Private space transportation outfit Space Exploration Technologies Corporation, or, SpaceX, canceled its planned cargo run to the International Space Station today with about an hour left until its scheduled 4:58 p.m. EDT lift-off, after a helium leak was discovered in the rocket.

The launch of the Falcon 9 transport vehicle rocket and Dragon cargo was called off by mission officials after engineers reported the rocket's first stage was leaking helium, according to a report by Reuters.

The mission's next launch window will be this coming Friday at 3:25 p.m., presuming the leak is fixed.

Third of 12 missions under the company's $1.6 billion contract with NASA, the trip had been delayed a few times, once because of a problem with the Air Force radar system used to track space flights, another over rocket contamination concerns.

Yet another potential postponement was mulled over the weekend, after the failure of a computer that controls key systems aboard the space station, including the orbiting lab's solar wing panels and a moveable base for the robot arm.

Despite the fact station crew members will need to venture outside the station to effect the needed repairs to the computer unit, mission managers opted to go forward with today's planned launch.

Aside from holding up the delivery of station supplies, the scrubbed launch also delays SpaceX's highly-anticipated test of four newly-installed landing legs on the Falcon 9, which is expected to lead the flight aerospace industry into a new age of recoverable and reusable rockets.

After it separates from the upper stage and Dragon capsule, the rocket is expected to reignite its engines to slow its drop to Earth.

Although this first time around the rocket stage will be programmed to position itself for a vertical touchdown into ocean waters, SpaceX foresees its Falcon rockets returning from missions with ground landing, after which they will be refurbished for future missions.

Besides the new landing extremities, the rocket's first stage also holds extra fuel for its planned controlled descent.

SpaceX officials reportedly expect less than a 40 percent chance the rocket stage will return and land successfully.

"This is a really difficult maneuver," SpaceX Vice President Hans Koenigsmann said during an April 13 news conference.

Orbital Sciences Corp. out of Virginia, which is working under a separate $1.9 billion agreement with the space agency, is preparing to launch its second resupply mission in June.