1214 
come. The British [17], for example, have developed 
such a transponder system, and a similar system has 
been developed for the Navy [22] by the National 
Bureau of Standards. Wind measurements have been 
made by the British to ranges of 100 miles and alti- 
tudes of 70,000 ft, the latter limitation being that of 
the balloon. Although no accuracies have been quoted, 
an analysis of the basic system suggests that the errors 
in measurement of wind should be less than those of 
the radiosonde-radiowind system. 
Although measurement of wind alone is an important 
function, the value of a sounding is increased if the 
temperature, pressure, and relative humidity are also 
known. In the British [17] system, the incorporation 
of meteorological sensing elements into the flight equip- 
ment in such a manner that the pulses are used as the 
telemetermg channel is now contemplated. Although 
no entirely satisfactory system has so far been described, 
there is no basic reason why such a system cannot be 
developed. The author is of the opinion that an all- 
electronic radarsonde system with meteorological com- 
puters will represent another major step forward in 
the radiosonde art. 
The radiosonde-radiowind system described previ- 
ously is capable of modification to an equivalent radar- 
sonde system by the addition of a ranging unit. Whether 
such a modification is desirable, or whether a complete 
redesign starting with a basic radar set is necessary, 
will be determined to a great extent by economic 
rather than technical difficulties. 
METEOROLOGICAL BALLOONS 
A full description of meteorological balloons and 
their uses, from the time of the first balloon in 1783 
until 1935, has been given by Reger [19]. In these 
early years, balloons were fabricated from a variety of 
materials, such as oiled silk, paper, goldbeater’s skin, 
and sheet rubber. The use of rubber latex was restricted 
to the smaller balloon sizes, such as pilot balloons. 
With the advent of the modern radiosonde, tre- 
mendous strides have been made in the manufacture 
of large balloons (850-10,000 ¢). Two methods have 
been developed for fabricating these large balloons. 
In the first method, a rubber gel is formed by introduc- 
ing latex into a hollow spherical mold immersed in 
hot water, and then automatically rotating it im such 
a way that the latex is deposited rather uniformly on 
the interior wall of the mold. In the second method, a 
suitable form made of plastic or aluminum is dipped 
into a coagulant and then into the latex. The latex 
solidifies and forms a gel on the mold. In both methods 
the gel is inflated while still wet and soft, and then 
carefully dried, deflated, and cured. From a wet gel 
pulled off a 20-in. dipping mold, it is possible to pro- 
duce a finished balloon 60 in. in diameter that in turn 
can be inflated to a diameter in excess of 25 ft before 
bursting. It appears from the rather sparse data avail- 
able that balloons made from a hollow mold are some- 
what stiffer than those produced by the dipping process. 
Recently, plastic materials such as polyethylene have 
been successfully fabricated into balloons. It is still 
METEOROLOGICAL INSTRUMENTS 
too early, however, to evaluate this balloon develop- 
ment properly. 
Altitude Performance. The present standard mete- 
orological balloon used to carry radiosondes aloft is 
made of a synthetic rubber called neoprene. The exact 
ingredients and the technique of fabrication, including 
curing times and temperatures, are considered trade 
secrets by the balloon manufacturers. Therefore, it is 
not possible to correlate these important factors with 
such balloon parameters as ascensional rates and burst- 
ing altitudes. It can be stated, however, that the bal- 
loons now supplied in this country for radiosonde work 
are of remarkable quality. The average daytime per- 
formance of these balloons, based on several hundred 
flights, can be summarized as follows: 
Weight of balloon 1000-1400 g 
Pay load 1700 g 
Free lift 1000-1500 ¢ 
Amount of Hs used 120 ft 
Approximate initial diameter 65 ft 
Approximate diameter at 90,000 ft 25 ft 
Unstrained thickness 0.004 in. 
Thickness at burst 0.0002 in. 
1000 (+100 ft min) 
(—50 ft min~) 
90,000 ft (80% of the time) 
100,000 ft (37% of the time) 
Ascensional rate 
Altitude attained 
Very large balloons, fabricated of synthetic rubber, 
have reached altitudes of from 120,000 to 140,000 ft 
during the daytime. These experimental balloons, car- 
rying a pay load of about 2000 g, weigh approximately 
10,000 g and require nearly 700 ft? of gas. The balloons 
are only partially inflated at the ground and become 
fully extended at about 30,000 ft. The rate of climb is 
about 800 ft min to 30,000 ft, and then 1100 ft min 
to bursting altitude. However, the performance of these 
few experimental balloons has been extremely erratic. 
If fabrication techniques can be developed that will 
yield balloons of uniform thickness and quality, it is 
estimated that altitudes of about 150,000 ft can be 
attained. Balloons of such altitude performance will 
open up new frontiers for upper-atmospheric research. 
Temperature Effects. In the course of testing balloons 
for performance, it has been observed that differences 
in temperature between the inside and outside of the 
balloons for daytime flights may reach values as high 
as 40C at 50,000 ft, and remain sensibly constant to 
the bursting altitude. At night, the temperature within 
the balloon remains about 1C warmer than the outside 
up to altitudes of 50,000 ft. The temperature gradient 
then reverses, the inside becoming progressively cooler 
and reaching temperature differences of about 10C at 
altitudes around 90,000 ft. Natural-rubber balloons 
were used for these nighttime flights. 
Although the daytime performance of the neoprene 
balloons can be considered excellent as far as altitude 
is concerned, the nighttime performance of the syn- 
thetie balloons leaves much to be desired. The average 
height that can be expected is from about 55,000 to 
60,000 ft; this limitation is due principally to the 
freezing of the balloon. By using natural rubber latex, 
