Knoedler:<\/strong>\u00a0Our adversaries are advancing their capabilities in terms of being able to keep us away from their critical military assets. [At the same time], we are always on a continuing path to build weapons that are going to take advantage of what we think are some of their vulnerabilities.<\/p>\n Hypersonics add speed and higher altitudes than our current cruise missiles. We need to make sure that we have the right mix of weapons systems to keep our adversaries always guessing about what\u2019s coming at them, and we need to counter the systems that they have to achieve our objectives.<\/p>\n Breaking Defense: What is it about air-breathing hypersonics that can take advantage of vulnerabilities that we\u2019re seeing in our near-peer adversaries?<\/strong><\/p>\n Knoedler:<\/strong>\u00a0We don\u2019t have weapons that are flying greater than Mach 5 right now, so that changes how they would have to operate their air defense systems. If they\u2019re looking for [missiles] that are going lower and slower, it\u2019s not so easy for them to change and start looking for things higher and faster. [That means] they\u2019ve got to be very deliberate about how they\u2019re going to set up their defense.<\/p>\n Breaking Defense: What have you learned from the three HAWC flight tests [two with Raytheon\/Northrop Grumman, one with Lockheed Martin]? Were these flight tests designed to test different types of technologies? Is HAWC a competition leading to a downselect and an Air Force production contract in the future?<\/strong><\/p>\n Knoedler:<\/strong>\u00a0When the Air Force Research Lab and DARPA set up this program, we were looking to the primes to provide a diversity in designs to go after our major objectives, which were flying faster than Mach 5, higher than 60,000 feet, and range greater than 300 nautical miles.<\/p>\n What we learned on the flight tests by Lockheed Martin, who was teamed with Aerojet, and Raytheon, who was teamed with Northrop Grumman, is that we did achieve those primary objectives.<\/p>\n I wouldn\u2019t call it a competition, per se, although it looks like that to the general observer. We, DARPA, always try to exercise, test, and demonstrate anything that we think is going to give the services a choice later on as they try to transition DARPA technologies to the warfighters.<\/p>\n One of our key technical pillars [with HAWC] was attention to affordability in the design. We asked our primes to look at affordability at the start and not to gold plate it such that we can\u2019t make thousands of these in the future if they get transitioned. They made choices based upon that goal so that they weren\u2019t choosing exotic materials and weren\u2019t doing contortions within the manufacturability. In other words, we can do it with a standard process so that subcontractors and lower-tier vendors could manufacture these given a drawing.<\/p>\n Our biggest lesson learned [from the test flights] is that we did verify the feasibility of an air-breathing weapon concept. If you go back in time and look at the other X-vehicles that were flown, the X-43 and X-51, we just took it to the next step. I wouldn\u2019t say that it was to a full weapon prototype, but it certainly matured the technology that those X-vehicles had. We went a little bit higher, a little bit faster, and a little bit longer than those guys did.<\/p>\n I talked about the big objectives: speed, range and altitude. We also managed to show that we could safely separate from our launch aircraft. We were able to stage it and light the scramjet engine, which was always a challenge from previous efforts. We were able to accelerate and get this on the cruise point that we were aiming for. Knoedler:<\/strong>\u00a0We had a certain number of vehicles that we asked each performer to build, and at this point we are doing the final assembly for each performer. Then we will see whether those are healthy enough to fly over the next few months.<\/p>\n Regarding HACM, we have been working closely with the Air Force Life Cycle Management Center at Eglin and their Hypersonic Attack Cruise Missile. Certainly we\u2019ll be involved in offering our advice and our lessons learned. The intent was to leverage the work that DARPA and AFRL did for the HAWC program so that they could then go off and build something that the Air Force would like to operate.<\/p>\n Breaking Defense: It\u2019s said that air-breathers will be less costly and easier to manufacture in quantity because they don\u2019t need the super advanced materials that a boost-glide hypersonic weapon would require. What are the technological manufacturing challenges that you addressed for HAWC?<\/strong><\/p>\n Knoedler:<\/strong>\u00a0Forgive me for a bit of alliteration, but I like to describe hypersonics as technology that\u2019s hot, it goes into the high-altitude regime, it\u2019s high speed, it\u2019s hard, and there\u2019s always a bit of hype associated with all hypersonic programs.<\/p>\n For us, hot is important. We\u2019re careful about the materials we use and I\u2019m not going to specify them, but let\u2019s just say I\u2019m not picking the exotic [materials], thermal barrier coatings, and complicated manufacturing processes that you might see on a space shuttle because I\u2019m not going Mach 25 re-entering the atmosphere.<\/p>\n I\u2019m making sure I\u2019m hypersonic, but I\u2019m going to choose materials that are generally available in aerospace. We\u2019re going to use some strong alloys, and we\u2019re choosing our trajectories and profiles so that we know those materials are going to survive for the length of time that we\u2019re going to fly. We\u2019re certainly going to challenge those alloys, but we\u2019re not going to make it so gold-plated that we can\u2019t afford these things or use the industrial base as it exists right now to make them at rate.<\/p>\n Glide Breaker is about hypersonic maneuverability<\/strong><\/p>\n Breaking Defense: What is the threat scenario today as it relates to defensive hypersonics?<\/strong><\/p>\n Greiner:<\/strong>\u00a0In the defensive world, we like to break things up between strategic defense and regional defense. Strategic defense is defense of the homeland, and regional defense tends to be defense of forward-deployed assets and bases. When we talk about strategic defense from a policy standpoint, our biggest deterrent is the policy of mutually assured destruction. That\u2019s not something that\u2019s fundamentally changed by hypersonics.<\/p>\n The challenge is with regional defense, when we have forward deployed assets and bases where mutually assured destruction does not apply. Hypersonics as an offensive capability from [our] adversaries tends to stress those forward deployed defenses. Realistically, hypersonic defense is quite pivotally important for being able to ensure the robustness of those forward deployed regional assets.<\/p>\n Breaking Defense: DARPA has released an artist\u2019s conception of Glide Breaker, and its hit-to-kill against highly maneuverable hypersonic threats, which we\u2019ll publish with this Q&A. Please explain what we\u2019re looking at in the graphic.<\/strong><\/p>\n Greiner:<\/strong>\u00a0That image depicts two hypersonic threats, doesn\u2019t matter what they are, coming from the right to left. Then coming from the left is our artist rendition of the kill vehicle that we are notionally targeting for this defensive mission.<\/p>\n The way that we\u2019re viewing this system is very similar to the SM-3, which is a multi-stage system that also dispenses a kill vehicle, which then does the final course corrections in order to achieve and consummate the hit-to-kill engagement. That is what we are trying to achieve in the exoatmospheric regime against a hypersonic vehicle.<\/p>\n [In the graphic], you see an image of this vehicle positioning itself in front of that hypersonic glide vehicle to achieve the hit-to-kill. You\u2019ve heard this before but it\u2019s essentially a bullet hitting a bullet.<\/p>\n Breaking Defense: Phase 1 of Glide Breaker focused on developing and demonstrating a divert and attitude control system (DACS) that enables a kill vehicle to maneuver and intercept hypersonic weapon threats during their glide phase. Please explain and describe what you\u2019ve found at the conclusion of Phase 1.<\/strong><\/p>\n Greiner:<\/strong>\u00a0When we talk about defense and intercepts, when you\u2019re trying to intercept something [with] a head-on-head collision, just like what\u2019s in the image, there\u2019s necessity to overmatch the threat. If a threat can pull X G\u2019s, you need to be able to pull more G\u2019s than that because as soon as it makes a move you\u2019re now having to catch up. You always have to have overmatch.<\/p>\n When you actually are engaging, you by definition are at the same altitude as the threat. [That means] your maneuverability is essentially the same or on parity as theirs if you\u2019re going the same velocity.<\/p>\n That makes pulling an angle of attack [maneuver] to complete a hit-to-kill engagement very difficult if not impossible for a maneuverable threat. Therefore, we have to go to a propulsive solution to get a propulsive overmatch of this threat. That is what drove us down the direction of utilizing a divert and attitude control system.<\/p>\n We have two performers, AerojetRocketdyne and Northrop Grumman. Both are complete with their design phases and are going into testing phases now. So nothing I can share about that other than saying that there\u2019s going to be more coming forward as we progress through our test activities with them.<\/p>\n Breaking Defense: And now Phase 2, which will focus on wind tunnel and flight testing to quantify aerodynamic jet interaction effects that result from DACS plumes and hypersonic air flows around an interceptor kill vehicle. Please explain.<\/strong><\/p>\n Grenier:<\/strong>\u00a0Phase 1 was looking at the internals, Phase 2 is looking at the externals. Once the DACS, in all its glory, is producing a big, hot plume of gas, it exits a nozzle that is essentially perpendicular to the direction of travel.<\/p>\n Imagine this kill vehicle traveling at hypersonic speeds through the atmosphere and introducing this high momentum jet of gas into a hypersonic cross flow. That\u2019s unlike the ballistic missile defense world where we do this intercept exo atmospherically without cross flow because there\u2019s no flow around the body.<\/p>\n In this case we have quite a high momentum flux going across the body so when I introduce that jet there\u2019s going to be an interaction between it and the hypersonic cross flow.<\/p>\n The problem is that we have very little data to go on to help us understand that effect because it\u2019s not something that we\u2019ve had applications before that required us to look at this.<\/p>\n The purpose of Phase 2 is to collect the data that we need in wind-tunnel testing to help us inform future kill vehicle designs from both control and design standpoints, as well as actually doing a flight test of a system where we actually put it onto a rocket to gather data.<\/p>\n![\"\"](\"https:\/\/www.fie.undef.edu.ar\/ceptm\/wp-content\/uploads\/2022\/11\/DARPAs-Hypersonic-Air-breathing-Weapon-Concept.webp\")
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\nBreaking Defense: What\u2019s next for HAWC? Is there a connection between this program and the Air Force\u2019s Hypersonic Attack Cruise Missile (HACM), an air-launched, scramjet-powered hypersonic weapon designed for high-value targets in contested environments from standoff distances.<\/strong><\/p>\n