Section V. COMPONENT DESIGN

Figure 25. T28 Thruster.

experience with previous systems, but the testing phase

workhorse model is fabricated and tested.

The

is the major determinant. Systems are tested on

procedure then becomes one of modification and retest

breadboard mockups and on rocket sleds at various

until the design specifications are satisfied with the most

speeds to determine the overall operation of each

efficient arrangement of components.

device in conjunction with every other device.

g. A portion of the design and testing phases may

be eliminated by using computers. An analog computer

c. The operation of devices in a system may be

has been used for analyzing a catapult's performance

sequenced by mechanical means such as gear trains or

theoretically under various acceleration loads and

static lines; however, the most common method is

friction forces.

through pyrotechnic delays and bypass fittings on the

ends of propellant actuated devices. Many pyrotechnic

36. Systems. a. Multi-component PAD systems

delays have been standardized, but their metal parts

generally are designed by the air-frame or missile

often are modified to insure the proper fit in the various

manufacturer under the direction of the cognizant

cartridge cases. The tubing, hose, and gas fittings used

agency. However, in the design of propellant actuated

in these systems are also standardized. Various fittings

devices, systems can be improved by eliminating

and types of hose or tubing have been studied, but

devices or combining several operations into one device

standardization has not reached the point of determining

to improve reliability and guarantee proper operating

equivalent lengths of hose for fittings, as is done in the

sequence of the system.

hydraulics industry.

b. The sequencing of operations is determined by

Section V. COMPONENT DESIGN

sealed in position by crimping the

37. Cartridge. a. General.

cartridge case.

(1) The cartridge (fig. 26) is a metal can

which contains the propellant, igniter, and

(2) Most cartridges contain percussion

primer. It is designed to burst open from

primers,

although

electric

ignition

the pressure of the propellant gases. The

elements have been used in place of

can (case) is hermetically sealed to keep

percussion primers in cartridges for

out moisture (moisture interferes seriously

missile applications.

An electrically

with performance). The hardware portion

initiated cartridge is similar except for the

of the cartridge consists of a drawn

primer. The percussion primer is fired by

aluminum case and a head. The head is