HEADQUARTERS FITZWILLIAM FORWARD
c/o Commander, Task Group 7.2
APO 187, c/o Postmaster
San Francisco, Calif.
SONIC BALLOON TEST I KVlAJALEIN
Inclosure G to FITZWILLIAM FORWARD RepOrt
17 ll.ay 1948
The Watson laboratories of Air Materiel Command arranged for ~ne ( 1)
of its sonic balloon teams to participate in the FITZ1iilLIAM proje¢t as a
mobile team to operate in the Central Pacific, at ~AJA~IN, GUAM Qnd HICKMI.
FIElD, HAWAII, in that order, changing location for each of the thlree (.3)
explosions.
The purpose of this exploratory test was as follows: first, to deter-
mine if an atomic explosion's compressional waves are generated in the sound
channel existing between 50,000 and 701000 feet (such waves would qonce~vably
travel unirrpeded for long distances in this channel without touching the
earth's surface); second, to determine whether a sound pick-up uni~ suspended
from a floating balloon could detect compressional waves (possibly undetected
by similar sound units at the earth's surface) by virt~e of the de¢reased
background noise in the high-level sound channel.
Balloons we~e m3de of high·grade plastic, were of tear-drop a~pe, and
were twenty-five (25) feet at their ls.rgest sea-level diameter. The sonic
unit was a combination microphone-transmitter which was suspended ~rom the
balloon and picked up sound waves, transmitting them to a ground directional
antenna connected to a radiosonde receiver (standard SCR 658 air weather
radio recelver). The transmitted sound impulses were recorded on pro (2)
Esterline-Angus recorders.
;. dribble constructed of a five (5) gallon tin incorporating e 11etered
jet to allow a predetermined spillage rate of high grade kerosenerethylene-
glycol mixture was attached to the balloon. This was designed to pounteract
the helium gas seepage thru the surface -ores of the plastic ballopn. This
metered loss of ballast and controlled the rising rate of the balloon at 500
to 600 feet a minute.
Grcu.OO sonic equiJ:nent consisted ot World v:ar II sound ranging devices
utilized to pick up sound waves from an explosion traveling along the earth's
curface.
A radio receiver was used to obtain e:~tplosion time notificati1on code
signals from the ENIWETOK radio station.
The balloon launching site had to have a down-~ind clearance of about
1000 feet to lay out tho JOO feet risers and cables to which 19ere 1
attachod
the microphone-transmitter and dribbler units. Also the site had to be
sheltered from the wind to prevent da~~ge to the balloon while it was being
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