Estimation of Propellant Charge Weight.

d. Estimation of Propellant Charge Weight.

(1) Catapults and removers.

(a) The propellant charge weight in pounds, C, required for a catapult or remover may be estimated

using equation (31).

and where

F = propellant impetus

e = overall efficiency (use 0.10 as a representative figure for catapults and removers)

y = ratio of specific heats

g = acceleration due to gravity

m = propelled mass

m' = modified propelled mass

a = angle between direction of thrust and-horizontal

V = velocity at separation

S = stroke to separation

(b) In the equation for modified propelled mass, the factor 1.03 is used to account for the affects of

friction and the quantity

sin a corrects for the angle of thrust with the horizontal. For downward

ejection, the plus sign in equation (32) would be replaced by a minus sign.

(c) Figure 21 for determining charge weight is based upon the following equation:

C=kWv

(4)

This equation is a modification of equation (31). The constant, k, was determined by letting γ =1.25,

e = 0.10, F = 3.1X105 for catapults and 3.6X105 ft lb/lb for removers, and m' = 1.1m. In addition, k

includes a term to permit propelled weight to be substituted for mass and another term to give the

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answer (charge weight) in grams. The constant was found to be: k =6.25 x10 gm sec /lb ft for

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catapults, and 5.38X10 gm sec /lb ft for removers.

(2) Thrusters.

(a) The charge weight for a thruster may be estimated using equation (33).

Where:

F = total resistive force

S = piston stroke

e = overall efficiency (0.10 is a representative value)

γ = ratio of specific heats

(b) Figure 22 is based on the following equation: