NASA gears up for one more key test before launching Artemis II to the Moon

"If things do not go so well, NASA's chances for launching Artemis II this month will likely wither away. NASA only has a handful of launch opportunities each month where everything lines up for Artemis II's flight around the Moon. The first two of this month's launch dates, February 6 and 7, are no longer an option after NASA ordered the two-day delay in this week's practice countdown. Here are the three launch opportunities still available this month, each with a two-hour launch window:"

"It took four tries for NASA to fully load propellants onto the first SLS rocket during a series of Wet Dress Rehearsals (WDRs) in 2022. None of the practice runs were free of problems. The list of technical snags included difficulties supplying gaseous nitrogen to the launch pad, problems keeping liquid oxygen at the proper temperature, and a series of valve and seal failures that led to persistent leaks of hydrogen fuel."

"Molecular hydrogen is notoriously difficult to wrangle. It is highly flammable, and the molecule's fantastically low mass and tiny dimension make it hard to contain. The cryogenic temperature of the liquified form of hydrogen is an additional complication. Liquid hydrogen must be kept at temperatures around minus 423° Fahrenheit (minus 253° Celsius), cold enough to freeze solid any gas it comes in contact with except for helium."

Artemis II's February launch prospects narrowed after a two-day delay in the practice countdown removed February 6 and 7 as options. Three remaining February launch dates each offer two-hour windows; missing them shifts the next opportunity to March 6 with additional dates through April. Wet dress rehearsals are essential to validating launch readiness and will determine the path forward. Previous Wet Dress Rehearsals required multiple attempts to fully load propellants, revealing issues with gaseous nitrogen supply, liquid oxygen temperature control, and valve and seal failures that caused hydrogen leaks. Liquid hydrogen handling poses major containment and cryogenic temperature challenges.

Read at Ars Technica