S paceX is still reeling from its September 1 launch pad explosion, which irretrievably damaged a Falcon 9 rocket and consumed a very important Facebook-sponsored satellite — all because of what was likely an issue in loading cryogenic helium into the booster’s upper stage liquid oxygen tank. The company is determined to launch rockets again before the end of the year, but there hasn’t been much clue as to whether it was making any real progress. Well, we finally have some encouraging news. On Sunday, someone posted to reddit a slew of images and a short video of a Falcon 9 rocket on Interstate 10 in Arizona, presumably en route from SpaceX’s testing grounds in McGregor, Texas, to Vandenberg Air Force Base in southern California. This is almost certainly the booster that will be used to launch 10 satellites owned and operated by Virginia-based communications company Iridium. Later that same day, Iridium’s chief executive, Matt Desch, added some confirmation...