With less than hour before launch at 10:21 a.m. EDT, the countdown continues on schedule. The SpaceX Falcon 9 and Dragon spacecraft are timed precisely to lift off at the optimum point to reach the space station, which is zooming overhead 249 miles above Earth at 17,500 mph. That means the launch window is 1-second today, otherwise the launch team will have to make another attempt on another day.