Breakthroughs in the precision and cooling mechanism of infrared sensors are pushing forward the country’s development of hypersonic weapons, researchers say. Warfare could be transformed by hypersonic missiles able to search for, identify and lock on to targets based on heat signature.
Chinese scientists say they have developed next-generation hypersonic weapons with technical breakthroughs in infrared homing technology – which the US military may not have until 2025.
Heat-seeking capability allows Chinese hypersonic missiles to home in on almost any target – including stealth aircraft, aircraft carriers and moving vehicles on the street – with unprecedented accuracy and speed, according to the researchers.
The first generation of hypersonic weapons were designed to penetrate missile defence systems and hit fixed targets on the ground at five times the speed of sound or faster. Although China and Russia had deployed some hypersonic missiles, a popular opinion elsewhere was that these weapons had little practical value unless a country wanted to start a nuclear war.
But conventional warfare could be transformed by a hypersonic missile being able to search for, identify and lock on to a target based on its heat signature when flying at low altitudes where the air is thicker, said the Chinese researchers, from the hypersonic infrared homing programme at the National University of Defence Technology.
According to the US Air Force, about 90 per cent of all the aircraft it has lost since the 1980s were shot down with heat-seeking missiles, and stealth fighters such as the F-22 could also be targets because their coating materials heat up easily in flight. A Chinese military researcher told an academic conference in 2020 that a ground-to-air hypersonic missile could catch up with and destroy an F-22 in a matter of seconds if it fired a missile or dropped a bomb from close range.
Heat sensing at hypersonic speed is not easy, but China has made “a series of core technology breakthroughs that were proven effective in tests”, lead scientist Professor Yi Shihe wrote in a paper published on December 15 in domestic peer-reviewed journal Air and Space Defence.
The country’s hypersonic infrared missiles had already been used in a number of test flights – work that won Yi’s team a top national award for military science and technology from the People’s Liberation Army, according to an editor’s note that introduced Yi’s work in domestic journal Modern Defence Technology last June.
“Precision guidance with infrared imaging technology is a force multiplier for hypersonic weapons,” Yi said in a paper published in the journal.
“If one party takes the lead in processing mature hypersonic weapons, this party will have the absolute advantage of asymmetric attacks.
“With effective hypersonic precision strike weapons, the critical value of ‘strategic depth’ in traditional warfare will no longer exist. All the critical political, economic and military assets of a country will be at risk.”
At high Mach numbers, the surface of a missile becomes so hot that a target’s heat signal can be overwhelmed by background noise. The infrared window would crack because no glass material could withstand the extreme heat and shock waves.
Scientists from around the world had proposed ways to lower the temperature, such as splashing liquid over the window or planting cooling tubes under the glass. Most of these ideas were ineffective or too complex, according to Yi and his colleagues.
The Chinese scientists put an air-blowing device in front of the infrared window to generate a thin membrane of cold air, reducing the heat on the glass. Some research teams in other countries had tried this approach but failed because the cooling air could trigger strong turbulence that distorted the heat signal, giving a fuzzy, flickering and less accurate location of the target.
Yi’s team solved this problem with a number of breakthroughs. They developed a compact, lightweight device that could generate an extremely cold stream of inert gas at more than three times the speed of sound to reduce signal distortion.
They managed to squeeze 40 microvortex generators into the air-cooling device to produce air flows that could break apart the turbulence. They also developed a new mathematical model that helped them to better predict and eliminate the optical distortion as missiles accelerated and homed in on targets at wide attack angles.
This progress came from a large number of experiments that they conducted in the KD-01 wind tunnel, a world-leading research facility for hypersonic infrared homing technology in Changsha.
The wind tunnel used a unique technology that allowed researchers to observe turbulence over glass with a resolution more than 120 times higher than that of facilities using American technology, according to Yi.
The United States had previously been a world leader in heat sensing, according to the Chinese scientists. In the 1980s and 90s, the US government and military invested an enormous amount of resources in the development of high-speed infrared homing technology that was used to develop missile defence systems such as the Terminal High Altitude Area Defence (THAAD) system.
However, these heat sensors worked only in thin air at high altitudes. Last February, the US Defence Advanced Research Projects Agency asked numerous defence contractors, including General Electric and Lockheed Martin, to develop infrared sensors for hypersonic missiles.
According to their contracts, the development and testing of their sensors will take at least four years.