roswell

which switches four elements into the transmitter circuit in turn.
Recently a motor making five revolutions per minute was used so
that each temperature is transmitted for three seconds. The four
elements are the free-air temperature, the gas temperature, battery-
pack tempereture and a reference signal. This switch is supple-
mented by a master program switch whicp alternately places the
temperature switch and the pressure modulator into the transmitter
circuit. The present arrangement is to permit the temperature data
to be transmitted for about one minute in every fifteen. In this
wt.y represente.tive temperature sampling may be obtained, without
materially destroying the continuit,y of the pressure and ballast
data.
A second system or determining temperature makes use of the smoked
drum of the barograph. By adding a temperature-activated pen, this
unit makes a record of the temperature encountered. Since it is not
the free-air temperature nor the temperature or the lifting gas but
rather the temperature or the barograph itself, the data obtained
has been or little value. Following the development of suitable
temperature telemetering apparatus, this method was not used.
c. Ballast Metering
It is often very desirable to knowwl'ether or not ballast control
equipment is operating properly during flight tests. For this
purpose, two ~stems of ballast metering have been devised. It is
possible (1) to record on an instrument which is balloon-borne or
(2) to detect and telemeter information to the ground concerning
ballast flow.
Figure ~7 shows the automatic siphon which has been used in the AM-1
transmitter circuit for the telemetering of such information. A
series of pulses of fixed frequency is transmitted whenever the
contact arm of the automatic siphon is filled above a critical
level. The electrolyte used is non-miscible with the ballast and
rises and falls in proportion to the rise and fall of the aain arm
of the siphon. This main arm empties when approxiDIIltely 3.5 grams
ot ballast have been allowed to flow into it. As a consequence of
this intermitte~t filling and emptying of the lines of the siphon,
an intermittent slgnal of f'ixed.frequency is transmitted whenever
ballast is flawing steadily. It is important that an electrolyte
be used wHich will not freeze at low atmospheric temperatures and
will not boil at the low pressures encountered. After a aeries of
tests it was decided that a G4% solution of hydrochloric acid be
used for altitudes up to 85,000 teet. It is necessary to use
platinum wire for the contact points.
In order to record in flight the functioning or the ballast control
system a ballast recording mechanism has been developed in con-
junction with the Lange Laboratories of Lexington, Kentucky. This
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