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Defense Speak Interpreted: Why Is Defense Hyper Over Hypersonics?

Perhaps you have noticed that the term “hypersonics” is now a buzz phrase in a big part of the Department of Defense research effort. What does hypersonic mean, and why is so much work needed in this weapons field?

Hypersonic is a term generally accepted for a missile traveling at least five times the speed of sound, or at least 3,836 miles per hour (speeds of Mach 5 and above). Generally accepted terms for speed of travel are given in Table 1.

Table 1: Regimes or ranges of Mach values ^[1].

In my February column, I concentrated on the traditional activities of the Missile Defense Agency and the effort to detect, intercept, and destroy intercontinental ballistic missiles that travel into space and then re-enter the atmosphere, as given above at “re-entry speeds.” Remember the characteristic of the flight body: an ablative heat shield, small or no wings, and a blunt shape.

Hypersonics are a whole new class of weapons, traveling faster than jet interceptors (Mach 5) and perhaps not going into space, or at most not nearly as high as ICBMs. Besides the previously listed properties for hypersonic and high-hypersonic flight, weapons in this group are intended to be maneuverable to avoid either detection or being intercepted. The end target for a hypersonic weapon cannot be determined from the flight trajectory.

But what makes a hypersonic different from a cruise missile? They both fly in the atmosphere and are maneuverable. Cruise missiles are subsonic but far slower than the target for hypersonics. Now, you can see the hole that Defense is facing—too fast for jet plane interceptors and able to avoid the traditional missile intercepts that MDA has perfected.

What is the overall objective of hypersonics? The concept of “prompt global strike.” Wikipedia defines this as “a United States military effort to develop a system that can deliver a precision-guided conventional weapon airstrike anywhere in the world within one hour” ^[2]. Simple math says that the weapon must be launched within 3,836 miles of any target on earth, or the weapon must operate faster than Mach 5 to reach any target. The same math says that a Mach 25 weapon would travel over 19,000 miles in an hour, so the weapon could reach any point on earth in an hour—depending on the direction of launch.

Two basic propulsion technologies enable hypersonic weapons: glide body and scramjet. The glide body concept uses much of the initial propulsion of an ICBM boost rocket (self-contained oxidizer). However, the term glide refers to the maneuverable descent phase through the atmosphere and under propulsion. The scramjet (supersonic combustion ramjet) principle uses initial rocket propulsion to reach top speed, and then the forward thrust helps compress supersonic air (ramjet) throughout the burn cycle in the engine. Remember, jet engines use compressed atmospheric air as the oxidizer and don’t have to carry weighty oxidizer—either longer distance or a bigger payload.

The Air Force weapon is the Air-launched Rapid Response Weapon (ARRW). The Navy weapon is the Conventional Prompt Strike (CPS) and is designed to be submarine-launched. The Army version is the Long Range Hypersonic Weapon (LRHW). As mentioned previously, the Common Hypersonic Glide Body (C-HGB) is the shell for both the Navy and Army weapons. Reportedly, the Navy is working on the Glide body, and the Army is working the weapons package to be delivered ^[3].

To add to the DoD concerns, Vladimir Putin of Russia has boasted that their Avangard “boost-glide” system is capable of carrying a two-megaton nuclear weapon at 27 times the speed of sound. And China successfully tested its own hypersonic missiles, dubbed the Xingkong-2—or “Starry Sky-2—and the Dong Feng 17—or DF-17—displayed at a recent military parade.

What is the challenge for electronics designers to support the hypersonic missile programs? First, there is the heat issue. The surface of the weapon approaches the temperatures of the space shuttle re-entry, with the ceramic tile surface. It is known that in 2011, DARPA's Hypersonic Technology Vehicle 2 (HTV-2) traveling at 13,000 mph, reached a skin temperature of 3,500°F. While materials of construction are closely guarded secrets for hypersonic weapons, suffice it to say that either the electronics must be designed to operate hotter than today’s circuit board maximum operating temperature (MOT) of 125°C or else the weapon must use extensive cooling of the guidance and detonation electronics.

Second, the hypersonic weapon is designed to evade conventional anti-missile systems. This means the guidance electronics must have AI to be self-piloted with sensors to avoid radar detection, anti-missile weapons, and jamming efforts by the targeted enemy.

This is summed up in the presentation at the Hypersonic Weapons Summit on April 1, 2020, by Dr. Alex Roesler, who is the deputy director for the Integrated Military Systems Center at Sandia National Laboratories. His presentation was titled “Efforts to Integrate Autonomous and AI Capabilities Into Hypersonic Systems: Developing Artificially Intelligent Aerospace Systems.”

The description of the presentation states ^[4], “The incredibly fast nature of hypersonic provide a strategic capability that could potentially alter current force structure as we know it. However, this speed comes with a price; it leaves little room for human intervention regarding changes or path correction. Our partners at Sandia are researching the application of autonomous and AI capabilities into hypersonic systems to circumvent this challenge,” including:

• “Efforts to integrate autonomous capabilities into hypersonic systems: near-term engineering challenges”
• “Addressing challenges of path planning, perception, localization, and flight control”
• “Ongoing collaborative efforts”

The current Defense budget contains a 23% increase in spending on Hypersonics ^[5]. Continue to watch the development of hypersonic weapons as a major focus of the U.S. Department of Defense.

References

1. Wikipedia, “Hypersonic Speed.”
2. Wikipedia, “Prompt Global Strike.”
3. S. LaGrone, “VIDEO: Pentagon Test Launches Prototype Hypersonic Weapon,” USNI News, March 20, 2020.
4. Institute for Defense and Government Advancement (IDGA), “Hypersonic Weapons Summit, Main Day 1,” April 1, 2020.
5. N. Strout, “New Pentagon Budget Request Invest in 4 Advanced Technologies,” DefenseNews, February 10, 2020.

Dennis Fritz was a 20-year direct employee of MacDermid Inc. and has just retired after 12 years as a senior engineer at (SAIC) supporting the Naval Surface Warfare Center in Crane, Indiana. He was elected to the IPC Hall of Fame in 2012.