2. How high can aircraft fly?
How do aircraft fly?
What changes when planes fly higher in the atmosphere?
What limits how high aircraft can fly?
Can we design different aircraft?
Who wants to go that high anyway?

3. How do aircraft fly? 4 forces: thrust from the engine(s),
drag from aerodynamics of the aircraft,
weight of the aircraft,
lift generated by the flow of air over the wings

4. What affects these forces?
DRAG – is friction of air molecules against the aircraft, less air = less????
THRUST – engine pushing aircraft forward, engine runs on ????, needs ??? Molecules to burn ?????
LIFT – generated by gas molecules passing over wings, less molecules = less ???

5. Soooooo…..
What changes in the atmosphere with altitude????

6. Things we already know about the atmosphere
Pressure __________ with higher altitude
In other words, there are less ________ in the atmosphere
Air is less __________ at higher altitude
Also…less _______ molecules at higher altitudes
Gravity is less too, but doesn’t make a big difference in weight

7. OK, then what limits flight?
Is it lift (less gas molecules) or is it airbreathing propulsion (less oxygen)?
It depends on the aircraft……
Helicopters can’t fly as high as Mt Everest because of loss of lift…not necessarily because the engine doesn’t have enough oxygen

8. At altitudes < 10 - 12 km, there are several aircraft choice
At altitudes < km, there are several aircraft choice. At altitudes > 12 km, however, there are few choices.
Human factors are important – there are limits on altitude vs pressurized cabins in commercial aircraft

9. So what aircraft fly where?
mi km
353,000 ft
‘outer space’ begins 327,
163,
85,
65,
35,
30,
space shuttle
X-15 A L T I U D E
Weather balloon
stratosphere
SR71
NASA ER-2 high-altitude aircraft, U2
Commercial flights
troposphere ft mi km

11. Tropopause can be as high as 15 km in tropical regions
For a manned balloon,113,740 ft. set in * For an unmanned balloon, 173,884 ft. set in 1972.

12. Can we design aircraft to fly higher or outside the atmosphere?
Can use fuels that requires less oxygen (methane, hydrogen) but we still have to carry oxygen to burn the fuel
The moon…been there, done that…
But we had to carry our own oxygen to burn fuel (and to breathe)

13. Why do we want to fly so high anyway?
If you want to get to ‘outer space’, you must pass through the atmosphere !
Staying inside the atmosphere? Why?
Study the weather
Study changes in the atmosphere
Global warming
Depletion of ozone layer (Stratospheric ozone has been a principal research focus with the NASA ER-2 high-altitude aircraft since the discovery of the ozone hole in 1985)
Anything else you can think of?

14. Latest and greatest
Experimental aircraft is the solar-powered Helios Prototype, an enormous flying wing that spans 248 feet (74 meters), but weighs just 1,600 pounds
(720 kilograms). Wider than a Boeing 747, the top of the Helios Prototype is clad with solar panels, which, its designers hope, will power the plane to rise above 100,000 feet.
Instead of the massive rocket required to launch a payload into space, a high-altitude airplane simply needs a runway.

15. In a galaxy far, far away……
Space shuttle - consists of the orbiter, propulsion systems-two solid rocket boosters (SRBs) and three main engines, and an external fuel tank. (liq H, liq O); while in orbit, uses smaller attached rockets
Solar winds – like sailors used currents and wind ??