Thread 64493021

what is more efficient?

> tail sitting VTOL like xbat

> horizontal VTOL like f35/harrier

tail sitting VTOL looks like it uses more fuel (idk why just assuming) but it saves weight by only having 1 nozzle

>>64493044
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>F-35B VTO MTOW 41,000lb
>F-35B STO MTOW 60,000lb
That should answer your question. It's a lot more efficient to get aerodynamic lift than pure thrust.

>>64493147
interesting stats, but im more curious about vertical (horizontal) vs vertical (tail)

>>64493021 (OP)
tail sitters simply bc less weight and complexity, also thrust and intake are better aligned. A helicopter is 100 times more efficient hovering though...

>>64493648
harrier or f35 have a ton of components to redirect thrust down. This is heavy and requires a lot of maintenance. A tail sitter has traditionally been too hard to fly. That's why they didn't do it in the 60s

>>64493797
that makes sense

>>64493794
true

desu RATO seems like the way to go since everything is unmanned now

>>64493021 (OP)
>>64493797
I would guess tail sitters are probably more efficient based on this chart. Probably similar to tilt-wing?
The F-35 uses both a lift fan and direct thrust so it's presumably somewhere in the middle of those two.

>>64493874
but wouldnt a jet and a lift fan have more disk area than one single disk in a tail sitter?

>>64493916
no, not even close. Tail sitters need pretty big props for a given weight, see >>64493797

>>64493931
He mentioned the xbat, not the vbat.
The F100 of the xbat is a low BPR TF.

>>64493797
>>64493931
are counter rotating props considered one disk or two disks?

>>64493974
sorry just googled, AI says its 2

>>64493988
counter rotating props count as 1 disk because the second propeller is not interacting with static air.

>>64493916
Comparing specific designs may yield an answer one way or another, but a tail sitter can probably extend its disk area by simpler means.

>>64494246
how can you extend your disk?

>>64493021 (OP)
The F-35/Yak-whatever method of running a ducted fan via turboshaft is more efficient.

At hover speeds you need to move a large volume of air with a very large intake because you do not have forward speed to increase intake pressure/mass flow.

Also tailsitters can't STOL. STOL is better than hovering because you can get some lift assistance from the wings and flaps.

>>64494285
Make the engine bigger or run a shaft from the engine into a large propeller or something.

>>64494360
but then how is that simpler than the f35?

>>64494364
You don't have to redirect thrust.

>>64494297
All Yaks used lifter jets. The MDD/N pre-JSF VTOL too. That configuration has a thermal problem but it's more efficient weight-wise.

>>64494381
I get what you mean but im trying to picture this and keep imagining a thick asf bulbous looking plane. on the other hand the sideways lift fan in the f35 keeps the body streamlined

>>64493874
it's just for take off and landing. Probably doesn't have to be very efficient