Naval News received a reply via email from the U.S. Missile Defense Agency’s (MDA) Spokesperson Nancy Jones Bonbrest at the end of September 2022.
Naval News: Can the MDA please explain how confident it is in the Glide Phase Interceptor (GPI) technology as of the 2020s? Could such a GPI missile system have existed several years back in the 2010s?
MDA: “MDA hypersonic defense efforts are being driven by emerging hypersonic threats. These counter-hypersonic efforts are aligned with U.S. Warfighter needs and part of a broader U.S. Defense Department strategy to bolster regional missile defenses. Developmental efforts to counter hypersonic weapons are in their early stages. Defense against maneuvering missiles, either ballistic or hypersonic, is more difficult than defense against missiles flying a purely ballistic trajectory. MDA has conducted technology assessments and analysis studies that provide confidence in current and near-future GPI Technology.”
Naval News: Are pacing threats pushing the GPI missile technology for the U.S. Navy as a direct response against enemy glide vehicles? Would GPIs have existed if it were not for peer nations’ hypersonic missile progress, or was GPI a U.S. Navy plan all along independent of peer nations’ hypersonic threats?
MDA: “MDA hypersonic defense efforts are driven by evolving missile threats, U.S. Warfighter needs, and broader Department of Defense strategy and policy. MDA’s GPI prototype development effort is fully aligned with U.S. strategy and policy, which encourages the development of systems to counter regional hypersonic threats, including sensors for the tracking and attribution of global hypersonic threats.”
Naval News: Many critics cite that it is hitting a “hypersonic bullet with a hypersonic bullet” challenge. Would missile interception challenges be easier or harder against hypersonic missiles compared to ballistic missiles?
MDA: “Defense against maneuvering missiles, either ballistic or hypersonic, is more difficult than defense against missiles flying a purely ballistic trajectory. However, MDA analysis indicates that kinetic kill is achievable for hypersonic defense.”
Naval News: Why GPI missiles and not a resurrected 747 Airborne Laser, unmanned drones, or a ship’s High Energy Laser for hypersonic missile defense?
MDA: “MDA’s GPI prototype development effort is part of a broad Department of Defense-wide strategy to counter regional hypersonic threats. As part of this strategy, the Department is assessing the full spectrum of technology available to address the evolving missile threat, to include non-kinetic capabilities such as directed energy as part of a layered defense approach.”
Naval News: Can MDA discuss specifications of the GPI missile such as seekers, kinetic kill vehicle warhead, range, dimensions, cost, size, boosters, speed, and maneuverability?
MDA: “GPI will leverage the current and proven Missile Defense System architecture that includes Command & Control, Battle Management & Communications (C2BMC), forward-based radars, other sensors, and Aegis ships utilizing cued acquisition and launch capabilities. The additional information requested is considered proprietary at this point.”
Naval News: Is the GPI missile a “one-shot chance,” or can it circle back, pursue, and try to hit again if it misses the enemy glide vehicle?
MDA: “The more opportunities to engage and potentially neutralize hypersonic threats in-flight, the better. To that end, GPI is intended to add an additional glide-phase layer, augmenting the Sea-Based Terminal layer for U.S. regional defense against hypersonic threats as part of the Department’s overall approach to a layered defense. The GPI concept of operations and engagement strategies will mature as the prototype effort progresses.”
Naval News: Can the MDA discuss if GPI is a multinational missile project with allied nations, or a domestic “U.S.-only” missile? Is NATO also developing their own GPI missiles?
MDA: “As GPI is currently a prototype effort, it is premature to discuss any international cooperative development aspects at this time. Any questions about NATO or other national capabilities should be referred to those individual countries.”
Naval News: Is DARPA or any of the Defense and university labs involved in this GPI project with MDA, or is it mainly Raytheon and Northrup Grumman?
MDA: “Addressing hypersonic threats is a Department-wide effort and there are several Department of Defense agencies, Federally Funded Research and Development labs, University Affiliated Research Centers, and industry partners contributing to the GPI prototype.”
Naval News: Does GPI borrow any technology from existing missile systems? Is that a requirement? (NASA’s Artemis Moon rocket borrows from retired Space Shuttle technology whereas SpaceX rockets use all new technology).
MDA: “GPI will leverage the current and proven Missile Defense System architecture that includes C2BMC, forward-based radars, other sensors, and Aegis ships utilizing cued acquisition and launch capabilities. Specifics of the GPI concepts would be considered proprietary information.”
Naval News: Can the GPI missile intercept anything else besides hypersonic glide vehicles? Can it target ships, aircraft, cruise missiles, satellites, drones, or rotorcraft?
MDA: “The GPI concept is designed as a defensive system to engage regional hypersonic vehicles in the glide phase of flight.”
Naval News: Can and will GPI be included in the AEGIS Ashore MDA land-based platforms?
MDA: “GPI is still in the prototyping phase. MDA will work with the Services, the Combatant Commands and other partners within the Department to ensure the GPI meets Warfighter needs.”
Naval News: Do you have a target date for GPI missile prototypes or test firings?
MDA: “Contingent on funding and Department approvals, the tentative timeframe would be to begin demonstrating the GPI concept in the 2030s.”
Naval News: How many GPIs do MDA envision to acquire by 2030?
MDA: “GPI is still in the prototyping phase. The Department has not assessed production requirements.”
Naval News: Can and will this be used for Mark 41 VLS land-based trailers for the U.S. Marine Corps and the U.S. Army or any system that has a Mark 41 VLS?
MDA: “GPI is still in the prototyping phase. MDA is working with the Services, the Combatant Commands and other partners to ensure GPI meets Warfighter needs.”
Naval News: Will the GPI be exported, or is it a “U.S.-only non-exportable” missile?
MDA: “GPI is still in the prototyping phase. Decisions about Foreign Military Sales of any new U.S. capability have not been determined.”
Naval News: What kinds of threat hypersonic weapons will GPI defend against?
MDA: “GPI will provide reliable layered defense against regional hypersonic missile threats.”
Naval News and Author’s Comments
For speculative discussion purposes, hypersonic missiles fly at speeds of at least Mach 5, or about one mile per second, or greater. The threats that the U.S.’s Glide Phase Interceptors (GPI) may target are enemy Hypersonic Glide Bodies (HGB) such as those that tip off the Chinese DF-17 and DF-21 hypersonic ballistic missiles although it is unclear from the MDA if those hypersonic missiles are the specific targets.
The artwork of a model kit below shows the shape and design of the HGB of a Chinese DF-17 hypersonic missile in the “Glide Phase” of flight (after missile booster separation) that the GPI is designed to intercept. Notice the HGB’s flight characteristics in the box art…the HGB not following a ballistic arc trajectory, not entirely low-flying and sea-skimming, but speeding and maneuvering low and fast enough to perhaps sneak under some radar and surface-to-air missile envelopes and protective bubbles.
Hypersonic threats can also be the Chinese air or ship-launched YJ-21 anti-ship hypersonic missile, dubbed the “Carrier Killer.”
“MDA has explored a number of options for neutralizing hostile hypersonic weapons, including interceptor missiles, hypervelocity projectiles, directed energy weapons, and electronic attack systems. In January 2020, MDA issued a draft request for prototype proposals for a Hypersonic Defense Regional Glide Phase Weapons System interceptor. This program was intended to “reduce interceptor key technology and integration risks”; however, according to then-MDA director Vice Admiral Jon Hill, it would not have been ready to transition into development until sometime in the 2030s. MDA instead shifted focus to nearer-term solutions and, in April 2021, initiated the Glide Phase Interceptor (GPI), which is to be integrated with the Aegis Weapon System and notionally provide a hypersonic missile defense capability by the mid- to late 2020s. Lockheed Martin, Northrop Grumman, and Raytheon Missiles and Defense have been awarded contracts for the “accelerated concept design” phase of the GPI.”