The Artemis II astronauts will blast their main engine Thursday evening to propel the Orion capsule out of Earth’s orbit and on to its next phase — a four-day journey toward the moon.
The six-minute engine burn is a pivotal move that will put the astronauts on a trajectory that humans haven’t traveled in more than half a century. Going beyond Earth’s orbit comes with a host of risks, such as the sheer distance from home if anything goes awry, and the health effects of exposure to deep-space radiation from solar activity or cosmic rays once the astronauts are beyond the protection of Earth’s magnetic field.