In celebration of [FRAGMENT DELETED], I thought I'd put up the comprehensive, rationalised pennant number system used by the UNN to designate its various spacecraft and stations. Ship names are prefixed with a two-letter pennant, where the first letter indicates the hull type, while the second demarcates the intended role of the vessel in question. It's ridiculously accommodative - so far, each ship class has received an entirely unique pennant. I may have gotten carried away. Anyway, it's here for you to reuse, adapt, or just gawk at.
Hull TypeC - Cruiser
D - Destroyer
F - Frigate
K - Corvette
L - Light Craft
N - Naval Non-Combat Vessel
E - Expeditionary Vessel
A - Naval Auxiliary
M - Merchant Aerospace Vessel
H - Orbital Habitat
S - Orbital Station
P - Deep Space Platform
G - Planetary Base
RoleS - Surveillance Vessel
G - Guided Missile Combatant
D - Directed Weapon Combatant
C - Light Craft Carrier
E - Combat Support Ship
O - Ordnance Transport / Minelayer
B - Troop Transport / Garrison
A - Assault Craft
F - Freighter
T - Tanker / Refinery
K - Liner / Colony
R - Rescue Vessel
Y - Shipyard / Maintenance Facility
M - Asteroid Miner
H - Terraformer
W - Salvage Vessel
Z - Gatebuilder / Tender
As an example of the system in effect, pennant CG would refer to a large multi-role missile combatant capable of independent operation and optimised for endurance, while pennant GC would refer to a major planetary centre with light craft hangars and a small garrison.
So how do YOU classify your ships?