Related Video Above: Hypersonic Weapons
The successful firing of the Hypersonic Air Breathing Weapons Concept represents what could be called a breakthrough accomplishment in the Pentagon’s massive effort to fast-track, test, prototype and ultimately deploy hypersonic weapons.
The effort has taken on urgency in recent years, as senior U.S. weapons developers have specifically said that the U.S. is behind both Russia and China in the hypersonic arms race. However, with an accelerated effort and recent progress, the gap is closing quickly.
Hypersonic Air Breathing Weapons Concept (HAWC) Scramjet Engines
The HAWC is a DARPA-Air Force weapons program, with industry support from both Raytheon and Northrop Grumman.
As cited by DARPA, Air-Breathing systems like HAWC use a scramjet engine to generate thrust -- and propel the air vehicle across long distances to a target. This is quite challenging to accomplish, because while it may be possible to quickly thrust or propel a weapon or air vehicle to hypersonic speeds, “sustaining” those speeds can be an entirely different matter.
While engineered to reach previously unattainable levels of propulsion, scramjet engine technology aligns with the technical configuration of existing high-power engine systems. This includes taking in a high-speed air flow, compressing the air and then igniting it with gas or some kind of propellant to generate thrust.
The U.S. Air Force, DARPA and multiple industry partners have been developing, testing and working on scramjet propulsion technology for many years, a challenging and at times unsuccessful process. Several years ago, the Air Force had some success with its X-51 Waverider hypersonic scramjet, an effort which undoubtedly contributed to the success of the HAWC flight.
“The achievement builds on pioneering scramjet projects, including work on the X-30 National Aero-Space Plane as well as unmanned flights of NASA’s X-43 vehicles and the U.S. Air Force’s X-51 Waverider,” a DARPA statement on the HAWC test said.
Hypersonic Air Flight Challenges
The challenges with hypersonic flight are multi-faceted, as they include:
- Missile configuration
- Heat management
- Targeting and trajectory
- Boundary layer air-flow surrounding the traveling weapon
Heat Management & Air Flow
Naturally, traveling at hypersonic speeds generates unprecedented temperatures, creating a need to engineer heat-resistant materials and creating the conditions needed to generate a smoother or “laminar” air flow less disruptive to a weapon’s flight path.
Turbulence in the air flow, Air Force hypersonics weapons developers describe, can lead molecules and other particles to shift in flight, a phenomenon which can both generate excessive, destabilizing heat and throw the missile off-course. This is why hypersonics weapons engineers take great care to engineer specially and carefully shaped hypersonic vehicles, creating configurations more conducive to generating a less disruptive air flow.
A less disruptive air flow, coupled with a smoothly-shaped horizontal exterior, might bring the added advantage of some “stealthy” properties as well. One senior Air Force scientist described the air flow challenges as “boundary layer phenomenology.”
An interesting Raytheon paper published during an earlier period in HAWCs development trajectory, cites “thermodynamics” or “heat”management as essential to creating successful and sustained hypersonic flight. The amount of heat generated by weapons traveling at hypersonic speeds can easily create flight instability or even destroy some of the materials built into the weapon itself. This is one key reason why Raytheon developers specifically developed novel weapons materials intended to withstand high temperatures.
One of the greatest challenges is what the Raytheon paper refers to as the “effects chain” -- the command and control, networking and sensor technology sufficient to achieve the requisite guidance, targeting and precision flight, as maneuvering into targets, changing course as needed and achieve precision strike capability is naturally much more challenging when being attempted at hypersonic speeds five times the speed of sound.
Pentagon's HAWC Flight
The Pentagon’s HAWC took off from an aircraft propelled by a scram jet traveling at five times the speed the sound, separating from the launch aircraft and achieving booster separation, in a recent successful test of a new generation of high-speed maneuvering attack weapons.
Hypersonics are here, according to statements from DARPA about the successful flight test of the HAWC hypersonic weapon. The missile, built by Raytheon Technologies, was released from an aircraft seconds before its Northrop Grumman scramjet (supersonic combustion ramjet) engine kicked on.
“The engine compressed incoming air mixed with its hydrocarbon fuel and began igniting that fast-moving airflow mixture, propelling the cruiser at a speed greater than Mach 5 (five times the speed of sound),” the DARPA announcement said.
The DARPA paper explained that the multi-faceted goals of the mission were met, such as successful vehicle integration and release sequences, safe separation from the launch aircraft, booster ignition and boost, booster separation and engine ignition and cruise. The HAWC’s speed and maneuverability enable it attack much more quickly than subsonic missiles and it can rely upon a massive, high-speed kinetic energy impact upon target without needing high explosives.
"The HAWC free flight test was a successful demonstration of the capabilities that will make hypersonic cruise missiles a highly effective tool for our warfighters,” said Andrew "Tippy" Knoedler, HAWC program manager in DARPA's Tactical Technology Office. "This brings us one step closer to transitioning HAWC to a program of record that offers next generation capability to the U.S military."
Hypersonic Weapons of the Future
What might be next for hypersonic weapons? How about hypersonic drones? Could be feasible in the not so distant future, depending upon continued progress. One nearer term possibility was recently described by senior Army weapons developers as growing efforts to engineer a “networked” hypersonic weapon able to maneuver and change course in flight through a data link sending updated targeting information.
“We have laid out priorities for near term tech insertion. We plan to hold multiple targets at risk through communication with the weapon in flight and hit a moving or relocated target. We will also improve the warhead,” Robert Strider, Deputy, Army Hypersonic Project Office, told an audience Aug. 11 at the Space and Missile Defense Symposium in Huntsville Ala.,
Boost "Glide Weapons"
Alongside air-breathing hypersonic weapons such as the HAWC, the Pentagon is also developing “boost glide” weapons which achieve speed and range by “skipping off the upper atmosphere.” One such weapon, the Army’s Long-Range Hypersonic Weapon is slated to emerge as operational by as soon as 2023. Multiple news reports, including one from Breaking Defense, quote Army sources explaining that the LRHW will indeed reach very significant ranges farther than 1,700 miles.
Boost Glide hypersonic weapons can be a winged glider or take on a canonical shape, making them maneuverable and high-speed with a high “lift over drag ratio,” a Raytheon hypersonic weapons expert told me. The cannonical shape also increases the smoothness of the air flow surrounding the projectile, something crucial to sustaining flight stability and maneuverability.
Boost-glide hypersonic weapons, a senior Raytheon weapons developer told me a few years ago, “propel a glide vehicle to a point in space where it has a certain altitude and a certain forward speed.” The speed of descent then propels the weapon toward its target.
Kris Osborn is the defense editor for the National Interest. Osborn previously served at the Pentagon as a Highly Qualified Expert with the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox