INVESTIGATION INTO THE GROUND AND FLIGHT CHARACTERISTICS OF J-100 AND J9-10-300 NEOPRENE BALLOONS

• Document Type: CREST
• Collection: General CIA Records
• Document Number (FOIA) /ESDN (CREST): CIA-RDP78-03639A000500040001-5
• Release Decision: RIPPUB
• Original Classification: K
• Document Page Count: 85
• Document Creation Date: December 22, 2016
• Document Release Date: May 3, 2011
• Sequence Number: 1
• Publication Date: January 1, 1958
• Content Type: REPORT

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INVESTIGATION INTO THE GROUND AND FLIGHT CHARACTERISTICS
OF J-100 AND J9-10-300 NEOPRENE BALLOONS
FINAL REPORT
COVERING PERIOD OF JUNE 1, 1957 - JANUARY 1, 1958
RLP#
DEWEY AND ALMY CHEMICAL COMPANY
Division of W. R. Grace & Co.
CAMBRIDGE, MASSACHUSETTS
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DEWEY AND ALMY CHEMICAL COMPANY RESEARCH LABORATORY
PROBLEM #
INVESTIGATION INTO THE GROUND ANDiFLIGHT CHARACTERISTICS
OF J-100 AND J9-10-300 NEOPRENE BALLOONS
FINAL REPORT
COVERING PERIOD OF JUNE 1, 1957 - JANUARY 1, 1958
OBJECT OF RESEARCH
STUDY THE GROUND AND FLIGHT CHARACTERISTICS OF THE DAREX J-100 AND
J9-10-300 BALLOONS CARRYING CERTAIN SPECIFIED PAYLOADS AND FREE LIFTS.
RLP#
REPORTED BY:
Francis T. Mansur
Project Engineer
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I ABSTRACT
II INTRODUCTION
III GENERAL DISCUSSION
A. Manufacture
B. Theoretical Consideration
IV TEST DATA AND ANALYSIS
A. Test Program
B. Ground Burst Diameter vs Flight Test Burst Diameter
1.) Time and Temperature Effect
2.) Effect of Payload
3.) Effect of Ozone
4.) Effect of Solar Radiation
5.) Effect of Atmospheric Turbulence
C. Performance of Aged Balloons
D. Adverse Weather Flights
E. Ascensional Rate
F. Room Temperature Diffusion Rate of J-100 Balloons
G. Adiabatic Cooling of Inflation Gas
H. Summary of Data Analysis: Conclusions
VII REFERENCES
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TABLES:
1.) Ground-Burst Test Data
2.) Expected Versus Observed Burst Altitude
3.) Cold Cabinet Tests - Prototype Neoprene Balloons
4.) Payload Versus Temperature at Burst
5.) Flight Tests with No Load Attached
6.) Ground Burst Tests With Load Attached
7.) Burst Diameters: Night Flights Versus Day Flights
8.) Aged Balloon Flights J-100 White Balloons
9.) Adverse Weather Versus Clear Weather Flights
10.) Factors for Use in Deriving Ascensional Rate
11.) Theoretical Versus Observed Ascensional Rate
12.) Loss of Free Lift Due to Permeability
FIGURES:
1.) Distance Control by Payload and Free Lift Variations
2A) - 2B) 2C) Light-Weight Modified Radiosonde
3.) Burst Diam. /Ground Diam. Versus Altitude
4.) Time-Altitude-Temperature Curve
5.) Friction Coeficient Versus Reynold's Number
6.) Relation Between Gross Lift and Loss of Free Lift Due to Diffusion
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I__ A&?WCT
An account is given of a series of ground and flight tests designed
to impart information regarding the performance characteristics of the
J-100 and J9-10-300 DAREX neoprene ballons.
The following parameters were considered:
1.) Burst diameter
2.) Altitude
3.) Rate of rise
4.) Permeability to hydrogen at sea level
5.) IIniforinity of performance
6.) Adverse weather flight characteristics
7.) Aging characteristics
The capabilities of the J-100 ballon in particular, have been exten-
sively examined and, wherever possible, explanations have been given for the
phenomena encountered during the test program.
It was found that:
1.) Because of the influence of flight time and temperature on the
elongation capabilities of the ballons, those balloons having a low ascen-
sional rate did not achieve as large a burst volume as those having a high
ascensional rate. Consequently, the bursting altitude for a given paylcad
was independent of the free lift in the range considered.
2.) Because of the inverse relationship between ground volume and
burst altitude, the altitude decreased progressively with each increase in
payload. -
3.) The ascent rate for J-100 balloons in the range considered ranges
from 250 feet per minute with 50 grams of free lift to 660 feet per
minute with 500 grams of free lift. For the J-9-10-300 balloons the
ascent rate ranged from 500 feet per minute with 300 grams of free lift to
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850 feet per minute with 1000 grams of free lift.
4.) The permeability to hydrogen at sea level was found to increase in
direct proportion to the gross lift. The rate of loss of lift was found to
be 11.4 grams/hr. for a 1 lb. load and increased progressively to 48.4 grams/
hr. for a 6 lb. load.
5.) The uniformity of performance of the J-100 balloons was found to
be such that the average standard deviation for a group of balloons having
the same payload and free lift is / 2,600 feet. The ascensional rates within
a group having the same payload and free lift were generally within / 10% of
the average.
6.) It was observed that overcast skies did not appreciably affect
the bursting altitude of the J-100 balloons.
7.) Aged balloons performed well up to a period of 1 year of shelf-
storage.
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II. INTRODUCTION
This report covers a series of tests designed to impart more precise
technical and operational information on Darex J-100 and J9-10-300 balloons
than is currently available. More specifically, it is a study of the ground
and flight characteristics of these balloons for their application to carrying
unusual and varied payload and free-lift combinations. As the science of
meteorology advances, it becomes desirable to have a greater control and
better understanding of the instrument-carrying balloons used either in
studying the atmosphere or in other wind-dependent operations. The J-100
balloon heretofore has been used primarily as a pilpt balloon to determine
wind direction and velocity at various altitudes; also the height, direction and
velocity of clouds whenever the balloons enter their bases. Little is known
concerning the ability of these small balloons to carry unusual payloads or
of their ascensional rates with low free lifts. This study is aimed at clear-
ing up some of the questions involved in this respect, in order to enable the
accurate projection of a predetermined payload to a predetermined point in
space at a known rate of ascent.
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III GENERAL DISCUSSION
A. Manufacture
B. Theoretical. Considerations
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III. GENERAL DISCUSSION
A. Manufacture
Darex meteorological balloons are manufactured from a specially pre-
pared duPont neoprene latex, compounded by the Dewey and Almy Chemical
Company to impart a high degree of stretch, cold resistance, gas imperme-
ability, and resistance to deterioration due to aging and exposure. The proc-
ess used in manufacture is the single-compound-dip, gel-expansion method,
wherein an impervious mold is coated with coagulant and dipped into the latex
compound causing a thin gel to form on the mold. Progressive diffusion of
the coagulant salt through this thin layer coagulates to form a thicker, finely
knit gel. The thickness of the gel is determined by the length of time the
mold is allowed to dwell in the compound. Once the desired thickness is ob-
tained, the mold is removed from the compound and allowed to air set for a
short time until the process of spontaneous exudation of serum, known as
synaeresis, commences. The gel is then immersed in water which causes
an osmotic flow of the serum to take place with a consequent increase in total
solids. The gel, after toughening, is stripped from the mold, washed, and
inflated to 4. 75 times its original diameter and dried to permanently increase
its size. The mechanism by which it is believed this permanent increase in
size takes place, is that during the expansion of the gel the polymer micelles
move on their water matrices until such time as when the area has become so
large that the now thinly dispersed water no longer affords lubrication. and the
micelles come in contact with each other resulting in adhesion and loss of
further plastic movement. Inflation beyond this point becomes elastic and re-
versible. Once the balloon is dried it is vulcanized in a hot air oven for six
hours at 2300 F. then inspected and packed in cartons to be opened again only
when ready for use.
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The factory specifications for the balloons studied in this project are the
following :
Sea-Level Thickness
Burst Sea-Level At At
Type Weight Diameter Diameter Burst Volume Flaccid Burst
J-100 100 gms. 16 inches 90( ) inches 216 cu. ft. ( ) .004 inch . 0001 inch
J9-10-300 300 gms. 29 inches 12.5 ( ) feet 1, 023 cu. ft.( ) . 004 inch . 0001 inch
B. Theoretical Considerations
Archimedes law states that the buoyant or upward force exerted on a body
immersed in a fluid is equal to the weight of the fluid displaced. A body im-
mersed in fluid displaces its own volume of fluid. If the weight of the fluid
displaced equals the weight of the body, the body is in equilibrium. If the
weight of the fluid displaced is greater than the weight of the body, the body
rises, and if the weight of the fluid displaced is less than the weight of the body
the body falls. Thus if a balloon is filled with a gas having a density less than
that of air, the balloon will possess a buoyancy or gross lift as expressed by
the following equation:
L = V(da - dg) where: L = gross lift or buoyancy, = free lift+payload
+weight of balloon
V = Volume of gas.
da = Density of air.
dg= Density of gas.
In the case of an extensible balloon, if the gross lift is greater than the
weight of the balloon and its payload, (i. e. if the balloon possesses a "free-lift"),
and if the balloon is tied off so that no gas can escape, it will rise. As it gains
altitude the atmospheric pressure decreases because of a decrease in air den-
sity. This decrease in air pressure allows the volume of the gas inside the
balloon to increase and thus expand the balloon. The balloon continues to rise
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and expand in this manner until it reaches a point where the film becomes so
thin that further expansion is no longer possible and rupture occurs, thus
terminating the flight. The relationship between gross lift and altitude can
easily be seen if we can assume a most probable bursting volume. If a bal-
loon starts its ascension with a large ground volume it will require a certain
decrease in atmospheric pressure to expand to its bursting volume. A simi-
lar balloon starting off with a smaller volume will require a greater decrease
in pressure and thus a higher altitude, to arrive at its bursting volume.
Since the ground volume depends on gross lift it is evident that altitude is
also dependent on gross lift.
Thus it is possible to control the altitude at which a neoprene balloon will
burst by choosing the proper payload and free lift. Since the free lift also
determines the ascensional rate the time spent in flight can also be controlled.
This relationship is represented graphically in figure 1.
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IV. GROUND AND FLIGHT TEST DATA AND ANALYSIS
A. Test Program
B. Theoretical Relationship Between Ground Diameter,
Burst Diameter and Altitude.
C. Ground Burst Diameters versus Flight-Test Burst
Diameters.
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A. TEST PROGRAM
In order to obtain.a more accurate knowledge of the capabilities
of the J-100 and J9-10-300 Darex neoprene balloons the following test, program
was carried out during this project.
TASK I. Existing Data. and Ground Tests
Phase (a) Study the existing data on J-100 balloons as compiled by the
U. S. Weather Bureau. The balloons tested by the Weather Bureau carry no
payload, bursting elevation being determined via theodolite tracking technique,
and are valuable in determining the maximum altitude which can be obtained
by the J-100 balloon.
Phase (b) Conduct a series of ground burst tests of the J-100 and
J9-10-300 balloons, using existing laboratory facilities, to determine what
bursting dimensions can be normally expected at sea level. These results
are to be compared with a. series of flight tests in order to ascertain whether
or not the balloons are reaching their maximum burst diameters during.flight.
Phase (c) Investigate variations in free lift (and consequently gross lift),
caused by adiabatic cooling of inflation gas at various rates of flow. Since
the volume of a gas varies directly with the temperature of the gas. '(at constant
pressure), more gas than is necessary may be put into the balloon to achieve a
given free lift. As the gas becomes. warmer. it may turn out that the balloon has
more lift than is intended.
Phase (d) Plot the room temperature diffusion rate of the J-100 balloon
inflated to flight dimensions. Sometimes it becomes desirable or even necessary
to hold an inflated balloon for a period of time before launching. In these
cases a knowledge of the amount of diffusion, and consequently lifting force
lost, becomes valuable.
TASK II. Study the performance of the J-100 and J9-10-300 by Field Testing.
A series of flight tests were carried out under varying weather conditions
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and varying payload-free lift combinations. Altitudes and ascensional rates
of the balloons were determined to a high degree of accuracy by use of radio-
sonde tracking technique. Since the standard radiosonde weighs in excess of
two pounds, a problem was encountered in those flights which required a pay-
load of exactly two pounds. This problem was overcome by removing the
radiosonde sensor mechanism from its regular plastic housing and re-installing
it in a hand-made housing of lightweight rigid styro-foam. (For details of pro-
cedure see Figures 2A, 2B.) The flight test program was broken down into the
following phases:
Phase 1.
J-100 clear weather daytime flights. External loads of 2, 3, 4, and
6 lbs. Free lifts of 50, 100, 200, 350, and 500 grams for 2 3 lb. payload, 200
500 grams free lift for 4 6 lb. payload. Five flights for each payload-free
lift combination making a total of 70 flights in this phase.
Phase 2.
J-100 adverse weather daytime flights. External load of 3 lbs. Free
lift of 200 grams.
Weather Conditions:
Light cloud cover --1 _5:flights
Heavy cloud cover - 5 flights
Rain - 5 flights
of 15 flights in phase 2.
Phase 3.
J-100 aged balloons, clear weather, daytime flights. External load
of 3 lbs. Free lift of 200 grams. Total 5 - 20 flights. Enough flights were
flown on aged balloons to determine at what point during shelf-storage their
extensibilities become impaired.
Phase 4.
J-100 nighttime.-flights. External load of 3 lbs. Free lift of 200 grams.
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Weather Conditions:
Clear - 10 flights
Light cloud cover
- 5 flights
-)
Heavy cloud cover-)
Phase 5.
J9-10-300 clear weather daytime flights. External loads of 5 and 10
lbs. Free lift 300, 700, and 1000 grams for 10 lb. load. Free lift of 300 and
700 grams for 5 lb. load, 4 flights for each payload free lift combination.;-
Phase 6.
J-100 clear weather daytime flights. Balloons preheated by a treat-
ment of five minutes in water at a temperature of 180?F. minimum. External
load of 3 lbs. Free lift of 200 grams. Fresh balloons, (no more than 3 months
old,) are used in this phase to determine whether Ainy crystallization has taken
place between time of manufacture and time of use.
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Fig. ZA.
Sensor mechanism is stripped of its plastic housing.
Transmitter is removed from its casing.
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X
an
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Procedure for modifying radiosonde:
A standard AN/AMT-4A radiosonde is stripped of its white plastic housing
as follows:
1.), Remove the studs which anchor the sensor mechanism platform to the
housing.
2.) Cut the wire leading to the humidity element.
3.) Cut the wires leading to the metal thermistor clamps.
4.) Remove the sensor mechanism from the housing.
5.) Prepare light-weight styrofoam housing by cutting a total of 6 sections
to the following dimensions; 2 sections 6. 25x4. 75 inches (these will be
the top and bottom of the new housing); 2 sections _6. 25x2. 25 inches
(these will be the sides); 2 sections 4. 5x2. 25 inches (these will be the
front and back).
6.) Anchor the sensor mechanism to the bottom of the new housing via the
battery wire connections. (fig. 2B)
7.) Cut away part of the bottom to prevent housing from touching aneroid
aELLo
ball' "8. (fig. 2B)
8.) Make sure transmitter cable and ground-check plug are outside of
housing. (fig. 2B)
9.) Build up sides and top of housing with the aid of scotch tape.
10.) Cut two small holes in top of housing and expose temperature circuit
wires. (fig. 2C)
11.) Attach thermistor to temperature leads. Plug in transmitter.
12.) Plug in battery and tape battery to the housing.
13.) Cut away part of side to expose on-off switch. (fig. 2C)
14.) Radiosonde is now ready for use. No humidity element is used.
15.) Remove transmitter housing and cover transmitter with transparent
polyethylene bag if further weight reduction is desired.
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B Theoretical $elatrt onship B tween Burst Volulge 4ndlt rude
The volume of a balloon at burst is calculated from the relationship:
V2 = NR
P2
where: V2 - volume at burst (cubic feet)
fi .;..gross lift (lbs.) = (molecular wt. of air - molecular wt. of H2)
R = 1.33 x 103
T2 = temperature at burst (OK)
P2 = pressure at burst (millibars)
Thus, if a most probable burst volume is assumed from a series of
ground burst tests, the theoretical bursting altitude can be predicted from
the relationship:
T2 - V2
P2 NR
For the sake of convenience in predicting bursting altitude when the
most probable burst volume is known, a graph (fig-3) has been prepared wherein
altitude is plotted as a function of T . The atmospheric conditions on which
. P
the graph is based have been derived from a.)undings taken at Vernalis,
California, the site where the flight tests in Task II were carried out.
Example: Ground burst tests indicate that J-100 balloons will burst
at an average volume of 268 cubic feet. Thus for a ballon carrying a 3 lb.
load with 200 grams of free lift:
N = 3.67 lbs./26.9 = .136 # moles
268 - Y.4? = T2
(.136)(1.33 x 103)
Referring to the graph in fig. 3 we find the altitude to be 46,500
Using the data from the ground burst tests and referring to fig. 3,
I rI
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the expected performances of the J-100 and J9-10-300 balloons were calculated
and compared to actual flight tests in table 2.
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77
f
l
+
--
-----
----
----
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TABLE. 2.1 EXPECTED VERSUS MKT ALTITUDE
J-100 Balloons
Average Ground Burst Volume = 268 cubic feet = 96 inches Burst Diameter
Free
Iri?#`
$
Theoretical
Alti uft
Observed
Ade
Observed
Burst
Volume
Observed
Burst
D er
(lbs.)
(grams)
(# Moles)
(feet)
(feet
( fee
(inches)
2
50
.0884
56,000
40,930
132
75.5
100
.0925
55,000
38,809
131
75.3
200
.1010
53,000
40,636
155
79.6
350
.1130
50,800
41,190
179
83.8
500
.1251
48,500
39,018
174
82.9
50
.1251
48,500
33,666
143
77.4
3
100
.1301
47,800
36,495
165
81.3
3
200
.1370
46,500
35,312
168
81.8
3
350
.1502
44,900
35,285
181
83.9
3
500
.1625
42,900
34,736
191
85.4
4
200
.1750
41,000
30,736
180
84.1
4
500
.1988
37,500
29,900
194
85.9
6
200
.2499
32,000
23,741
202
86.8
5.75
620
.2740
29,200
23,000
218
89.3
J9-10-300 Balloons
Average Ground Burst Volume = 1940 cubic feet - 185 inches Burst Diameter
5
300
.2398
80,000
58,187
803
138
5
1000
.2960
76,000
57,565
993
147
10
300
.4240
64,900
45,392
781
137
10
700
.4580
63,000
46,212
876
11,2
10
1000
.4810
62,000
46,220
930
144
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The calculation of the exact bursting volume of a balloon in flight
presents a problem. It is well known that the temperature of the gas inside
the balloon during a daytime flight is substantially higher than that of the
surrounding air. During a night flight, the temperature of the gas is equal
to or slightly colder than the outside air-, Therefore, in order to calculate
the exact volume of a balloon in flight-from the relationship PV = NRT, it is
necessary that we know the exact temperature of the gas inside the balloon.
Some experiments designed to measure the internal temperatures of balloons
in flight have been carried out by the National Bureau of Standards which
indicate that the internal temperature of balloons in the altitude range under
our consideration is as follows:
Day Flight Regular A411oon*
Altitude
ft.
External Temperature (?C)
Internal Temperature (?C)
Top of Balloon
Bottom of Balloon
20,000
-22.5
-20.0
-10.0
25,000
-28.0
-25.0
-19.0
30,000
-43
-37.0
-27.0
35,000
-52
-45
-36
40,000
-60
-48
-42
For night flights the Bureau of Standards reports internal tempera-
tures as ranging from 0?C to 6?C colder than external temperatures. These
flights were all carried out during the months of December and January.
Presumably, flights carried out during. the summer would give slightly
different results. It is also suspected that flights carried out at different
time of day would differ from each other. Also, it can be reasonably assumed
that the internal temperature of a balloon with a low ascensional rate would
differ from that of a balloon with a high ascensional rate since the faster
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balloon spends less time exposed to the sun and is better ventilated than the
slow one.
A further complication arises if one considers the variance in
internal pressure which-must exist. A cold neoprene balloon skin exerts
more internal pressure than a warm one. Presumably, balloons flown at night
possess a higher internal pressure than those flown during the day, and those
flown during the day differ from each.other to a degree dependent upon the
amount of heating received by the film. Thus: far, to our knowledge, no one
has been able to measure accurately the temperature. and tension of a balloon
film in flight.
Thus, in the absence of precise experimental data, no attempt was
made to measure the exact bursting volumes of the balloons flown during this
program.. Calculations were simply based on the external temperature and
pressure as reported by the attached radiosonde.
*National. Bureau of. Standards. Report.#2530, June 12, 1953, Technical Report
No. 8 "Measurement of The Temperatures Inside -and, Outside of Sound~ng
Balloons During Flight"
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As can be seen from Table 2, the burst diameters and, consequently
the elevations attained in actual flight were considerably below those predic-
ted on the basis of ground burst tests. Moreover, the burst diameters tend to
increase as the free lift is increased and contrary to expectations, reach their
greatest dimensions with the heavier rather than with the lighter loads. This
phenomenon is believed to be largely a function of time and temperature. The
following reasons are offered in support of this belief.
1.) EFFECT OF TIME AND TEMPERATURE
In previous low temperature testing of balloon films by the Dewey and
Almy Balloon Laboratory (1) it was found that at relatively high temperatures
the elongation of rubber like materials at rupture was essentially constant and
relatively high, i. e. , the material was soft and elastic. At very low tempera-
tures the elongation was constant but very low, i. e. , the material was hard and
inelastic. In the range between the relatively high and very low temperatures
the elongation decreased with the lowering of the temperature, i. e., the elasto-
mer progressively underwent a change from a soft elastic material to a hard
inelastic material. (See Table 3.) The sequence of events taking place during
this phenomenon is believed to be as follows: The expansion of long chain poly-
mers exhibiting rubber like properties is the result of two distinct movements;
one the micro-movement of one molecule in relation to an adjacent molecule and
the other the macro-movement of a group of molecules or a micelle in relation to
another. These two movements occur simultaneously during expansion at normal
temperatures. With a decrease in temperature, the macro-movement of the rub-
ber micelles is retarded allowing greater opportunity for strain between the
molecules. At this point there is a rise in modulus of the film as the polymers
resist the forces tending to deform them. Consequently, some spot on the film,
weaker than the rest, gives way and rupture occurs. The rise in modulus of the
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film is attributed to the phenomenon known as crystallization wherein the
movements of the carbon atoms'in the polymer chain are restricted.
The relationship between extensibility and crystallization can be rep-
resented by drawing an analogy between a polymer chain and a coiled steel
spring. If the spring is stretched out until all the coils are straightened, it
will have a certain length. But, if we solder a few of the coils together so
they cannot straighten out, then we will be unable to draw out the spring to
its original length. Thus, if some of the polymers which go to make up a
balloon film are prevented from uncoiling, because they are crystallized,
the balloon will not achieve its maximum elongation. This, we believe, is
the reason why balloons in flight do not achieve the same elongations as bal-
loons inflated at room temperature.
Research by others (9) into the mechanism of high polymer crystalli-
zation indicates that the development of crystallinity in polymers is not in-
stantaneous ax low temperatures but progresses with time-Of exposure.
Curves of specific volume of rubber as a function of time at temperatures
below the crystalline melting point show that crystallization cannot be consid-
ered complete for long periods of time. Thus, the maximum elongation which
can be attained by a balloon is inversely proportional to the time of exposure
to cold temperatures.
12k-
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TABLE 3. ) COLD CABINET TESTS - PROTOTYPE NEOPRENE BALLOONS
CONTRACT C50-KO-761 #158356; #158386
BALLOON # 101 102 103 113 114 115 116
GAUGE THICKNESS (IN.) . 0040 . 0042 . 0040 . 0045 . 0040 . 0045 . 0045
FLACCID DIAMETER (IN.) 4.63 4. 25 4. 70 4. 50 4.50 4. 375 4.56
MAXIMUM PRESSURE 4.8 5. 1 3. 0 14.7 15.6 23.0 23. 0
(Inches H20)
PRESSURE AT 10 IN. -DIA. 3.0 3.5 2. 1 4.7 4.7 22.0 22.0
it 15 IF 2.1 2.6 1.8 4.9 5.4 22.5 21.0
20 " 1.9 2.1 1.4 10.3 12.8 --- ---
" 25 " 2.0 2.8 1.6 --- --- --- ---
PRESSURE AT BURST (In. H20) Z. 0 2.8 2.5 14.7 15.6 23.0 19.4
DIAMETER AT BURST (IN.) 25.5 25.0 29.5 21.9 21.5 18.5 19.5
TEMPERATURE ?F. 72?F 72?F 72?F -45?F -45?F -76?F -76?F
RATIO B. D. /F. D. 5.52 5.89 6.21 4.87 4.78 4.23 4.28
Note that the internal pressure of the balloon rises sharply as the temperature de-
creases, indicating stiffening of the film. Since the area of the balloon varies as the
square and the volume as the cube of the diameter, the normal tendency is for the pres-
sure to decrease progressively with increase in diameter although there is actually an
increase in linear stress in the film. However, as the balloon stiffens as a result of the
low temperature, a much greater pressure is developed per unit increase in surface area.
-5--.
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TABLE 4j PA!j. i,D YjS.~ TE EPxAATQRE AT BII T
J-110 ; Ba}oon
Payload
Zree L itt
Average
Te?-peraLture, At Burst
Average
Diameter at Burst
2 lbs.
200 grams
-48?C
(-54.4?F)
79.6 inches
3 lbs.
200 grams
-43?C
(-45.4?F)
81.8 inches
4 lbs.
200 grams
-36?C
(-32.8?F)
84.1 inches
6 lbs.
200 grams
-19?C
(- 2?F)
86.8 inches
J9-10-
balloons
5 lbs.
300 grams
-62?C
(-79.6?F)
138 inches
5 lbs.
1000 grams
-56?C
(-68.8?F)
147 inches
10 lbs.
300 grams
-59?C
(-74.2?F)
137 inches
10 lbs.
700 grams
-60?C
(-'16.0?F)
143 inches
10 lbs.
1000 grams
-56?C
(-68.8?F)
144 inches
- :kG-
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-
74
-
t
li
}
f
t
{
---
--
-----
-- -
a
r
;_
1
{
-1-
1
-17
P
J
r-
7
r
II
,
4
4
Altitude Thous 11 of Vleet
( ?a ) a1n;8aaduzaJ
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This temperature effect is borne out in actual practice by the fact that
in the case of the J-100's those balloons carrying a six pound payload attained
a larger diameter than those. with a two pound payload. This is in agreement
with the concept of temperature effect since balloons carrying the heavier loads
reach their maximum diameter at an altitude far below, and consequently much
warmer than balloons carrying two pound loads. (See Table 4.) In this connec-
tion, it is interesting to note that in the case of the larger (J9-10-300) balloons
the greatest burst diameters were reached by those having the highest free lift,
but there was no substantial difference in burst diameters between heavy and
light payloads. The "payload effect" did not appear in this case since the max-
ima of the larger balloons is such that very low temperatures are encountered
even in the case of the balloons carrying ten pound loads.
The fact that balloons with the highest free lift attained larger burst di-
ameters than those with the lower free lift and similar payload, can be accounted
for by the fact that those balloons with a low free lift spend a considerably long-
er time, (See Fig. 4.) in regions of low temperature than those with high free lift,
therefore allowing a greater degree of crystallization to take place with a result-
ing decrease in extensibility.
2.) EFFECT OF PAYLOAD:
It would seem, at first thought, that balloons in flight should burst at a
smaller diameter than balloons tested on the ground, because of the strain in-
duced on the balloon film by the payload. On the other hand the flight tests
appear to indicate that the higher the payload, the larger the burst diameter.
This seeming paradox was investigated via two methods: 1.) Study data on bal-
loons flown with no payload attached. 2.) Perform experiments whereby various
loads are attached to balloons burst at sea level.
Phase 1.
The U. S. Weather Bureau, as a matter of routine, carries out flight tests
on production lots of Darex J-100 balloons. In these tests, the balloons carry
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no payload and have a free lift of 500 grams. Burst altitude is determined via
theodolite tracking technique. The Weather Bureau was contacted and the fol-
lowing flight test data were received:
TABLE 5.) FLIGHT TESTS WITH NO LOAD ATTACHED
J-100 WHITE BALLOONS
RELEASE
DATE 1956 TIME LOT 615
BURST ALTITUDE (FEET)
BURST DIAMETER (IN.)
5/27
0730
49i475
74. 0
5/28
0730
56,975
85.0
5/30
0730
59.950
91.0
6/3
0730
55,050
83. 5
6/7
0730
59,950
91.0
6/9
0730
56,975
85. 0
6/10
0731
59,950
91.0
6/11
0731
54,230
81.0
6/16
0730
55,050
83.5
AVERAGE
56,300
As can be seen, even balloons carrying no payload burst at a substantially
lower diameter during flight than those burst at sea-level. It is also noted that
these balloons burst at approximately the same diameter as those flown with a
payload and the same free lift (see 500 grams free lift; 2 3, 4, 6 lb. loads, Table
2.)
Phase 2.
To investigate further the effect of payload on burst diameter, an experi-
ment was carried out whereby various loads were attached to a series of balloons
burst at sea-level. The procedure was as follows: A J-100 balloon was fitted
with a valve closure. A 2.lb. weight was suspended from the closure. The balloon
was then inflated with helium until it just balanced the weight in mid-air. The
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helium tank was then replaced with a compressed air inflation line and inflation
was continued to burst thus maintaining a constant load on the balloon through-
out the entire inflation. The test was repeated using a 4 and then a 6 pound load.
Fifteen tests were carried out for each condition with diameters being measured
at burst by means of moveable vertical rods. The results are as follows:
TABLE 6.) GROUND BURST TESTS WITH LOAD ATTACHED
LOAD
NONE
2 LBS.
4 LBS.
6 LBS.
BURST DIA.
95.0
94.0
96.0
85. 5
(INCHES)
97.5
105.0
95.0
103.0
92.0
90.0
97.0
93.:0
92.0
100.0
95.0
84.0
97.0
90.0
95.0
94.5
100.0
90.0
94.0
85"..0-
92.5
101.5
103.0
97.
93.0
105.5
97.0
87.0
101.0
91.0
82.0
97.0
94.0
86.5
90.0
95.0
89.0
90.0
94.0
86.0
92.0
96.0
94.0
92.0
97.0
90.0
85.0
97.0
94.5
90.0
94.0
93.0
88.0
98.0
9020
98.0
AVERAGE
94.5
94.5
93.5
92. 2
It can be seen that although there is a definite downward trend with increasing
load, the difference is not great enough to fully account for the comparatively
low bursts achieved in flight. It appears therefore, that the strain induced into
the balloon film by the attached load is only partially, if at all, responsible for
smaller than expected burst diameters and definitely does not tend to increase
burst.diameters with increasing load. (It will be recalled that at first glance
the flight test data seemed to indicate that the heavier the payload the larger
were the burst diameters attained.) This further substantiated the theory of
temperature effect.
3.) EXPOSURE TO OZONE:
Ozone is formed in the atmosphere by the action of ultra-violet light
from the sun on molecules of atmospheric oxygen. While the amount of ozone
varies somewhat with the seasons and in different parts of the country, the daily
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concentration at the earth's surface. is from .0 - 50 parts. per 100 million parts
air by volume. Previous work by the Dewey and Almy Chemical Co. Balloon
Laboratory revealed that neoprene balloons maintain moat of their elongation
properties at ozone concentrations up to 680 parts per 100 million parts air
by volume (2). While it cannot be claimed conclusively that atmospheric ozone
plays no part at all in decreasing the expandibility of neoprene balloons, it is
considered to be a very small factor since concentrations larger-than 50 parts
per 100 million parts air are not usually encountered at the-altitude reached by
these balloons.
401 ULTRA=VIOLET RADIATION:
The effect of ultra-violet radiation. on neoprene balloons has been shown
to be negligible by an experiment, performed by Barford et ala (7), which made
use of an "atmosphere chamber" to determine the effects of solar radiation on
both natural rubber and neoprene type balloon fabrics. To simulate the condi-
tions of a daytime flight,, two large ultra.-violet discharge tubes and twelve in-
fra-red lamps were placed at distances in such a way that the total radiation
was equivalent to that due to the sun in the upper atmosphere. The results of
the experiment showed that natural rubber balloons are appreciably affected by
solar radiation, but neoprene balloons are not affected at all.
MAT
BURST EXTUSION
WITH. RADIATION
WITHOUT RADIATION
Natural Rubber
4.7
5.6
Neoprene
4.2
4.3
A further indication that solar radiation does not deteriorate the
balloon fabric daring flight is obtained when-we compare night flight burst
volumes to day flight burst volumes. Calculated.on the basis of ambient tem-
perature and pressure it can be seen from table-7 that there is close agreement
between burst volumes. However, if we take into account the fact that the
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internal temperatures are higher during the day flights then it becomes
evident that day flight balloons achieved a larger burst,- volume- than those
flown at night. Thus it can be reasoned that if sunlight did-have a deter-
iorating effect on the balloon fabric then those.balloons?flown at night would
have burst at a larger volume than those flown in the daytime.
-3?-
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TABLE 7.1
NIGHT PLIGHTS VMMS.DAY FLIGHTS
J-100 BaUQQns
Night Fli.ahts
Dar Flights
Payload
Free Lift
Altitude
Volume
Altitude
Volume
(Lbs.)
(Grams)
(Feet)
(Cubic Feet)
(Feet)
(Cubic Feet)
3
200
38,064
188
31,361
146
3
200
32,214
149
38,661
186
3
200
36,197
170
39,498
192
3
200
37,103
179
36,165
174
3
200
34,695
162
30,8%
140
3
200
34,488
162
3
200
37,795
179
3
200
38,854
172
3
200
35,804
167
3
200
36 , 1
,
Average
35,963
170
35,312
168
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5.) ATMOSPHERIC TURBULENCE EFFECT ON BURST DIAMETER:
It is not felt that atmospheric turbulence contributes to any large extent
to lowering the extensibility of neoprene balloons, except perhaps during the
initial phase of the ascent where, as the balloon rises against the. dense air, a
deformation of the upper hemisphere known as "dishing in" occurs. As a re-
sult of the internal restoring forces and the decrease in velocity, the balloon
does not maintain its deformed shape and springs back to its original spherical
shape. Once the balloon passes this stage and ascends into thinner and colder
air, little or no deformation.occurs since at the colder temperatures and higher
elongation the balloon possesses greater rigidity.
140-
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C. PERFORMANCES OF AGED BALLOONS
It is well known that meteorological balloons, after years of shelf-
storage, deteriorate to some extent. The term "aging" as applied to balloon
films describes various physical and chemical changes that begin when manu-
facture is completed and continue during storage until the product is no longer
suitable for its intended use.
The chemical changes in vulcanized rubber that take ~ place with aging
are attributed to three possible 'reactions:
1. Chain scission - the long molecular chains, which form the major
structure of the polymer, may be cut into smaller pieces. This.
reduces the molecular weight of the polymer and, as molecular
weight decreases, the tensile strength of the rubber is lowered and
ultimately is lost completely. If "chain scission" occurs extensively
in balloons, they will soften and appear to have become unvulcanized.
This phenomenon is known to occur in natural rubber and is called
"reversion". Neoprene, however, is very resistant to this type of
degeneration and in this respect is superior to natural rubber as a
balloon film.
2. Age Crystallization - the linear molecular chains may be tied to-
gether by cross-links. The process of cross-linking due to aging
is thought to be due to the effect of oxygen reacting with the unsat-
urated groups in the polymer. This process, if it occurs extensive-
ly, results in a decrease in extensibility and an increase in the
stiffness of the film. In the case of a balloon, if the process of
crystallization has not progressed too far, this condition may be
reversed, through the action of heat, by immersing the balloon in
hot water (200?F) for a few minutes prior to use.
3. The nature of chemical side groups along the molecular chains may
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be modified. In case of neoprene, chlorine may be split off to form HCL.
These reactions have received considerable attention by many investigators
with the results that compounding techniques have been improved to a point where
any deterioration of a neoprene balloon film due to aging has been reduced to a
very small minimum and has been mentioned above, can normally be reversed
by "preheating!'
Since it is operationally desirable to use balloons without the
necessity of preheating, a series of flight tests was carried out in an effort
to determine at which point the J-100 balloons begin to lose their extensibility.
The results of these tests are as follows.
T 8 _ AGED BALL00N FLIGHTS J-100 WHITE b4LLO NS
LOAD
LIFT
AVERAGE
AVEEA(aL,
LB3
hAMS)
AGE
PIEHE~2
ALTITUDE FTC
BURST D1A ? lW S.
.
3
200
3 MOS
NPJ
o
j5,312
81.8
3
200
3 MOS
5 MIN.. @ 200 F
34,103
80.4
3
kO0
13-15 MOS
NONE
32,518
79.3
3
200
19-20 MOS
NONE
31,367
78.1
3
200
24 MOS
NONE
o
20,820
69.2
3
200
24 MOS
5 MIN. 4 200 F
31,227
77.5
The foregoing data indicates that the J-100 balloons maintain their maximum
extensibility without the necessity for preheating for a period of time well
over lit months.
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D. ADVERSE WEATHER FLIGHTS
For operational purposes it is essential to have a knowledge of the perform-
ance characteristics of balloons under adverse weather conditions for comparison
with performance under clear weather conditions. This phase of the test program
was designed to study the performance of J-100 balloons under the following ad -
verse conditions: Heavy clouds, daytime; light clouds, daytime; rain, daytime;
heavy clouds, nightime. The results of this series of tests is as follows:
TABLE 9.) ADVERSE WEATHER VS CLEAR WEATHER FLIGHTS
ALL FLIGHTS HAVE 3 LB. LOAD AND 200 GRAM FREE LIFT
WEATHER
ALTITUDE (FT.)
Day
Clear
35,310
Day
Heavy Clouds
38,731
Day
Light Clouds
36, 004
Night
Clear
35,663
Night
Heavy Clouds
34,013
The data in TABLE 9 indicates that burst altitudes of J-100 balloons carry-
ing the same payload and free lift are not affected by variations in cloud coverage.
(Flight scheduling was such that only one flight was made successfully during a
very light rain. This flight reached an altitude of 39, 751 feet.. Another flight
launched in heavy rain was forced down by a sudden squall shortly after launching.
By the time a second flight was prepared, the rain had ceased, thus it was not
determined whether the balloon was forced down by the momentum of the rain or
because of an error in making up the free lift.)
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E. ASCENSIONAL RATE
1.) Theoretical Considerations
When a balloon is released from rest (velocity = 0) the forces
acting on it are its weight and the buoyant force of the air. Since balloons
are filled with a lighter-than-air gas, in this case hydrogen, the resultant
force is an upward one and is expressed by:
F V (Da-Dh) - (w + W) (1)
Where: F = Free lift (grams) or upward force.
V = volume of balloon (c.c.)
Da = density of air (grams/c.c.)
Dh = density of hydrogen (grams/c.c.)
w = weight of balloon (grams)
W = payload (grams)
If F-'00 the balloon is accelerated upward and as a result of this acceleration
it acquires an upward velocity and therefore experiences a retarding force.
The magnitude of the retarding force is dependent on the properties of the
fluid (density, viscosity) and on the velocity, shape, and size of the body
passing through the fluid. Through an analysis beyond the scope of this report
the law of motion of a body in a turbulent fluid is given by*:
F = (k/g) Da v2 A (2)
Where: F is the retarding force in grams; k a dimensionless constant
depending on the shape of the body, in this case a sphere, and on the Reynold's
number; g the acceleration of gravity; Da the density of the air in grams/c.c.;
v the velocity in cm/seo;.and A the cross-sectional area in cm2 of the body
* Clarke and Korff (Journal of the Franklin Institute "The Radiosonde" Oct. 1941)
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normal to the direction of flow.
As the velocity increases, the retarding force also increases and
eventually a velocity is reached such that the upward force and the retarding
force are equal. The balloon then ceases to accelerate and moves with a
constant velocity called its terminal velocity. This velocity can be fc?:;;d by
setting the upward force equal to the retarding force.
Since V = 4/3'T r3 and A = 7rr2 where r is the radius of the balloon
in cm. we can rewrite equations (1) and (2) thus:
F = 4/3 Tr r3 (Da-Dh) - (w + W) (eq. 1)
F = (k/g) Da v2 n r2 (eq. 2)
Combining them we get:
F+w+W r3 Dh) a
F 3flr Davx k
v2 = 4/3 g (D Dh) (++ )
From equation (1) we see that
V= F +a + 4/3 "W r3 thus r = (3/41r
Replacing r in eq. 3 by eq. 4 we gets
v'2 = 4/3 g ()
(eq. 3)
F+awFi}1/3
(eq. 4)
F } ( 3/41T )113
(
Da-Dh
) (eq. 5)
Solving equation (5) for v we get
gv = ( /2 (F) 1/2
6)
cm./sec. at sea level (eq. 6)
j+w 3
Values of the resistance coefficient, k, depend on the shape of the
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body, in this case a sphere, and on the Reynold's number, R = vr , where v is
the velocity in am/see.; r is the radius in cm.; u is the kinematic viscosity
(viscosity/density) of the fluid, air in this case.
It is evident thats
(a) according to equation (3), the initial rate of rise depends
largely on the values of r and k for each balloon.
(b) the properties of the atmosphere are continuously changing
with each increase in altitude (density, viscosity and temperature decrease with
altitude).
(c) The properties of the atmosphere are variable at different
locations, time of day and season of the year. (Temperature, convection currents,
winds, solar radiation etc. are variable.)
(d) The properties of the balloon are continuously changing with
altitude (radius increases with altitude, membrane tends to stiffen with decreas-
ing temperature, deformation of shape during ascent, etc.)
Thus it can be seen that the ascensional rate will not necessarily
remain constant throughout the flight nor necessarily be the same for a given
balloon at all times and places.
Since R, the Reynold's number, depends largely on the value of density
of the air, it can be seen that the value of R will decrease continuously with
each increase in altitude. Examination of figure 5'(k versus Reynold's number)
reveals that, for balloons starting off with a Reynold's number of less than
about 1.2 x 105, k will remain constant throughout the flight and according to
equation (3) velocity will be proportional to the square root of the radius,
hence will increase with increasing altitude. In those cases where R is greater
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than about 1.5 x 105, k will not remain constant but at some point during the
flight will increase abruptly when R becomes less than about 1.2 x 105.
Balloons of this type will have a lower rate of rise in the upper portion of
their flight than in the lower portion. If R is very much greater than 4 x 105
then it can be seen that the abrupt change in It may not occur before the flight
terminates.
It has been reported by some investigators (8) who have studied
ascensional rates of various sisee and types of meteorological balloons that
the ascensional rate.
(1) is greater during the day than during the night. (We believe
that this phenomenon is due to the effect of solar radiation on the temperature
of the gas inside the balloon and the tension of the balloon film during flight.
Since the gas is warmer at any given altitude during the day than during the
night, the net result is a larger volume during the day and hence from equation
(1) free lift is greater during the daytime at any given altitude.)
(2) in greater in the afternoon than in the morning and is affected
by local topography. Presumably, these phenomena are due to the variations,
with time and place, of convection currents and temperature.
(3) is affected by changes in wind speed and direction.
(4) is related to the material and shape of the balloon.
(5) is related to the kind of gas used in filling the balloon.
In view of all these factors, it is evident that any formula based
purely on the physical laws of motion to predict the rate of rise of an ex-
pansible balloon can at best be only a close approximation since it is impossible,
within the scope of this report, to take into account all of the variables included
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in the motion of a dynamic body in a dynamic fluid.
However, for practical purposes, we may utilize the data obtained
from the flight tests in Task II of this report and arrive at a general formula
for the Darex J-100 balloons which will be accurate in most cases to within
10% of the average actual rate.
II. Experimental Data:
(a) Average rate or rise for the J-100 balloons in the range under
consideration; the empirically derived formula for rate of rise is:
340 (F) 1/2 ft per minute = average rate of rise
(F,~)3"3
For J9-10-300 balloons carrying payloads in the range of 5 lbs., the
empirically derived formula ist
1+20 1/2
CF / 3 ft. per minute = average rate of rise
For J9-10 300 balloons carrying payloads in the range of 10 lbs. the
empirically derived formula is:
500
F 1/2 ft* per minute = average rate of rise
(F+w+W) 113
A comparison between the ascent rates predicted by these formulae
and the actual ascent rates observed in flight tests indicates fairly close
agreement, except of course in the case of night flights where, as has been
previously mentioned, the observed ascent rates were slower than theoretical.
It can also be seen from Table II. that early morning flights tend to be slower
than afternoon flights in most cases.
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(b) Incremental rate of rise
A study of the incremental ascensional rate characteristics recorded
in Chart A. reveals the following:
(1) In the case of the J9-10-300 balloons
(a) In general the rate of rise is greater in the lower
Portion of the .ight than in the upper portion. This is
thought by us to be due to the relationship between Reynold's
number and the coefficient of friction. That is, we believe
the coefficient of friction increased abruptly at a point
during flight when the Reynold's number decreased below about
1.2 x 105.
(2) In the case of the J-100 balloons
(a) With the lower free lifts, the ascent rate tends to
increase with altitude. We believe this to be due to the fact
that these balloons start off with a low Reynold's number thus
k remains constant, hence velocity becomes proportional to radius.
Another factor may be super-heating of the gas due to excess time
in flight.
(b) In the case of the cloudy weather flights the rate of rise
appears to be initially slightly slower than the latter part of
the flight. It is believed that this is due to the lack of
.direct solar radiation received by the balloon from ground level
until it breaks through the cloud layer.
(c) Ascent rate during night flights is slightly higher in the
initial part of the Sight than in the latter part. We believe
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this is due to the tendency of the balloon film to stiffen
in the low temperatures of the upper portion of the flightlas
well as the fact that the internal temperature is slightly lower
than ambient which in our opinion brings about a slight decrease
in free lift.
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K
AS
.30
.0
W3 S'rANca
Cot"icuT
A Q
8 Q 4
REYNCIDS N4MUUR
o. 1.0 is zoo z.s s.e 3s 4.0 _ R yt ~O
Fig. 5. Variation of resistance coefficient k with Reynold's Number R
vr/v, for a sphere (B) and for ellipsoids of revolution with their major axes
parallel (C) and perpendicular (A) to the direction of motion through the air.
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TABLE 10.) RELATIONSHIPS USED IN CALCULATING RATE OF RISE FORMULA
Density of air at 20?0 = 1.025 grams/liter
Derisity of hydrogen _ .09 grams/liter
Gravitational conatant = 980 cm./sec.
-2
Viscosity of air _ .0181 10 gsaaslcm.sec.
2
Kinematic viscosity of air = viscosity/density = .151 cm. /sec.
Reynold's numbers veloc. of balloon(cm. per sec.) rad. of balloon
Kinematic viscosity (cm.2/ sec.)
Figure 5. Graph Reynold's number vs coefficient of friction.
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J9-10-300 BALLOON
TIME OF DAY
GRASS
FREE
LIFT
GRAMS
GROSS
LIFT
THEORETICAL OBSERVED
FT./MIN. FT./MIN. PAYLOAD
1:30 P.M.
300
2920
510
584 5 lba.
9:00 A.M.
300
2920
510
509
6r50 A.M.
300
2920
510
433 "
1:10 P.M.
300
2920
510
526 "
Average
513
11:30 A.M.
300
5190
500
483 10 lbs.
1:30 P.M.
300
5190
500
478
5:26 P.M.
300
5190
500
519
11:00 A.M.
300
5190
500
average
507
12:21 P.M.
700
5590
745
722 10 lbs.
8:30 A.M.
700
5590
745
596
10:00 A.M.
700
5590
745
697
11:40 A.M.
700
5590
745
Z-Q4
Average
680
3:32 P.M.
1000
3620
865
815 5 lbs.
6:00 P.M.
1000
3620
865
827 "
8:30 A.M.
1000
3620
865
71,4
11:40 A.M.
1000
3620
865
OA
Average
805
11:50 A.M.
1000
5885
875
879 10 lbs.
1:45 P.M.
1000
5885
875
924
4:15 P.M.
1000
5885
875
914
5:55 A.M.
1000
5885
875
Z22
Average 862
TABlE II.) THEORETICAL VERSUS OBSERVED ASCENSIONAL RATES
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3100 BALLOONS
Flight Conditions
Da9 Clear
Time
of
DU
Grams
Free
Lift
Grams
Gross
Lift
Theoretical Observed
Ft. /Min. ?t. /Min.
P*y-
Lead
~_
8:30 A.M.
50
1080
235
251
2 Lbs.
9:30 A.M.
50
1080
235
252
9:12 A.M.
50
1080
235
276
9:30 A.M.
50
1080
235
257
"
Avg.
260
8:45 A.M.
50
1535
207
187
3 Lbs.
12:40 P.M.
50
1535
207
273
8:30 A.M.
50
1535
207
220
"
8:15 A.M.
50
1535
207
227
"
8:42 A.M.
50
1535
207
228
127
Avg.
23
"
10:40 A.M.
100
1130
325
337
2 Lbs.
1:05 P.M.
100
1130
325
342
n
3:40 P.M.
100
11,30
325
322
n
n
11:35 P.M.
100
1130
325
336
n
2:45 P.M.
100
1T30
325
Avg.
342
"
8:30 A.M.
100
1585
290
312
3 Lbs.
8:25 A.M.
100
1585
290
324
"
9:00 A.M.
100
1585
290
308
10:45 A.M.
100
1585
290
326
1:15 P.M.
100
1585
290
Avg.
317
"
11:00 A.M.
200
1230
446
434
2 Lbs.
"
8:30 A.M.
11:25 A.M.
200
200
1230
1230
446
446
417
452
3:30 P.M.
200
1230
446
453
"
1:30 P.M.
200
1230
446
"2
"
Avg.
441
"
11:00 A.M.
200
1685
405
423
3 Lbs.
2:00 P.M.
200
1685
405
405
3:55 P.M.
200
1685
405
399
8:55 A.M.
200
1685
405
374
10:55 A.M.
200
1685
405
"
Avg.
401
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J-100 ' s (Continued)
Flight Conditions
Time
Grams
Grams
D& Y Clear
of
Day
Free
Lift
Gross
Lift
Theoretical Observed Pay-
Ft. /Min. Ft.,411 n: I:oa
11:50 A.M.
200
2138
372
433
4 Lbs.
10:45 A.M.
200
2138
372
429
It
1:50 P.M.
200
2138
372
363
"
3:55 P.M.
200
2138
372
408
w
8:40 A.M.
200
2138
372
2
of
Avg.
400
1:45 P.M.
200
3047
315
344
6 Lbs.
3:30 P.M.
200
3047
315
JL2
w
Avg.
363
"
1:00 P.M.
320
3047
420
477
5.7 Lbs.
10:40 A.M.
320
3047
420
465
"
2:00 P.M.
320
3047
420
480
to
Avg,.
474
2:15 P.M.
350
1380
570
558
2 Lbs.
4:00 P.M.
350
1380
570
553
"
3:45 P.M.
350
1380
570
525
It
"
11:45 A.M.
350
1380
570
556
to
"
2:15 P.M.
350
1380
570
561
it
Avg.
550
?
12:05 P.M.
350
1835
520
545
3 Lbs..
11x00 A.M.
350
1835
520
51.2
9:00 A.M.
350
1835
520
510
10:00 A.M.
350
1835
520
%
"
Avg.
527
10:30 A.M.
500
1530
660
675
2 Lb.3.
1:00 P.M.
500
1530
660
649
3:05 P.M.
500
1530
660
627
M
5:00 P.M.
500
1530
660
611
fl
10:30 P.M.
500
1530
660
655
N
Avg.
643
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J-100'8 (Continued)
Flight Conditions Time
Grams
Grams
of
Free
Gross
Theoretical
Observed
Pay-
Day Day
Lift
Ft./Ein.
Laced
7 n,
_
_
,
3:00 P.M.
500
1985
600
680
3 Lbs.
2:20 P.M.
500
1985
600
650
10:15 A.M.
500
1985
600
660
10:15 A.M.
500
1985
600
598
3:32 P.M.
500
1985
600
,5
Avg.
635
8:34 A.M.
500
2440
565
580
4 Lbs.
8r50 A.M.
500
2440
565
530
8:50 A.M.
500
2440
565
Avg.
548
10:00 A.M.
620
3350
570
656
5.75 Lbs.
3:04 P.M.
620
3350
570
623
"
1:05 P.M.
620
3350
570
6674
avg.
651
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J-100's (Continued)
Flight Conditions
Night Clear
Time
of
De-v
Grams
Free
Lift
Grams
Gross
Lift
Theoretical
Ft./Min.
Observed
n,,
Pay-
load
11:00 P.M.
200
1685
405
299
3 Lbs.
"
9:00 P.M.
200
1685
405
315
9,30 P.M.
200
1685
405
346
11145 P.M.
200
1685
405
347
"
2:03 A.M.
200
1685
405
291
4:25 A.M.
200
1685
405
308
1,00 A.M.
200
1685
405
340
3:2O A.M.
200
1685
405
338
"
10:40 P.M.
200
1685
405
344
1:00 A.M.
200
1685
405
M
Avg.
325
Night Overcast
9:30 P.M.
200
1685
405
308
3 Lbs.
9:15 P.M.
200
1685
405
383
It
9:00 P.M.
200
1685
405
357
Avg.
349
Heavy
Day Clouds
11:50 A.M.
200
1685
405
420
3Lbs.
n
300 P.M.
200
1685
405
416
"
1:30 P.M.
200
1685
405
446
n
"
11:30 A.M.
200
1685
405
435
"
2:00 P.M.
200
1685
405
l7
Avg.
429
Light
Day Clouds
3:20 P.M.
200
1685
405
425
3 Lbs.
9:00 A.M.
200
1685
405
O0
"
Avg.
412
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F. f . ROOM TEMPERATURE DIFFUSION RATES OF J-100. BALLOONS INFLATE
TO FLIGHT DIMENSIONS
The permeation of gases through membranes has been the. subject of con-
siderable experimental investigation. . This process of permeation of a gas through
a film is generally regarded as a combination in series of ; a) adsorption. and
solution by the gas into the membrane at one surface; b) diffusion of the gas
through the body of the membrane and; c) dissolution.and desorption .of the diffus-
ing gas out of the membrane at the other surface. (5). The rate at, which a volume
of gas will diffuse through a membrane is dependent on temperature; pressure;
area of membrane; and thickness of membrane. The rate of diffusion is propor-
tional to the temperature, pressure difference: and the area and. inversely
proportional to the thickness of the film. Because permeability is a combination
of the two functions of solubility and microporosity of the film, it is evident that
the rate of permeability will rise and fall with the temperature.' An.increase in
temperature increases the vibrations of the moleculesnaking up the polymeric
membrane. If this is regarded as a multi-layered reticulum,. then it can be
visualized that the interstices or holes are opened and closed more often or pos-
sibly to a greater extent to increase the possibility of the passage or diffusion.-of
the molecules of gas through them. An.increase in temperature also brings about
an increase in the kinetic energy of the gas molecules allowing a greater frequency
of collisions between the gas molecules and the walls, of the film.
In the case of meteorological balloons it is well known that loss of lift due
to permeation. in flight is so small as to be negligible (4). This is understandable
since as the balloon rises into regions of. low temperature both the solubility and
the kinetic energy of the gas are greatly decreased and the porosity of the film
itself is markedly decreased due to. stretching and orientation of the polymeric
structure of the membrane. But, although it is generally conceded that permea-
tion is a negligible factor during actual flight, it is operationally desirable to
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_J _A -
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know how much free lift would be lost to permeation, by a balloon inflated to
flight dimensions'and allowed to stand at room temperature for a period of time
prior to launching. With a knowledge of the diffusion rate at room temperature
of a balloon carrying a specified payload, and free lift to attain a desired ascen-
sional rate, the free lift could be increased to compensate for future loss in
cases where it is desirable or necessary to delay the launching of an inflated
balloon. With this in view, an experiment was conducted whereby loss of lift
due to permeation was measured, over a period of time, for J-100 balloons car-
rying payloads of 1, 2, 3, 4, and 6 pounds.
The procedure for the experiment was as follows:
Several J-100 balloons with 1, 2, 3, 4, and 6, lb. loads attached
were. f ted with. hydrogen to a point where the load was just balanced in mid-
air. The balloons were checked at intervals of ten minutes and ballast was
removed to restore the balkftce when lift was lost. The removed ballast was
weiglt'and recorded as grams of lift lost. This procedure was continued for
several houra,with the following results:
TA L 19.) LOSS' 0F' LIFT 'C15 TO P ABI ,7'Z'Y 3-100 VI iITE BALLC$b S
Payload Grams. of lift lost (10 minute intervals) 20-`C
Avg. Loss (gms.)
per hour
1 lb. 0.6 1.6 2.6 3.0 3.2 1.7 0.0 117 2.0 2.2 2.2 2.2 2.0 11.4
2 lb. 0.9 3.7 2.3 3.3 2.-J 2.7 2.6 3.3 2.6 6.3 *6.3 2.5 2.'7 17.5
3 lb. }.9 3.1 4.,6 4.6 3.8 4.8 5.0 5.3 4.4 4;4 4.4 5.3 5.3 25.8
4 lb. 0.0 5.9 5.7 5.7 7.4 4.6 5.9 5.9 7.2 7.2 5.1 6.8 7.0 33.0
6 lb. 0.0 0.0 7.3 7.3 9.2 9.9 8.8 12.3 8.1 8.5 10.F 11.4 10.2 48.4
It, can be seen from Table 12, that the loss of lift in the first ten minutes is very
Small regardless of the load the balloon is-carrying. We feel that this effect is
due to two factors.
1.) During inflation the gas is cooled by adiabatic expansion and takes
time to reach equilibrium with room temperature..
2.) There is a short build-up period during which the f.lm is not
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saturated with the dissolving gas. Once the proper concentration gradient is
built up, the gas will diffuse through the film at a fairly constant rate.
The discrepancy in the amount of lift lost between 10 minute intervals is
probably due to minor disturbances in the air caused by slight updrafts or down-
drafts in the area where the experiment was conducted. However, since these
conditions are similar to those encountered in the field, it is believed that the
average loss of lift as determined by the experiment is representative of the
actual state of affairs regarding the practical relationship between diffusion. and
free-lift.
RUBBER 0.03! CM__
t
10 20 30 40 50
TEMPERATURE - 'C
Relation between permeability to hydrogen
and temperature.
For the sake of convenience in operational use, a graph has been prepared
wherein loss of lift in grams per hour has been plotted as a function of gross lift.
L
(See figure- &.-)
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U
0
Ln
--- Irtt-
4 1i
F-i
1- -T- - -
t-
I ~ -
TT FT-T
.au/ ?stus - ssoZ I;Tri-aa.1A
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G.) ADIABATIC COOLING OF INFLATION GAS
Two attempts were made to measure the temperature of the inflation gas
versus room temperature immediately after inflation. The balloons used in the
experiment were inflated at a regulator pressure of 25-50 p.s.i.
Attempt #1. A thermometer was inserted through the valve of the
neck-closure into the balloon immediately after inflation. It was oberved that
the temperature inside the balloon was 1?C. below that of room temperature.
Attempt #2. Since it was felt that the thermometer used in Attempt
#1, was not sensitive enough to accurately measure the gas temperature, a,
second attempt was made using a radiosonde. This was accomplished by attach-
ing a long wire to the thermistar and inserting it into the balloon before inflat-
ing. Thus the temperature of the gas was measured while the balloon was being
inflated. Again a difference of only 1?C. was noted.
From these experiments it was concluded that variation in lift due to
adiabatic cooling of the gas was not a large factor in determining free-lift in the
case of a J-100 balloon.
H.) CONCLUSION
It is concluded from the foregoing ground and flight test data that the
characteristics of the J-100 and J9-10-300 gram balloons are.
1. Burst Diameter:
a.) Ground burst diameters are somewhat larger than flight test
burst diameters because of the effects of time and tempera-
tures. - (96 inches vs. 77-85 inches).
b.) Balloons having a high ascensional rate attain larger burst
diameters than balloons having a low ascensional rate.
(77 inches vs. 85 inches).
c.) Balloons carrying a payload of sufficient magnitude to pre
clude their ascending to high altitudes burst at a larger
:73
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diameter than balloons capable of ascending to high altitudes
because of the difference in temperatures.
d.) Balloons can be stored for a period of 12 to 15 months with-
out the necessity of pre-heating.
2. Burst Altitude:
a.) In accordance with the gas laws, balloons with light payloads
ascend to higher altitudes than those with heavy payloads.
However, because of the relationship between time, temper-
ature and burst diameter, balloons with a given payload and
low free-lift will reach approximately the same altitude as
a similar balloon with the same payload and high free-lift.
The altitudes attained by the balloons under consideration
range from:
(1) 23, 000 feet with a 6 lb. payload to 40, 000 feet with
a 21b'. payload using J-100 balloons.
(2) 45, 000 feet with a 10 lb. payload to 58, 000 feet with
a 5 lb. payload using J9-10-300 balloons.
The presence of clouds does not affect the burst altitudes
attained by J-100 balloons.
c.) J-100 balloons flown at night reach the same altitude as those
flown during the day.
3. Ascensional Rate:
It has been shown that the ascensional rate of meteorological
balloons is proportional to (Free Lift) 1/2
(Gross Lift) 1/3
and that for a J-100 balloon the theoretical rate of rise is
equal to 340 (Free Lift) 1/2 feet per minute and for a
(Gross Lift)1 / 3
J9-10-300 balloon the theoretical rate of rise is equal to 3*6
44-
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A LOO FAR -6L0-
(Free Lift) 1/2 feet per minute. &S-oo FeR 1010 Pg)fId1#o
(Gross Lift) 1/3
b.) Because of certain uncontrollable variables in the nature of
the fluid and the body in motion, it was found that the above
formulae are only accurate to within 10% of all the actual
rate of rise, therefore
c.) reliance must be based on experimental data if greater
accuracy is desired.
d.) Night flights rise more slowly than day flights.
e.) Early morning flights rise more slowly than afternoon,
flights.
f.) J-100 balloons flown under conditions of overcast skies have
the same average ascensional rate as those flown in clear
weather.
g.) Aged balloons have the same ascent' rate as fresh balloons.
4. Permeability:
a.) Permeability of a gas through a neoprene membrane is a
solubility phenomenon.
b.) The rate of permeability is directly proportional to temper-
ature, surface area and pressure difference and inversely
proportional to the thickness of the film.
c.) Because of the rapid decrease in temperature during flight,
the loss of lift due to diffusion during flight is very small,
becoming negligible at high altitudes.
d.) Because of a lag period, balloons inflated to flight dimen-
sions and held at ground level will not lose any lift due to
diffusion in the first ten minutes. However,
e.) if balloons are inflated and held at room temperature for an
extended period of time before launching they will lose from
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11.4 grams of lift per hour for a 2 lb, load to 48 grams of lift per hour
for a 6 lb, load. The rate of diffusion increases as the load is in-
creased because the film is thinner with the heavier loads.
5.
Adiabatic cooling of inflation gas
a.)
If balloons are inflated at a regulator pressure of 25-50 p.s.i. there
will be no loss of lift due to adiabatic cooling of inflation gas.
6.
Uniformity of performance
The data obtained from the flight test program indicates that the average
range in burst altitude for the J-100 balloons is 5,582 feet and the average
standard deviation is 2,610 feet.
For the J9-10-300 Balloons, the average range is 7,400 feet and the
average standard deviation is 3,610 feet.
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 Sanitized Copy Approved for Release 2011/05/03: CIA-RDP78-03639A000500040001-5
DI$PFRSION ANALYSIS
Payload (Lbs..)
free Lift (Grams
NolFli&hts
Range
Standard
Devi ton
2
50
4
5036
2450
2
100
5
9320
4050
2
200
5
7090
3020
2
350
5
3652
1570
2
500
5
3631
1560
3
50
5
8366
3600
3
100
5
7369
3170
3
200
5
8622
3710
3
350
4
6772
3300
3
500
5
8385
3650
4
200
5
10905
4700
4
500
3
4877
2890
6
200
2
2733
2420
5.75
620
3
3314
1960
3 light clouds
200
2
400
358
3 heavy clouds
200
5
4786
2060
3 night flights
200
10
5850
1900
3 cloudy night
200
3
761
450
3 preheated
200
8
2890
Average
5582
2610
Average Range =
5,582 feet
Average Standard Deviation = 2,610 feet
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 Sanitized Copy Approved for Release 2011/05/03: CIA-RDP78-03639A000500040001-5
DISPERSION ANALYSIS
J9-10-300 Balloons
Payload (Lb-se)
Free Lift (Gramml
No.F11 is
Rar3ge_
Standard
Deviation
5
300
4
4033
1960
5
1000
4
12979
6300
10
300
4
10020
4860
10
700
4
2352
111+0
10
1000
4
77%6
3750
Average
7400
3610
Average Range = 7,400 feet
Average Standard Deviation = 3,610 feet
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 Sanitized Copy Approved for Release 2011/05/03: CIA-RDP78-03639A000500040001-5
References:
1.) E. Habib, DA36-039-SC-82. Dewey & Almy Chemical Co.
2.) Dewey & Almy Chemical Co., DA36-039-SC-15463, M. Burgess.
3.) W. H. Lewis, L. Squires, G. Broughton "Industrial chemistry of col-
loidal and amorphous materials" Macmillian, New York (1949).
4.) H. T. Mastenbrook, "Neoprene Carrier Balloons" Naval Research
Laboratory, 17 Jan. 1951.
5.) Othmer and Frohlick,. "Correlating permeability constants of gases
through plastic membranes"", Polotechnic Institute, Brooklyn, New York
6.) Sager and Sucher, "Permeability of Neoprene to Gases", Nat'l Bureau
of Standards, Vol. 22, Jan. 1939.
7.) Barford at als "High-Altitude Free Balloon Flying", Imperial College
of Science and Technology, "" London. 6-12-54.
8.) H. Landers, M. Stipple "Local Rate of Ascent of the Thirty Gram Bal -
loon", A D No. 72988 Astia.
9.) F. W. Billmeyer, Jr., Textbook of "Polymer Chemistry", University
of Delaware and Polychemical Department, E. I. DuPont de Nemours
& Co., Inc.
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 Sanitized Copy Approved for Release 2011/05/03: CIA-RDP78-03639A000500040001-5
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