Chapter 2
BLAST AND SHOCK
The blast-and-shock program was designed to document information on shock parameters
in the propagation of the blast wave incident on and through the media of air, ground, and
water.
The isolation of the EPG allowed experiments on the effects produced by test de-
vices whose yields were in the megaton range. Only limited blast measurementat long
ranges had been made for Ivy Mike, which was the first megaton device detonated by the
United States. In a sense, the program was an extension of the Operation Ivy experiments;
additional experiments were needed to confirm, explain, or supplement the Ivy data.
A considerable quantity cf worthwhile data was obtained from Castie participation.
Despite uncertain yields and shot delays, the program was able to adaptitself to these
changing situations and achieve most of the objectives which were originally conceived.
2.1
OBJECTIVES
After Ivy, certain general objectives were defined for blast programs on future full-
scale tests at the EPG; it was on these requirements that the Castle program was based.
It was determined that free-air measurements should be made on devices with vields
greater than 540 kt to check the basic free-air curve. Surface measurements were needed from high-yield detonations to validate the use of height-of-burst curves and the
scaling relations in such yield ranges. Of great importance was the documentation of
adequate dynamic-pressure measurements, to increase the knowledge of this parameter
in itself as well as its relation to damage. More information was needed on the effects
on the blast wave as it is propagated through a nonhomogeneous atmosphere. It wag expected that refraction might also be noticed at distant ranges along the ground, because
such effects had been observed for the Ivy Mike shot. Considerably more information
was desired on blast effects over and through the water. Little data was available to
define shock propagation in very-shallow water or describe the water shoc!: produced by
nuclear detonation over deep water. It was also hoped to obtain data on the transmission
through the water via the sound fixing and ranging (SOFAR) channel as well as the outline
and activity of the surface water waves.
The Castle shcts were al! developmental devices, so that the military-effect programs
hac to be fitted to available yields, heights-of-burst, and shot geometry. In all cases,
the height-of-burst was essentially zero; that is, surface bursts on land, water, or ihe
ato! rim.
From these general objectives, then, the following specific objectives were evolved:
(1) determine air-blast overpressures as a function of altitude and time at relatively
short distances above high-yield surface detonations; (2) obtain data on the occurrence
of a precursor from high-yield surface detonations; (3) determine the time characteristics
of air-blast overpressure as a function of distance from surface zero for high-yield weap-
ons, in order to confirm the validity of scaling laws; (4) check the theoretical relationship
between dynamic pressure and overpressure and evaluate dynamic pressure as a damage parameter; (5) obtain information on the pressure-time history of underwater shock
in shallow water for high-yield surface detonations; (6) determine the transmiasion in