Development of Propellant Charge Design

which, with simplification, gives the total energy output of the thruster (FTS).

Where:

θ = angle in radians through which the hatch moves.

The angle through which the hatch moves is 15° or 0.26 radian. Substituting the applicable figure

gives

FTS = 100(8)(1/cos 15°+90(5)(.26)(1/cos 15°+(1/2)(6,000)(8)(1/cos 15°

)

FTS = 830+120+24,800=25,750 in.-lb

(e) Devices of this type usually operate at about 10 percent ballistic efficiency; therefore, the required

propellant weight may be estimated as follows:

(f) The thruster must overcome a high initial force which decreases as the stroke progresses; hence,

plateau propellant composition with regressive geometry (i.e., cord grains (uninhibited rod)) probably

are best for this application.

(g) If the angle (θ) through which the hatch moves is known, an approximate stroke time and propellant

burning time can be estimated.

This stroke time is conservative because it is based on an average acceleration of 5 rad/sec which is

actually the peak acceleration. The average would be somewhat lower.

52. Development of Propellant Charge Design. a. Grain Design.

(1) The basic problem in the selection of a propellant grain design for most stroking propellant actuated

devices is the requirement that gases must be supplied at an increasing rate during the functioning time of

the device. As noted earlier in this chapter, for most catapult applications a constant or even slightly

increasing pressure is desired after maximum acceleration has been reached. Due to (1) the increase in

internal volume as the stroke lengths, (2) the high heat transfer rate which causes a large loss of energy,

(3) gas leakage, and (4) energy transferred to the accelerated mass, an increasing rate of gas evolution

must be provided. Limiting this rate of gas production, however, is the maximum rate of change of

acceleration and the maximum acceleration allowable which