MINOT AIR FORCE BASE The 91st Missile Wing at Minot Air Force Base reached a historic milestone on Sept. 14 as it finished the last Propulsion System Rocket Engine upgrade for the nation's Minuteman III intercontinental ballistic missiles.
The ICBM component upgrades were part of Air Force Global Strike Command's $210 million Life Extension Program.
The Propulsion System Rocket Engine Life Extension Program at Minot began in July 2005 and consumed more than 200,000 "Rough Rider" maintainer and defender man-hours through completion.
"The LEP program is extending the life of the missile," said Master Sgt. Jeremy Trudeau, 91st Missile Maintenance Squadron missile maintenance team section noncommissioned officer in charge. "Originally this system was supposed to last 10 years and we're already at 50."
"The great maintenance makes that possible," Trudeau added.
The last missile in the Air Force to be upgraded belonged to the 91st Missile Wing, which operates, maintains and secures a fleet of 150 Minuteman III missiles located in underground launch facilities scattered across the northwest part of the state.
The Propulsion System Rocket Engine is one of seven critical and age sensitive components being refurbished in the Minuteman III to reduce life cycle costs, repair and remove age-related dilapidation, and extend the life of the weapons systems through 2020.
Propulsion System Rocket Engine is a liquid fueled fourth stage of the Minuteman III ICBM last produced in 1978. It follows the burnout of the first three solid fuel stages and provides maneuvering for post-boost re-entry systems when returning through the atmosphere.
"PSRE is liquid instead of solid, because we need it on demand to get into the upper atmosphere," said Senior Airman Doug Schimmeck, 91st Missile Maintenance Squadron cage-man.
He added it enables slower, more controlled burn of fuel to precisely position the re-entry vehicle for release on target.
The PSREs operational environment is roughly 700 miles above earth and its elegant, simple design makes an ignition system unnecessary. The PSRE's fuel (monomethel hydrazine) and oxidizer (nitrogen tetroxide) are hypergolic, meaning the two liquids will ignite upon contact with each other. They are injected together into 10 fixed roll, pitch and yaw nozzles and the gimbaled axial thrust engine, making the PSRE basically a sub-orbital space craft.
Once the previous original PSRE unit is removed from the weapons system and replaced with the new LEP unit; missile maintainers properly secure and mark the old materials as toxic before transport.
"When we get back to base, we put the old component in a PSRE container for shipment to Hill AFB," explained Airman 1st Class Daniel Peryer, 91st Missile Maintenance Squadron missile maintenance technician.
The 309th Missile Maintenance Group at Hill AFB (the MMIII depot) then modifies the old PSRE to the new LEP configuration and returns it to the spare line.
Ultimately, the PSRE Life Extension Program will sustain the Minuteman III ICBM force far past its original design life to meet our Nation's land based strategic deterrent need; a role the Minuteman III and the men and women who maintain, secure and operate it have faithfully executed for 50 years as of this October 2012.