Originally posted by stofsk:
So I figure that you have to decommission ships after a certain point. Traveller posits a future where ships can be in service for a century at least.
Would you need to mothball ships for decades after their century of service? (if it turns out that naval ships actually have more or less time in service in Traveller, so be it) Assuming a relatively slow tech progression, a ship that was made two centuries ago might not be up to the standards of the day's modern battleship, but in cases where you're running out of ships and need anything that can fly, bringing a ship out of retirement is still an option.
The TU History of the 60kton Fleet Intruder class High-Lightnings CA's that saw action in the Imperial-Solomani Rim war (992-1002 TI) and what happened to the surviving members of the class. Several were sold to become huge armed bulk freighters--one sold to an over-the-border Imperial trading Sector-wide firm, iirc.
Several were mothballed at Trin/Deneb. One of these Azhanti-High-Lightning-class received upgrades to a meson gun instead of her initial issued PA spinal mount, and a partially streamlined hull for gas giant refueling herself under emergency circumstances.
ISS Arrival Vengeance CF-6415 was handpicked to be "stolen" by mercenaries & nobles to take on Archduke Norris' MT-era module adventure to scout out what remained of the Shattered Imperium.
Problems though: antiquated computer systems, a hull that's probably marked with micrometeorite impacts, and no doubt other maintenance concerns that would necessitate the ship still costing money even whilst in mothballs.
There are places in space one can store such vessels, and 'mothball' ships. Most have been discussed already. One such place to avoid your mircometeor damage is of course in the Oort cloud of a system. It isn't the only one, however. They could also be parked if installations are not there already, at the la Grange points of a planet.
Or would you decommission the vessel? Today, when you want to get rid of a vessel properly you basically sink the thing and create an artificial reef. In space, what do you do? I imagine you can program a course orbit that will take the ship into the local sun. Or if there is a gas giant nearby then a one-way ticket down would work in a pinch.
Some particularly famous ships can be converted into museums. For everything else, that one final voyage is made.
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Okay
Stofsk--
there are several prudent reasons for mothballing, besides saving for "rainy day war". 1.)
A new client state might appear over the border, and wish to become more familiar with Imperial tech.
What better way than to sell them some the outdated (-1, or 2 TL) Imperial vessels?
2.) Auxillary training vessels for Navy academy crews.
3.) A Sector/ subsector natural disaster (say a star goes nova, like in the Maghiz-of Darrian space)--cobble together a rescue-evacuation fleet--tap your mothballed ships!
These are just a few reasons why mothballing is a good idea. To answer how its done, better ask someone else with knowledge of the present day techniques. I'm honest to say I defer that with handwavium and nod, "they do it/ did it."
Now to the latter part of your query:
The hull and anything not nailed down or too expensive to open the hull up and remove at the time is removed & stockpiled. Where? Why to the Naval Depot Bases! Parts is parts, after all.
Now a breaker-yard, is a base where battle damaged vessels unworthy /too expensive to save are cannibalized down to hull metal. The scrap is sent back to A-class & B-class ports for making more hulls, and anything else (turets, weapons, power systems, sensors, etc that remains winds back up either at a Depot, or if need is immediate, to nearest Naval base where ships of that class are for their spare parts Stock piles.
And last, for TNE purposes with technology lost by the Rebellion's ferocious ship losses throughout, those older hulled vessels become the pocket empire's new fleet with a little work. TA-7 'Fighting Ship's gives us a look at what was an auxillary vessel then (200 some odd years prior) and what would be 2nd- 3rd line vessels of the Tne era if found and restored.
Thanks again, Good topic!
That's where the 15 minutes came from.
instead of ducking who'd served on the former class without the new upgrades when reporting to the bridge! 
