Solid rocket motors for the first five Air Force flight tests of the Northrop Grumman [NOC] LGM-35A Sentinel future ICBM are in construction, the company said on Monday. "Every propulsive element of the Sentinel missile has been prototyped and tested," according to the company. "Northrop Grumman has assembled the first three-stage Sentinel booster, verifying design, processes and technologies, and solid rocket motors for the first five flight tests are already in production." In addition, "two interstage separation tests were conducted…