June 6, at 12:00 am E.T. SLS began it’s roll to Launch Complex 39B for the second time

As the clock struck midnight at the Kennedy Space Center SLS once again began to move towards the launch pad for another attempt later this month to load her fully with the super cooled propellants, and run a countdown rehearsal which NASA aims to complete before moving forward with the launch of Artemis I later this summer.

During the initial Wet Dress Rehearsal an issue with ground equipment at the launch pad caused a one day delay from April 3, then teams encountered issues with the supply of nitrogen gas to the launch pad. On April 4 a fueling attempt was cut short by concerns about the temperature of liquid oxygen flowing to the rocket’s core stage. Finally engineers discovered a problem with a helium valve on SLS’s upper stage. The valve issue prevented teams from being able to pump the upper stage full of propellant on the next attempt.

Now with the issues all currently resolved the 322 foot tall Moon rocket is once again ready to attempt the WDR (Wet Dress Rehearsal) again. Out of High Bay 3 of the Vehicle Assembly Building, the largest single story building in the world which was built to construct and service the Saturn V Moon rockets of the Apollo program, SLS once again begins its long slow journey to the launch pad. Riding a diesel powered crawler transporter, the 4.2 mile journey will take between eight and twelve hours to complete. With the SLS rocket, and its mobile launch platform weighing a combined 21.4 million pounds, the 6 million pound crawler transporter arrived with its precious cargo atop the ramp of pad 39B around sunrise today.

This SLS, or Space Launch System is the largest rocket NASA has yet to build, and is the flagship of the agency’s Artemis program which will return man, and land the first woman on the Moon’s surface later this decade. This mission, Artemis I will be a uncrewed test flight to send the Orion capsule around the Moon and back to Earth before it will fly with human cargo.

Before the mission takes flight however NASA will complete its WDR to test those countdown procedures and fully load the rocket with fuel, that’s more than 750,000 gallons of that super cooled liquid hydrogen and liquid oxygen. Currently planned for June 19 the WDR will last about forty-eight hours, and if all goes accordingly this go around officials have voiced, with caution, a potential August liftoff. That said, an official target window won’t become finalized until the data from the Wet Dress Rehearsal has been fully analyzed, and there are no further issues with the vehicle, and ground systems. That launch opportunity lasts from Aug. 23, to Sept. 6.