The Artemis II mission, which will carry the next man and the first woman, North Carolina native Christina Koch, back to the Moon, is scheduled to launch no earlier than 6:24 p.m. on Wednesday, April 1.
On Sunday, Koch and the other astronauts in quarantine awaiting the Artemis II mission held a question-and-answer session that was livestreamed by NASA.
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"It is our strong hope that this mission is the start of an era where everyone can look at the moon and think of it as a destination," Koch, an NC State graduate who holds two bachelor's degrees and a master of science, said.
The countdown begins Monday at 4:44 p.m., when teams start preparing to fuel the towering rocket with more than 700,000 gallons of supercold liquid oxygen (LOX) and liquid hydrogen (LH2).
Throughout the process, meteorologists with the 45th Weather Squadron, based a few miles south of the launch pad at Cape Canaveral Space Force Station, will monitor conditions for any violations of launch weather commit criteria. These strict rules are based on decades of experience and hard lessons from earlier programs.
If conditions fall outside this narrow set of acceptable atmospheric limits, the launch will be delayed or scrubbed.
Unlike the Space Shuttle, which had only a few minutes to launch in order to reach the International Space Station, Artemis II has a two-hour launch window. That added flexibility gives teams time to wait out marginal weather or resolve technical issues.
Temperature
Temperature is monitored using sensors mounted on towers across the Cape at heights of 40 meters (about 130 feet) and 78 meters (about 256 feet). If the 24-hour average temperature drops below 5°C (41°F), the launch is delayed for at least 24 hours. With temperatures in Florida expected to remain in the upper teens Celsius (high 60s °F), this constraint is not expected to be an issue.
The Space Launch System (SLS) uses solid rocket boosters derived from the Space Shuttle program. These boosters include an additional segment on each side and incorporate hardware and design heritage from 84 shuttle missions.
This temperature rule traces directly back to the loss of Space Shuttle Challenger, which launched on an unusually cold January morning with temperatures around 2°C (36°F). The cold conditions compromised the seals in a joint of one of the solid rocket boosters.
At the upper end, if temperatures exceed 30°C (95°F) for more than 30 minutes, a launch delay may be required. Forecast highs in the upper 20s Celsius (low 80s °F) suggest this will not be a concern for the upcoming launch window.
Wind limits: Surface and upper-level risks
Wind is not a single measurement but a vertical profile that has to stay within limits from the ground up through the upper atmosphere. Conditions at the surface affect rollout and pad operations, while winds aloft can introduce shear that places additional stress on the vehicle during ascent.
Sensors near the launch tower and temperature instruments track conditions at the surface. Higher up, winds are measured using weather balloons launched by the 45th Weather Squadron, which provide a vertical profile of wind speed and direction, along with temperature and air pressure.
Lightning and electrified clouds
The lightning rules are some of the strictest launch constraints, shaped in large part by what happened during the Apollo 12 lightning strike incident. The rocket was struck by lightning just after liftoff, knocking out nearly all of its electrical systems.
The situation was saved by John Aaron, later nicknamed the “steely-eyed missile man” by his colleagues. He recognized the problem from a simulation and calmly told the crew to switch SCE to AUX, a move that brought the spacecraft’s systems back online. He would later play a key role during Apollo 13 mission, helping develop the power-up sequence that brought the damaged spacecraft home.
Today, missions are not allowed to launch near thunderstorms or electrified cloud fields. Even clouds that are not producing storms can violate the rules if they contain the right mix of ice and liquid water.
Clear skies are not always safe either. Rockets can trigger lightning as they pass through charged layers in the atmosphere, so even a bright, cloud-free day can lead to a scrub.
Clouds, precipitation and icing
NASA avoids launching through:
- Clouds producing precipitation
- Thick cloud layers extending up into freezing temperatures
- Clouds capable of charge buildup
So what are the chances the astronauts will actually be on their way to the moon on Wednesday?
The current forecast shows rain chances picking up around midday, then easing as the launch window approaches. It is still early, and Florida weather can be unpredictable, so that outlook should be taken as a bit of encouragement rather than anything firm.
If a delay is needed, Thursday may bring more of a challenge, with isolated showers in the forecast.
At this point, the chances of Artemis II launching on its first opportunity on April 1 at 6:24 p.m. are essentially a coin toss. Everything either comes together, with fueling, technical work, and weather all within limits, or it does not.