High Altitude Environment

Flight Profile

Maximum Altitude: hmax = 125,000 ft = 24 miles = 40 km
Ascent Time: ta = 2 hr = 7200 s 
Ascent Rate: va = 18 ft/s = 1050 fpm = 12 MPH = 5.5 m/s
Maximum Range: Rmax = 300 miles = 500 km
Float wind speed: vb = 68 knots = 78 MPH = 115 ft/s = 35 m/s
Float time: tb = Rmax/vb = 3.8 hr =13700 s
Impact speed: vc = 20 ft/s = 6 m/s

Environment at Sea Level:

Air Temperature: T0 = 288 K = 15°C = 59°F = 518 R
Air Density: r0 = 1.225 kg/m3 = 0.07648 lb/ft3 = 0.0023769 slug/ft3
Air Pressure: P0 = 101325 N/m2 = 2116 lb/ft2 = 14.69 lb/in2

Expected Environment at Float Height (40 km):

Air Temperature: 251 K = -22 °C = -8 °F
Air Pressure: 0.040 PSI = 0.0027 atm = 0.27% of sea level
Air Density: 0.00024 lbs/ft3 = 0.30 % of sea level
Wind Velocity: To the West at 68 knots = 78 MPH
Gravity: 9.68 m/s2 = 98.8% of sea level
Energy Flux from the Sun: 1400 W/m2
Energy Flux from the Earth: 500 W/m2
Cosmic Ray Flux: 100,000 per sq.meter every 10 seconds
Gamma Ray Flux: 1 per sq.meter every 10 seconds

(For more information on how the expected environment at float altitude is derived from conditions at sea level and from simple physics, check the Environmental Models page...)