As the countdown reaches zero at 6:24 pm EDT, the Space Launch System rises in a column of fire, its engines straining against Earth’s gravity. At liftoff, nearly 8.8 million pounds of thrust surge through the vehicle, driven by twin solid rocket boosters that burn for the first two minutes.
The ascent is violent, deliberate, and unforgiving — a phase where even minor anomalies can escalate quickly. For Artemis II, the first crewed lunar mission in more than five decades, this marks the beginning of a carefully sequenced test to carry humans beyond low Earth orbit once again.
The boosters separate and fall away, shedding weight and allowing the core stage — powered by four cryogenic RS-25 engines — to take over. These engines rely on liquid hydrogen and liquid oxygen stored at extremely low temperatures, creating technical challenges under vibration and acceleration. Over the next several minutes, the core stage pushes Orion towards orbital velocity. By the time it shuts down and separates, roughly eight minutes into flight, the spacecraft is moving fast enough to remain in orbit — a critical milestone in the journey outward.
The Interim Cryogenic Propulsion Stage then assumes control. Its first burn lifts Orion into a stable, highly elliptical orbit around Earth. Here, the mission enters a brief but critical pause. Inside the Crew Module, Commander Reid Wiseman, pilot Victor Glover, and mission specialists Christina Koch and Jeremy Hansen begin checks that determine whether they proceed further.
Environmental controls, carbon dioxide removal, navigation, and communication links are verified in real conditions. The crew also conducts manual piloting exercises, demonstrating that Orion can be steered with precision if automation fails — a capability vital for future deep-space operations.
This phase is not routine. It is a checkpoint. As Artemis II flight director Fiona Antkowiak told BBC, “Translunar injection is a huge decision — you must be sure the spacecraft can support the crew for up to 10 days, because once you commit, there are no quick ways to return.” The risk is clear: beyond this point, contingency options narrow.
Once cleared, the ICPS executes the translunar injection burn — a manoeuvre that sends Orion out of Earth orbit and onto a path towards the Moon.
Precision is everything.
A slight deviation in angle or velocity can require fuel-intensive corrections later. The spacecraft now enters a regime where the gravitational pull of both Earth and the Moon is balanced.
Along this trajectory, Orion operates as a self-contained system. Its European Service Module supplies propulsion, power, and life-support consumables, including oxygen, nitrogen, and water. Unlike the International Space Station, Orion does not rely on a fully closed-loop system. Instead, it combines stored resources with limited recycling — a design that sustains the crew without resupply. Any failure escalates quickly, making redundancy and monitoring critical.
As the spacecraft travels further from Earth, navigation depends on star trackers, inertial systems, and updates from ground stations. Small thruster burns adjust the trajectory as needed. When the spacecraft passes behind the Moon, communication with Earth is temporarily lost. In this blackout, Orion operates autonomously, maintaining its course and handling anomalies without immediate support.
This is one of the mission’s key tests: whether crew and systems function independently in deep space.
Radiation adds another layer of risk. Outside Earth’s magnetosphere, astronauts are exposed to galactic cosmic rays and solar particle events. Unlike missions in low Earth orbit, where some shielding exists, Orion relies on its structure and operational strategies to limit exposure.
Mylswamy Annadurai, project director for Chandrayaan-1, tells TNIE that the shift in lunar missions reflects a broader ambition. “The latest mission is about returning humans to the Moon,” he says, noting that earlier Apollo missions focused on short visits near the equator. “Now, the focus has shifted after the discovery of water on the Moon. Missions are targeting these areas.” He adds that the larger challenge lies in sustaining human presence: “Earlier astronauts stayed only for a few hours or days, but longer missions now require protection from space radiation, better life-support systems, and safety mechanisms for prolonged exposure.”
As Orion loops around the Moon, it follows a free-return trajectory, shaped by gravity rather than constant propulsion. The Moon’s pull bends the spacecraft’s course and sends it back towards Earth, providing a built-in safety margin if engines fail. Even so, thermal control remains a concern. In the vacuum of space, temperatures swing sharply between extremes. Orion maintains stable internal conditions through insulation, radiators, and active management.
The return to Earth introduces the most intense phase. Re-entry occurs at speeds approaching 39,000–40,000 km/h, far faster than typical orbital missions. The challenge is not friction alone, but the compression of air ahead of the spacecraft, generating extreme heat. Orion’s ablative heat shield absorbs and sheds this energy by burning away in layers, protecting the structure beneath. The angle of entry is exact — too steep, and the spacecraft risks structural damage; too shallow, and it could skip off the atmosphere.
As parachutes deploy in sequence and Orion descends towards splashdown, mission control monitors every parameter. “Everything we do is focused on one priority: making sure the crew returns home safely,” Trey Perryman told BBC.
By the time the capsule reaches the ocean, Artemis II tests not just hardware, but the ability of humans and machines to function together in deep space. It builds on decades of exploration, from Apollo’s brief visits to more recent discoveries of water ice. The mission ultimately assesses whether current technology and human endurance can support longer journeys — a necessary step before any sustained presence on the Moon, and before moving deeper into the solar system.