This is truely impressive
It just goes to show that the UK still has the engineering know-how to take on the world. Now if only we had the cash ...
Brit rocket outfit Reaction Engines has demonstrated its precooler chilling air in Mach 5 conditions in less than 1/20th of a second. In context, Mach 5 is more than twice as fast as the Concorde's cruising speed and 50 per cent up on the SR-71 Blackbird. The HTX test programme had previously run the precooler at temperatures …
Seems that there is a reader who knows what the relationship between cooling air and rocket engines is then. IMO the article could do with a brief overview of how the engine works or why the super rapid cooling is a benefit. Perhaps then we'd be able to make more jokes....
This engine doesn't separate the oxygen off, it just cools it a massive amount. That's extremely useful because it means they can compress it extra hard in the engine core, which makes the engine much more efficient. The waste heat ends up in ramjet-like burners.
Turns out that liquifying and separating off the oxygen is a net loss when they ran the numbers, so they don't do that.
Er, that's not quite it I think.
You need to chill the air because the compression heating in the inlet caused by the aircraft ramming air into the engine at Mach 5 raises the air temperature to 1000°C before its reached the compressor blades. There's no compressor that would survive such a temperature, especially as the compressor itself heats the air even more. If the air at the front of the compressor is starting off at 1000°C, the air getting to the combustor is going to start melting things no matter what it's made from.
The SR-71 was limited to Mach 3.0 by the inlet air temperature reaching 400°C.
Also, compressor air is used for cooling hot section components, such as turbine blades, etc, something that can't be done if the air is already at 1000°C.
The reason to go to all this bother instead of just switching from jet mode to rocket mode earlier is that you'd have to carry a lot more liquid O2. By being able to ingest air beyond Mach 5, you can save a lot of weight.
I don't know if this is a factor but even if you could compress air at an input temperature of 1000C without destroying the engine then the result would be air significantly hotter than 1000C. The thermodynamcis just doesn't work if the temperature is too high. At around 3000C then around half of water molecules disassociate into hydrogen and oxygen and this temperature could easily be reached if significant compression of the air was being performed. This is a more fundamental limit than the ability of the engine to withstand temperatures etc.
Does it? After reading up, I don't see any mention on splitting air into nitrogen and oxygen. I don't see how -150C should help with that anyway. At least as far as the Wikipedia article suggests the precooler is there to prevent the engine from melting or blowing up due to the high pressure without the need for very heavy parts. It seems that during air-breathing mode air is used directly in the combustion. Feel free to correct me if I am mistaken.
Hugely impressive - but hugely expensive. The only way that we can deliver a marvellous and world beating technology like this (or fusion, or defeating global warming, or space stations, or Mars colonisation…) is by working together.
Which is a long winded way of inviting a downvote nuking by pointing out that our continued obsession with national suicide (or Brexit, as it is commonly known) is a very good way of ensuring that projects like this will either never be delivered, or at least that they won’t be delivered by Britain.
"Which is a long winded way of inviting a downvote nuking"
And quite rightly too.
This has nothing to do with Brexit or the EU.
These guys have been working on this since 1989, so prior to the EU coming into existence.
And while the majority view here appears to be that it is awesome engineering (a view I share), no one has mentioned that these guys have also spent 30 years working hard to market the idea and raise funds, persuading all sorts of people that they are not just a bunch of British loonies, but have a credible idea which they can deliver.
The project is now funded because the idea is good and the team doing it are capable of delivering. Bugger all to do with the EU or BREXIT.
It may be a surprise to some, but the UK (as a nation) and more importantly, individual British companies and people will continue to work with people/companies from other nations after BREXIT (many of which countries won't even be in the EU).
So can we please stop needlessly prattling on about the EU, when we have such a bloody brilliant piece of engineering to admire?
I used to think this was amazing engineering, and indeed it is. This stuff is Really Difficult.
But I’m less certain than I used to be, that this is the right technical way forward for launchers.
If we look at what Space-X are doing - Elon Musk may be a first-class twat, but he teaches us a lot of important lessons.
1) Fuel efficiency and delta-v aren’t the most important thing. Fuel is 2% of launch cost.
Fuel mass is only important, in that it scales the cost of dry mass of the tanks, and the lifting power of main engine.
Dumb dry mass is cheap, smart dry mass is expensive.
2) SSTO is cool, but not ultimately critical. Re-usability of top stages is most vital. Cost drives everything, and simpler turns out to be cheaper than smaller.
3) Even weight efficiency of the structure isn’t critical. Build Cost is critical. The latest for BFR is using riveted steel like Flash Gordon movies, rather than aluminium and carbon fibre for the main tanks. It’s just cheaper, faster and easier to build, and the extra fuel to lift it still isn’t the dominant factor.
Fair points; what defines a successful space launch system will likely be the cost of pound (or kilo, or Approved Register Unit of Measurement) to orbit, however, the two technologies may co-exist: the Space-X approach may prove to be the commercial winner for routine satellite launches, but Reaction Engines offers potential long-distance sub-orbital (very fast) passenger/cargo travel.
I had to look up melting temperatures of metals just because..
1,000°C to a Useable temp in such a small period that will not melt the engine wow just wow.
Please can I have a Firefly ASAP, preferably with Kaylee in charge of engineering.
Because there are some very smart people about, it's not just about melting points of metals.
Those clever people over at the Rolls-Royce Engine Division run blades in their Trent engines in temps above the nominal melting points of the materials, by a combination of fins/cooling holes in the blades themselves. The alloys they use are apparently a closely-held secret as well.
QUote:The alloys they use are apparently a closely-held secret as well.
They're based on materials like Inconel which has a high nickel/chromium content, which is grown as a single crystal of the material, then ground into shape, with the holes cut in by electrical discharge machining.
And after some experience with such materials, all I can say is "They're right bastards to machine"
Hmm, back in ancient times when I worked there (I designed a doohickey to help in the manufacturing process) the blades were investment cast, cooled in such away as to create a single crystal and then the root profile was cleaned up by broaching. I’d be surprised if bulk grinding is used instead of that basic process.
"And after some experience with such materials, all I can say is "They're right bastards to machine"
Amen to that, not sure what would be worse, big old turbine blades or the 3mm diameter, hollow, tapered to a razor edge metal to glass seals I used to have to machine to 5 micron tolerances in a former life.
Those clever people over at the Rolls-Royce Engine Division run blades in their Trent engines in temps above the nominal melting points of the materials, by a combination of fins/cooling holes in the blades themselves.
Yes, but those blades are cooled with bleed air taken off from the back end of the compressor somewhere. However if the air entering the compressor is already at 1000°C then the air at the back end will be even hotter due to yet more compressive heating. So the air supplied to the turbine blades for cooling isn't actually going to cool anything. It's going to melt things all by itself. It's also going to melt the back end of the compressor, the combustor, etc.
Cooling the air in the inlet sorts out a whole load of problems.
Actually, in current gas turbines, along with inconel alloys, it's a combination of coating the early stages of the power turbine blades and stators with Ceramic Matrix Coating ( the composition of which is rather IP protected) and cooling air from a suitable interstage location in the compressor section/turbine ( depends on your design)
The air is extracted at a pressure and temperature low enough to provide the internal and necessary surface cooling by excluding the extremely hot combustion gases from direct contact with the components. For any direct surface contact the CMC provides final protection. The combustion gases have expanded enough prior to encountering the first stage that the interstage cooling air pressure is high enough to do the job.
Subsequent interstage expansion of the combustion gases and therefore cooling, results in the last stages of the power turbine not requiring assisted cooling.
The single crystal aspect increases the mechanical strength of the blade so that resists flying apart due to impact and / or centrifugal forces. It adds little to the material's thermal performance.
Because you can use the air coming into the engine for blade cooling. IIRC ambient temperature at airliner cruise height is about -20 to -40c, so even after compression it's pretty cold.
Now what happens when the inlet air is already 1000c?
The J58 on the SR71 used uncooled blades but AIUI cooled blades are SOP nowadays.
Obviously alloys have improved in about the 70 years since its design so you could run hotter.
Or you can put the pre cooler in front and (potentially) get away with some of those blades being Aluminium.
The idea with Sabre is it starts off as a jet-esque engine and gets through most of the atmosphere then- to get really fast for orbit- shuts off the inlet and becomes a rocket, burning on-board stores of fuel and oxygen. The same engine is both a jet-ish-thing and a rocket.
No piggy back, just an awesome technical achievement when it works.
It's better than that. Imagine an SR-71 type aircraft that can go from the ground, up to Mach 17 in orbit and back. That's basically what it's intended to do.
The precooler is needed only to make the jet mode operable to higher speeds / altitude, getting the aircraft closer to space before it has to switch to rocket mode and start using onboard O2 instead of atmosphere for combustion. By switching to rocket mode higher up, where there's a lot less drag, you get more delta V out of the amount of O2 carried.
In principal the pre-cooler is needed only between about Mach 3 and whenever they switch to rocket mode. Jets working up to Mach 3 are achievable without pre-cooling, using sane materials.
No, the idea is straight to orbit. I attended a lecture given by Alan Bond who basically invented it. They plan to run the engine as a jet engine up to ~Mach 5.5/~75kft, and then switch it to a rocket mode. The jet engine is super-duper efficient and lightweight, and together with the high speed means they have enough propellant left to reach orbit.
Another old plan is quick flights half way around the world. The piggy-back two stage to orbit is a new-ish plan. It makes sense as you only need the first two thirds of the jet/ramjet/rocket engine to work and you get a bigger payload. Reduced development time at the cost of some re-usability. At their rate of funding it makes a lot of sense.
The idea is you can burn the fuel for the first 10km or so using air as the oxidiser, and only when it gets too thin do you need to use LOX (liquid O2) or high-test peroxide, etc, for getting in to your wanted orbit.
While 10km or so might not sound like much for the 100km or more "orbit" hight, it represents a lot of the volume of fuel burned and so the saving in not having to carry your oxidiser on-board is very significant. See also:
"at Mach 5, they travel 86 meters in 1/20th of a second"
Quite. There's something not making sense here. Is the engine 86 metres long? Is there a convoluted path? Is the air slowed to much less than Mach 5? Or does this mean there's some way to go before it can be cooled quickly enough to work in an engine of practical size?
As it's a jet engine, the air must be subsonic to go through the compressor. Jet engines with supersonic airspeeds are SCRAMJETs and is still a very experimental technology.
So yes, it's getting slowed down a lot however this is relatively well understood.
I assume the impressive cooling is required for engine efficiency, including not melting immediately
Yes and no.
SABRE is designed to switch to full closed cycle rocket mode a bit over M5. It was designed to go all the way to orbit. No 2nd stage needed. No 2nd engine type needed.
Will REL's backers let it be fitted to a vehicle that can do so.
Probably not. One of the big benefits of SSTO is down mass, which you loose if you make the US expendable.
There are lots of ways to go up to orbit. Very few to come down again. TSTO with expendable US is one of those stupid, bean counter type "optimizations" that look good in spreadsheets but shoot you in the foot operationally.
So far as I can see, there's now no unproven technology in the HOTOL / SKYLON concept. Jet engines work, rockets work, the precooler now works, supersonic aerodynamics are understood, space flight control is understood, heat shields for reentry are a done deal. It's all there.
Ah, hang on; this being a British thing there's the significant question of whether a decent cup of tea can be brewed and served in a porcelain cup and saucer at all points in the flight profile of such a vehicle, complete with a digestive biscuit. (Yes, I'm British. These things are important). Pretty sure they couldn't on the Space Shuttle. What a waste of NASA talent.
So it might actually get built. Now that'd be quite a thing, and rather more showy-offy than anything anyone else is doing. Can't wait!
In extreme circumstances, such as during a rocket launch, it is acceptable to serve tea from a Thermos (Tartan pattern obligatory)
However the reduced air pressure on board the ISS does preclude the making off a proper cup of tea.
It was delays in the development of the high pressure tea kettle which did for the 1950 British moon landing
Like the Centurion tank all British AFVs ever
Not every AFV ever. IIRC tank crews were in the habit of getting out of their tanks to make tea when the opportunity arose and, what with there being a war on, got killed to death by the enemy while doing so. That led to brew kit being installed in tanks (and all other AFV) as standard, so that tea could be had from within the confines of an armoured metal box.
"However the reduced air pressure on board the ISS does preclude the making off a proper cup of tea."
Only if you make it in an open vessel. You can use a pressure cooker to get the correct boiling temperature, obviously with the release valve calibrated to 100 degrees so you don't end up with stew.
Rich tea is the only acceptable accompaniment to tea
Or, for the truely adventurous amongst us, dark-chocolate-coated stem ginger cookies.
AND NO DUNKING. People who dunk buscuits in tea should be exiled away to the outer darkness of uncivilised parts - somewhere like America.
Haven't you heard of the space rated vacuum insulated double skinned porcelain Mk 1 tea cup? Essential tableware in this household I can tell you.
Aside from that, 1) porcelain ideal for a quick cuppa, for light weight maneouvring, no hanging about; 2) half inch thick stoneware pint pot, reinforced handle, preheated in the furnace of course, ideal for a serious cuppa for serious work. With a digestive.
Just yesterday I was reading that Neil Woodford - until about 2 months ago the "most successful fund manager in Britain" - had invested part of his doomed fund into a company called Industrial Heat, which is a front end for Andrea Rossi and his e-Cat "cold fusion" scam. Surprised no-one had picked up on this until now (source)
The contrast between one firm doing smart things with little money and another quite literally investing milliions into perpetual motion machines tells you everything you need to know about modern Britain.
Every Star Wars director has solved this problem so I am at a loss to understand why this is even a question.
Fighters take off from the planetary surface, transition into space where they dog fight and do other retro stuff before leaping into hyperspace so they are home in time for tea.
This is true of Star Trek shuttles as well.
And there's not a teapot (or lavvy) to be seen. (Although there might be some we haven't been shown on the shuttles given they are much bigger than X fighters.) Simples evidently.
And there's not a teapot (or lavvy) to be seen.
B5 S1 has a scene with Garibaldi and Sinclair in a room talking. It's only till Sinclair moves to a wash basin that you realise what he was supposedly doing in the first part of the scene (could be early S2 with Garibaldi/Sheridan but certain it's S1). Possibly in the lead-up to the B4 double-eps.
Only SciFi I've seen that in. ST's shuttles don't even remotely have space for a lav (nor sleeping quarters, even though sometimes they do multi-day trips in them).
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