Rate of fire is determined by how fast the ejection pump can cycle. Usually in about 30 seconds or so. Each tube has its own slide valve. You can only have one slide valve open per bank. These are mechanically and electrically interlocked. We have not used compressed air to directly eject a weapon for 60 years or so...
We use compressed air to move the ejection pump piston which moves the water cylinder forcing seawater up through the Impulse tank. The impulse tank is a vertical tank which has both tubes running through it.. The slide valve for the tube being shot opens and allows the water from the impulse tank into the tube, thus forcing the torpedo out with HUGE force.... three to four G'sss This is one of the reasons you can launch at any speed.
Here is a crude quick drawing:
You can be draining/loading a tube at the same time you are shooting the other tube in the bank. The cycle time is from the time of fire to when the ejection pump ram goes back to battery, ready for the next shot..
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