NASA’s Space Launch System on launch pad 39B. Credit: NASA/Kim Shiflett
NASA commenced a two-day countdown dress rehearsal for the agency’s huge Space Launch System moon rocket Friday, with clocks ticking down to a critical milestone Sunday, when the heavy-lifter will be fueled and pressurized on the launch pad for the first time.
But much of the test will happen without independent press coverage. NASA plans to provide sanctioned updates on the two-day dress rehearsal via the agency’s website and social media accounts, but news media representatives are not being permitted to listen to the countdown activities.
NASA has cited security and export control restrictions for the move. Numerous media representatives requested access to the SLS countdown audio for the wet dress rehearsal. Launch countdown audio feeds for other U.S. rockets, including those developed by private companies and hauling sensitive U.S. military satellites into orbit, are widely available to the news media and the public.
The two-day countdown began at 5 p.m. EDT (2100 GMT) Friday with countdown clocks at Kennedy Space Center starting at T-minus 43 hours, 40 minutes. The test will culminate with a simulated cutoff of the countdown at T-minus 9.34 seconds Sunday afternoon, just before the rocket’s four RS-25 main engines would ignite on launch day.
The countdown test, called a wet dress rehearsal, is a major milestone before NASA proceeds with an attempt to launch the 322-foot-tall (98-meter) Space Launch System on the Artemis 1 mission, the first test flight for the Artemis program to return astronauts to the moon.
“This is our last design verification prior to our launch,” said Tom Whitmeyer, NASA’s deputy associate administrator for exploration systems development. “And it is a test, so I have to note that we could learn something during the test. So we’ll take the data and address the data as we get it.”
The SLS rocket will send an unpiloted Orion crew capsule to the moon, where the ship will maneuver into lunar orbit for tests and demonstrations before returning to Earth several weeks after launch, aiming for a splashdown in the Pacific Ocean off the coast of California.
Artemis 1 is scheduled to launch no earlier than June 6. NASA managers plan to select an official target date for the Artemis 1 launch after the wet dress rehearsal.
The countdown test will help NASA verify the Space Launch System, its mobile launch tower, and launch pad facilities are all ready for the real Artemis 1 countdown.
“There’s thousands of components on the mobile launcher that need to perform,” Whitmeyer told reporters earlier this week.
The rehearsal this weekend will “closely follow” a real launch countdown, said Charlie Blackwell-Thompson, NASA’s Artemis 1 launch director. “There are couple of minor differences, but they are, in fact, minor.”
“Primarily, this is about loading the vehicle, she said. “It is about utilizing the ground support equipment, the commodities out at Launch Complex 39B, along with the command and control system here in the LCC (launch control center), getting through those (propellant) loading operations, and then getting into the terminal portion of the count.”
The launch team has accomplished multiple countdown simulations and a countdown sequencing test with the SLS when it was unfueled inside the Vehicle Assembly Building at Kennedy. And the core stage was filled with cryogenic fuel during ground testing at NASA’s Stennis Space Center in Mississippi.
But the dress rehearsal is the first time the fully-stacked rocket will be loaded with propellant.
“This is first time that we’ve done it in this particular configuration, so there is definitely an opportunity to learn some things, and and certainly as we do, we’ll incorporate them into our preparations and planning for launch,” Blackwell-Thompson said.
This graphic shows the Space Launch System’s major components. Credit: NASA
Over the course of the weekend, engineers, technicians, and mission managers at Kennedy and other support locations across the United States will run through their procedures just as they would on launch day.
The water tank at launch pad 39B, which provides water for the facility’s sound suppression system, will be filled as it would in a real countdown. The Orion spacecraft and SLS computers will be powered up, and technicians will move flame deflectors into place at pad 39B, even though no engines will ignite during the test.
The Space Launch System’s upper stage, derived from United Launch Alliance’s Delta 4 rocket, will be powered up early Sunday, and pad 39B will be cleared of all personnel.
The countdown will hold for 90 minutes early Sunday, allowing teams inside the launch control center at Kennedy to make sure everything is ready to begin loading super-cold liquid hydrogen and liquid oxygen into the rocket’s propellant tanks.
That propellant loading should begin shortly after 7 a.m. EDT (1100 GMT) for the giant Boeing-built core stage, covered in orange foam insulation to prevent ice build-up on the rocket’s outer skin.
Liquid oxygen, chilled to minus 297 degrees Fahrenheit (minus 183 degrees Celsius) will begin loading first into the core stage. Then liquid hydrogen, stored at minus 423 degrees Fahrenheit (minus 253 degrees Celsius), will start pumping into the rocket’s main stage at pad 39B.
It will take about three hours to load liquid oxygen into the core stage, and an hour-and-a-half for liquid hydrogen. In flight, the propellants will feed the rocket’s four RS-25 main engines, leftovers from the space shuttle program, for a burn lasting more than eight minutes.
Then the launch team will move on to loading hydrogen and oxygen into the rocket’s cryogenic upper stage, powered by a single Aerojet Rocketdyne RL10 engine. Here’s a breakdown of the propellants that will be loaded into the rocket Sunday:
• Core Stage liquid oxygen: 196,000 gallons
• Core Stage liquid hydrogen: 537,000 gallons
• Upper stage liquid oxygen: 5,000 gallons
• Upper stage liquid hydrogen: 17,000 gallons
Another 30-minute build-in hold is planned when the countdown reaches the T-minus 10 minute mark Sunday afternoon. After a final “go/no go” pre-launch readiness poll, NASA launch director Charlie Blackwell-Thompson will give approval for the countdown clock to resume.
If all goes according to plan, the countdown will target a simulated launch time of 2:40 p.m. EDT (1840 GMT) Sunday. In the final 10 minutes of the countdown, the core stage and upper stage propellant tanks will be brought to flight pressure, the boosters will be armed, and the rocket will be switched to internal power.
The countdown will cut off at T-minus 33 minutes and recycle to the T-minus 10 minute hold. NASA’s launch team plans a second run through the terminal countdown later Sunday afternoon, culminating in a hold at T-minus 9.34 seconds, just prior to ignition of the main engines.
Then the core stage and upper stage will be drained of cryogenic propellants, and NASA engineers will evaluate the rocket’s performance during the dress rehearsal.
NASA withholds coverage of SLS countdown dress rehearsal
NASA plans to release only text updates through the weekend. NASA TV will not be airing any live commentary for the final hours of the practice countdown. The agency’s television channel has previously provided live coverage of similar events, such as space shuttle tanking tests.
Whitmeyer, whose responsibilities include overseeing the SLS and Orion programs, said NASA is restricting access to the countdown audio loops due to “export control” concerns. He said NASA is being “super sensitive” and “cautious.”
“Export controls are a significant consideration for our program,” Whitmeyer said. “It’s the first flight of the rocket. Typically, what they’re looking for is timing and sequencing data, flow rates, temperatures, how long it takes to do certain tasks. That’s considered to be important information by other countries. So we have to be very careful data when we share data, particularly for the first time.”
NASA’s Space Launch System on pad 39B ahead of the Artemis 1 Wet Dress Rehearsal. Credit: NASA/Kim Shiflett
NASA provided regular access to launch control team audio for space shuttle countdowns. Whitmeyer said NASA had worked through details on what information could be released during shuttle countdown operations, but hasn’t done so for the Space Launch System.
“As we work through this wet dress rehearsal, we’re actually going to talk to the export control people and share with them what we think is acceptable data, and then they’re going to verify that it is acceptable data, and we hope that, by the time we get to the launch, we’ll have a really good understanding,” Whitmeyer said.
Some of the most suitable analogs to the SLS dress rehearsal were the space shuttle’s flight readiness firings at Kennedy, and a pair of space shuttle tanking tests in 2005 that stopped short of engine ignition. NASA TV provided hours of live coverage for those events.
The low-key coverage of the Artemis 1 countdown rehearsal comes on the verge of the first test flight of the Space Launch System and a public relations offensive to build excitement about humans returning to the moon. NASA has spent more than $20 billion developing the Space Launch System over the past decade.
NASA’s inspector general reported last year that the agency had, at the time, committed more than $19 billion developing the Orion spacecraft over the last 15 years. Another $4.8 billion since 2012 went toward readying Kennedy Space Center’s ground infrastructure for SLS and Orion missions.
Kathryn Hambleton, a NASA spokesperson, said the agency’s public affairs team has had “ongoing discussions” with export control officials for months “to determine what technical audio we will be able to share publicly during launch or otherwise, including related media requests for coverage of WDR (wet dress rehearsal).”
“Given the concerns about the potential for detailed technical discussions on the command channel, the teams determined wet dress rehearsal would be the best opportunity to demonstrate how we would use the audio channels, at which milestones, and while protecting controlled information in order to facilitate approval for use during launch,” Hambleton said.
“I do apologize on behalf of the agency,” Whitmeyer said.
NASA is providing a continuous video feed of the SLS on pad 39B over the weekend. Spaceflight Now is providing a similar video stream, and will provide commentary Sunday as NASA releases text updates.
Spaceflight Now’s request for additional video views was denied by NASA.
Meanwhile, NASA’s communications team at Kennedy will be using the countdown audio channel and launch pad camera views for a rehearsal of their own Sunday, practicing for the agency’s live broadcast of the Artemis 1 launch.
NASA’s launch commentator team will be participating in the broadcast rehearsal — with a full production involving two TV stages — and presumably will be unable to provide public commentary on the test itself.
Artemis countdown test paves the way for final launch preparations
The Space Launch System was built up inside the iconic Vehicle Assembly Building at Kennedy over the last year. NASA rolled the rocket out of the assembly building for the first time March 17, and the rocket reached pad 39B before dawn March 18 to begin preparations for the wet dress rehearsal.
Technicians connected the SLS mobile launch platform with the launch pad’s data, power, purge, and propellant lines, then began validation tests to ensure the connections are good. That was followed by communications testing at the launch pad, and tests to characterize the electromagnetic environment with the rocket at the pad.
An astronaut on the International Space Station took this picture March 30 of the Kennedy Space Center, showing pad 39B at lower right, pad 39A just above it, and the Vehicle Assembly Building. North is down in this photo. Credit: NASA
Crews then loaded 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. The power units will be activated and the booster nozzles will go through a steering test profile in the final seconds of the dress rehearsal.
Once the rocket is drained of propellant, NASA teams will prepare the Space Launch System to roll back to the VAB around April 11, assuming the dress rehearsal goes smoothly.
With the rocket back inside the VAB, crews will inspect the vehicle and perform additional testing, primarily with the SLS flight termination system, the destruct charges that would blow up the rocket if it flew off course after liftoff.
Then NASA plans to transfer the Space Launch System back to pad 39B around one week before the Artemis 1 target launch date, with final launch preps closely mirroring much of the work teams have accomplished getting ready for the countdown dress rehearsal.
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