KENNEDY SPACE CENTER, Florida—The upcoming launch to the Moon represents a full day of meticulous preparation, a reality well understood by the four astronauts preparing to embark on NASA’s Artemis II mission.
“It is actually a very long day,” remarked Victor Glover, the pilot for Artemis II. “We wake up about eight hours before launch, and there’s a pretty tight schedule of things to get out there.”
Glover and his three crewmates have their schedules intricately defined to maximize efficiency throughout the nine-day Artemis II mission. If all proceeds as planned, the mission will take them over 250,000 miles from Earth, further into space than any humans have gone previously. Following their trajectory around the Moon, the crew and their Orion capsule will re-enter Earth's atmosphere at a speed of approximately 25,000 mph (40,000 km/hr), setting a new record for human travel velocity.
Reid Wiseman, the mission commander, will partner with Glover at the controls of the Orion spacecraft’s cockpit. Complementing them are mission specialist Christina Koch and Canadian astronaut Jeremy Hansen. Each astronaut plays an essential role in the mission, which aims to validate the Orion spacecraft, a vehicle that has been in development for two decades and is now ready for its inaugural crewed flight.
The launch could take place as early as Wednesday from NASA’s Kennedy Space Center in Florida. The mission has a two-hour launch window beginning at 6:24 pm EDT (22:24 UTC). Viewers can watch NASA’s live coverage of the countdown and launch via the embedded YouTube stream below.
As the full Moon rises in the eastern sky over the launch site during this launch window, the significance of their destination has deepened for the Artemis II astronauts since their selection three years ago. This mission is the first crewed endeavor of NASA’s Artemis program, which aspires to establish a sustainable human presence on the Moon, including a lunar base at the Moon’s south pole, to facilitate future missions to Mars.
“A destination is not just something we’re looking at,” stated Koch, 47, a former spacecraft engineer and Antarctic explorer. “It is our strong hope that this mission is the start of an era where everyone, every person on Earth, can look at the Moon and think of it as also a destination.”
NASA has successfully carried out nine Apollo missions to the Moon, achieving six landings; however, no humans have visited since 1972. Artemis II aims to alter that course. Sixty years ago, America was in competition with the Soviet Union in the space race. Presently, China has its sights set on landing its citizens on the Moon by 2030. According to NASA's current timeline, U.S. astronauts are expected to set foot on the lunar surface by 2028.
Artemis II has six available launch opportunities through Monday, April 6. If the mission does not launch during this window, it would have to wait until the end of the month for the next opportunity to attempt a Moon mission. Launch windows are contingent upon various factors, including the Moon's position in its 28-day orbit around Earth, trajectory needs to ensure the Orion spacecraft receives adequate sunlight for battery charging, and the required reentry angle into the atmosphere over the Pacific Ocean. The precise trajectory for the mission varies based on the launch day.
Wiseman understands that there is a possibility Artemis II may not launch on Wednesday.
“The way I kind of think about it in my head is this is the first time we’re loading the crew on (the rocket), with fuel, on the pad,” explained Wiseman, a 50-year-old former Navy test pilot. “NASA is ready. This vehicle is definitely ready to go. We went through the flight readiness review. We are ready to launch, but we’re also humans trying to load millions of pounds of propellant onto a giant machine and send it to the Moon.
“So it could very well be that we get on April 1, and we’re behind timeline and we’re just not ready as a team, and then we’ll probably take a 24 or 48 hour pause,” Wiseman added. “If we get off on the 3rd, great. If we get on the 6th, great. If we’ve got an issue and we’ve got to come back in May or June or whenever the vehicle and the team are ready, we are ready for that.”
Key Countdown Considerations
NASA has outlined critical elements to monitor during the countdown. Here are the key considerations.
Will hydrogen leak again?
At approximately 7 am EDT (11:00 UTC), NASA is scheduled to start loading over 750,000 gallons of super-cold propellant into the 322-foot-tall (98-meter) Space Launch System (SLS) rocket. This is a complex procedure that demands precision.
The process of preparing the rocket for propellant loading will commence roughly 11 hours prior to the launch, beginning with the thermal conditioning of the core stage tanks to ready them for their cryogenic contents.
Once the tanks achieve the necessary cryogenic temperatures, the flow of liquid hydrogen into the core stage is anticipated to commence around 8:30 am EDT, with the introduction of liquid oxygen following approximately 15 minutes later. The launch team plans to increase flow rates to “fast fill” mode for both tanks around 9:00 am EDT. This stage marks a critical point in the countdown as engineers monitor for any signs of gaseous hydrogen accumulation near the fueling connector at the bottom of the rocket.
Liquid hydrogen must remain at temperatures near minus 423° Fahrenheit (minus 253° Celsius), a condition cold enough to solidify any gas it encounters, except for helium. Furthermore, hydrogen, being the lightest element on the periodic table, tends to find leaking pathways. NASA is acutely aware of the challenges posed by hydrogen leaks, having grappled with them during the core stage fueling line for the uncrewed Artemis I test flight four years ago. Similar issues resurfaced when the launch team attempted to fuel the rocket for Artemis II for the first time in February.
In addition to its propensity for leaks, liquid hydrogen exerts stress on materials with which it comes into contact. The cryogenic temperature has the potential to alter the shape and integrity of seals and gaskets, leading to leak paths that might go undetected at standard temperatures.
After rectifying leaks found in February, technicians replaced the hydrogen seals on Artemis II, and the launch team successfully completed a countdown rehearsal several weeks later, bolstering confidence that the seals will hold during the actual launch. Nevertheless, NASA officials are still investigating the underlying causes of the seal failures. Sensors are in place to promptly identify any hydrogen accumulation during the countdown.
The process of filling both tanks on the SLS core stage will take approximately three hours. Following this, liquid hydrogen and liquid oxygen will begin to flow into the rocket’s upper stage shortly after core stage loading begins. If the countdown remains on schedule, the rocket should be fully fueled soon after 12 pm EDT. At that point, NASA plans to send the closeout crew to Launch Complex 39B to prepare for the astronauts' arrival. Throughout the countdown, the rocket will be gradually replenished with propellant.
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