The countdown was halted just over a minute before launch when a steering mechanism in the rocket
malfunctioned — "behaving strangely," as SpaceX chief Elon Musk noted via Twitter.

The soonest SpaceX can try again to launch the unmanned Falcon rocket is Friday morning, provided it can
quickly fix the problem.

NASA took the latest shipment delay in stride, while the company faced three more days of anxious waiting
for its unprecedented rocket-landing test — attempting to fly back the main booster to a platform in the
ocean.

The Dragon capsule is loaded with more than 5,000 pounds of food, science experiments and equipment for
an upcoming series of spacewalks, as well as belated holiday surprises for the six station astronauts.
The station pantry took a hit when another company’s supply ship was destroyed in a launch explosion a
few months ago.

Space station commander Butch Wilmore said the six crew members ran out of condiments a month ago, and
he’s yearning for some yellow mustard to spice up the food. He and his crewmates were watching the
launch countdown just before sunrise live via a video feed from Mission Control in Houston.

"Certainly, there’s a little bit of disappointment because it had fresh fruit and those types of
things that we’re all interested in getting," Wilmore said in an interview with The Associated
Press after the postponement. "But they’ll get off the ground here in a couple of days and it will
all be great."

SpaceX officials said one of two motors needed for rocket thrust steering of the second stage was moving
when it should have been still. If controllers had not aborted the launch, computers likely would have
done so closer to flight time, officials said.

Once the Dragon is on its way, the California-based company will try to fly the first-stage booster
rocket to a platform in the Atlantic. No one has ever pulled off such a touchdown. Normally, the
boosters are discarded at sea.

SpaceX’s founder, Musk, said recovering and reusing rockets could speed up launches and drive down costs.

The delivery was supposed to occur before Christmas, but was delayed twice in mid-December, once because
of a flawed test firing of the rocket engines. The test was repeated successfully, paving the way for
Tuesday’s try — the sixth supply run by SpaceX since 2012.

NASA is using SpaceX and another private company — Orbital Sciences Corp. — to help keep the space
station stocked. The last shipment attempt — by Orbital — ended in an explosion seconds after the
October liftoff from Virginia. Orbital has grounded its rocket fleet until next year.

Researchers, some of them school children, scrambled to get replacement experiments and equipment on this
Dragon flight.

Space station program manager Mike Suffredini said the outpost is nowhere near being short on food or
other critical supplies. Russia and Japan also have supply shipments planned this year.

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Online:

SpaceX: http://www.spacex.com/

NASA: http://www.nasa.gov/mission_pages/station/main/index.html