Those nose spikes are properly termed a "Barometric
Probe"commonly referred to as a "baro probe". The probe is a part
of the warhead system and was used to sense the barometric pressure
(as opposed to dynamic pressure) at altitude.
This pressure sensing was then sent to the barometric switches (baro
switches) in the warhead where they served to "advise" the warhead
circuitry of the missile altitude. This information was used by the
warhead to complete warhead arming sequences and to provide altitude
warning in the fail-safe system to provide a "one point" or HE
detonation as required by a missile returning to low altitude with
no direct fail-safe signal received from the MTR. The baro switches
were set at the time of mating the warhead to the missile (this was
done by use of the T 4014 Test Set in the Warhead Building) and
could also be set at the launch area after mating.
There were two altitude settings - high and low - arming sequence
and fail-safe sequence settings. The baro probe was a delicate
mechanism and was always part of the Technical Proficiency
Inspection as relates to the unpacking (they came in steel
containers), cleaning, and mounting. It was carefully inspected for
freedom of movement and cleanliness.
There came a time when the Baro Probe was requiring excessive
maintenance as they were always exposed to weather
(we are speaking of above ground sites now) and a bright red cover,
which resembled a doghouse for a dachshund was installed.. It made
the missile look odd but kept the probe clean. I think this came
about around the time of the "President Kennedy" plug if anyone
remembers that.
The probes were a big pain but served a very important purpose.
The "plain old nose spike" was a dummy spike so one couldn`t tell
(by casual observation) which was a nuclear warheaded missile and
which was an HE only as a nuclear warheaded round always had a baro
probe mounted and of course HE did not require one. We are speaking
of counter-intelligence measures. Perhaps only used in Europe - I
know they were used in Europe but by the time I served in the States
around Cincinatti (the Dillsboro, Indiana site guarded Cincinatti) I
saw no dummy probes - only covers.
The plain old or dummy spike became obsolete when the baro probe
cover came in to use as the covers hid all sight of the probe.