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Separation events are typically released by pyrotechnic charges up to altitudes of about 20,000 feet. Above this altitude, when BP combustion is less reliable. However, for relatively low altitudes, pyrotechnics are far and away the most widely used separation mechanism.
Pyrotechnic
See "Ejection Charge" for more details. Pyrotechnics are usually used for separation because of their reliability.
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- Messy
- Leaves thick, dusty, smelly residue inside the rocket
- Requires thermal protection for parachutes, webbing, payloads, avionics, and other materialsinternal components
- adds weight and reduces available volume for parachutes and critical recovery components
Motor Ejection
Most COTS solid rocket motors have an ejection charge in the top of the motor casing. It is ignited after a delay grain between the rocket motor and the ejection charge is burned through. See below:
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- internal components
Ejection Charge (electronically initiated)
Ejection charges can also be initiated by electronics. Typically a charge is set up as follows:
It is important to consider the safety of the altimeters when using this method. Ejection gases can damage altimeters from the heat, and the sudden pressure difference can damage the barometer. This is also a highly reliable method, but it is more complex because the altimeter, its connection to the charge, and the integration of the system must be checked meticulously prior to launching the rocket. This method is almost always used for dual deployment scenarios.
Motor Ejection
Most COTS solid rocket motors have an ejection charge in the top of the motor casing. It is ignited after a delay grain between the rocket motor and the ejection charge is burned through. See below:
This is the most reliable method of pyrotechnic separation, and is common for all rockets from 1/4A to L motors.
CO2 Ejection
Small, pressurized canisters of CO2 can be used to pressurize a tube section in the place of pyrotechnics. A COTS example is the Perigrine. These use a small, well-packed pyrogen to release compressed CO2, which in turn pressurizes the section to be separated. This system has the benefit of leaving less residue than a pyrotechnic-only system while still having the same initiation method already used for ejection charges. This is typically used for high-altitude flights (above 20k feet).
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