In a critical prelaunch test before SpaceX's first operational cargo delivery to the International Space Station, engineers filled a Falcon 9 rocket with propellant Friday, rehearsing countdown procedures ahead of the mission's scheduled liftoff in October.

A SpaceX spokesperson confirmed the successful completion of the test.

The Falcon 9 rocket on the pad for its WDR. Credit: NASA

SpaceX completed a successful wet dress rehearsal today, a launch readiness test which simulates the actual countdown of the Falcon 9 rocket, in preparation for its first official cargo resupply mission to the International Space Station," the company posted on its Facebook page. "This mission is targeted to launch in early October."

Located in a control room south of Cape Canaveral Air Force Station, the SpaceX launch team oversaw a practice countdown that concluded with a simulated cutoff just before launch.

During the test, the Falcon 9 booster was loaded with more than 75,000 gallons of kerosene and liquid oxygen propellants.

The Falcon 9 rocket was lifted atop the launch pad earlier Friday. The upcoming mission's Dragon cargo capsule was not attached to the launcher, but remained inside the hangar at pad 40, the Falcon 9's seaside launch complex.

The Falcon 9 rocket's first stage was filled with nearly 39,000 gallons of cryogenic liquid oxygen and almost 25,000 gallons of kerosene fuel. About 7,300 gallons of liquid oxygen and 4,600 gallons of kerosene went into the second stage.

High-pressure gases were also loaded into the rocket.

Another countdown rehearsal is scheduled before launch, in which the control team will again load propellant into the rocket and ignite the booster's nine first stage Merlin engines for a few seconds, verifying their health.

The Falcon 9 being erected on the pad. Credit: NASA

The rocket is due to take off Oct. 8, and the unmanned Dragon spacecraft will reach the space station about two days later. Crew supplies, spare parts, and experiments will be carried inside Dragon's pressurized module.

SpaceX completed a test flight to the space station May, demonstrating the ability to berth with the complex and return to Earth with cargo.

The October mission is the first of a dozen flights under the auspices of SpaceX's Commercial Resupply Services contract with NASA.

The $1.6 billion contract was signed in December 2008 to provide commercial cargo delivery and return to and from the space station. Orbital Sciences Corp., a competitor to SpaceX, has a $1.9 billion deal for nine similar flights.

Each Dragon flight will carry up to 7,300 pounds of internal and external cargo to the space station and return up to 5,500 pounds of equipment to Earth.

The flight will also deploy a second-generation Orbcomm communications satellite. The first of 18 small 340-pound satellites built by Sierra Nevada Corp., the Falcon's secondary payload will relay data, transmit messages, and track ships for Orbcomm's corporate customers.