Reaction Engines’ Sabre Rocket Engine Demo Core Passes Review [Archive]

Lyneham Lad

14th Mar 2019, 16:56

Good to read that progress is being made.

Intro to an article on Aviation Week (https://aviationweek.com/future-aerospace/reaction-engines-sabre-rocket-engine-demo-core-passes-review?NL=AW-05&Issue=AW-05_20190314_AW-05_224&sfvc4enews=42&cl=article_2&utm_rid=CPEN1000003474208&utm_campaign=18793&utm_medium=email&elq2=4c5e46e553144e2bb45bdea919f904a1):-

The demonstrator core of Reaction Engines’ air-breathing Sabre rocket propulsion system has successfully passed a preliminary design review held in collaboration with the UK Space Agency and European Space Agency.

The assessment clears the way for a follow-on critical design review and the subsequent development and test of the core at a newly built facility in Westcott, England, in 2020. The complete engine, which will ultimately build on the core to incorporate a pre-cooler, rocket engine and ramjet, is designed to provide air-breathing thrust from the runway to Mach 5 and beyond for hypersonic aircraft and, in rocket mode, low-cost access to space.

unmanned_droid

14th Mar 2019, 19:21

diginagain

14th Mar 2019, 20:12

Excellent news
Indeed it is.

tartare

15th Mar 2019, 09:24

Hurry up guys.
I want to be able to fly to London from Sydney for the weekend.
Actually, on second thoughts, maybe I don't...

Onceapilot

15th Mar 2019, 12:14

So what is their proposed ££ per kilo to LEO?

Astronomic? :rolleyes:

OAP

JG54

15th Mar 2019, 19:05

According to figures released in 2011 -12, £650 / KG.

SpaceX are currently around $2,700 - 3,000 / KG on an expendable Falcon 9 for comparison.

unmanned_droid

15th Mar 2019, 19:25

According to figures released in 2011 -12, £650 / KG.

SpaceX are currently around $2,700 - 3,000 / KG on an expendable Falcon 9 for comparison.

So, you could expect that price to triple for a 'real life' figure and still be very competitive.

JG54

15th Mar 2019, 21:10

So, you could expect that price to triple for a 'real life' figure and still be very competitive.

Hmm. Maybe, but then again...

The current cost of a 'standard' Falcon 9 FT launch books at $50 million. The stated ambition is to get that figure below $10 million through reusability. Seventeen years ago, SpaceX didn't even exist. Now, they have approximately 65 - 70% of the commercial launch market, with all of the economies of scale which that brings. I, for one, wouldn't bet against them achieving that goal. Everyone else is looking like an 'also ran', and I see nothing on the horizon likely to change that.

Onceapilot

15th Mar 2019, 21:59

The difference being, that you can go and launch your payload on several pure rocket launchers today but, your payload will have evaporated before this "spaceplane" ever exists. :eek:

Like the Stirling engine, the efficiencies claimed for this regenerative heat cycle and cryogenic cooled, air-compressing, condensing and breathing/pure LOX/LH2 variable cycle rocket engine do not stack-up. The theoretical efficiency factors do not translate into the weight-limited reality that would be needed to make it competitive in orbital operation. The plant required to achieve the theoretical efficiencies is worthy of a ground based Nuclear powerstation.

Somehow, it is proposed that the efficiency of wing-borne lift within the atmosphere, burning Hydrogen fuel with a small amount of ingested air, cooled and compressed by energy from carrying extra liquid Hydrogen fuel that also provides cryogenic cooling of the air through bulky heat exchangers, will provide some earth shattering increase in efficiency. Of course, this also ignores the extra weight of the wing-borne structure and it's aerodynamic controls, the extra weight of the complex engines that have to be lifted all through the flight and reentry, the extra Hydrogen fuel/coolant to operate the air-breathing rocket, the take-off and landing apparatus, the extra propellant burn during the slow ascent and, the deadweight of the additional propellants that are needed to accelerate the relatively slow spaceplane to orbit after the interface between wing-borne/air breathing and the pure rocket/ballistic operation above the atmosphere, compared to a non wing-borne multi stage pure rocket.

There is also the question about the construction of a large spaceplane that is intended to be re-used, the weight of the structure to survive reentry, heating, flight loads and landing. Oh yes, landing. On a runway, like the takeoff?
However, the benefit of wing-borne lifting a ballistic rocket to some altitude and speed for launch to orbit (like the Pegasus launch system) does have some performance advantages but, of course, there are the practicalities of size.
Now, there are certainly interesting possibilities for high altitude atmospheric flight but, I reckon that the the multi stage rocket has got orbital lifting well and truly wrapped up for generations.

OAP

Onceapilot

15th Mar 2019, 22:08

Sorry, forgot to mention the weight of the Helium based power/heat energy transfer system, but Helium is light, right?:)

OAP

t43562

17th Mar 2019, 17:34

Onceapilot:
Like the Stirling engine, the efficiencies claimed for this regenerative heat cycle and cryogenic cooled, air-compressing, condensing and breathing/pure LOX/LH2 variable cycle rocket engine do not stack-up. The theoretical efficiency factors do not translate into the weight-limited reality that would be needed to make it competitive in orbital operation. The plant required to achieve the theoretical efficiencies is worthy of a ground based Nuclear powerstation.
ESA think it might. The US AFRL think it might. The people involved are actual rocket scientists one of whom also worked at JET on nuclear fusion. Weight limiting is the whole point because LOX is very dense and they aim to have to carry less.

The whole point of their cycle is the way it uses energy that the LACE (Liquid Air Cycle Engine) concept wasted. The innovation is the thermodynamic cycle and the very lightweight heat exchangers that enable it.

Somehow, it is proposed that the efficiency of wing-borne lift within the atmosphere, burning Hydrogen fuel with a small amount of ingested air, cooled and compressed by energy from carrying extra liquid Hydrogen fuel that also provides cryogenic cooling of the air through bulky heat exchangers, will provide some earth shattering increase in efficiency. Of course, this also ignores the extra weight of the wing-borne structure and it's aerodynamic controls, the extra weight of the complex engines that have to be lifted all through the flight and reentry, the extra Hydrogen fuel/coolant to operate the air-breathing rocket, the take-off and landing apparatus, the extra propellant burn during the slow ascent and, the deadweight of the additional propellants that are needed to accelerate the relatively slow spaceplane to orbit after the interface between wing-borne/air breathing and the pure rocket/ballistic operation above the atmosphere, compared to a non wing-borne multi stage pure rocket.
You're implying that these people can't do basic sums about weight which if you think about it would be quite unlikely. In fact they are an engine company and their reason for designing a notional spaceplace (Skylon) was to demonstrate that the sums in fact did work out and that the weight of the vehicle was amply compensated for by the reduction in the amount of LOX that it had to carry. On top of that the US AFRL has done work on other concepts with smaller versions of the same engine and a TSTO orbit configuration and considered it feasible.

There is also the question about the construction of a large spaceplane that is intended to be re-used, the weight of the structure to survive reentry, heating, flight loads and landing. Oh yes, landing. On a runway, like the takeoff?
However, the benefit of wing-borne lifting a ballistic rocket to some altitude and speed for launch to orbit (like the Pegasus launch system) does have some performance advantages but, of course, there are the practicalities of size.
Now, there are certainly interesting possibilities for high altitude atmospheric flight but, I reckon that the the multi stage rocket has got orbital lifting well and truly wrapped up for generations.

That depends on many factors including whether they can recover upper stages. It also means that you indeed need a landing pad in a place where you can accept the risk of a rocket falling somewhere perhaps not exactly where it should. Rockets are very unreliable in comparison to aircraft. If totally reused they might get to a much higher level but they're not thus far etc.

Skylon's cost has always presented problems because it was a big upfront investment. With cost of that investment entirely laid at the door of one vehicle it would compete with a fully reusable rocket and the issue is why would anyone go to that effort to be "as good". On the other hand if you start using the SABRE engine in military aircraft and perhaps start with smaller TSTO spaceplanes and if there are numerous spinoffs for the heat exchanger technology in conventional jet engines and .... nuclear submarines or whatever... then the economics could see quite a big change.

So the real problem is whether the market will be big enough to support all these companies. It might be growing but I don't think that's easy to predict. The proposed internet satellite constellations might be the way to have enough launches to justify the many ongoing developments by various companies and I think the SpaceX one is important to their plans for making launches cheaper but I wonder if there are slightly too many of those constellations in planning.

Onceapilot

17th Mar 2019, 20:18

Thanks for your reply t43562.
So, let us cut to the chase....There are Military possibilities for partial/air breathing Scramjet etc high altitude/high speed vehicles that must incorporate cryogenic elements. However, the technologies are underdeveloped, expensive and not yet crucial so, it gets back-burnered and funded from misdirected technology development, and sci-fi spaceplane smoke and mirror funding. :)
Good luck with your (notional) spaceplane.
BTW, Charge air cooling of subsonic commercial aircraft gas turbines is already proven to be inefficient, even if the heat exchanger was weightless.:*

OAP

t43562

8th Apr 2019, 09:54

https://www.bbc.co.uk/news/science-environment-47832920

UK engineers developing a novel propulsion system say their technology has passed another key milestone.

The Sabre air-breathing rocket engine is designed to drive space planes to orbit and take airliners around the world in just a few hours. To work, it needs to manage very high temperature airflows, and the team at Reaction Engines Ltd (https://www.reactionengines.co.uk) has developed a heat-exchanger for the purpose.
This key element has just demonstrated an impressive level of performance. It has shown the ability to handle the simulated conditions of flying at more than three times the speed of sound. It did this by successfully quenching a 420C stream of gases in less than 1/20th of a second.
...

https://www.reactionengines.co.uk/news/reaction-engines-test-programme-successfully-proves-precooler-capability-supersonic-heat-conditions

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.

They're apparently at Mach 3.3 conditions and ramping up to Mach 5 conditions and think it's all going better than expected so far.

https://www.reactionengines.co.uk/application/files/8215/5466/7108/HTX_Assembly_Animation.mp4

Lyneham Lad

8th Apr 2019, 12:01

Also reported in The Times today.
Breakthrough for hypersonic jet that could fly at Mach 25 (https://www.thetimes.co.uk/article/breakthrough-for-hypersonic-jet-that-could-fly-at-mach-25-mgvltfltc?shareToken=60ca0540136740c8ef1d2b209b5c8f60)

Onceapilot

8th Apr 2019, 20:00

t43562

8th Apr 2019, 22:02

So, the BS about "spaceplane" continues. I will not book my ticket. :) As I have said, this engine project has a Military purpose. The fact that todays general population can be deceived is unsurprising. :)
OAP

It would be difficult to book any tickets as humans are not likely to be the cargo in any such spaceplane. The "general population" is a term which such a lot of people define as not including themselves and I wonder at that because it's usually only in a very narrow area that anyone isn't "general" and from so many angles that they are fully as ignorant as everyone. I do wonder what the motivation really is in ignoring the experts though.

Onceapilot

9th Apr 2019, 07:06

It would be difficult to book any tickets as humans are not likely to be the cargo in any such spaceplane.

So, let's see the hype drop the transport BS and stick to the only realistic reason to develop air breathing Mach 25 engines....possible military purposes. :)

OAP

esa-aardvark

9th Apr 2019, 09:33

This concept was around when I worked (I retired 1996!). The UK government
was not keen, if I remember correctly it was made 'secret'. No one else could build it.

ORAC

22nd Oct 2019, 06:48

http://aviationweek.com/aircraft-propulsion/reaction-engines-precooler-passes-hypersonic-testReaction Engines Precooler Passes Hypersonic Test

Reaction Engines’ precooler has successfully run at Mach 5 temperatures, validating for the first time the capability of the novel heat exchanger design to operate at hypersonic flight conditions for atmospheric and space access applications.

The breakthrough test is pivotal to Reaction’s goal of using the lightweight heat exchanger (HTX) to boost high-speed turbojets for supersonic and hypersonic vehicles as well as for developing the company’s Synergistic Air-Breathing Rocket Engine (Sabre), which is targeted at low-cost, repeatable access to space.

Forming the culmination of a DARPA contract awarded in 2017, the Mach 5 run took place in the second week of October at the company’s TF2 test facility at the Colorado Air and Space Port near Watkins. Established on an all-new site just 22 months ago, the high-speed test comes seven months after the heat exchanger demonstrated operation at supersonic conditions equal to Mach 3.3. Heated air for the tests is generated by a General Electric (http://awin.aviationweek.com/OrganizationProfiles.aspx?orgId=31624) J79, which operated at military power for the supersonic runs and in maximum afterburner for the tests up to Mach 5.

“We had high confidence but, until these tests over the past six months, there was just an assumption this technology would work at these high temperatures because there was no way to test it. So, I’m very glad it came off,” says Adam Dissel, president of Reaction Engines. Although initial tests in the UK in 2012 using a Rolls-Royce (http://awin.aviationweek.com/OrganizationProfiles.aspx?orgId=20257) Viper turbojet demonstrated the ability of the HTX to chill air from ambient to under -120C (-184F), the larger-scale evaluations in the U.S. were viewed as the true acid test. “Taking the whole device up to these high temperatures as part of an integrated system is quite a design challenge,” he adds.

Describing the test result as a “major moment in the development of a breakthrough in aerospace technology,” Reaction Engines CEO Mark Thomas says: “We are seeing significant interest from a range of potential customers and technology partners.”.........

Following the activation of the afterburner system on the J79, the team took a build-up approach toward hitting the high Mach target. “Through early summer, we tested multiple points of the envelope, eventually running up to about Mach 4.3. We tested at various airflow rates with varying coolant rates of helium mass flow passing through the precooler,” says Dissel. The approach yielded “a good understanding of the physics and the air-pressure drop across the matrix as it transitions across the precooler,” he adds. The results also indicate the HTX responds quickly to variable airflow conditions. “The precooler has behaved amazingly well,” Dissel says. “It adapts to changing flow nearly instantly, so that was good to see. It’s part of a function of how light it is, so the precooler is not relying on thermal inertia to survive.”

By the time tests got to Mach 4.3 levels, however, the group realized that the test infrastructure was approaching heating limits before the precooler could reach its planned test condition. “The challenge we have had on the facility side was tricking it into thinking it’s flying on a Mach 5 aircraft. To ensure we had the right condition, we took a couple of months to make some upgrades and added insulation blankets to reduce the heat transfer into the walls of the airflow ducts and plenum,” he adds. The upgrade, which also involved increasing the mass flow of the helium cooling circuit, made sure “we were ready to go for gold on the max condition,” Dissel notes.......

Ascend Charlie

22nd Oct 2019, 10:53

But where does the heat go after being taken out of the incoming airflow? If it transfers to liquid helium in the pre-cooler, what do they do with a pile of hot helium?

VinRouge

22nd Oct 2019, 11:38

But where does the heat go after being taken out of the incoming airflow? If it transfers to liquid helium in the pre-cooler, what do they do with a pile of hot helium?

I think the design has a significant part of the heat load absorbed by the LH2 fuel which is then used in a conventional sense. The open loop design is shut off when not enough Bernoulli’s can be collected up top, at M5+. By this stage, air resistance is so low that the mechanics of getting to orbit become
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.

pasta

22nd Oct 2019, 12:09

I think the design has a significant part of the heat load absorbed by the LH2 fuel which is then used in a conventional sense.
Exactly; in that regard it's not hugely different to conventional rocket engines using fuel to cool their nozzle. The Wikipedia (https://en.wikipedia.org/wiki/SABRE_(rocket_engine)) page explains it fairly well; the helium loop is also used to power turbines, which is quite elegant.

VinRouge

22nd Oct 2019, 13:34

Exactly; in that regard it's not hugely different to conventional rocket engines using fuel to cool their nozzle. The Wikipedia (https://en.wikipedia.org/wiki/SABRE_(rocket_engine)) page explains it fairly well; the helium loop is also used to power turbines, which is quite elegant.
like to know where all of the helium will come from though. It’s not exactly a massively abundant element.

https://www.google.co.uk/amp/s/amp.freep.com/amp/1116242001

ORAC

22nd Oct 2019, 14:17

https://www.newscientist.com/article/2095196-huge-newfound-deposit-of-helium-will-keep-mri-scanners-running/

VinRouge

22nd Oct 2019, 14:50

https://www.newscientist.com/article/2095196-huge-newfound-deposit-of-helium-will-keep-mri-scanners-running/point is, not enough for widespread commercialisation, mindful of other uses.

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.

pasta

22nd Oct 2019, 15:24

point is, not enough for widespread commercialisation, mindful of other uses.

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.

balsa model

22nd Oct 2019, 15:32

pasta

22nd Oct 2019, 17:04

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.
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).

VinRouge

22nd Oct 2019, 19:10

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).
It’s also how the falcon 9 can get back to launch site with minimal fuel (plus the significantly reduced mass on the 1st stage) A lot of the fuel has been expended giving the “up” velocity vector, whereas the 2nd stage gives much more to the horizontal component, which in the case of SABRE open loop can only kick in once aerodynamic drag has a minimal effect.

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.

t43562

22nd Oct 2019, 20:21

t43562

22nd Oct 2019, 20:29

xexgtudp8yA

t43562

22nd Oct 2019, 21:15

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.

tartare

22nd Oct 2019, 21:48

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...

tdracer

22nd Oct 2019, 22:27

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.

Exactly! Most of the mass of rocket launch into space is fuel/oxidizer (at liftoff, the Saturn V was ~95% fuel/oxidizer by mass). And if you're burning H2 as your fuel, you need ~8x that mass of O2. Being able to use oxygen from the air is a huge carrot that can justify quite a bit of extra equipment mass (particularly when you start talking reusable).

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?

msbbarratt

24th Oct 2019, 20:04

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.

There's a big opportunity for something like this in in-space assembly plans. To build a big satellite on the ground is very expensive - big facilities, big transport problems, big assembly hall for the launcher stack, big test faciliites, etc. Whereas if you can launch, say, 1 ton lumps and reliably join them up in orbit, you save all that cost on the ground. And there's no real limit on how big the final spacecraft is.

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.

VinRouge

25th Oct 2019, 09:00

t43562

26th Oct 2019, 15:50

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.

To start with, Skylon is not on the short term agenda because the development cost would be enormous. REL isn't sitting on that kind of money so they have to find way to prove the entire concept and retire the risk cheaply. My impression is that their original management thought this was a bit circuitous and pointless and had large amounts of investment promised to them which then evaporated at some point. Hence the new management and small investments from BAE, Rolls and Boeing and the change of focus to Two Stage to Orbit (TSTO) designs and the search for other applications in jet engines. In TSTO designs the re-entry problem is gone, as I understand it. The SABRE-powered TSTO vehicle doesn't enter orbit and then have to return from it - it carries a rocket on top or in a mission bay which does the last part of the flight. Although all heat issues are not gone the severity is greatly reduced.
https://cimg0.ibsrv.net/gimg/pprune.org-vbulletin/456x378/skylon_reentry_255be07df019ea8c65e0d689b7395882ea477b1d.png

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 (https://forum.nasaspaceflight.com/index.php?action=dlattach;topic=45914.0;attach=1570899;sess= 43773)

ORAC

26th Oct 2019, 17:13

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-musk-explains-stainless-steel-starship.html

https://arstechnica.com/features/2019/09/after-starship-unveiling-mars-seems-a-little-closer/

Lyneham Lad

19th Feb 2020, 10:37

A lengthy and very interesting article on Reaction Engines background plus current and future developments.

For Reaction Engines, cool is the key (https://www.flightglobal.com/flight-international/for-reaction-engines-cool-is-the-key/136746.article)

ORAC

17th Mar 2021, 08:54

Can’t help thinking Sabre is like fusion - always just a few years away....

https://www.defensenews.com/global/europe/2021/03/15/reaction-engines-chases-the-elusive-prospect-of-a-hypersonic-fighter-jet/

Reaction Engines chases the elusive prospect of a hypersonic fighter jet

LONDON — A hypersonic propulsion company backed by Rolls-Royce (https://www.defensenews.com/global/europe/2020/08/21/rolls-royce-backs-hypersonic-power-specialist-reaction-engines-with-new-investment/), 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 (https://www.defensenews.com/global/europe/2019/07/18/british-military-scrambles-to-speed-up-work-on-hypersonic-engines-weapons/) 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.”

etudiant

17th Mar 2021, 13:08

[QUOTE=ORAC;11010418]Can’t help thinking Sabre is like fusion - always just a few years away....

Exactly. As noted above, the presumed cost savings from reuse-ability of HOTOL have been largely met by Space-X's approach.
That leaves the technology searching for a mission, but hypersonic fighters are just as operationally dubious as the US Army's pursuit of a 1000 mile range cannon.

t43562

28th Apr 2023, 17:33

https://aviation-xtended.co.uk/ep-171-reaction-engines/

With the UK leading aerospace company Reaction Engines now leading the way in technology application from space rockets to Formula 1 and into today’s market for sustainable flight, we have an exclusive opportunity to speak to Mark Thomas, Reaction Engines Chief Executive Officer, about the company, its products and its exciting future innovations.

There is a section of the podcast referring to the hypersonic UAV shown in concept photos below - apparently work is underway.

https://i0.wp.com/aviation-xtended.co.uk/wp-content/uploads/2023/04/HVX-Concept-V-Formation.jpg?resize=1024%2C576&ssl=1

Asturias56

29th Apr 2023, 08:20

It was in 2019 when this thread started...............

t43562

1st May 2023, 10:21

It was in 2019 when this thread started...............

Indeed and things have happened - including various commercial applications of the heat exchanger technology, and a "higher speed" test of their precooler for AFRL which handled 10MW of heat transfer proving that it could handle high flow. https://twitter.com/reactionengines/status/1626250265828507648

If you cannot see the Twitter link (like me!) this is next best:
https://reactionengines.co.uk/fct-testing/

Also tests of the preburner that is the "starter motor" of a SABRE engine which puts heat into the system via their HX3 heat exchanger until the vehicle is moving fast enough that the heat can be supplied by slowing incoming air:

https://reactionengines.co.uk/air-breathing-rocket-engine-technology-update-july-2022/

This UAV (announced Jul 2022 IIRC) will presumably let them advance the TRLs of various bits of their technology although it will be a precooler in front of a jet engine rather than an air-breathing rocket. I'm sure they want it to fly but it probably doesn't need to to still help them.

Asturias56

1st May 2023, 11:02

t43562

1st May 2023, 16:57

they originally were talking about 2020 for first ground test of the whole engine IIRC

this months "Flight " has an interesting article on the cancelation of the USAF ARRW AGM-183A hypersonic system - "numerous technical challenges"
Well, I think they have chronically too little money but at least they've moved the state of the art ahead some steps and nobody in the future history of the world ever again needs to doubt that those things are possible. That's a solid achievement. There's a report on how they spent some government money which might be interesting even if you only dip into it:

https://www.gov.uk/government/publications/synergetic-air-breathing-rocket-engine-sabre-programme-evaluation-report-2022/synergetic-air-breathing-rocket-engine-sabre-programme-evaluation-report-2022#synergetic-air-breathing-rocket-engine-sabre-programme-evaluation-report-2022

W.R.T. the AGM-183A I can see how all these things are hard and in that case the performance is either OK or not acceptable. With this precooled jet engine there's obviously a similar judgement but one can approach it gradually. I have to speculate but Rolls Royce have at least run a gas turbine on hydrogen recently:

https://www.bbc.co.uk/news/business-63758937

One has to hope that Rolls/REL/BAE can apply what they learned to a smaller engine.

So assuming that they have an engine which they can make run on hydrogen it should fly without any precooling at all and all the precooling will do is to enable it to go faster than it would have otherwise. Mach 5 would be the absolute upper limit but it might not need to approach more than a fraction of that to prove it is working properly and that would be great for REL.

Even testing such an engine on a bench might have value for them - and they have a "bench" in Colorado which might be suitable.

I'm sure that there is a large chance of failure