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Electric "missile" type UAV/Drone

Yabadab

Yabadab

Mechanical
Oct 30, 2023
5
Is an electric "missile" like drone/UAV, where the propeller is enclosed in the body tube (fuselage), possible with two BLDC motors (I have picked AT2826 from T-Motor) with 12*6 propellers? Or will I have to look at using Electric Ducted Fans (EDFs)?

EDFs are much more powerful but their efficiency is horrible when compared to the usual propeller based design. They are also more expensive but using two propeller based BLDCs comes around the same price as one EDF. The propellers also force me to make a 12-inch wide body tube, where as the EDF would allow me to significantly down-size the drone.

I also plan on using thrust vectoring using mechanical vanes in the exhaust nozzle, albeit I'm not sure where to begin with designing the vanes and integrating them. The nozzle is a simple converging cone to decrease cross-sectional area and increase velocity, thus, thrust.

Any insight/help will be greatly appreciated.
 
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Two propellers in series will not be very efficient, although I suppose if you increase the pitch of the second it might help. Putting a 2 bladed prop into a tube turns it into a ducted fan of sorts.
 
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Ah, so should I further increase the diameter of the body tube and add a larger propeller & motor or should I bite the bullet and just use an EDF?

Also if I do happen to use two motors, how do I find out on how much I should increase the pitch of the second propeller?

Thank you for your reply.
 
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Well you work through the equations. It isn't rocket science, but there again most rocket science isn't rocket science.
 
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I would also like to state that after careful consideration, we have greatly downsized our payload carrying capacity and as such, the propellers and body tube diameters have been shortened to just 6 inches.

Now all that's left is figuring out if TVC using mechanical vanes in the exhaust stream works, how to design it.
 
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When US-persons offer tech advice here on designs with potentially dubious use-cases, does that constitute an export under EAR / ITAR? :)
 
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Possibly, there again this will have the worst performance of any possible configuration except for flapping wings. People in the past have got into trouble for designing cruise missiles and the like (which is not very difficult if you are after minimum viable product performance), I think we can safely say that cat is long out of the bag.
 
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I'm not in the US, just letting that out there.

On other news, I have decided to use a NACA 0009 airfoil for the mechanical vanes in the exhaust body tube. Now I have to decide whether I need wings/fins for efficiency during horizontal cruising.
 
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