MAXIMUM HEIGHTS OF ASCENT OF OF SPHERICAL RUBBER BALLOONS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP80-00809A000600340153-4
• Release Decision: RIPPUB
• Original Classification: S
• Document Page Count: 7
• Document Creation Date: December 22, 2016
• Document Release Date: August 15, 2011
• Sequence Number: 153
• Publication Date: September 1, 1950
• Content Type: REPORT

Sanitized Copy Approved for Release 2011/08/17 :CIA-RDP80-00809A000600340153-4
f~ t
FIB
~~
~~
'?
.~_-?
SUBJECT
HOW
WHERE
DATE
(ANGUAGE
CLASSIFICATION 8$,cREr~--~
CENTRAL INTELLIGENCE AGENCY
INFORMATiOW FROM
FOREIGN DOCUMENTS OR RADIO BROADCASTS
REPOR~
CD f:0
DATE OF
INFORMATION 1948
DATE DIST. ~ ~f. 1950
f
.._
NO. 4~~ PAGES 7
SUF'PI.EMENT TO
REanRT No.
or iMt YtITtD tile. .Ind. . T-t11w01~1ttlOt Ot Tllt t[tt4i100
t. t. C.. 111110 tt.lt t~ltOtp Alto t~l~tl=to rtltoll a no-
or m eountn a lllr ?ltt 9D
rums n u.. nnotteno~ or mt roe a rlweumt.
THIS IS UNEVALUATED INFURMATION
Meteorologiya i Gidrologi~a, No 3,? 1948?
In clear `reamer, ouc-rv~..~ .:.,o....------ --
for long periods. Processing of these observations indicates heights of ascent
of 30-50 kilometers an3 more. Aa a rule,-the~wind data~ob~ineBily aublished
r
explanatlon for such prolonged o se t from those in
beoa received recently from stations and observatories,~Mesp~cpYi7Q.,}Y?i~ twee of
g
m
limit to the height of ascent end what are the ueations on?this subJect have
vatloas? Many q
b
a
These data differs rp y
kilometers,. sad themfor? should be subJected to closer scrutiny. Ia there a
factors? What is the
itin
li
1 from data compiled for the ue~,~"1 ~eiahts of 10-15
h
envelopes.
Rubber envelopes are usually considered to be ideally elastic. This is a
convenient dehcriptien, but does not actually describe the state Qf the rubber
akin. Yt has now beer established thst te~e*_'Ature limits for highly elastic .
propertiec exist for all types of vulcanized rubber (Zayronchkovskiy, A. D.,
Technology of Leather Substitutes, Gizlegprom, 1940; Treloar, L. R., Reports oa
Progress in phydics,,tVol Ix, Pp 113-136, 1943.) The lower limit is associated
with the transition of rubber molecules into the crystallic or vitreous-like
state, wh7.le the u~rpja~ limit is connec :ed wi+Ih the transition into the state
of a viscous fluid. Noninflated rubber paeses from the amorphous to the crys-
taLlic state at 10 degrees centigrade and lower. The crystall~ltoi~dape~rag~e-
creasas in stretching. CryRttllic formations develop during p
of rubber as well as during cooling and expansion. Crystallization does riot
cover the entire melss; tie csystallic and amorphous. forms .of rubber are found
under certain condltions in unstable equilibrium, with the amorphous part ss; ller
is inflated than in noninflated rubber. Changes in the phase state of molecules
(cryatall,ization) reduce elongation and increase tension ih the rubber skin.
Sanitized Copy Approved for Release 2011/08/17 :CIA-RDP80-00809A000600340153-4
 Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
At about 70 degrees below zero centigrade, rubber molecules enter the
vitrecus-like state, in which rubber becomes friable with practically no
stretch, and sharply increases its ultimate strength.
Rubber balloons in flight are subjected to both low temperatures and
tensile deformations. Decrease in the "stretching coefficient" (gratnost'
rastyazheniya) and increase in stress under negative temperatures both vary
considerably, depending upon rubber type. ingredients, degree of vulcanization,
etc. Thus, the degree to which rubber envelopes approximate ideally elastic
envelopes may vary widely for different types of envelopes.
Assuming that the envelopes are ideally elastic and that the temperature
of hydrogen during ascent is the same as that of the surrounding air, we ob-
tain the well 'mown formula:
Dpi: D3 = G:Gp
where DG and GG are envelope diameter and air density at the surface (before
ascent) and D and G are the same quantities at a certain level. :iince DO and
GO are constants for each practical case the limiting (bursting) diameter
D must be maximum for maximum ascent. ~OTH: This simple formula merely states
mathematically that the buoying force of the atmosphere on the balloon is always
constant??
Thus, the height of ascent of ideally elas~ic envelopes is limited by the
elastic prope^ties of the rubber, the size of ?;:s~ bursting diameter, or. the?
maximum (bursting) stretching coefficient. This conclusion, although long ac-
cepted, is not the complete solution of the problem. We will show that the
strength of the rubber akin is also an essential factor in determining the max-
imum height~of ascent of real balloons.
The existing types of envelopes can be divided into the following cate-
gories:
1. Envelopes whose properties approach those of envelopes made of nonvul-
canized rubber. These envelopes are soft and have little strength; in flight
they have Yixed lift and burst at low altitudes.
2. Envelopes whose lroperties are close to ebonite envelopes. These enve-
lopes have a hard, thick, dense skin and stretch only under great stress; in
flight they have decreasing free lift and. burst at low altitudes.
3. Envelopes which have high elasticity and strength and maintain fixed
free lift is Plight. These envelopes are quite soft. They ars basic in aerolog-
ical practice. The volume of these envelopes in Plight is usually considered
inversely proportional to air density.
~F. Envelopes which have elastic properties at the beginning of flight and
harden at the end of flight. The free lift in these balloons begins to decrease
at a certain height and in some cases reaches zero; that is, the pi4sal levels
off in air. Such rase' are rare in natural latex (or caoutchouc) envelopes, but
are common is envelopes made from sovprene (a syathetic,Fhloroprene rubber.)
5. Envelopes having defects in the skin which form one or several persist-
ent air holes in flight. The Yree 3.if?: in these balloons begins to decrease
after formation of the air hole. They may level off and even drop slowly.
Air holes is latex, seamless balloons have recently become more ,:ommoa as
a reptult of both tae properties of the latex and productioc technology.
- 2 -
SECRET
~~CR~T
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340
 Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
SECRET
Several computations are required to determine maximum heights of ascent.
We begin with calculations of maximum heigirts for ideally elastic envelopes which
can be considered as including the envelopes in category 3? The calculations
will be made for the international standard atmosphere, which is accepted every-~
where for design calculations (Yur'yev, B. Id., Experimental Aerodynamics, Obo;oniz-
dat, 1939)?
The relative variation of pilot balloon diameter with height is shown in
Table 1. For heights about 20 kilometers, the temperature was considered to
be constant (5:i, 50 degrees) ~i].
Latex, Reamless envelopes produced by a plant of GUGbfS (Main Administra-
tion of the $ydrometaorological Service) have the aeromechanical indices shown
in Table 2 (Instructions to drometeorolo ical Stations and Yosts, Ho 1F, Part
1, pp 13, insert, 19
Envelope No
Weight
(grams)
Diameter, 17on-
inflated (cm)
Maximum Bursting
Diameter D (cm)
1
12
2
8
~
2
3d
h
17
80
3
80
5
25
120
50*
360
~0
60
230
-3-
SECRFsT
~SECRE~
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
 Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
-~
SEC~cT
When Billed With $vdrogen
?,tmiting, Burst- Initial Vertical
ing, Stretching Diameter Free Speed W Height of
Dp (~ Lift A (m~m~in) Ascent km
Envelope loo Coefficient
1 5 37-38 14-22 100-120 2
2 4,7 64-67 110-140 160-175 5
3 4,g 80-83 205-250 200-220 to
5~. 3 8 153_156 1,800 300-400 to
*Envelope Ho 50 Wse taken out oY production in January 1945 and replaced
by envelope Ho 100 which is made from sovprene latex.
By using these tables, We can calculate the maximum stretching coefficient
of envelope Ho 2 to ascend to 15 .kilometers (for a norm of filling with hydrogen
according to Table 2.)
For 15 kilometers We find the ratio to be A:D~)_ 1~Sis1~ nslthat aF~xi-
envelope Ho 2, a-!erage DO = 66 centimeters (Table
mum (bursting) diameter of D 66 x 1.85 122 centimeters is required for ascent
to 15 kilometers. This bursting diameter corresponds to a maximum (bursting)
stretching coefficient oY K _ 1?2/17 7.2?
Similar calculations for envelope 3 reveal that the bursting diameter for
a 20-kilometer ascent is D 197, or a maximum stretching coefficient of
K . 197/25 = 7.9?
In order to raise envelope f!o 20 (with a radiosonde) to 10 kilometers, we
need a bursting die~meter D 370 centimeters, which corresponds to s stretching
coefficient of K . 370/60 6.2.
One of the leaders of the rubber balloon industry says that only the best
samples of latex balloons of average size have stretching coefficients of 7-7.5
and that only the best oY large size have 6. In practice, this figure is 5-5.5
for the first envelopes, and 4-4.5 for the second. Similar results Were ob-
tained by the author in numerous tests of envelopes at a plant of the GJGASS.
Dines (The Meteorolaeicsl Magazihe, 1929) writes that he tested many Rfigl.ish
envelopes and obtained stretching coefficients of 7.5 o~y Yor the bast eamplea.
Coefficients about 5.5 were not obtained under flight conditions.
The Ameriwaa balloons, Dagex Ro i00 (Weight lOC grams), Produced by the
De's W1~i Almy Chemical Comps.,{, have uninflated diameter of 36 coefficient aonfd
bursting diameter oY 230 centimeters, giving them a stretching
6.4 (Bulletin oY the American Meteorolo ical Societ_, Vol 18, Ho 11, 1937)?
[xoTS: 230 . 3 x
English radiosonde balloons Weighing 700 Brame, Produced by Guide Bridge
Rubber and Company, have un~nflated diameter of 115 centimeters and burstiay,
diameter oY 520 centimeters; i.e., a stretchinl; coefficient of 4.5? For pr -
War Soviet balloons, stretching coefficient 5 Wen planned for envelope Ho 5
and coefficient 11.5 for envelopes Kos 10, 15, and 20. The coefficient Was
higher in practice, but did not exceed 7 Yor the first anveloi.es and 6 for
the second.
S~C~e
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
 Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
s~c~r1
Thus, we can conclude from many tests that ''he very best fresh latex enve-
lopes Ro 1 only rarely have 8-9, the maximum stretching coefficient {which cor-
responds to an altitude o~ 6 kilometers); envelopes No 2 and 3's corresponding
figures are 7-8 (giving sa altitude oY 35 kilometers for No 2, 20 lsilomet~rs for
No 3); and No 50 has 6-6.6 (20 kilometers). At this tiu!?, the industrjr does not
produce envelopes with nigher stretching coefficients.
The sharp discrepancy in maximum (bursting) stretching coefficient between
iseaceounted foreby defectsin produchion technology and aging ofdthedrubberopes
skin.
Wi;at iu general are the maximum heights for ideally elastic balluona '.chose
volume in flight is inversely proportional to air density? We taken. an extreme
case for 111ustration, namely:
1. We assume that an envelope filled with hydrogen levels off in air in
the "noninflated" state; i.e., the stretching coefficient'is unity. Calcula-
tions show thatppp grams fornrhskin 0.040ecentimete~rsethick?~Accordinglys ~d
a weight of 5,
will have an envelope diameter of 130 centimeters and a weight oY 1,220 grams
for a skin 0.025 centimeters thick.
2. 4ie assume that this balloon is filled with hydrogen to a stretching co-
efficient of 1.1 (i.e., to 1~U percent of the noninflated diameter) for flight.
The free lift will then be 1,600 grams, enough to lift a radiosonde, for -she
insufficient evenTPorcnormal pibaleobservation80(themverticalespeed of theobals
loon is very low).
3. If the maximum stretching coefficient of the first envelope is 6, the
bursting diameter D will equal 200 x 6 1,200 centimeters? interpo~ationlin
204 x 1.1 = 220 centimeters, the ratio D:DO equals 5.45? BY
Table 1, tre find an altitude of 36 kilometers for the value 5.45. .r
Thus, the maximum altitude which can be reached by the best ideally elastic
large envelopes does not exceed 35 kilometers for radiosondes and pilot balloons.
The maximum stretching coefficients (6-8) assumed in the calcul~ii~ys~taural or .
tamed for large envelopes only when they are mode from high-q
synthetic latex (neoprene?).
gow csa we explain the prolonged one-point pibal observations which give
heights of 30-50 kilometers for ordinary ball.oons2 This could be observed only
xhea, the envelopes used belong to the 4th category of our classification. Ac-
tually, if we admit the possibility of complete balancing of the periods beon
in the atmosphere, it can remain in this suspended state for long p
cause har@.eaing of the envelope is accompanied by increase is strength. Thus,
with envelopes of the 4th category, the observer would record for this pexiod
some fictitious hei6ht of the most fantastic proportions. ~~~ Apposaible~
the observer assumes that his balloon rises continuously, forgetting p
'balancing"]
To evaluate the approximate heights at which s~zch balancing might occur for
various envelopes, first assume that envelope No 2 rises, expanding until it
reaches 5 kilometers in flight, and ce,ntinues to rise maintaining constant vo1=
time (D 80 centimeters, according to Table 2) until free lift hen completely:
disappeared.
~~i0~d~ 1
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
 Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
1
Dividing the weight oY the envelope (36 grams) plus the weight of the hy-
drogen (20 grains) by the volume, 0.272 After- nt rpolationtin Table lY wlecfind
meter oY Lydrogen equal to 24~+ g-rams.
a balancing height of 13 kilometers fluatwei vtlof drogenr135 fgramsnvheight
No 3 (weight of envelope, 80 grams, P gh ~Y
of ascent with expansion, 10 kilometers; diameter for this height, 120 centi-
meters), we fled a balancing height of 18 kilometers.
rr^or envelope No 50 (weight of envelope, 360 grams, Plus weight of hydrogen,
270 grams; height of ascent with expansion, 1J kilometers; diameter for this
height, 230 centimeters; ~~eight of radiosonde, 6,100 gr~msi,l~ obtain~ift of
1'cubic meter of hydrogen required for balancin of 66 = 266 ems,
which corresponds to s height oY 13 kilometers, or, Yor t e case of eac~nt
without load, 630/6.5 = 97 ~'~, which corresponds to ly 'ailomrters.
Envelopes of the Sth category differ from those 3ust considered only in
that the pilot balloon will balance more rapidly when an airhole forma. Con-
sequently, the maximimt heights oY ascent will be considerably lower. In addi-
tion, the time oY "suspension" will be considerably less, so that the fic-
titious heights will also be small.:r.
Generalizing the preceding, we reach the following conclusions: ?
1. The maximum height of ascent of the very. best types of large idea kilo-
elastic envelopes made from natural and synthetic latex does not exceed 35
meters.
2. Maximum height of ascent: the best fresh samplescf late:c seamless en-
velope No 1 has 6 kilometers, envelope No 2 has 15 kilometers, envelope No 3
has PO kilometers, and envelope No 50 (without a radiosonde) has 2U kilometers.
3. The heights of ascent mentioned in the beginning of the article ere
fictitious.
4. Fictitious heights, vhich are obtained only ~~pPn siuton thevfollw~
depend upon the length oY observations, which (1?.,ngth) P
ing:'
~. (1) the amount of wind drift of the balloon and (2) the visibility
(for envelepes.b&14ncing "stiffly" in air);
? b.' (1) the height at which the air hole formed, (2) the strength of
the envelope, (3) the amount of gas escaping, (4) the wind drift of the balloon,
and {5) visibility (for envelopes with air holes).
From the computations cited, we conclude that as long as the maximum stretch-
ing coefficient is considered to be the limiting factor in designs and producion
technology, the deiling will be limited to 35 kilometers for good large envelopes,
The ceiling could be almost doubled if we could obtain a combination of elastic
expansion in the beginning and a rigid state at the end, since this would pro-
vide ascent until free lift completely disappears. CalculatioenvelopetNot3eII18
lope Nn 2.could have a ceiling of 13 kilometers instead of 5,1 kilometers in-
kilometera instead of 10; and envelope No 50 (without load), 9
stead aY 10.
In many cases, observations stop because the envelope is lost against the
background of the horizon. In these cases, observations stop before the balloon
burets and therefore the problem of producing highly-elastic envelopes is aca-
demic.
-6-
SECRE?:
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
 Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
-1
sE~~Er
Many researchers have experimentally studied efficient selection of enve-
lope colors for various sky conditions. All of these xere more or less unanimous
in their conclusions, and so ve make reference to only one study.
Thomas gave the folloxing table in his article "Visibility of Colored Sus-
pended Objects in. Pibal Observations" (The Meteorological Maga.::.ne, Vol 62, 1927).
Color of envelopes
Red for lov cloudiness
White up to 2.5 kilometers
Silver for alti~;udes about
2.5 kilometers
White Red
Light-Gray Red or Whitep_
Dark-Gray Red or White
S. I. Troytskiy pointed out that in addition to the color the glass or lus-
ter of the envelope surface is important.
The American Dewey and A].a~}r Chemical Company produces envelopes in three
colors: black, red, white. The plant of the GUGMS has produced eaperimeatal
sets of different-colored envelopes, but, unfortunately, mass production of
colored balloons has not been organized.
In closing, we mention that the maximum height~of ascent is a function of
the degree to xhich-the envelope is filled with hydrogen as veil as of the
stretchii:~q coefficient, strength, and visibility. This factor can be neglected,
hoxever, sit;cA more or less standard norms for filling are used at all stations.
-7-
SECRET
~SECF;E~'
,r~
Sanitized Copy Approved for Release 2011/08/17: CIA-RDP80-00809A000600340153-4
STAT