Sabre engine: How the test will work

1. Pre-cooler
During flight air enters the pre-cooler. In 1/100th of a second a network of fine piping inside the pre-cooler drops the air's temperature by well over 100C. Very cold helium in the piping makes this possible.

2. Jet engine
Oxygen chilled in the pre-cooler by the helium is compressed and burnt with fuel to provide thrust. In the test run, a jet engine is used to draw air into the pre-cooler, so the technology can be demonstrated.

3. The silencer
The helium must be kept chilled. So, it is pumped through a nitrogen boiler. For the test, water is used to dampen the noise from the exhaust gases. Clouds of steam are produced as the water is vapourised.

Reaction Engines' breakthrough is a module containing arrays of extremely fine piping that can extract the heat and plunge the intake gases to minus 140C in just 1/100th of a second.

Ordinarily, the moisture in the air would be expected to freeze out rapidly, covering the pre-cooler's pipes in a blanket of frost and compromising their operation.

But the REL team has also devised a means to stop this happening, permitting Sabre to run in jet mode for as long as is needed before making the transition to a booster rocket.

On the test rig, a pre-cooler module of the size that would eventually go into a Sabre has been placed in front of a Viper jet engine.
The purpose of the 1960s-vintage power unit is simply to suck air through the module and demonstrate the function of the heat exchanger and its anti-frost mechanism.

Helium is pumped at high pressure through the module's nickel-alloy piping.

The helium enters the system at about minus 170C. The ambient air drawn over the pipes by the action of the jet should as a consequence dip rapidly to around minus 140C.

The next few weeks will see some intense activity in the REL control room
Sensors will determine that this is indeed the case.

The helium, which by then will have risen to about minus 15C, is pushed through a liquid nitrogen "boiler" to bring it back down to its run temperature, before looping back into the pre-cooler.

"It is important to state that the geometry of the pre-cooler is not a model. That is a piece of real Sabre engine," said Mr Bond.
"We don't have to go away and develop the real thing when we've done these tests; this is the real article."

The manufacturing process for the pre-cooler technology is already proven, but investors will be looking to see that the module has a stable operation and can meet the promised performance.

Because REL is working on a busy science park, it has to meet certain environmental standards.

This means the Viper's exhaust goes into a silencer where the noise is damped by means of water spray.

The exhaust gases are at several hundred degrees, and so the water is instantly vaporised, producing huge clouds of steam.

Anyone standing outside during a run gets very wet because the vapour rains straight back down to the ground.

Courtesy: msn.news - The Telegraph - Sarah Knapton 29.06.19

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British engineers at Reaction engines have made the “biggest breakthrough in flight technology since the invention of the jet engine.”

The new invention can cool air entering an engine, from 1,000C to -150C in a 100th of a second, without creating icy blockages, allowing the jet engine to run safely at much higher power.