Reaction Engines’ Sabre Rocket Engine Demo Core Passes Review
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far more trivial.
The Isp Quoted for open loop are pretty impressive. This means the majority of the mass can be accelerated to 1/5 orbital velocity and more importantly, pushed out of the majority of the earths atmosphere.
Curious us to see how the structural thermal design side will pan out if they plan SSTO.
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Exactly; in that regard it's not hugely different to conventional rocket engines using fuel to cool their nozzle. The Wikipedia page explains it fairly well; the helium loop is also used to power turbines, which is quite elegant.
https://www.google.co.uk/amp/s/amp.f...amp/1116242001
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Military applications i guess yes, but if you are expecting commercial flights under 2 hours as is oft sold as part of the marketing hype, forget it.
The helium loop is a closed cycle, it's not going to be a consumable. Compared with the quantity required for single-use applications - party balloons, weather balloons, blimps etc, it seems like a fairly modest proposition.
So it does look like the solution works great. (And an impressive engineering team, knocking down problems one-at-a-time.)
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
Apologies, I'm probably not going to explain this very well, but I'll have a go. Bear in mind that around 90% of the energy of an orbital vehicle is kinetic rather than potential; in other words, the real work is getting it up to speed rather than getting it up:
For a conventional rocket ascending almost vertically through the lower atmosphere (which is the most efficient profile for a non-winged vehicle) quite a lot of its thrust is "wasted" in resisting gravity. For instance, if a 10 ton rocket has engines generating 30 tons of thrust, 10 tons of thrust are required just to stop the thing accelerating downwards, so only 2/3 of that thrust actually causes the rocket to accelerate in the intended direction. Apparently this was a very significant factor for the Saturn 5, which (checking Wikipedia) weighed just under 3 million kg fully fuelled, and generated 34,000 kN of thrust (in other words, at the point of lift-off, only about 10% of the thrust was actually accelerating the vehicle). A winged vehicle is able to use the atmosphere to generate lift, which is how we are able to fly aircraft with a thrust:weight ratio of less than 1, so it's able to use a much greater proportion of that thrust to accelerate. Now combine the fact that the SABRE engine in air-breathing mode has just over 7x the specific impulse of a decent rocket engine (because no oxidiser is carried) and it's able to do so with around 1/7 the fuel burn of a rocket-powered winged vehicle.
This is only helpful for the first part of the launch, but by the time the Sabre engine is switched to internal oxidiser, my calculations have it travelling at ~1600m/s (Mach 5.5@94,000ft), which is 70% of the speed (2300m/s) that the Saturn 5 jettisoned its first stage (representing about 75% of its overall mass).
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I think what it's getting at is there are 2 factors: the different flight profile of a winged vehicle and the increased specific impulse of an air-breathing engine.
Apologies, I'm probably not going to explain this very well, but I'll have a go. Bear in mind that around 90% of the energy of an orbital vehicle is kinetic rather than potential; in other words, the real work is getting it up to speed rather than getting it up:
For a conventional rocket ascending almost vertically through the lower atmosphere (which is the most efficient profile for a non-winged vehicle) quite a lot of its thrust is "wasted" in resisting gravity. For instance, if a 10 ton rocket has engines generating 30 tons of thrust, 10 tons of thrust are required just to stop the thing accelerating downwards, so only 2/3 of that thrust actually causes the rocket to accelerate in the intended direction. Apparently this was a very significant factor for the Saturn 5, which (checking Wikipedia) weighed just under 3 million kg fully fuelled, and generated 34,000 kN of thrust (in other words, at the point of lift-off, only about 10% of the thrust was actually accelerating the vehicle). A winged vehicle is able to use the atmosphere to generate lift, which is how we are able to fly aircraft with a thrust:weight ratio of less than 1, so it's able to use a much greater proportion of that thrust to accelerate. Now combine the fact that the SABRE engine in air-breathing mode has just over 7x the specific impulse of a decent rocket engine (because no oxidiser is carried) and it's able to do so with around 1/7 the fuel burn of a rocket-powered winged vehicle.
This is only helpful for the first part of the launch, but by the time the Sabre engine is switched to internal oxidiser, my calculations have it travelling at ~1600m/s (Mach 5.5@94,000ft), which is 70% of the speed (2300m/s) that the Saturn 5 jettisoned its first stage (representing about 75% of its overall mass).
Apologies, I'm probably not going to explain this very well, but I'll have a go. Bear in mind that around 90% of the energy of an orbital vehicle is kinetic rather than potential; in other words, the real work is getting it up to speed rather than getting it up:
For a conventional rocket ascending almost vertically through the lower atmosphere (which is the most efficient profile for a non-winged vehicle) quite a lot of its thrust is "wasted" in resisting gravity. For instance, if a 10 ton rocket has engines generating 30 tons of thrust, 10 tons of thrust are required just to stop the thing accelerating downwards, so only 2/3 of that thrust actually causes the rocket to accelerate in the intended direction. Apparently this was a very significant factor for the Saturn 5, which (checking Wikipedia) weighed just under 3 million kg fully fuelled, and generated 34,000 kN of thrust (in other words, at the point of lift-off, only about 10% of the thrust was actually accelerating the vehicle). A winged vehicle is able to use the atmosphere to generate lift, which is how we are able to fly aircraft with a thrust:weight ratio of less than 1, so it's able to use a much greater proportion of that thrust to accelerate. Now combine the fact that the SABRE engine in air-breathing mode has just over 7x the specific impulse of a decent rocket engine (because no oxidiser is carried) and it's able to do so with around 1/7 the fuel burn of a rocket-powered winged vehicle.
This is only helpful for the first part of the launch, but by the time the Sabre engine is switched to internal oxidiser, my calculations have it travelling at ~1600m/s (Mach 5.5@94,000ft), which is 70% of the speed (2300m/s) that the Saturn 5 jettisoned its first stage (representing about 75% of its overall mass).
Noted your point thanks on the He being completely closed loop thermodynamic cycle, hadn’t realised this, thought they were ditching it overboard to get rid of waste heat.
So it does look like the solution works great. (And an impressive engineering team, knocking down problems one-at-a-time.)
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
We fly around with jet engines instead of rocket engines and that's one of the obvious reasons why. So why can't a jet engine be used at Mach 5? Well, air has to be slowed down from supersonic since shockwaves cause problems with the compressor and doing that makes it very hot and then you can melt your engine. REL's approach works up to M5 so it might help fighters or drones or even missiles get from runway to M5 (or less) with one engine and then endure longer.
I'm not an expert. Perhaps this explains better:
https://aviation.stackexchange.com/q...y-slow-it-down
Last edited by t43562; 22nd Oct 2019 at 20:49.
These snippets might be interesting:
The final amount of cooling is dependent on the temperature of the heat sink used in the test. “In the current campaign, we rejected heat to a water boiler; the test done several years back in the UK rejected heat to a liquid nitrogen boiler,” he notes. “The ultimate choice for a flight system as to what temperature you cool the air down to is an integrated trade study depending on the application. Our current thoughts are that for either Sabre or precooled jet engines, you would likely not need to cool down to cryogenic temperatures.”
....
For high-speed turbojet applications in the nearer term, the HTX significantly reduces compressor delivery temperature (T3). This maintains sea-level conditions in front of the compressor over a wider range of speeds, thus maximizing net thrust. For space access applications, the HTX will pass chilled air to a turbo-compressor and into a rocket thrust chamber, where it will be burned with subcooled liquid hydrogen fuel.
Reaction Engines is now conducting a detailed examination of the HTX prior to assembling updated versions more tailor-made for testing with jet engines—though this time in front of the engine rather than sitting in its exhaust. “We’d like to apply the learning from this test to see what can be done for precooled propulsion next,” says Dissel. “We are very interested in the ability to enable a fast jet engine and to be able to demonstrate that here on the ground and then transition that to flight-test opportunities. That’s the next progression, and this buys down a major risk element of the Sabre engine.”
.....
For an initial step, Reaction is studying the relatively small GE J85. “That’s our candidate at the moment. If we can show a jet engine operating at 20-40% past its design point, that would help prove the value proposition as quickly as possible,” he adds. The current precooler is sized for airflow rates of around 30 lb./sec. making it suitable for such an engine.
In the UK, where work is underway toward testing the core of the Sabre engine in 2021, Reaction is also starting an effort to evaluate the precooler with a Eurojet EJ200 under a £10 million ($13 million) project announced in July by the Royal Air Force’s (RAF) Rapid Capability Office. The project, which also involves BAE Systems and Rolls-Royce, is intended to inform engine studies for Britain’s future combat aircraft, the Tempest.
The RAF says the effort could also lead to lower costs both in terms of purchase and maintenance, a key focus of Britain’s Future Combat Air System Technology Initiative to research and develop new technologies that can be injected into UK Eurofighter Typhoons and Lockheed Martin F-35s as well as potentially feature in a future Typhoon replacement in the 2030s.
....
For high-speed turbojet applications in the nearer term, the HTX significantly reduces compressor delivery temperature (T3). This maintains sea-level conditions in front of the compressor over a wider range of speeds, thus maximizing net thrust. For space access applications, the HTX will pass chilled air to a turbo-compressor and into a rocket thrust chamber, where it will be burned with subcooled liquid hydrogen fuel.
Reaction Engines is now conducting a detailed examination of the HTX prior to assembling updated versions more tailor-made for testing with jet engines—though this time in front of the engine rather than sitting in its exhaust. “We’d like to apply the learning from this test to see what can be done for precooled propulsion next,” says Dissel. “We are very interested in the ability to enable a fast jet engine and to be able to demonstrate that here on the ground and then transition that to flight-test opportunities. That’s the next progression, and this buys down a major risk element of the Sabre engine.”
.....
For an initial step, Reaction is studying the relatively small GE J85. “That’s our candidate at the moment. If we can show a jet engine operating at 20-40% past its design point, that would help prove the value proposition as quickly as possible,” he adds. The current precooler is sized for airflow rates of around 30 lb./sec. making it suitable for such an engine.
In the UK, where work is underway toward testing the core of the Sabre engine in 2021, Reaction is also starting an effort to evaluate the precooler with a Eurojet EJ200 under a £10 million ($13 million) project announced in July by the Royal Air Force’s (RAF) Rapid Capability Office. The project, which also involves BAE Systems and Rolls-Royce, is intended to inform engine studies for Britain’s future combat aircraft, the Tempest.
The RAF says the effort could also lead to lower costs both in terms of purchase and maintenance, a key focus of Britain’s Future Combat Air System Technology Initiative to research and develop new technologies that can be injected into UK Eurofighter Typhoons and Lockheed Martin F-35s as well as potentially feature in a future Typhoon replacement in the 2030s.
Hmmm - sounds like the naysayers here might be looking at a meal of crow?
REL certainly sound like they're making good progress - if true, astonishing stuff - 1000 degrees quench in 1/20th of second.
A mile a second flight beckons...
REL certainly sound like they're making good progress - if true, astonishing stuff - 1000 degrees quench in 1/20th of second.
A mile a second flight beckons...
Oxygen is very heavy. That's the issue. Not carrying it (or carrying only the bit you need for the portion of your journey that is in space) makes a HUGE difference.
I've long thought that SCRAM jets would end up being the answer - when material technology caught up with the thermal requirements. But if this works with the current technology, that's great.
In the year 1800 (and for centuries before that), rapid long distance travel was around 6 mph using a sailing ship or horse drawn wagon. 100 years later, in 1900, that speed had increased to ~60 mph, using trains with steam locomotives. 100 years after that, by the year 2000, that speed was around 600 mph using jet aircraft. Is it that far-fetched that by the year 2100, that speed could be around 6,000 mph using sub-orbital transports?
So it does look like the solution works great. (And an impressive engineering team, knocking down problems one-at-a-time.)
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
But what is the problem again?
And I'm not trying to disparage this effort - only the marketing explanations look to me naive or dishonest.
To be more precise, this claim of better lift to orbit:
Carrying quite a bit of extra hardware so that you can fly obliquely through the atmosphere to save a small fraction of the oxidizer weight, then claiming that overcoming the thick atmosphere in this manner is an achievement, just does not quite add up.
As to London-to-Sydney: what will be the idea for redundancy here? One glitch in this pre-cooler and I imagine the consequences will be spectacular.
Again, not in the spirit of disparaging the actual science/engineering of this thing.
The advantage of SKYLON is that it can potentially launch a lot of 1 ton lumps in the time it takes a rocket launcher company to perform a single launch cycle. It could also bring them back again which, weirdly, makes things on the ground cheaper too; a module that's dead on arrival in orbit can be brought back and fixed, so that means one might be more willing to take a chance on less design analysis, testing, etc.
Wild guess here - it'll probably take roughly Concorde levels of maintenance to keep it flying.
The "flying" bit is good because it's a more efficient way to gain height than a purely ballistic ascent. The Saturn V burnt a whole heap of fuel just in the first couple of thousand feet, not really gaining any orbital velocity at all.
A pre-cooler packing it in does sound like a major event in flight. It might depend on thrust asymetry, but if it happened at a high enough height it might still make orbit on the other engine. What matters is getting that velocity up, and taking a little long doing might mean you get to a lower orbit. For example, the Shuttle sacrificed a little altitude for speed in its flight profile as a matter of course.
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Im still curious about solving structural heating issues. The hypersonic tests carried out by the USA have used the fuel as a surface coolant. If this fuel is now used for cooling the airflow, not sure how this will be dealt with. The RCC panels developed for
shuttle were horrendously difficult and expensive to produce (it took some convincing to spare one for destructive testing as part of the Colombia accident investigation as they were in extremely short supply). The vehicle will be exposed to extended periods sonic shock compressive heating, Be interesting to see if manufacturing has made RCC or similar technology more commercially viable.
I think the original design with the engines on the wing tips will be a no-go; the unstarts suffered by SR71 resulted in a few catastrophic losses. I can’t imagine that this additional level of yaw with next to no aerodynamic damping and limited RCS output would mean any form of asymmetry would be recoverable. That lends itself to something like a lightning engine configuration or some form of very rapid thrust control on any symmetric engine.
shuttle were horrendously difficult and expensive to produce (it took some convincing to spare one for destructive testing as part of the Colombia accident investigation as they were in extremely short supply). The vehicle will be exposed to extended periods sonic shock compressive heating, Be interesting to see if manufacturing has made RCC or similar technology more commercially viable.
I think the original design with the engines on the wing tips will be a no-go; the unstarts suffered by SR71 resulted in a few catastrophic losses. I can’t imagine that this additional level of yaw with next to no aerodynamic damping and limited RCS output would mean any form of asymmetry would be recoverable. That lends itself to something like a lightning engine configuration or some form of very rapid thrust control on any symmetric engine.
Last edited by VinRouge; 25th Oct 2019 at 09:41.
Im still curious about solving structural heating issues. The hypersonic tests carried out by the USA have used the fuel as a surface coolant. If this fuel is now used for cooling the airflow, not sure how this will be dealt with. The RCC panels developed for
shuttle were horrendously difficult and expensive to produce (it took some convincing to spare one for destructive testing as part of the Colombia accident investigation as they were in extremely short supply). The vehicle will be exposed to extended periods sonic shock compressive heating, Be interesting to see if manufacturing has made RCC or similar technology more commercially viable.
I think the original design with the engines on the wing tips will be a no-go; the unstarts suffered by SR71 resulted in a few catastrophic losses. I can’t imagine that this additional level of yaw with next to no aerodynamic damping and limited RCS output would mean any form of asymmetry would be recoverable. That lends itself to something like a lightning engine configuration or some form of very rapid thrust control on any symmetric engine.
shuttle were horrendously difficult and expensive to produce (it took some convincing to spare one for destructive testing as part of the Colombia accident investigation as they were in extremely short supply). The vehicle will be exposed to extended periods sonic shock compressive heating, Be interesting to see if manufacturing has made RCC or similar technology more commercially viable.
I think the original design with the engines on the wing tips will be a no-go; the unstarts suffered by SR71 resulted in a few catastrophic losses. I can’t imagine that this additional level of yaw with next to no aerodynamic damping and limited RCS output would mean any form of asymmetry would be recoverable. That lends itself to something like a lightning engine configuration or some form of very rapid thrust control on any symmetric engine.
It's not that the issues cannot be dealt with - Skylon would return much less steeply than the Space Shuttle so it would experience a longer heat soak but lower peak temperatures. The use of an unstressed silicon carbide shell on a space frame would protect it well enough without the need for the heavy duty tiles used by shuttle. Most of the structure would not need active cooling. The few areas that did require cooling could be cooled with a slight excess of the hydrogen fuel kept for the purpose.
The engines for TSTO are smaller but built of modules such that doubling or quadrupling certain modules would result in an engine suitable for Skylon. REL are apparently designing not one engine but a family. With luck this means that whatever other uses they can find for their technology, whether military or space-related or other will all help to retire many risks for Skylon and then the development cost will decrease and the interest in funding it increase.
Paper at EUCAS - ONERA TSTO study with Sabre
Last edited by t43562; 26th Oct 2019 at 15:53. Reason: clarify.
Ecce Homo! Loquitur...
Reference the heat loads of reentry - SpaceX has found a much simpler, and cheaper, option.....
If you’ve reduced the fuel load, and size of the fuselage, by up to 80%, you can afford the extra weight of the steel - if there is any, because it eliminates the need for the eight of tiles etc.
https://www.space.com/43101-elon-mus...-starship.html
https://arstechnica.com/features/201...little-closer/
If you’ve reduced the fuel load, and size of the fuselage, by up to 80%, you can afford the extra weight of the steel - if there is any, because it eliminates the need for the eight of tiles etc.
https://www.space.com/43101-elon-mus...-starship.html
https://arstechnica.com/features/201...little-closer/
Thread Starter
A lengthy and very interesting article on Reaction Engines background plus current and future developments.
For Reaction Engines, cool is the key
For Reaction Engines, cool is the key
Ecce Homo! Loquitur...
Can’t help thinking Sabre is like fusion - always just a few years away....
https://www.defensenews.com/global/e...c-fighter-jet/
Reaction Engines chases the elusive prospect of a hypersonic fighter jet
LONDON — A hypersonic propulsion company backed by Rolls-Royce, Boeing and BAE Systems has taken a step closer to developing an engine capable of powering combat jets and other aircraft at speeds of up to Mach 5 following tests of two subsystems vital to the success of the design.
British-based Reaction Engines said the recently completed tests of full-scale heat exchanger and hydrogen pre-burner subsystems validated the design of what are key components required to supply heat energy and air to the core of the air-breathing engine.......
The success of the trials on the heat exchanger, known as the HX3, and the pre-burner is another step in the right direction to maturing Reaction Engines’ technology. The latest tests follow trials undertaken in 2019 in Denver, where the company undertook high-temperature airflow testing for the Defense Advanced Research Projects Agency’s HTX program.
The company reported at the time that its proprietary ultra-lightweight heat exchanger used in the test was exposed to hypersonic conditions approaching 1,000 degrees Celsius, or roughly 1,800 degrees Fahrenheit. The heat exchanger performed its pre-cooler function by quenching about 1,800-degree Fahrenheit temperatures in less than one-twentieth of a second, according to the company.
Dissel said that together the three tests successfully demonstrate key subsystems not previously used in an aerospace environment.
“The company is very focused on maturing the subsystems that are fundamentally new to aerospace. Pre-cooler was the big one, and now with the innovative HX3 heat exchanger and pre-burner tests, these are three key components very specific to Sabre,” he told Defense News on March 5.....
When might we see Reaction Engines move to the next stage and conduct a Sabre engine core test? The company said last year that could happen in the next 12-18 months. Now, however, there appears less willingness to discuss dates.
Answering a question about timing, Dissel said Reaction Engines continually evaluates what can be done in terms of funding and customers, including the British government. “Certainly it is in the technology plan, but timing is somewhat funding-dependent.”
https://www.defensenews.com/global/e...c-fighter-jet/
Reaction Engines chases the elusive prospect of a hypersonic fighter jet
LONDON — A hypersonic propulsion company backed by Rolls-Royce, Boeing and BAE Systems has taken a step closer to developing an engine capable of powering combat jets and other aircraft at speeds of up to Mach 5 following tests of two subsystems vital to the success of the design.
British-based Reaction Engines said the recently completed tests of full-scale heat exchanger and hydrogen pre-burner subsystems validated the design of what are key components required to supply heat energy and air to the core of the air-breathing engine.......
The success of the trials on the heat exchanger, known as the HX3, and the pre-burner is another step in the right direction to maturing Reaction Engines’ technology. The latest tests follow trials undertaken in 2019 in Denver, where the company undertook high-temperature airflow testing for the Defense Advanced Research Projects Agency’s HTX program.
The company reported at the time that its proprietary ultra-lightweight heat exchanger used in the test was exposed to hypersonic conditions approaching 1,000 degrees Celsius, or roughly 1,800 degrees Fahrenheit. The heat exchanger performed its pre-cooler function by quenching about 1,800-degree Fahrenheit temperatures in less than one-twentieth of a second, according to the company.
Dissel said that together the three tests successfully demonstrate key subsystems not previously used in an aerospace environment.
“The company is very focused on maturing the subsystems that are fundamentally new to aerospace. Pre-cooler was the big one, and now with the innovative HX3 heat exchanger and pre-burner tests, these are three key components very specific to Sabre,” he told Defense News on March 5.....
When might we see Reaction Engines move to the next stage and conduct a Sabre engine core test? The company said last year that could happen in the next 12-18 months. Now, however, there appears less willingness to discuss dates.
Answering a question about timing, Dissel said Reaction Engines continually evaluates what can be done in terms of funding and customers, including the British government. “Certainly it is in the technology plan, but timing is somewhat funding-dependent.”