modulating valve opens. This valve varies the
amount of hot air from the 400°F bleed manifold
temperature control system used to warm the
coolant fluid.
When the heat exchanger outlet fluid
temperature reaches 104°± 4°F and the missile
outlet fluid temperature reaches 85°±3°F, the hot
air modulating valve will close. This prevents the
cold and hot air modulating valves from being
open simultaneously.
The missile supply line sensor, located at the
outlet of the heat exchanger, is also used to sense
an overtemperature condition. If the coolant
temperature exceeds 115°± 3°F, the missile con-
dition (MSL COND) advisory indicator light il-
luminates. The hot or cold air modulating valve
will close. If the missile pump pressure drops to
60±5 psi, a pressure switch causes the MSL
COND light to illuminate. If pressure downstream
of the pump increases to 89±5 psi, the missile
bypass valve opens to return the fluid to the pump
inlet.
The missile cooling system consists of a cold
air modulating valve, hot air modulating valve,
air-to-coolant heat exchanger, coolant pump,
coolant fluid expansion tank, bypass valve, air-
moisture-contaminant remover, controller,
coolant temperature sensor, fairing interlock
switch, and liquid cooling control panel. Each of
these components is discussed in the following
paragraphs. The functional relationship of the
components is represented in figure 1-18.
Missile Cold Air Modulating Valve
The cold air modulating valve is mounted
on the air-to-coolant heat exchanger. It varies
the flow of refrigeration system air to the
heat exchanger. The valve has a butterfly, a
diaphragm-type pneumatic actuator that is
mechanically linked to the butterfly, an electro-
magnetic torque motor, and butterfly position
switches. Electrical signals from the missile
controller govern the torque motor, which allows
regulated air pressure to be vented. The smaller
the amount of air pressure vented, the larger the
valve opening. If the electrical power or air
pressure is interrupted, the valve closes.
Missile Hot Air Modulating Valve
The missile hot air modulating valve is
mounted on the air-to-coolant heat exchanger.
The valve varies the flow of hot air from the 400°F
bleed manifold temperature control system in
response to electrical signals from the controller.
The hot air heats the coolant during system warm-
up. The operation of the valve is the same as the
missile cold air modulating valve.
Missile Air-to-Coolant Heat Exchanger
The air-to-coolant heat exchanger consists of
two sections: weapons control system (radar)
loop, and missile loop. The heat exchanger is
similar to an automobile radiator. The coolant
flows through the core while air flows around the
core. When the radar portion of the heat
exchanger is being used, the missile cold and hot
air modulating valves are closed to prevent reverse
flow through the missile section.
Missile Coolant Pump
The coolant pump is a single-stage, centrifugal
pump driven by a low-slip, two-pole induction
motor. When the pump is operating, it circulates
18 gallons of coolant per minute through the
system. The pump is lubricated and cooled by a
small portion of the coolant, which is circulated
through the motor. A pressure switch in the pump
outlet opens when the pump output pressure drops
to 60 ±5 psi. The pressure switch causes the MSL
COND (missile condition) advisory light to
illuminate. Also, a thermal switch will open when
230°±5°F is reached. This switch causes the
pump to stop and also illuminates the MSL
COND light. The coolant pump is located in the
right Phoenix fairing.
Coolant Fluid Expansion Tank
The expansion tank is located in the right
Phoenix fairing. The tank maintains a constant
coolant fluid pressure at the pump inlet,
accommodates thermal expansion of the coolant,
and provides a coolant reserve for the missile loop
in case of leakage. The tank has a bellows, fluid
sight and level indicator, fluid relief valve, and
a pneumatic pressure indicator. The bellows is
pressurized to maintain a positive fluid pressure
of 30 to 37 psi at the pump inlet. Should
pressurization reach 45.0±2.3 psi, the fluid
pressure relief valve will open and vent fluid. The
fluid sight and level indicator displays fluid level,
and the pneumatic pressure indicator extends to
indicate air pressure by temperature degrees.
1-25
