(Adds quotes from SpaceX chief executive, booster test, in paragraphs 5 and 15-16)
By Irene Klotz
CAPE CANAVERAL, Fla., April 18 (Reuters) - An unmanned Falcon 9 rocket blasted off from Cape Canaveral Air Force Station in Florida on Friday to deliver a cargo capsule to the International Space Station for NASA.
The 208-foot-tall (63-meter-tall) rocket, built and operated by privately owned Space Exploration Technologies, or SpaceX, bolted off its seaside launch pad at 3:25 p.m. EDT (1925 GMT), darting through overcast skies as it headed toward orbit.
The Dragon cargo ship, which is loaded with about 5,000 pounds (2,300 kg) of equipment, science experiments and supplies, is due to reach the station on Sunday.
The station, a $100 billion research laboratory owned by 15 nations, flies about 260 miles (418 km) above Earth.
"The rocket flight was perfect as far as we could tell," SpaceX chief executive and founder Elon Musk told reporters at a news conference after launch.
The cargo run is the third by SpaceX under a 12-flight, $1.6 billion contract with NASA. The U.S. space agency hired SpaceX and a second company, Orbital Sciences Corp, to fly supplies to the orbital outpost after the retirement of the space shuttles in 2011.
NASA also is planning turn over crew transport from Russia to private industry by 2017.
SpaceX had planned to fly last month, but delayed the mission to review a potential contamination concern with its rocket. The issue was resolved, but then an Air Force radar system, needed to track the vehicle during flight, was damaged, sidelining all launches from Cape Canaveral for two weeks.
Another launch attempt on Monday was called off after a valve leak was found in a part of the system that separates the Falcon 9's first and second stages. The rocket was removed from the launch pad and repaired.
On Friday, the only issue was the weather, but the rain and thunderstorms that clobbered central Florida on Friday cleared in time for the Falcon 9 to lift off at the precise moment when Earth's rotation aligned its launch pad with the plane of the space station's orbit.
"Mother Nature is providing a window of opportunity today," NASA mission commentator Michael Curie said shortly before launch.
SpaceX also used Friday's launch to test technology it has been developing to recover and reuse its rockets.
The Falcon 9's first stage included extra fuel so that some of its engines could reignite as the booster fell back toward Earth, slowing its descent.
The vehicle also was outfitted with four deployable landing legs to help stabilize it for a potential vertical touchdown on the ocean before toppling over.
Results of the test were still pending, but Musk said he did not think the booster splashed down intact.
Given the rough seas and experimental nature of the test, "I wouldn't give it high odds," Musk said.
Eventually, SpaceX hopes to fly its Falcon rockets back to land for refurbishment and reuse. (Editing by Eric Walsh and Mohammad Zargham)