"Keith Willshaw" wrote in message
...

"Charles Gray" wrote in message
...
had actually put a U.S. style R&D system in place during WWII, and
instead of coming up with (however pretty they look on paper)
dozens
of designs that never made it beyond wind tunnal designs and
focused
on say two or three fighter designs.
For example, if they'd pushed through the first jet fighter
design
in 1940 (I forget what it was called), and focused on incremental
improvmeents instead of always running to the next design.

I don't think the German R & D program was so bad. The Germans had
less resources and had to cull more projects.
Their support of jet engine development was infinitely superior to
what Whittle received. Apart from Heinkels sponsorship of von Ohain
Junkers, BMW, Bramo all had been lead to jet engine development on
the basis of




Would this have had a major impact on WWII, or just drawn it out
by
a few months?

There are a number of issues here

1) They couldn't just push on with the initial design
it was no more a workable fighter than the original
Gloster prototype

True, but the He 280 was far in advance and had two engine choices.

von Ohain says Ernest Heinkel looked like he was going to cry when the
HeS 006 was cancelled. The engine was brilliant but its was further
away from production and Heinkel was told it was his own fault when
the RLM was trying to run a national program.


2) The bottleneck for German (and to an extent allied)
jet fighter production was developing an engine that
could be mass produced and have an accceptable
service life. This problem was exacerbated by the
shortage of high temperature alloying elements such
as chrome, nickel and tungsten. The Germans never really
solved this problem. The Jumo engines had a rated life
of 25 hours, which was rarely achieved, at a time when
Rolls Royce jet engines had exceeded 2000 hours

Actually the Jumo 004B had a mean time between scheduled overhaul of
25 hours. The is different from saying an engine service life of 25
hours.

At 25 hours the engine needed two main tasks: A/ the 6 carbon steel
combustion chambers were replaced. This task could have been avoided
if they were made out of refractory alloys or stainless steel; as it
was they were mad out of mild steel with aluminum oxide coating. B/
The turbine was removed, x rayed and replaced if necessary or refitted
for another 10 hours.

The British engines had plentiful nickel and were made of nimonic
alloy which was 80% nickel and 20% chromium.

The Germans had to make do with Tinadur (15% chrom 14% nickel, 4%
Titanium balance steel) or Cromadur ( 18% Chrome, 10% manganese
balance Steel) and then only on the Blades and Turbine Stator nozzles.

(Both Blades materials were used as neither could be manufactured in
sufficient quantity)

Nickel is essential to limit creep and fatigue in the blades. Without
this material the British engines would not have lasted minutes as
they lacked the German cooling techniques.

The Germans were thus well ahead in blade root cooling, hollow cooled
blades, film cooling and were making progress in ceramics for the
stator blades. (Anthony Kay In his History of German Gas Turbines
estimates early 1946 for ceramic turbine stators)

The BMW003 A/E used on the Ar 234 and He 162 shows what they could
have achieved in service life: The BMWs combustion chamber lasted 200
hours and its turbine could be removed, inspected and replaced in 2
man hours with the engine remaining on the wing.

The final Jumo 004C and Jumo 004D rated at a 60 hour a blade life.
These engines gave 1000kg and 1050kg thrust and a Me 262 in combat
trim was recorded at 578mph with these engines.

In the very firsts pre production jumo 004 engines the blades could
give between 100 to 6 hours service. 25 hours was a very reasonable
engine life but upon manufacture away from skilled trades personnel
the quality dropped (the annealing process and heat treatments had to
be done correctly as did turbine balancing and initially manufacturing
quality was quite poor which meant that the engines were given
overhauls at about 10 hours) Eventual quality drifted up again.

The Jumo 004D would also have benefited greatly from throttle
limiting. If the throttle was moved to fast the inrush of fuel would
increase turbine and combustion chamber temperatures by 200C before
the compressor had a chance to spool up and this lead to premature
failure.

The British Engines suffered from this as well.

Note also that the dull performing Mk 1 Meteor suffered protracted
development because its engines had such a large diameter that
integrating them in the airframe was a huge head ache. The Germans
purposefully avoided this issue by choosing axial.



3) Germany never had a shortage of airframes and their
fighters were as good as contemporary western designs and
better than most soviet ones.

I believe the Germans were forbidden to engage La 5 and Yak 9s below
4000 meters because the Russians at that altitude were unbeatable by
anyone German or Allied.

They did however lack
pilots and fuel. As a result thousands of aircraft were
captured on the ground by the end of the war.

Also good materials: 30% of Me 262 losses were to collapsing nose
wheels caused by faulty materials.

The syn Fuel was always of slightly lower grade necessitating heavier
engines. The Me 109 was a tiring airframe that was kept on because
the Jets were expected in 1943 not 1944 and because disruption to
production was not possible. Nevertheless It was still capable of
suprises; eg the Me109K extraordinary climb rate.

The Jets would have solved the German fuel crisis as they are
indifferent to octane number. At wars end me 262s were operated on
centrifuge refined crude oil that was simply heated and pumped in.
The Jumo 004 was designed to run on diesel so this was not too
difficult.


The wind tunnel designs and studies didn't really tie up
much in the way of resources. The really wasteful
project was the V-2/A4 which used colossal amounts
of strategic material, manpower and industrial resources
to produce a weapon that had essentially zero military
usefulness.

Within 12 months the LEV-3 strap down single axis guidance system
would have been replaced with the more accurate 3 axis gimbaled SC-66.

The accuracy while still not stunning would have meant that an attack
by a dozen of these missiles on a bridgehead or airfield would be
quite damaging.

Additionally the beacon controlled guidance system might have improved
as well. The weapon had potential.






Keith