NASA says the first rollout of the Space Launch System moon rocket is planned for March ahead of a key fueling test on a seaside launch pad at Kennedy Space Center, a delay of several weeks to allow more time for work inside the Vehicle Assembly Building.

The 322-foot-tall (98-meter) SLS rocket was supposed to roll out of the Vehicle Assembly Building on Feb. 15. That’s now expected to happen next month, beginning several weeks of testing on the launch pad, culminating in a mock countdown in which the rocket will be filled with cryogenic propellants.

The delay in the rocket’s first rollout to pad 39B at Kennedy will push back its launch on a test flight around the moon from March until no earlier than April. NASA officials said they are also evaluating launch opportunities in May.

The mission, called Artemis 1, will send the Orion spacecraft to the moon, where it will enter a distant orbit in a multi-week, unpiloted “shakedown cruise” to demonstrate the SLS rocket and Orion are ready to carry astronauts. The next mission, known as Artemis 2, will send a crew of four around the moon and back to Earth, paving the way for future lunar landing flights.

Tom Whitmeyer, NASA’s deputy associate administrator for exploration systems development, said Wednesday there is “no one specific thing” that caused officials to delay the first rollout of the huge moon rocket from the Vehicle Assembly Building.

The activities inside the VAB include final outfitting of the rocket, adding and testing instrumentation to measure the rocket’s performance before and during launch, and installing the flight termination system, a set of pyrotechnic charges that would destroy the launch vehicle if it veered off course.

“I like to think of if you had a work being done on your kitchen, and you were down to a punch list,” Whitmeyer said. “We’re basically down to a punch list of things that we need to complete. It can be something as simple as a scratch that needs to be polished out or some paint that needs to be fixed. There’s just a lot of that. It’s a really big vehicle.”

Technicians are also installing thermal blankets around the rocket’s four RS-25 main engines, leftovers from the space shuttle program. Before rolling out of the VAB on its mobile launch platform, ground crews will remove scaffolding needed to access parts of the engine section, Orion spacecraft, and other sections of the rocket.

We’re taking it one step at a time,” said Mark Bolger, head of NASA’s exploration ground systems team at Kennedy Space Center. “We’re doing it very meticulously, and we’re proud of the progress that we’ve made.”

The Space Launch System has been fully stacked inside High Bay 3 of the Vehicle Assembly Building since October, when the Orion spacecraft was raised on top of the rocket’s upper stage. The addition of the Orion spacecraft followed stacking of the rocket’s solid-fueled boosters and core stage earlier in 2021.

Four RS-25 main engines at the bottom of the Space Launch System’s core stage. Credit: NASA/Corey Huston

Late last year, ground teams at Kennedy completed a series of component power-ups and testing to ensure all the elements of the vehicle can properly communicate and function with each other. They also accomplished an end-to-end communications test of the SLS and Orion spacecraft involving NASA’s network of deep space tracking stations around the world.

The SLS launch team, working out of a newly-modernized firing room inside Kennedy’s Apollo-era Launch Control Center, conducted two countdown sequencing tests in December and January.

Using the real rocket and Orion spacecraft inside the VAB, the countdown simulations demonstrated the performance of the SLS ground launch sequencer, which managers the countdown until a handoff to the rocket and spacecraft’s on-board computers at about T-minus 30 seconds.

The first test in December was largely successful but was cut off a few seconds before the handoff. Another sequencing test Jan. 24 ran the full planned duration, setting up the SLS launch team and ground software for their next big test with the wet dress rehearsal, which will run a full countdown until T-minus 10 seconds, moments before ignition of the rocket’s four RS-25 main engines.

In preparation for the wet dress rehearsal, or fueling test, the Space Launch System will ride an Apollo-era crawler transporter along a pathway first engineered in the 1960s for movements of NASA’s Saturn 5 moon rocket. Sources said the rollout is currently scheduled around March 8. It was previously planned for Feb. 15.

After servicing and checks on the launch pad, NASA’s ground team will load super-cold liquid hydrogen and liquid oxygen into the rocket’s core stage and upper stage during a simulated countdown. After the dress rehearsal, the rocket will roll back to the VAB for closeouts and final pyrotechnic ordnance connections, then return to pad 39B six days before the target launch date.

NASA officials said the earliest the Artemis 1 test flight could take off is during a 15-day launch period opening April 8 and closing April 23. The space agency also has launch periods from May 7 through May 21, and June 6 through 16.

The launch periods are driven by the locations of the Earth and the moon, and NASA’s requirement for the Orion spacecraft to splash down in the Pacific Ocean during daylight hours at the end of its mission, expected to last several weeks. The exact mission duration will depend on when in each launch period Artemis 1 leaves Earth.

One reason the Artemis 1 mission missed launching in the February or March windows was a failure in a computer that controls one of the rocket’s RS-25 main engines. The computer has two redundant operating channels, and the backup channel failed to power up consistently during testing in November.

Crews inside the VAB swapped out the engine control computer, made by Honeywell, in December. The new engine controller is working normally, according to NASA.

Engineers believe they have isolated the cause of the problem with the engine controller, Whitmeyer said. He did not identify the suspected cause, but said engineers were able to replicate the problem during troubleshooting, and it’s not a constraint to beginning the SLS wet dress rehearsal. He said NASA will provide a public update on the issue in the coming weeks, once more testing is completed.

Whitmeyer said the COVID pandemic and industry-wide supply chain issues have caused “logistical challenges” and problems with “parts availability” on the Artemis program.

A large number of COVID cases during the surges of the delta and omicron variants of the virus slowed some of the work inside the VAB, Bolger said.

“Where it hurts is when it affects our touch labor workforce in the high bay,” Bolger said, adding that the situation has improved in recent weeks with a decline in cases and a return to full workforce numbers.

The chief near-term aim of the Artemis program is to land astronauts on the moon, including the first woman and person of color to explore the lunar surface. Humans haven’t visited the moon since the Apollo 17 mission in 1972. Eventually, NASA wants to establish outposts in lunar orbit and on the moon’s surface to pave the way for future expeditions to Mars.

The SLS test flight is a milestone in a decade-long 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. At that time, NASA officials hoped to launch the first SLS test flight in 2017, but the mission is now running more than four years late.

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.

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 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.

NASA’s inspector general said last April 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.

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