Dimensions and Approximate Lift of Spherical Balloons

(Information from Free and Captive Balloons by Ralph Upson c 1926)

Balloon Size:  For any given number of passengers, the required size of a balloon depends on its construction, the kind of gas, and the surplus of gas and ballast desired for maneuvering purposes.  Other things being equal, the surplus gas needed is approximately in proportion of the volume of the balloon.  The following table gives the usual safe passenger capacity, assuming hydrogen of 64 lbs. lift and coal gas of 42 lbs lift per 1000 cu. ft:

 Note: Gross lift is calculated by multiplying Volume / 1000 X 64.5 lbs. (Hydrogen)

Improving lift and flight duration

For  practical purposes all gas balloons are built in basically the same manner.  The ability to fly the balloon for long periods or distances depends on the amount of gas and ballast that can be carried

However, some indirect actions can be taken to improve lift and the amount of ballast that can be carried to help improve flight durations (if all other things are equal):

1. A savings in structural weight increases the ballast supply, gas reserve, and total range of altitude.

2. The latter is also improved by means of keeping the gas as pure as possible. This is best controlled by having an appendix which closes tight on decent.

3. Increasing the resistance of the balloon to vertical motion.

4. Improved means of shedding rain and snow.

5. Cutting down the heating effect due to radiation from sun.

6. Low diffusion fabric and a tight valve.

7. Miscellaneous substitutes for discharge of gas and ballast such as a drag rope.

The last 5 items will make a given supply of gas or ballast go further and will aid in holding a given altitude.

Envelope fabric holds the greatest possibilities for saving weight in items 1 and 4.

Eliminating the net will save weight, improve shedding of water and snow.  If it is designed with equatorial rim  attached to the envelope lines (net less design) increases vertical resistance.