NASA’s powerful new Space Launch System moon rocket was transported from its launch pad back to the Vehicle Assembly Building at Kennedy Space Center for final repairs, testing and finalization on Saturday, and was nearing launch later this summer after being launched last month had completed a refueling demonstration.
The 98-meter-tall moon rocket rolled out of its bases on Pad 39B at 4:12 a.m. (0812 GMT) on Saturday, about five hours behind schedule to allow time for additional inspections. A diesel-powered caterpillar transport carried the Space Launch System rocket down the ramp and along the stone-covered caterpillar track on the 6.8-kilometer journey back to the Vehicle Assembly Building.
The launch vehicle rolled into High Bay 3 of the iconic assembly hangar at around 2 p.m. EDT (1800 GMT) and was secured at the VAB about half an hour later.
The return of the SLS moon rocket to the Vehicle Assembly Building brings the Artemis 1 mission one step closer to launch on a test flight around the moon. After a decade of development that has cost more than $20 billion, the Artemis-1 mission will mark the first flight of the giant SLS lunar rocket, sending an Orion crew capsule on course to orbit the moon .
The test flight will not carry astronauts but will be the first launch of a manned rocket and spacecraft to the moon since the Apollo program. If the Artemis-1 flight goes according to plan, for the next SLS/Orion mission — Artemis 2 — NASA intends to carry a crew from about 2024 on a loop around the far side of the moon and back to Earth, carrying the first astronauts to mark voyage to the moon since 1972.
Future Artemis missions will include a commercial crew lander to ferry astronauts between the Orion spacecraft in lunar orbit and the lunar surface.
NASA’s launch team fully loaded the lunar rocket with cryogenic liquid hydrogen and liquid oxygen during an exercise countdown on June 20, completing a key test objective that managers wanted to complete before moving on to final launch preparations.
A series of April training countdown runs were plagued by technical problems that prevented the rocket from being fully refueled.
The Countdown rehearsal on June 20th was not without problems. Engineers discovered a hydrogen leak in a quick-disconnect fitting near the bottom of the rocket’s core stage, in a line that dumps excess hydrogen from the system overboard to thermally condition the four RS-25 main engines for ignition.
The launch team overcame the problem and continued the countdown to T-minus 29 seconds, about 20 seconds ahead of the time the engineers wanted to achieve in the dress rehearsal. One of the final test targets, not met on June 20, was a hot fire from hydraulic pumps that power the steering mechanisms of the rocket’s two solid-fuel boosters, which provide 80% of steering control for the first two minutes of launch.
NASA ground crews successfully activated the hydraulic power packs during a separate test on June 25, paving the way for crews to prepare the rocket for rollback to the Vehicle Assembly Building.
The return to the rocket hangar was supposed to begin late Thursday, but NASA delayed the move by a day to complete work on the slope of the caterpillar path leading to the launch pad. The teams finished grating or screening the caterpillar track with heavy equipment before continuing the rollback Friday night.
The crawler reached a top speed of nearly 1 mph during the return trip to the VAB. The combined stack of the SLS moon rocket, its mobile launch platform and the tracked vehicle weighs approximately 21.4 million pounds.
The NASA ground team stopped the crawler and SLS moon rocket just outside the VAB around noon Saturday to allow time for the crew access arm on the mobile launch vehicle tower to position itself next to the Orion crew capsule on the vehicle .
The access arm retracts while moving against the mobile launcher tower and cannot be extended once the missile is in the assembly building.
Arm outstretched, the crawler continued to move through High Bay 3’s vertical door. The transporter’s lift and leveling system lowered the mobile launch platform onto pedestals inside the VAB to complete the journey from Pad 39B.
The space agency hasn’t set an official launch date for the first SLS lunar rocket, but officials are aiming for the launch vehicle to be ready for launch for the Artemis 1 test flight in late August or early September, when the moon, sun and Earth align will allow the mission to achieve all of its objectives.
A launch period starts on August 23rd and runs until September 6th. NASA has one more launch period available from September 19 through October 4, followed by three more two-week launch periods through the end of the year. Depending on when the Artemis-1 mission launches, the Orion test flight could last around 26 days or even 42 days. Mission duration depends on the Moon’s position relative to Earth, allowing the Orion spacecraft to complete half an orbit or one and a half distant orbits around the Moon.
Launch periods are constrained by a number of considerations, including the position of the Moon in its orbit around Earth, restrictions on how long the Orion spacecraft can fly in the shade without direct sunlight on its solar arrays, and reentry and spray rules. including a request for a daytime return to Earth to assist with salvage operations in the Pacific Ocean.
The launch windows for Aug. 23-Sept. 6 windows are given below. August 30th, August 31st and September 1st are not viable launch dates as not all launch window restrictions are met for those days.
Once the rocket is back in the assembly building, workers will deploy 10 sets of access platforms to reach different levels of the launch vehicle and set up an access stand to reach the leaking hydrogen line.
Aside from work already planned to prepare the rocket for launch, technicians will repair the leaking hydrogen connector discovered during last month’s refueling demonstration. Workers will replace Teflon seals on quick-disconnect fittings in the tail service mast umbilical, the connection that routes cryogenic propellant between the mobile launch platform and the SLS core stage.
Officials believe one of those seals came loose in the 4-inch quick connector that leaked during the June 20 countdown rehearsal. Phil Weber, an integration manager on the Artemis ground operations team, said last week that workers will also likely replace a similar gasket on a larger 8-inch propellant fill and drain line as a preventive measure.
Other work within the VAB includes replacing an avionics box on the SLS upper stage and loading software on the upper stage computer. The ground crew will also stow the final equipment in the Orion spacecraft’s pressurized cabin and install flight batteries on the core stage, boosters and second stage, according to Cliff Lanham, flow director of Artemis 1 in NASA’s Kennedy ground operations team.
“Then ultimately we want to do our tests of the flight termination system, and once that’s complete we can do our final inspections on all parts of the vehicle and do our closeouts,” Lanham said in a June 24 press briefing.
The flight abort system consists of pyrotechnic charges on the missile that are fired to destroy the vehicle if it veers off course and threatens populated areas.
Ground crew at the VAB will arm the flight abort system and conduct an end-to-end test to demonstrate the Space Force Range Safety Team’s ability to send a command to destroy the SLS moon rocket. The flight termination system is only certified for 20 days after the test is completed, and the missile would need to be returned to the VAB to re-validate the destruction mechanisms.
According to Lanham, work on the SLS moon rocket in the Vehicle Assembly Building will take about six to eight weeks.
Weber said the ground crew will “hurry” to roll the missile back to Pad 39B after checking the flight termination system. The missile must spend 10 to 14 days on the pad before the first launch attempt, and the timeline currently shows the Artemis-1 team could make three launch attempts before the 20-day flight abort system certification clock expires.
NASA officials are expected to set a launch date as early as next week.
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