EGS preparing ML-1 for validation tests at the Pad

by Philip Sloss

Exploration Ground Systems (EGS) is getting Mobile Launcher-1 (ML-1) ready to roll out to Kennedy Space Center (KSC) Launch Pad 39B next week as it moves through the final phases of integration and testing of the combination launch umbilical tower and platform ahead of the Artemis 1 launch. ML-1 is currently going through verification and validation (V&V) testing in the Vehicle Assembly Building (VAB) at KSC.

Along with confirming that installation of systems up and down the tower and on the platform are complete, the testing inside High Bay 3 of the VAB also verifies that the Launch Control Center can command and control ML-1 in anticipation of assembly of the first integrated Orion and Space Launch System (SLS) vehicle prior to a launch late in 2020 or 2021.

The current round of outfitting and V&V testing is working on data, electrical, mechanical, and other services employed during vehicle assembly, while the Summer at the launch pad will also checkout fluid and propellant-related connections to and operations with the pad systems needed to launch Artemis 1.

Wrapping up swing arm testing in the VAB ahead of pad rollout

ML-1 is the platform that the SLS launch vehicle stands on, along with the umbilicals that provide all the services needed by the launcher and the Orion spacecraft. Artemis 1 (also known as Exploration Mission-1) is the first launch of SLS and the first use of ML-1 and all the EGS-related Launch Complex 39 (LC-39) infrastructure.

The launch will also start the second Orion mission and is the first flight integrating all three Exploration Systems Development (ESD) programs (EGS, Orion, SLS). The upcoming rollout to Pad 39B, currently scheduled for June 27, marks completion of most of the installation and outfitting of the Mobile Launcher (ML) and the end of the first round of V&V testing in the VAB.

Credit: NASA.

(Photo Caption: The Mobile Launcher umbilicals and connections for the SLS Block 1 Crew vehicle configuration for Artemis 1. The umbilical arms attached to the Core Stage and Interim Cryogenic Propulsion Stage (ICPS) swing away from the rising vehicle after the umbilical plates disconnect at liftoff. Hydraulic extension and retraction of the arms individually and in groups is being tested in the VAB this month.)

“We rolled into the VAB back in early September and at that point we still had some installation work to do and then we got into our Multi Element Verification and Validation (MEV&V) testing which is our big testing effort between the VAB and the Mobile Launcher,” Cliff Lanham, EGS Senior Project Manager for the Mobile Launcher, said in a June 10 interview.

As all of the subsystems and components are installed on the ML, the MEV&V testing makes sure they are meeting their functional and other requirements, both as standalone systems, but also connected to VAB services.

Testing also verifies the command and control infrastructure to the ML from the Firing Rooms in the LC-39 Launch Control Center adjacent to the assembly building. “Some of the series of testing that went on was for each of our electrical systems,” Lanham explained.

“We went through and performed end-to-end testing where we basically run in many cases locally, meaning we can control from the Mobile Launcher the subsystem or the electrical system out to the end of the umbilicals. Then once we were confident in that we then go to a remote testing where test our systems from the Firing Room all the way through the VAB through the ML out to the end of the arms.”

“We also have been swinging the arms, so we have been testing the Core Stage Forward Skirt Umbilical (CSFSU) and swinging that, the Core Stage Inter-Tank Umbilical (CSITU), the Interim Cryo Propulsion Stage Umbilical (ICPSU), have all been going through a series of swing testing throughout the past several months,” he added.

“Along those same lines the Orion Service Module Umbilical (OSMU) has also been tested [and] we’ve been prepping the Tail Service Mast Umbilicals (TSMU) and getting ready for drop testing which we’ll be performing in the next week or so, hopefully this week, to get that done as we prep for the roll to the pad.”

Credit: NASA/Frank Michaux.

(Photo Caption: The Core Stage Inter-Tank Umbilical arm in February as swing arm testing was beginning in the VAB.  The umbilical plate at the end of the arm (middle left) mates to a plate on the Core Stage intertank to (among other things) provide air conditioning to stage avionics and to allow hydrogen gas boil off from the liquid hydrogen tank to be vented away from the vehicle.)

“We make sure that we can control it when we extend the arm because obviously you don’t want something that could possible damage the vehicle, but primarily what you’re looking for, the big bulk of the testing is tuning the arm so that it will appropriately swing back and brake and connect to the tower the right way,” he explained.

Most of the other ML systems are in various phases of testing. “There’s also some other fluid-type systems, hydraulic systems,” Lanham noted.

“We’ve been testing the TVC (Thrust Vector Control)/hydraulic subsystem, which provides hydraulic servicing to the Boosters and the Core Stage systems and we’ve also been doing a lot of environmental control system (ECS) testing. There we test out through the system to a portable purge unit outside the VAB.”

“They provide the air-conditioning and such up through the VAB, through the Mobile Launcher system out to the ends of the arms and we’ve been doing testing there to ensure we can deliver all the proper air and temperatures and humidities, those types of things out to the ends of the arms where they feed the vehicle,” he added. “We’ve also done the backup testing where if we were to have a failure with a portable purge unit we [have] mini-purge units.”

Credit: NASA.

(Photo Caption: The Core Stage Inter-Tank Umbilical arm in an extended position away from the ML tower during swing arm testing in the VAB.  At liftoff, the ground and vehicle plates are separated and the ML’s hydraulic arm subsystem swings this and other T-0 umbilicals away from the rising vehicle.)

“We do all the same testing to make sure we can supply what’s needed to the vehicle.”

In addition to the vehicle’s hydraulic system needs, the ML swing arms are also hydraulically actuated and an additional, pre-rollout swing test is planned to retract the ICPSU, the CSFSU, and CSITU at the same time. “It’s called an Integrated System Verification and Validation (ISVV) test,” Lanham said.

“The HAASP (Hydraulic Arms and Accessories Service Pressure subsystem) is the hydraulic system that controls the arms, so we’ll do a simultaneous retract of those three arms.” Lanham said the simultaneous retract ISVV test is an end-to-end test that will be commanded from the Firing Room.

He also noted they are wrapping up drop testing of the Vehicle Stabilizer and working on testing and checkout of the hazardous gas detection system.

Finishing pre-rollout installations

In addition to all of the testing on completed sections of the ML, installations and other work also continue ahead of the rollout. “From the standpoint of installation work in the VAB we’ve had to do some structural mods and we’ve been working through those,” Lanham noted.

“We’re about ninety, ninety-five percent complete on the structural mods that we’ve been working. We’ve been doing a lot of pneumatics work, finalizing the tubing throughout the Mobile Launcher and then getting all those systems cleaned.”

“Basically what you’ve got to do is go through and you pressure test the systems, then you’ve got to clean them and then you’ve got to dry them and then once the pneumatic pieces are in place we get into testing pneumatic systems as well,” he added. Testing of the pneumatic system, which functions as a part of the propellant loading infrastructure will continue at the pad ahead of a propellant loading demonstration planned there.

Credit: NASA/Kim Shiflett.

(Photo Caption: The south-facing side of the flame deflector, showing some of the Ignition Over-Pressure/Sound Suppression water system plumbing.  The pad deluge and other water flows will be tested with the Mobile Launcher in place for the first time this Summer.)

“We’ve also been putting in nozzles which are [for] the IOP (Ignition Over-Pressure)/Sound Suppression system,” Lanham said. “We’ve had to weld [them] into the flame hole and get those positioned properly, they’re all in.”

Lanham said there are twenty-eight nozzles around the flame hole. “There’s eight on each side for the Core Stage and then six on each booster,” he noted. “This week we’ll be putting on the rainbirds, which go on the 0-deck.”

Lanham also noted that testing of the IOP/Sound Suppression water system with the ML is one of the first set of Pad-ML MEV&V tests. “We’ve got to get the rainbirds installed to be ready for our water flows when we first get out to the pad, so we’re working to get that done,” he said.

“Right now what we’re trying to get accomplished before we leave would be the engine service platforms, we’re trying to get those installed and tested but again if we don’t get that done we can do that at the pad. That’s one area we’re trying to complete.”

“We’ve got some ICPSU arm swings to complete so we’re still working on those,” he added. “We’re doing some haz gas testing that’ll go right up to when we’re ready to leave.”

Modal testing on second shift

Lanham said that the team is current working two shifts in the VAB to get ready for rollout. In addition to the integration and testing work to complete the ML to support its first launch, a modal test of the ML is being conducted prior to rollout.

“We’re getting ready for the modal test which will be our next really big test, which kicks off second shift this coming Sunday night the sixteenth,” he said. “That’s where we’ll be driving the Mobile Launcher and seeing how it responds to different inputs and then they’ll be recording all that data, so we’ll be doing that over the next several weeks just about right up until when we roll.”

“So the idea here is we’re going to do the modal on second shift,” he explained. “What we’ll be doing is a 12-hour shift and then we’ll be doing our regular work and other testing on the first shift, so we’ll continue to test right on up to when we’re ready to roll out.”

Credit: NASA/Frank Michaux.

(Photo Caption: The upper umbilical/access arms on the Mobile Launcher umbilical tower back in September following roll into VAB High Bay 3.  Pictured here, from the top are the extended Crew Access Arm and Orion Service Module Umbilical, then the retracted Interim Cryogenic Propulsion Stage Umbilical and Core Stage Forward Skirt Umbilical.)

The plan is to finish as much work as possible before rolling out to the pad, but in addition to finishing leftover systems testing there will also be some other work done out at the pad along with the MEV&V.

“There will be some what I would call ‘punch list’ items that remain from the installation and the construction work, so we’ll be doing punch list items,” Lanham said. “We do have just a little bit of structural work that we’ve got to complete that we won’t finish in the VAB that we’re going to finish up at the pad.”

“Things like painting and architectural finishes, where we’ve got to put like acoustic tile in the electrical rooms, that type of stuff will be finalized. Really ‘cats and dogs’ types of stuff that we’ll have to finish up, including all the other testing at the pad, MEVV testing.”

The testing will continue during the rollout. “On the way out we’ll be essentially capturing the vibrations of the system as we roll out,” Lanhan said.

“It’s a dynamic check of how things are reacting during the actual roll. So we’ll be checking that for both the base and tower of the Mobile Launcher, we’ll be capturing that. There’s some ECS testing, Environmental Control System testing, we’ll be doing as we roll out.”

Getting ready for handover to operations

The multi-element testing first in the VAB and next out at the launch pad is pointed at finishing construction of the ML so it can be turned over to ground operations to begin launch preparations for Artemis 1. Testing at Pad 39B is scheduled to run through the Summer, with the ML being rolled back to the VAB around the end of September.

After returning to the VAB from the pad, a few more tests and a partial booster stacking exercise will be conducted along with formal reviews to certify the ML is complete and ready to support its first launch.

Credit: NASA/Michael Miller.

(Photo Caption: A fire extinguishing system (Firex) test of Mobile Launcher-1 (ML-1) while at Pad 39B for fit checks last September. A more exhaustive set of water flow tests are planned early in the ML’s Summer-long stay at the pad. Early water flows will help determine if any adjustments need to be made to fine tune the system configuration.)

The booster stacking exercise will use test hardware similar to booster stacking practice that has occurred in the past in VAB High Bay 4. With the ML complete, technicians can practice lifting inert aft segments onto the ML’s Vehicle Support Posts and run through stacking a center segment on top.

Certifications will cover all the development work. “Certifications meaning where each and every subsystem will show their paperwork essentially,” Lanham explained.

“Showing where they tested, showing their data packages, and saying we’ve met our requirements and we’re ready to go. That gets bought off and then we’ll transition the system over to operations and they’ll begin operations and maintenance, so that kind of work will continue on the Mobile Launcher that’s got to occur periodically or however they have it laid out.”

“But the big phase will finish testing and then get into the whole certification process,” he added. “I’m the project manager for the Mobile Launcher for development, so I take it all the way through certification and then again it transitions over to operations and then they’ll give me something else to go do.”

Lead image credit: NASA/Cory Huston.

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