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March 01, 2013

SpaceX Wrestles with Balky Dragon Spacecraft

By Doug Mohney, Contributing Editor

Today, March 1, 2013, SpaceX (News - Alert) launched its second paying cargo delivery flight to the International Space Station (ISS). The Falcon 9 rocket’s performance appeared to be "nominal" from all appearances, with spectacular "Rocket Cam" video from the Falcon 9 during its trip to orbit.  

The Dragon spacecraft, however, wasn't so well-mannered.

The Falcon 9 vehicle left Cape Caneveral Air Force Station at 10:10 a.m. ET, putting the SpaceX Dragon capsule into low Earth Orbit (LEO) in route to a rendezvous and berthing on March 2. 

SpaceX information went quiet shortly after Dragon separated from the Falcon 9's second at about 9 minutes into launch. According to the mission timeline published by SpaceX and NASA, solar panel deployment would have started 11 minutes into the launch, at about 10:21 a.m.

No further information came from SpaceX until 10:43 a.m. Company founder and CEO Elon Musk issued a series of tweets providing updates on Dragon's status:

10:43 a.m. -- @ElonMusk - Issue with Dragon thruster pods. System inhibiting three of four from initializing. About to command inhibit override.

11:03 a.m. -- @ElonMusk - Holding on solar array deployment until at least two thruster pods are active

11:12 a.m. -- @ElonMusk - About to pass over Australia ground station and command inhibit override

11:40 a.m. -- @ElonMusk - Thruster pod 3 tank pressure trending positive. Preparing to deploy solar arrays.

11:49 a.m. -- @ElonMusk - Solar array deployment successful

12:01 p.m. -- @ElonMusk - Attempting bring up of thruster pods 2 and 4

The Dragon has four sets of thruster pods to control and propel the spacecraft.  A 12:05 p.m. e-mail from the company said the spacecraft "experienced an issue with a propellant valve," and it was trying to bring up the remaining three pods.

Dragon needs at least two pods up and running to start a series of burns to rendezvous with the space station, but there's also a timing issue involved.  According to the mission timeline, the spacecraft would start to open up its guidance and navigation bay door at about 2 hours and 26 minutes into the flight, followed by a coelleptic burn to put Dragon into a circular orbit.

 ISS Mission Control in Houston said SpaceX may need to change the sequence of planned rendezvous burns, but the gating issue at the moment is safe and reliable operation of the those Dragon thrusters.

The spacecraft has enough power to remain in orbit for at least a couple of weeks now that the solar panels are deployed, so there's plenty of time to work through hardware issues and arrange a later – but safer – rendezvous with the station.

Edited by Braden Becker

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