roswell

When the contact is made, the load line is cut and the entire
weight of the dependent equipment is used to pull out a section of
the balloon wall. Through this rupture, the lifting gas can es-
cape, and the balloon descends, using the upper portion as a para-
chute. The rate of descent has been observed to vary from 600 to
1500 feet per minute when this system is employed.
For some special applications it has been desirable to cause the
balloon to descend after some predetermined time, instead of waiting
for the descent to air traffic lanes. In these cases, a clockwork
switch has been used instead of the pressure-activation unit. ~ben
docks are used they are kept free of lubricants which will freeze.
The best results have been obtained from the use of a Dow Corning
Silicone (DC 701) diluted with 30% kerosene. If this is not
available, it is better to send up a clock without any lubrication.
Given relatively loose mechanism (a cheap alarm clock) the differ-
ential expansion of parts which is encountered at low temperatures
is apt to cause less trouble than does the congealing of standard
lubricants.
IV. EQ.UATIOOS AND TF..EORETICAL CONSIDERATIONS
Development of a controlled altitude balloon has led to investigation
of many theoretical considerations applicable both directly and in-
directly to the description of variables encountered in balloon control.
Some of these relationships have been derived directly from standard
hydrodynamic or thermodynamic principlesJ others come from an empirical
study of results of laboratory tests and actual balloon flights. In
this section we will investigate these theoretical considerations and
endeavor to correlate them with actual flight results. A more simple
investigation of the equations necessary for the launching and tracking
of a controlled altitude balloon is contained in Part II of this report,
"Operations."
We shall first consider the relationships which aid in evaluating the
elementary characteristics of non-extensible balloon flight and those
which are helpful in carrying out inflation and launching operations
of such balloons. Next, we shall discuss more complex considerations
involved in balloon flights.
A. Floating Altitude and Altitude Sensitivi5Y
To determin& the altitude at which a non-extensible balloon will
float we must consider the weight of the balloon system, the volume
of the belloon, and the densities of the lifting gas and the
air. [If the lifting gas is 98% helium (molecular weight
4.50 lb./lb. mol), the lift of a unit of gas will be 24.4 lb./lb. mol.
Similarly, if 98% hydrogen were the lifting gas, the lift would be
26.6 lb./lb. mol.] By using these three basic parameters, we can
obtain an expression for the molar volume at which the balloon will
float:
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