posted 10-15-2012 08:42 PM I would say that similar things said
of the Mercury spacecraft could be said about any complicated
system, even today. The design uses sensors with functional
limitations. So a mechanical switch closes when a fairing is
jettisoned, or a door is opened, and the circuit turns on a
control panel light. But there could be a mechanical failure of
the switch, or a break in a wire, or a broken lamp filament,
that could prevent the illumination of the panel light. There
would be other possible scenarios where the light would
illuminate when it shouldn't. Part of the piloting function (for
a crewed vehicle) and mission control function, is to understand
and interpret such sensor readings. This was especially
demonstrated with Apollo 13. And we see it with current Mars
probes, among many other places. It may not be the case of a
particular light being green or red, but similar sensor
interpretations would need to be applied.