roswell

sample stations. Figure 21 shows the calculated net lift of the General
Mills balloons.
c. Balloon Diameter-Weight Relationships
To facilitate design discussions, charts have been drawn up
relating the approximate weight of a balloon to its size and the unit
weight of the balloon fabric. A ten percent increase is added to the
weight over that determined from the surface area to account for seams
and shroud lines. Figures 22 and 23 are these charts.
D. BJLte of Rise
It is important that the rate of rise of a balloon be neither
too fast nor too slow. For example, if a General ~dlls' 20-foot balloon
rises faster than 900 feet per minute, there is danger of rupturing the
balloon when pressure altitude is reached. On the other hand, if rates
of rise under 400 feet per minute are chosen, since the free lift will
be quite low, there is dange~ of: 1) a slight error in inflation resulting
in the balloon's being unable to lift the equipment, or 2) with a wind much
in excass of the rate of rise, the up-wind release failing due to the
dragging of the equipment prior to its be1ng lifted by the balloon.
To compute the tree lift necessary for a given rate of rise, the
equation developed by Korft4 is used. This equation is:
V : 412 (F) j-
(G) f
where F =f~ee lift in grams
V : rate of rise in feet per minute
G : g~oss lift in grams
For our purposes, we wish to find F and have modified the equation
to reads
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