Project Sunrise
Los Angeles California 1974
Flight of the Worlds First Solar Powered Aircraft
by
Roland Boucher
In order to determine the climb and glide profile of Project Sunrise we will have to correct both the airspeed and propeller speeds for the effect of reduced air density at altitude. The power required for level flight will increase directly with the increase in airspeed requiring a 400 percent increase in minimum power at the design altitude of 73,000 feet.
3P5
Propeller speed will increase about 250 percent over the sea level value in the thin upper atmosphere and the thrust power required for level flight will increase four times the power at sea level as shown at right.
The propeller chosen for Project Sunrise had an expected efficiency of 60% at sea level rising to 73% at the design altitude of 73,000 feet.
The minimum power required for level flight
both at mean sea level and at 73,000 feet altitude are:
Min Pwr at MSL= 23/(0.85 X 0.60) = 45 watts
Min Pwr at ALT = 23 X 4/(0.85X 0.73) = 148 watts
The climb rate at noon with the solar panel developing a full 445 watts both at sea level and at altitude with an 85% efficient propeller are:
Climb Rate at noon & sea level = (445 - 45) x (44/21.33) x 0.85 x 0.60) = 400 x 1.05 = 421 fpm
Climb Rate at noon & 73000 ft = (445 - 148) x (44/21.33) x o.85 x 0.73) = 297 x 1.28 = 380 fpm