Jet PoDs

Riain · Jul 20, 2013

There have been a few threads about earlier jets lately, which as usual get shot down.

But what are some realistic PoDs to get earlier jet engines?

Perhaps Whittle not making the mathematical error that AA Griffith picked up in 1929. This could allow Whittle to build this:

in 1930 rather than 1937 to prove the concept.

There are plenty of later PoDs but this is the earliest one I can think of.

Archibald · Jul 20, 2013

A turbojet works in a close cycle the following way. The compressor (the fan that suck air into the combustion chamber) is driven by a turbine located at the rear of the engine. That turbine is fed by the gases from the combustion chamber, closing the cycle.
Of course the gases are very hot so the turbine needs advanced alloys.
Now in the motorjet, the front compressor was driven by a piston engine (that added its weight and consumption to the jet, not good)
At least they didn't needed the turbine at the rear.

The motorjet come long before the turbojet, perhaps as early as 1909 and the Coanda aircraft

(although it existed, it probably never flew, as explained here)

http://en.wikipedia.org/wiki/Motorjet

oldironside · Jul 20, 2013

Well, the Coanda may not have flown, but the Caproni Campini N1 certainly did. It made its maiden flight in 1940, but the technology was relatively simple and it could probably have flown earlier. The big problem was that it was a total dead end.

Riain · Jul 20, 2013

The motorjet isn't a particularly useful contraption, not a patch on the turbojet.

MattII · Jul 20, 2013

I'd say a good one would be Aegidius Elling getting some strong financial backing, that could give us jet engines as early as the 1910s, and jet aircraft in the 1920s.

Riain · Jul 20, 2013

In 1920 the RAF receives a report stating that gas turbines have no future in aircraft, based on the inefficiency of existing gas turbines.

In 1926 AA Griffith wrote a paper which changed this view, showing that turbine blades should be aerofoil shaped. Jet aircraft engines cannot occur without this theoretical breakthrough.

phx1138 · Jul 20, 2013

There's one I've come across that makes me wonder...

In the U.S., there was pretty substantial research done on improving turbochargers, which require the same high-temperature, fast-rotating turbines. So why didn't GE (frex) develop a turbine engine...?

It's quite possible. (IDK how widely-known Whittle's early work was. Then again, Ohain was working, so...)

oldironside · Jul 20, 2013

phx1138 said:
Then again, Ohain was working, so...)

Post war Whittle and von Ohain met and compared notes. They basically came to the conclusion that neither knew anything of the other's work, and that they'd solved the same problems more or less simultaneously.

IMHO the jet engine had two fathers and it would be doing a diservice to either of them to give more credit to the other. Whittle's engine was first to run, von Ohain's was first to fly. Honours even.

Riain · Jul 20, 2013

How about Whittle doesn't make a calculation error in his 1930 thesis and as such AA Griffith doesn't dismiss it outright? Could this get the ball rolling on Whittle's engine in the early 30s instead of the late 30s?

Garrison · Jul 20, 2013

Riain said:
How about Whittle doesn't make a calculation error in his 1930 thesis and as such AA Griffith doesn't dismiss it outright? Could this get the ball rolling on Whittle's engine in the early 30s instead of the late 30s?

Doing a little research that certainly seems like the most credible POD offered up to date. Without the error it wouldn't be so easy to dismiss his work and he might get at least some funding and support. It doesn't require huge changes to history for the POD to happen and it seems plausible that it might make a difference so for whatever it's worth I certainly think it makes a good starting point.

PMN1 · Jul 20, 2013

When Whittle explained what kind of combustion temperatures he was looking at, he was laughed at by all but Laidlaw, Drew and Co.

What made them think they could do it when everyone else didn't?

oldironside · Jul 20, 2013

Garrison said:
Doing a little research that certainly seems like the most credible POD offered up to date. Without the error it wouldn't be so easy to dismiss his work and he might get at least some funding and support. It doesn't require huge changes to history for the POD to happen and it seems plausible that it might make a difference so for whatever it's worth I certainly think it makes a good starting point.

So, it wouldn't be unreasonable to just shift the timeline for developing Whittle's ideas six years further back. Rather than having the formation of Powerjets Ltd in 1936 as the starting point, we could have had funding from the Air Ministry in 1930. It would probably have been at a pretty low level - comparable to the private investment Whittle got OTL, but enough for him to make progress at the same rate he did OTL.

So, we could then see the first prototype run in 1931, the first flying test bed in 1935, and potentially the first operational jets by 1938.

Garrison · Jul 20, 2013

oldironside said:
So, it wouldn't be unreasonable to just shift the timeline for developing Whittle's ideas six years further back. Rather than having the formation of Powerjets Ltd in 1936 as the starting point, we could have had funding from the Air Ministry in 1930. It would probably have been at a pretty low level - comparable to the private investment Whittle got OTL, but enough for him to make progress at the same rate he did OTL.

So, we could then see the first prototype run in 1931, the first flying test bed in 1935, and potentially the first operational jets by 1938.

Well with a reasonably simple POD in the mid 20's yeah not impossible. Of course the questions then are; who actually develops the plane? And what's the German response?

If jet engines demonstrate their potential sooner then there might be more interest from some of the bigger companies in developing the aircraft. It probably depends on timing but if someone like RJ Mitchell got interested that could have produce an interesting aircraft...

As for the German's this might well favour Heinkel designs over Messerschmitt as they flew the first German jet OTL. Of course given the tangled politics of the German aircraft industry under the Nazi's that might actually delay their introduction as Messerchmitt tries to play catch up and do their best to undermine Heinkel.

oldironside · Jul 20, 2013

Garrison said:
It probably depends on timing but if someone like RJ Mitchell got interested that could have produce an interesting aircraft...

Hmmm. Maybe a jet powered version of this?

Just Leo · Jul 20, 2013

I have read that a monumental impediment to the development of turbine engines was that they didn't suit tube-and-rag biplanes at all. A trend to a more modern aircraft construction of monocoque fuselages and cantilever wings made of metal has to come along with the advanced engine concept.

I would have liked to see what RJ Mitchell would have done with the project, along with B Shenstone. I wouldn't want Joe Smith touching it. Also like James Martin and Teddy Petter. Also DH, but without booms.

oldironside · Jul 20, 2013

Just Leo said:
I have read that a monumental impediment to the development of turbine engines was that they didn't suit tube-and-rag biplanes at all. A trend to a more modern aircraft construction of monocoque fuselages and cantilever wings made of metal has to come along with the advanced engine concept.

I think you're right, but it would not necessarily have held back development. The first all metal cantilever monoplane flew in 1915...

800px-Junkers_J_1_at_D%C3%B6beritz_1915.jpg

... and by 1931 we had racers that looked like this:

All it would need is for those geniuses at the Ministry to realise that an advanced engine needs an advanced airframe. Actually, that is pretty unlikely, isn't it.

MattII · Jul 20, 2013

And I still say a PoD involving Aegidius Elling could see them in even earlier.

Garrison · Jul 20, 2013

MattII said:
And I still say a PoD involving Aegidius Elling could see them in even earlier.

The fundamental problem there is whether the airframes could advance fast enough to really exploit the engine. In the early thirties maybe but 1910? 1920? I'm not so sure.

oldironside · Jul 20, 2013

MattII said:
And I still say a PoD involving Aegidius Elling could see them in even earlier.

Well, fair enough. I freely admit to knowing almost nothing about Aegidius Elling, so I'm ready to be persuaded. A quick look at his Wikipedia page shows that he did foresee the gas turbine as a power plant for an aircraft. I think the real problems would be temperature - could he have stopped the turbine melting whilst at the same time creating enough power for flight? - and weight. Since Whittle (and probably von Ohain) used his work as a basis, its possible he could have been the first but I'm not a metallurgist, so I'll keep my bullshit opinion to myself this time.

MattII · Jul 20, 2013

oldironside said:
I think the real problems would be temperature - could he have stopped the turbine melting whilst at the same time creating enough power for flight? - and weight.

In 1903 I don't think it would have been possible, no, and perhaps not even in 1913, but the thing with breakthrough engineering is that with enough interest in a problem someone is going to come up with a solution. Hells, it could be that Frank Whittle could work from Elling's base and be one of the first to figure out the metallurgy, maybe some time in the 20s.