As we enter the 2020s, China, Russia, and the United States are spending billions to develop hypersonic weapons in a bid to outpace ever-improving missile defenses.
While strategic-range cruise or ballistic missile strikes may be detected between 15 minutes to an hour before impact, hypersonic weapons capable of exceeding five times the speed of sound threaten to decrease that margin to just a few minutes. Such a fast tempo of destruction could destabilize the current balance of power by making first strikes more effective and unpredictable.
According to South china morning post report, a scramjet engine built for China’s classified hypersonic strike weapon can run at maximum boost for at least 10 minutes, the longest in the world.
In a ground test in Beijing, Dr Fan Xuejun and colleagues from the Institute of Mechanics fed extremely fast, super-hot air into the engine and took the burn to the maximum for 600 seconds, according to an article posted on the institute’s website last month.
Since 2013, the United States Air Force X-51A Waverider has held the duration record with a 210-second burn that pushed the plane to Mach 5. In 2016, an Indian test vehicle reached Mach 6 with the engine running for just five seconds.
The Chinese breakthrough was based on the “world’s first systematic investigation into the effect of hydrocarbon fuel state change on the performance and stability of supersonic combustion”, the article said.
A scramjet is an air-breathing engine for a flight that becomes operational at Mach 5 – five times the speed of sound – or above. Traditional jet engines can melt at hypervelocity. The scramjet has no moving parts, like a turbofan, but instead uses the forward motion of a plane to compress air and mix it with high-energy fuel to generate explosive thrust.
Unlike a ramjet, the air in the scramjet moves faster than sound even after compression.
Supersonic air stream could raise the temperature of the engine to over 4,000 degrees Celsius – twice that of ordinary jet engines – and if the heat built up, the scramjet could explode.
The US Air Force Research Laboratory in Tennessee, for instance, spent nine months last year to accumulate 30 minutes of combustion time on a scramjet engine.
But whether a scramjet engine can maintain the performance at high speed flight remains a question.
Huang said that ground tests could not simulate all the elements of an actual flight at high altitude and some components that worked on the ground might become less reliable in the air.
The article did not say when the experiment was conducted or if the performance was in actual flight. But the engine had been applied in a classified hypersonic weapons program, according to the institute.
Hypersonic weapons can travel up to Mach 20, according to the US Defence Advanced Research Projects Agency.
A 10-minute scramjet boost to a weapon could give it a range of more than 4,000km (2,500 miles) at top speed. Even the most advanced missile defence system would struggle to intercept threats manoeuvring at such high speed.
The Beijing active cooling scramjet engine facility used for the test was a world leader, the institute said.
Russia deployed Avangard, a nuclear-capable hypersonic glide vehicle that was reportedly capable of reaching a top speed of Mach 27 in December last year. It was two months after China showcased its DF-17 missile, a mid-range hypersonic weapon, at the national day parade.
The United States, though an early starter, has fallen behind China and Russia in the hypersonic race, according to the Pentagon. To catch up with China and Russia, the US defence department said in March that it had tested a prototype to validate the design of a hypersonic weapon that could be available for deployment by 2023.
“Delivering hypersonic weapons is one of the department’s highest technical research and engineering priorities,” the Pentagon said at the time.
