{"id":39899,"date":"2013-03-02T20:32:58","date_gmt":"2013-03-02T12:32:58","guid":{"rendered":"https:\/\/wp-productionenv-bjg9h2g2bgg5b8aa.southeastasia-01.azurewebsites.net\/news\/resilient-crs-2-dragon-successfully-berthed-on-the-iss\/"},"modified":"2013-03-02T20:32:58","modified_gmt":"2013-03-02T12:32:58","slug":"resilient-crs-2-dragon-successfully-berthed-on-the-iss","status":"publish","type":"post","link":"https:\/\/starpath.global\/news\/resilient-crs-2-dragon-successfully-berthed-on-the-iss\/","title":{"rendered":"Resilient CRS-2 Dragon successfully berthed on the ISS"},"content":{"rendered":"

Back to full health, SpaceX\u2019s Dragon spacecraft was captured and then berthed by the Canadarm 2 on the International Space Station (ISS) Sunday morning. Arriving just one day later than planned \u2013 due to required troubleshooting with the spacecraft\u2019s propulsion system \u2013 Dragon marked its third arrival at the orbital outpost.<\/p>\n<\/p>\n

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CRS-2 Status \u2013 Article will be updated throughout FD-3:<\/p>\n

Dragon was launched out of Cape Canaveral\u2019s Space Launch Complex 40 (SLC-40) at 10:10am local time on Friday, carried uphill by the Falcon 9 rocket.<\/p>\n

Only one minor issue was reported prior to launch, namely a low temperature reading on the flight computer \u2013 caused by a combination of chilly conditions in the region and the \u201ccold soak\u201d from the LOX tank on the Second Stage during the countdown.<\/p>\n

\"PadThe Falcon 9\u2019s ascent was nominal, with just one reference to a Ground Support Equipment (GSE) issue after lift-off, relating to a small fire on the pad \u2013 as is usually seen when the Falcon 9\u2019s plume catches the pad\u2019s umbilical line on the strongback.<\/p>\n

Successfully completing its job by deploying the Dragon without a hitch, the Falcon 9 showed it had overcome the issues of the CRS-1 (SpX-1) launch, which resulted in shut-down of Engine 1 during ascent. The success will add confidence to SpaceX\u2019s internal post flight investigation procedures, which included Non Destructive Evaluation (NDE) testing on their flight hardware.<\/p>\n

NASA mission patches<\/path>Rocket launch schedules<\/path>Space Shuttle<\/path>\n

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However, a new challenge was soon to face SpaceX engineers, just moments after Dragon was shown to have successfully separated from the Falcon 9 Second Stage via onboard cameras.<\/p>\n

\"TwoThe problem was seen in the propulsion system \u2013 a set of four \u201cquads\u201d of thrusters on the Dragon, vital for attitude control and required burns en route to its destination.<\/p>\n

As flashed up on L2\u2019s CRS-2 mission coverage, the issue was seen during priming phase, as Dragon prepared to fire up its thruster systems by pressurizing the fuel tanks via the injection of gaseous helium.<\/p>\n

\u201cPost-separation, Dragon\u2019s propellant system opened valves between the Helium tanks and the Fuel and Oxidizer tanks to pressurize the system. All four fuel tanks were observed to pressurize as expected. However, only oxidizer tank 1 showed nominal pressure response,\u201d the notes added.<\/p>\n

With three of the four quads at a lower than required pressure, only \u201cQuad 1\u201d remained online, which was not enough to ensure Dragon could maintain attitude control.<\/p>\n

\u201cOx tanks 2,3, and 4 did not indicate a pressure increase. Due to this failure to pressurize, three of Dragon\u2019s four prop quads were unusable. Dragon\u2019s attitude drifted while troubleshooting occurred, and solar array deploy was delayed.\u201d<\/p>\n

\"DragonAlthough the initial plan was to deploy Dragon\u2019s solar arrays once two Quads were available, SpaceX decided to unfurl the arrays with only one Quad working. This proved to be helpful for the unstable Dragon, with SpaceX CEO Elon Musk describing it as not unlike an ice skater stretching out her arms during a spin maneuver to slow the rotation.<\/p>\n

Meanwhile, controllers continued to evaluate the propulsion system, concluding it was was being caused by either a blockage in the helium line, or a sticky check valve. The solution was to \u201cjack-hammer\u201d the valves in the system by commanding them to cycle on and off several times in succession. This proved to be successful.<\/p>\n

\u201cTroubleshooting involved cycling the helium isolation valves between the He and Ox tanks 2-4. This allowed \u201cslugs\u201d of pressure to flow through the regulators and downstream to in-series check valves that were suspected to be the cause of the blockage,\u201d added the notes. \u201cAfter several cycles, the Quad 4 Ox tank suddenly rose to its expected pressure, indicating the blockage had cleared.\u201d<\/p>\n

\"DragonWith two Quads (1 and 4) now available, Dragon regained attitude control. Shortly after, the remaining two Quads (2 and 3) saw their tank pressures eventually return to normal.<\/p>\n

Now with all four Quads, a much happier Dragon conducted a test burn of around 30 seconds to observe the performance of its prop system.<\/p>\n

\u201cAll appeared well, as oxidizer tank pressures remained stable and did not decay, as might occur with restricted helium flow,\u201d the notes continued. \u201cThis was followed shortly by a four minute burn, during which the prop system again appeared to function nominally.\u201d<\/p>\n

Notably, the delay rescheduled the key Coelliptic Burn, resulting in the Dragon being unable to arrive at the ISS on Saturday. However, thanks to the speedy mitigation of the problem by the SpaceX team \u2013 and what appears to be good propellant margins \u2013 Dragon successfully negotiated a path to be in a stance for a Sunday berthing.<\/p>\n

See Also<\/h4>\n