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A pyrotechnic fastener (also called an explosive bolt, or pyro, within context) is a fastener, usually a nut or bolt, that incorporates a pyrotechnic charge that can be initiated by a remote command. A fastener is a Hardware device that mechanically joins or affixes two or more objects together An explosive material is a material that either is chemically or otherwise Energetically unstable or produces a sudden expansion of the material usually accompanied Explosive charges embedded within the bolts are typically activated by an electric current, and the charge instantly breaks the bolt into two or three pieces. The bolt is typically scored around its circumference at the point(s) where the severance should occur. The circumference is the distance around a closed Curve. Circumference is a kind of Perimeter. Upon detonation a select part of the fastener rapidly disassembles without producing any shrapnel or fragments, freeing the mated units from each other. They are often used in space applications to ensure separation between rocket stages, since they are lighter and far more reliable than mechanical latches. A latch (called sneck in Northern England is a type of mechanical fastener that is used to join two (or more objects or surfaces together while allowing for the regular or

Often the term "explosive bolt" is used to refer to pyrotechnic fasteners in general. For example it is often stated that the Space Shuttle is held to the launch pad with explosive bolts but it is actually the large "frangible nuts" that each contain two pyrotechnic charges that split the nut into two pieces. NASA 's Space Shuttle, officially called the Space Transportation System ( STS) is the Spacecraft currently used by the United States The Frangible nut, commonly confused with an Explosive bolt, is a component used in many industries but most commonly by NASA to sever mechanical connections including

For the safety and reliability reasons, exploding bridgewire detonators and slapper detonators are frequently used in aerospace technology in place of classical blasting caps. The exploding-bridgewire detonator ( EBW, also known as exploding wire detonator) was invented by Luis Alvarez and Lawrence Johnson for the A slapper detonator is a relatively recent kind of a Detonator developed in Lawrence Livermore National Laboratory. A blasting cap is a small Explosive device generally used to detonate a larger more powerful Explosive such as Dynamite.

More recent developments have utilized pulsed laser diodes to detonate initiators through fiber-optic cables which subsequently fire the main charge. A laser diode is a Laser where the active medium is a Semiconductor similar to that found in a Light-emitting diode. A pyrotechnic initiator (also initiator or igniter) is a device containing a Pyrotechnic composition used primarily to ignite other more difficult to ignite An optical fiber cable is a Cable containing one or more Optical fibers The optical fiber elements are typically individually coated with plastic layers and contained

Gas generators are close cousins of pyrotechnic fasteners. A gas generator usually refers to a Propellant mixture often similar to a Solid rocket propellant that burns to produce large volumes of Gas. They are used to generate large amounts of gas, eg. for turbopumps, to inflate balloons especially airbags, to eject parachutes, and for other such applications.

Compositions used

Various pyrotechnic compositions can be used, depending on the desired burn rate and required amount of energy and volume of gas produced. Some materials, eg. RDX, sublimate in vacuum, which limits their usefulness in aerospace applications. Cyclotrimethylenetrinitramine, also known as RDX, cyclonite, hexogen, and T4, is an Explosive Nitroamine widely used Composition with the character of bipropellants and flash powders are often used. A bipropellant rocket engine is a Rocket engine that uses two propellants (very often liquid propellants) which are kept separately prior to reacting to form a hot Flash powder is a Pyrotechnic composition, a mixture of Oxidizer and metallic Fuel which burns quickly and if confined will produce a loud report

Standard pyrotechnic mixtures used by NASA

External links

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