...in the fact that,

even if powered by nuclear reactors (the space "ships" would almost have to be, and hopefully fusion),

they'll have no more endurance than they can carry crew stores and other perishable supplies.

 

At least for the first few centuries until we get those replicator-like food makers such as Star Trek uses, ships aren't going to be able to carry a massive food-growing arena (?) that can allow the crew to subsist indefinitely on long duration missions (even though it should be expected that nutritionally-enhanced "space MREs" will be an obvious requirement on long missions, but just like today's personnel, don't expect them to subsist indefinitely, happily, on them).

Water and air reclamation will become much easier, but without access to food stuffs and other perishables, the space craft's duration would be no greater than many nuclear subs, needing to meet with replenishment craft every few months.

 

And besides, there will need to be considerable machine shop and parts fabrication facilities onboard the space craft: it won't be like just being able to surface, radio for assistance, or pull into the nearest port for repairs, which is only days, or at most, a few weeks away, and carrying so many just-in-case spares for the most likely components that could fail would end up needing too much additional bulk in the ship's design, just to carry adequate spare parts.

 

And until very fast travel speeds are achieveable (several 10's-100's km/sec, as Mach 10-20 just ain't gonna cut it),

as well as the obviously necessary decceleration (inertial dampers?) devices to rapidly slow down just as easily as they can accelerate,

space ships will have to be massive, at least as large as current CVNs, if only to be able to sustain crews for months on end with minimal,

if any,

resupply.

 

Low observable technologies and signature reduction will be a must, as such vessels won't be as maneuverable as Star Trek and Star Wars depict capital ships to be,

again,

at least not without inertial dampers, structural integrity field generators, particle & radiation shielding, and other cool techie stuff that looks & sounds so cool thanks to the special effects people, but,

let's face it,

is pretty much still light years away...at least so far as implementing them all into a workable design.

 

Perhaps by that time we'll have come up with the proper terminologies and colloquial jargon for space combat.

A space craft with endurance as long as its perishables? Like, a ship?

I think that "persistant" is the key feature.

The only reason we don't have nuclear reactors in aircraft is in case they crash in the wrong place.

The reason we don't have reactors in airplanes is there is no value in flying for years when the mean time between failures of the equipment onboard is measured in hours.
There is no value in paying for all the pain of building an airplane that can carry months of provisions when it is never more than some hours away from a place where it can regenerate and maybe even swap crews.  A ship needs to think of being days or even weeks transit from port.  A spaceship traveling for years may not really be a ship anymore.  It may be more correct to call it an ark.

 

Treadgar

Something I haven't seen explored in scifi is the impact that the path a particular culture takes to space, and to a space force in particular could dramatically impact what they call their troops, and different cultures might well use different names.

 

One culture might have fleets commanded by admirals and another might have squadrons commanded by generals. Some space forces might consider their ground troops to be Army, others Marines. Some might consider them comparable to naval CBs, others to the USAF ground units like pararescue and pathfinders--the folks who land on a planet to set up infrastructure to support the space craft.

 

The limited endurance on spacecraft of the supplies needed by their crew might dictate that ships in a campaigning space force live off of the land, finding habitable planets to obtain supplies from. As such, a ship capable of deploying a space elevator could be a key component of a scifi fleet that is frequently overlooked.