CAPE CANAVERAL, Fla. (AP) — NASA begun fueling its moon rocket Wednesday for humanity’s first lunar trip in more than half a century, aiming for an evening liftoff with four astronauts.

Tensions were high as hydrogen fuel started flowing into the rocket hours ahead of the planned launch. Dangerous hydrogen leaks erupted during a countdown test earlier this year, forcing a lengthy flight delay.

The launch team needs to load more than 700,000 gallons of fuel (2.6 million liters) into the 32-story Space Launch System rocket on the pad before the Artemis II crew can board.

“It is time to fly,” commander Reid Wiseman said on the eve of launch via X. Favorable weather was forecast.

Three Americans and one Canadian will fly around the moon without stopping or even orbiting — then head straight back for a Pacific splashdown. They will set a new distance record for the farthest humans have traveled from Earth as they zoom some 4,000 miles (6,400 kilometers) beyond the moon and then hang a U-turn.

Astronauts last flew to the moon during Apollo 17 in 1972.

Artemis II is the opening shot of NASA's grand plans for a permanent moon base. The space program is aiming for a moon landing near the lunar south pole in 2028.

“The next era of exploration begins,” NASA Administrator Jared Isaacman posted on X.

Best wishes already have started to pour in, including from England's King Charles III to Canadian Space Agency astronaut Jeremy Hansen.

Hansen will become the first non-U. S. citizen to launch to the moon. The crew also includes Christina Koch and Victor Glover, the first woman and first Black astronaut, respectively, destined for the moon.

“In this historic moment, you stand as a bridge between nations and generations,” the king wrote in a letter to Hansen, “and I commend you for your courage, discipline and vision that have brought you to this threshold.”

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