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Burn rate is an important parameter, especially in propellants, because it determines the rate at which exhaust gases are generated from the burning propellant, which decides the flow rate through the nozzle. The thrust generated in the rocket of a missile depends on this flow rate.
Erosive burning (high-velocity flow moving past the propellant). Initial temperature of propellant. In summary, however, most formulations have a burn rate between 1–3 mm/s at STP and 6–12 mm/s at 68 atm. The burn characteristics (such as linear burn rate) are often determined prior to rocket motor firing using a strand burner test. This ...
Since the single propellant grain is so large (most smokeless powders have grain sizes around 1 mm, but a caseless grain will be perhaps 7 mm diameter and 15 mm long), the relative burn rate must be much higher. To reach this rate of burning, caseless propellants often use moderated explosives, such as RDX.
Propellant combustion occurs inside the motor casing, which must contain the pressures developed. Solid rockets typically have higher thrust, less specific impulse, shorter burn times, and a higher mass than liquid rockets, and additionally cannot be stopped once lit.
The specific surface area of the propellant influences the speed of burning, and the size and shape of the particles determine the specific surface area. By manipulation of the shape it is possible to influence the burning rate and hence the rate at which pressure builds during combustion. Smokeless powder burns only on the surfaces of the pieces.
Many different sugars are used as the fuel for rocket candy. The most common fuel is typically sucrose, however, glucose and fructose are sometimes used. As an alternative, sorbitol, a sugar alcohol commonly used as a sweetener in food, produces a propellant with a slower burn rate and is less brittle when made into propellant grains. [5]
For liquid-propellant rockets, four different ways of powering the injection of the propellant into the chamber are in common use. [11] Fuel and oxidizer must be pumped into the combustion chamber against the pressure of the hot gasses being burned, and engine power is limited by the rate at which propellant can be pumped into the combustion ...
A Crawford burner is a device used to test burn rate (chemistry) of solid propellants. It is also known as a strand burner. A Crawford burner consists of a small pressure vessel in which a thin bar of propellant to be tested is mounted on a stand. The bar is coated with an external coating so that burning cross-sectional surface is restricted.