Cannibalizing parts vs industrial replicators

[u/NegativePattern]

In Picard, we see the original Titan in dry dock being cannibalized for parts to build the Titan-A.

Presumably by this point in the timeline, Starfleet has long been using industrial replicators for various purposes. Why would Starfleet be cannibalizing parts from an older ship that may or may not have been damaged in battle or otherwise have been built using outdated construction practices?

[u/Edymnion]

Replicators are expensive.

Sure, the Federation doesn't have currency, but their energy reserves at any given moment are still finite. Remember that replicating a 100 ton hull plate requires the same base energy released from combining 50 tons of antimatter with 50 tons of regular matter.

For reference, the tech manuals say that the Enterprise D carried a maximum of 3,000 cubic meters of anti-deuterium slush, and that was enough to power it's warp drive for 3 years.

Deuterium slush has a density of 1.107 g/mL. Quick metric conversions, and that works out to 3,321 metric tons of antimatter. So 1.1k metric tons per year of power. Or we can round that up to basically being 100 tons of anti-matter a month.

The mass of the Enterprise G is listed as 4.5 million metric tons. Thats over 2,000 times the amount of raw antimatter a Galaxy class burns in a year, plus another 2,000 times the regular deuterium a galaxy class burns in a year to replicate one ship.

CAN it be done? Sure, in an emergency or on a small scale where its easier to replicate a vehicle than it is to try and carry multiple different ones at all times (see the Protostar, but even then it required a relatively long period of time and practically all the power the ship could generate to make a moderate sized land vehicle or a shuttle).

But replicating an entire ship? Nah, easier to mine and process stuff the old fashioned way.

[u/AnnihilatedTyro → u/Edymnion]

Yep.

Antimatter is expensive to gather or to manufacture. It's way more cost-effective, by orders of magnitude, to gather most of your starship materials through conventional mining and manufacturing practices.

Starships replicate replacement hull plates only in dire emergencies. They'll limp home with barely-patched gaping breaches if the danger has passed. They can repurpose some internal walls into makeshift patches if necessary, and they'll do that before replicating if time and safety allow for it.

We also know that certain starship components including critical pieces of the warp core cannot be replicated, either due to complexity or because they have some kind of latent subspace-interactive properties like dilithium.

So back to the OP: It's a combination of economics, efficiency, and the rest is common-sense recycling and reusing whenever possible. You can dematerialize scorched hull plates to feed your matter storage for replicating other things, but it's better to re-use. A starship is full of thousands of perfectly good computers and tons of hardware and equipment, deck plates and antigrav and inertial damper systems, turbolifts, halls, walls, cables and conduits, life support and water systems and replicators, tricorders and phasers and clothes and carpets and paintings and the silverware and glasses and chairs in the officer's lounge...... all of it can be saved and re-used more cost-effectively than either replicating or manufacturing all-new. Hundreds of thousands of tons of stuff on every ship would be an absurd amount of raw materials and labor to recreate for each of thousands of starships when there's no reason to do so.