For a catapult, the terminal velocity and, therefore, the kinetic energy is important and the resistive forces are very small.
Thus, the energy balance equation must contain a term describing the work done by a thruster in exerting a force through
. The equation of motion must also be altered to include the
a distance. In general terms, the work is equal to
resistive force against which the thruster acts. In general, this resistive force is constant or a function of stroke (para. 51d
(2)).
a. Damping Requirement. In some thruster applications, the velocity of the piston must be held below certain
values. To limit the piston velocity, either internal or external buffer systems are used. The interior ballistics of a
buffered thruster can be described by the following equations. The general energy equation defines the heat loss
in terms of a heat transfer coefficient, the surface area of the device exposed to hot gases, and a temperature
difference.
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