Design Off?

[Burncycle]

Looking at that YAK, I imagined JSF with an F-23 like exhaust.    

[Mossie]

Yeah, but I kind of wonder how much they value the pilots? A fold at that much of a wing load joint seems rather "Petrov, Ve need ze space" rather than "Hey, let's make it safe".

Sounds very Russian, that's for sure!

[Planeman]

actually, with a little bit of manipulation, the exhaust thrust would work quite well out of KF's design...energy has to be relocated.  There is a a bias in some people's thinking about turboprop vs jets...Harriers are a prime example...horrible waste of fuel and energy.

So trun the squirel cage fan from a shaft rather than bleed air?

Actually isn't that how the F-35 runs its single lift fan?

I think we could combine the shaft drive feature with the squirel fan Idea to give a much more narrow/compact fighter than even the Yak-141.

The gearbox etc adds weight and thrust/weight advantage is less than lift jets, but it frees up design a lot.

Here's a rough sketch of the sort of layout that could be used - any similarities with the F-32 are coincidental. The main engine would be the same as on the Yak-141, but the removal of the liftjets allows a narrower fuselage:


The wings would fold right at the root and use probably not have onboard hydrolics to do the folding, relying on crew served devises to fold them (saves weight but makes it crew intensive?)



Re the Su-33s fold, I'm pretty sure that there's never been a crash attributed to its wing fold mechanisms, so guess their faith is well placed.

[kitflubber]

Planeman,

That was my reasoning for the squirrel cage fan -- to save  much-needed body space for weapons and fuel. The lift fan JSF loses range and payload -- this plane, with long, narrow fans, minimizes the tradeoff.

[Planeman]

We could make the jet even narrower by putting the squirel cage fans more inside the fuselage, approximately in the dorsel spine just behind the cockpit, where the main fuel tank normally would be (on most jets).

Of course, as with any VTOL jet, fuel capacity becomes an issue.  

[GTX]

Guys,

I hate to rain on your parade, but I doubt the "squirel cage fans" will provide the thrust you require for VTOL flight.  If you're not too worried about practicality, then that's fine and whiff away, but if you want it to appear realistic, you would need to change the design.

Regards,

Greg

[cthulhu77]

I think you're wrong.  But there is only one way to prove that it can work, isn't there?

[kitflubber]

GTX,

Sorry for not answering sooner -- been busy. I really have no idea whether a squirrel cage turbine would work. I based the idea on a German fan design from the sixties (a tabletop fan!). It just seemed like an attractive design alternative to big circular fans. On the topic of more conventional lift fans, here is an image of my earlier design. It would not be attractive to Planeman's purposes, since less of the wing can fold:

[Planeman]

A big single fan like on the F-35 is more efficient but makes for a wide fuselage because the intake ducts have to go around it.

I can picture a variation of the squirel cage fan in my mind that would produce a lot more thrust by compressing the air to a much greater extent.

A similar fan (in some ways anyway) is used in fanwing designs. The fanwing is virtually incapable of stalling and with vectored thrust (as has flown) can take of almost vertically. Not suitible for fast jets because of the drag factor (transonic buffering of blades likely to prevent supersonic flight anyway). But it does demonstrate that longitudinal fans can be made sufficiently powerful for flight.



A fanwing would be ideal for observation and ASW purposes. Or as a gunship.    

[Planeman]

I think that the squirel cage idea of longitudinally (spelt?) fans is great because it allows for a narrow fuselage, which would be key for the optimum fighter to fit into the tubular hanger of the sub. But I think that a bit more of a corkscrew to the blades and a compressive cone shape would help.

Here's my current layout thinking, using the fan exactly as illustrated by Kitflubber


The engine would be the same as on the Yak-141, but drive the squirel cage blades as per the F-35.

Main problem is that there's virtually no space for fuel.

I've given it a cranked arrow wing like on the Indian LCA but with much more dyhedral (wing tip much lower than root) and it'll probably have wingtip launchrails for AAMs.

The wings would fold virtually at the root making it about 8m tall, but only about 3-4m wide with wings folded.

I'm stuck on the tail.

[kitflubber]

Planeman,

Yeah, I remember seeing the Fanwing on a discussion of exotic aircraft on this forum. I was considering presurizing the flow when I drew my original sketch, but then I was assuming we would merge the flow with exhaust gases as well.



I see the squirrel cages will serve you well to make a narrow fuselage for the Typhoon's space contraints -- I was thinking of a more conventionally sized craft that sacrifices less room in the fuselage to lift fan space.

[kitflubber]

Oh great drawing BTW -- love your idea of pressurizing longitudinally.

[rallymodeller]

Re the Freestyle: The main reason it was not adopted by the AV-MF was that the main engine had to be in full afterburner to lift the plane, and that had a somewhat unfortunate effect on the Kiev's flight deck during testing (!). The Freestyle is basically a sound design but needs an engine more powerful in non-reheat.

And also in reference to submersible carriers -- for those who know of Robotech/Macross, both of the ships that made up the "arms" of the SDF-1 were said to be at least semi-submersible -- the landing ship "Daedalus":


and the aircraft carrier "Prometheus":

[Hobbes]

It seems to me that a squirrel cage fan has huge pumping losses: part of the air will be trapped in the fan instead of being propelled out.  

[Planeman]

My variation on the squirrel fan VTOL fighter is still plodding along. The twin boom arangement was mainly motibated by fuel concerns. They fold as part of the wing, with the all-moving tail finf folding on a clever way that I'll have to draw to explain.

I've tried to incorporate radar signiture reducing technology and shaping bt with external stores a must, it's not in the league of the F-22.