difficult, but if the two elliptic.al shot bags are em-
ployed, they must be lifted simultaneously upward and
outward away from the balloon. As the cell rises, each
piece of gear must be cradled by its bearer allowing it
to be lifted vertically when the balloon passes overhead.
In many instances where the wind direction is ~ot constant
at the surface or changes as the balloon goes upward, and
exact downwind positioning of launching personnel will be
difficult. It is often necessary for these men to run to
one side or forward or baekward to get directly beneath
the balloon. In cases of extreme wind speed, it has been
found necessary to load the lower pieces of equipment on to
a truck bed before release of balloon and launch 1t by
driving underneath the balloon.
It is possible to estimate the space required to launch a
train of given length if the wind speed is known. By using
the computed figure for rate of rise, the length of time re-
quired to lift the entire train is found. The distance
the bubble will travel during this time is proportionate to
the wind speed. For example, if a train 250 feet long is
launched with the rate of rise at 500 feet per minute, a
bubble will move downwind at 660 feet if the wind is 15
miles per hour (22 feet per second), and the man at the end
of the equipment train must cover 410 feet in 30 seconds
carrying the gear with him.
The use of a restraining line attached to the load line above
any heavy gear or delicate gear is recommended. A loop in
this restraining line is attached to a winch mounted on a
track a few hundred feet downwind of the lowest piece of
gear, or is held by a well-gloved man. The safety ~~ights
are attached near the end of this line. The balloon tends
to pull the gear in beneath itself in calm or light winds,
and may pull sidewise if the train alignment is not perfectly
downwind; the restraining line withstands this pull. Thus
tethered, the b•lloon is forced to come overhead of the equip-
ment bearers, and they are able to launch with less diffi-
culty and danger of equipment damage. If the apparent ascent
rate is too slow, the restraining line is cut between the
.safety weights and the other pieces of equipment. If the rate
of rise appears to be high enough, the restraining line is
severed below the safety weights and they rise, completing
the launch:i.ng.
VII. TRACKING AND ALTITUDE DETERMINATION
Following release, it is often necessary to know the position
of the balloon and its height as long as possible. Several
methods of position and height determination have been found
useful. Advantages and limitations of each system are given.
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