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Iain Boyd: Hypersonic missiles pose a big challenge to defend

Russia used a hypersonic missile against a Ukrainian arms depot in the western part of the country on March 18.

The technology the Russians used is not particularly advanced. However, next-generation hypersonic missiles, now under development in Russia, China and the U.S., do pose a significant threat to national and global security.

I am an aerospace engineer who studies space and defense systems, including hypersonic systems.

These systems pose an important challenge due to their maneuverability all along their trajectory. Because their flight paths can change as they travel, hypersonic missiles must be tracked throughout their flight.

A second important challenge stems from the fact that they operate in a different part of the atmosphere from previous threats. They fly much higher than subsonic missiles, but much lower than intercontinental ballistic missiles.

The U.S. and its allies do not have good tracking coverage for this in-between region, nor does Russia or China.

Russia claims some of its hypersonic weapons are nuclear capable. This is cause for concern, whether true or not.

Should Russia deploy such a system, the target nation would have to decide the likelihood of it delivering a nuclear warhead.

In the case of the U.S., if the determination were made that the weapon was nuclear, there’s a high likelihood it would consider this a first strike attack and respond by unloading nuclear weapons in return.

The hypersonic speed of these weapons increases the precariousness of the situation, because the time for any last-minute diplomatic resolution would be severely reduced.

It is the destabilizing influence that modern hypersonic missiles represent that is perhaps the greatest risk they pose. I believe the U.S. and its allies should rapidly field their own hypersonic weapons to bring other nations, such as Russia and China, to the negotiating table to develop a diplomatic approach to their management.

What is hypersonic? Describing a vehicle as hypersonic means that it flies faster than the speed of sound, which runs 761 mph at sea level and 663 mph at 35,000 feet, where passenger jets fly.

Passenger jets travel at just under 600 mph. Hypersonic missiles travel about 3,500 mph, or about a mile a second, if not faster.

Hypersonic systems have been in use for decades. For example, when John Glenn came back to Earth in 1962 from the first crewed U.S. flight around the Earth, his capsule entered the atmosphere at hypersonic speed.

All of the intercontinental ballistic missiles in the world’s nuclear arsenals, however, are hypersonic. They travel about 15,000 mph, or about 4 miles per second, at maximum velocity.

ICBMs follow a predictable trajectory that takes them out of the atmosphere into space and then back into the atmosphere again. The new generation of hypersonic missiles fly very fast, but not as fast as ICBMs, and remain within the upper reaches of the atmosphere.

There are three different types of hypersonic missiles — aero-ballistic, glide and cruise.

An aero-ballistic missile is dropped from an airplane, accelerated to hypersonic speed by a rocket, then placed on an unpowered ballistic trajectory that it can alter on direction.

The weapon Russian forces used to attack Ukraine, the Kinzhal, is an aero-ballistic missile. It uses technology that has been around since about 1980.

Hypersonic glide vehicles are similar, but are launched by rockets instead of dropped from a plane. They include China’s Dongfeng-17, which is considered the most advanced, along with Russia’s Avangard and the U.S. Navy’s Conventional Prompt Strike.

A hypersonic cruise vehicle features an air-breathing engine called a scramjet to sustain speed. Because they ingest air into their engines, they can be launched by smaller, cheaper rockets.

Hypersonic cruise missiles are under development in both the U.S. and China. The U.S. reportedly conducted an initial test flight in 2020.

Nations are developing these weapons due to their relatively high speed, relatively low trajectory and high degree of maneuverability, which combine to make them very hard to defend.

The U.S. is starting to develop a layered approach to its defense system. It features a constellation of sensors in space and requires close cooperation from key allies.

This system is likely to prove very expensive and take many years to implement.

Hypersonic missiles with conventional, non-nuclear warheads are primarily useful against high-value targets, such as aircraft carriers. Being able to take out such a target could have a significant impact on the outcome of a conflict.

However, hypersonic missiles are expensive, thus not likely to be produced in large quantities. And as seen in the recent use by Russia, they are not necessarily the kind of a silver bullet capable of ending a conflict.

From The Conversation, an online repository of lay versions of academic research findings found at https://theconversation.com/us. Used with permission.

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