3.1 Armed. An ignition system
is armed when the output of a primary explosive, a sensitive pyrotechnic or
application of a firing stimulus can produce ignition of the munition
a. An ignition system employing an ignition safety
device with pyrotechnic train interruption (see 5.2.2) is considered armed
when the interrupter(s) position (or condition) is ineffective in
preventing propagation of the pyrotechnic train, given initiation of the
sensitive elements of the train, at a rate equal to or exceeding 0.5
percent at a confidence level of 95 percent.
b. An ignition system employing firing energy train
interruption (see 220.127.116.11) is considered armed when the interrupters’
position or condition is ineffective in preventing initiation of the first
element of the pyrotechnic train at a rate equal to or exceeding 0.5
percent at a confidence level of 95 percent.
c. An ignition system employing a non-interrupted
pyrotechnic train and a non-interrupted firing energy train (see 18.104.22.168)
is considered armed when the firing energy available for delivery to the
initiator equals or exceeds the initiator's maximum no-fire
3.2 Common mode failures. Multiple failures
that result from, or are caused by, seemingly unrelated failure(s) or an
adverse environment. Examples include the failure of two gates on a single
digital integrated circuit due to loss of the ground to the chip or failure
of two transistors due to exposure to a high temperature environment.
3.3 Enabling. The act
of removing or deactivating any safety feature, which prevents arming.
3.4 Environment. A
specific physical condition to which the ignition system may be exposed.
stimulus. A specific stimulus obtained from an environment.
3.6 Fail-safe design.
A characteristic of an ignition system and/or part thereof, including the
ignition safety device, designed to preclude ignition of the propulsion
system or hazard to personnel when safety features malfunction.
3.7 Firing Energy
Train. The path of all non-chemical energy leading to the first element
of a non-interrupted pyrotechnic train.
3.8 Firmware. The
combination of a hardware device and computer instructions or computer data
that reside as read only software on the hardware device. The software
cannot be readily modified under program control.
3.9 Igniter charge. A
source of heat and pressure that actually ignites the motor propellant.
3.10 Ignition safety
device (ISD). A device that is an integral part of the munition whose
purpose is to prevent an unintended functioning of the rocket or missile
motor through interruption of the pyrotechnic train, interruption of the
firing energy train, or control of the energy required to arm the ISD and
function the initiator.
3.11 Ignition system
(IS). The aggregate of devices in a weapon system, including those in
the munition, launcher and munition launch platform (e.g., fire control
system, armament control unit), which control the arming and firing signals
to cause the munition propulsion system to function.
3.12 Independent safety
feature. A safety feature is independent if its integrity is not
affected by the functioning or malfunctioning of the other safety
The component or components which convert the firing energy
resulting in initiation of the first explosive or pyrotechnic element, even
in the case of a distributed system where the energy conversion may occur at
some distance and in a physically different module from the explosive or
pyrotechnic element. The first explosive or pyrotechnic element of the
explosive train will always be considered as part of the initiator. Examples
of Initiators include but are not limited to:
Bridgewire (EBW) devices;
b. Semi-Conductor Bridge (SCB)
c. Laser diodes, the first component of the explosive
or pyrotechnic train, and the in between (transfer)
d. Exploding Foil Initiators (EFI) including the
bridge and explosive component;
firing energy train. A firing energy train with its elements physically
and functionally separated until arming to interrupt the firing energy path
and thus prevent ignition of the first element of a non-interrupted
pyrotechnic train in the event of unintended activation of any sensitive
element in the firing energy train (e.g., low voltage laser diodes).
pyrotechnic train. A pyrotechnic train (see 3.18) with elements of the
train physically and functionally separated until arming to interrupt the
firing path and thus prevent ignition of the motor propellant in the event
of unintended ignition of any sensitive element of the train.
no-fire stimulus (MNFS). The stimulus level at which the initiator
will not fire or unsafely degrade with a probability of .995 at a confidence
level of 95%. Stimulus refers to characteristic(s) such as current, rate of
change of current (di/dt), power, voltage, or energy which is (are) most
critical in defining the no-fire performance of the initiator.
materials. Those energetic materials or compounds which do not
ordinarily detonate in their intended function but rather burn or
deflagrate. Typical examples include boron potassium nitrate
(BKNO3), black powder, and many metal/oxidant combinations.
train. The deflagration train beginning with the first pyrotechnic
element and terminating in the munition propellant. For the purposes of this
standard, the term pyrotechnic train refers also to those trains
incorporating one or more detonating components.
feature. An element or combination of elements that prevents
unintentional arming or functioning.
3.20 Safety system
failure. A failure of an ignition system or ignition safety device to
prevent unintentional arming or functioning.
pyrotechnics. Sensitive pyrotechnics are used to initiate or ignite
other, less sensitive, materials in the pyrotechnic train. They are used in
primers or squibs of ignition systems and are sensitive to ESD, heat,
impact, or friction and undergo a rapid exothermic reaction upon
environmental. A component or series of components designed to detect
and respond to a specific