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SpaceX overcomes thruster problems with cargo ship

After more than six hours of suspense, engineers are optimistic they've resolved trouble with thrusters on the Dragon cargo ship, clearing the way for a rendezvous with the International Space Station.

William Harwood
Bill Harwood has been covering the U.S. space program full-time since 1984, first as Cape Canaveral bureau chief for United Press International and now as a consultant for CBS News. He has covered more than 125 shuttle missions, every interplanetary flight since Voyager 2's flyby of Neptune, and scores of commercial and military launches. Based at the Kennedy Space Center in Florida, Harwood is a devoted amateur astronomer and co-author of "Comm Check: The Final Flight of Shuttle Columbia." You can follow his frequent status updates at the CBS News Space page.
William Harwood
5 min read

A SpaceX cargo ship loaded with more than a ton of spare parts, science equipment, and crew supplies bound for the International Space Station thundered safely into orbit today. But vexing trouble with the capsule's rocket thrusters quickly turned the $133 million flight into a high-tech cliff hanger.

Six-and-a-half hours after launch, follwoing extensive troubleshooting and analysis, it appeared company engineers had resolved the problem, bringing all four sets of thrusters on line and setting the stage for a delayed rendezvous with the space station.

But it was touch and go in the early stages of a high-stakes drama for the emerging commercial space industry.

Following a picture-perfect launch and a near-flawless climb to space, the SpaceX Dragon cargo capsule was released into its planned preliminary orbit. But flight controllers quickly found themselves faced with a sticky valve or possibly blockage in a helium pressurization line that prevented three of the ship's four sets of maneuvering thrusters from operating.

A SpaceX Falcon 9 rocket blasts off from the Cape Canaveral Air Force Station, kicking off the second of at least 12 commercial space station resupply missions under a $1.6 billion contract with NASA. SpaceX

Unable to orient itself toward the sun or carry out any other major maneuvers, deployment of the ship's solar panels was delayed, leaving the spacecraft in "free drift" on battery power alone.

Elon Musk, SpaceX founder and chief designer, eventually decided to deploy the arrays anyway while engineers studied what to do about the thruster problem.

By repeatedly opening and closing valves in the thruster plumbing, engineers were able to "pressure hammer" the system, eventually freeing up whatever was causing the original problem and restoring the propellant system to the normal pressures. Musk said:

It looks like there was potentially some blockage in the oxidizer pressurization (system). It looks like we've been able to free that blockage, or maybe a stuck valve. We've been able to free that up by cycling the valves, essentially pressure hammering the valves, to get that to loosen. It looks like that's been effective.

All the oxidizer tanks are now holding the target pressure on all four (thruster) pods. I'm optimistic we'll be able to bring all four of them up and then we'll work closely with NASA to figure out what the next step is for rendezvousing with space station.

Shortly after the briefing concluded, engineers reported all four sets of thrusters were back on line and that testing was underway to verify the health of the system. But it appeared unlikely the Dragon could reach the outpost before Sunday at the earliest.

Space station Commander Kevin Ford took the delay in stride, telling a NASA flight controller: "That's space exploration for you."

"We sometimes have problems and work through them, and that's how you learn," he said. "If not tomorrow, maybe a couple of days down the road we'll get it licked."

The Dragon cargo ship's Falcon 9 rocket, also built by Space Exploration Technologies, roared to life at 10:10 a.m. ET, kicking off the second in a series of at least 12 commercial space station resupply missions under a $1.6 billion contract with NASA.

Trailing a torrent of flame from its nine Merlin 1C engines, the 157-foot-tall rocket majestically climbed away from the Cape Canaveral Air Force Station, launching almost directly into the plane of the space station's orbit onto a trajectory paralleling the East Coast of the United States.

During the first operational SpaceX resupply flight last October, one of the booster's first stage engines suffered a combustion chamber rupture, prompting an early, but safe, shutdown. The other engines fired longer than planned to make up for the shortfall, and the Dragon cargo ship was released into the intended orbit.

This time around, all nine engines appeared to work normally, and the first stage fell away on time about three minutes after liftoff. The second stage, powered by a single Merlin engine, then continued the climb to space.

Live television views from a camera mounted at the base of the second stage showed the engine nozzle glowing cherry red against the limb of the Earth as the rocket neared orbit. A few moments later, another television camera showed the Dragon capsule as it was released from its booster about nine minutes and 46 seconds after liftoff.

The capsule's two solar arrays were expected to deploy two minutes later.

"It appears that although it achieved Earth orbit, Dragon is experiencing some kind of problem right now," John Insprucker, SpaceX's Falcon 9 product manager, said during a company Webcast. The company ended its coverage a few moments later.

The Dragon spacecraft was released into an initially elliptical orbit with a high point of around 200 miles and a low point of around 120 miles. Because of the thruster problems, SpaceX flight controllers were not able to begin a series of rendezvous rocket firings on time.

As a result, the capsule's arrival at the station was delayed until at least Sunday and possibly longer.

Whenever it gets there, the flight plan called for the Dragon to pull up to within about 30 feet of the huge lab complex and then to stand by for capture Ford, operating the lab's robot arm from a robotics work station in the multi-window Cupola compartment.

The astronauts typically handle berthing chores, carrying out complex multi-joint maneuvers to move the captured spacecraft to its docking port on the Earth-facing side of the station's forward Harmony module.

SpaceX Dragon's quest to the space station (pictures)

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But this time around, ground controllers at the Johnson Space Center in Houston were expected to take over, sending commands to remotely operate the arm through berthing to demonstrate their ability to carry out complex arm procedures and to give the astronauts a bit of a break during a very busy day.

The Dragon capsule is packed with some 2,300 pounds of equipment and provisions, including 178 pounds of crew supplies; 300 pounds of space station hardware, including replacement components for the lab's carbon dioxide removal system; and more than 700 pounds of science gear, including a pair of Glacier freezers and experiment components.

A spacewalk equipment handling fixture called a grapple bar is mounted in the Dragon capsule's unpressurized trunk section. The station's robot arm, again operated by flight controllers in Houston, will be used a few days after berthing to extract the grapple bar assembly and stow it on the station's exterior for future use.

Assuming a successful berthing, Ford and his crew mates plan to repack the capsule with 1.5 tons of no-longer needed gear, components that need refurbishment or failure analysis, and experiment samples that are needed by scientists back on Earth.

The return manifest includes 209 pounds of crew equipment; 1,455 pounds of science gear, including a Glacier freezer and cold bags loaded with experiment samples; and 884 pounds of space station hardware.

The SpaceX Dragon capsule is the only space station cargo craft designed to bring cargo back to Earth, a critical capability that was lost when NASA's space shuttle fleet was retired in 2011.

The manned Russian Soyuz spacecraft that carry three-person crews to and from the space station can only bring back a few hundred pounds of cargo. All other station vehicles -- unmanned Russian Progress supply ships and European and Japanese cargo craft -- burn up during re-entry.