surface bursts to be
bef
r
0.665 - 0.789 =
e
,
P
where h is turnower altitode in feet, R is distance in feet from shot to recorder, t is recorded arrival tize in secouls, and ‘> is the ray characteristic
welocity in feet per secood.
By assuming a straight-line 7o-degree ray below
Teak beight of burst, a wirtua] ground source has been estimated in Fig. 6.5
for use in the equation at R = 2,427,000 + 250,200 cos 72” = 2,904,000 feet.
As ooted in Section 6.1.3, the acoustic wertical arrival would have been 235
seconds near Teak ground zero.
Thus, along the Te-degree ray, travel cine
would be 234/sin Je” = 266 seconds, so an arrival at FFS fros the virtual
source would be (see Table 6.2) approximately t= 5+ 246 = 1171 secomis.
Porther,
b = (2,905, 000) [ 0.265 - 0.789 metas | = 94,000 feet MSL.
That this characteristic welocity is higher than sound speed (Table 6.7) for
this turnover level is not surprising, considering the many approximations made.
Mie
25Q,200/ sie 72
2,827,000°
250, 200 cos 72°
VIRTUAL BURST POINT
FRENCH FRIGATE SHOALS
Fig. 6.5--Teak shock ray geometry.
As a further projection, vith the concest of rays traveling to 10° foot
altitudes, acoustic ray calculations shown in Fiz. 6.6 have been made through