NASA will try to launch Artemis again on Saturday, Sept. 3

The Space Launch System (SLS) is the most powerful rocket ever built
Artemis 1 has been waiting on the launch pad since the first attempt was scrubbed on Monday. (Image credit: NASA)

NASA will make its second attempt at launching its 'mega moon rocket' this Saturday (Sept. 3.), the space agency announced, just days after scrubbing the rocket's first liftoff attempt following an engine issue.

The Artemis 1 rocket is made up of the six-person Orion capsule perched atop the 30-story Space Launch System (SLS) — dubbed the 'mega moon rocket' — and was initially scheduled to embark on its maiden voyage to the moon and back on Monday (Aug. 29). But engineers were unable to cool one of the rocket's four core stage RS-25 engines down to a safe temperature in time for launch. That issue, along with poor weather conditions, forced NASA to cancel the launch just two minutes into the spacecraft's two-hour launch window, NASA officials said at a news conference on Tuesday (Aug. 30). 

The rocket's new window for a second attempt will be on Sept 3., one day later than the earliest available window of Friday (Sept. 2.), which NASA ruled out due to a high risk of adverse weather conditions. 

Related: Lightning strikes Artemis I mission's 'Mega Moon rocket' launch pad during tests

"The launch pad time for a Saturday attempt would be 2:17 p.m. EDT," Mike Sarafin, NASA's Artemis mission manager, said at a news conference on Tuesday. "It's a two-hour window." NASA officials added that if the rocket didn't take off on Saturday, another launch could be scheduled as soon as 48 hours later.

NASA views this flight as the first of three missions that will be a vital testbed for the hardware, software and ground systems that are intended to one day transport the first humans to Mars and beyond. The upcoming uncrewed Artemis 1 test flight — part of the Artemis program named after the twin sister of the ancient Greek god Apollo — will be followed by Artemis 2 and Artemis 3 in 2024 and 2025/2026 respectively. Artemis 2 will make the same journey as Artemis 1, but with a four-person human crew, and Artemis 3 will send the first woman and the first person of color to land on the moon's south pole. 

Monday's launch was scheduled for 8:33 a.m. ET, but the attempt was plagued with problems from the beginning. Initial fueling attempts hit delays in the early hours of Monday morning when lightning, which had already struck the Artemis rocket pad two days before, threatened to zap the rocket again. 

Then, not long after 3 a.m. ET, the launch team announced it was having problems filling the rocket with supercooled liquid hydrogen fuel. These problems are reminiscent of those the team reported having during April's wet dress rehearsal, where a faulty helium valve and a liquid hydrogen leak prevented the rocket from being prepared to the point of ignition, Live Science previously reported. Another snag for Monday’s failed launch came when engineers spotted a suspected crack in the rocket's thermal insulation, although it was later deemed to be superficial.

The issue that finally scuppered the launch arrived just after 6 a.m. ET, when the team declared that the liquid hydrogen fuel was only cooling three of the rocket's four engines to sufficient temperatures prior to ignition. The problematic engine, named engine three, appeared to be around 40 degrees Fahrenheit (22 degrees Celsius) warmer than the temperature of minus 420 F (minus 250 C) needed for launch.

NASA will attempt to fix this issue for Saturday afternoon's launch by performing the engine chilling procedure half an hour earlier — a trick officials say was effective during a successful test conducted last year. 

And the engine may not have trouble cooling at all; NASA scientists have suggested a faulty temperature sensor may have falsely reported the temperature inside the engine as being much higher, and much further from flight-ready, than it actually was. 

"The way the sensor is behaving does not line up with the physics of the situation," John Honeycutt, NASA's program manager for the Artemis 1 mission, said at the news conference.

The faulty sensor cannot be easily replaced, and swapping it out would likely mean the rocket has to be rolled back to NASA's Vehicle Assembly Building for a thorough investigation. As this would probably mean delaying the launch for several months, Honeycutt said that his team was looking into creating a workaround plan that would enable flight engineers to make an "informed decision" on whether the rocket could take off without taking readings from the sensor.

NASA is banking heavily on a successful mission for Artemis 1, which has come under scrutiny for a price-tag that has ballooned to eye-watering levels. The program, which began in 2017, has already cost more than $40 billion to develop and is projected to knock U.S. taxpayers back by $93 billion by the end of 2025, according to the office of NASA inspector general Paul Martin — the space agency's internal auditor.

"Given our estimate of a $4.1 billion per-launch cost of the SLS/Orion system for at least the first four Artemis missions, NASA must accelerate its efforts to identify ways to make its Artemis-related programs more affordable," Martin said at a March 1 testimony before the House Subcommittee on Space and Aeronautics. "Otherwise, relying on such an expensive single-use, heavy-lift rocket system will, in our judgment, inhibit if not derail NASA's ability to sustain its long-term human exploration goals of the moon and Mars."

Despite these issues, NASA officials insist that the American public will find the cost of the rocket — which they say will kickstart a new era of space exploration — to be justified. 

"This is a brand new rocket. It's not going to fly until it's ready," NASA administrator Bill Nelson told reporters on Monday following the scrubbed launch. "There are millions of components of this rocket and its systems, and needless to say, the complexity is daunting when you bring it all into the focus of a countdown."

Nelson added that his own space shuttle launch, held in 1986 while he was a member of Congress, had four scrubs before it eventually took off.

"Had we launched on any one of those scrubs, it wouldn't have been a good day," he said.

NASA will be eager to launch Artemis before Sep. 10, the peak date of this year's hurricane season. So far, no named hurricanes have formed this year, but signs of increasing storm activity in the Atlantic basin suggest the period of unusual calm could be about to end.

Originally published on Live Science.

Ben Turner
Staff Writer

Ben Turner is a U.K. based staff writer at Live Science. He covers physics and astronomy, among other topics like tech and climate change. He graduated from University College London with a degree in particle physics before training as a journalist. When he's not writing, Ben enjoys reading literature, playing the guitar and embarrassing himself with chess.