Raytheon is in the final stages of preparing the GBU-53/B Small Diameter Bomb II for a system verification review to be undertaken within the coming weeks in advance of the U.S. government’s Milestone C review. If the review is passed successfully, a decision to enter the low-rate initial production (LRIP) phase is expected.
Weighing just over 200 pounds, the SDB II has pop-out wings to give it a healthy standoff glide range, and a tri-mode seeker featuring semi-active laser (SAL), millimeter wave radar (MMW) and uncooled imaging infrared (IIR) guidance. The weapon incorporates a dual-band UHF/Link 16 data link and is fully network-enabled, allowing it to be handed off to other platforms in flight, and is capable of in-flight re-targeting. The radar seeker can act as an altimeter to give selectable air-burst capability, while the warhead combines the properties of a traditional blast/fragmentation warhead with a shaped charge.
Advantages of the SDB II, compared with such earlier weapons, include its ability to attack moving targets and its enhanced performance in adverse weather. The weapon can be used in three primary modes of increasing complexity. In the co-ordinate attack mode it uses GPS to guide to a point designated by latitude/longitude co-ordinates. In the laser-illuminated mode it functions as a typical laser-guided weapon, able to target points designated from a number of sources.
In the normal attack mode the weapon uses fused MMW and IIR guidance data. The weapon is given some information from the aircraft’s weapon system prior to launch, and then flies by GPS/inertial guidance to the general target area. The MMW radar is used to find target-like objects, this sensor being particularly useful in penetrating clouds and smoke. As the weapon nears the target, the IIR sensor is brought into play to further refine targeting. The missile has built-in algorithms to classify the target type, such as wheeled or tracked vehicles, and also to prioritize the target that it attacks.
SDB II entered the engineering manufacturing development phase in August 2010, and that is scheduled to continue until 2017. LRIP weapons will be fielded first on the U.S. Air Force’s Boeing F-15E Strike Eagle, which has been used for a number of tests that have verified the weapon’s capability against moving targets. The majority of EMD flight trials have already been completed, with only a few fully guided tests left to be accomplished during this month.
In addition to the F-15E, the SDB II is considered a priority for the Lockheed Martin F-35B/C for the U.S. Marine Corps and Navy, although it would also be applicable to the Air Force’s F-35A. Fit-checks were completed early last year to verify that the Joint Strike Fighter could carry four SDB IIs in each weapons bay alongside an AIM-120 AMRAAM air-to-air missile.
SDB II is planned for inclusion in the Block 4A iteration of the F-35, which is scheduled to achieve initial operating capability around 2021. Raytheon (Chalet C7-9, OE9) and the JSF team are shortly to begin pit-drop tests from the F-35’s bay before increasingly complex air-drop tests. These begin with jettison test vehicles to verify safe separation, control test vehicles with initial guidance package and finally guided test vehicles with full guidance systems and telemetry equipment. In terms of the F-35 itself, some integration is required in the operational flight program software.
Although the F-15E and F-35 are the main priorities for SDB II, the weapon is also applicable to many other U.S. tactical aircraft, including the unmanned MQ-9 Reaper. Raytheon has received approval to offer the weapon for export to certain partner nations, and it has received considerable interest. To support this campaign the SDB II has been fit-checked on the Lockheed Martin F-16 and Boeing F/A-18. o