1082
evident on the pressure-time curve; Sendia'’s tine of arrival refers of course
ALi
to the pressure :.. in the “thermal shock .
Wigore 2 shows the peck pressure vs. distances over land and vater.
Here again the agreassnt with the theoretical predictions is conatéered ex-
cellent, both over land and water.
Hote the return of tho thermal curve |
to approach the ideal values near 8 yeti.
Purther, veyond 10,000 foet the
pressures are below ideal, indicating that the effect of ataoepheria inhom-
gmneity sets in somewhere beyond 19,000 to 15,000 feet.
Figur: 3 shows the positive duration vs. bcrisontal distances.
‘The
theoretical curves ara not exact; for simplicity, I have used here the posi-
tive duration of « free air curve with @ reflection factor of 2.
For a dca
at altitude, the cloencia positive duration should de more nearly like 1/2
the tonaage indicated here. On thecurves, the two close-in ideal surface
positive durations are, in fact, shorter than inéicated but at large dis-
tances for the positive durations become much longer then predicted.
This
is attributed to atucupherie inhcuogeneity setting in beyond 15,000 feet.
Hote also that the ponitive durations are considerably longer over lanl than
ovar water; this is again due to thermal effect andi precursor action, with
aoe reinforcenmt of the dDlast wave from thermal vadiatics.
BEST COPY AVAILABLE
3. MIKE chor
During bis visit last week, Lew Fussell reported thet the mora recent
fireball measurements are giving values of / like 268 from the Perry-Dastmn
filme, and 278 from the Engeht Rapntronics.
‘The fireball measurenents at
Ferry, which resulted in the firevell yield of 12 megatons, was based on data
whose
/ values vere more like 2773 now the Ingebl messuremengs will be large
decause the apparent wise of the fireball is measured by the tangent to the
fireball, end at theese close-in distances, the proper correction will reduce
Wa
geab
roELT ree
at
eB”
: