The principal blast effects are crushing due to overpressure and the change in steady
state aerodynamic conditions due to the material velocity. The latter is similar in nature
to the sharp~edged gusts enountered in the normal atmosphere. These changes are influenced by bending of the structure and displacement of the entire aircraft.
For Castle, analytical and experimental investigation established the critical overpressure of the B-36 as 0.8 psi, and of the B-47 as 1.0 psi. The analysis of gust loading
established the B-36 horizontal stabilizer as the critical component. Since the B-47 experiment was primarily designed to investigate thermal effects, the gust-load investigation was performed only to establish the safety of the aircraft for the thermal input to be
obtained.
Two basic problems were involved in the operation of the aircraft: the flying of the
aircraft to a point in space at a given time, and the accurate determination of the actual
TABLE 6.1
DESIRED AND ACTUAL POSITIONS AT TIME ZERO AND TIME OF
SHOCK ARRIVAL
Shot 3 data anuaable because of iow yield.
All B-36 data celoulated from radar soope photos
except for Shot 6, which ts Raydist data. B-47 data obtained from ship's instrumentation for
Shota 4 and 6 and from Raydist data for Shots 1 and 2. Ranges in thousands o* feet.
Shot
Horizontal Ranges
.
At Time-zero
At Shock-arrival
Desired
Actual
Desired
Actual
1: B-36
B-47
50.0
48.0
50.8
50.9
18.7
121 0
2; 3-36
B-47
50.0
§9.0
§1.7
TE.8
4: B-36
B~4?
50.0
42.2
5. B-36
8: B-36
B-47
B-47*
Shock-Arrival Position
Slant
Actual
Range
Altitude
115
137.5
18.8
141.9
33.0
38.0
18.8
132.0
17.9
192.5
86.2
198.7
37.0
35.0
$0.8
542
78.5
119.4
81.6
140.0
89.6
144.3
$7.1
35.0
339.5
40.6
65.5
69.7
80.4
40.0
121.4
31.8
122.0
29.5
90.3
84.6
86.0
84.0
92.1
91.0
33.0
35.0
_~
_
_
-
—
_
_
* 8-47 eborted Shot 5 because of fuel leak.
flight path during the thermal and blast phases of the detonation. Positioning was in _
general performed by aircraft instrumentation, and tracking by a combination of aircraft
instrumentation and a Raydist Radio Navigation System. For safety reasons, positioning
was based on the predicted maximum-possible yield of the device.
For both experiments, danger-region diagrams were plotted in terms of horizontal
range and altitude, upon which the effects parameters discussed previously were plotted
simultaneously in order to show the boundaries of regions within which aircraft damage
would result. These diagrams were used on each shot under a given set of conditions of
yield, aircraft velocity, and aircraft configuration, to establish a position in space which
would give the desired input without endangering the aircraft. Positioning data is summarized in Table 6.1.
Thermal instrumentation was installed to define radiant exposure, irradiance, and
the temperature rise on wing, fuselage, stablizer, and elevator. In addition, straingage bridges were installed in the left wing and stablizer of the B-47 to obtain information on the mechanical effects of the thermal input.
Free-stream overpressure and
pressures on the underside of various surfaces were measured. Blast-response data
were in terms of strain-gage measurements of the wing, fuselage, and stabilizer; linear
1