What are they made of?
The envelope is made of about 1000 sq. metres of reinforced nylon fabric called rip-stop nylon. It is very light but very strong. The fabric is chosen particularly because it does not support a flame and retains its strength in such a way that any tears will not propagate.
How big are they?
Diameter of an average envelope is 17 metres, height is 24 metres. Its volume is 2,100 cu. metres.
What kind of fuel is used?
Common propane or butane is used. It is carried in liquid form, under pressure, in the tanks, and routed in the burners in flexible hoses. There it is atomized from the heat and ignited as it is directed upwards into the balloon. The flame may shoot as far as 2.3 metres in the wide open blat that the pilot controls.
How do they inflate them?
A balloon is quite unwieldy on the ground, especially in gusty winds; much like a great sail. You need at least five people to handle the balloon. A fan is most commonly used to hill the envelope with ambient air. Then as the air is heated with the burners, the balloon rises to a vertical position.
How high can they go?
Flight in this type of balloon of over 12,000 metres has been recorded, but is rare. The sport of balloonind is most rewarding at 60-160 metres, floating over the countryside.
How fast do they go?
As fat as the wind blows. But if it is higher than 13 kms. per hour at ground level, the balloons normally are not going to inflate.
How long can they stay up?
Normally about two hours depending upon the ambient (outside) air temperature. and on weight carried. Some are equipped with enough fuel to stay up for over 20 hours to establish distance and duration records.
How do they steer the thing?
Generally speaking, you don't. It goes where the wind goes. The trick is to pick an altitude that has the wind direction you want. Surface winds are usually always blowing 90 degrees opposed to the winds 1000 metres above the ground, sometimes even 180 degrees and are reasonable predictable.