Warren Boley has abruptly resigned as the president of the Aerojet Rocketdyne, the rocket engine manufacturer with facilities in Chatsworth. Boley has been replaced by Scott Seymour, chief executive of GenCorp, the Rancho Cordova parent of Aerojet Rocketdyne. No explanation was given by the company for why Boley left on Friday but a report by Reuters quoted sources as saying Boley and Seymour had differences about the company’s future. Boley had been president of Aeorjet Rocketdyne since July 2012 after GenCorp acquired Rocketdyne from United Technologies Inc., in Hartford, Conn., in a deal valued at $550 million. The acquisition combined Rocketdyne’s storied history of developing and building engines used in the Apollo and Space Shuttle programs with the expertise of Aerojet in rocket and missile propulsion. In an email sent to employees, Seymour thanked Boley for his contributions and expressed confidence the company would execute a strategy that will achieve its goals. “Together, we will continue to deliver results that benefit our customers, shareholders and employees,” Seymour wrote. A week before his departure, Boley was at the San Fernando Valley campus to meet with reporters to discuss projects the company was working on, including a replacement engine for the Russian-built RD-180 engine used on the Atlas V rocket to take military and spy satellites into space, and the development of hypersonic engines. In October, an Antares rocket using an Aerojet built engine exploded moments after takeoff in Virginia on a mission to take supplies to the International Space Station.