Reaction Engines precooler heat exchanger successfully achieved all test objectives in the first phase of high-temperature testing designed to directly replicate supersonic flight conditions and future tests are planned at even higher temperatures.  

The company say that the precooler is a key element of Reaction Engines revolutionary SABRE engine and is a potential enabling technology for advanced propulsion systems and other commercial applications.

HTX Test Article - Open.jpg

The ground-based tests saw Reaction Engines precooler successfully quench the 420°C (~788°F) intake airflow in less than 1/20th of a second. The intake temperature replicates thermal conditions corresponding to Mach 3.3 flight, or over three times the speed of sound.

Mach 3.3 matches the speed record of the SR-71 Blackbird aircraft, the world’s fastest jet-engine powered aircraft produced to date and is over 50% faster than the cruising speed of Concorde.

In the recent tests, the compact precooler achieved all test objectives and achieved 1.5 MW of heat transfer, the equivalent to the energy demand of 1,000 homes; successfully cooling incoming air from a temperature at which hot steel starts to glow.

The tests are the first phase in an extensive test programme which will see the precooler test article (HTX) exposed to high-temperature airflow conditions in excess of the 1,000°C (~1800°F) expected during Mach 5 hypersonic flight.


The significant testing milestone occurred at Reaction Engines’ recently commissioned TF2 test facility located at the Colorado Air and Space Port, US. The TF2 test facility has been constructed by Reaction Engines to undertake ground based ‘hot’ testing of its precooler technology. The technology has already passed an extensive range of tests in the UK where its performance was fully validated at ambient air temperatures.

Commenting, Mark Thomas, Chief Executive, Reaction Engines, said:

“This is a hugely significant milestone which has seen Reaction Engines’ proprietary precooler technology achieve unparalleled heat transfer performance. The HTX test article met all test objectives and the successful initial tests highlight how our precooler delivers world-leading heat transfer capabilities at low weight and compact size.

This provides an important validation of our heat exchanger and thermal management technology portfolio which has application across emerging areas such as very high-speed flight, hybrid electric aviation and integrated vehicle thermal management.”

To replicate the conditions the precooler will experience at hypersonic speeds, the TF2 test facility uses a General Electric J79 turbojet engine formerly used in a McDonnell Douglas F-4 Phantom aircraft to provide high-temperature airflow.

Engineers at Reaction Engines’ Culham headquarters constructed the HTX precooler test article and after initial testing it was shipped to Colorado at the end of 2018, and ‘hot’ tests commenced in early March 2019.

TF2 site .jpg

In addition to the hot precooler tests being conducted in the US, Reaction Engines is in the final stage of constructing its TF1 test facility at Westcott, Buckinghamshire, UK, where it will undertake ground-based testing of a SABRE engine core.

Over the last four years Reaction Engines say it has raised over £100m from public and private sources and has secured investment from BAE Systems, Rolls-Royce and Boeing HorizonX.

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A truly astonishing piece of technology!


Brilliant news, especially as this is the latest iteration of pre-cooler. About five years ago they used a prototype pre-cooler to feed a Rolls Royce Avon and it raised its thrust by a minimum of 50%. Come on Rolls Royce lets see what it could do to a EJ200.


Great news.
A great piece of British technology.

John Pattullo

which looks set to join the list of other british technologies that we are going to hand to the americans


That being said, because this is so common, I believe it will be guarded against considerably.

James Harrington

I do hope so Frank, but the trend says otherwise.

James Harrington

It will join ARM, GKN, just the two latest UK technology companies sold unless we protect our strategic / national technology interests. .Depressingly common and long term trend, ARM is now in the hands of the Chinese when the UK government should have know such a move was planned at the time Softbank took it for a steal. Softbank is very close to PRC in many business acquisitions. GKN facilities now being closed and tecknology transferred to the USA.

Described as an amazing bit of advanced kit. Sounds fantastic. Great work lads.

Steve Taylor

The French and Germans wouldn’t have let an ‘ARM’ slip out of ‘national control’.

For a nation of xenophobic isolationists we do well selling off everything we have to all and sundry.


Softbank is Japanese and Melrose (which acquired GKN), while an asset stripper, is a British company.

James Harrington

And Softbank then turned all the cell phone chip patents for chips used in China over to….. China, while Melrose is closing the aircraft canopy manufacturing facility in the UK and selling to who…..

Steve Taylor

Or the French……..

What I would love to know is, what is the potential market for this inter cooler and/or engine likely to be worth in the future? Will the technology be protected so Reaction gets 100% market share, or will others likely be able to copy it? The cynical part of me is just waiting to be told ‘reaction sold to Boeing’ or similar and see all the potential financial and economic benefits go to another country, or for the Chinese to steal it!
But great news and well done to all involved,a really exciting developement and one I’m following closely.


Boeing already have a share in the project… However we really need to thank ESA for them getting this far as they were funding it initially… British investors are too risk averse to put money into something that has not been fully proven which is why we lose so much tech to foreign investors.

Tim UK

Exactly right. It’s nothing to do with selling of our ideas, it’s just a fact that UK investors / VC’s are very risk averse.


Unfortunately, we all know the answer to THAT…


No, article states it uses a separate rocket booster, not combined like the reaction engine

chaz baz

Will this, if a success stay a british advantage for our companies and nation in gen, or will it go abroad and gain scant benefit to us as usual. Yeah i admit i am a bit of a sceptic nowadays. Still this looks blinking amazing in it potential.

I share your scepticism. Our amazing technical genius has been frittered away since ww2 (actually since 1890) because of lack of investment from British investors! Ask Rees-Smogg (the ultimate patriot) where he advises his clients to invest their money….

Chris H

Herodotus – I think you should either repeat what you believe that ‘advice’ to be, prove it was JRM that gave that advice or withdraw. Innuendo is not an attractive trait. JRM owns some 15% of SCM, he is not employed by them and does not advise clients as he is not covered by SCM’s licence to give financial advice issued by the FCA and cannot in any case by reason of being an MP and the obvious conflict of interest as he could be party to lawmaking affecting outside interests. Its like me owning 15% of Tesco and you… Read more »

An interesting response! I have no proof of anything of the sort…I merely suggested that those that claim to be patriots find that their business interests might be in conflict with the development of British industry. As for the content of your (attempted bullying) communication ….I really had no idea…perhaps you could enlighten us?

Not a good forum….really weak and unprincipled. Come back CPW…at least you had some spunk!

Chris H

‘Attempted bullying’?
I challenged your innuendo and gave some facts as to why I challenged it. Note I challenged the innuendo not YOU personally. There is a difference but if you can’t see it I can’t explain it.
Not sure how I can bully an innuendo … but at least you admit it is without proof.


Good to have you back Chris, you have been missed on here, hope you’re well.

Chris H

@SoleSurvivor – Thank you and yes I am still vertical and OK thanks! Likewise yourself I hope.

Daniele Mandelli

I second that. Chris H, pleased to see you comment. And also pleased you still “lurk” and keep up with things here.

Chris H

@ Daniele – Hah yes the writing stopped but the reading never did. As I said elsewhere UKDJ is required reading before other deeper sources like Janes or whatever.

Daniele Mandelli

There have been some almighty clashes here concerning Brexit. You’re expertise and ability to debunk the debunkers was sorely missed! We did try to hold the fort!

Steve Martin



Amazing isn’t it the City of London one of the two major World investment centres yet as usual high tech or anything innovative never seems to get the investment if needs from it unlike all those years when Britain was growing on its innovation. I guess investment in property to sell to rich foreigners increasing costs for the rest of us is far safer with greater rewards. OF course it will all run out in the end and we have little to fall back on. Even Sir Herman Hauser lambasted the sale of Arm abroad over British investment in it… Read more »


That is how UK business operates in general. Poor management and poor forward thinking has left many of our companies in a bad state. People like to blame the EU for many of our issues but most of them are 100% home made…


Ultimately that is how the economy is run – it’s not about building large firms but about growing profit in the City of London. Banks, VCs, pension funds etc invest in small companies, watch them grow, and when they reach a certain size, sell off their shares and collect the profit and reinvest in the next big thing. Of course, the buyer will be a foreign firm and the small British startup will become a wholly owned subsidiary. It’s ability to grow and innovate will be curtailed, it will follow the corporate practices and direction of the umbrella firm, it… Read more »


Are you aware of how many foreign acquisitions British companies make each year?


The UK accounted for £91.4bn in outward foreign direct investment in 2017, just under the £92.4bn of inward FDI for the same period. This follows three years of UK outward disinvestment that plummeted to -£100bn in 2014. We are now 5th behind the USA, Hong Kong, Germany and the Netherlands in terms of share of world outward FDI (after occupying the #2 spot between 2000 and 2015 – a period when the City of London was at its peak). But while UK companies do invest heavily overseas as the above figures show, this is driven by the City of London… Read more »

Chris H

@spyinthesky – I am not sure that is 100% accurate but I fully understand, and even agree with, your general point about how our financial system works. But some context is needed. Banks are constrained by regulations to ensure unnecessary risk is not passed on to taxpayers a la 2008. They require supporting securities and assets before lending. Other financing institutions have both security and fiduciary constraints and again cannot just be reckless investors much as they want to be. Other countries have different views and Governments will support private investment acting as guarantors. EU rules forbid this as it… Read more »


It was John Redwood who told investors to get out of the Uk.

Rees-Mogg merely has shares in a firm that has opened an Irish office and why not, lots of money is being moved to Dublin in the wake of the 2016 vote.

The main problem for British tech has been a lack of government investment as quite often we like to leave things to the market. Thankfully, for once, has seen some sense and backed this one.


Ironically most go to the US which and have private investors so perhaps its more to do with the way we penalise or even demonise investors.

Chris H

@ Blackivar Well you have (as many do) misquoted what Redwood was arguing against as was briefly referred to at the end of the article you quote. And in context the UK edition of ‘Business Insider’ (like the CBI and other large business conglomerates) is a virulent anti Brexit organisation as it and its friends like the EU so anything any Brexiteer says is dissected to the last detail to find a way to misrepresent it. Redwood was in a very long and deep debate about how the Bank of England has mishandled its side of the fiscal and economic… Read more »

Steve Taylor

I am very excited about this and have been since I first heard about the project (before REL was an entity).

Let’s hope this time the UK keeps the technology and it isn’t handed over easily as has happened far, far too often in the past.

David A-H

This technology must remain British – we are sick to death of grubby politicians and their “investment” mates selling British innovation and technology to foreign competitors.


It is nothing to do with grubby politicians. It is entirely to do with the British attitude to risk. In the US investors are willing to take risks on things like Space X etc but in Britain they crawl away until they think it is a perfectly safe investment. For instance the shoes and trainers you see that light up as you walk were a British invention, the inventors went to every British shoe company to sell them the idea but there were no takers. So they went to America and sold it to a US company and now all… Read more »

David A-H

Noted Lee – but I still wonder why the Government allows “jewels in the crown” to be taken over by foreign companies? I really can’t see the Germans or French allowing it?


I agree with you. However as UK investors are risk averse who would invest in our companies if foreign investment was curtailed?

Steve Taylor

That is why one said UK and not the ‘government’.


I was replying to David A-H…


Yes, the British attitude to risk, risk sharing and short versus long term thinking is the significant difference I think. Ultimately it is a political and social choice. For example, by virtue of thinking long term and being prepared to underwrite significant investments at government or state level France built Rafale and got it to market earlier than Typhoon. It virtually created Airbus as a European competitor to Boeing. It also managed to protect its sovereign auto and steel industries for a long time. But now their model is struggling. Patriotism and sovereignty or capitalism? Where is the best deal… Read more »

Robert Blay

Reading the comments below, maybe it’s the British natural negative attitude towards anything positive and wonderful that is the problem, a good news article, and most of the comments are nothing but moaning. Get a grip. We talk ourselves out of anything positive. Any recent article about the new carriers or F35 for example comes with a string of negative comments, we have waited decades to have this level of equipment, 2 of the most advanced carriers in the world, and a fleet of world beating 5th gen aircraft to fly off them, and what do most do? Moan about… Read more »


Save the Royal Navy thinks the carriers should have point defence missiles, think they said the decision to not have missiles was taken when we were meant to be having 12 type 45’s, they go on and question if a type 45 could defend the carrier against a saturation missile attack. Nobody moaned about the F-35B, they said specifically they can’t think of a better aircraft for the carriers, what they did do was suggest a split buy and purchase the F-35A for the RAF, pointing out the specifications which the A is better than the B and seen as… Read more »

Robert Blay

If all your escorts have been blown out of the water, a handful of SAMs on the carrier are not going to save you.


“If all your escorts have been blown out of the water, a handful of SAMs on the carrier are not going to save you.”

That’s terrible logic, why don’t you suggest that to the Navy to include in their training..

“Right boys and girls if our escorts are disabled, sunk, or there was a mechanical or human error and we have missiles incoming, don’t use the Phalanx, don’t bother firing a missile, don’t try save the ship, don’t even bother abandoning ship because you will be dead, nothings going to save you.


Robert Blay

I served in the RN for 14 years, have you? I served on Invincible class carriers for all of that 14 years, so I guess I have a pretty good idea of Navy training and doctrine, the RN is very good at fleet defence, we went 20 years on the Invincibles without the sea dart system, because it was deemed better to extend the flight deck to carry more aircraft, and trust the escorts to do there job, we have made a huge investment in Aster/Sampson radar, that’s what it’s job is for. And if there ever was a serious… Read more »


No I have not, but plenty of people who did thinks we should of had a PDMS on the QEC. Let’s not forget the only reason we don’t is because of costcutting, first in 2002 they scrapped the PDMS then in 2003 they scrapped phalanx which was later reversed. The Invincibles were built to possibly expect Soviet missiles attacking it. By the time of the mid 90’s that threat was all but gone and it was beneficial to add more space for aircraft to an already small carrier. Now we have more chance of peer or near peer threats, more… Read more »

Robert Blay

The men and women are safe when the fleet defence works, the carrier has phalanx, chaff/flares and a whole host of electronic warfare equipment. Seriously, if the shit has hit the fan that bad that every single escort, RN or coalition has been sunk, every single Aster missile/sea captor/ phalanx and whatever the American destroyers carry has been spent, a handful of missiles are not going to save the day. I mean, let’s be honest, this is 3rd world war stuff, massive scale conflict, and In times of real conflict, all sorts of toys come out of the locker that… Read more »


The French carrier keeps breaking down. Its planes are old fashioned. Russian carrier is a load of junk. The Chinese are just being poor copies of everything and half of it is propaganda. We are doing pretty well and even if we should do better it’s still better than most. Too many on here are a bunch of know all’s moaning at a load of regulation puff pieces produced by various industry PR info sheets. Our armed forces are easily up to everyone else’s except America’s. And grow up you people… we are a tiny island, not the billion plus… Read more »


Tiny island? We are the 9th largest out of over 300, the Canaries are tiny islands, Mauritius is a tiny island.

The Rafale M and E2-C Hawkeye are old fashioned? 😂 the Rafale is a very capable fighter not a million miles away from typhoon and the Hawkeye is what the yanks use.

Chris H

@SoleSurvivor – While I in no way decry the Rafale (well OK just a bit) I have to point out the Rafale M is like a Tranche 1 Typhoon which is a very different aircraft to later Tranche builds. Its why T1 builds cannot be upgraded in Project Centurion like T2 and T3 will be and 24 of the original 51 T1s are being activated from store just for QRA and other fighter roles. Rafale M aircraft are now nearly 20 years old and although they have had little use compared to all Typhoons they will be up for replacement… Read more »


Mate, you’re missing the point. The Sabre engine concept is a game changer for the aerospace industry as its seamlessly combines a gas turbine, ramjet and rocket engine in one. Therefore, it can be used to propel an aircraft from ground level to space. However, to make it work it requires the pre-cooler. To significantly reduce the air temperature before it enters the engine. This is because due to friction and the process of slowing the air down for the engine as the aircraft goes faster, the air temperature ramps up and at Mach 5 the air temperature is near… Read more »

Robert Blay

Thanks for that very informative reply. Thanks Daveyb


Anyone interested in the history of this should check out the Three Rocketeers documentary that was run in 2012 by the BBC I believe.


I am a bit confused so I hope that someone could help me out. This engine and pre-cooler is an interesting break through and hopefully stays within the UK, I can only say well done to the team. It also appears to be a requirement for Mach 5+ flight, hyper-sonic flight. At a 1,000C it will not take long before metal and electronics will fry and or warp. This I understand. This is the bit that I am confused with, the Russians and Chinese boast about their hyper-sonic missiles etc. Yet if I understand correctly this pre-cooler is designed so… Read more »

Robert Blay

Hi Ron, I can’t give you a educated reply unfortunately on this matter, but I think the story’s around the Russian and Chinese hypersonic missiles are alot of bull, and many years away from being credible weapon systems.

Remember Ron, the Sabre engine is not a standard jet engine, it is a Synergetic air breathing rocket engine. This works as a jet engine up to Mach 5 in the earths atmosphere, but can transition to rocket mode as it enters space and power up to Mach 20plus. No one else has been able to combine these two separate elements and the intercooler has always been the stumbling block. British engineers have solved the issue and means space craft will not need separate rocket boosters to get out of the earths atmosphere. The intercooler itself can also be meshed… Read more »


The ramjet engine that is used in Brahmos is basically a straight pipe, with a convergent zone that is used to compress the air so that fuel can be added to it (no moving parts). The ramjet will not work unless it is already travelling through the air at over Mach 1. Therefore, it uses a rocket engine booster to get it to this speed, which then drops off when its fuel is used up. The engine can be made of much simpler materials, with the heat resistant material start from the convergent zone to the exhaust. The missile’s avionics,… Read more »

Mr Bell

The UK needs to keep this amazing technology within the UK. Patent and copyright law the technology and concept so only this company can sell it. Then happily sell these engines to the world whilst retain sole manufacturing in the UK.
Chances of us doing that with HMGs support? Absolutely zero. We will sell it off cheap and get nothing back for yet another British innovation.


“Tests were carried out at a facility at the Colorado Air and Space Port in the US.” So the Yanks have already stolen our invention? First the M52, The Atomic Bomb, the World Wide Web, the first smartphone and countless more. When will we ever learn to stop being a country of sell-outs? You don’t see the Germans or French do this, we just willingly give everything to the Yanks and they just cut us out after.

Chris H

@AgentB I would maybe read the article again and better yet read up about the project and the company. The Colorado site is only a test facility and that is all. The company is based at Culham and is building a new test facility at Westcott in Bucks. Two of its industry partners are British based. However I do have concerns about Boeing’s involvement. Since when did they build jet or indeed any engines? My fear is they will buy a share, import it to the USA and command sole rights in the world’s biggest aerospace market and given the… Read more »