NASA’s Space Launch System moon rocket on pad 39B at the Kennedy Space Center on Aug. 30. Credit: NASA/Eric Bordelon
NASA officials said Thursday they hope to try again to launch the Artemis 1 moon rocket from the Kennedy Space Center as soon as Sept. 23 or 27, but that schedule comes with two big caveats: A repair to a leaky liquid hydrogen fueling line must hold tight during a tanking test next weekend, and the Space Force’s Eastern Range has to extend the certification of batteries on the moon rocket’s flight safety system.
The answers to both of those questions were unknown as of Thursday, officials said. Managers briefed reporters on the status of Artemis 1 launch preparations as ground teams at Launch Complex 39B were busy replacing seals on connections where liquid hydrogen flows from the launch platform’s tail service mast umbilical into the core stage of the Artemis 1 moon rocket.
Jim Free, NASA’s associate administrator for exploration systems mission development, said Thursday that the agency has requested Sept. 23 and 27 for launch dates on the Eastern Range. In order to approve those launch dates, the Space Force would need to waive or extend its requirement for re-certification of batteries on the rocket’s range safety destruct mechanism.
While the Space Force evaluates that question, ground crews at Kennedy planned to swap out a seal in a quick disconnect fitting on an 8-inch liquid hydrogen fill and drain line that leaked during a launch attempt Saturday, Sept. 3. The quick disconnect is located at the interface between the launch platform and the Space Launch System rocket, where ground side and flight side umbilical plates meet. NASA is also replacing a seal in a nearby 4-inch liquid hydrogen bleed line as a precautionary measure.
Technicians erected an environmental enclosure around the work area at the tail service mast umbilical, gray housings that stick above the deck of the mobile launch platform to feed liquid hydrogen and liquid oxygen into the rocket. The tent will protect sensitive components in the umbilical area from weather and contamination.
NASA officials said after Saturday’s scrubbed launch attempt that they were considering options to repair the hydrogen leak at the pad or inside the Vehicle Assembly Building, which would require the rocket to roll the 4.2-mile (6.8-kilometer) distance back to the hangar on a diesel-powered crawler-transporter. A benefit of repairing the leak at the pad is that the launch team will be able to confirm the tightness of the umbilical seal under cryogenic conditions.
If technicians can make quick work on the seal replacements, NASA plans a test to load super-cold liquid hydrogen and liquid oxygen into the Space Launch System moon rocket around Sept. 17, next Saturday. The flow of liquid hydrogen, chilled to minus 423 degrees Fahrenheit, through the umbilical line will confirm whether the new seal stopped the leak in the 8-inch fill and drain line.
The shape and size of seals and gaskets can change when exposed to super-cold temperatures, creating a leak path that wasn’t detectable at ambient temperatures. A molecule of liquid hydrogen, created by bonding two hydrogen atoms together, is one of the tiniest known in the universe, and leak through gaps impermeable to other molecules.
The SLS moon rocket’s core stage contains 537,000 gallons of liquid hydrogen fuel and 196,000 gallons of super-cold liquid oxygen as an oxidizer. The same propellants power the SLS upper stage, with much smaller tanks.
Mike Bolger, head of NASA’s exploration ground systems office at Kennedy, said officials plan to fully load propellants into the SLS core stage and upper stage during the Sept. 17 tanking test, but plan to stop short of the terminal countdown sequence. That would allow the launch team to verify other actions during the countdown, including the bleed flow of liquid hydrogen to chill down the core stage’s four main engines for startup, and a pressurization test of the rocket’s core stage fuel tank.
The engine hydrogen bleed line had a leak during a June countdown rehearsal. Technicians fixed the leak, but a sensor measurement during the first Artemis 1 launch attempt Aug. 29 indicated one of the four main engines was not reaching cold enough temperatures during the chilldown procedure. NASA officials determined the measurement came from a bad sensor, and approved another launch attempt Sept. 3 with plans to confirm proper engine temperatures through other data sources.
But the countdown Sept. 3 never got that far because of the hydrogen leak that prevented fueling of the launcher’s core stage.
“So we’ll hold to those two dates. We’ll continue to work with our great partner in the range as they evaluate the realism and feasibility of our waiver request and certainly if they decide that is not the right thing to do, we obviously will support that and stand down and look for our next launch attempt, but we still will press with the tanking test.”
A view of the tail service mast umbilical connected to the core stage of the SLS moon rocket during a rollback to the Vehicle Assembly Building on July 2. Credit: Stephen Clark / Spaceflight Now
Bolger said the launch team continues to fine-tune the procedures for loading cryogenic liquid hydrogen into the core stage in a bid to overcome the pesky leaks. Engineers aim to reduce flow and pressure changes during fueling for the upcoming tanking test, and the next launch attempt.
“We’re calling it a kinder and gentler approach to tanking,” Bolger said. “We think that may help reduce the stress of pulses or sudden changes on the seals.
“By replacing the seals and going this through cryo event, and making the tanking process as benign as possible, we’re optimistic that we can knock this problem flat and have a a successful tanking,” Bolger said.
The launch team commanding the propellant loading sequence over-pressurized the quick disconnect on the 8-inch liquid hydrogen fueling line during the Sept. 3 launch attempt, but Bolger said engineers are still investigating whether that pressure damaged the seal and caused the leak. The additional pressure did not exceed specifications for the quick disconnect, but reached levels above the required pressure.
Bolger said initial inspections of the 8-inch seal removed during the repair work at pad 39B showed a minor “notch” that could be a sign of damage, and a possible source of the leak. “The team will be taking a lot deeper look,” he said.
Even if the tanking test validates the leak repair, the 322-foot-tall (98-meter) Artemis 1 moon rocket may still have to return to the Vehicle Assembly Building. The U.S. Space Force’s Eastern Range — responsible for public safety for all launches from Kennedy Space Center and Cape Canaveral Space Force Station — has certified the moon rocket’s flight termination system batteries for 25 days, a life cycle that expires this week.
NASA officials confirmed Thursday they have asked the range to extend the certification of batteries on the flight termination system, which would destroy the SLS moon rocket if it veered off course and threatened populated areas during launch. The Space Force has already agreed to an extension from 20 to 25 days, enabling Artemis 1 launch attempts through all possible dates in the mission’s previous launch period, which ended Tuesday.
NASA submitted the flight termination system waiver request to the Eastern Range with data they say provide evidence the batteries will continue to be reliable for launch attempts in late September. If the Eastern Range does not agree to another extension, NASA will have to reset and re-test the flight termination system batteries. That work must occur inside the Vehicle Assembly Building.
A rollback to the VAB would delay the Artemis 1 launch until at least mid-to-late October. The next launch period opens Sept. 19 and runs through Oct. 4, followed by another series of launch dates from Oct. 17 through Oct. 31. The launch periods are governed by the position of the moon in its orbit around Earth, and other mission requirements to limit the time the Orion spacecraft spends in shadow and to ensure the capsule splashes down in daylight at the end of its mission.
NASA officials selected the tentative Sept. 23 and 27 launch dates to work the Artemis 1 mission around other schedule considerations. NASA’s DART spacecraft is on track to collide with a small near-Earth asteroid Sept. 26 in a demonstration of an asteroid deflection technique, a schedule that is set in stone due to orbital dynamics. That event requires support from the Deep Space Network, NASA’s worldwide network of antennas used for communicating and tracking missions beyond Earth orbit.
The DSN antennas are also needed for the Artemis 1 mission as the Orion spacecraft nears the moon a few days after launch. A liftoff Sept. 23 would put the Orion spacecraft’s critical maneuvers around the moon after the time of the DART asteroid impact.
There are also launches in late September and early October already on the Eastern Range. A United Launch Alliance Atlas 5 rocket is set for launch Sept. 30 from pad 41 at Cape Canaveral Space Force Station, and SpaceX’s Crew-5 astronaut mission to the International Space Station — under contract to NASA — is scheduled for liftoff Oct. 3 from pad 39A at the Kennedy Space Center.
Launch dates for Artemis 1 in early October — near the end of the next launch period — may be unavailable due to scheduling conflicts with preparations for the Crew-5 launch from pad 39A, less than 2 miles south of pad 39B. The Crew-5 mission could take priority on NASA’s schedule because it is a human spaceflight mission needed to continue operations on the International Space Station.
The two-hour launch window Sept. 23 opens at 6:47 a.m. EDT (1047 GMT), and would result in the Orion spacecraft returning to Earth for splashdown in the Pacific Ocean on Oct. 18. The Sept. 27 launch opportunity has a 70-minute window opening at 11:37 a.m. EDT (1537 GMT), with a mission that would end with a Nov. 15 splashdown for the Orion capsule.
“We’ll hold to those two dates,” Free said. “We’ll continue to work with our great partner in the range as they evaluate the realism and feasibility of our waiver request, and certainly, if they decide that is not the right thing to do, we obviously will support that and stand down and look for our next launch attempt, but we still will press with the tanking test.”
A view of the liquid hydrogen umbilical during a retraction test inside the Vehicle Assembly Building. Credit: NASA
The Artemis 1 mission will mark the first test flight of the SLS moon rocket, the most powerful launcher to ever lift off from U.S. soil. Its four main engines and two solid rocket boosters are leftover designs from the space shuttle program. The engines and boosters will generate 8.8 million pounds of thrust at launch, about 15% more power than the Saturn 5 moon rocket from the Apollo program.
The Space Launch System will send a human-rated Orion crew capsule on an unpiloted shakedown cruise around the moon. The Orion spacecraft will fly just 60 miles (100 kilometers) from the lunar surface and swing into a distant retrograde orbit, then fire its engines to begin a return course to Earth, culminating in a parachute-assisted splashdown in the Pacific Ocean off the coast of San Diego.
If it goes well, the test flight will pave the way for four astronauts to strap in to the Orion capsule on the Artemis 2 moon flyby mission, currently scheduled for launch in 2024. Future Artemis missions will include commercial lunar landers to ferry astronauts to and from the surface of the moon.
While NASA managers work through the hydrogen leak and flight termination system battery issues, engineers are also keeping an eye on the condition of the SLS moon rocket nearly two years after stacking of its solid rocket boosters began inside the VAB.
Ground teams began stacking the boosters on the mobile launch platform Nov. 20, 2020. A 12-month certification clock for the boosters began ticking with the stacking of the left-hand aft center booster segment Jan. 7, 2021.
NASA officials said then that the one-year certification, a holdover from boosters on the space shuttle program, could be extended with additional analysis of the condition of the solid-fueled rocket motors. That is what happened.
There is “minimal” risk for keeping the boosters stacked for at least the next few months, according to John Blevins, NASA’s chief engineer on the Space Launch System program.
Blevins said the rocket’s engineering team also wants to minimize movements of the launcher between the VAB and its launch pad. “It is an event that does add just routine wear and tear, and I don’t want to do that,” he said.
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