wrote in message
...

Obviously, with 16 thrusters, there
are 16 valves, but there are only 12 switches and twelve potential grey
bars.

I just caught this and it too is irrelevant. The Helium valves are
redundant. That is why there are eight. The SM RCS system is bipropellant
and that is why there are eight propellant tank iso valves. It has nothing
to do with the number of thrusters.

Daniel