Global Security Newswire
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New Details Emerge About U.S. Nuclear Missile Test Failure
WASHINGTON -- The U.S. Air Force is beginning to narrow down possible explanations for a rare flight test failure last month of one of its Minuteman 3 ICBMs, but it appears that the precise cause has not yet been determined (see GSN, July 27).
An "anomaly" occurred during the final powered stage of the July 27 launch, when the missile was being propelled by its post-boost motor, according to Air Force Global Strike Command officials.
This was the first flight test failure in two years and only the second such incident since 1998, when the current Minuteman 3 configuration was fielded, said GSC spokeswoman Michele Tasista, speaking on behalf of a team of experts at the Louisiana-based command.
The nation maintains 450 of the nuclear-armed, strategic-range ballistic missiles on round-the-clock alert in underground military silos in three states: Montana, North Dakota and Wyoming.
Minuteman 3 was first fielded in 1970 but has undergone a number of technology updates and refurbishments over the past four decades. Its boost and post-boost systems have a nearly 93 percent success rate in flight tests during that time period, Tasista said.
Global Strike Command directs day-to-day missile readiness operations and oversees flight tests roughly twice a year of ICBMs pulled randomly from launch facilities and immediately replaced by operational spares.
The Minuteman 3 tests are conducted over the Pacific Ocean without a nuclear payload and are intended to demonstrate that the missile continues to function properly. Each trial costs about $10.3 million, or twice that amount if the expense of the missile is included.
Global Strike Command has not described the anomaly, saying only that the shot was "terminated due to potential safety concerns along the predicted flight path."
The command officials also would not say whether initial findings appear to indicate a guidance problem, a faulty propulsion system or some other glitch. After observing the abnormality, military controllers aborted the flight with a self-destruct mechanism five minutes after the missile launched from Vandenberg Air Force Base in California.
"We can't speculate on the cause of the anomaly, which is under investigation," Tasista and her team said in response to questions from Global Security Newswire.
The Minuteman 3's Propulsion System Rocket Engine -- a liquid-propellant stage used for positioning nuclear-equipped re-entry vehicles precisely towards their intended targets -- has "a perfect safety and performance record in over 200 flights spanning 30 years of successful operational deployment," the motor manufacturer, Aerojet, boasts on its website.
The liquid stage ignites only after three solid-fuel rocket motors boost the missile into space. Upon separating from a bulkhead, one or more re-entry vehicles coast on a ballistic trajectory and return into the atmosphere en route to their targets.
Command officials confirmed that the Propulsion System Rocket Engine used in the failed ICBM test last month was refurbished in 2005. An ongoing service-life extension effort is being conducted to ensure that all the liquid-fuel motors installed in Minuteman 3 missiles can remain in service through 2020, according to Aerojet.
A malfunctioning guidance system on the Minuteman 3 might be a more likely cause of the test failure, according to defense experts.
"We have never had a problem with the post-boost [propulsion] system," said one retired ICBM commander. "So I would find it hard to believe that's the culprit."
The former officer spoke on condition of not being named because of military sensitivities involved in discussing technical details about nuclear weapons.
Guidance engineers and analysts from Minuteman 3 contractors Boeing and Northrop Grumman sit on the Global Strike Command board investigating the July incident -- a possible indication that the service suspects a guidance-system malfunction -- while liquid rocket engine manufacturer Aerojet is notably absent.
Boeing performs maintenance on the Minuteman 3 "missile guidance set" and in 2009 completed a seven-year program to upgrade the missile's guidance system. Northrop Grumman leads the Air Force's ICBM contractor team.
The Minuteman 3's guidance system includes a computer that directs the weapon system during flight, keeping the missile on course to deliver warheads to their designated endpoints, according to the Air Force. During the liquid-fuel stage, the guidance set is intended to maneuver the delivery system to predetermined points where re-entry vehicles separate for the remainder of their ballistic trajectories.
Under the Defense Department's 2010 Nuclear Posture Review, the Air Force is in the process of reducing each Minuteman 3 to a single warhead. The missile has the capacity to carry up to three warheads.
The only other flight test failure for the current configuration of the Minuteman 3 occurred in August 2009, when a trial was similarly terminated after launch. The GSC officials were unable by press time to say what caused the 2009 failure.
The command's investigation board is chaired by Lt. Col. Trevor Hazen, an operations officer with the 576th Flight Test Squadron, based at Vandenberg.
He is additionally joined on the panel by other Air Force personnel, including representatives of the 30th Space Wing Safety unit, also based at Vandenberg, and the Air Force Nuclear Weapons Center, which is headquartered at Kirtland Air Force Base in New Mexico.
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