Could the Luftwaffe survive against Allied attacks if the USSR had been defeated?

[Soren]

Well according to your qoute KK the problem was solved with the reduction in rpm from 9,000 to 8,700 rpm. So the resonance problem was solved before the Me-262 entered full service, as the Me-262's in service weren't allowed to run at over 8,700 rpm producing 8.8 kN of thrust.

Now according to my research some problems with engine service life remained because of substitute metals used in the hot section and because of the initial throttle system allowing large amounts of fuel to be dumped into the engine at once, causing a flameout. This problem was later solved, preventing the risk of flameouts and allowing more aggressive throttle control. However the problems with the metal softening in the hot section still remained as the needed metals weren't available, and IIRC full throttle flight was only allowed for 30min at a time.

The Jumo 004D series had a new throttle control system which like that on the late B series prevented flameouts and allowed aggressive throttle control. However the D series was also allowed to run at higher rpm's, suggesting a new turbine blade design amongst other things. The increase in rpm's was considerable at some 1,300 rpm, and the increase in power was noticable as-well at 1.5 kN. And all this for no increase in weight.

Performance with the D series was pretty mindblowing at 920 km/h at SL and 945 km/h at 5.5km.

[kool kitty89]

I think it was more due to thermal creep than softening. Continued expansion and contraction of the metals used in the hot section caused certain components (namely the turbine blades) to become distorted over time. The use of nickel alloys can mean hot section components that are virtually immune to thermal creep, as the addition of nickel in certain combinations greatly reduced the expansion with heat. (Nimonic alloys used in the british engines, in addition to being resistant to high temperatures and oxidation, were particularly good in this respect as I recall)


The blade softening problem occured in a similar manner to the flame-out behavior: too much fuel was dumped in at once and (rather than resulting in a flame-out) the ai-fuel mix was made richer (ie closer to stoichiomentric in this case), causing higher temperatures. At the same time there would be insufficient cooling air while this is occuring, worsening the problem. This results in temporarily overheating the hot section and softening/warping of the turbine. (depending on the severity of the event and the condition of the engine this may cause an immediate failure of the turbine or possibly a ruture in the combustion chamber, or simply result in more minor damage that will shorten engine life and possibly fail lter on)

[BIG BIRD]

I saw A show on the history chanel that said the germans could start production of 1,000 Heinkal he 162 volksjagers a month, some variants were estimated to be more than a mach for a mig 15 or f-86.

[kool kitty89]

Those would be the Swept wing variants with the HeS 011 engine. (He 162C)

There was also the He 162D with foreward swept wings.

[delcyros]

The reliability issue of the Jumo-004B was due to the fuel regulation system, which (unlike the BMW-003) was not regulating the fuel flow in correspondence to airflow but to engine rpm. Easy to burn out the turbine blades when accelerating from idle to ca. 6.000rpm. That´s why 100 hour benchtests are not very reflective, they do undergo the critical throttle setting only once and then remain fro the duration of the benchtest at high rpms. In service conditions, one has to accelerate from time to time (every take off, f.e.) and the intervals are probably related to less than one hour. Hence the avg. service lifetime of the turbine section of the BMW-003 was 200 hours instead of 25 for the Jumo-004 while both engines passed multiple benchtests in well in excess of 100 hours. Both engines used identic alloys. Check my post #23 in this thread for more details:

http://www.ww2aircraft.net/forum/avi...ne-1745-2.html (Heinkel He-162 engine.)

[red admiral]

A few bits to add; changing materials isn't a magic fix. Prolonged heating of a material under load will eventually result in failure. This is called creep and its probably the most boring failure mechanism possible. The blade will grow in length until it either snags the side panel or breaks from excessive stress. Adopting a nickel superalloy reduces the rate of creep it doesn't stop it so the failures will still happen, only after greater running periods. However, if you have good maintenance procedures you can reduce the failure rate by replacing the blades (or the engine more likely in this case) before this becomes a problem. This stands whether you have steel, nickel or ceramic blades. More regular engine changes for the 004 would have mostly solved this problem.

*Note, modern engines have FADEC that continously measure the clearance between the blades on the casing and move the casing outwards as the turbine blade grows.

For reliability of the engine in service use combustion is a big problem and the limiting factor in the early British designs before being mostly solved in 1941/42 (though a better burner was put into service on the Nene and subsequent designs). You're trying to burn a lot of fuel in a combined space, short time in a howling gale. Excessively quick throttle movements are going to have bad results. The US ran into lots of problems in the 50s with the adoption of on/off afterburners.

My comments with regards to reliability in service are more to do with the other end - the compressor. Rapid throttle changes (or even differences in AoA) could cause problems because of the poor surge characteristics. Rpm increases so more air has to be compressed and against a higher pressure gradient so at times it will break down and the air flow reverse direction and start coming out of the front. Its a lot more rapid and violent than that, with lots of vibration and the possibility of blades breaking. The low pressure ratio of the 004 (compared to the immediate postwar Avon) reduces the problem but fuel consumption is poor as a result.

Performance with the D series was pretty mindblowing at 920 km/h at SL and 945 km/h at 5.5km.

Pretty similar to the Meteor F.4 which is more or less constant 590mph up to 15000ft whereupon its limited to M0.82

[kool kitty89]

The 003, 004, and 006/HeS-30 (as well as Heinkel's centrifugal-flow engines) all had fairly low pressure ratios of around 3.0-3.2:1 (even lower on the early Centrifugal models).

The 004A/B/D/E (and iirc the 003A/E) used the relatively simple impulse blading in the compressors (with ~80% of compression taking place at the rotor blades and most of the stators acting as guide vanes only), which allowed the blades to be made of stamped sheetmetal, cheap and efficient method of construction, but a lower mechanical efficiency and greater weight. (albeit the 003 was a little more efficient than the 004's compressor)

The HeS-30/006 (as well as some versions of the 003 being devloped with much greater performance, significatly higher pressure ratio, and greatly reduced SFC; namely the 900 kp 003C and 1,200 kp 003D) used reaction blading (with compression acheived ~50/50 at the rotors and stators) with much greater efficiency and compression per stage, achiving a similar pressure ratio to the 003 and 004 but in only 5 compressor stages. With much lower specific fuel consumption, size, and weight. The downside is that the blades had to be machined and required the use of thrust bearings.

Early jet engines

I believe Delcyros has brought a lot of this up before as well.

[kool kitty89]

Early jet engines

I found the post I was looking for on that forum regarding the vibration and TBO. (it seems I overlooked it a while ago)


It also gives a good summary of the advantages and disadvantages of the Britich vs German engines. (ie the 004 the 004 had a much smaller frontal area at the expense of considerable weight gain)

[Venganza]

Originally Posted by namvet68

No...with Japan being knock out all the might of the US military would be turn on Germany. Now the Luftwaffe would have to face the high flying B-29's. All American forces would be able to focus on bring Germany to her knees and lets not forget the possible of having the A-bomb dropped on her also. [Emphasis added.] Turman would not be a fraid to do it.

American flight schools can turn out more pilots than Germany could and American factories can turn out more everything than Germany could.

England than could turn to all of her empire to send all the troops from the Asia to Europe.

I think the part about the A-bomb is the crucial part and it has nothing to do about whether of not we had knocked the Japanese out of the war. If the war had gone on into 1945, it wouldn't have mattered how many wonder weapons the Nazis had. If the bomber streams started getting hammered by these jets and the Allies started to lose their air superiority, they would have just started dropping A-bombs on the Germans and the party would have been over. It might have been a little more difficult to drop atomic bombs on people who looked like us (the Germans as opposed to the Japanese) but I'm sure we would have gotten over those qualms. If the Nazis had also had the bomb, then that would have changed everything, but even in real life, with the impetus of getting hammered by both sides, they didn't have the bomb by 1945, and if they had defeated the Soviet Union, I think their atomic research would have been put even more on the backburner, so no Nazi A-bomb by 1945. The Allies win.

[kool kitty89]

In a horific/terror factor kind of way, yes, but the allies (the US) had only one more bomb nearing readiness after Fat Man, after that it would have been several months before another could be completed. (so a total of 1 Uranium bomb and 2 Plutonium bombs detonated durring the war, with a third in readiness)

[HoHun]

Hi Venganza,

>If the Nazis had also had the bomb, then that would have changed everything, but even in real life, with the impetus of getting hammered by both sides, they didn't have the bomb by 1945

Hm, we know that today, but how much did the Allies know in 1945? I suppose the consideration that Germans might possibly have an atomic bomb could have dampened the enthusiasm to nuke Berlin, even if it was only a low-probability chance ...

Regards,

Henning (HoHun)

[ratdog]

and the junkers 390 made it possible for them to drop it on one of our cities because one mission they came within 12 miles of new york

[kool kitty89]

The validity of that has been discussed ad nauseum, I'll dig up the thread...


However, a one way trip could be made by, say an He 177B/277, which had the payload (and iirc bomb bay size requirements) capabilities as well. I believe the Ju 290 (if suitably modified) may have been possible to do it with as well.


But the question is would the Germans have had a nuclear bomb available? And IMO the answer is no. There just wasn't serious work being done to develop one, and out of the relatively small nuclear projects that were going on all serious reasearch was going into development of reactors and nuclear power development.


Had work been concentrated on weapons development and producing sufficient amounts of enriched uranium for bomb use, it may have been possible, but I doubt they would have been able to complete more than one (in the 10 kTon class) or maybe a couple smaller ones. I'm not sure if there was work being done on breeding plutonium. (which can be produced much more quickly than enrichiching natural Uranium to weapons grade -hence why the US only completed a single Uranium bomb, while they had enough material to build 3 Plutonium bombs by the wars end)

Of course, the functioning mechanism of the Uranium bomb can be made much simpler (gun-type opposed to implosion) than a plutonium bomb. (which is why the US decided it necessary to test their plutonium bomb before deployment)

The point is,, German devleopment was minimal in terms of a bomb.

Otoh the Japanese focused their 2 projects -1Army + 1Navy- solely on Uranium enrichment and weapons development. And there is evidence of a posible test of a staged device just days befor the surrender. (from the more secret IJN project off shore of N. Korea)

[ratdog]

that could have been bad

[kool kitty89]

Yes (I assume you're referring to my discussion on German development), and it possibly could have ended the war in a stalemate with the begining of a cold war with the Axis in place of the Soviets.