Countdown to Lunar Orbit: Understanding Artemis 2 by the Numbers

As NASA nears the launch of the highly anticipated Artemis 2 mission, understanding the key figures provides crucial context for this historic endeavor. The agency is targeting an April 1 launch attempt to send a crew of four astronauts on a journey around the Moon.

This mission represents a monumental leap, as it will be the first time humans have ventured beyond low Earth orbit in over 50 years. Assuming the April 1 launch date holds, 19,474 days will have elapsed since the final Apollo mission in 1972.

The Duration and Distance of the Lunar Flyby

The entire Artemis 2 mission is scheduled to last for 10 days. During this period, the crew will travel a total distance of 1.4 million miles. Their flight path is designed as a figure-8 trajectory around the Moon.

This path will take the Orion spacecraft approximately 4,600 miles past the far side of the Moon before initiating the return loop to Earth. At its furthest point, Orion is expected to reach a maximum distance of 250,000 miles from our planet.

The Power Behind the Mission: The SLS Rocket

The Space Launch System (SLS) rocket, which will propel the crew, is currently recognized as the most powerful operational rocket globally. Its core stage is propelled by four RS-25 engines, each generating about 512,000 pounds of thrust.

The two solid rocket boosters contribute an additional 7.2 million pounds of thrust combined. The SLS has flown only once previously, during the uncrewed Artemis I mission in 2022. The core stage requires a massive 733,000 gallons of super-cooled liquid hydrogen and liquid oxygen propellant.

Cost and Heritage of the Megarocket

The SLS architecture draws heavily from older Space Shuttle technology. This reliance on legacy systems has contributed to significant expense increases over time.

In 2023, the cost for a single SLS flight was reported to have risen to a minimum of $4.2 billion. The Office of Inspector General (OIG) linked roughly $6 billion in overruns, specifically concerning the propulsion systems, to chronic delays and contract structures.

The Crew: Experience and Exposure

The Artemis 2 crew consists of four astronauts: NASA’s Reid Wiseman (Commander), Victor Glover (Pilot), Christina Koch (Mission Specialist), and the Canadian Space Agency’s (CSA) Jeremy Hansen (Mission Specialist).

Collectively, the crew has logged 714 days in space, primarily aboard the International Space Station. Broken down, Wiseman has 165 days, Glover has 167 days, and Koch has 328 days. CSA astronaut Jeremy Hansen will be making his first journey to space with this mission.

Radiation Concerns During Transit

NASA estimates that each crew member could face radiation exposure ranging from 20 to 30 millisieverts (mSv) during the mission. In the rare event of a major solar particle storm, the Orion design limits crew exposure to under 150 mSv.

These projected levels remain well below NASA’s established career limit of 600 mSv for astronauts, suggesting the radiation risk for Artemis 2 is manageable.

Navigating the Lunar Shadow and Reentry Risks

When Orion passes behind the Moon, communication with Earth will be temporarily lost. This blackout period could last anywhere from 30 to 50 minutes, depending on the exact launch time, as the Moon blocks radio signals.

During this communication loss, the spacecraft will operate on autopilot, requiring the crew to manage any unexpected issues independently without mission control support. The spacecraft relies on a single main engine, eight auxiliary engines, and 24 reaction control thrusters for maneuvers.

The Critical Reentry Phase

Artemis 2 will feature zero lunar landings; its purpose is to pave the way for Artemis 4, tentatively slated for 2028, which aims for a crewed lunar surface landing. However, reentry remains the mission's most precarious stage.

Orion’s heat shield is engineered to endure temperatures up to 5,000 degrees F and reentry speeds reaching 24,700 mph. The landing sequence involves an 11-parachute system. Drogue parachutes deploy at 23,000 feet to slow the craft to 307 mph, followed by main parachutes deploying at 9,500 feet to ensure a splashdown speed of about 17 mph in the Pacific Ocean off California.