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Jason DavisMarch 1, 2013

Dragon reaches orbit, but experiences propellant valve issue

Update: 3:45 p.m. EST

NASA has concluded a press conference updating Dragon’s status.  

Dragon is equipped with 18 Draco thrusters organized into four pods. Two pods have four thrusters, and the other two have five. The thrusters are powered by eight propellant tanks. Four contain fuel, and the other four contain oxidizer.

SpaceX CEO Elon Musk says that when Dragon was released by the Falcon 9, only one of the oxidizer tanks was showing nominal pressure. The current theory is that blockages formed in the pressurization lines leading to the oxidizer tanks, but Musk cautioned that it is too early to say for sure. SpaceX has been able to cycle valves to free the suspected blockages, and all four thruster pods are back online. As of now, only two pods are engaged, but Musk estimates this will be corrected within the hour.

This will delay Dragon’s arrival at the station by at least one day. NASA and SpaceX are optimistic the problem will be resolved in time for a Sunday berthing. If not, station managers stress there is a wide timeframe to work with, and they will not proceed until they are satisfied Dragon can show it has the necessary redundancies in place to safely approach the ISS.

Original article: 12:45 p.m. EST 

A Falcon 9 rocket and Dragon capsule soared into cloudy Florida skies Friday morning, kicking off SpaceX’s second paid cargo run to the International Space Station. The launch and subsequent release of Dragon appeared to be issue-free, likely evoking sighs of relief from SpaceX controllers that dealt with an engine failure on Falcon’s previous flight last October.
Liftoff of CRS-2


Liftoff of CRS-2
SpaceX's Falcon 9 rocket and Dragon capsule lift off from Launch Complex 40 at Cape Canaveral, Fla. on March 1, 2013. The mission, Cargo Resupply Services 2 (CRS-2), marks SpaceX's third trip to the International Space Station.

This time, however, a problem occurred on Dragon itself just after it drifted away from the Falcon’s upper stage, and SpaceX abruptly ended their launch coverage.

"It appears that, although it achieved orbit, Dragon is experiencing a problem right now," said John Insprucker, Falcon 9 Product Director. SpaceX CEO Elon Musk continued to provide updates as the situation developed.

Issue with Dragon thruster pods. System inhibiting three of four from initializing. About to command inhibit override.

— Elon Musk (@elonmusk) March 1, 2013

Holding on solar array deployment until at least two thruster pods are active

— Elon Musk (@elonmusk) March 1, 2013

About to pass over Australia ground station and command inhibit override

— Elon Musk (@elonmusk) March 1, 2013

Thruster pod 3 tank pressure trending positive. Preparing to deploy solar arrays.

— Elon Musk (@elonmusk) March 1, 2013

Solar array deployment successful

— Elon Musk (@elonmusk) March 1, 2013

SpaceX then released a statement saying a thruster propellant valve was the cause of the problem. The company said that although one thruster pod is up and running, they require two to begin a series of burns to proceed towards the International Space Station.

Dragon is scheduled to arrive at the station on Saturday, March 2. It will perform a series of height adjust burns to bring it within 2.5 kilometers of the station. Following a go-ahead from NASA, Dragon will close to 10 meters, at which point station commander Kevin Ford will grapple the spacecraft with Canadarm2, the station’s robotic arm. Flight Engineers Tom Marshburn and Chris Hadfield will also provide assistance.

Dragon’s back-to-back flight problems will likely focus renewed scrutiny on the burgeoning private spaceflight company. During Falcon 9’s CRS-1 flight on October 8, 2012, engine number one failed in dramatic fashion approximately one minute, 19 seconds into flight. Dragon’s ride to the ISS was unaffected, but a secondary payload for satellite company Orbcomm was deployed into a lower-than-required orbit. It eventually tumbled back into Earth’s atmosphere (PDF).

At a press conference Thursday, SpaceX president Gwynne Shotwell offered few details about the previous engine failure, saying the cause was a material flaw in the engine’s protective jacket. According to SpaceflightNow, Shotwell said she could not offer further details because the launch report is under review by the U.S. State Department. She also said that the exact composition of the failed material could not be disclosed due to export control laws.

Dragon receives last-minute cargo


Dragon receives last-minute cargo
SpaceX's Dragon capsule receives last-minute cargo prior to its launch from Space Launch Complex 40 at Cape Canaveral, Fla. on March 1, 2013. The private spaceflight company said the supplies included a surprise for the astronauts aboard the International Space Station.

Once Dragon is successfully grappled, it will be berthed to the station’s Harmony module. Hatch opening is currently scheduled for Sunday, and Dragon’s cargo will be unloaded over the next few weeks. NASA shows a scheduled Dragon return date of March 25.

Read more: International Space Station, commercial spaceflight

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Jason Davis

Digital Editor for The Planetary Society
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