And, IIRC, this was compounded by Helium's 'super-critical' properties under those conditions.

To his surprise, REL seemed to have significantly under-stated the performance...
I would not expect the helium to be cold enough to exhibit superfluid properties (which I assume is what you mean). At 1 atmosphere it is liquid below 4.2 K but does not become superfluid until around half that. No doubt RE's working pressure and temperature are somewhat higher. So a claimed performance significantly below the superfluid's calculated capabilities would be sensible enough.
please inform yourself:


supercritical, not "superfluid"
 
Reaction Engines, Inc. (REI), the U.S. subsidiary of Reaction Engines Ltd. (REL), Culham UK, a leader in the design, manufacture, and application of thermal management solutions for the aviation, space, energy, and transportation sectors, today announced the successful completion of the Foreign Comparative Testing (FCT) campaign of Reaction’s revolutionary engine precooler heat exchanger at its Colorado high-temperature test facility. First announced in July 2022, the FCT test program was conducted in partnership with the U.S. Department of Defense and U.S. Air Force Research Laboratory (AFRL) and was aligned with the Air Force FCT goal to assess maturing technologies that could meet defense needs.
 
Mark Thomas, Reaction’s chief executive, said its focus was developing hypersonics for the military. It is part of a programme with Rolls-Royce and the Ministry of Defence that aims to fly a demonstrator by the middle of the decade. “I am confident we will manage that,” Thomas said. The civilian market is less of a priority. “It is certainly something we think about, but it is very, very difficult. Most of our efforts are now focused on military applications, then other commercial applications for the cooling technology.”

 
A report dated 2022, 'Preparing for Lift-Off.' Not paywalled though you have to give name and email to download if that's a problem (it asked for company name, but 'N/A' was accepted). They emphasise the military and responsive space launch applications, starting with the HVX project already discussed as 'Generation 1', a 2STO with airbreathing reusable 1st stage and expendable 2nd as 'Generation 2' and a Skylonoid as 'Generation 3.'

Preparing for lift-off.

How responsive launch will be critical to defence in space.

Thought Leadership
The need to rapidly respond to events and threats within the space domain has become more evident with the recent geopolitical situation highlighting the importance of access to information to build resilience. This paper explains what responsive launch entails, what it could look like, and highlights the case for a UK capability towards responsive launch.
 

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None of the concepts illustrated should be taken as actual representations of what the vehicles would look like. Even HVX/Generation 1 is notional. Still, it's interesting to speculate. An older illustration of what appears to be Generation 2 (below) apparently has SABRE engines and a problem with heating of the fuselage by the exhaust plumes is addressed by placing the engines well back. The new rendering seems to just use the precooler technology in front of more conventional engines while Generation 3 has some differences from the original Skylon. The Generation 3 concept above seems to have a shorter tail (presumable to mitigate fuselage overheating again), lacks canards and has a new TPS and LERXs.
 

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Simply following the money as SABRE / Skylon weren't revenue generating products
I understand, but still, not with a bang but a whimper... The initial driving objective was an SSTO HTHL ABRLV, and yet, here we are - again... Despite my fairly intimate understanding of the monumental obstacles and resulting scepticism, I was kind of rooting for the original team, and hoping they eventually actually *could* turn SABRE/Skylon into revenue generating orbital products in civilian, commercial, or defense use.
 
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Most of the original team retired over 5 years ago now

Basically, reusable multi-stage VTVL rockets are much lower risk and development cost and time. Only the military seems to be semi interested in the greater cross range / orbit flexibility for splaceplanes, but not interested enough to pay massively for it.
 
I was more struck by all the cool entrepreneur dudes who thought they could knock up a hypersonic craft in a few years with a few bucks.
The major aerospace companies have struggled to produce anything hypersonic larger than a cruise missile despite efforts since the 1960s and these dudes think they will just rock up and do it?
Is there no bubble these folks won't exploit? SST, SSTO, eVTOL and go knows what else.

Like all these wheezy ideas, you've got to have a willing customer with a market. No airline has yet really pushed for such craft, the profit margins would barely stack up.
If the USAF really wanted such capability they would have been knocking down the doors at the PhantomSkunkWorks by now.
 
Just as the first 'Oil Crisis' made civilian SSTs and big hovercraft (*) uneconomic, IMHO, the only customers for SABRE this decade are military aviation and super-biz-jets...

Perhaps its time will come in the 2030s ??

*) For the record, our local Coastguard / RNLI / F&R have a road-trailered, RIB-sized hovercraft with water-jetting gear for nimbly extricating people beset on tidal coast's wide sand and mud banks...
 
I was more struck by all the cool entrepreneur dudes who thought they could knock up a hypersonic craft in a few years with a few bucks.
The major aerospace companies have struggled to produce anything hypersonic larger than a cruise missile despite efforts since the 1960s and these dudes think they will just rock up and do it?
Is there no bubble these folks won't exploit? SST, SSTO, eVTOL and go knows what else.

Like all these wheezy ideas, you've got to have a willing customer with a market. No airline has yet really pushed for such craft, the profit margins would barely stack up.
If the USAF really wanted such capability they would have been knocking down the doors at the PhantomSkunkWorks by now.
For every Tesla there are dozens of Juiceros. As usual, Burning Man is the punchline to the article.

 
This sounds WAY too familar... I'm thinking I've heard of this before in relation to the RASCAL program. I seem to recall a report showing a "deep-cooled turbo-rocket" called the "KIL-N" cycle I think?? Basiclly it used an RL-10 engine fed by LH2 and Liquid Air drawn from a set of compressor intakes and heat-exchangers...

I'll see what I can find again.

Randy
Any luck finding that?


...There have been concepts that allow for compound curves in structures that can be fit in a conventional cylindrical cargo shroud/bay. They involve stacking smaller segments rotated 180 degrees from each other, thus aligning them along one axis as a cylinder. When orbit has been achieved, the whole stack is removed, the segments rotated, and as much as a 1/4 arc of a complete toroid results. Note that a 1/4 arc required a serious lift booster, and the more conservative concepts I've read about called for arcs of only 1/6 or 1/8.

Wish I still had those papers that discussed these concepts. The diagrams were actually quite detailed in the stacking and deployment phase.
It's like the F-35's 3-bearing Nozzle. 3 sections with 30deg angles on them. Spin the center section 180deg and it sits mostly straight, while if you spin that center section 180deg the other way it forms a 90+deg curve.


In 1963 the US Army had their nuclear energy depot. Portable reactors to turn (air nitrogen ) and water's hydrogen into ammonia methanol or hydrogen fuels. They studied DH Caribou transports and UH-1 choppers turbines with NH3. I have the pdf somewhere. Not very encouraging. Methanol and ammonia have half the energy of kerosene. Hydrogen is doomed by storage issues.
Just means your fuel tanks need to be twice the size. Too bad nuclear reactors are too complex to operate by grunts.


Well then the twitter headline is misleading, damn it. Stupid clickbait... :rolleyes:
Clickbait on twitter? I'm about to die of not-surprise. (/sarcasm)


This ammonia thing is about generating liquid hydrogen for fuel cells or to burn. REL is betting that producing the LH2 from renewables power to liquid it should then be combined with nitrogen to make ammonia as this has some storage and transportation advantages over LH2. But still obvious issues. REL's spinoff tech here is to be able to rapudly crack the ammonia to liberate the H2 for use in fuel cells or simply burn.

We'll see. The LH2 lobby seems to be more vocal / well funded.
Anhydrous ammonia is vastly easier to transport and store. And isn't a frakking ultralow cryogenic with all those storage risks, on top of massive explosion limits.

Hydrogen sucks as an aviation fuel. The only reason rocket engineers use it is because there isn't anything better.


Yes, turbofan engines can run on gaseous hydrogen, with properly designed fuel controls and combustor fuel nozzles. Hydrogen burns very quickly and likely would be a superior fuel compared to kerosene, if that were the only consideration. In fact, liquid hydrogen has tremendous capability to drive turbines just with the phase change to gas as it absorbs vaporization heat - see Pratt & Whitney Project 304.

Of course the real problem with hydrogen is storage. Even in a supercooled liquid start, the volume is large. On the RP-1/LOX Saturn V, the LOX tanks are twice the size of the kerosene tanks. But the LH2 fuel tanks on the space shuttle are twice the size of the LOX tanks. You can make an airliner with LH2 fuel, but there may not be enough space for the passengers.

Whether you can store enough H2 in Ammonia form and turn it into a usable form fast and efficient enough to make it worthwhile is the question.
I believe that RE is talking about using exhaust heat to crack a small amount of ammonia into hydrogen and nitrogen gas, then inject that now-hot 3xH2+N2 into the combustion chambers to get the heat necessary to burn ammonia directly.

This leverages their expertise in heat exchangers and is a relatively simple setup. though it does require a custom built engine with both H2 and NH3 fuel injectors, plus some amount of space between the two in order for the H2 to burn and put heat into the NH3 to crack it and then ignite the cracked H2. Probably talking about a 50-100% longer combustion section in the engine, with the cracking heat exchanger wrapped around the exhaust after the turbines.


Looking at ammonia specific gravity and heat content says it takes up less space than LH2, but still will require significantly larger tank volume than kerosene.
It's looking like 2x the volume for ammonia tanks compared to kerosene, based on Joules/Liter. Which isn't bad. Not compared to hydrogen. Does mean 50% more weight of fuel, however. Jet fuel is ~0.8kg/liter, ammonia is ~0.6kg/liter. Equal energy is 0.8kg of jet fuel versus 1.2kg of ammonia.


Yes, icing is always a problem for engines which fly through humid air at freezing temperatures, whether it be on the way up, down or cruise. Remember SABRE is intended as a ground-to-orbit powerplant, so it is going to spend time in that regime at some point. Also, the stratosphere may have a low density, but it can still have a high relative humidity and an awful lot flows through an engine at high speeds. You don't need much ice to break a delicate microtube at those speeds.
This was one of the key features that REL had to demonstrate on a working prototype that they were on top of, before the big investors would come in.
And that test was even more challenging, as they were using the exhaust of a J79. Which means even more water vapor than you'd normally see at Mach 5 and whatever altitude. Lots more. On the order of water vapor being up to about 5%* of the total mass of the air flowing through the cooler.

* - Jet engines normally burn about 25% of the air they ingest, the rest of the airflow is used for cooling. Normal air is 20% oxygen by volume. 1/4 of 20% is 5%. Yes, I assumed away the CO2 production which I know does exist but I don't have good references for, so add some large error bars to that 5%.
 
The 'classic' high-temperature + high-pressure route to ammonia may soon be trumped by any of several mostly-benign processes variously reported by eg PhysOrg.

If even one scales well, ammonia's economics will change remarkably.

FWIW, for one of my SciFi tales ( 'City of Fresno', a WIP), I configured their many big evac pods --Think A380 fuselage-- as not the usual dished ends, but stacked truncated cones, outer 60º, inner 40º and central 'flat'. Docking ports on the 60º provided for a hexagonal toroid, those on the 40º for 'nonagonal' = '9-up'. Axial provides 'linear' assembly. Okay, not 'flat' for joggers, but gently rising and falling like a 'park' path. At least pod longerons are straight, rather than 'curved' like a yacht...
 
The 'classic' high-temperature + high-pressure route to ammonia may soon be trumped by any of several mostly-benign processes variously reported by eg PhysOrg.

If even one scales well, ammonia's economics will change remarkably.

FWIW, for one of my SciFi tales ( 'City of Fresno', a WIP), I configured their many big evac pods --Think A380 fuselage-- as not the usual dished ends, but stacked truncated cones, outer 60º, inner 40º and central 'flat'. Docking ports on the 60º provided for a hexagonal toroid, those on the 40º for 'nonagonal' = '9-up'. Axial provides 'linear' assembly. Okay, not 'flat' for joggers, but gently rising and falling like a 'park' path. At least pod longerons are straight, rather than 'curved' like a yacht...
Curve the inner walls, leave the outer walls flat.
 
Equal energy is 0.8kg of jet fuel versus 1.2kg of ammonia.



And that test was even more challenging, as they were using the exhaust of a J79. Which means even more water vapor than you'd normally see at Mach 5 and whatever altitude. Lots more. On the order of water vapor being up to about 5%* of the total mass of the air flowing through the cooler.
Equal energy is 0.8 kg of jet fuel versus 1.9 kg of ammonia.


The water content of the J79 exhaust had no impact on the precooler testing because during those tests at their TF2 Test Facility in Colorado the exhaust from the precooler was well above 100 oC. The circulating cooling medium through the tubes (helium or whatever) was cooled by boiling water so the exhaust from the precooler was probably in the order of 150 oC.

The difference between the composition of ambient air and the composition of the J79 exhaust only has a small impact on the physical properties of the hot "air" and consequently a small impact on the heat transfer coefficient in the precooler.
 
The water content of the J79 exhaust had no impact on the precooler testing because during those tests at their TF2 Test Facility in Colorado the exhaust from the precooler was well above 100 oC. The circulating cooling medium through the tubes (helium or whatever) was cooled by boiling water so the exhaust from the precooler was probably in the order of 150 oC.

The difference between the composition of ambient air and the composition of the J79 exhaust only has a small impact on the physical properties of the hot "air" and consequently a small impact on the heat transfer coefficient in the precooler.
We've been over this.

They used liquid nitrogen as the heat sink in that test, or else it would not have shown what the engineers needed it to show.
 
There is nothing cryogenic in TF2.
The lowest temperature downstream the J79 is boiling water at 100 oC venting steam to atmosphere.
 
Interesting development.

Reaction Engines has been awarded funding to further a U.K./U.S. collaboration under the UK Space Agency’s International Bilateral Fund. Reaction Engines has chosen Virgin Galactic as the airframe partner for this project. This funding will enable research and development for horizontal launch vehicle concepts utilising air-breathing, hypersonic propulsion technology. The funding programme supports UK ambitions to become a science superpower and build international collaboration to develop innovative technologies.
Reaction Engines has chosen to work with Virgin Galactic on this project. Virgin Galactic’s unique, reusable, suborbital spaceflight system allows them to fly aircraft to the boundary between air and space. After extensive development, Virgin Galactic recently began commercial operations with monthly flights to space for private astronaut and research customers.

Under the planned bilateral activity, the U.K. and U.S. Companies will explore the combination of their capabilities, potential use-cases, and development paths. Neither Virgin Galactic or Reaction Engines are strangers to the benefits of strong U.S. and U.K. collaboration and this opportunity to engage is in step with Reaction’s strategic mission of developing hypersonic and space access solutions, by harnessing the allied capabilities and a shared vision of the future. This joint undertaking, as supported by the UKSA, elevates this mission to the global stage and has the potential to set the course for future collaboration.

 
Whatever comes of it, let's hope its not another tale of technological brilliance squandered because no one is willing to take a chance on new technology. Surely at some point there needs to be another person who believes in the bouncing bomb enough to back it.
 
Any thoughts to combine this tech with pulse detonation?

The latter makes me think vibration---the former... icing.

Maybe they need to be together
 
It seems the company is having cash flow problems.

A British company aiming to pioneer hypersonic flight and which counts Boeing and Rolls Royce Holdings among its backers is scrambling to raise new funding amid a squeeze on cashflow.
 
I'm confused, reading the news piece, what exactly do Reaction produce and how do they actually make money ? ... https://news.sky.com/story/rolls-royce-backed-reaction-engines-scrambles-for-new-funding-13162736
That is the business model; spend 30 years developing no products but convince VCs to give you money in the hope of future products...

It's not really that bad though; they do provide technical services (e.g. engineering design) and some low level prototyping, so there is actually some sales/income.
 
I'm confused, reading the news piece, what exactly do Reaction produce and how do they actually make money ? ... https://news.sky.com/story/rolls-royce-backed-reaction-engines-scrambles-for-new-funding-13162736

Last time I've checked, they had given up Skylon for a USAF TSTO study. Another stream of revenue was the revolutionary Skylon heat exchanger. It was to have all kind of interesting applications, from Formula One to cracking easy-to-store ammonia into high-energy hydrogen fuel for airliners.
 
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I'm confused, reading the news piece, what exactly do Reaction produce and how do they actually make money ? ... https://news.sky.com/story/rolls-royce-backed-reaction-engines-scrambles-for-new-funding-13162736

For decades they have only made money by selling shares.

The occasional radiator or "study" they sell provides only peanuts.

Because early last year the original stakeholders (RR, BAe, UKSA, ESA, Boeing Horizon, ........) did not want to put one more penny into this money-pit, CEO Mark Thomas had to go cap-in-hand to the UAE to beg for money. He got £40 million from them. That allowed him to pay salaries, rent and utilities up till now.
I'm sure the Arabs also got wiser in the mean time so now MT has to find another fool to buy their shares.
This is finally the beginning of the end for this Theranos clone.
 
"...r this Theranos clone."

With respect, Dagger, their filament heat-exchanger and its de-icing system / cycle / whatever are very real, proven to be decades ahead of the industry standard. IIRC, belatedly creeping into niches such as motor racing...

That the Shuttles' tragic demise killed orbital 'wingy thingies' beyond the un-crewed US' X-34 and its Chinese near-clone is sad. Similarly, Concorde's premature, FOD-related grounding plus global financial turmoil plus, yes, 'Zoom' calls, put a long, long halt to supersonic civilian flight and plans for hypersonic...

By analogy, consider how hovercraft have been side-lined beyond niche applications, such as small 'sport' and 'Rescue' (*) craft, and those huge LCACs...

*) Our local Coastguard / 'Fire & Rescue' services often deploy a RIB-sized hovercraft to scoot across local estuaries' notoriously treacherous sand-bars and mud-flats, use light-weight water-jetting equipment to break suction on beset folk...
 
With respect, Dagger, their filament heat-exchanger and its de-icing system / cycle / whatever are very real, proven to be decades ahead of the industry standard. IIRC, belatedly creeping into niches such as motor racing...
All they are capable of is producing a rather simple tubular heat exchanger. Idea probably copied from Suntan. See above.

Others produce similar microtube heat exchangers, also for motor racing radiators. See above.

De-icing system? As I pointed out more than once above they no longer claim on their website that they cool down to -150 oC without freezing up. That was just a lie to get financing. Now they only talk about cooling down to ambient, which is something any heat exchanger manufacturer can do.

Decades ahead of industry standards? If that were true then many would want to license or buy their technology, or buy the whole company, but nobody does.

Neither do we see investors queuing up to buy shares in this "decades ahead" company.
They are broke after burning through the £40 million they got 18 months ago and now again have to beg for money.
 
Concorde successor
pB43k.jpg
 

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