starship's ongoing development. One such milestone is the ability to transfer and store large amounts of cryogenic propellant in space, which has never been done before.

Now, NASA is breaking up those objectives between multiple missions. Artemis 3 will now launch in 2027, and will rendezvous with one or both of NASA's contracted moon landers in Earth orbit. In addition to Starship, NASA has also tapped the Blue Moon lander from Blue Origin to support the Artemis program, and the space agency is eager to test out Orion with Starship, Blue Moon or both on next year's Artemis 3 flight.

"It's challenging, it's ambitious, but with this course correction, we are on a more stable foundation, and a more realistic path to the mountains we have ahead," NASA Associate Administrator Amit Kshatriya said on Friday (Feb. 27).

In the same way that Artemis 2 parallels the objectives of Apollo 8 to test out the crew capsule's flight systems around the moon, Artemis 3's mission to demonstrate rendezvous and docking with the lunar landers in Earth orbit, as well as testing out new spacesuits, is now closely aligned with Apollo 9.

NASA also wants to shorten the cadence between Artemis launches. Apollo 8 launched on Dec. 21, 1968, and was followed less than three months later by Apollo 9 — a much quicker turnaround than Artemis' current wait time of three-plus years.

To do this, NASA is backing away from some of the more complex design upgrades intended for Aretmis' rocket, the Space Launch System (SLS). SLS Block 1 was designed with the Interim Cryogenic Propulsion Stage (ICPS) to launch the first three Artemis missions. Artemis 4 and the missions to follow were supposed to employ more powerful SLS variants — Block 1B, Block 2 and so forth — which feature an enhanced Exploration Upper Stage to launch heavier elements of the program, such as components for the Gateway space station planned for lunar orbit.

Now, NASA is planning a more standardized SLS, with an upper stage solidified for its design rather than customized for each Artemis mission, and a new NASA graphic paints a picture of what that and other plans for Artemis' future might look like.

An image released in concert with last week's Artemis announcement illustrates NASA's new vision for the program and humanity's return to the moon, and has some details that may bring clarity to how that vision will unfold.

The newly unveiled image is divided into three frames: Artemis 2, Artemis 3 and Artemis 4 and beyond. The Artemis 2 panel contains no surprises; it shows Orion's launch on SLS, lunar flyby and return to Earth. Artemis 3 shows the mission's new plan, with Orion still flying with ICPS, docking with both Starship and Blue Moon above Earth.

The image's bottom panel — Artemis 4 and beyond — is the most interesting. It shows the standardized SLS Block 1 configuration launching alongside SpaceX's Starship rocket and Blue Origin's New Glenn. Orion is then seen flying next to both landers in space, still attached to its SLS upper stage, which is notably not the ICPS.

Instead, the spacecraft appears to be powered by a dual-engine Centaur vehicle, which is the upper stage for United Launch Alliance's (ULA) Vulcan rocket. While NASA has not yet confirmed that it plans to outfit Centaur for SLS and Orion, doing so could make a lot of sense. The stage is nearly equal in diameter to Orion and its service module, has been proven reliable on all of ULA's Vulcan missions to date, and doesn't need to be designed from scratch to support the needs of future Artemis launches.

Other significant inclusions in NASA's illustration are seen on the lunar surface. Next to a handful of Starship and Blue Moon landers stands a robotic Intuitive Machines lander — notably, the first commercial lander to touch down on the moon, which it did as a part of NASA's Commercial Lunar Payload Services (CLPS) program in early 2024.

Moon rovers bearing a striking resemblance to Astrolab's FLEX lunar excursion vehicle are also seen scattered around the modules of a lunar base. Astrolab's rover design is one of three in the running for Artemis, along with rovers from Intuitive Machines and Lunar Outpost, neither of which appears to be included in NASA's graphic.

NASA is hoping its Artemis restructuring will accelerate its readiness for a 2028 crewed lunar landing, while also breaking its missions down into more manageable milestones. It's an ambitious undertaking for an increased launch cadence by the space agency, which has run into repeated delays over the course of the last 10 or so years leading up the program's first crewed flight.

Some experts aren't sure the space agency can pull off the new plan in such a short amount of time, but still see the reorganization as a step in the right direction. As Lori Garver, NASA's deputy administrator from 2009 to 2013, said in an online post, "We didn't 'wait' 3.5 yrs between launches because we wanted to, that is what it took. The new plan increases the probability that the next US moon landing attempt will be successful — even though it is still likely more years away than we hope."

Her post received a response directly from Isaacman, who agreed that "after decades, America’s return to the moon has to be more than just talk."

"I would describe launching SLS every 10 months as extremely difficult," Isaacman wrote, "which is supposed to be our specialty at NASA."

NASA's Artemis 3 mission will no longer land astronauts on the moon — and it might not involve SpaceX's Starship megarocket, either.

On Friday (Feb. 27), the space agency announced that it's revamping the architecture of its Artemis program of lunar exploration. One of the biggest changes involves Artemis 3, which was originally supposed to land astronauts on the moon using Starship's upper stage.

NASA's new plan launches Artemis 3 in 2027 but keeps it in low Earth orbit. The mission will aim to demonstrate a range of technologies and capabilities there, including a rendezvous and docking procedure between the Orion crew capsule and "one or both commercial landers from SpaceX and Blue Origin," agency officials said in a statement on Friday.

Blue Origin, which was founded by Amazon's Jeff Bezos, is developing a crewed lander called Blue Moon. That vehicle was supposed to carry NASA astronauts for the first time on Artemis 5, a lunar landing mission previously targeted for 2030.

But NASA has mused about pressing Blue Moon into service sooner than that. Last October, for example, then-Acting Administrator Sean Duffy announced that he planned to open the Artemis 3 landing contract to competition, explaining that he wasn't satisfied with the pace of Starship's development. (Starship has flown 11 test flights to date, and the most recent two were fully successful. However, the vehicle has yet to reach Earth orbit.)

Blue Origin was the only realistic competitor for that moon-landing gig. And it would appear the company remains in the running for the mission in its revised form, given the wording of Friday's announcement.

"Otherwise, they could have simply said in this statement today that they're going to dock the Orion with the Starship lunar lander and do their testing," Don Platt, head of the Department of Aerospace, Physics and Space Sciences at the Florida Institute of Technology, told Space.com on Friday. "But they didn't. They didn't say that."

Pace of development isn't the only factor going into this decision, according to Platt, who also leads the university's Spaceport Education Center.

"NASA does not want to have to rely on only one one contractor, either," he said. "I think that's why they're really kind of pushing this competition between Blue Origin and SpaceX."

Blue Origin appears to be leaning into the competition. In late January, the company announced that it's pausing its suborbital space tourism flights for at least two years "to further accelerate development of the company's human lunar capabilities."

"The decision reflects Blue Origin's commitment to the nation's goal of returning to the moon and establishing a permanent, sustained lunar presence," the company said in a statement at the time.

The revised Artemis architecture now envisions the first crewed lunar landing since the Apollo era to take place on Artemis 4 in 2028, with a possible second touchdown occurring that same year, on Artemis 5.

The new plans are part of a broader shift, which prioritizes a step-by-step approach and an increased launch cadence. (It's been more than three years since the first — and so far only — Artemis mission lifted off; NASA is gearing up to launch the Artemis 2 crewed mission around the moon in a month or so.)

For example, NASA officials said on Friday that they want to keep flying Artemis' Space Launch System rocket in a configuration as close to the current "Block I" as possible. Previously, Artemis 4 had been slated to use the "Block IB" variant, which would have featured a new, more capable upper stage.

The ultimate goal of Artemis is to establish a permanent, sustainable human presence on and around the moon in the next five to 10 years. NASA also wants to land the first Artemis astronauts before China puts boots on the moon, which the nation aims to do by 2030.

"With credible competition from our greatest geopolitical adversary increasing by the day, we need to move faster, eliminate delays and achieve our objectives," NASA Administrator Jared Isaacman said in Friday's statement.

"Standardizing vehicle configuration, increasing flight rate and progressing through objectives in a logical, phased approach, is how we achieved the near-impossible in 1969, and it is how we will do it again," he added.

NASA's plan to return humans to the moon has changed.

As engineers work to fix issues with the Artemis 2 mission's Space Launch System (SLS) rocket, NASA officials are reexamining what flights will follow and are shaking up plans for which of those will actually land astronauts on the moon.

In short, Artemis 3 is changing from a crewed mission to the lunar surface to an Earth-orbit rendezvous of NASA's Orion spacecraft with one or more of the program's moon landers in 2027, NASA Administrator Jared Isaacman announced on Friday (Feb. 27). The program's first moon landing will now take place on Artemis 4, in 2028, with a potential second landing that same year with Artemis 5.

In addition, SLS' design will be standardized to streamline production, and the rocket's launch cadence will be shortened from once every three years to once every10 months, if all goes to plan. To accomplish this, NASA plans to bolster its workforce in order to "rebuild core competencies," Isaacman said, "that will directly contribute to NASA's launch cadence."

It's a major shift in the architecture of NASA's Artemis program, which aims to establish a sustained human presence on the moon and in lunar orbit. A recent report from NASA's Aerospace Safety Advisory Panel (ASAP), however, cast serious doubts on the previous architecture, calling into question the agency's timeline, projected mission safety and the readiness of the Human Landing System (HLS) vehicles that NASA has contracted from private companies to perform lunar landings.

As originally designed, Artemis 3 encompassed a long list of technological firsts, with a heavy dependency on HLS, which the ASAP determined posed "significant risks at the mission level."

"This is just not the right pathway forward," Isaacman said. "Going right to the moon … is not a pathway to success."

"We want to reduce complexity to the greatest extent possible," he added. "We want to accelerate manufacturing, pull in the hardware and increase launch rate, which obviously has a direct safety consideration to it as well."

With the new framework, Artemis 3 is drastically simplified, and less dependent on the readiness of a moon lander's ability to actually land on the moon. The development of both private HLS landers chosen by NASA has fallen short of the space agency's hopeful timeline, resulting in impending delays.

NASA contracted SpaceX's Starship to land astronauts on the Artemis 3 and Artemis 4 moon missions. Starship has flown 11 suborbital test flights over the past three years but has yet to notch several critical milestones needed to qualify the spacecraft for lunar landings with astronauts onboard.

NASA picked Blue Origin's Blue Moon spacecraft, meanwhile, to land astronauts on the Artemis 5 moon mission. A Blue Moon pathfinder known as Mark 1 is currently undergoing testing at NASA's Johnson Space Center in Houston.

Before NASA will let either Starship or Blue Moon carry astronauts to the lunar surface, the vehicles will have to demonstrate their ability to transfer and store cryogenic fuels in space, rendezvous and dock with Orion, as well as execute an uncrewed moon landing and successful ascent back to lunar orbit.

Now, NASA plans to use Artemis 3 as a safe proving ground for those procedures in low Earth orbit before entrusting the landers to be 100% successful on their first flights to the moon.

Previous architecture for Artemis 4 used an upgraded version of SLS, called Block 1B, which featured the enhanced Exploration Upper Stage in place of SLS' current Interim Cryogenic Propulsion Stage (ICPS). If NASA's launch cadence with SLS remained unchanged, Artemis 4 would have launched sometime around 2030.

Space agency officials are counting on a standardized SLS configuration to shorten the wait time between launches, and are now targeting an Artemis 4 liftoff in 2028 as the program's first crewed lunar landing, with the potential for Artemis 5 to repeat the feat later that same year.

"I think what we're doing is directly in line with what ASAP asked us to do," Isaacman told Space.com during Friday's briefing. "I think it should be incredibly obvious you don't go from one uncrewed launch of Orion and SLS, wait three years, go around the moon, wait three years and land on it."

Isaacman compared the need for an increased SLS launch cadence to the United States' first lunar program, saying, "There has to be a better way, in line with our history."

"We did not just jump right to Apollo 11. We did it through Mercury, Gemini and lots of Apollo missions with the launch cadence every three months," Isaacman said. "We shouldn't be comfortable with the current cadence. We should be getting back to basics and doing what we know works."

In the meantime, teams at NASA's Kennedy Space Center continue to work toward an April launch date for Artemis 2, despite its recent relocation from the pad at Launch Complex-39B to the Vehicle Assembly Building (VAB) for repairs.

Engineers conducting routine post-fueling procedures after a Feb. 19 countdown rehearsal for the Artemis 2 rocket encountered a helium flow pressurization issue on ICPS that they could address only back inside the VAB. That countdown practice run was the second "wet dress rehearsal" for the Artemis 2 SLS, which experienced liquid hydrogen leaks and an early countdown termination during testing on Feb. 2.

"The suspected system component for the helium flow will be removed, and they're going to undergo detailed sections and assess the cause of the issue," Lori Glaze, acting associate administrator for NASA's Exploration Systems Development Mission Directorate, said on Friday. "We hope to get down to the root cause of that and make changes, not just to the hardware, but to our operational procedures, so that we don't encounter the same issue again when we roll back out to the pad."

Counting on a quick diagnosis and fix, NASA officials hope to have SLS back on the pad in time to meet Artemis 2's next launch window, which opens April 1, with additional opportunities April 3-6 and April 30.

Artemis 2 will be Orion's first mission with a crew onboard. They are NASA astronauts Reid Wiseman, Victor Glover and Christina Koch and Canadian Space Agency astronaut Jeremy Hansen. The quartet will launch on a 10-day mission to fly in a single loop around the moon before returning to Earth.

Artemis 1 successfully sent an uncrewed Orion capsule to lunar orbit and back to Earth in late 2022.

BREMEN, Germany — With NASA's decision to continue using an interim upper stage for additional flights of the Space Launch System, Boeing is working on changesto both that stage and a more powerful upper stage.

In an Oct. 3 call with reporters, John Shannon, vice president and program manager for the Space Launch System at Boeing, said NASA has asked Boeing to look at changes to the Exploration Upper Stage (EUS) to improve its performance.

Those changes were prompted by the decision NASA made earlier this year to delay the introduction of the EUS. That stage was originally planned to enter use with the second SLS mission, Exploration Mission (EM) 2. Instead, the first flight of what's known as the Block 1B configuration of SLS has been delayed to the fourth SLS launch, likely no earlier than 2024. [Photos: NASA's Space Launch System for Deep Space Flights]

"That has put a slow down on the Exploration Upper Stage work," he said. "We were rapidly approaching the critical design review."

"We're actively working through additional design opportunities to lighten the stage and increase its performance and take even more out to the lunar area, so that the Gateway can be built and we can get human boots back on the surface of the moon," he said.

Shannon said later neither the company nor NASA had a specific goal for increasing the EUS' performance. "It's a very open-ended discussion with NASA," he said, describing it as an opportunity created by the delay in the stage's introduction. "We have some really sharp guys. They're going off and coming up with some really great options for NASA to consider." Those options include changes to the stage itself as well as orbital mechanics techniques.

While he said there was no specific goal for that performance increase, he mentioned later in the call "all the work we're going to do to try and get one or two extra tons of co-manifest payload." NASA has previously advertised a co-manifested payload capacity of about ten tons for the SLS Block 1B.

The decision to delay the EUS' introduction means flying two additional SLS Block 1 missions with the original Interim Cryogenic Propulsion Stage (ICPS). One of those missions will be for EM-2, the first crewed Orion flight, while the other is being reserved for the launch of NASA's Europa Clipper spacecraft to Jupiter's moon Europa.

Shannon said NASA is handling procurement of the additional two ICPS units from United Launch Alliance, which based it on the Delta 4 upper stage. That should be completed in the "next couple months," he said.

The ICPS was originally not planned to be human-rated, but will undergo some changes to be used on the EM-2 mission. The biggest change is the addition of an emergency detection system similar to one used on the Centaur upper stage of the Atlas 5 on commercial crew missions. Additional sensors and instrumentation will be added to the stage both for redundancy and to give astronauts on Orion more information about the status of the stage.

During the call Shannon also addressed the schedule for development of the SLS. The core stage, for which Boeing is the prime contractor, has been on the critical path for the EM-1 launch in mid-2020. It has been running "neck-and-neck" with the Orion service module, as Mark Kirasich, NASA Orion program manager, described it a briefing earlier that day.

"That's a good characterization of it," Shannon said. The focus is getting the core stage completed and delivered to the Stennis Space Center in Mississippi "at the beginning of next summer." It will spend about six months there undergoing testing, including a full-duration firing of its four RS-25 engines.

Once those tests are complete, the core stage will go to the Kennedy Space Center to be integrated with its solid rocket boosters, ICPS and Orion spacecraft for an additional six months of testing. "It looks like everything is lining up and we're staying in sync with Orion from a schedule standpoint," he said. "We'll be able to support the needs of the program."

He admitted that the program had underestimated the amount of effort that would go into developing the vehicle, which has suffered several years of delays. "We underestimated that somewhat. We thought we would be able to reuse hardware without as extensive a [qualification] as we've done on some it," he said. "But as we got into testing and understood the environments in an SLS, it required us to go back and do additional qualification work."

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