More information has recently become available on the “Unexpected Energetic Event” that was apparently responsible for the failure of the first SM-3 Block IB intercept attempt (FTM-16) in September 2011.  The cause was a failure in the SM-3 interceptor’s third rocket stage motor.    Despite assurances that this component, which is common to both the IA and IB variants of the SM-3 interceptor, had performed successfully many times previously, it also apparently experienced an “anomaly” in its previous test (FTM-15, April 14, 2011, of an SM-3 IA) serious enough to temporarily halt deliveries of new interceptors.  In the most recent test, a May 2012 repeat of September’s failed intercept, the part of the third stage booster (the second pulse) that had failed previously was not used, and the interceptor hit its target.

 “Unexpected Energetic Event” during the FTM-16 intercept test, September 1, 2011.[1]

Background

Under the Obama Administration’s European Phased Adaptive Approach, the U.S. Navy plans to deploy a series of increasing capable interceptors as part of its Aegis Ballistic Missile Defense (BMD) system.  At least the first two types of these interceptors will use a SM-3 missile equipped with a small homing kill vehicle.   The first version, the SM-3 Block IA, is currently deployed and operational in the Mediterranean.  The next version, the SM-3 Block IB is currently undergoing testing with the goal of being deployed by about 2015.

The figure below compares the SM-3 Block IA with the new Block IB.  The new version has improved kill vehicle (a two-color seeker and a new divert system) and guidance system, but otherwise the two interceptors are essentially identical.  In particular, the third stage rocket booster is common to both interceptors (this is labeled “MK136 TSRM” on the figure).  This third stage has a two-pulse capability, that is, it can put out a pulse of thrust, and then after a delay, produce a second thrust pulse. 

Aegis Block IA and IB Interceptors[2]

 There have been three intercept tests of SM-3 interceptors since the beginning of 2011 (there have been many previous intercept tests of the SM-3 Block 1A, most of them successful).  These are:

FTM-15, April 14, 2011.  Successful intercept using SM-3 Block 1A.

FTM-16, September 15, 2011.  Failed intercept using SM-3 IB.  This was the first intercept test of an SM-3 IB.  (Sometimes referred to FTM-16E2).

FTM-16E2a, May 9, 2012. Successful intercept with a SM-3 IB.

Discussion.

The FTM-15 test, the most recent test of a Block IA interceptor, was initially reported as an unqualified success, with indications being that all components performed as designed.[3]  However, subsequent analysis of the test data apparently revealed an “anomaly” that while not preventing an intercept was serious enough halt deliveries of new SM-3 IA interceptors.  

FTM-15 Geometry. [4]

According to the DOT&E 2011 Annual Report (published in early 2012):

“Anomalous behavior was observed during the flyout of the SM-3 Block IA interceptor in FTM-15, but the anomaly did not preclude an intercept.  If the anomaly occurred under different engagement conditions, it could have had an impact on the success of the engagement.  However, it should be noted that the anomaly was not observed in any of the other 21 previous SM-3 flyouts.”[5]

According to an April 2012 GAO Report, “As a result of an anomaly in the latest SM-3 Block 1A flight test — FTM 15 in April 2011 — MDA halted acceptance of SM-3 Block IA deliveries.”[6] At the time of the GAO report, 12 SM-3 IA missiles were being held at the production factory.

On September 1, 2011, MDA conducted the first intercept test of the new Block IB interceptor, FTM-16.[7]  It is unclear (to me) if the cause of the April test failure was known at this point — the 2012 GAO and DOT&E reports indicated that the review of the test had not been completed at the time they conducted their assessments.  In this September test, the interceptor failed to hit its target, and the GAO indicated that production of Block IB interceptors was subsequently slowed while the investigation of the failure was conducted.

The first public indication (that I know of) of the cause of the failure FTM-16 is the picture of an “unexpected energetic event” at the top of this post.  This picture was part of a briefing slide shown by MDA Director Lt. Gen. Patrick O’Reilly at a March 2012 conference and is posted on the MDA website.[8] 

The April 2012 GAO report then revealed that: “The first SM-3 Block IB developmental flight test failed in September 2011, and an anomaly occurred in an April 2011 flight test of the SM-3 Block IA.  The flight test failure and the test anomaly occurred in components that were shared between the SM-3 Block IA and IB.”

In its May 7, 2012 issue, Aviation Week and Space Technology reported that the September test had “failed owing to a solid-rocket fuel burn through the missile casing, according to industry officials.  This resulted from a specific flight profile, which they say will be avoided by a change to the missile’s software.”[9]

On May 9, 2012 the second intercept test (FTM-16E2a) of the SM-3 Block IB was conducted and the interceptor reportedly successfully intercepted its target.[10]

Following this test it was reported that the failure of the September test was associated with a problem with the second pulse of the third stage.  According to Rear Adm. Joseph Horn, the Aegis BMD Program Executive, the first pulse performed normally, but then just before the kill vehicle was to be released, the booster exploded.[11]

How was this problem solved before the May 2012 test?  According to Admiral Horn: “We took the delay out and never fired the second pulse on that third-stage rocket motor”