Slight clarification: Commercial jump drives don't work for ships that use non-Commercial engines.
A military vessel, weapons and all, that uses a commercial engine (power multiplier 0.5 or lower, size 25 or higher) can make use of a commercial jump engine.
Also, military jump drives are not military-grade components themselves, a ship with them can be a commercial vessel (and usually is in my games, typically consisting mostly of 0.5 power engines with some decent-size fuel tanks).
Hmm....I've never actually tried either of those scenarios because why would you??
A military ship with bloated, inefficient commercial engines?
A commercial freighter/colony ship with a military jump drive that's going to need constant maintenance and need to be way heavier than it needs to be?
The one scenario I could see it for are troopships -- my troopships are typically commercial designs. But then I'd either build an armored commercial jump tender, or integrated jump drives on the troopships. Or even just tacking on some small defensive weapons or >0.5 power engines and just making it a military vessel.
I build low-power military ships all the time.
Cheap and fuel-efficient, often possessing low-powered weaponry as well (don't care about bulk if we don't need high performance, low-tech components are cheaper per HTK than armour and can be repaired in space). 100 railgun shots every 15s on 10000t may seem a sorry excuse for an escort vessel... but at about 500BP it's a bargain.
And as I said... a military jump engine is no military component, the jump ship can still count as commercial. To me, putting jump engines on a military ship that needs maintenance seems a waste unless I have no choice (i.e. I want more speed than I can get on a design that consists mostly of 0.5 power engines).
Can you post a sample design? I'm still thinking they're horribly inefficient, as they'll be slow (i.e. dead), undergunned (i.e. dead), and take some serious investment in your military shipyards.
I'm curious about the mineral wastage as well. Even if you salvage every wreck you're still pouring a lot down the drain, and those are decidedly nonrenewable resources.
Sorry for the delay, real life intruding.
Copied from a post on reddit...
Just Shoot Me class Corvette 10 800 tons 321 Crew 481.8 BP TCS 216 TH 480 EM 0
2222 km/s Armour 1-43 Shields 0-0 Sensors 1/1/0/0 Damage Control Rating 3 PPV 81
Maint Life 1.04 Years MSP 84 AFR 311% IFR 4.3% 1YR 78 5YR 1166 Max Repair 48 MSP
Intended Deployment Time: 11 months Spare Berths 0
240 EP Commercial Ion Drive (2) Power 240 Fuel Use 4.05% Signature 240 Exp 4%
Fuel Capacity 100 000 Litres Range 41.1 billion km (214 days at full power)
10cm Railgun V1/C1 (27x4) Range 10 000km TS: 4000 km/s Power 3-1 RM 1 ROF 15 1 0 0 0 0 0 0 0 0 0
Fire Control S00.7 24-4000 (2) Max Range: 48 000 km TS: 4000 km/s 79 58 38 17 0 0 0 0 0 0
Gas-Cooled Fast Reactor Technology PB-1 (6) Total Power Output 27 Armour 0 Exp 5%
This design is classed as a Military Vessel for maintenance purposes
Note the fairly advanced fire control speed tech compared to the rest, it's the most important tech line for the concept.
These are quite good at defending against ASMs, assuming no missile ECM, which I don't think I ever encountered. A flotilla of a few thousand BP can stop most missile threats without undue operating costs or logistics burden.
Against heavy AMM spam they're cheaper than the ordnance needed to shoot them down, I'm happy if these get targeted rather than something more valuable.
I may keep building the style at later tech levels, sometimes accompanied by an even more hilariously bad offensive variant: large-ish but low-tech lasers, or whatever I looted off wrecks/ruins that's too good to scrap but too bad to put on respectable ships (which I build in a completely different way, with an eye towards weight efficiency).
Most of the time, I favour more sophisticated ships for offense, and cheap flak barges (maybe literally, this works arguably even better with unpowered pods and commercial tugboats) enter the picture when my shiny high-tech ships can't play to their advantages.