Amid growing concerns of missile inventory size and VLS cell count, the U.S. Navy is set to test a new surface-launched missile interceptor designed to maximize capacity in their Mark 41 VLS cells. The effort comes as production of SM-6 ramps up into the late 2020s to match inventory requirements, alongside increased production of RIM-162 ESSM Block II.
The Compact Agile Interceptor aims to pack multiple small diameter missiles into one Mark 41 VLS cell while keeping high-end performance capability to intercept ‘complex raids’ of hypersonic threats. The addition of a compact interceptor would add a third missile to the U.S. Navy’s inventory capable of dealing with hypersonic threats, coming in behind the 13.5 inch (0.34 m) SM-6 Dual I/II and 21-inch (0.53 m) SM-6 Block IB.
What seemed like a contender for the CAI program was Lockheed Martin’s Patriot Advanced Capability 3 Missile Segment Enhancement (PAC-3 MSE), which was reported by InsideDefense last year. It has seen action in Ukraine against hypersonic aeroballistic missiles (the Kh-47M2 ‘Kinzhal’ or AS-24 Killjoy air-launched ballistic missile) and reportedly against hypersonic air-breathing missiles (the 3M22 ‘Zircon’ or ‘SS-N-33’ hypersonic cruise missile).
PAC-3 MSE’s diameter is roughly 11.4 inches (29 cm), a little over half the diameter of a common missile canister used in Mark 41 VLS cells. Despite the smaller diameter, Lockheed Martin told Naval News at Sea Air Space 2023 (SAS) that the intention was to leave the missile largely unchanged for integration work, ending the possibility of dual-packing missiles for the time being, thus ending the possibility of the missile being a candidate for Compact Agile Interceptor.
“I think there’s a lot of studies of what you can do. Our big thing is to keep the missile the way it is. So you have to get into things like folding things and other stuff if you wanted to try to increase the capacity within one cell. What we want to do is work and partner together. So one missile comes off the line and can go to the Army, the Navy and it’s not unique to that to that it’s just one way to go.”
Lockheed Martin at SAS 2023
PAC-3 MSE does not meet program requirements unless Lockheed Martin modifies the control surfaces to fold inside the Mark 41 VLS cell. Doing so would allow the missiles to dual-pack inside each Mark 41 VLS cell, doubling the magazine capacity. That added capacity is a critical requirement for missiles in the Compact Agile Interceptor program. With Lockheed Martin opting to maximize efficiency and commonality, for good reason, the likelihood of PAC-3 MSE being a CAI candidate is slim.
According to U.S. Navy budget documents for FY2025, the propulsion concept for the Compact Agile Interceptor has already been chosen, with plans for the “procurement of 2-3 flight test units with [the] selected propulsion concept” this year. A wide range of propulsion options are on the table, ranging from highly loaded grain propellants to solid fuel ramjets, which will likely be staged on a first-stage booster.
Details on the chosen propulsion system and competitors in the program thus far have not been made public, but flight tests are planned for FY2025 which begins in October of this year. Full All-Up Round (AUR) tests are not expected for quite some time.
