Defence expert: Russia’s hypersonic missiles are primarily propaganda

Kinzhal hypersonic missiles attached to Russian MIG-31s at a military parade in Moscow in May 2018. Illustration: IKvyatkovskaya / Bigstock

Russian forces using a hypersonic missile against a weapons depot three weeks into the invasion in Ukraine attracted a lot of attention. The missile was originally designed to hit American warships and bypass NATO’s missile defence systems. In the days after the attack, military experts called it everything from a display of power to a failure of the Russian Air Force, which apparently cannot move safely in Ukrainian airspace. But everyone seems to agree on at least two things: it is a very expensive tactic, and Russia does not possess many such missiles, which bear the name Kinzhal.

According to LiveScience, Americans are also working on a hypersonic missile. But it is not something that they seem to be focusing on, says Henning Heiselberg, astrophysicist and head of the Center for Security at DTU. He has previously worked in the Research Service of the Danish Armed Forces and the Danish Ministry of Defence’s New Fighter Aircraft Program. We have sent him a number of questions about the pros and cons of hypersonic missiles.

Pure propaganda

What are the benefits of using a hypersonic missile for Russia?

“Putin is using the country’s Kinzhal hypersonic missiles as propaganda for Russia’s military superiority and technological lead. As a kind of psychological warfare. The missile is expensive and has limited operational use. It has to be lifted by a MiG or Tupolev aircraft up to high altitude and close to the speed of sound (Mach 1 or 1236 km/h) before being released. But once it’s released, the engine accelerates the missile up to hypersonic speeds between Mach 5 and 10, where it has a range of up to 2000 km, after which it glides down towards the target. Its tail fins make it manoeuvrable in the atmosphere, and its high speed makes it harder to shoot down. Kinzhal is similar to the Russian Iskander short range missile, which is also being used in Ukraine. However, it’s launched from the ground and can therefore only just reach hypersonic speeds at Mach 6, and it has a somewhat shorter range.”

What other missiles can Russia use if they are not going for expensive propaganda?

“Ordinary missiles fly at supersonic speeds between Mach 2 and 4, and they can be easily launched from the ground from batteries on vehicles or individually from the shoulder as well as from aircraft, helicopters, or drones. They have almost the same efficiency and are therefore quantitatively preferable. After all, a missile’s most important elements are an engine, fuel, explosive charge, and a seeker. The faster it flies, the less fuel efficient it is. Just like cars on the road, only far worse because a rocket’s fuel consumption grows exponentially with speed. So not much is gained from the extra speed.”

“Then there are also long-range intercontinental missiles that go into space in a ballistic trajectory at speeds up to Mach 25, like low-flying satellites. But those rockets also require large amounts of fuel and are therefore quite large and expensive. They are probably much faster than hypersonic missiles, but less manoeuvrable.”

Too expensive

Hypersonic missiles are often viewed as a part of an arms race. What do you think about that?

“Russia and China claim to be leaders in hypersonic missiles, which is a half-truth. The USA has been leading in the development of aircraft and rockets since Sputnik. They have been testing various hypersonic aircraft and rockets for decades, but have found them too difficult and expensive to develop. They require much more fuel to achieve and maintain the high speeds, and aerodynamics are hampered by shock waves and by the oxygen and nitrogen molecules in the air dissociating and ionizing. Hypersonic missiles do not measure up to ordinary short-, medium- and long-range missiles in terms of efficiency, and they have therefore been repeatedly shut down by Congress.”

But speed is still a crucial factor because it can prevent them being shot down?

“That is true. The U.S. Air Force has therefore also on several occasions tried to develop hypersonic aircraft, which have great tactical possibilities—as opposed to a disposable missile. The famous SR-71 Blackbird spy plane was developed by Lockheed in the 1960s after the U2 spy plane was shot down. Its ramjet engine could reach a top speed of Mach 3.2—almost hypersonic. In order to withstand the high temperatures generated at such high speeds, it was built of titanium. Incidentally, this metal existed only in the Soviet Union and therefore had to be purchased through European shell companies. The X-15 was also developed in the 1960s, and its rocket engine could reach Mach 6.7 almost out into spac e.”

Hypersonic flight is not simple

“But hypersonic flight is just not simple. In a regular turbojet engine, the turbine compresses the air, which mixed with fuel explodes a hot jet backwards, accelerating the aircraft. At supersonic speeds, the air is automatically compressed (“rammed”) into the engine, and another type of “ramjet” engine without a turbine is more efficient. However, the air is still slowed down to subsonic velocities in the ramjet. At even higher hypersonic speeds, the air velocity in the engine becomes supersonic, and it gets the name supersonic combustion ramjet or simply scramjet.”

“Getting them to work at different speeds is a great challenge. It’s not yet possible to make hybrid engines, so the scramjet must be lifted by an aircraft at high speed before it can start, just like the Kinzhal missile.”

So you do not see Americans turning their attention to hypersonic missiles after Russia introduced them on the battlefield?

“No. If you look at what Americans are mainly focusing on in their development, it’s cruise missiles and stealth aircraft like Lockheed’s F-35. In addition, they are focusing on further developing advanced drones that can get to anywhere on Earth within a day, controlled via satellite from Nevada. They are extremely effective for surveillance and precision bombing with smaller missiles. The Pentagon has simply carried out a cost-benefit analysis that indicates that smaller and cheaper missiles can be used against, for example, Taliban donkey caravans with opium in Afghanistan.”