SpaceX's Dragon spacecraft is about to make history – and you can watch.
If all continues to go well, by about 10 a.m. EDT, the craft will have moved to within 10 meters of the International Space Station. Space station flight engineer Don Petitt, the mission's grappler-in-chief, will use the station's Canadian-made robotic arm to grasp Dragon.
Although the process of grappling and berthing looks to be fairly simple, it isn't, notes astronaut Catherine Coleman, who grappled the Japanese HTV on its second supply mission to the station in January 2011. She likens it to trying to pass something from one car to another – when both are traveling at interstate speeds.
On orbit, it's a Grey Poupon moment at 17,500 miles per hour between one vehicle that weighs more than 1 million pounds and another weighing a tiny fraction of that. Still, Dragon can inflict a world of hurt on the station if something goes wrong. Hence the delicate touch Petitt must apply and the slow pace he'll use to pull Dragon to the station's docking port.
Flight controllers are trying to maintain a schedule that allows Dragon's capture and berthing to take place during the sunlit portions of the station's 90-minute orbits.