
#37
Jan2110, 05:34 PM

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There is a FAR (I can not remember the number off the top of my head) that governs the testing of noise signatures around airports. It is pretty detailed and measurements are required to simulate an aircraft arriving and departing and at altitudes, of I believe, 400 ft. It has been a while since I have read that FAR. I think it wouldn't be a killer for this application, but it would definitely be a concern. 



#38
Jan2110, 06:07 PM

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Thrun's team setup next to ours in the semifinal, so I had the opportunity to talk him and his team over several days. He's a fantastic engineer, great sense of humor. 



#39
Jan2110, 06:19 PM

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prop noise reduction techniques, then compare with known noise of 200HP turbine or piston engine. 



#40
Jan2110, 06:20 PM

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#41
Jan2110, 06:31 PM

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#42
Jan2110, 06:37 PM

P: 261





#43
Jan2110, 07:01 PM

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Maybe also see another thread for existing HTS propulsion research. http://www.physicsforums.com/showpos...2&postcount=14 



#44
Jan2110, 07:43 PM

P: 4,780

I took issue with a statement made by many of these articles: namely, that you don't need air intakes because it's electric. This is hogwash because anyone that has flown an electric airplane knows they get very hot (battery, motor, and electronics). Cooling them is absolutely an issue. I do not buy that they don't need 'air intakes' for this vehicle. There will be significant power losses in the form of [tex]i^2R[/tex].
Also, how is this thing 'stealth' with big spinning rotors? 



#45
Jan2110, 08:08 PM

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*quick math for gasoline combustion at 30HP requires 1 liter O2/sec, 5 liters air/sec, STP 



#46
Jan2110, 08:17 PM

P: 4,780

How does the fact that a UAV is RC scale, or large scale, change the fact that there *will* be power losses by the engines that pose a thermal problem?
Please explain why you think this is not the case. Also, what calculation did you do to get this 15HP number from? I don't believe this for one second. Also, I did not say 'quiet' I said 'stealth': as in, radar cross signature. 



#47
Jan2110, 08:26 PM

P: 4,780

Let's do a simple calculation using the momentum theory equation of an *ideal* rotor. A real rotor will inevitably require more power:
[tex] P = \frac{T^{3/2}}{\sqrt{2 \rho A}} [/tex] Assuming: [tex] \rho = 0.002378[/tex] slug ft^3 [tex] A = 28.27[/tex] Assuming a generous 6' rotor diameter [tex] T = 300lbs [/tex] (Assume 600lb GTOW) That gives a power of about 25.7HP, very close to the claim on SIAM article of 60HP total (30HP each)! 



#48
Jan2110, 08:48 PM

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Yes: 



#49
Jan2110, 09:03 PM

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#50
Jan2110, 09:03 PM

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#51
Jan2110, 09:11 PM

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For illustration:
NEMA electric motor efficiency requirements Power (hp) Minimum Nominal Efficiency 1  4 78.8 5  9 84.0 10  19 85.5 20  49 88.5 50  99 90.2 100  124 91.7 > 125 92.4 I suspect the typical RC motor is 0.1 to 0.01 HP. You get the idea. http://www.engineeringtoolbox.com/el...ncyd_655.html 



#52
Jan2110, 09:14 PM

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#53
Jan2110, 09:16 PM

P: 4,780




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