Muting the Hype over Hypersonics: The Offense-Defense Balance in Historical Perspective

X51A Waverider hypersonic_edited

The “allure of battle,” writes Cathal Nolan, is a powerful one. The compelling idea that the first mover wins has drawn many to start wars; as such, it can be deeply destabilizing. Technological developments amplify these tendencies, especially when emerging technologies seem to favor the offense. This is the case for fear-filled discussions about hypersonic weapons, for which no defensive measures currently exist.

Currently, the United States is struggling to adjust to new technological developments as it enters an era of near-peer competition. But it is critical for U.S. policymakers to take the long view of technological change. Recalling the frequent shifts in the historical relationship between offense and defense, it becomes evident that the standard cycle of offensive and defensive weapons development will continue and that defensive solutions to the hypersonic challenge will soon be developed. When that happens, Chinese and Russian acquisition of hypersonic weapons will actually help to stabilize relations — not unlike a conventional form of mutually assured destruction. Such a development would mark a departure from a period when the United States had precision capabilities and others did not, which amplified Russian fear of the United States.

Historical perspective helps to temper the fear of destabilizing innovations in the hypersonic weapons space by U.S. rivals. During the interwar period, airpower advocates from Giulio Douhet to Billy Mitchell insisted that the bomber could not be stopped. The devastation that bombers could bring to cities would be so horrific that war simply could not last more than a few days. Airpower, they insisted, should be used as part of a “relentless” offensive. The development of radar before the outbreak of World War II, however, helped reset the balance between offense and defense.

As legendary airman Claire Chennault insisted even before radar was developed, the bomber would not be “the first exception to the ancient principle that for every weapon there is a new and effective counter weapon.” We can point to numerous other examples of this rebalancing between new offensive and defensive capabilities, such as between armor and anti-tank missiles. More recently, anxiety about the destabilizing effects of drones has receded to some extent with the development of anti-drone technology.

Today, experts worry about airpower’s limitations in light of drastic improvements in defensive capabilities, especially advanced surface-to-air missiles. Hypersonic weapons, however, offer the possibility of resetting that balance just as improvements in bombers did prior to the advent of radar. A recent War on the Rocks article described how hypersonic missiles, “which travel at speeds greater than Mach 5, shorten John Boyd’s famous observe-orient-decide-act loop, making it nearly impossible for human minds and teams to even comprehend the information, let alone defend against a short-range attack.” The article paints a compelling picture of the kind of threat the United States faces as its peer competitors diligently pursue weapons that pose a seemingly intractable problem.

Hypersonic weapons have many in the U.S. military on edge. Due to their speed, they significantly reduce reaction time, have sufficient kinetic power to cause significant destruction even without a payload, and are difficult to intercept. As a result, hypersonics can bypass a country’s defense systems and strike areas within that country with little to no resistance. The U.S. Defense Intelligence Agency told Congress in its Worldwide Threat Assessment that hypersonics will “revolutionize” warfare by enabling targets to be struck faster, harder, and from farther away. Note, however, that such characteristics are far more evolutionary in nature than revolutionary.



It is important to acknowledge the limitations of hypersonics, which do, in fact, permit the development of defensive countermeasures. While hypersonic weapons travel at an extremely fast rate of approximately 2 miles per second, the speed of the Tsirkon hypersonic cruise missile, they still pale in comparison to the speed of directed energy weapons (which travel at the speed of light, 186,282 miles per second). Directed energy weapons such as lasers and high-power microwaves are gaining traction because they address the threat of hypersonics with an unconventional approach. Throughout history, militaries have tried to defeat weapons by creating the next most advanced version of those weapons. If one country created a missile capable of traveling 10 miles, another country would create a missile capable of traveling 20. However, with directed energy weapons, the approach is to defeat the technology that makes these advanced weapons so threatening. Lasers are capable of destroying targets using a focused beam of energy, while high-power microwaves are an invisible wave of electromagnetic energy capable of frying microprocessors.

Hypersonic weapons are fast, but they are not instantaneous. Thus, when used against moving targets beyond certain distances, the weapons lose effectiveness as the target’s speed increases and its size decreases. Such limitations require most hypersonic weapons to have some form of onboard guidance, which in turn necessitates electronic circuits to do computations and make guidance adjustments. These circuits are highly susceptible to high-power microwave damage. Additionally, the beam width of high-power microwaves is significantly wider than that of a weaponized laser, which requires less time to be used for targeting. Although lasers are extremely effective, when it comes to countering hypersonic weapons, they are limited by line of sight, limited range, and power requirements. For this reason, when talking about defending against hypersonic weapons, high-power microwaves are the more logical choice.

Additionally, because hypersonic weapons are so fast, they struggle with maneuvers in the final seconds against small fast-moving targets. This is due to maneuverability limitations at high speeds. Hypersonic weapons, therefore, are most effective for large and slow-moving or stationary targets, such as an aircraft carrier. Areas outfitted with high-power microwaves could provide area denial capabilities for high-value target areas against hypersonic weapons. Using the equations provided in a University of Maryland study of high-power microwave technology, a source power of 9.5 megawatts could deliver the power density required to damage a hypersonic weapon at a target 25 miles away. This would be about 12.5 seconds prior to the missile reaching the transmission site, assuming the hypersonic weapon is traveling directly toward it. This may not seem like a long time, but the slightest change in trajectory in anything traveling at those speeds would result in a drastically different termination point. For example, an angular change of half a degree would result in a miss distance of 1,150 feet. Additionally, depending on the fusing method, high-power microwaves may also be able to prevent the weapon from fusing and, ultimately, deny detonation.

China is one of many countries attempting to develop such directed-energy technology. Richard Fisher, an expert on Chinese and Asian security at the International Assessment and Strategy Center, stated in testimony before the U.S.-China Economic and Security Review Commission:

Some Chinese military experts expect that energy weapons will become more prevalent in 10 to 20 years and will dominate the battlefield in 30 years. As such, it is imperative that the United States redouble its focus to achieve technology breakthroughs needed to realize decisive energy weapon capabilities and be ready to cooperate with critical allies to accelerate co-developments. The U.S. should also retain the flexibility to deploy energy weapons from diverse platforms, including space platforms, to meet what could be rapidly emerging new Chinese energy weapon threats.

Lockheed Martin is now also discussing integrating the technology into UAVs for the Army, but this integration is at a tactical level while high-power microwave technology has strategic uses. Although Boeing initially led the high-power microwave field in 2012 with its development of the Counter-electronics High-powered Advanced Missile Project, or CHAMP, its use and integration has been limited to the B-52. Other countries are advancing the field. China is developing high-power microwaves not only for the purpose of deployable munitions but also for area denial for high-value targets. More integration is necessary if the United States is to remain effective in an evolving battlespace.

High-power microwave technology, however, is not without its own weaknesses. Its effective range is based on the power density present at the target, a number of factors that can affect this figure, such as transmitter power, feeder loss, antenna gain, range, path loss, and the effective isotropic radiated power. These factors really boil down to two design elements: environment and range. These limitations can be used to create a versatile weapon that can defeat hypersonic weapons in most cases. As technology moves forward, someone will inevitably determine how to artificially increase the path loss to a point where the microwave drastically loses effectiveness. It is important to acknowledge each technological leap not as a permanent solution but as part of an ongoing cycle, just as has been the case for other weapons, such as the tanks discussed earlier. Many in the Army believed them to be obsolete in the 1970s until innovators stumbled upon a lightweight protective material that provided them with an important offensive advantage once again.

Whether it is hypersonic weapons or high-power microwave technology, no one method or technology can exist for long without a countermeasure. Still, hypersonics and other weapons will continue to entice nations with the promise of easy answers that can reduce the fog and friction of war. For now, U.S, policymakers should invest in directed-energy technology while bearing in mind that it is not a silver bullet.

Amid the return to great power conflict, it is understandable that the United States fears the rapidly increasing capabilities of its rising peer competitors. But it is worthwhile to consider whether the U.S. investment in hypersonics needs to be rebalanced more toward developing defensive capabilities. It is also helpful to consider those fears in historical perspective and in light of constant shifts in the technological and military balance. The United States needs offensive and defensive hypersonic capabilities for deterrence. Yet ironically, China and Russia’s acquisition of these capabilities can help to stabilize tensions because it helps them fear the United States less, and vice versa. So keep calm and innovate on.



Dr. Heather Venable is an Assistant Professor of Military and Security Studies at the Air Command and Staff College, where she teaches classes on airpower and the historical experience of combat. She has written a forthcoming book entitled How the Few Became the Proud: Crafting the Marine Corps Mystique, 1874-1918.

Clarence Abercrombie is a Captain on Active Duty in the United States Air Force. He is an F-15E Strike Eagle Weapons Systems Officer and Instructor Combat Systems Officer at NAS Pensacola. He is an advocate for HPM technology, Chairman of the National League of Female Veterans, Marketing Staff member for Legacy Flight Academy, and a 2019-2020 Regional Finalist for the White House Fellows Program.

The views in this article do not reflect any official position or opinions of the United States Air Force or the Defense Department.

Image: U.S. Air Force graphic