NASA的巨型登月火箭緩慢而壯觀地爬回發射台！

NASA is preparing for an exciting mission to send astronauts around the Moon, something that hasn't happened in over fifty years. The Space Launch System, or SLS, is NASA's huge new rocket, and it is paired with the Orion spacecraft. Recently, the SLS and Orion were rolled out from the Vehicle Assembly Building to Launch Pad 39B at Kennedy Space Center in Florida. This journey is only four miles, but it takes up to twelve hours because the rocket and its launch platform are so heavy and valuable. The Crawler-Transporter-2, a special vehicle built in 1965, moves the rocket very slowly to keep it safe. The rocket stands nearly 100 meters tall and weighs about 5,000 tonnes, making it taller than Big Ben's clock tower.

Earlier this year, NASA had to delay the launch because of a problem with the rocket's helium system. Helium is used to pressurize the fuel tanks, and any issue with this system could affect the rocket's performance or safety. Engineers brought the rocket back inside the Vehicle Assembly Building to fix the problem. They replaced faulty parts and tested the system again to make sure everything was working. Now, with the rocket back at the pad, engineers are running more tests to confirm that the repairs were successful and that nothing was damaged during the move. They will also practice parts of the countdown, using the same computers and networks that will be used on launch day, but without actually fueling the rocket.

The Artemis II mission will carry four astronauts: Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen. They are already in pre-flight quarantine and will travel to Florida closer to the launch date. The mission is planned for early April and will last about ten days. The crew will fly around the far side of the Moon before returning to Earth. This is the second time the Artemis II rocket has been moved to the pad, as the first attempt was interrupted by the helium issue. If all the final tests go well, NASA will decide a few days before the earliest launch opportunity whether to proceed. If the launch is delayed, there are several backup dates in April. This mission is a big step for NASA, as it will be the first crewed flight in the Artemis program, leading to future missions that aim to land astronauts on the Moon again.