roswell

To use the first of thes~ principles it is possible to main-
tain a conditi~n of buoyancy by at least the following two me-
thods: (1) dropping a part of the load. as ballast, to match the
loss of lifting gas which occurs as a result of diffusion and
leakageJ (2) replacement of the lifting gas by evaporation from a
reservoir of liquified helium or hydrogen. Of these two methods,
ballast dropping is most satisfactory from the consideration of
simplicity of control and safety of personnel. While the use of
liquid helium is theoretically ·more efficient, the amount and com-
plexity of control equipment adds much to the cost and also the
weight of air-borne equipment.
The development of non-elastic balloons which oe.n withstand high
internal pressure was investigated. Two designs which compro-
mise extreme cost (required for balloons of high internal pressure)
with small wall strength, hence small super pressure, were tested.
At first, attempts were made to control balloon performance by using
buoyancy-load balance techniques with elastic balloons, but the
difficulties which were experienced resulted in the development of
a third principle of operation combining a non-extensible balloon
with a system of controls which can be applied either to a freely
expanding balloon or to a balloon of fixed volume.
III. ME'IRODS OF ATTACK
The work on the development of controlled-altitude balloons may be
divided into three phases, each one identified by the type of bal-
loon which was us.ed. Concurrent with the balloon development was
the design and testing of control equipment required to maintain
the balloon at specific altitudes. Some of the equipment instru-
mentation was used on more than one kind of balloon, but in general
the problems and methods of attack are identified with one of the
three types of balloons.
A. Rubber Balloons
Following the example of Clarke and Korff, assemblies of neo-
prene rubber balloons were first considered. Using these
freely expanding balloons it was necessary to balance the load
to be lifted with the buoyancy given by an integral number
of balloons. One or more accessory balloons were attached to
the assembly to provide lifting force to carry the train aloft.
Vii th the gear at a predetermined altitude, the lifting bal-
loons were cut loose from the train by a pressure-activated
switch,leaving the equipment at floe.ting level, more or less
exactly balanced. Since there is no inherent stability in an
extensible balloon, any existing unbalance will cause the
train to rise or fall indefinitely until the balloon reaches
-a-