Liftoff! Artemis II Astronauts Begin Historic Moon Mission

For the first time in more than half a century, human astronauts are heading to the moon.

Launch Complex 39B at NASA’s Kennedy Space Center in Florida erupted in flames Wednesday evening as the agency’s Space Launch System (SLS) rocket fired its boosters and engines, generating 8.8 million pounds of thrust and sending four astronauts—three American, one Canadian—on a 10-day trip around the moon and back.

If the Artemis II mission goes to plan, NASA astronauts Reid Wiseman, Victor Glover, and Christina Koch and Canadian Space Agency (CSA) astronaut Jeremy Hansen will travel farther from Earth than any human has before. If conditions are right, they could also be the first humans to lay eyes on parts of the far side of the moon.

The Artemis II crew will not actually land on the moon. But akin to Apollo 8, it will test a mission profile that could enable future lunar landings, beginning with the Artemis IV mission in 2028. NASA Administrator Jared Isaacman in March said the space agency plans for semiannual landings after that as it looks to build a permanent $30 billion base.

There is plenty riding on the Artemis campaign, which President Donald Trump formally established in 2017 as a successor to the Apollo program. It is years behind schedule and billions of dollars over budget, having flown only a single uncrewed test flight in 2022. Artemis II is the first time NASA’s SLS and Orion crew capsule are flying with astronauts.

For a deeper dive on the spacecraft and crew behind the mission, which you can track in real time, check out FLYING’s Artemis II guide.

Burn, Baby, Burn

During the mission’s first flight day, SLS and Integrity—the name of the Artemis II Orion vehicle—performed a series of burns to place the crew on a precise, figure-eight-shaped trajectory that will send them more than 230,000 miles from Earth. Day two will begin the sojourn to the moon.

During the countdown, teams loaded the SLS core stage with more than 750,000 gallons of supercooled liquid oxygen and liquid hydrogen propellant. Following a brief hold in the countdown to address an issue with a battery on the Launch Abort System (LAS)—designed to generate 400,000 pounds of thrust and pull Orion to safety in the event of an early emergency—the mission lifted off at 6:35 p.m. EDT.

The SLS’ four core stage RS-25 engines, repurposed from the space shuttle program, fired about one second before launch. Each produces 2 million pounds of thrust for the approximately eight-minute ascent to orbit.

At T-0, SLS activated its twin solid rocket boosters—the largest such structures in history, providing about the same thrust as 25 airliners firing at full throttle. They are about 17 percent more powerful than those powering the Apollo-era Saturn V. Combined, the boosters and engines give SLS enough juice to clear the launch tower.

After performing what is called a roll maneuver—rotating along its vertical axis to adjust attitude and set itself on the proper orbital trajectory—SLS broke the sound barrier around the one-minute mark. Seconds later, it reached Max Q, the point when the vehicle experiences peak aerodynamic stress as it pushes through the dense lower atmosphere.

Around the two-minute mark, explosive bolts fired to jettison the boosters from the SLS core stage. They splashed down north of the Bahamas about four minutes later. The launch abort system was also expended.

About eight minutes in, the spacecraft reached 100 nm in altitude and was traveling about 17,000 mph. It began to slow when the SLS core stage engines throttled down for main engine cutoff (MECO), marking the start of one of the mission’s most exciting phases.

The crew, traveling in the Integrity capsule, separated from the SLS along with the interim cryogenic propulsion stage (ICPS)—the upper stage mechanism responsible for adjusting its orbit. The ICPS took over steering, established communications with mission control in Houston, and chilled its engine to prepare for additional burns. Integrity unfurled its solar array wings, designed to augment its fuel system and provide power to the entire spacecraft.

The ICPS performed two burns to raise Integrity to what NASA considers a safe, high-Earth orbit. From there, a final push, scheduled for Thursday night, will send the crew on their approximately four-day journey to lunar orbit.

Up Close and Personal

The next highlight came about an hour later, when the ICPS separated from Integrity and served as target practice for a proximity operations demonstration.

The crew took manual control of the vehicle, flying it toward and around the detached stage to simulate docking with another spacecraft. That will be necessary for future Artemis missions that add more vehicles and complex maneuvers to the equation.

After Integrity moved a safe distance away, the ICPS fired one last time to put it on course for a splashdown in the Atlantic Ocean. Then, the Orion Stage Adapter—a ring connecting the ICPS and Orion—ejected four shoebox-sized CubeSats, or square-shaped miniature satellites. The CubeSats come from Artemis Accords signatories Argentina, South Korea, Germany, and Saudi Arabia and will perform a range of on-orbit experiments.

Saudi Space Agency CubeSats will collect data on space radiation, solar X-rays, solar energetic particles, and magnetic fields. Argentina’s will measure the radiation spectrum around Earth, collect GPS data, and test a long-range communications link.

The Korea Aerospace Administration’s CubeSat contains material designed to mimic human tissue, allowing it to measure radiation across the Van Allen belts—one of the most hazardous regions for astronauts. Germany’s experiment will study the performance of electrical components to guide the design of future lunar vehicles.

The astronauts themselves will also conduct science during the mission, both as researchers and test subjects.

They agreed to wear wristbands that monitor their movement and sleep patterns and place radiation-detecting devices in their pockets. The latter are being used beyond low-Earth orbit for the first time. NASA installed six radiation sensors throughout Integrity to further measure exposure.

While in Earth orbit, the astronauts will remove their spacesuits and gauge the Orion life support system’s ability to provide breathable air. They will don the suits again only during dynamic parts of the mission, spending most of it in plainclothes.

Crewmembers also donated blood to create miniature stand-ins of their bone marrow, contained in USB-sized chips. Bone marrow is considered particularly sensitive to radiation.

After completing their activities in Earth orbit, the crew will get some rest before the translunar injection burn—one of the mission’s riskiest phases according to John Honeycutt, manager of NASA’s SLS program.

More Excitement Ahead

The Artemis II astronauts have already completed several objectives. But the mission is just getting started.

The next few days should be relatively quiet as Integrity transits to lunar orbit. Things will pick up again on flight day five, when the capsule begins experiencing a stronger gravitational pull from the moon than the Earth.

By day six, the astronauts will begin orbiting the moon. NASA’s Lunar Reconnaissance Orbiter and other spacecraft have been mapping the lunar surface for decades. But humans can pick up on subtle changes in color or terrain that machines cannot, giving NASA an opportunity it has not had in decades.

Artemis II will fly tens of thousands of miles closer to the surface than humans have been in 50 years. At that distance, the moon will appear about the size of a basketball held at arm’s length. The hope is that the astronauts can collect imagery that gives researchers a new perspective.

The return trip figures to be one of the trickier portions of the mission. Integrity will disengage its propulsion systems after slingshotting around the moon. Instead, it will rely on Earth’s natural gravity to pull it home.

The ill-fated Apollo 13 is the only mission to travel around the moon in that trajectory, called a free return. Apollo 12 used a hybrid free return on approach to the moon. But the strategy is largely untested, used mainly as a contingency flight profile—until now.

Integrity will face another test during atmospheric reentry, when it hits an estimated 25,000 mph and external temperatures reach up to 5,000 degrees Fahrenheit as superheated plasma enshrouds the vehicle. Its heat shield is designed to protect the crew against these conditions.

During the uncrewed Artemis I mission, however, the heat shield unexpectedly cracked and chipped away. Rather than replace it, NASA modified Artemis II’s reentry profile to reduce strain on the structure. A new heat shield will be installed for Artemis III.

Honeycutt, the NASA SLS program manager, estimated the mission has between a 1 in 2 and 1 in 50 chance of failure. The agency’s crew loss threshold is 1 in 40 for lunar missions and 1 in 30 for Artemis missions overall, better than the Apollo program’s 1 in 10 figure. Honeycutt said the perigee raise and translunar injection are the mission’s riskiest phases.

What’s Next?

Artemis II’s level of success could have a ripple effect on the rest of the NASA campaign.

In February, Isaacman overhauled Artemis, adding a new mission in 2027 before the first lunar landing. The idea is to gradually test new capabilities rather than evaluating them all in a single mission. But any hiccups could drive cascading delays to future missions, or even another overhaul.

If all goes to plan, NASA will proceed with Artemis III, which is intended to test one or both human landing systems (HLS) developed by SpaceX and Blue Origin. The HLS vehicles will conduct in-orbit demonstrations, including docking and propellant transfer. They are designed to rendezvous with Orion in lunar orbit, deliver crew to and from the moon’s surface, and serve as temporary habitats.

After that, NASA believes it will be ready for the real deal in 2028. That will depend on SLS and Orion being ready for Artemis II. The space agency will soon get its answer.