Houthis claim ‘hypersonic’ missile used in Israel attack. What are hypersonic missiles? - explainer

The Iranian-backed Houthi group claimed on Sunday to have launched a hypersonic ballistic missile at Israel. While there is no evidence that the claim is accurate, it is clear the Houthis managed to reach Israel with a missile. Its flight path is not known, nor the particulars of its speed, but the Houthis claimed it flew 2,040 km. in 11.5 minutes.

The key claim of the missile being “hypersonic” is noteworthy because many countries – and now even terrorist groups – are claiming “hypersonic” capabilities.

The IDF confirmed some aspects of the Houthi claim. It said that a surface-to-surface missile was fired from Yemen toward Israeli territory, launched at 6:21 a.m. “An initial inquiry indicates the missile most likely fragmented in mid-air,” the military said. The sirens sounded in Israel at 6:32 a.m. – meaning that the flight time the Houthis claimed appears relatively accurate.

This allows for a quick calculation of the approximate speed of the missile: approximately 177 km. per minute. A hypersonic speed is defined as being above Mach 5, or more than five times the speed of sound, that is more than 102 km. per minute.

The Center for Arms Control and Non-Proliferation notes that “technically speaking, hypersonic weapons have existed since the middle of the 20th century. A hypersonic weapon is merely something that travels at Mach 5 or faster, or at least five times the speed of sound. Ballistic missiles have long possessed these speeds.”

However, merely being “hypersonic” is not actually what matters in today’s discussion of hypersonic missiles.

The Stockholm International Peace Research Institute (SIPRI) notes that “the speed of ballistic missiles (predating the current hype around hypersonic missiles by almost a century) in many cases far exceeds that of today’s ‘hypersonic missiles.’ The ancestor of ballistic missiles, Germany’s A-4 (which later became commonly known as the V-2) was first launched in the 1940s. During ascent, it could reach a speed greater than Mach 5 (although only for a brief period) and could do so again momentarily on its way back down. But, no one would claim that the V-2 was a hypersonic missile. In a similar vein, should one apply this label to modern intercontinental ballistic missiles that reach speeds beyond Mach 20 at ascent and re-entry?”

Hypersonic missiles today are those that have the ability to maneuver; they don’t merely go up and come down in a trajectory, like a ballistic missile. The weapon must be able to maneuver within the atmosphere, which usually means moving vertically or horizontally.

Which countries claim development and access to hypersonic missiles?

Last year, Iran claimed to unveil a hypersonic missile, saying that it had developed a missile that could be fired and then separate, where part of it re-enters the earth’s atmosphere. It was not clear if the Iranians had completed this missile and tested it. Nevertheless, the increasing claims of “hypersonic” capabilities by Russia, China, and other countries are raising eyebrows and leading air defenders to want to find ways to defeat these systems.

The main challenge of truly hypersonic weapons is the maneuverability at high speeds. It is already clear that cruise missiles and drones present unique challenges to air defenses. Air defenses have to do more than just intercept weapons that are based on statistical trajectory methods of fire. What that means is that it is easier to intercept an object that goes up and comes down on a known path, than an object that is moving around.

It is also difficult to detect low-flying objects that may fly through valleys the way cruise missiles may fly. It is also hard to intercept drones, not only because they maneuver but because they may fly very slowly or have a low radar cross-section.

Systems that detect threats are designed to detect and also define or classify the threat, which becomes very important in a battle space with many objects in the sky. For instance, Iranian air defense shot down a commercial jetliner in 2020 because their air defenders mistook it for a threat. In today’s world, one doesn’t want to shoot down their own planes or drones or mistake a flock of geese for a drone swarm.

Air defense systems are also expensive. For instance, the interceptors used against large ballistic missiles or long-range threats are much more expensive than Iron Dome interceptors, which are used against shorter-range threats. This means that an air defense picture is important, and not making mistakes is equally so. Israel’s enemies, such as the Houthis, Hamas, and Iran, by extension, want to develop new capabilities to try to test Israel’s defenses. This translates to attacking with drones from different directions, like the Houthi drone attack from the Mediterranean Sea in July.

A lot has been learned in the realm of the Iranian missile and drone threat. This can be seen chiefly from the massive aerial attack Iran launched toward Israel in April, which was thwarted by a combination of capabilities from Israel, the US, and the UK.

The Houthi claims about a “hypersonic” weapon are purely to spread propaganda about their accomplishments. The key question now is whether the Houthi missile – which is likely based on Iranian technology – can maneuver at high speeds within the atmosphere. Is it a type of cruise missile or a ballistic missile? These are key questions, and determinations will need to be made based on the answers.

If the Houthis have indeed developed new dangerous weapons, then it is important for the international community to sanction this group. The Houthis have already proven their danger to shipping and to the region.