Raytheon [RTN] this week said its Small Diameter Bomb (SDB) II flight test program is in full swing and “advancing steadily” toward Milestone C in fourth quarter fiscal year 2014, after a key Senate panel recently said it wanted the Air Force to brief the congressional defense panels on its entire SDB program as it approached critical milestones.

Raytheon spokeswoman Holly Caldwell said Tuesday of the nine guided test vehicles (GTV) and two live fire tests required for Milestone C, four guided test vehicles have been flown to verify closed-loop performance of the entire system. Caldwell said GTV-1 and GTV-3 scored direct hits on targets moving at operationally representative speeds.

Boeing’s Small Diameter Bomb. Photo: Air Force.

The Senate Armed Services Committee (SASC) said in June in its FY ’14 defense authorization report the SDB II (GBU-53/B) flight test program was temporarily suspended due to a flight test failure, but has since resumed. Caldwell confirmed the suspension and said the GTV-2 and GTV-4 flight tests experienced “degraded performance,” but in both cases, root causes were identified and corrective actions were implemented into the production design. Two subsequent flight tests, Caldwell said, have validated the corrections incorporated to date.

“The discoveries made during the flight test program are fully resolvable weapon development issues,” Caldwell said. “Although the lessons learned during flight tests have required us to adjust the previously planned Milestone C, SDB II is still on track for Milestone C in FY ’14. Both Raytheon and the government are committed to a successful system verification review and Milestone C in FY ’14.”

SASC said in its report that it originally anticipated Milestone C in August and that the service plans to start low-rate initial production (LRIP) of SDB II in 2014. Caldwell said Wednesday fourth quarter FY ’14 was the new Milestone C goal. Requests to the Air Force for comment were not returned by press time.

The Small Diameter Bomb (GBU-39B), developed by Boeing [BA], is an extended range, all-weather, day-or-night, 250-pound class guided munition designed to hit stationary targets. SDB II, developed by Raytheon, is designed to hit moving targets. Raytheon in July 2012 successfully hit a moving target with SDB II during its first guided flight test.

Raytheon has developed a tri-mode seeker (radar, infrared and semi-active laser) for SDB II, adding on to the first SDB’s use of global positioning system (GPS) and inertial navigation system (INS) data to achieve required precision. These new sensors are intended to provide automatic target recognition features for striking mobile targets, like tanks, vehicles and mobile command posts, SASC said.

SASC said it is aware of a possible modification to SDB I that would add a semi-active laser (SAL) sensor, which could provide some, but not all, of the potential SDB II capability against moving targets. The committee urged the Air Force to consider this option if there were additional SDB II flight testing difficulties that could cast doubt on the system.

Caldwell said adding a SAL sensor to an existing coordinate attack weapon would not address the weather and range limitations laser-designated munitions face. SDB II is able to kill fixed, stationary and mobile targets in adverse weather out to standoff ranges through its multiple targeting systems, using millimeter-wave radar, imaging infrared, GPS coordinate attack and SAL, Caldwell said.

SDB II is also equipped with a dual-band weapon data link (Link 16 and Ultra High Frequency), Caldwell said, which provides the capability to maintain communications between the weapon and aircraft, ground personnel or third-party controllers. This allows for providing updates, target changes and system status, Caldwell said.

SASC said the briefings should include the current status of the SDB II test program, potential gaps in capabilities if SDB II testing were to be delayed, an examination of the mix of SDB I and SDB II weapon capabilities and costs and a recommended way ahead for SDB procurement (Defense Daily, July 1).