Reaction Engines and Rolls-Royce have entered a new strategic partnership to develop high-speed aircraft propulsion systems.
Reaction Engines is the company responsible for SABRE (Synergetic Air-Breathing Rocket Engine) which they describe as a new class of aerospace propulsion with the potential to provide air-breathing thrust from standstill on the runway to speeds above Mach 5 in the atmosphere. The scalability of SABRE allows for multiple applications whilst delivering the fuel efficiency of a jet engine with the high-speed capability of a rocket.
Reaction tests SABRE precooler at Mach 5 conditions
Reaction Engines’ proprietary pre-cooler technology is key to SABRE. As previously reported in The Engineer, 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 part of the agreement both companies will investigate applications for Reaction Engines’ thermal management technology within civil and defence aerospace gas turbine engines and hybrid-electric systems.
“We have been working closely with Reaction Engines for the past two years, including exploring the potential of high-Mach systems for defence applications, and I am delighted that we are able to strengthen that relationship,” said Mark Thompson, Director of Global Strategy & Business Development, Rolls-Royce.
“Reaction Engines’ thermal management skills, added to our suite of existing technologies and capabilities, will further assist us as we explore opportunities in supersonic and hypersonic aviation,” Thompson added. “Building on our many decades of innovation, we will also explore the use of Reaction Engines’ technology within our aerospace gas turbines and its potential application in future hybrid-electric propulsion systems, as we look to make flying ever more efficient and sustainable.”
Additionally, Rolls-Royce is making a further investment in Reaction Engines as part of a wider funding round. The two companies have been working together since 2018, including on the first phase of a UK Ministry of Defence contract to undertake design studies, research, development, analysis and experimentation related to high-Mach advanced propulsion systems.
“This strategic partnership is about developing market ready applications for Reaction Engines’ technology in next generation engines and is a significant step forward for our technology commercialisation plans,” said Mark Thomas, Chief Executive of Reaction Engines. “Our proprietary heat exchanger technology delivers incredible heat transfer capabilities at extremely low weight and a compact size. We look forward to expanding our international collaboration with Rolls-Royce…to bring to market a range of applications that will transform the performance and efficiency of aircraft engines, enable high speed – supersonic and hypersonic – flight and support the drive towards more sustainable aviation through innovative new technologies.”
Where does all the heat extracted from the incoming air go to. Is all that energy re-used in some way?
Isn’t a condition of this system that you have liquid Hydrogen as a fuel /coolant ?
The heat extracted from the air goes to helium circulating in the heat exchanger. This is used to run the compressor fans and the rest of it goes to the liquid hydrogen fuel. You actually need more fuel to cool the air than for the engine so the excess is used like an afterburner.
just wanted to say it is great to see that a british company is coming up with ideas like this.
The heat goes into the hydrogen fuel which is extremely cold
This may allow VG to develop a Mach 5 business jet instead of Mach 3
https://www.syfy.com/syfywire/virgin-galactic-and-rolls-royce-launching-new-mach-3-superjet
If memory serves me correctly the heated air is (necessarily) cooled down by heat transfer to a closed cycle helium heat exchanger – that dumps heat into the liquid hydrogen; thence warming it up so that it may be burnt more effectively. I suspect that the constraint of how much hydrogen is vapourised relates to the the need to stop the engine inlet duct getting too hot.
A jet engine can benefit from cooling of compressed gas – and the improved energy efficiency resulting.
I do remember we talked to some engineers suggesting that static components, such as vanes (or casings), could be made multifunctional (hence avoiding any weight penalty) heat-exchangers. However that was some years back and it would be interesting to know, of Rolls-Royce, if they are, now, intending using their own compact heat-exchanger manufacturing technology or that of Reaction Engines.
At least in the Sabre engine, it goes into evaporation of the liquid hydrogen fuel.
In the original SABRE design, a helium loop transferred heat from the air to the liquid hydrogen fuel, chilling the air to just above its liquifaction point. In the process, the temperature difference between air & fuel was used in a heat engine to drive the turbomachinery.
Can that thermal exchanger be fitted in the exhaust air to cool it for stealth (IR) signature applications?
Could someone please explain how the high air temperature occurs. The compression ratio of reaction engines is low, so the air preheat from compression is low, added to which the air temperature at high altitudes is far below ground level values. The combustion temperature is what drives the engine, the higher the better usually. So, am I missing something, or, where does the high air temperature actually come from in this engine. The website does not explain this either.
Isn’t this a misguided project since, to reach carbon zero, we need to stop using fossil-fueled aircraft by 2050. It would be better to focus on high-efficiency hydrogen powered aircraft to replace the current fleet.
It’s to do with the adiabatic compression of the air as it rams into the front end of the engine. At supersonic (or hypersonic) velocity it can’t deflect around the engine. Even at Mach 2, the exterior of Concorde reportedly got up to around 100°C even though it was flying through air at -60°C.
If you stop something that is moving fast to measure its temperature, it will be hot. Try putting your fingers in a fast jet of cold water. Or don’t as you will burn them badly (I know). If you stop air travelling at a certain Mach number, you can multiply its temperature by approximately ” 1+ (0.2*M^2)” where M is the Mach number. This is all in Kelvin so minus 60 C is plus 213 K. The answer for Mach 2 at altitude in -60C is 383 K or 110 Deg C. Hence why Concorde could grow by 250mm in flight., and going any faster in an aluminium aircraft is very brave.
Thanks Ian Watson-Walker for pointing out the issue of frictional heat. Re-entry of spacecraft have skin-temperatures of almost 2000K.
Having dug a little more into what SABRE is, I think that the cooling of the inlet air is because the engine has a compressor which works better the lower the air temperature. I’ve not found what drives the compressor as yet, but this might be the purpose of the cooler, it also vaporises the liquid hydrogen fuel of course.
SABRE is a terrific concept (so far as I can understand it) and I hope that it gets all the necessary funding to take it forward. i would request that the editors keep us updated on this fascinating topic.
My point really was that to implement this technology for civil aviation (which has been suggested), you don’t just have to develop the engine, you have to have the liquid hydrogen infrastructure as well as integrating storage of a cryogenic low density fuel into a civil aircraft structure. Its all possible, but is there enough of a market to pay for it?
Although the ambient temperatures are quite low, as air passes through a shock train, it gets heated quite largely. For example, even at Mach 4, an efficient mixed compression intake can result in ~800K towards the choked end of diffuser.