Spinward Flow
SOC-14 5K
Exactly.Then all you need is the fittings, not the tanks.
All you need is the fittings, not the tanks.
Furthermore, if the fittings can accept "standard drop tank sizes" ... even if the configuration of those tanks are not ideally matched to the configuration of the ship (tanks design isn't purpose built for YOUR ship) thereby spoiling the streamlining, so long as you're in vacuum that streamlining factor doesn't matter. All that matters, when you jump (out at 100+ diameters) is the volume of fuel ... not the "shaping" of the drop tanks relative to your hull configuration.
You'll need conformal drop tanks (to retain streamlining) for any kind of fuel skimming operation (gas giant orbital needing partial streamlining or ocean water refueling needing atmospheric streamlining) to fill the drop tanks up in-situ as a single stage refueling operation ... but out at the jump point, any kind of streamlining concerns are a complete non-issue.
Furthermore, as a matter of simple economics ... if there is an in-system drop tank service for commercial use (they fill the re-usable tanks and recover them for refueling after use) allowing for drop tank "rentals" (per se), things get even simpler. If a ship wants to rent the use of a drop tank, they have to pay a rental fee and either the ship prepositions a "fuel deposit" for later use (potentially with a "fuel premium" cost of needing to deliver more fuel to the drop tank service than the ship intends to consume, such as if you're going to use 40 tons you'll need to deliver 50 tons to the drop tank service but will only be allowed to use your 40 tons allocation while the service keeps the rest for sale to other customers), or the ship "buys" the fuel that they're going to be using from the drop tank service (just like buying fuel at a starport) in addition to their rental fee. Such an operation becomes possible if the drop tanks can be jettisoned and thrust far enough away to not be destroyed when the starship jumps ... allowing the drop tanks to be recovered, inspected and refilled for reuse as a local service. After that it's just a question of unrefined/refined fuel and haggling over details (and "loyalty discounts" for repeat customers).
However, such logistical support realities then mean that (as previously mentioned) ... all you need at the design phase is the fittings, not the tanks themselves ... and as LBB A5 demonstrates, adding those fittings onto a ship is an expense of MCr0.01 and zero tonnage (a bargain, really).
Given the minimalist cost involved in adding drop tank fittings to a starship at the design/naval architect phase of construction ... why wouldn't you include such a detail, even if it isn't going to be a "use every jump" kind of option or necessity?
Better to have and not need (especially at that price of MCr0.01) than to need and not have, I'm thinking.
After that, it's a question of deciding what drop tank services are available at different starport types IYTU.
You can even do things such as saying that type A, B and C starports can all construct drop tanks ... but only type A starports will consistently have drop tank rental services available ... and type B starports can be a case of "sometimes yes, sometimes no" depending on location/location/location and other factors. Another option would be to say that drop tank rental services are only (reliably) available at type A and B starports of worlds with Population: 7+ (so not classified as Non-industrial), although there can be exceptions (for reasons various and sundry, such as having a naval and/or scout base in system).