Simply put; sparse!
The Scout service can't even establish regular contact other than a multi-month scout/courier visit for many worlds of the imperium. Much like that the Imperial Navy presence for many worlds is just a gazelle every couple months, only not any fixed schedule, if that. They're also the folks with enough nuclear missiles to strilize worlds forever, and not only the skill and practice but willingness if need be to do so.
For me the Imperial Navy *is* focused on enforcing the rules of the Imperium and maintaining interstellar military presence and lines of communication. Megacorporations play a big role in this. There will be major fleet presence at the heavily industrialized/high-tech/high-population worlds, and escorts for the major shipping that that connects these worlds, mostly on the scale of a cruiser or two (maybe) and and 6-10 destroyers. Even more traffic to/from these lines with naval bases, like the cargo ship semi-annual run with nuclear missile resupply for the fleet. Some worlds have high SDB defense networks.
There are fleets proper, due to the emporer of the flags aspect, they are major political (and military force!) players. Sector fleets as the "main" fleets of the imperial navy, not under direct and local control of capital. Capital will have more than one fleet, at large on deployments/mission/liasons with the various sector fleets. Spirit of like the baron wars of medieval times. Emporers have claimed that title by bringing their fleet to Capital...
The Capital Imperial "proper" fleets really do serve a PR role of "showing the flag" by sheer ability to travel interstellar large tonnages of ships, reclaiming humanity from the collapse of the 2nd imperium and the long night, striking awe (and terror?) into the lesser worlds of the imperium, and often even the major worlds!
Subsector "fleets" may have some cruisers and destroyers at the subsector capital, the vast majority though world/group of world mobilizable subsidized merchants, ensuring trade (patrolling) groups of worlds. IMTU subsidized merchants are usually quasi military/militarizeable vessels for that very reason.
Nobles play a large role here. Subsector military fleets would tend to be battle riders with the transports kept/controlled by the subsector capital, or even dependant on Sector navy for transport (!)
IMTU the navy does *not* have a gazillion J6 courier order/news/comm system set up imperium wide. If you need a message sent send a trusted commander and his ships.
The megacorporations themselves have fleets, like some of the tradewars stuff, or mention in Axhanti High Lightning of "privatized" vessels. Armies are carried by the navy, so there are big fleets of cruisers to transport regiments and such for major wars of conquest, all carefully designed sized and managed so as to be able to be destroyed by the navy fleets <s>. The multi kt transports are often the biggest ships around and are like a cruiser, tbh, outmassing their destroyer escorts.
Fleets also are actual assemblages of ships, there aren't so many of them they're all over everywhere, they tend to be in an area, regularly try to establish and maintain contact and awareness of other fleets compositions, locations, movement, and communications as well. this is most of the fleets day to day activity.
On a darker note, Capital has attained TL15, but the vast majority of the fleet are recovered/refurbished TL12-13 Solomani 2nd Imperium ships as a core supported by TL8-11/12 Vilani Bureau fleets. Much more common J2 or J3 vessels making multiple jumps for further travel. The advantage of Capitals' TL is a greater range of operation for travels of it's fleets.
Of fleet composition and type, i tend to not like the ones from ships of the imperium cause they not too thought out often. My goal is to have the destroyers be the rocks of ~1kt missile havey armor, Lt Cruisers of meson Spinal say 20ktish or the smaller PA spinals, and Heavy Cruisers PA spinals. Translation Vilani Kt Missile destroyers, Solomani Lt PA and heavy Cruisers, Imperial proper Lt Meson Cruisers.Hating unhittable ships i tend to keep agility low enough that it resembles a fight if using high guard, specifically as regards fighters being able to hit capital ships, the TLs i use help in this. So much more anti-fighter batteries of say FF6 missiles, 6xtrp msl. Don't really use super computer fighters, more there's a large amount of say model/3, and those the top of the line fighters. things might change what with mongoose travellers wings or whatver, but the space combat seems half there and broken tbh, lots of stuff in it i like though, like barrage fire of sand as anti fighter/light attack.
Ginam Sera? i forget the name my ~2kt HG vilani destroyer/troop transport, TL9/11, multi jimp capable is posted here somewhere.
In a lot of this i was influenced by T4 Melieu 0, and pocket empires, where the imperium formed by co-opting existing pocket empires making them the local nobility. So a sector fleet is in reality a pocket empire with its own TL industry base and design philosophy, or even some subsector fleets being minor pocket empires. Much of the strength of the imperial fleet is their (marginally) higher TL base and hence jump capability, but moreso the skein of resupply points and bases/depots to enable (and control) fleet movement and resupply. The problems arise when fleets whether internal or external go avoyaging <s>
) spent on the military. That's not a problem if the interstellar state in question is peaceful and under no threat. But for a state like the Imperium, hemmed in by three hostile (Solomani, Zhodani, K'Kree) and three unfriendly powers (Aslan, Vargr, Julians), at least two of which (Sollies and Zhos) are of comparable size and effectiveness (TL)[*] it does matter. An expenditure of 3% is a little low to be plausible, but not completely so, and it IS canon. But anything lower than that is just not plausible to me.
