Launch of a SpaceX Falcon 9 rocket carrying an unmanned cargo ship bound for the International Space Station has been delayed from Sunday to no earlier than March 30, because of what sources described as apparent contamination that could pose problems for research hardware carried by the Dragon cargo craft.

The Dragon spacecraft is being prepared for launch inside the SpaceX hangar at Cape Canaveral. Photo credit: SpaceX
 
SpaceX engineers were preparing the rocket for launch at 4:41 a.m. EDT (GMT-4) Sunday to boost the Dragon capsule, loaded with about 4,600 pounds of equipment and supplies, on an automated flight to the International Space Station.

But the launch was put on hold, sources said, when engineers noticed contamination of some sort on the Dragon's lower unpressurized trunk section.

Two of six electrically powered payloads aboard the Dragon are mounted in the trunk section -- a first for this mission -- and engineers were concerned the contamination might "outgas" in orbit and cause problems for the station-bound hardware.

One of the payloads, the Optical Payload for Lasercomm Science, or OPALS, "will test the use of laser optics to transfer information to Earth from space," according to the NASA-SpaceX press kit. The other trunk payload includes four high-definition Earth viewing, or HDEV, cameras that will be mounted on the station's hull. Both payloads will be removed from the trunk by the station's robot arm.

By delaying the flight to the end of the month, engineers will have time to correct the problem while making way for the planned March 25 launch of a Russian Soyuz spacecraft carrying three crew members to the international outpost.

This will be the third operational commercial resupply mission carried out by SpaceX under a $1.6 billion contract with NASA that calls for at least 12 flight to deliver some 44,000 pounds of cargo to the space station.

In a brief statement, SpaceX acknowledged the launch delay for the CRS-3 mission, but did not provide any details as to what prompted it.

"To ensure the highest possible level of mission assurance and allow additional time to resolve remaining open items, SpaceX is now targeting March 30th for the CRS-3 launch, with April 2nd as a back-up," the company said in an email release. "These represent the earliest available launch opportunities given existing schedules, and are currently pending approval with the (Air Force Eastern) Range.

"Both Falcon 9 and Dragon are in good health; given the critical payloads on board and significant upgrades to Dragon, the additional time will ensure SpaceX does everything possible on the ground to prepare for a successful launch."