Hypersonics: Making MACH 5 and beyond detectable and defendableStory
February 04, 2021
Threats facing the U.S. military are evolving fast – hypersonically fast. At speeds of MACH 5 and greater, hypersonic weapons are becoming increasingly challenging to detect, deter, and destroy. Military-technology manufacturers, however, are refusing to let these light-speed advancements become the Achilles heel for the U.S. Department of Defense (DoD). The methods through which companies in the hypersonic sector plan to ensure domestic confidence in this arena are said to be dependent on innovations like early detection, robust sensor systems, and a better understanding of what exactly makes a hypersonic weapon so lethal.
The United States isn’t reinventing the wheel with hypersonic technologies or the systems that detect them. Adversaries like North Korea, Russia, and China have had significant stake in these capabilities for just as long, motivating much of the innovations that have taken place on the homefront.
This global arms race has essentially boiled down to who can detect what, when they detect it, and for how long. The U.S. military already has the capabilities to recognize and destroy short-range ballistic missiles, but what makes a missile hypersonic is a flight speed of MACH 5 and above, equivalent to 3,836 mph. For perspective, modern-day surface-to-air guided missiles like the MIM-104 Patriot travel at about MACH 4, or 3,069 mph.
Missiles like the Patriot are also engineered to follow a predictable flight path, making them easier for radars and sensors to recognize and deter. Hypersonic weapons are designed not only with significant speed advantages, but also with high maneuverability, further complicating the operational challenges that manufacturers face when building the systems that are intended to protect from them.
But industry efforts are addressing these points through sensor fusion, high-end signal processing, RF solutions, and more. In spite of the hypersonic hype surrounding these weapons and the sensationalistic nature of a deadly munition traveling faster than the speed of sound, these missiles are neither invincible nor invisible. Companies are confident that a shift from the research and development phase of developing counterhypersonic solutions to deploying and fielding them is the necessary next step in cementing the U.S. military’s position when faced with hypersonic threats. Whether or not that position is first, second, or tied with adversaries, transformation is nonetheless underway.
Sensor fusion is critical for detection
The benefits of fusing data coming in from multiple sensors can be easily understood once the characteristics of planet Earth are taken into account. When dealing with a weapon that knows no boundaries, like a hypersonic missile, keeping defense strategies tied to their respective domains could put the U.S. at risk.
“The world is round. Christopher Columbus demonstrated that about five centuries ago. And radars and RF energy, with the exception of HF [high frequency], intrinsically operate via line of sight,” says Bill Conley, senior vice president and CTO of Mercury Systems (Andover, Massachusetts). “With that in mind, it would be possible for someone to write a requirement where some type of terrestrial-based radar would not be capable of doing the mission. At that point, you have to go to the space layer to go ahead and do something useful.”
Companies like Raytheon are doing just that: Currently in development are space-based sensors for a proposed satellite constellation to aid in tracking hypersonic missiles from outside the atmosphere. Families of sensors that span domains will become key in achieving multimission detection of hypersonic threats.
“A space layer expands the battlespace and our options to respond to future threats as technologies advance,” says Erin Kocourek, senior director, Raytheon Missiles & Defense (Tucson, Arizona) Hypersonics campaign lead. “It would augment the existing missile-defense architecture and offers persistent sensing, as opposed to ground-based sensing which is limited by the curvature of the Earth. Ground sensors are challenged to see threats coming over Earth’s horizon and space allows early warning for persistent tracking from launch to impact.”
Kocourek goes on to cite that sea- and ground-based sensors are used in Raytheon’s counterhypersonic portfolio; examples are the SPY-6 to enable distributed maritime operations and the Lower Tier Air and Missile Defense Sensor (LTAMDS) designed to supplement mobile land-based operations – both with 360-degree sensing capability. (Figure 1.)
[Figure 1 | A mock-up of the LTAMDS, a radar designed to defeat advanced and next-generation threats including hypersonic weapons.]
“Having highly accurate, long-range 360 sensing allows the warfighter to see and defend against advanced threats from all directions.” Kocourek says. “Distributed sensing and integration of systems are also being incorporated as part of an advanced networked architecture to defend against new threats and provide resiliency.”
Despite any claims made by adversaries, hypersonic weapons are not undetectable, nor are they undefeatable. The very nature of these hypersonic threats has simply begun to redefine the ways in which military technology companies are innovating these sensor systems.
“Early warning from ground and space is key – and cross-domain, campaign-level modeling and simulation is especially critical to advance our missile-defense capabilities.” Kocourek says. “Initial deployments will not meet all requirements – systems will be developed with block upgrades in mind to allow for capability improvements as technology matures. This approach puts us on a path to continue to evolve and outpace the threat.”
It is evident that immediacy is the driving force behind not only the hypersonic weapons themselves, but also behind the systems that are designed to counter them. The clock is ticking in virtually every area of hypersonic technology. This need for speed is trickling down into the development process where digitization and autonomy are boosting efficacy.
Integrating autonomy and digitization into the loop
Establishing the idea that hypersonic weapons are a cross-domain threat means that the countering systems will be required to operate in varying environments. Rather than developing radars and sensors specific to each domain, which would necessitate significant amounts of time and money that aren’t readily available, companies are looking toward integrating intelligence.
“Intelligent sensors are needed,” Kocourek says, “ones that evolve with the threat. Raytheon Technologies is creating ‘software-defined apertures,’ a new generation of sensors with improved performance that are able to understand their environments, adapt to the mission, and deploy multiple capabilities. A software-defined aperture is like a phone with a thousand apps. From scanning the skies to communicating back to base, radars responding to hypersonics must be able to do much more than just detect and track a single type of threat.”
Digitization is another approach being taken when developing counterhypersonic technologies. Companies have decided that digital design coupled with a modular and open systems approach will be a quicker and more affordable way to develop and deploy.
“We also have renewed our focus on leaping forward into the future through digital design because it’s the most critical large-scale action we can take to outpace our adversaries,” Kocourek says. “Digital design will take years off the development process, allowing us to deliver solutions that outpace threats sooner.”
Intelligent sensors are also being designed with the end user in mind, as a supplemental capability to further bolster momentum and efficiency. Essentially, hypersonic weapons are a threat so powerful and encompassing that human-machine teaming could prove to be more beneficial than ever.
“There will always be a place for the human operator, but in the world of hypersonics, where seconds mean miles, we see a near future where human operators collaborate closely with autonomous platforms on hypersonic missions.” Kocourek says.
Signal-processing requirements for hypersonic detection
It’s a fact: Humans need time to make a decision, especially a decision as critical as determining how to combat an incoming hypersonic threat. The only way to buy time when faced with a weapon traveling at speeds of MACH 5 and beyond is to ensure that the systems in place to detect such weapons can do so at a significant range. This reality requires immense processing power – so much so that traditional radars struggle to maintain such high power transmission.
“Detecting and tracking hypersonic missiles will require the integration and processing of data from multiple sensors. That will include data from multiple radar frequencies and IR [infrared] sensors,” says Ray Alderman, executive director of the VITA standards organization. “That can be done by tightly coupling high-speed D/A [digital-to-analog boards that control the frequency-hopping radar transmitters and antennas], high-speed A/D [analog-to-digital] boards that collect the radar returns and IR [infrared] radiation, and high-speed processors like GPUs [graphics-processing units] that process all that data on a high-speed VPX backplane.”
Hypersonic weapons are pushing the envelope for signal processing requirements in a multitude of areas. Added to the need for longer detection ranges that will directly result in a need for greater processing power is also the fact that the amount of data coming in will grow and make it paramount to cut down on or buy the time required to process it all and turn it into actionable intelligence.
“There are ever-evolving advancements in speed of munitions and times from launch to planned target impact,” says Rob Cox, director of hypersonic initiatives at Abaco Systems (Huntsville, Alabama). “So the capability needs of military platforms and their respective ability to conduct wide sweeps of airspace via complex sensor arrays, rapidly process that data, feed it back to a response system to assess and position the intercept point of that threat, and then facilitate the operational decision loop is greater than ever before.” (Figure 2.)
[Figure 2 | Abaco Systems photo shows the test firing of a hypersonic munition.]
Today, most radars in production are active electronically scanned arrays (AESAs). These types of radars require manufacturers to put much of the signal-processing components directly into the array face as opposed to a more controlled embedded environment, making the systems more prone to thermal and environmental challenges. Counterhypersonic systems will demand specific size, weight, and power (SWaP) features different than those used in widely used radars, but defense electronics companies remain confident in future development.
“We don’t have to make those macro-level design trades, but what we do have to worry about is, if you have an electronics module in the phased-array aperture, how do you keep that cool to keep it working?” Conley says. “While there’s the overall system-level cooling, there’s also the very specific electronics-level cooling.”
The fact that one exists to ensure the failure of the other notwithstanding, both hypersonic weapons and the systems that deter them have an underlying similarity: too much heat. When trying to design a system that requires as much power as that of a counterhypersonic radar, mitigating these thermal challenges becomes a balancing act.
Managing the heat
“We’re analyzing how hot something will get and dedicating time to thinking about how we can route that heat and get it off of the board and into a conduction or some other sort of cooling mechanism to get the heat away from where it’s being generated,” Conley says. “With that in mind, the power requirements to get in are actually becoming challenging as well to try and make sure that we can actually get the right amount of power into a system. There’s a balance of that cooling and power distribution.”
Industry officials say that it all comes down to scale: When electronics are embedded in the array face of the radar, a much larger density of heat is created. Taking this science in conjunction with the majority of military customers asking for the most cutting-edge processor available whether or not the size is germane for that array face means that things are going to heat up.
“High-performance embedded computing systems generate significant heat – the enemy of reliable performance,” Cox says. “What’s needed is a dual-pronged approach: design for minimal heat and innovative cooling architectures. Board layout is critical, as is extensive thermal modeling. The key to success is to use powerful components, especially processors, originally destined for mobile applications in which minimal heat dissipation is a prerequisite, such as laptops.”
Even though the microelectronics in these counter-hypersonic systems are being driven down into smaller packages, thermal density continues to rise alongside processing power. To combat these seemingly opposite goals, gallium nitride (GaN) has proven to be a revolutionary technology for thermal management in high-power systems.
“With GaN, you’re able to get more power,” Conley says. “GaN has a larger band gap, and with a larger band gap you can put higher voltages across it, and therefore get more power out of it compared to CMOSS. GaN is a more efficient amplification of a signal, and by being more efficient it allows you to take all of that power that you’re generating and get it out the aperture of the radar in RF [radio frequency] energy as opposed to having to just turn it into heat and then deal with it as a cooling problem.”
Innovations like the use of GaN in these radar systems are pivotal, because even as the systems are engineered with near-futuristic power, a single ground-based sensor isn’t enough to protect against hypersonic weapons. The fusion of data coming in from multiple sensors strategically placed on land, at sea, and in space is thought to be what’s needed to keep the U.S. military one step ahead of hypersonic threats.