While Artemis II schedule remains uncertain, NASA EGS preparing to be ready and waiting for stacking

by Philip Sloss

At the Kennedy Space Center (KSC), NASA’s Exploration Ground Systems (EGS) program continues to prepare for the Artemis II circumlunar mission that was recently delayed to September 2025. EGS is finishing certification of new ground systems to support crewed launches of the agency’s Orion spacecraft with its Space Launch System (SLS) rocket beginning with Artemis II.

NASA recently disclosed new issues that the Orion program is working to resolve that are delaying the launch readiness of Artemis II by an additional 10 months. While Orion is working on those issues and determining how long it will take to resolve them, EGS has adjusted their near-term schedules for finishing their certification work and preparing SLS solid rocket booster (SRB) hardware to eventually be stacked for Artemis II. Depending on Orion’s progress, it is hoped that stacking for the mission could begin later this year.

EGS finishing new Mobile Launcher, Pad 39B systems validations

NASA announced the 10-month delay to the target launch date for the Artemis II lunar flyby mission in a media audio conference on Jan. 9. The public target date for the launch moved from November 2024 to September 2025 and was attributed to additional engineering and production work necessary on the Orion spacecraft before it can be fully outfitted and turned over to EGS for launch processing.

The Orion program is now working to resolve multiple issues uncovered during both the production of future spacecraft and its human-rating certification work for Artemis II. The behavior of Artemis I’s base heatshield as the crew module returned to Earth in December 2022 is also still being investigated and could be a factor in deciding the final Artemis II launch date.

The EGS, Orion, and SLS programs are now replanning based on the long delay. While a new milestone schedule is being worked out, EGS is finishing the verification and validation of upgrades to ground hardware and software to support the beginning of crewed Orion/SLS launches from Launch Pad 39B.

“We’ve got a lot of testing that we’re in the middle of right now, with all the different tests,” Cliff Lanham, NASA EGS senior vehicle operations manager, said in a recent interview with NSF. “We’re looking to complete those in I’ll say the early-to-mid spring timeframe and then late spring we’re looking to roll the Mobile Launcher back to the VAB.”

Mobile Launcher-1 (ML-1) rolled out to Pad 39B last August, after Artemis I post-launch repairs, refurbishment, and installation of elements of a new emergency egress system (EES).

Credit: NASA/Isaac Watson.

(Photo Caption: The first slidewire basket is seen Jan. 24 during initial setups for validating the emergency egress system for crewed Artemis launches that begin with Artemis II.)

Before a launch, the pad workforce will be cleared from the area while SLS is loaded with propellants. However, as crewed flights begin, both the astronaut flight crew and closeout crew support team will be on the Mobile Launcher to help the astronauts board Orion. The egress system, which is similar to ones used for Commercial Crew and previous NASA crewed transportation systems like the Space Shuttle, will allow personnel at the pad to quickly get away from the vehicle and Mobile Launcher (ML) in case of an emergency.

Four baskets will be staged on the ML umbilical tower at the 274-foot level, which is where the crew access arm and “white room” are located for crews to enter and exit the Orion crew module. The baskets will run down slidewires to a terminus area on the west edge of the pad infield, where mine resistant ambush protected (MRAP) emergency transport vehicles will be parked that can be driven away from the pad.

Currently, EGS is setting up the first of the four slidewire baskets to begin verification testing. “We’re fitting up that first basket to the rail system up on the Mobile Launcher tower,” Lanham explained. “We’ve got some software that we’re finishing up over the weekend and we’re looking right now at Monday [Jan. 29] to get into our drop testing with the baskets, where we’re actually testing the baskets and the braking and the different systems that are part of that first basket run.”

“Once we complete all that, then we’ll get into the other three baskets and do similar drop testing with those.” The first set of tests is being performed by the construction contractor, JP Donovan.

“That’s called commissioning,” Lanham noted. “Right now, we’re looking at finishing that up in the mid-spring timeframe to finish that testing, and then at the end of that testing by the construction contractor, we would then go into, with our operations contractor, the actual verification and validation testing for several weeks.”

“Once that’s complete, we get into another ISVV or integrated system verification and validation test where we’ll actually bring the crew out, and that’s called ‘ISVV 1,'” he added. “We’ll run through, with the crew, the launch day sequence of events and also we’ll be swinging the baskets down the tower.”

The crew participated in an initial run of the launch day sequence of events last September; the next test run will add practice for emergency modes that might require quick evacuation. “They would come out of the vehicle, go down the walkway of the Crew Access Arm, across Level 274 of the Mobile Launcher over to where the baskets are. They’ll practice that, they’ll get familiar with the pathway, and then practice with the baskets,” Lanham noted.

Credit: NASA.

(Photo Caption: Shuttle STS-109 mission pilot Duane Carey leads commander Scott Altman in evacuation practice during terminal countdown demonstration test activities in February 2002. The Artemis II flight crew will help commission the new emergency egress system by participating in similar practices between now and their launch, currently targeted for September 2025.)

Orion’s launch abort system (LAS) will be available for the crew to use at the very end of the countdown, but up until then, the EES provides another evacuation route for both the flight crew and closeout crew if the latter team is still at the pad before launch.

Another important aspect of the verification and validation (V&V) testing at the pad is practice for setting up the system for launch. In contrast to the Commercial Crew launch pads and the Shuttle before them, Pad 39B is a clean pad, with no fixed crew access tower.

Access to the vehicle is more like the Saturn V vehicles that originally flew from the Launch Complex 39 pads over 50 years ago, with crew access on the umbilical tower of the Mobile Launcher. For SLS, the concept of operations is to roll the vehicle and ML out to Pad 39B a little more than a week before the planned launch date, which means that the EES slidewires and baskets will need to be set up as a part of launch countdown preparations.

“That’ll all be a part of the [verification testing], that is where we practice setting up the system,” Lanham said. “We’ve got to run cables up to the tower from the terminus site, so we’ll practice that, we’ll time that, and that’ll all roll into the launch countdown timeframe when we roll out, so that’ll all be taken into account and worked.”

“And also any time we get the opportunity, like through the V&V phase of the testing, the COMET contractor will likewise be looking at those timelines as they put the system through its verification and validation.” Jacobs Technology is the prime launch processing contractor for KSC’s Consolidated Operations, Management, Engineering, and Test (COMET) contract.

Launch pad systems at 39B, such as the environment control system, have also been modified and upgraded between Artemis I and II, and those changes are being validated too. A major new capability being brought online beginning with Artemis II is a second, large liquid hydrogen (LH2) storage sphere to increase the original capacity at 39B to better support the needs of current and future SLS configurations.

The new sphere will increase the number of Orion/SLS launch attempts that EGS can support, which should improve the chances of launching within the heavily constrained lunar launch periods that Artemis requires. One of the V&V tests that EGS is preparing for is to check out the LH2 loading system with both large storage spheres online and interconnected.

“We have what’s called our integrated system verification and validation test four, which is a cold flow/cryo flow of LH2 from that [new LH2 sphere] to the ML,” Lanham said. “We have found some corrosion on some pipelines and on our vent lines and we’re working to get that fixed.”

Credit: Julia Bergeron for NSF.

(Photo Caption: The two, large LH2 storage spheres are seen in this image from a recent NSF flyover of the Kennedy Space Center. EGS will be validating that the new, larger sphere on the left is ready to support Artemis launches beginning with Artemis II. Plans call for the new sphere to be used to flow LH2 into SLS stages on the pad and for the original, Apollo-era sphere to be used for replenishment as necessary.)

“We’re kind of building a contingency plan to go ahead and do a cold flow from the old sphere to the Mobile Launcher before we were to roll off the pad, in order to keep our schedule for Artemis II, and in the meantime we would complete that repair on that piping and then do a flow between tanks to allow us to complete that test in parts, which is perfectly valid as part of a certification program. So, right now we’re thinking in the early to mid-spring timeframe we would be doing the Mobile Launcher portion of that cryo flow.”

For tanking operations with the SLS rocket and Orion spacecraft, the plan is for the new, larger capacity LH2 sphere to supply the cryogenic fuel from the storage farm through the cross-county lines at the pad, into the ML plumbing, and eventually into the two SLS liquid-propellant stages. “The idea would be the old sphere is actually the replenishment sphere, back to the new sphere,” Lanham noted. “So, we would load from the new sphere and use the other one to replenish.”

A series of ISVV tests has been underway since ML-1 arrived at the pad last summer. One set of tests was just completed, fine-tuning the water flow from the Pad 39B water tank into the ignition over-pressure protection and sound suppression (IOPSS) system.

“We just finished, literally as I’m talking to you, the last water flow, which is called ISVV 2,” Lanham said in the Jan. 25 interview. “That was our final flow of water for that. That included ISVV 6, which is our high-speed imagery test.”

“We did those in conjunction with each other, that final water flow plus that imagery test. We just completed that, so that’s very good news.”

SLS Boosters almost ready to stack, will wait for better schedule clarity

Over in the Vehicle Assembly Building (VAB) area of Launch Complex 39, EGS is completing Artemis II stacking preparations of SLS solid rocket booster (SRB) segment hardware in the Rotation, Processing, and Surge Facility (RPSF). Both sets of the two five-segment SLS boosters were transported by rail from Northrop Grumman’s Promontory facility in Utah to KSC in late September.

Since they arrived at KSC, each of the ten fueled solid rocket motor segments has been offloaded and inspected. “All the segments are offloaded now and six of the 10 segments are in Surge 2, ready for stacking when we get to that point,” Lanham said. All of the segments are offloaded in the RPSF Rotation building. After receiving inspections, eight of them are placed in one of the two “Surge” buildings for storage.

Credit: NASA/Frank Michaux.

(Photo Caption: Four of the solid rocket motor segments for Artemis II are seen in the RPSF on Dec. 21. An unidentified center segment is to the far left as the left-hand center-center segment is rotated, post-offload. To the right, the two aft assemblies are seen in their build-up stands.)

The two aft segments are installed in buildup stands in the Rotation building, where each is mated to an aft skirt. A nozzle extension — also called an exit cone — is attached, along with the aft attachment ring that helps connect each booster to the SLS core stage. When fully outfitted, each is called an aft assembly.

“We have roughly about a month of work left,” Lanham said about the aft assemblies. “We’re doing the developmental flight instrumentation (DFI) work where we’re routing some cables, wires, around that area of the attach ring and then we fill that area with cork, which is a lot of work going on right now.”

“We finished our leak checks of the aft exit cones recently, so we have about a month of work left in that area, and towards the end of February we’re expecting to have the segments ready for stacking.” The other two segments that remain in the RPSF Rotation building are the center-center segments.

“What we’re doing there is just yesterday we completed our masking and outlining of the NASA worm logo, so they’ll remain in the [Rotation building] as we paint on the worm logo to those segments, so you’ve got six segments in Surge 2 and you’ve got four in the Rotation building,” Lanham added.

The SRBs have five motor segments: forward, forward-center, center-center, aft-center, and aft. A forward assembly on top includes booster avionics and a nose cone with one set of separation motors. The aft assembly includes the aft motor segment, exit cone, core stage attach ring, and the aft skirt that houses thrust vector control (TVC) systems and the second set of separation motors.

A systems tunnel runs vertically along the length of the booster, which is where the NASA worm logo resides on the center-center segment. As with the Artemis I boosters, most of the logo will be painted around the systems tunnel area in the RPSF now. After that, those two segments will be moved to the Surge 2 building for storage. The remainder of the logo will be finished after the systems tunnel covers are attached to the fully stacked boosters on the Mobile Launcher in the VAB.

Credit: Julia Bergeron for NSF.

(Photo Caption: The three main RPSF buildings are seen in this image from a recent NSF flyover of KSC. On the far left is one of the two storage buildings, Surge 2. In the middle, closest to the camera, the Rotation building is where all the SRB segments are offloaded and inspected; it is also where the aft segments, aft skirts, and exit cones are assembled into the booster aft assemblies. Immediately behind the Rotation building is the original Surge building. During the higher flight-rate Space Shuttle program, KSC ground operations might have been processing two or more sets of SRBs between the VAB and the RPSF and storing others in the Surge buildings.)

Although the SRB hardware could be ready to support the beginning of vehicle integration or “stacking” in the next several weeks for Artemis II, it is too early to start that with over a year and a half until the new target launch date. The new September 2025 target date was based on forecasts to resolve one of the issues, a redesign of a circuit within an electrical motor drive controller in the Orion environmental control and life support system (ECLSS). This issue will require taking some electronics out of the Artemis II Orion spacecraft and then retesting them after they have been replaced.

“At this point, we drove that September date based on the time we think it’s going to take to do the removal [and] replacement of the [Orion] life support system electronics and the penalty testing required to do the integration on the way back out,” Amit Kshatriya, deputy associate administrator for the Moon to Mars Program in NASA’s Exploration Systems Development Mission Directorate, said in the Jan. 9 media audio conference where the delays were announced. “We’re hopeful that the other findings that are as a result of abort loads on the battery, as well as the conclusion of all the tests required for the heatshield, is enveloped by that work.”

Previously, the EGS and SLS programs were preparing to begin stacking the Artemis II vehicle early this year, starting with the SLS SRBs and followed by the cryogenic core and upper stages. With the new target launch date, the programs will be re-evaluating when to deliver the core stage, which is finishing its production at the Michoud Assembly Facility (MAF) in New Orleans.

The delivery schedule of the other SLS hardware — adapters that connect the stages and Orion — will also need to be reworked. Estimates had been that EGS would need at least eight months to prepare Orion from the point they received the spacecraft to the point of Artemis II launch readiness. If that were the case, Orion would need to resolve the issues, make all the necessary changes, and finish outfitting and retesting the spacecraft by the end of the year to make a September 2025 launch date.

In short, apart from the boosters, the pieces needed to support stacking are not in place and it’s not yet clear when they will be ready. For now, as Lanham said, EGS is tentatively working towards bringing the Mobile Launcher back to VAB High Bay 3 around the end of the spring.

“At that point, we would get into a series of work, where we prep the VAB, we prep the Mobile Launcher, umbilicals, and get ourselves postured [to] start stacking the boosters,” he said. “I’m using reference timelines, because we’re still laying out the schedule, still working the details, but we’re looking at the early summer to get into the booster stacking if all goes well.”

Credit: NASA/Frank Michaux.

(Photo Caption: The top of what would be an “ICPS Short Stack” is seen from the Mobile Launcher umbilical tower cameras in 2021 during the Artemis I launch campaign. A tanking test of the Artemis II SLS vehicle’s core stage and Interim Cryogenic Propulsion Stage (ICPS) with the Mobile Launcher and Pad 39B propellant systems will be conducted likely next year. Either the full vehicle with Orion will roll out to the pad for that test, or just the SLS Block 1 rocket elements with the ICPS on top.)

The SLS core stage is the centerpiece of the rocket and Lanham said that delivery of Core Stage-2 to KSC will be worked out between the EGS and SLS programs. “Core stage delivery, from a hardware need date, is driven off of the stacking of the boosters, so what we do is we look at where that timeframe will fall, and then we back up to the left and we look at the work that we have to do in the transfer aisle on the core stage, and then we kind of say ‘what’s the margin we feel we need for that?’ We kind of get an idea of the total timeframe that we need for [the] core stage and that puts us in the vicinity of a date out to the left that we then negotiate with the SLS program.”

“In general, we try and do a ‘just-in-time’ delivery on the hardware, because when the hardware gets here, there is care and feeding of the flight hardware with our technicians and engineers, and having it here too early puts a burden on them that we try to avoid,” Lanham added. He estimated that receiving the core stage about eight weeks before they expect to stack it with the SLS boosters would provide the work time and schedule margin needed.

Whether stacking could begin as early as summertime with placing the booster aft assemblies on the Mobile Launcher will remain a question while the Orion program works through their newly reported issues.

“What will happen is, as we get closer to the date to start stacking, we’ll have what’s called a KMR,” Lanham said. KMR stands for “key milestone review.” “We’ll get everybody, including our sister programs, together and we’ll discuss ‘Is everybody ready to start the stacking?'” he added. “Obviously, things come up and we’ll adjust accordingly.”

The boosters are one of the “limited operational life items” (LOLI) on the spacecraft and the rocket. They have a generic stacking life of 12 months and for Artemis I, extending that life required additional analytical work for each extension. Stacking of the Artemis I boosters was paused once for the SLS core stage Green Run, but the “stack life” still ended up being almost two years.

NASA leadership has previously said one of the lessons learned from Artemis I was to better “protect” the standard 12-month stacking clock for the boosters. In addition, for Artemis II, Lanham said they are not planning to pause the booster segment stacking schedule after they start with the aft assemblies.

Looking at options for Artemis II tanking test, pad access

Once the Artemis II vehicle is stacked, there will be a tanking test conducted, where the vehicle will roll out on the Mobile Launcher to Pad 39B separately from launch. Following the test, it will be rolled back to the VAB to complete the remaining launch preparations. Only SLS is loaded with propellants on launch day itself; the Orion spacecraft is fueled for the mission months in advance. One of the questions for the test is whether or not to perform it with Orion integrated on top.

A tanking test working group was formed last year to take a look at the options. At some point in the future, after there is more certainty in Orion’s schedule, a decision will be made by NASA leadership about using a full vehicle stack with Orion or a “short stack” without Orion for the tanking test.

“We will do a tanking test, it’s just a matter of what that configuration will look like,” Lanham said. “The short stack configuration would be ICPS with a cover, and then the full stack obviously would be the entire vehicle with Orion stacked. But that’s all still being weighed and looked at.”

Credit: NASA/Frank Michaux and Kim Shiflett.

(Photo Caption: VAB platforms, scaffolding, and test equipment are shown deployed around the forward skirts of the Artemis I SLS Boosters and core stage intertank in the main image taken in August 2021. Inset in the lower left, an image taken from the Mobile Launcher umbilical tower during the umbilical release and retract test in late September shows the location of yellow and red-colored access doors for the Boosters and core stage on the -Z side of the vehicle. EGS is studying the feasibility of whether safe access for launch team personnel could be provided to those access doors at Pad 39B to allow testing and reconfiguration of internal equipment.)

For Artemis I, a series of one-time tests was conducted as part of that launch campaign on the stacked vehicle. A low-fidelity mass simulator for Orion was constructed for some of those tests, possibly including testing with the SLS stack at the launch pad. As it turned out, it wasn’t necessary to use the mass simulator for rollout or pad testing. Now, for Artemis II, a tanking test configuration without Orion would also not include any mass simulators or Orion-to-SLS connecting hardware.

The “ICPS Short Stack” option would just be the SLS core stage and boosters, plus the Interim Cryogenic Propulsion Stage (ICPS) on top, with the Launch Vehicle Stage Adapter (LVSA) connecting the ICPS and core stage. Only the core stage and ICPS would be fueled for the tanking test, whether or not Orion is there.

The extra time that comes with the delay is also allowing teams to take a look at the possibility of increasing access inside the vehicle at Pad 39B to improve launch availability for Artemis II. The lunar launch opportunities for Artemis II should be similar to Artemis I in a general sense, where there would be a repeating cycle of about two weeks where SLS could launch Orion to the Moon followed by two weeks where that would not be possible.

Similar to Artemis I, the availability to launch is further constrained by the 25-day certification life for the SLS flight termination system (FTS) on the Eastern Test Range where Cape Canaveral Space Force Station and KSC launches are conducted. Once the 25 days are up, the system needs to be retested to renew its certification for another 25 days, and under current circumstances that testing can only be performed in the VAB.

The tests themselves might only take several days, but the additional overhead that comes along with moving the vehicle back to the VAB from the pad to retest and then roll back out is much longer than that. “The idea would be to give us that access to the vehicle, basically to eliminate the need to roll back if we could do the FTS testing at the pad,” Lanham said. “So we’re looking at what would it take to get pad access into those forward assemblies of the boosters and the intertank of the core stage to do that.”

The access doors for the booster forward assemblies and one of the access doors for the core stage intertank face the Mobile Launcher umbilical tower. “We’re studying that, it’s still in the early stages at this point, but that’s what we’d be looking to do,” Lanham noted.

(Lead image: Mobile Launcher-1 is seen at Launch Pad 39B during a recent NSF flyover of the Kennedy Space Center. Integrated testing between the mobile launcher and pad systems is expected to continue into the spring. Credit: Max Evans for NSF)

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