The inaugural United Launch Alliance (ULA) Vulcan rocket rolled out to the Space Launch Complex (SLC)-41 pad at Cape Canaveral Space Force Station on Dec. 6 to undergo an extensive practice countdown.

Known as a Wet Dress Rehearsal (WDR), ULA is preparing to conduct a full day-of-launch test to ensure the new rocket, pad systems and launch team are ready for the first Vulcan mission. The WDR exercises the hardware, procedures and the people to reduce the risk of a delay on launch day.

The rehearsal follows the tightly scripted sequence by rolling the Vulcan from the Vertical Integration Facility (VIF) to SLC-41, performing the entire countdown operation to fuel the rocket with cryogenic propellant and returning the vehicle to the VIF afterwards.

The countdown begins before sunrise under the guidance of the ULA launch conductor from the Advanced Spaceflight Operations Center (ASOC), located about four miles (6.4 km) from the pad.

The rocket stages are powered up, avionics tested and final preps to ground systems accomplished. That enables the ULA launch director to give approval for fueling process.

The launch team configures the Vulcan Centaur for cryogenic loading and approximately one million pounds (454,000 kg) of methane, liquid oxygen and liquid hydrogen into the rocket's tanks using the same procedures that will be executed on the actual launch day.

With the rocket filled up, permission will be given to enter terminal count at T-minus 7 minutes. The final phase of the countdown pressurizes the rocket, arms various systems and transitions the vehicle to internal power.

At T-minus 25 seconds, engineers confirm final readiness by declaring "Go Vulcan," "Go Centaur V," "Go Cert-1." The count finishes just prior to ignition time.

The rocket is then safed and cryogenic tanks drained in preparation to return to the VIF.

Once the WDR operations are satisfactorily accomplished, the encapsulated payload will be delivered to the VIF for hoisting atop the launch vehicle to begin combined preparations for launch.

The Certification-1 test flight will launch Astrobotic’s  Peregrine lunar lander on a commercial flight to the Moon and carry the Celestis memorial payload into deep space. Launch is targeted for Dec. 24.

Learn more about the Vulcan Cert-1 launch
See our Cert-1 photo album