High Explosive Corner Turning Performance and the LANL Mushroom Test Page: 3 of 5
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EXPERIMENTAL DETAILS
Figure 1 shows a scale drawing of the Mush-
room test shot assembly. The test is named
for its distinctive geometry-a 25.4 mm diameter
pressed hemispherical "cap" of test material, ini-
tiated by a 6 mm-diameter x 24 mm-long "stem"
composed of four PBX9407 (94 wt.% RDX, 6 wt.%
binder) pellets. The stem's purpose is to provide
a strong and repeatable pressure input irrespec-
tive of the reproducibility of the Reynolds RP-2
detonator. Its 6 mm diameter was chosen by trial
and error, using PBX9504 as the test explosive.
Alignment Marks Pedestal Alignment Marks
Camera
Slit
Explosive
Sample
- RP-2 Detonator
Base
-Spring
Detonator Leads
FIGURE 1. Scale drawing of the Mushroom Test
Samples are pressed directly to shape in a
hemispherical die. Since the final volume is fixed,
the sample density may be controlled simply by in-
serting the appropriate amount of mass. The bulk
density of the finished pieces is also measured by
immersion, as corner turning is quite sensitive to
this parameter.
The sample is epoxied at four spots around
the edges to a PMMA pedestal. The stem passes
through a hole in the pedestal and contacts the
equator of the test sample. The pedestal is epox-
ied to a PMMA base, which holds the detonator
and two 450 mirrors. The detonator and pellets
are spring-loaded against the test sample to ensure
good contact between the pieces. The assembly is
designed so that all pieces are automatically and
accurately located with respect to one another.Detonation breakout is observed with an
internal-slit rotating mirror streak camera. The
experiment is viewed directly and from two sides
via the mirrors. The image of the camera slit
spans the center of the hemisphere and its mir-
ror images to give a composite streak record. The
slit is precisely aligned by centering it between two
blackened scribe marks on the pedestal (Fig. 1),
which are visible in the mirror views. The sam-
ple surface is painted with aluminum fluosilicate
to enhance the light output upon breakout.
Figure 2 shows a sample (negative) streak cam-
era record. The two diagonal bands on top are
the detonation wave traveling through the stem,
as seen through the PMMA pedestal. Their ter-
mination indicates the entrance of the detonation
wave into the pellet, and provides the time ori-
gin used for the breakout data. The three images
on the bottom are detonation breakout and the
subsequent product light from the three views.E
5Distance
Shot# 15-2430
Wave
inside
stem
Wave
inside HE
Breakout
TLeft
Mirror
ViewCenter
(Direct)
ViewRight
Mirror
ViewFIGURE 2. Mushroom test dynamic streak record.
The test is fired cold (-55 C) to observe worst
case corner turning behavior. The shot is cooled
at 1 C/min using dry nitrogen, and is soaked at
temperature for 30 minutes. The styrofoam shot
box has a double-glass observation window, and
dry nitrogen is blown between the panes and also
over the top pane to prevent condensation.
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Hill, L. G.; Seitz, W. L.; Forest, C. A. & Harry, H. H. High Explosive Corner Turning Performance and the LANL Mushroom Test, report, September 1, 1997; New Mexico. (https://digital.library.unt.edu/ark:/67531/metadc695294/m1/3/: accessed July 17, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.