A moment more than a decade in the making. NASA’s Space Launch System (SLS) rocket for the Artemis 1 mission made its first trip down the crawlerway at the Kennedy Space Center in Florida on Thursday evening, March 17.
Rollout first motion happened just before 6:00 pm EDT (22:00 UTC) for a planned 11-hour journey to LC-39B. But when SLS arrived at the pad Friday morning, it found a completely different, rebuilt launch complex from the previous vehicles that called it home.
The rollout marked a significant milestone for NASA’s new Moon rocket that will help ferry astronauts to lunar vicinity where they will then — for Artemis 3 — transfer to a waiting SpaceX Starship lunar lander for humanity’s planned return to the Moon later this decade.
Orion and SLS are also NASA’s crew launch vehicles for missions to the upcoming Lunar Gateway station.
The rollout to Pad B brought the 98.1 m (322 ft) tall rocket the 6.7 km (4.2 miles) from Vehicle Assembly Building (VAB) High Bay 3 (HB-3) to the pad for a series of pad connections, systems checkouts, and rocket integration work that will all lead to a full-up practice countdown complete with fueling and a countdown cutoff (stopping point) at just under the T-10 second mark.
But SLS found a very different launch pad when it arrived than the one used by the final Shuttles and Ares I-X, the last rocket to launch from the pad in October 2009.
Deeply rooted in history, Kennedy Space Center’s Launch Complex 39B has been home to many transitions — but none as major as the one for SLS. Once built to support the Saturn V and Apollo program, it transitioned to support the Space Shuttle in the late-70s and early- to mid-80s, then a lasting change in the lightning towers for the now-canceled Constellation program, and now today, where it will once again support another Moon shot with the SLS and the upcoming Artemis program.
Construction of 39B began in December 1964 and was completed nearly four years later in April 1967. While Launch Complex 39 A and B are near-identical builds, the only major difference between them is that Pad B sits 2.1 meters (7 feet) higher at 16.7 m (55 feet) above mean sea level.
The pad hosted a single human lunar orbit mission with Apollo 10 and Stafford, Young, and Cernan. It would be the first and only Saturn V mission launched from 39B when it lifted off on the program’s everything-but-land rehearsal for the first Moon landing.
While 39A would support all of the human Moon landing missions, 39B would host the three crewed Skylab missions as well as the final launch of the Apollo program: the Apollo-Soyuz Test Project mission in July of 1975.
Artemis, the sister of Apollo on the move to Launch Complex 39 B
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The clean pad was then abolished for the Shuttle Program, with a Fixed and Rotating Service Structure supporting Shuttle pad operations and fueling needs. The pad also received hypergolic fuel and oxidizer lines as well as helium and nitrogen service lines.
Other significant modifications included the addition of an 88.3 m (290 foot) tall water tower to support the Sound Suppression System. Located on the northeast side of the pad, this 300,000-gallon tank would release at T-16 seconds, with a peak flow rate of 900,000 gallons per minute.
A hydrogen flare stack was also added to the pad for the Shuttle era, even though the Saturn V before it had also used liquid hydrogen as a propellant. For Apollo, a hydrogen burn pond was used to eliminate this highly flammable fuel source.
But truly significant changes, a rebuild, was not possible until the Shuttle program ended and NASA could get into the pad — which still had most of its 1960s technology — and truly rebuild and modernize it.
The SLS Block 1 Mobile Launcher at Pad B for testing. The water tower can be seen between the ML and a taller lightning protection system tower. (Credit: NASA)
“The pad was built in the 60s, and since it was built, because of the amount of launches that we had in the Shuttle timeframe where the pad was basically operational seven days a week, 24 hours a day, there was little time to go and do refurbishment or upgrades to the pad,” said Jose Osvaldo Perez Morales, Senior Project Manager, Exploration Ground Systems about the changes to the pad and preparations to support SLS in an interview with NASASpaceflight.
Teams finally had a chance to truly rebuild Pad B and make it a 21st-century pad.
“When I got the pad, first thing I had to do, obviously the cables that were serving Apollo and Shuttle were cables from the 1960s. The cables, the core was a big piece of copper.”
“And we decided to take every piece of cable out of the pad. We removed about 1.3 million feet of cable. Of which, at the time, I was fortunate enough to recycle that and buy all the fiber optic that I needed to install in the pad.”
In all, the 1.3 million feet of copper cable was replaced with just 300,000 feet of fiber optic cable.
“So we basically brought the pad to the 21st-century era, where now we are going to send messages through fiber instead of copper. And below the pad’s surface, there’s a big room called the PTCR [Pad Terminal Connection Room]. And that’s where all the electronics reside for launches.”
“This is where all the systems that talk to all the valves and the different things that move the pad reside. Well, all that was taken out. We replaced that, obviously, with completely new electronics, with PLC [Programmable Logic Controllers]-type controls,” said Mr. Morales.
“Back when I got to the pad, there were three or four rooms, I mean wall-to-wall, full of racks and electronics because obviously they were of the 1960s era. Now, you go into the same room and you find three or four racks and the room almost empty because you’ve got state-of-the-art PLCs that do the work of maybe 20 racks back in the Shuttle era.”
Outside at the pad, the sound suppression system and flame trench were also completely reworked for SLS.
“We did a tremendous amount of modifications to the ignition overpressure and sound suppression system to conform to the new vehicle,” said Morales. “Those pipes had been there since the 60s, and we brought them up. We basically modified the way the new mobile launcher was being fed from those pipes.”
The Core Stage for Artemis 1 during its arrival at the Kennedy Space Center in April 2021 with Pad-B behind it. (Credit: Nathan Barker for NSF)
Teams also refurbished the water tower, something that had never taken place before, and added numerous valves and systems for the dynamics the system will have to withstand for SLS.
In the flame trench, all of the bricks from Apollo and Shuttle were removed and the pad structure inspected and refurbished before 96,000 new bricks were installed.
The trench’s flame deflector was also completely reworked. In the Shuttle era, the deflector was lined with Fondu Fyre material and had to be refurbished between launches.
“We took an idea of a flame deflector that they use in Guiana,” said Morales. “In Guiana, instead of using Fondu Fyre or any cement type area, what they have is steel plate lining, like shingles on the roof of your house. That’s exactly what we’ve got now with this new flame deflector. It’s about one inch, one and a half inch plates lining all the flame deflector.”
“It can take a lot more launches before you have to do any repairs, and it requires a lot less maintenance,” noted Morales.
But a striking new addition to the pad from Apollo and Shuttle are three 600 foot lightning towers.
“One of the first projects at the pad was to protect the vehicle from lightning strikes. The first concept had four towers, and we had this doctor from Venezuela who was an expert in lightning. And [there was a] theory … called the Rolling Ball. And he did all kinds of models and basically came up with these three towers.”
There really are no words to describe having SLS roll down the crawlerway right in front of you.
Speechless
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This theory proposed that with a three-tower design with nine conductors to the ground, the odds of having lightning strike any place in the area and not the towers was 1 in 10,000 years, according to Mr. Morales. “And throughout the years since 2011, we have never had a lightning strike go and basically hit the inside of the pad.”
As part of the three-tower design, highspeed cameras were placed on the towers looking at the fiberglass lightning mast where lightning will strike.
“We put some very high-speed cameras right before the fiberglass mast. Then we put a bunch of sensors around the perimeter of the pad. Every time the potential energy from the air and the ground comes to a point, it triggers the camera, saying, ‘Hey, there’s a possibility of lightning close by.’ And the cameras capture everything.”
But the lightning protection towers at 39B also sport another upgrade that has never before been present: weather stations.
The SRB for SLS connected to the Core Stage. (Credit: Stephen Marr for NSF)
“Each lightning tower has four levels. Each level has a complete weather station. The closest weather station that the Launch Director had at the time during Shuttle, it’s about five miles away from the pad.”
“So they would have to make decisions on launch based on a weather station that was about five miles away from the pad. Now, they’re going to have these three towers, and each tower has four weather stations.”
“So you’re going to have 12 weather stations all around your vehicle to basically understand what the exact conditions are for weather and make a decision if you can launch or not in a heartbeat.”
While SLS won’t need launch weather information for this trip to the pad, the weather stations will be critical for the multiple weeks of outdoor work and tests the vehicle will undergo for its Wet Dress Rehearsal campaign.
Of note, the electrical potential monitors will also play a key role in determining if the ground weather is acceptable to fuel the rocket and when work will have to stop at the pad for worker safety.
The crawler transporter arrives at LC-39B with the SLS ML for pad testing in 2019. (Credit: Stephen Marr for NSF)
Presently, the Wet Dress Rehearsal is scheduled for April 3. This will involve a full fueling of the Core Stage — built by Boeing — and the Interim Cryogenic Propulsion Stage — built by United Launch Alliance — with liquid oxygen and liquid hydrogen and will give the Launch Team their first opportunity to take the vehicle through a near-full countdown.
After this, SLS will return to the VAB for final launch preparations before moving back to LC-39B for launch.
The currently No Earlier Than launch date for Artemis 1 is June 2022, with a formal target to be announced once the Wet Dress Rehearsal is complete.
(Lead image: SLS moving to the pad. Credit: Thomas Burghardrt for NSF)