Capturing the Dragon: SpaceX's uncrewed cargo ship arrives at the International Space Station

Monday, January 12, 2015, 4:46 PM - After a flawless launch into orbit early Saturday morning, SpaceX's Dragon cargo ship arrived at the International Space Station ahead of schedule, and is now securely berthed for a month-long stay.

It was 5:54 am Eastern Time when ISS commander Butch Wilmore maneuvered the Canadarm 2 into position and took hold of the Dragon, just one minute after station sunrise. Given that the uncrewed spacecraft pulled alongside the station, keeping a distance of just 30 metres, well ahead of schedule, the crew went ahead with the berthing procedure a full 35 minutes earlier than expected, only waiting for sunrise to give them enough light to work by. While it wasn't until 8:54 am before the Dragon was berthed (a necessarily slow process when you're reeling in a multi-ton object in low-Earth orbit), the spacecraft is now securely bolted to the station's Harmony module for the next four weeks or so.

This fifth flight to the ISS by the Dragon, and the fourth delivery mission by SpaceX, brings with it a load of nearly two and a half tons of cargo for the station crew.

Included in this particular delivery are support materials for over 250 science experiments, food and station supplies, and since this launch was originally scheduled to happen in time for a delivery before Christmas, the crew also has presents on board that they've been waiting to receive.

One of the science experiments included is one that was original on board the Orbital Sciences rocket that exploded just seconds after launch back in late October. This crystal growth experiment, designed by a group of Kamloops elementary school students, got this second chance to fly into orbit, and will now join the rest of the experiments being performed by the station crew. 

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The only part of the launch that didn't go as well as many had hoped was the attempted landing of the rocket's first stage on a barge at sea. According to Elon Musk's Twitter account, the rocket managed to find the barge and attempt the landing, but came in too fast, hit the barge hard and broke up. One problem noted by Musk was that the set of fins controlling the rocket's motion as it landed ran out of hydraulic fluid, despite performing extremely well during the transition between hypersonic speeds and subsonic speeds. SpaceX's next launch, which is scheduled for February, is expected to carry 50 per cent more hydraulic fluid than is needed, providing an effective margin for error for the next attempt.

An important part of this cargo run is a new NASA Earth-observing mission known as CATS, or the Cloud-Aerosol Transport System. Using lidar - light detection and ranging - this sensor will provide high resolution data on clouds, smog and dust, for use by scientists on the ground in weather, climate and air quality forecasts.