SpaceX’s second Dragon Commercial Resupply Services mission to the International Space Station encountered a thruster issue that slowed the scheduled critical deployments of the capsule’s solar arrays and rendezvous maneuvers, following an otherwise successful March 1 liftoff.

The effect of the difficulties on plans for a rendezvous with the 250-mi.-high, six-person orbiting science laboratory and on grapple operations scheduled for early March 2 were unclear, said Pat Ryan, a NASA spokesman in Mission Control.

The Dragon’s power-generating solar panels were extended at 11:49 a.m. EST, with commands issued from an Australian ground station, nearly 90 min. behind schedule, according to statements from Elon Musk, SpaceX founder and chief designer. NASA confirmed the statement issued by Musk via Twitter.

Dragon encountered an unspecified problem with a propellant valve after settling into an initial 124 X 202-mi. orbit, following its ontime liftoff at 10:10 a.m. EST from Cape Canaveral. The difficulty prevented three of four thruster pods on the supply capsule from operating, said SpaceX spokeswoman Christina Ra.

“Once we get at least two pods running, we will begin a series of burns to get to station,” Ra said in a post-launch advisory.

Musk said his Hawthorne, Calif.-based control team was attempting to override flight control system inhibits that were preventing three of the four thruster steering systems from initializing.

The scheduled 25-day mission is the second by SpaceX under a $1.6 billion NASA cargo services contract awarded in late 2008. The first mission, successfully launched in October, followed a six-year, NASA-led Commercial Orbital Transportation Services (COTS) partnership. The COTS partnership transitioned to commercial operations following an initial Dragon visit to the station in May 2012.

NASA astronauts Kevin Ford and Tom Marshburn were have been preparing to position themselves in the station’s U.S. segment Cupola observation deck, ready to reach out with the 58-ft.-long Canadian robot arm to grapple the supply vessel as soon as March 2 at 6:30 a.m. EST.