Minuteman Solid Rocket Motor Warm Line test success

  • Published
  • By Col. Ryan Britton
  • System Program Manager
On Oct. 20, 2011, Northrop Grumman (NG) and ATK successfully ground tested a Minuteman III Stage 1 solid rocket motor for the U.S. Air Force as part of the Minuteman Solid Rocket Motor Warm Line (SRMWL) program. The refurbished Stage 1 case used in this test originally entered operational inventory in January 1961. This motor sat on strategic ICBM alert for six years at Malmstrom Air Force Base, Mont. The test was conducted at ATK's facility at Promontory, Utah. ICBM System Program Office (SPO) personnel and a number of VIPs (including Brig. Gen. Daryl Hauck, and representatives from Air Force Global Strike Command, OSD/Pentagon, U.S. Strategic Command and Congress) attended the event.

In addition to the ground test event, attendees were given a tour of Stage 1 production/manufacturing facilities at Promontory. The first stop was the motor propellant washout facility where washed out propellant is reclaimed for future usage. After reusable components are removed, the Stage 1 steel case and Stage 2 titanium case propellant are washed out. Motors are later refilled with new propellant in a casting facility, X-ray inspected and then sent to the finishing facility. The next stop on the tour was the nozzle refurbishment area where Stage 1, 2 and 3 nozzles are completed. This facility is also used to refurbish some Liquid Injection Thrust Vector Control (LITVC) components used to maneuver the booster in flight. The last stop on the tour was the hydro test bay where Stage 1 and Stage 2 motor cases are pressure tested to ensure motor case integrity.

ATK has manufactured over 4,000 motors over the life of the Minuteman program. NG/ATK recently completed a successful 10-year Minuteman Propulsion Replacement Program (PRP) that produced approximately 1,800 re-manufactured motors. The SRMWL program is a low rate production program that produces up to 30 PRP-configured motors (10 each of Stage 1, 2 and 3) over a two year production period. This effort is in support of a congressionally directed program designed to maintain the Minuteman III solid rocket motor production capabilities. SRMWL motor production started in February 2010 and will complete in May 2012. At the conclusion of the production effort, all specialized tooling, including tooling at vendors, will be preserved and stored for potential future need.

The SRMWL program maintains industrial base capabilities by producing the required motor sets and exercising the necessary engineering skills. SRMWL motors are delivered in two lots, one lot for each production year. All six motors from the first production lot have been delivered. Successful Production Quality Assurance (PQA) tests have been accomplished on a Stage 1, 2 and 3 motor. The PQA tests are required on each lot, prior to final acceptance, to ensure all motor specifications are being met. PQAs assess the motor ballistic in a full scale static firing environment. Stage 1 PQA tests are accomplished at ATK Promontory and the Stage 2 and Stage 3 motors are accomplished at Arnold Engineering Development Center because these motors need to be tested in an altitude chamber to simulate the flight environment. The Stage 2 PQA and Stage 3 PQA for the second lot will be completed in January 2012 and February 2012 respectively.