2 months ago
NASA is rolling out its giant Moon rocket to the launch pad for a second time ahead of a mission to send astronauts around the Moon — a feat not attempted in more than 50 years.
The 98-meter-tall Space Launch System (SLS) and Orion spacecraft are making the four-mile journey from their assembly building to Pad 39B at the Kennedy Space Center in Florida.
This move follows a problem with the rocket's helium system that forced NASA to abandon a launch attempt in March and return the vehicle indoors for repairs.
Engineers say the issue has now been fixed and hope that a series of final tests at the pad will confirm the rocket is ready for an early-April launch window.
Just after nightfall, the SLS emerged from the Vehicle Assembly Building (VAB) — one of the largest buildings in the world — and began its slow crawl towards the Atlantic coast.
Standing taller than Big Ben's clock tower at nearly 100 meters, the rocket and its launch platform weigh about 5,000 tonnes. They are being carried by Crawler-Transporter-2, a low-slung, tank-like vehicle on caterpillar tracks that NASA built in 1965 to inch Saturn V Moon rockets to the pad.
Its maximum speed is about 1 mph (1.6 km/h), and it moves even more slowly on bends and up the gentle ramp to the launch pad, so the four-mile journey can take up to 12 hours.
The slow pace is intentional: like carrying a precious Ming vase, the gentle motion reduces stresses on the multi-billion-dollar rocket and launch tower. The slow speed also gives flight teams the best chance to spot and stop any unwanted movement of what is effectively a mobile skyscraper.
Once the rocket reaches the pad, engineers will spend several days verifying that the repairs carried out in the VAB have worked as intended and that nothing shifted during the slow journey out. They will reconnect the launch tower to the vehicle and run pressure tests on the helium system that caused the earlier problem.
Controllers will also rehearse parts of the countdown, sending commands through the same computers and networks that will be used on launch day, but without filling the tanks with fuel.
After these tests, NASA's mission management team will meet a few days before the earliest launch opportunity on April 1 to review the data and decide whether to proceed.
The Artemis II crew — Reid Wiseman, Victor Glover, Christina Koch, and Jeremy Hansen — have entered pre-flight quarantine and will travel to Florida closer to launch to participate in various rehearsals, including suiting up and traveling to the pad. NASA is targeting launch opportunities in the first week of April for the ten-day mission, which will loop around the far side of the Moon before returning to Earth.
This is the second time the Artemis II rocket has made the trip to the pad. In March, NASA had to roll it back to the assembly building after detecting an interruption in the flow of helium to the upper stage during a fueling test. Helium is used to pressurize propellant tanks, and any fault in that system could affect the performance of the upper stage engine or the safe draining of fuel.
Rather than pressing ahead, managers chose to stand down from the planned launch window and return the SLS to the VAB so engineers could fully access the problem area instead of investigating while it was on the pad.
Inside the VAB, work platforms were raised around the upper stage so specialists could reach valves and plumbing in the helium circuit. Engineers replaced suspect components, swapped batteries in several critical systems, and repeated tests to confirm the fault had been cleared.
After reviewing the data, NASA managers approved a second rollout and the next phase of checks at the pad. If those tests are completed without incident, Artemis II will become the first crewed mission in the Artemis program, paving the way for another crewed test flight, Artemis III, scheduled for 2027 in Earth orbit, followed by Artemis IV in 2028, which aims to see astronauts set foot on the Moon.
For the first launch opportunity, NASA is targeting 18:24 Eastern Daylight Time on April 1, which is 23:24 in the UK. If that attempt is delayed, further launch windows are available on April 2, 3, 4, 5, and 6. If those are missed, there is a final opportunity on April 30.
