roswell

AUGUST 1948 AT HE L STAN F. S PI L HAC S, C. S. S C H ~EIDER, A~ D C. B. l\1 0 0 R E 133
capsule and linkage is of conventional design but in
place of the commutator bar, a motor driven helix is
employed. This system permits the determination of
FIG. 4. Minimum pressure switch (mercurial).
pressure data without knowledge of the history of con-
tact sequence or of the ascent or descent of the balloon,
as is required in the conventional radiosonde.
5. Tracking of the balloon
The balloons that have been flown by the writers
usually have been tracked by theodolites. Airplanes
have also been used, to extend the observations. These
two methods require the balloon to be visible and not
obscured by cloud cover. When available, ground
radar has been used in tracking the balloons, with
good results.
A series of SCR 658 radio direction-finders is also
used, arranged in a net along the expected trajectory
of the balloon. In addition, aircraft equipped with
inverted search radar have been employed to extend
the tracking net.
6. Flight results
While the characteristics of various plastics were
being investigated, four preliminary flights were made
with clusters of ordinary meteorological balloons, from
16 to 26 in number, to which two to four towing
balloons were attached. The towing balloons were cut
free by a baroswitch at a predetermined altitude. The
remainder of the balloons were inflated so that they
exactly balanced the load hung from the cluster. To
offset diffusion, sand was dropped from an arrange-
ment of tubes, 9 to 16 in number, each containing
about 200 to 1500 grams of sand ballast. This ballast
was dropped by a baroswitch mechanism on descent
only. Some of these flights were relatively successful
as a beginning method but the dropping of discrete
quantities of sand caused too great fluctuation of alti-
tude and therefore was abandoned later. The first
successful flight stayed at 51,000 ft, plus or minus 100
ft, ·for 38 minutes; another remained between 30,000
and 40,000 ft for 147 minutes. The latter shows the
same characteristic time-altitude curve as the cosmic-
ray clusters, although its altitude control is superior.
It is not believed that much improved altitude control
can be obtained, utilizing ordinary meteorological bal-
loons. Flight termination was usually due to deteriora-
tion of the balloon caused by the sun.
In the first flight utilizing plastic balloons, a cluster
of ten seven-foot diameter balloons6 was used. The
load on the cluster was 16.5 kilograms. An altitude
control was used. Unfortunately, the maximum alti-
tude reached was not as high as the predetermined
altitude which was selected to seal the diaphragm of
the automatic ballast valve. As a result, the cluster
rose to ceiling and stayed at this altitude for a short
while. Diffusion and leakage of helium produced a loss
of lift at the rate of 125 feet per minute.
The next flight was made with a single polyethylene
balloon, 15 ft in diameter. To insure sealing-off, the
ballast-release diaphragm was set to operate at an
altitude of 12,000 ft, considerably below the calculated
ceiling of the balloon. After a dawn release the balloon
continued to ascend to 15,100 ft where it leveled off,
then slowly descended to 9000 ft due to diffusion
losses. At this altitude the ballast release began to
operate and thereafter the balloon maintained its
altitude within ± 1300 ft for a period of 4! hours before
the radio signal was lost. However, in the first two
hours of this period, before the convection currents
e Made by General Mills, Inc.
LOW DRAIN
ELECTRIC
MOTOR
DRIVING HELIX AT
ABOUT 2 RPM
SUITABLE
LIGHT WEIGHT
HOUSING TO
PROTECT
lt.ISTRUMENT
DURING !'LIGHT
-HELIX
PLUG TO HAVE
CONNECTIONS WIRED
TO EACH CONTACT ARM,
TO HELIX AND
TO MOTOR
FI<i . .'. Olland-cyde pr('ssure mmlulatur.