Rocket Parachute Size Calculator/fr

Description
Ce calculateur détermine la taille du parachute nécessaire pour atteindre le taux de descente souhaité en fonction des paramètres du parachute.

Le taux de descente souhaité dépend de vos besoins. En règle générale, le parachute principal devrait ralentir la fusée à environ $$6.1\,m/s\,(20\,f/s)$$ tandis que le drone devrait permettre au parachute de descendre beaucoup plus rapidement $$18.3\,m/s\,(60\,f/s)$$ - $$21.3\,m/s\,(70\,f/s)$$. L'éditeur dispose de préréglages pour ceux-ci, la valeur pour le parachute de freinage se situant au milieu de la plage. Vous pouvez définir un taux de descente personnalisé en fonction de vos besoins.

A key value for determining the descent rate is the coefficient of drag ($$C_D$$). The exact value of this will depend on a variety of factors including the shape of the parachute. Presets are provided for parachutes cut from a flat piece of material (round, square, hexagonal) such as those provided by many kits, and for a true dome shape. Your parachute manufacturer may provide a better value for this coefficient.

Usage



 * 1) There are several ways to invoke the command:
 * 2) * Press the button.
 * 3) * Select the option from the menu.
 * 4) Enter the weight of your rocket and parameters for your parachute.

Calculation
Parachute size is determined by the mass of the rocket, desired descent rate, and drag characteristics of the parachute. The calculation is a two step process. First the area of the parachute is calculated:


 * $$A = { 2mg \over { \rho v_T^2 C_D }}$$

where


 * $$m = $$ the mass of the rocket
 * $$v_T = $$ desired terminal velocity
 * $$C_D = $$ drag coefficient of the parachute
 * $$\rho = 1.22$$ air density, average at sea level in $$kg/m^3$$ at $$15C$$
 * $$g = 9.807$$ acceleration due to gravity in $$m/s^2$$

The diameter is then calculated from the surface area based on the shape.

For hexagonal parachutes:


 * $$D = \sqrt{ 2A \over sqrt{3}}$$

For square parachutes, the diameter is the length of each side


 * $$D = \sqrt{A}$$

For all other parachutes, the shape is assumed to be circular


 * $$D = \sqrt{ 4A \over \pi }$$

Units
Calculations are done using metric units, but will display in your preferred units. Values can also be entered using any supported units by including the units with the value (eg 5 oz, or 23.2 g)