NASA is set to roll the Space Launch System, a heavy-duty rocket designed to send astronauts to the moon, out of the iconic Vehicle Assembly Building at the Kennedy Space Center on Thursday evening. A crawler-transporter originally built more than 50 years ago for the Apollo program will haul the towering rocket to its launch pad for a countdown dress rehearsal.
The rollout from High Bay 3 in the Vehicle Assembly Building began around 5:47 p.m. EDT (2157 GMT) Thursday. The Space Launch System, crowned with NASA’s Orion crew capsule and the ship’s pointy-shaped abort motor, is riding atop its purpose-built launch platform, called the Mobile Launcher.
Ground crews moved Crawler-Transporter 2, or CT-2, under the Mobile Launcher earlier this week to prepare for the roll to pad 39B, one of two NASA-owned seaside launch pads constructed in the 1960s.
The SLS and Orion spacecraft are heading to pad 39B for a countdown dress rehearsal in early April, when the launch team will load super-cold liquid hydrogen and liquid oxygen propellants into the rocket’s Boeing-built core stage and upper stage, made by United Launch Alliance.
If the test goes well, NASA will return the rocket to the VAB later next month for additional launch preparations, then roll the SLS back to pad 39B for launch on the Artemis 1 mission, the first test flight of NASA’s program to return astronauts to the moon for the first time since 1972.
Artemis 1 will not carry astronauts, but the mission will verify the rocket and Orion spacecraft are ready to carry a four-person team on a looping trajectory around the moon on the Artemis 2 mission, scheduled for launch in 2024.
NASA’s Artemis 3 mission, targeted for no earlier than 2025, will attempt the first landing on the lunar surface. NASA has a contract with SpaceX to build a human-rated lunar lander based on the company’s privately-developed Starship rocket, and the Orion capsule will dock with the Starship lander near the moon, allowing astronauts to float into the SpaceX rocket for the ride to the lunar surface.
The Starship will launch the crew back off the moon to link up with the Orion spacecraft, which will ferry the astronauts back to Earth. The early Artemis missions will lay the groundwork for the assembly of a mini-space station, called the Gateway, in orbit around the moon, and more ambitious expeditions with moon rovers and longer-term living quarters.
“We are in in very good shape and ready to proceed with this roll on Thursday evening,” said Charlie Blackwell-Thompson, NASA’s launch director for the Artemis 1 mission. “It’s going to be just a wonderful, wonderful sight when we see that amazing Artemis vehicle cross the threshold of the VAB, and we see it outside of that building for the very first time.
“I think it’s going to really be breathtaking, and it’ll be something really special for me and everyone that has worked on this and gets an opportunity to see it.”
The Space Launch System will be the first rocket to roll out of the VAB since the space shuttle mission in 2011. With a total thrust at liftoff of 8.8 million force-pounds, it’s the most powerful launcher to emerge from the huge assembly building since the last Saturn 5 rocket was prepared for launch with NASA’s Skylab space station in 1973.
“Rolling out of the VAB, that’s really an iconic moment for this vehicle,” said Tom Whitmeyer, NASA’s associate administrator for exploration systems development. “And to be here for a new generation of a super heavy-lift, exploration-class vehicle, it’s going to be a day to remember.”
The crawler-transporter that will haul the rocket to pad 39B was upgraded to handle the weight of the SLS with its mobile launch platform. The entire stack, including the crawler, mobile launch platform, and the Space Launch System, will weigh around 21.4 million pounds during the 4.2-mile (6.8-kilometer) journey.
The rocket will travel along the rock-covered crawlerway, the same path taken by Saturn 5 moon rockets and space shuttles.
Once outside of the VAB, the crawler will pause to allow the crew access arm on the mobile launch tower to retract away from the Orion spacecraft. The rollout will then resume to move farther from the VAB, before another planned stop to gather data on the entire stack’s response to the deceleration. The data will help inform models on the structural stiffness of the stack.
Then the crawler will start moving again, reaching a top speed of 0.8 mph for the rest of the trip to pad 39B.
NASA’s two crawlers were built in the 1960s by Marion Power Shovel Company of Ohio. Over the last decade, Crawler-Transporter 2, which has logged 2,335 miles (3,758 kilometers) in its lifetime, was outfitted with new diesel engines and power generators made by Cummins, and modified to support the heavier load of the SLS.
Technicians also replaced roller assemblies and bearings with hardware designed for a greater load capacity. Other upgrades included a new lubrication system, new jacking and leveling cylinders, a new driver control and monitoring system, new brakes, and reconditioning of the crawler’s gear cases and gears, according to NASA.
The modifications are intended to extend the service life of the crawler by 20 years.
“While the original crawler was over 50 years ago, we have done significant upgrades in preparation for rolling this vehicle to the pad and for Artemis operations,” Blackwell-Thompson said.
Once the rocket is on pad 39B, ground teams at Kennedy will spend about two weeks preparing for the SLS countdown dress rehearsal. The two-day simulated countdown is scheduled to begin April 1, culminating in the loading of liquid hydrogen and liquid oxygen on Sunday, April 3.
“We only have about five or six things we have to do, but of course those five or six things are fairly complicated,” Blackwell-Thompson said.
Technicians will connect the mobile launch platform with the launch pad’s data, power, purge, and propellant lines, then begin validation tests to ensure the connections are good. That will be followed by communications testing at the launch pad, and tests to characterize the electromagnetic environment with the rocket at the pad.
Crews will load hydrazine into the the hydraulic power units on each of the two side-mounted solid rocket boosters. The boosters, built by Northrop Grumman, are extended versions of the boosters that flew on the space shuttle, and they reuse rocket motor casings left over after the shuttle retired.
The booster hydraulics power the thrust vector control steering system at the base of each booster.
During the countdown dress rehearsal itself, currently set for April 3, the countdown clock will stop at about T-minus 10 seconds, just before the four RS-25 main engines would ignite on the crew stage.
Then the launch team will drain the rocket of liquid propellants and prepare the rocket to roll back to the VAB around April 11, assuming the dress rehearsal goes smoothly.
The rocket’s return to the VAB will set the stage for final work on the vehicle’s range safety destruct system, which would be used to destroy the rocket if it veered off course after liftoff. After other closeouts and tests, the rocket will return to pad 39B for the Artemis 1 launch countdown.
The launch is currently scheduled for no earlier than May, but could be delayed to later launch windows in June or July. The mission has a two-week launch period from May 7 through May 21, then another launch period opens June 6 and runs until June 16.
The SLS test flight is a milestone in a 10-year development that started in 2011, when Congress ordered NASA to design and build a gigantic rocket using technology left over from the agency’s retired fleet of space shuttles. NASA awarded Lockheed Martin the contract to develop the Orion spacecraft in 2006 under the umbrella of the agency’s Constellation moon program, which was canceled in 2010.
The rocket will launch the Orion spacecraft on a multi-week demonstration mission. The capsule will enter a distant retrograde orbit that moves in the opposite direction of the moon’s rotation, allowing NASA mission controllers at the Johnson Space Center in Houston to check out the craft’s performance before the agency commits astronauts to fly on the Artemis 2 mission.
The exact duration of the Artemis 1 mission depends on when the launch occurs in the month-long lunar cycle. The Orion capsule will return to a parachute-assisted splashdown in the Pacific Ocean off the coast of California.
NASA kept the Orion program alive through two major restructurings of the agency’s deep space exploration efforts, first during the Obama administration, when Congress and the White House agreed to pivot NASA’s focus to a human mission to Mars, with an interim crewed expedition to an asteroid.
The Trump administration shifted NASA’s exploration program back to the moon. NASA dubbed the moon program Artemis, naming it for the twin sister of Apollo in Greek mythology.
Through it all, the Orion program survived. NASA’s inspector general reported last year year that the agency has spent $12.8 billion developing the Orion spacecraft since 2012, plus an additional $6.3 billion committed to the program in the prior decade under the Constellation program.
The Artemis 1 mission will be the second spaceflight of an Orion capsule, and the first mission to fly an Orion spaceship to the moon. It’s the first flight of the Orion spacecraft’s European-built service module, which provides electricity and propulsion for the capsule in deep space.
NASA’s inspector general said last year that the agency has budgeted $18.8 billion for the SLS program since 2012. Another $4.8 billion in the same period went toward readying Kennedy Space Center’s ground infrastructure for SLS and Orion missions.
Email the author.
Follow Stephen Clark on Twitter: @StephenClark1.