The Air Force tested an unarmed Mk21A reentry vehicle Oct. 9, launching it aboard a Minotaur I rocket from Vandenberg Space Force Base, Calif., as part of the vehicle’s development. The flight was an in-flight environmental test supporting development of the Mk21A, a new reentry vehicle that the Air Force plans to integrate onto a future Sentinel intercontinental ballistic missile (ICBM), the service said in a press release. Lockheed Martin [LMT] is currently under contract for the Mk21A’s engineering and…