Like Sol/terra is a very well traveled system. If a ferry would work anywhere it would be there. The travel time is only 9-10 days from earth to zenith with a dropship. The cost of a dropship moving itself is 10 burn days is the same as 10 burn days of fuel you dump with reactor charging an engine, but the dropship has a very low tonnage cost per day. Now a tiny ferry drive rated to 1 LY presumably is so tiny it can affordably transport multiple dropships cheaper then they can move themselves.
First question is how much time is saved by burning to (effectively) Saturn's orbit from Earth than going to either Zenith or Nadir.
Second question is how expensive it is to build such ships initially.
Third question is the general cost of maintenance. One thing to consider in that is how much it costs to maintain a sail versus the Dropship fuel saved.
Then from there is how long it takes for that ferry ship to "pay for itself" in how much it "saves" everyone in its operation.
Also, if the drive is too efficient, then 1ly warships, which would quickcharge their way across conventional 30ly leaps, would have massively more room for weapons and armor at a fraction of the cost, only spending a little longer making big jumps but having far too great an efficiency once in system.
Unfortunately, any JumpShip that can go 30 lys per Jump is pretty much doing it on solar power, and can (usually) guarantee they will land near a star. While a 1ly "ferry" ship would almost guarantee that MOST of their Jumps will not be near a star so must be using fusion engines/fuel for recharging the core. That would not be an efficient use, even if it could "theoretically" get their faster with a slightly faster charging Core per Light Year.
If the ferry is more efficient in both speed (charging time) and fuel (transporting multiple big civilian droppers for less fuel then the droppers would spend) then we wouldnt see dropships with interplanetary drives in the same manner. The ferry would be the defacto solution. Already, we can use civvy jumpships to spend 183 hours charging with a solar sail to bypass the dropship transit time, so the ferry needs to also be more efficient then civilian jumpers with a sail.
Nope, sorry. You're missing some key points.
First, Jumpships cannot bypass Dropship transit time. Sure they can show up where the ferries would ostensibly show up, but they would have to keep up real time data on where everything is in the system before they Jump in. There are many reasons why the Zenith and Nadir Jump Points are used consistently instead of just Jumping in on the ecliptic, but reliability of that point is the biggest.
As it is, it only shortens the time, not bypasses it. As I mentioned above, its the difference of flying up/down at an angle to the center of the system to the Jump Limit versus just flying "out" along the ecliptic. I don't think it's huge, maybe saving 1-2 days in Sol, to use the example.
Second, not every system could have one. There will be far more systems without Ferries than with. So the normal Dropships we have now will be needed.
Third, they same would still be needed for invasions. There is no guarantee that the ferries would be available in the first place (base protocol would be to Jump out to ecliptic) or be in sufficient numbers to carry the entire invasion force.
So in final point, it only has to be efficient enough to be able see paying for itself and profiting over the duration of its use in order to justify its use. It doesn't have to be a very high level of efficient, just efficient enough.
