[FoRK] Hover Camera

Dave Long dave.long at bluewin.ch
Mon May 2 03:46:57 PDT 2016


having found myself nerdsniped, here's an infodump to get this  
subject out of my head:

- might not even need much extra insulation; the keratin in feathers  
and talons isn't known as a great conductor: ~10 picomhos
http://www.ece.utah.edu/wp-content/themes/ece-express-theme/uploads/ 
amanda/Electrical%20and%20AFM%20Structural%20Studies%20of%20a% 
20Humidity%20Sensors%20Based%20on%20Keratin%20(Human%20Hair).pdf

- speaking of talons, apparently raptor feet have a ratchet mechanism  
so they passively stay clenched and require active effort to open,  
and pointy talons can produce substantial pressures.

- Harris' hawks do pack hunt in nature, but other species don't.  (I  
have colleagues who employ cross-species hunting teams, implying that  
multiple birds —who already know they must share their prey at least  
with the falconer— would probably be mostly a Simple Matter Of Training)

- more than you ever wanted to know about modeling the "spherical  
falcon" (theoretical model is capable of pulling 1,5g during  
recovery; practical birds appear to exceed this)
http://www.avibirds.com/pdf/S/Slechtvalk8.pdf

-Dave

getting good stoop measurements is apparently difficult; some radar  
numbers I ran across say stoops generally start with 15-20 m/s,  
accelerating to final impact around 40.

going back to the golden eagle vs. zero zero simple impact scenario,  
by the back of the envelope:

preimpact momentum:
eagle:	5,0 kg * 40 m/s	= 200 kg m/s
drone:	0,25 kg * 0 m/s	= 0 kg m/s
postimpact:
system:	200 kg m/s / 5,25 kg = 38 m/s

preimpact KE:
eagle: 0,5 * 5,0 kg * (40 m/s)**2	= 4'000 J
drone: 0,5 * 0,25 kg * (40 m/s)**2	= 0 J
postimpact:
system: 0,5 * 5,25 kg * (38 m/s)**2	= 3'800 J

by way of comparison, a fastball at 40m/s carries:
0,5 * 0,145 kg * (40 m/s)**2		= 120 J
so to get the equivalent of the 200 J dissipated in that impact, we'd  
want a talented pitcher:
0,5 * 0,145 kg * v**2 = 200 J	=>	v = 50 m/s  (~120 mph)





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