Aircraft

Reaction begins testing Mach 4 jet engine upgrades for US Air Force

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Reaction Engines is beginning testing of its hypersonic propulsion technology with the US DoD, hoping to demonstrate its precooler can be integrated with existing jet engines to give them Mach 4 operating capabilities
Reaction Engines
Reaction Engines is beginning testing of its hypersonic propulsion technology with the US DoD, hoping to demonstrate its precooler can be integrated with existing jet engines to give them Mach 4 operating capabilities
Reaction Engines
Reaction's extraordinary precooler has already demonstrated that it can cool a Mach 5 hypersonic air stream from 1,000 °C down to -150 °C in 1/20th of a second. The upcoming tests will triple the heat load
Reaction Engines

The UK's Reaction Engines has started a new test campaign to greatly expand the envelope on its high-mach propulsion technology, hoping to prove it can upgrade current jet engines to be capable of working from takeoff speeds up to Mach 4 and beyond.

The new tests are being done in conjunction with the US Department of Defense and Air Force Research Laboratory, as part of a Foreign Comparative Testing program that the US military uses to identify high-TRL (Technology Readiness Level) technologies that could "rapidly and economically satisfy current and emerging requirements."

The technology in question is the groundbreaking precooler that forms a key part of Reaction's vaunted SABRE, or Synergetic Air Breathing Rocket Engine. The SABRE engine, still under development, is a jet/rocket hybrid that promises to operate as a super-fast jet for hypersonic flight at speeds up to Mach 5 in the atmosphere, and then engage its rockets to accelerate up to Mach 25 "for space access."

These speeds would be completely out of the question without Reaction's extraordinary precooler, a kind of radiator-on-steroids that's charged with the task of taking a hypersonic stream of air, heated to temperatures in excess of 1,000 °C (1,832 °F) by the rude arrival of a Mach 5 aircraft, and chill it down to -150 °C (-302 °F) faster than the blink of an eye, so that it doesn't instantly melt the engine internals as it passes.

Reaction's extraordinary precooler has already demonstrated that it can cool a Mach 5 hypersonic air stream from 1,000 °C down to -150 °C in 1/20th of a second. The upcoming tests will triple the heat load
Reaction Engines

Thus, it needs bulk surface area, which it achieves using thousands upon thousands of thin-walled tubes, through which coolant is forced at high pressure, with zero leakage a critical factor. Reaction says it's figured out a way to bond all these cooling tubes to the inlet and outlet manifolds in a single operation that eliminates leaks.

The company successfully tested the precooler up to Mach 5 in ground testing back in 2019, and this new test campaign, to be undertaken in Colorado in the next few weeks, will build upon that work, pushing the air mass flow rate and other test parameters to deliver "a three-fold increase in the total energy transfer through the engine heat exchanger."

From the DoD's perspective, these tests are designed to evaluate whether the precooler could be integrated with other state-of-the-art jet engines, potentially opening up a quick path to higher speeds than they're currently able to handle. “The exciting outcome that I am looking forward to over the coming weeks is the validation that our technology could enable current jet engines to operate from takeoff up through Mach 4 and beyond," said Reaction Engineering Manager Andrew Piotti in a press release.

Source: Reaction Engines

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7 comments
David F
Reaction Engine's pre-cooler is a long-awaited revolution in aerospace propulsion.
TedTheJackal
That much hardware to stretch out staging a Mach number or two seems like diminishing returns but maybe it will work out. Maybe a precooled scramjet/rocket hybrid can achieve SSTO.
Jim B
Mach 5 flights from Europe to Australasia cannot come soon enough. But I wonder if the cost can ever get low enough to compete with regular turbofan jet plane flights to these destinations?
Slowburn Fan
That temperature swing is unimaginable
Rocky Stefano
Are the current jetfighter airframes engineered to withstand Mach 4-5 speeds?
Trylon
The legendary SR-71 needed all sorts of interesting design quirks in order to handle Mach 3 speeds, everything from corrugated titanium skin to oval fastener holes to allow expansion. This obviously isn't intended for run-of-the-mill USAF aircraft, especially stealth aircraft with their composite skin.
Treon Verdery
Laser peening is a published metal strengthening technology, perhaps that could make it better.

Visualize a refrigerator with piezoelectric elements on the fins, raising airflow from microvibrations