Image of the Day: ISS Robotic Arm Completes 1st-Ever Hookup with SpaceX’s Dragon –Launching Commercial Space Era



The International Space Station's crew reached out today with a robotic arm to grab SpaceX's Dragon cargo capsule and brought it in for the orbital outpost's first-ever hookup with a commercial spaceship.The unmanned capsule is carrying 1,000 pounds of supplies on this unprecedented test flight. If the long-range plan unfolds as NASA hopes, U.S. astronauts could be shuttled back and forth on the Dragon or similar spacecraft within just a few years.

"Looks like we got us a dragon by the tail." The relief in the words of U.S. astronaut  Don Pettit was audible as he grabbed the uncrewed SpaceX Dragon spacecraft using a robotic arm on board the International Space Station today. Pettit used the space station's 58-foot robot arm to snare the gleaming white Dragon after a few hours of extra checks and maneuvers. The two vessels came together while sailing above Australia.

The docking followed a morning in which the spacecraft underwent a series of control tests – such as approaching the ISS and then retreating a precise distance to order – to prove that it is controllable in an emergency, to prevent a repeat of the 1997 accident when a Russian Progress cargo freighter collided with the Mir space station (video) and caused a dangerous depressurisation and power loss.

"Dragon started backing away as it was meant to do, reaching a 250-metre hold position," said NASA on its online TV channel. It successfully completed follow-up manoeuvres to 36 metres, then 30 metres – using thermal imaging and laser radar (LIDAR) data to double-check its range. For a time the thermal and LIDAR range data were not in agreement – but after the numbers converged Dragon was finally given a "go" to berth with the ISS.

A standard ISS unit called a power data grapple fixture allows the arm's grippers to safely grasp objects to which it is attached. Indeed, a series of such fixtures dotted around the station allows Canadarm2 to self-relocate, moving end-over-end like an inchworm. A grapple fixture attached to Dragon allowed the Canadarm2 to grasp it.

Once Dragon was held fast, the ISS crew steered the arm to orientate the capsule correctly and drew it in to dock Dragon with the standard non-Russian docking hatch called a Common Berthing Mechanism. On Saturday, the hatch will be opened to the pressurised capsule so the ISS crew can unload the cargo – which as you can see from the flight manifest includes astronaut rations, clothes, laptops and a bunch of zero-g experiments.

Dragon's advantage if that it is designed to be recoverable via an Apollo-style ocean splashdown. Re-entry, and a splashdown with a return cargo intact, will be SpaceX's next challenge in two weeks' time.

The Daily Galaxy via NASA, and AP

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