MIL-DTL-23659F
APPENDIX A
design parameters should be well understood to predict the consequences of manufacturing
tolerances and aging.
A.7.6.4. Firing Properties.
a. The purpose of the firing properties tests is to establish required electrical initiation
characteristics of the ILI. The firing properties test establishes statistical characteristics that can
be used for selecting or verifying the following: the design's recommended all-fire voltage, the
maximum no-fire voltage, and the maximum allowable safe stimulus. These parameters can be
used for the evaluation of an ILI suitability for an application and/or in the establishment of
thresholds for safety critical states. For example, in MIL-STD-1316, ESADs containing firing
capacitor voltages above MNFV are considered armed, thus the determination of MNFV via the
firing properties test can be used to determine the arming point for evaluation of safe separation
requirements.
b. ILI that are capable of being detonated at potentials less than 500 volts cannot be used in
any non-interrupted energetics train application governed by the existing military safety
standards (MIL-STD-1316, MIL-STD-1901 or MIL-STD-1911). At a minimum, firing
characteristics established under this test must be used to establish compliance with this
requirement.
c. Various statistical type analyses have been prepared and are used in order to project
safety and reliability characteristics, for example: Bruceton, Neyer, Langlie and Probit Methods.
Statisticians have pointed out the fallacy of an inappropriate use of these various methods and
the extreme care necessary in their application.
d. Maximum No-Fire Voltage (MNFV) determination is important for use in safety
evaluations, see the example in paragraph A.7.6.4 a. Voltage is a commonly used parameter in
defining the test inputs in capacitive discharge firing system evaluations. Knowledge of voltage
potential effects can also be important for evaluating powered ESADs, whose electronics if
subverted by noise or electromagnetic radiation could develop a voltage on the high voltage
capacitor. The probability level established by this test was selected to correspond with the
probability typically used in the Hazards of Electromagnetics to Ordnance (HERO) community.
e. Maximum Acceptable Safe Stimulus (MASS) can be any stimulus that is unsafe such as
voltage, current, light, etc. MASS, for this test is also characterized as a voltage, and is
represented as the voltage on the firing capacitor at which the probability of initiation is 1 X 10-6.
f. While 12 hour temperature conditioning is specified for this, and several other tests, the
duration could be tailored to suit the test hardware. The intent is that the temperature of the test
item has stabilized at the test temperature, which often will require less time for small test items.
When determining temperature stabilization times, all the test hardware should be considered,
including the test item and, where necessary, firing unit components. The conditioning duration
and logic used for selecting less than 12 hours shall be documented. Effort shall be made to
assure that the ILI meets the temperature requirements at the moment it is functioned. This
requirement may be meet by employing a test methodology of conditioning to a temperature
more extreme than the requirement and monitoring the time needed to function the ILI.
Temperature monitoring is not required for ambient tests provided the device storage
temperature and test facility air temperature are within the specified acceptable range.
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