Lesson plan
Delay composition
Delay composition, also called delay charge or delay train, is a pyrotechnic composition, a sort of pyrotechnic initiator, a mixture of oxidizer and fuel that burns in a slow, constant rate that should not be significantly dependent on temperature and pressure. Delay compositions are used to introduce a delay into the firing train, e.g. to properly sequence firing of fireworks, to delay firing of ejection charges in e.g. model rockets, or to introduce a few seconds of time between triggering a hand grenade and its explosion. Typical delay times range between several milliseconds and several seconds. A popular delay charge is a tube of pressed black powder. The mechanical assembly prevents the outright detonation of the charge. While delay compositions are principally similar to other fuel-oxidizer compositions, larger grain sizes and less aggressively reacting chemicals are used. Many of the compositions generate little or no gas during burning. Typical materials used are: * Fuels: silicon, boron, manganese, tungsten, antimony, antimony trisulfide, zirconium, zirconium–nickel alloy, zinc, magnesium, etc. * Oxidizers: lead dioxide, iron oxides, barium chromate, lead chromate, tin(IV) oxide, bismuth(III) oxide, barium sulfate (for high-temperature compositions), potassium perchlorate (usually used in small amount together with other oxidizers), etc.…
Article summary
Delay composition, also called delay charge or delay train, is a pyrotechnic composition, a sort of pyrotechnic initiator, a mixture of oxidizer and fuel that burns in a slow, constant rate that should not be significantly dependent on temperature and pressure. Delay compositions are used to introduce a delay into the firing train, e.g. to properly sequence firing of fireworks, to delay firing of ejection charges in e.g. model rockets, or to introduce a few seconds of time between triggering a hand grenade and its explosion. Typical delay times range between several milliseconds and several seconds. A popular delay charge is a tube of pressed black powder. The mechanical assembly prevents the outright detonation of the charge. While delay compositions are principally similar to other fuel-oxidizer compositions, larger grain sizes and less aggressively reacting chemicals are used. Many of the compositions generate little or no gas during burning. Typical materials used are: * Fuels: silicon, boron, manganese, tungsten, antimony, antimony trisulfide, zirconium, zirconium–nickel alloy, zinc, magnesium, etc. * Oxidizers: lead dioxide, iron oxides, barium chromate, lead chromate, tin(IV) oxide, bismuth(III) oxide, barium sulfate (for high-temperature compositions), potassium perchlorate (usually used in small amount together with other oxidizers), etc.…
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Discussion questions
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- If two sources disagreed about one of these facts, what would you need in order to trust one over the other?
Bibliography
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