Reaction tests SABRE precooler at Mach 5 conditions

The UK’s Reaction Engines has tested the vital precooler of its SABRE engine in airflow conditions replicating speeds of Mach 5.

During ground tests at the company’s purpose-designed facility at the Colorado Air and Space Port, the SABRE precooler successfully dealt with airflow temperatures in excess of 1,000°C in less than 1/20th of a second. In April, Reaction announced that replicated airflows of Mach 3.3 had been achieved as part of the ongoing HTX testing programme in Colorado, but that corresponded to temperatures of just 420°C.

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The latest test therefore marks a significant leap forward for the SABRE programme and Reaction’s aspirations of hypersonic flight. Mach 5 is more than 50 per cent faster than the SR-71 Blackbird – the fastest-ever jet-powered aircraft – and more than double the cruising speed of Concorde.

“This is a momentous landmark for Reaction Engines in the development of its SABRE engine, which has the potential to revolutionise both access to space and high-speed flight by powering aircraft to five times the speed of sound,” said Reaction co-founder and CTO Richard Varvill.

“The performance of our proprietary precooler technology was validated at hypersonic flight conditions and takes us closer to realising our objective of developing the first air-breathing engine capable of accelerating from zero to Mach 5.”


The pre-cooler heat exchanger consists of thousands of thin-walled tubes through which coolant is passed, giving a high surface-to-weight ratio that quenches extreme airflow temperatures in a fraction of a second. This means that SABRE’s actual jet engine element receives the cool ambient air it needs to function efficiently. As well as the obvious applications in aerospace, the patented precooler technology could also benefit a range of other sectors such as automotive, energy and industrial processing.

“This is a major moment in the development of a breakthrough aerospace technology which has seen Reaction Engines’ precooler tested at Mach 5 airflow temperature conditions, smashing through previous achievements at Mach 3.3 temperatures and paving the way for hypersonic flight,” said Reaction Engines CEO, Mark Thomas.

“In addition to its use in our SABRE class of air-breathing rocket engines, there are numerous exciting commercial applications for our precooler technology. We are seeing significant interest from a range of potential customers and technology partners.”