Figure 39. Floating piston and thermal expansion chamber.
space between pistons. When the cartridge fires, the
g. Other damper arrangements are possible, and
expanding gas exerts a pressure on the gas piston. The
one, a system in which the gas acts to rotate a threaded
liquid on the other side of the gas piston experiences a
shaft and advance the piston while centrifugal brakes
similar pressure and transmits this pressure to the load
attempt to maintain constant velocity, is being studied at
piston. The load piston exerts a force on the liquid in
However, the majority of dampers in
the chamber and causes liquid to pass through the
existence and being developed are of the fluid-orifice
orifice into the space between chambers. As the pistons
type described here.
move forward, the load piston moves at a higher speed
46. High-Low Systems. a. In propellant actuated
than the gas piston which is the reason for the name
devices using high-low systems, propellant
"hydraulic multiplier." The piston speeds are dependent
on the size of the orifice in the load piston.
f. Whether or not damping systems are used is
another consideration when calculating wall strengths.
For example, the "locked shut" pressure in the gas
chamber of the device shown in figure 40 may be
greatest pressure that the body of the device must
withstand occurs in the damper chamber. The force on
the gas piston is equal to the force on the load piston,
but on the fluid chamber side of the load piston the force
is distributed over a smaller area (because of the area
occupied by piston shaft) ; therefore, the pressure
Figure 40. Thruster with fluid damping.
exerted by the fluid on the body walls is greater than
that of the gas.
Locked-shut conditions may be
simulated by closing the orifice, but not by resisting