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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.
Burn rate (typically expressed in mm/s or in/s) is the sample length over time at a given pressure and temperature. For solid fuel propellant, the most common method of measuring burn rate is the Crawford Type Strand Burning Rate Bomb System [3] (also known as the Crawford Burner or Strand Burner), as described in MIL-STD-286C. [4]
The first powders were called "MR" for military rifle powder. In the 1920s these powders were improved and the name was changed to IMR. Various different powder are produced and are given numbers to distinguish them. The different types of powder typically have different burning rates.
This graph shows different pressure curves for powders with different burn rates. The leftmost graph is the same as the large graph above. The middle graph shows a powder with a 25% faster burn rate, and the rightmost graph shows a powder with a 20% slower burn rate. Energy is the ability to do work on an object. Work is force applied over a ...
red lead with silicon, burning at intermediate rate; lead(IV) oxide with silicon, burning at 5–6 cm/s; potassium permanganate with antimony, very slow; Manganese Delay Composition: manganese with lead chromate and barium chromate (lead chromate is the principal oxidizer, barium chromate acts as burning rate modifier, the more of it the slower ...
Military rifle propellant was manufactured in batches in a procedure taking about two weeks [7] from treating cotton linters with nitric acid, through curing the extruded grains to evaporate excess ether and alcohol, and finally coating the dried grains with DNT and graphite.
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. Larger pieces burn more slowly, and the burn rate is further controlled by flame-deterrent coatings that retard burning slightly.
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]