 On April 17, 1958, Reaction Motors, Inc.'s acquisition by Thiokol Chemical Corporation was finalized by the approval of the stockholders and RMI was henceforth referred to as Reaction Motors Division (RMD).RMD's engine for the X-15 was completed and 199 flights were made before the X-15 project was discontinued in 1969, years past its due date and having cost more than five times its original budget.The X-15 is credited as having reached a record mach 6.72 at 67 miles above the Earth, being solely responsible for providing the data necessary to insulate and maintain the structural integrity of the Mercury spacecraft, and a host of additional technical achievements and aviation milestones.