Say it’s roughly twice the cost of an equivalent propeller plane, all down to the highly strung/complex engine and the development work for the supersonic aerodynamics. Or ~50% more than the equivalent MiG-21, if that’s easier.
Another route to this - if they see photos of an aircraft (say a MiG-21) and get an idea of performance but don’t see how. This would leave them assuming it’s some sort of ducted fan powered by a piston engine - which would then lead them to develop this. Someone has a bright idea, and this then develops into a jet engine ~10 years down the line…
Well we are finished with the design but here is the final thought:
It is 150% the cost of the MiG-21 , though I didn’t see how. Machined nickel is different from cast aluminum, I expect it to be 20% less. It’s probably the materials and labor of handling them that raises the cost. Though the MiG-21 is designed to be extremely cheap as it lack a radar and other avionics. If you are saying the aircraft cost twice as much as the equivalent propeller plane, my guess is the P-47 thunderbolt. This supersonic aircraft cost 2 million dollars.
Though considering that at the time they know what a jet engine is (they just cant stand the laughable fuel efficiency), I guess it is viable. The reason i made this was because the design was supposed to be cheaper. I thought axial compressor turbines are significantly more complex than a wankel engine made of cast aluminum.
I’ll hitch you in on the story:
The race we are speaking of lives on a very complex and exceptionally rare system of planets in which there are two orbits very close to each other, each having two planets of there own. Earth’s orbit remains the same, and behind is Verdeckt, Vilous, and Gaia, the latter one is the enemy). Take great notice that earth is on average 15+ years more advanced than they were in the real world. World War two is fought with jets and nukes.
In the case of this airplane, it was located in Vilous, made 1982 earth time. But before that they don’t even know what firearms are. Well in this story , Apollo wasn’t going to the moon, it was making second and even third America should the United States lose to The Soviet Union, Verdeckt and Vilous based nation were the Calvary that will wipe out what wasn’t wiped out. They needed a vehicle to do it called the Sea Dragon, which can effectively put a one million pound spaceplane into orbit for a very low cost of 50 USD per pound, and is very reusable. In 1965, Apollo commissioned a series of rovers on a scaled down rocket, 5 Sea dragon rockets (4 are spares), 20 spaceplanes containing men, weapons, a farm, and medical equipment, this counts as a single fleet and separate project. Apollo 1 is a single fleet to Verdeckt. Apollo 2 is a single fleet to Vilous. Did I also mention the probe is a unarmed robotic extremely long range M113 APC?
The first phase in Apollo 2 (like Apollo 1) is just the rocket and probe, the result are different though. It resulted in a bunch of savages running from a M113 APC. But they had swords and buckboards and stuff. Also the only Vilous inhabitant to intentionally run towards it invented the suspension for carriages, a torsion bar. That was an extremely unlikely result to meet a civilization that advanced. He just wanted to see the damn thing.
The second phase was production (which was quick), and by 1967, there are over a thousand volunteers with different roles, none of which were expected to come back to earth and they knew it. The purpose of the medical facilities was vaccination. They went over to Vilous and took there germs and language, and in exchange interested them in a new subject: the Bessemer process, successfully accepted by norther tribes (did I mention savages). Success resulted in the production line and car by 1972. then the airplane by 1975. by 1979 the four stroke engine. By 1982 the airplane I was talking about, and they broke the sound barrier.
To the humans understandings, they cannot use jet engines because the steel they produced did not withstand temperatures and was not efficient enough to save the limited oil. The needed material came from a separate territory called Tonruz which was owned by a different species and for political reasons, it’s not possible to trade. It turns out there is a cold war going on in Vilous. The humans used interesting ingenuity to get them to drive cars while meeting demands which are comparatively strict. So they made the airplanes use a wankel engine, but why?
While it was inefficient, humans told them to make it out of the strongest wood- steel composites, the Sound barrier is very much real, and also to stay in it for only a certain time. The airplane was put into production after a strange modification to make it run on “something else”, and as a result is a very important aircraft in 1985. BUT if the aircraft cost 50% more than a mig21, why not make a mig 21. Easy, there is a resource problem on metals between the tribes and tribes in Tonruz. only steel and wood is viable. Aluminum is also kind of an issue. The only issue is the fuel. The thing about Vilous is that all the races are almost feral, and the planet is a desert with little oil reserves. The thing is that the resources used (and i did not mention this earlier) is planted wood as a renewable resource. Even by 1982 industry does exist, but is so limited. So the races are still savages all along. As a result Apollo 2’s result is near questionable. Unlike Apollo 1 which does not have any resource problem, and met countries on verdeckt which are at a state of Tranquility.
For the last words: this is highly off topic, as i am now explaining this planes history which is highly fictitious. I recommend that you do not search up Vilous or the races that live in it. Those races and above location are not my responsibility or idea. The original race is made by a person in Japan, the work is left unfinished. But you can go hear: http://verdeckt.wikia.com/wiki/Verdeckt_Wiki
Thing is, the turbines in a modern jet engine are only expensive because they’re operating at extremely high temperatures to get high efficiency. If you’re willing to accept lower efficiencies, you can use simple cast nickel turbine blades – not quite cheap as chips, but getting there. Furthermore, the power loadings on turbine blades are huge compared to compressors – off the top of my head, a single HP turbine blade the size of your thumb will produce about 100 horsepower and weigh a few tens of grams. This means they can get seriously expensive per blade before any other form of engine gets cost-competitive.
The problem here is that the speeds you’re requiring force you to go for a compressor + Convergent-Divergent nozzle. That’s the front half and most of the weight of a jet engine, with the rest being sheet metal work (jetpipe + combustors) and the turbine
Rough guess – all the electronics will be the same price, the airframe will be significantly more expensive due to what is essentially a piston + jet propulsion system.
The turbines are pretty simple provided you keep the temperatures down – it’s only when you plan to operate in gas significantly above the melting point of the metal (as is routine nowadays) that it becomes a problem. With the early Whittle-type units they just turned the temperature down until it gave an acceptable turbine blade life (IIRC ~1000 hours) and replaced the blades regularly.
Seems entirely reasonable. That being the case, this is about the only way you could exceed the speed of sound. The Germans did try using what were IIRC mild steel turbine blades with active cooling at the end of WW2 (nickel being unobtainable) and they did get a working engine. Problem was it had a life expectancy of about 10 hours – at the time they didn’t care as this was significantly longer than the life expectancy of their pilots, but unless you’re in the process of fighting a war you’ve already lost that isn’t a good way to go. You could possibly improve it with very modern technology to match the early Whittle-type engines, but that’s about your limit – it was a pretty awful design!
And that wooden airplane part- that’s hard to explain, especially how they managed to get it to supersonic speeds. But I think I know why but that was not the production model.
So what are the main problems of this aircraft right now.
It needs an engine that last at least 250 hours. It’s cooling of course.
we have the airframe down
we have the engine power down since the beginning…
then I notice I did something terribly wrong. If the Mighty Earbanger/ Thunderscreech has a design speed of around transonic with a massive 4000 horsepower engine. Why can’t I just use the starting engine, 12 liter wankel with 6000 horsepower. What I am speaking of is sizes. The Merlin sueprblock of similar size to the engine is not even close to half the weight of the Allison T40, let alone half the size. I have room for 2 more of these, and I can still go mach 1.5 with a single engine.
I think.
Anyhow, you mentioned earlier that increasing the weight of a vehicle or engine by 1% to to increase efficiency by 1% is a net loss. What is it a net loss of? speed, efficiency range?
because I am having a thought of making the engine a compound engine.
What do you think I could do to increase fuel efficiency now.
Increasing total vehicle weight by 1% will increase fuel burn by 1% (the ratio of lift:drag is a function of the aerodynamics - so modifying the engine won’t affect this). Drag will also be increased, slightly reducing top speed (although probably by an insignificant amount - drag can increase incredibly quickly with speed when you hit the design limits).
If you increase engine efficiency by 1% at the same time, the fuel burn per unit distance travelled is the same.
HOWEVER the maximum takeoff weight is unchanged. If the empty weight of the aircraft is increased by 1%, that same weight increase must be removed from the amount of fuel (or payload) it can lift off the runway.
Hence, you will lose ultimate range (can lift less fuel off the runway), payload (can lift less weight off the runway) and possibly a tiny bit of speed depending on the exact design - this can easily be handwaved away.
what this means is that my increase in efficiency by percentage has to be higher than the increase of weight by percentage. do you have a suggestion for modification, this thing has two massive turbochargers right now.
and if I have the 12 liter wankel in a Mig-21 -ish fighter and that’s it, how does it compare to the mig 21, right now without your guessed modification?
in terms of speed and efficiency. I I could remember correctly it has half the efficiency, but it can achieve the same speed. How do we improve this? more turbos?
I am literally just starting to see how this is going.
In terms of short-term power, water or methanol injection between the turbocharger exhaust and the engine inlet. This cools the gas, which then contracts and then enables you to cram more into the same size of combustion chamber and hence burn more fuel for more power. This is the same thing an intercooler does, but I don’t think you’re going to have space or weight for one - this is a much lighter way of doing it, but the consumption of water/methanol is high.
Another option is hybrid jet/rocket power. This can be as simple as a couple of large fireworks on underwing pods. This is mostly of value for takeoff, which is when the aircraft is at it’s heaviest and needs the power most, hence military jets normally taking off using reheat (afterburner). If fired at high altitude it gives you a LOT of extra potential height, and if you’re higher you can also go faster. Good altitude/speed diagram giving you an idea of what the thrust gives you here: http://www.spaceuk.org/sr53/sr53%20research.htm
Finally, you could look at air-launching from a mother aircraft (like the B-52 used to launch the US X-planes). That saves a hell of a lot of weight in climbing to altitude, allows you to optimise for high-speed flight, and gives you a lot more effective endurance - the aircraft can be airbourne and ready to launch, as if on a standing patrol, and launched very fast when needed.
This is where I start to disagree with using a turbo jet or advanced air compression, or just accepting poor performance.
Throughout this entire discussion, I have been pretty confused, so I end up with a new idea every now and then. This is not about cooling.
Well, something just popped up in my mind. I will add an airplane: the XF-84H Thunderscreech, I like to call it the Witch (you will get it if you are in your 20’s and play video games).
By the time it’s engine was made, it had 5850 horsepower, and weighed in at over 2000 pounds.
The airplane itself I am speaking of weighs in at 18000 pounds
The airplane we are speaking of weighs the same.
The Wankel engine that it uses has twice that power density as that engine because it is a modern 12 liter with massive twin turbos, and the same power… on cast iron. Half the weight, same power, but it is a crap load less efficient. If I made it a tandem with another wankel (forming a compound engine), the engine would nearly double in weight, but power would be increased, and because of the shear power left in the exhaust I would get a great increase in efficiency, and it would still suck compared to the turbine. However, it will be more reliable and cheaper because at the time the most advanced available engine material looked like this:
This is unsuitable for a turbojet because they are flimsy with this material. Wankel engines are… chunky (it may be more important than you think).
To get to the point: you suggest using exhaust gas to drive more air into the compressor. If I do that, there will be more heat in the engine and the problems arise in cooling the engine. I use a standard cooling system in the simple Tandem Compound Wankel because I do not increase the efficiency of the first engine. Instead, I used the unburned fuel and hot exhaust to run a second non combustion engine. At the time of the country making this airplane time, this is better than a complex cooling system and an efficient first engine. This is also far different than the Napier Nomad you mentioned earlier because there is not extra power shaft, or gear box, it’s just another set of somewhat wider expansion chambers. It’s all in one engine block, in fact.
And that is only half the story. The X 84 came from a time where the most powerful engines had the fuel economy of a Bugatti Veyron, but had roughly twice the horsepower of a modern day 2007 Fiat 500. Yet the P-51 and Spitfire were impressive sights, and they went far enough. When we are talking about my idea I feel like that it will go 300 miles an hour and fly all the way to the next McDonalds. In other words, my side of the discussion is pessimistic but confusing.
Now that I have explained the concept, The goal is to have a range of 600 miles with no external tanks, and a top speed of mach 1.5.
I am very confident in this concept, but right now, you’re the king.
Errr… no, I’m not suggesting that at all. I’m suggesting intercooling the existing turbochargers that feed the Wankel engine using some sort of evaporative cooling (Water or Methanol). This reduces both charge temperature and work required by the compressor section of the turbocharger - in turn allowing you to fit either a bigger turbocharger for more boost or have higher exhaust energy for more thrust. The cost is a bit of weight and efficiency.
Intercooling the compressor you’re using to generate the supersonic thrusting air is a BAD thing - it’ll significantly cut down your thrust.
Sorry, my mistake, I was thinking about cooling the turbochargers not the rotor. I used the wrong word, referring to the turbocharger as the spool of compressor blades in a jet engine.
what about the engine design.
Oh yes, and thank you for all the information you gave out and sticking in the thread, I am going to use them in the concept.
As a matter of interest, I’d reckon you should be checking out the Flight Magazine Archives which show Napier aero-engines, they were right up there with the last hi-po big inch aircraft reciprocating mills…
Check out the Sabre, a 36 litre H-24 sleeve valve fighter mill type-tested giving 3000+ hp @ 4,000rpm at world beatingly competitive power-per-cc & hp/kg ratios.
Napier also developed the Nomad, a very efficient [& it’s still more efficient on a SFC basis than today’s gas-turbines] 2-stroke Diesel aicraft engine…
Napier also did the Deltic [also a 2-stroke Diesel] for high speed heavy vehicles - express locos & fast patrol boats, so good that even the USN used them in Vietnam…
Cube-a-what-now?
& has IT passed a 100hour type-test at 3,000hp?-If not, See Napier Sabre Mk VII…
The last 2-stroke G.P. race motorcycles [sadly, now banned from competition…] were reliably putting out 55hp from each 125cc [non-turbo] cylinder…440hp/Ltr.
Cubewano- listed because they’re typical of modern rotary engines intended for UAVs, and aren’t too highly stressed. It’ll burn just about any fuel, has no boost and about 2 moving parts. Something like Liquid Piston would also be a possibility - that’s more like what we’d end up with if we tried to design an internal combustion engine from scratch, rather than based on the first successful technology out there (steam engines).
Given the particular context of this thread (a non-earth based civilisation with only propeller driven aircraft) there is no reason to assume that they will have started out with piston engines. No jet engines is a given, and since a turbocharger is almost identical to a Jet engine in principle (and a supercharger is close behind) that implies little or no boost. Rotary engines make very high power to weight ratios easier, and are recognisably different from Earth technology which would be important in a book.
If I was going for extreme piston engines, I’d have either suggested a Rolls-Royce Crecy (bench tests gave potential for 5,000 BHP from 860kg before it was cancelled!) or a Formula 1 engine (about 6kW/kg)
Forget about F1 engines, they are ludicrously complex & expensive for what they make power-wise, in fact the RR Crecy would be a good basis for up-dating [with 21st century metallurgy/computer engine management],being a 2-stroke.
4-strokes are inherently ‘lazy’ & have to be revved very high [F1] or pressure boosted [ by pumps &/or chemically] to make power, but then have mass/complexity/cost issues.
Consider the chainsaw…
A chainsaw has to have a high power to weight ratio, be manually heft-able,capable of operating at various attitudes/angles, & cost effective…
Honda is an ideologically driven pro-4-stroke company, but even they haven`t been able to make a viable 4-stroke chainsaw, since a low mass,compact dry-sump,turbo 4-stroke is very difficult to make on a cost effective basis to compete with the current 2-strokes.
The Wankel [technically not a rotary -see Bentley BR 1] is interesting, & running on a 2-cycle does offer good power density, but - [ as can a high performance 2-stroke using a pulse-tuned exhaust system] may be seen as a mechanical 1/2-way stage between reciprocating mills & true turbines…
Alas, yes…Toyo Kogyo [Mazda] recently dropped their Wankel engines from production - after doing their best with them for decades…
SFC efficiency & max power density are hard to get in the same machine, the most fuel efficient are the [very] big 2-stroke ship Diesels…
… but the Napier Nomad [also 2T Diesel]-is likely still the most SFC efficient mill to fly…
What is the best Sterling cycle mill performance [in metal, -not in theory] achieved, power to weight-wise?
I’m well aware that rotating radial engines are (realistically were - nobody has made an engine like that for almost a century, for VERY good reasons) known as rotary engines. However, Wankel refers to a specific type of engine, and the derived versions of it running a slightly different cycle are known as Rotary engines nowadays. Liquid Piston isn’t a Wankel cycle but is mechanically similar, and is known as a rotary engine (in much the same way as piston engines typically follow the Otto, Diesel or Rankine cycles).
Take a look at the Liquid Piston link I put in there - the problems aren’t inherent to Rotary engines but to the particular implementation. Conceptually you can get pretty close to the Carnot limit, although how close you end up in practice is as yet unclear…
