Elon Musk's SpaceX [SPCX] has made payload fairings for its rockets, including Falcon 9, at SpaceX's Hawthorne, Calif. plant, and now competitor United Launch Alliance (ULA) is bringing its fairings build in house as well--an effort that may achieve savings from vertical integration of manufacturing. ULA, which is the prime for the Vulcan Centaur, said on Wednesday that it has forged an agreement with Beyond Gravity USA, Inc., to move production, sustaining engineering and development work for Vulcan's payload fairings…