An amended Request for Information (RFI) that was updated on March 20th by the US Air Force’s Armament Directorate has revealed that the US Navy’s F-18E/F Super Hornet has become an objective aircraft for integration with Boeing’s GBU-39/B Small Diameter Bomb (SDB I). The RFI states that Armament Directorate is seeking sources that can provide “SDB I Aircraft Integration, Test, & Program Support, throughout the production and sustainment phases.” SDB I is currently integrated on F-15E, F-22A, AC-130W/J, F-16C/D Block 30/40/50, A-10 and F-35A, with the F-18E/F, MQ-9, B-1, B-2, B-21 & B-52 all on the objective list. The RFI states that integration efforts are not limited to those identified aircraft, but did not specify whether integration with the F-35B & F-35C variants, for the US Marine Corps and US Navy, respectively, would be pursued in addition to the F-18E/F. The RFI also identifies Foreign Military Sales (FMS) requirements for SDB I integration. Among these would be Bahrain, Bulgaria and Morocco, who all have active FMS cases for F-16 Block 70s and SDB I, which are not yet integrated.
SDB I has been in production for nearly 2 decades, with well over 50,000 produced, including over 38,000 for the US Air Force. Naval Air Systems Command (NAVAIR) has until now not demonstrated any interest in procuring SDB I, however the Navy is a participant in the SDB II program, now designated as GBU-53/B StormBreaker. Unlike SDB I, StormBreaker adds the ability to strike moving targets, thanks to its sophisticated tri-mode seeker. The moving target requirement was infamously removed by the Air Force during the competition to develop and produce SDB I, which allowed Boeing to beat out rival Lockheed Martin. A senior Air Force procurement official later plead guilty to charges of violating conflict of interest laws. StormBreaker, produced by Raytheon, is integrated on the F-15E, with efforts underway for F-35 and F-16. The Navy achieved Early Operational Capability for the weapon on the F-18E/F in October 2023, and anticipated reaching Initial Operational Capability (IOC) by Q3 FY2024, but as of April still had two additional operational test events left to complete. NAVAIR has not yet publicly confirmed whether IOC has been achieved.
The Navy’s new interest in SDB I may be explained by their significant ongoing role in executing airstrikes against the Islamic Revolutionary Guard Corps backed Houthis in Yemen. The BRU-61/A rack allows 4 SDB Is to be carried in the place of one 1000lb or 2000lb Mark 80 Series General Purpose Bomb, quadrupling the number of targets that can be serviced by a single aircraft sortie. The US Navy has been relying on JDAM equipped Mark 80 Series, as well as much more expensive ordnance, such as AGM-84H/K SLAM-ER (Standoff Land Attack Missile-Expanded Response), AGM-154 JSOW (Joint Standoff Weapon) and even BGM-109 Tomahawk Land Attack Missile (TLAM) to strike the Houthis. SDB I is cheap, at an average unit cost of $48,000 over the 3 most recent production lots, and Boeing is facilitized to produce up to 10,000 bombs per year. Actual production is far below that, so significant orders from the Navy would help drive unit cost down. A JDAM kit for comparison (also produced by Boeing) is just over $50,000, with the Mark 80 Series being an additional cost.
StormBreaker comes in at an even higher unit cost at approximately $220,000. StormBreaker is also still just in Low-Rate Initial Production (LRIP), with actual deliveries of around 1000 bombs per year, slightly above the minimum sustaining rate of 868 per year. The current objective for a full-rate production (FRP) decision is this month, which is three years behind schedule, due to F-35B/C software development delays. Transitioning from LRIP to FRP may provide some modest reductions in unit cost, but Raytheon is already sitting on slack production capacity that is going unused due to low order quantities. Despite a MAX production rate of 2100 per year, orders are only averaging 1100-1200 per year between the Air Force, Navy and FMS customers. Increasing order quantities will be necessary to bring costs down further.
This puts the Navy in the awkward position of not having an affordable and plentiful precision guided standoff weapon in its arsenal. JDAMs offer just 24km in range, compared to 74km for SDB I. JSOW & SLAM-ER are not actively being procured by the Navy, and are much more expensive. The significant quantity of these less suitable munitions being expended in Yemen may have caused the Navy to finally recognize the capability gap that they have been operating under due to the lack of a weapon in SDB I’s class. Whatever the reason though, SDB I will certainly be a useful tool for the Navy. The Air Force back in September 2024 awarded Boeing a $6.9 billion ceiling undefinitized contract action for SDB I production Lots 20-29, which gives them significant flexibility to increase the size of future task orders to account for Navy procurement needs.