NASA plans to roll its huge moon rocket back to the launchpad at Florida’s Kennedy Space Center on Thursday evening, setting the stage for four astronauts’ much-anticipated journey around the moon. The 322-foot-tall Space Launch System rocket, topped with the Orion capsule, will launch the crew on a 10-day trip as early as April 1. But first, the rocket and spacecraft must make a painstakingly slow, 4-mile trek from the hangar to the launchpad. The journey is set to begin at 8 p.m. ET and will likely wrap up around 12 hours later. It’s the second rollout process for the 11-million-pound rocket. It was first rolled to the launchpad in mid-January, but several weeks ago, engineers found a blockage in the flow of helium that required NASA to roll the rocket back to its Vehicle Assembly Building for repairs. The vehicle's return to the launchpad will involve a moving platform known as a crawler-transporter, which will inch along at a pace of around 1 mile per hour.…