NASA’s Space Launch System’s first lunar rocket rolled out to its launch pad early Monday at Kennedy Space Center for another attempt later this month to fully load it with super-cold boosters, the culmination of a repeat of the countdown that officials aim to complete before moving forward with launch later this summer.
The towering 322-foot-tall (98-meter) rocket began its journey at 12:15 a.m. EDT (0415 GMT) Monday with the first move out of High Bay 3 inside the Vehicle Assembly Building, Kennedy’s iconic hangar originally built to stack and service Saturn 5 moon rockets during the Apollo program.
The SLS moon rocket and its mobile launch platform traveled to Pad 39B on a diesel-powered crawler transporter. The 4.2 mile (6.8 kilometer) journey took about 10.5 hours. The lowering of the moon rocket platform onto the launch pad support poles marked the official conclusion of the journey at 10:47 a.m. EDT (2:47 p.m. GMT), according to a NASA spokesperson.
The full stack weighed approximately 21.4 million pounds for deployment.
The massive rocket is the largest ever built by NASA and is the centerpiece of the agency’s Artemis lunar program, which aims to return astronauts to the lunar surface later this decade. NASA is preparing the first SLS lunar rocket for the Artemis 1 test flight, a demonstration mission to send an unmanned Orion crew capsule around the moon and back to Earth on a shakedown cruise before it don’t fly with people.
In preparation for the launch of Artemis 1, NASA teams at Kennedy stacked the SLS moon rocket and rolled the launcher on pad 39B for the first time on March 18 before a “wetsuit rehearsal” to test procedures countdown and fully load the rocket with over 750,000 gallons of super cold liquid hydrogen and liquid oxygen propellants.
But a series of technical problems prevented the NASA launch team from completing the countdown repeat in April.
A ground equipment problem at the launch pad delayed the test by a day from April 3, then encountered problems with the launch pad’s nitrogen gas supply. Nitrogen is used to purge the compartments inside the SLS moon rocket.
A refueling attempt on April 4 was halted by concerns about the temperature of liquid oxygen flowing through the rocket’s core stage, then engineers discovered a problem with a helium valve on the SLS upper stage .
The helium valve problem prevented the launch team from pumping propellants into the upper stage during the next refueling attempt. But NASA tried again on April 14 to load cryogenic thrusters into the core stage, but encountered more problems with the nitrogen supply. After temporarily overcoming the nitrogen problem, the launch team detected indications of a hydrogen leak near an umbilical connection at the bottom of the center stage.
NASA officials then decided to send the rocket back to VAB for repair.
The Artemis 1 launch vehicle returned to the hangar on April 26, and technicians inside the large bay tightened the seals on the umbilical connection in hopes of repairing the hydrogen leak. Workers also replaced the stubborn upper stage helium valve, which failed due to rubber debris stuck in the mechanism. NASA said teams inside the VAB also worked to ensure no debris would be a problem for the new valve.
Meanwhile, upgrades to an offsite nitrogen gas plant near Kennedy Space Center were completed to increase system capacity for the SLS moon rocket. The nitrogen plant is operated by Air Liquide.
With troubleshooting behind them, NASA teams returned the Artemis 1 lunar rocket to pad 39B for another countdown dress rehearsal, or WDR, later this month. If all goes as planned, the next attempt to fully load the SLS lunar rocket with propellant is scheduled for June 19.
Before that, space center ground crews will prepare the rocket for the practice countdown. These tasks will include loading the steering, or gimbal, mechanism on the rocket’s two solid-fuel boosters with hydrazine fuel, which powers the hydraulic power units in the booster’s thrust vector control system.
The countdown test will end with a cutoff just inside T-minus 10 seconds, before the rocket’s main four-stage engines fire.
If the launch team is able to accomplish the WDR, NASA will return the space launch system to the assembly building for final fences and testing. NASA will once again transport the rocket to Pad 39B for the actual launch campaign, currently scheduled for August at the earliest.
The agency does not set an official launch date until it successfully completes the WDR.
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