iming for each photo was possibly
inaccurate and the scale factors my
e been erronecus, since these were not
taken in a carefully plamed manner acd the persistent spectacle bad oot been
predicted.
Further, and possibly more important, is the geometric error in as-
soming the glowing blast wave pictured was in a wertical plane through the burst
point.
A successive aporozimatioa solution for the correct geametry does not
appear to be justified in view of the other uncertainties in the measurements.
Finally, if shock speeds were actually only half the scaled walues, as the
photos indicate, the rough agreement between shock arrival-time calculations sod
observatious and incidence angles at French Frigate Shoals could be negated.
Qo the USS Barer, many faint pops and bangs were audible from Orange
about 10 to 15 mimites after zero time.
These are beliewed to be similar
to noises recorded at Eniwetok from Bikini megaton-class shots.
Shock rays
from the burst originating at high elevation angles abowe the horizon suffer
energy reduction by spherical expansion at first and become nearly acoustic.
Then, as they travel to extreme altitudes (60 to &O miles), they again become sbock rays in the wery-low ambient atmospheric pressure, travel super-
sonically (to Mach 2 to 3), and are thus turned back to groumd by refraction,
where they strike at high incidence angles ,!°
6.2
INSTROMENTATION
6.2.1
Instrument Description
The microbarograph instrumentation system was first used during Operation
Dpshot/Knothole.
Since this systes, designated 3-PEM-2, has been ‘described in
detail in sc-2990(m2)*? and WT-9003, 10 it is described only briefly in this
report.
°
The change of pressure resulting from ouclear detonation is sensed,
together with undesirable high~ and low-frequency noise, in a cross-shaped
hose array leading into a Wiancko sensing head.
tion of the system is diagramed fn Fig. 6.8.
The general theory of opera-
‘The hose array has an upper