NASA modifies ML-1 for Artemis II, ML-2 under construction for SLS Block IB

by Nathan Barker

As construction begins to assemble the Mobile Launcher-2 (ML-2) for Artemis IV, Mobile Launcher-1 (ML-1) secured its position once again back on top of Launch Complex 39B for pad validation and testing. This comes after ML-1 spent the better part of this year undergoing repairs and upgrades outside of the VAB at the West Park Site following Artemis I.

Nathan Barker chatted with David Sumner, Senior Project Manager for NASA’s Exploration Ground Systems (EGS) for ML-1 on Artemis II, in an interview with NASASpaceflight.

Ignition Overpressure Protection and Sound Suppression (IOP/SS)

One of the more not so noticeable changes to the Mobile Launcher (ML) deck included upgrading the rainbirds, and the Ignition Overpressure Protection and Sound Suppression (IOP/SS) systems. “We have five rainbird heads around the ML, and we have modified all five of those for a couple of reasons,” said Sumner.

“One is for water flow improvement and coverage on the deck, and the other one to try to improve our imagery as well as compared to Artemis I.” He continues, “One of the heads we changed to what we call the ‘pringle.’ It was a brand-new head, fully redesigned, rebuilt, and that was more for the water and the water flow dispersion.

“The other four rainbird heads we put basically deflectors onto the Artemis I heads. Those are directed mainly to throw the water down and off of the cameras that are on the [zero] deck.”

While we were accustomed to the red water bags that covered the Solid Rocket Booster (SRB) flame holes during the Shuttle program, there are no plans to implement such changes.

“We took a look back at shuttle with the water bags and all of that kind of thing later on in the STS flights, but we’re not planning to do that this time. So, we’re really looking at the protection of the [zero] deck, to protect the mobile launcher and improve our imagery,” said Sumner.

The blast plates on the ML deck will also be replaced and the supports around them will be strengthened. “They’re basically on the perimeter of the flame hole, and that’s where we see the most blast pressures. And they’re basically partly there to protect the [zero] deck structure and take the majority of that blast.”

“We did take some damage, they did warp some, so we had to go [with] new [plates],” Sumner continued. “There’s also what we call water dams, and it’s basically plates that when the ignition overpressure flows, that it redirects some of the flow, again for imagery and to keep the water from going directly into the vehicle. We’re reinstalling new plates, the water dams below, and we’re also looking at adding upper water dams. And again, that is for imagery improvement.”

“Best case we will be able to use these through Artemis II and Artemis III,” Sumner explained. “Worst case, they’re sacrificial and the blast plates will have to be replaced again after Artemis II, so we’ll have to see how that goes. But I do know they’re trying to make some improvements based on what we saw during Artemis I.”

“Those changes may include change in thickness, strength, and some other structural reinforcements that they are adding.”

The damage to the blast plates did not come as a surprise, and according to Sumner, “I would say there was some risk known there that those [blast plates] may be sacrificial or that the warping may happen.”

“So we did know, we were prepared to refabricate those if needed, and it was needed. So we’ve went right into that and those are being replaced right now and we’re replacing those out at the pad. Schedule wise we’re in good shape with the replacement of those,” he added. “The teams are preparing for the first IOP flow test out at the pad here in the next few weeks. ”

Repairs on the ML

It was previously noted in an earlier interview that modifications to improve the liquid hydrogen systems on the ML in response to issues faced during the various Wet Dress Rehearsals and launch counts could be required. “We have not done any major modification on liquid hydrogen,” said Sumner.

“We’ve repaired anything that was damaged during launch and brought them back to what we had before. I know there were some lessons learned out of the Artemis I wet dress. I would say on the operation side of the house, they’re working to correct those lessons learned.”

However, additional work is occurring to harden the Gaseous Nitrogen, GN2, system on the ML to avoid the challenges experienced during Artemis I. “We definitely looked into that one because that affected our fire suppression activity, if we needed activation or wash down,” noted Sumner.

ML-2 rising out of the ground – via Julia Bergeron for NSF

All damaged GN2 lines were replaced on the ML during its time at the West Park Site with some being hardened with additional shielding.  Sumner added, “We saw some vibrations [at the base area] that were a little unexpected. Everything was hard piped, and so we’re looking at ways if we can put some flex connections in there to give it a little bit more flexibility to move around.”

“So, there’s a few different mitigations that we’re doing there with the GN2 system, but it’s coming along very well. We have a couple different contracts working on it right now and we will have the GN2 back up online here shortly, and we have [it] partially online now, but we’re going to fully get through the system hopefully here by the end of August, and that’ll put us back into fire suppression testing and some other GN2 testing that we have to do with that.”

Another noticeable area of damage was that of the elevators on the ML which required substantial refurbishment. “That design is still in work right now with our engineering teams, and it’s basically a holistic design on hardening the elevator systems and the blast doors that get closed for launch,” said Sumner.

Inside the shaft, “the rails inside [that] the elevators ride on … we should be getting a design here in the next few weeks hopefully to start implementing and hardening that system so that we don’t see the same damage and losses that we saw during Artemis I.”

Emergency Crew Escape System

In order to support crew missions, ML-1 has been modified with the Emergency Crew Escape System. In the event of an on pad emergency, Wiseman, Glover, Koch, and Hansen would be required to evacuate the ML and pad via slide wire baskets immediately.

Sumner explained that “just before going to the pad, we made quite a bit of progress as all the platforms were installed. We had the four pipeline hoists for the baskets and the cable themselves. Those are installed on level 325.”

“Once we get to the pad, we do have equipment being shipped here. The basket fabrication is coming along very well. We’ve gone through probably about a little more than half or 75 percent of our factory acceptance testing. That’ll prep us to be ready to ship those baskets out here to KSC in the next few weeks, and then we’ll start getting the whole system set up.”

“So we’re making really good progress on some big equipment that is finally starting to show up” Sumner added. “At the same time, we’re preparing all of our test plans, and we’ll begin integrating the whole system and pulling it together. There is a lot to go and a short period of time though as well. Right now we’re looking at trying to get everything tested in the next 90 days or so.”

Once the final installation is complete, integrated testing of the baskets will occur. “Different scenarios are required – fairly extensive as far as the varying weight conditions, wind conditions, wind direction, and wind speed. We have to test all of those as well as failure modes in the baskets themselves and on the braking system. We’re not planning on putting any people on the baskets during the testing, so we’ll use some kind of ballast,” said Sumner.

He added, “We’ll run all four baskets through every test that we can to be able to buy off on all the requirements that we have and fully be ready to turn that system over for operation when we’re done.”

Sumner noted that “we’re trying to give our Launch Director and her office as much availability as possible throughout the year to be able to launch and not be dependent on constraints with emergency escape system.”

The addition of the crew escape system adds 250,000 pounds in new equipment and platforms to the ML. Sumner noted this “does not affect anything with the roll out and the limitations on the CT or the crawler way or anything like that. We’re still within those bounds.”

Crew Access Arm

Not since STS-116 when Space Shuttle Discovery launched in December of 2006 has a flight crew walked across a crew access arm at 39B. “We have to certify the Crew Access Arm for Artemis II”, said Sumner. “The CAA requires over 100 swings that we have to do for certification, so we’re going to be in a position here in the next couple weeks to start those swings, and we’re ready as the hardware is basically complete.”

“We’ve got a little bit of software work to do before then to get everybody ready to start doing these swing tests. Those are going to start on a daily cycle hopefully here in the next two or three weeks.” Teams plan to put the access arm through its series of swing tests and complete certification before the ML is needed back in the VAB for stacking.

While the majority of testing is scheduled to be completed in November, crews at 39B will be kept busy completing additional work that will take them into the December-January timeframe. Once this final work is complete, CT-2 will roll back under ML-1, picking it up for the journey back to the VAB for Artemis II stacking. Artemis II is currently targeted for late November 2024.

(Lead Image showing ML-1 and the start of ML-2 at KSC via NSF Flyover – Max Evans).

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