United States Airforce

The United States Department of Defence has suggested it is investing in the modernisation of its missile defences, but pretty soon these could be useless.

Global powers, including the United States and Russia, have been working on the concept of hypersonic missiles for over 50 years. At the moment, only preliminary tests of the systems needed for the missiles to work have been successful. Although experts at the RAND Corporation expect these weapons will become a reality in the next decade. When they do, there could be devastating consequences.


What are hypersonic missiles?

“Hypersonic missiles combine the speed of ballistic missiles with the accuracy and manoeuvrability of cruise missiles,” says Patricia Lewis, research director of International Security at Chatham House. This means that they're not only fast (as their name implies) but nimble too.

The missiles are designed to travel at approximately 5,000 to 25,000 kilometres per hour , or one to five miles per second, a report for the RAND Corporation explains. In other words, the missiles fly more than 25-times faster than modern airplanes.

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They're made of two components: Hypersonic Glide Vehicles (HGVs) and hypersonic cruise missiles (HCMs). HGVs are unpowered vehicles that glide to their target at the top of the atmosphere, reaching between 40km to 100km in altitude.

HGVs are launched on an Inter-Continental Ballistic Missiles, or ICBM. Once released they glide along the upper edge of the atmosphere, manoeuvring toward their target, says Richard Moore, senior engineer and director of RAND’s Washington office.


It's possible to keep the target a secret until the last few seconds of their flight because of the uniquely low trajectory they take in the atmosphere. It is then that missile makes its final dive.

As they near their target, they may continue to manoeuvre to avoid defences and strike whatever target they're going after. It is expected the missiles will operate at speeds between Mach 8 and Mach 20 – or between 6,200 miles per hour and 15,300 miles per hour.

However, Hypersonic cruise missiles (HCMs), use a solid-fuelled booster to accelerate to at least Mach 4. As they approach or achieve hypersonic speeds, (Mach 5 or 3,800 miles per hour), the booster on the missile will fall away and their more fuel-efficient, supersonic combustion jet engine, named SCRAMJET, ignites.

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In the atmosphere, this completes the acceleration to a higher speed, and then provides sustained power for the cruise portion of the missile’s flight.


These HCMs fly much higher than airplanes, but lower than HGVs because they need the air to be thick enough to feed their SCRAMJET engines. Like HGVs, these missiles also manoeuvre to a height that will evade defences, and will keep their target a secret until the last few seconds of their flight. Their flight altitudes are between a few tens of kilometres and 100 kilometres.

Another unique feature of the hypersonic missiles is that they can carry either nuclear weapons or conventional warheads, making them more versatile than previous missiles.

Imagined hypersonic missile in flight RAND Corporation

What makes these different from the average ICBM?

ICBMs travel much higher than hypersonic missiles, although they travel at roughly the same speed. ICBMs have little manoeuvrability, because they travel so high, which makes them quite predictable.

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Because ICBMs travel at much higher altitudes than HGVs and HCMs, they can be detected by missile ground sensors much sooner, says Moore, and so deflected. Also, because ICBMs are rocket-fuelled, their smoke is easily detectable from ballistic missile sensors in space. For the same reason, air-fuelled HGVs and HCMs are largely undetectable.

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What could the impact of this be?

Currently, hypersonic missiles are being created by the United States, Russia and China, while Australia, France and India have all been reported to be developing the technology.

“The ability to easily circumvent enemy air defenses and deliver an accurate conventional weapon to a target anywhere on the planet within one hour would fill a big gap in current military capabilities," Bruce Blair, nuclear security expert at Princeton University says. “They will be capable of evading current missile defences and would result in hair-trigger responses” Lewis adds.

The United States especially has a variety of early warning satellites and missile defence systems which would be rendered largely useless.

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Most technologically-advanced countries capable of developing hypersonic missiles would therefore be able to challenge the major powers. This means that the distribution of these missiles could create major geopolitical instabilities.

“The spread of hypersonic missiles, unless halted through export controls or a new treaty, will mean that a wider range of small countries will be able to threaten larger military powers such as China, Russia or the US,” Lewis says.

“As a result, regional powers that are trigger-happy can generate military conflicts that threaten US friends and allies and draw in major powers,” says Richard Speier, adjunct political scientist at RAND.



Blair highlights that the capabilities of the missiles could have both a positive and a negative impact. “This weapon could be used to rapidly attack terrorist hideouts or missiles being fuelled on their launch pads or highly defended inland facilities such as anti-satellite missiles sites in China,” he says.


“Without such a tool, the United States might only have a nuclear option to deal with these threats and so hypersonic vehicles could raise the nuclear threshold during conflict,” he adds. “On the other hand it could lower the threshold for conventional conflict and make the outbreak of war more likely.”

Kingston Reif, director for disarmament and threat reduction policy at the Arms Control Association, also emphasises the ability of hypersonic missiles to confuse and accelerate military conflict. “A big concern is the launch of a conventionally-armed hypersonic missile could be confused with a nuclear armed one,” he says. “Given that hypersonic weapons are still under development, there is a critical need to develop measures to constrain the development of these weapons.”

Updated 30.10.17: A quote originally attributed to Bruce Blair was incorrectly attributed to Patricia Lewis.