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distribution and testing panels, and 
the TINT for blowing off the warhead. 
In the midsection between the alcohol 
and oxygen tanks, two cameras are 
mounted for taking pictures at inter- 
vals on the way up. The cosmic-ray 
film-recording camera is mounted on 
one of the motor supports immediately 
below the oxygen tank. The spectro- 
graph is mounted in one of the fins and 
is provided with a fairing to maintain 
the necessary streamlining of the fin. 
At the extreme tail end of the missile 
are mounted the various antennas for 
telemetering, ionosphere, and emer- 
gency cut-off equipment. I should 
now like to discuss each of the various 
experiments at greater length. 
Cosmic Rays 
There are many cosmic-ray experi- 
ments that one can perform even in 
a rocket which spends only 4 or 5 
minutes above the atmosphere. Of 
all the possibilities we felt that two 
stood out above all others, namely: 
1, a determination of the nature of the 
primary radiation (heretofore the 
nature of the primaries could be 
inferred only from studies of the 
secondary or tertiary radiation within 
the atmosphere), and 2, a study of the 
fundamental reactions taking place 
as the primaries pass through the 
atmosphere. 
Until the advent of the rocket, cos- 
mic-ray experiments had been con- 
ducted in balloons up to an altitude 
of about 24 km., corresponding to an 
atmospheric pressure of 2 cm. of 
mercury. These experiments (13, 14) 
had determined the distribution of the 
total as well as the “‘hard’’ cosmic 
radiation through the atmosphere, and 
they indicated that even at pressures 
as low as 2 cm. of mercury the primary 
radiation had already reacted with air 
nuclei to produce a secondary radia- 
tion generally considered to be mesons. 
The V-—2 was capable of reaching the 
region of the primaries (up to this 
time generally considered to be pro- 
ANNUAL REPORT SMITHSONIAN INSTITUTION, 1948 
tons by most workers in the field (14, 
15) and also of passing through the 
very interesting region in which the 
ultranucleonic transformations, which 
result in meson production, take place. 
One of the latter was assumed to be 
the very important and fundamental 
proton-meson reaction about which 
very little is known, since it apparently 
occurs on earth only in the cosmic 
radiation at the top of the atmosphere. 
Four different cosmic-ray experi- 
ments have been successfully per- 
formed to date in four different flights 
(16, 17, 18, 20, 21).. At the present 
time three more experiments are in 
preparation for incorporation in flights 
during May and July 1947. The 
results of these experiments have given 
more insight into the nature of the 
cosmic radiation. The first two ex- 
periments established the fact that the 
greater portion of the primary radia- 
tion consists of “hard” particles (i. e., 
particles which will penetrate at least 
12-15 cm. of lead) and that about one 
out of every five such particles will 
produce a shower in 12 cm. of lead. 
In addition it was found that large 
showers were produced by the pri- 
maries in the rather considerable mass 
of material in the warhead which sur- 
rounded the counter telescope. On 
the basis of this information the third 
and fourth experiments were per- 
formed, which I should like to discuss 
in greater detail. 
The third experiment (18) consisted 
of two parts. In the first part a cosmic- 
ray telescope was arranged to test the 
penetrating properties of the incoming 
ionizing radiation. It was found that 
(at a zenith angle of 45°) about 60 
percent of the radiation was absorb- 
able in a large thickness of lead (14 
cm.). The other properties of the 
high-altitude radiation were again 
verified, i. e., the large numbers of 
warhead showers, and the showers 
under 14 cm. of lead (28 percent in 
this measurement). The second part 
of the experiment, conducted in the 
same flight, tested for penetration 
