15 years ago
canyons. The forest service could use them to count big horn sheep,
etc. If the weather was fair, wouldn't you like to take a quiet ride
in an airship? Maybe sneak up on a mule deer . . .
There's no question conventional PV would get a blimp going over 25
mph. Boeing's new 40% efficient PV would move an airship at 30 - 35
Assume a football shaped blimp 30 meters long 10 m in dia.
The volume is about 1500 m^3 or over 1 ton of lift using He.
The area is about 250 m^2 on a side which is enough space for 100 kW of
PV at 40% efficiency.
Use this calculator to estimate the drag force:
10 meter dia ball going 9 m/sec => 700 Newtons drag force.
A football of the same dia will have somewhat more drag so, to be
it's 1000 N
Multiply this by 9m/sec for the power = 9000 N m /sec = 9 kW
Assuming prop efficiency is 70% and propulsion efficiency is 60% -- the
props must be big -- only 41 kW will end up as thrust.
So we have 4.5 X more power than what we need to go 20 mph!
Using the propeller rule (p ~ v^3), top speed is closer to 55 km/hr --
cruising speed for a Sonoran pronghorn!
The first PV airship should be named the "Pronghorn."