Orion crossed into the Moon's gravitational sphere of influence on Day 5, approximately 322,000 km from Earth. It is the first human spacecraft to enter lunar gravity territory since Apollo 17 in December 1972: a gap of 19,478 days. 1
The crossing is an invisible threshold, not a physical barrier. At roughly 66,000 km from the Moon's centre, the lunar pull on the spacecraft exceeds Earth's. From this point forward, the Moon accelerates Orion rather than Earth decelerating it. The crew is committed. The translunar injection burn that fired on Day 2 set this trajectory; the extraordinary navigation precision that cancelled two consecutive correction burns confirmed the spacecraft was on course to reach it without adjustment.
Four people are now in a region of space no human has occupied since Eugene Cernan, Harrison Schmitt, and Ronald Evans departed it 54 years ago. In the intervening half-century, robotic probes from multiple nations visited the Moon. No crewed vehicle ventured beyond low Earth orbit. The gap between Apollo 17 and this moment is longer than the entire history of crewed spaceflight that preceded it.
