Heh, beat me to it Tom Schoene
I had been thinking of starting a drop tank thread for those not already aware of all the issues beaten to death around it. And I was going to begin with the T20 80/20 rule. So on to my next issue with drop tanks...
Using T20 as an example, since the thread is so named and begun (though other systems will no doubt come into play), my problem is not with using the tanks as described for a fast burn and drop prior to jump but actually jumping with them attached or manuvering with them. The tanks are listed as costing a mere Kcr 10 plus Kcr 1 per dT of fuel capacity. Given the cost of a simple ship hull is Kcr 50 per dT and up I find it hard to believe a drop tank could have the structural integrity needed for manuvering or the jump grid needed for jumpspace. Also there is no mention of if you need more bridge allotment to cover the drop tank tonnage or not. Some of the other systems made you penalize streamling when the drop tanks were carried but this is also not addressed in T20 unless I missed it.
My suggestion, keep the p. 267 text as is with the inclusion of the 80/20 fuel usage rule here too but drop the last two sentences and the description line at the end and replace it with something like:
L-Hyd Drop Tanks: Tanks must be built and purchased as an empty hull. They are treated as a carried craft in an external docking mount (p. 274). This specialized docking mount cannot be used for normal craft but is dedicated to drop tank usage and rapid fuel transfer only. The 30% extra volume in the docking mount includes volume for the extra 20% of the fuel that must be retained through jump.
Alternatively a standard docking mount may be used for a drop tank if allowance aboard is made for the 20% fuel required. This is in addition to the normal 30% required for umbilicals (5%), launch and recovery grapples (5%) and airlock access (20%). If access to the craft/drop tank is not required dismountable tanks may be installed in the normal airlock access volume for the 20% fuel margin. In some cases specialized small craft are built to use such an arrangement, giving the ship the option of a dedicated small craft for rapid refuelling when retained or a drop tank that can then independantly skim more fuel and be ready for the next ship that arrives.
For example: An architect desires a drop tank with 100 dT of jump fuel for a ship. The external docking mount will require 30 dT inside the mother ship, but will include 20 dT to retain the fuel margin to see the ship through jump when the tanks are dropped. This 20 dT of fuel capacity may also be used for other purposes if filled and not used for jump. The base cost of the mount is Kcr 120 but to avoid the streamlining penalty we'll pay Kcr 240. The tank itself will be a sphere to allow gg fuel skimming (partially streamlined). While carried by the mother ship (fully streamlined) the ship is reduced to the drop tank's partially streamlined factor. If we had chosen a streamlined tank, at more expense, the mother ship would retain its fully streamlined aspect even with the tank attached. The tank will cost Mcr 7.0 before discounts.
Historically drop tanks do not come into use until about the year 1100 in the OTU but they may be built at any TL supporting ship construction. The major reason they are not widely used is safety. No commercial vessel carrying passengers is allowed to use drop tanks and most commercial operations do not use them even for freighters because of the added expense for hazard pay scale for the crews and higher insurance for possible loss.
Firms may be hired at most starports to recover drop tanks and store them for use upon return. Costs are as per p. 350 for cargo shuttle service (x10 for 100d to orbit) and orbital berthing, paid in advance. Tanks dropped without arrangement for such service are considered abandoned and fair salvage. Tanks left in orbit beyond the prepaid berthing fee are held by the recovery service for 30 days before becoming the property of the recovery service. If reclaimed before the 30 days the penalty is double the 30 day storage fee, regardless of the actual lateness of the claim.
The militatry maintains their own recovery service, and all military drop tanks are considered contracted even if apparently abandoned. The military does pay reasonable finder fees and salvage costs for temporarily uncollected drop tanks that are returned to them.
Some large corporations are experimenting with drop tanks and also have their own recovery service. These will often take private recovery and storage contracts as well.
Note:
This is still undergoing some editing and its rather simplistic. For example the example above could provide 120 dT of fuel, but as only 20 dT is onboard if the tanks are dropped it still limits the jump to 100 dT total in dropped mode. The 120 dT could be used for retained mode jumps though, or you could fiddle the requirements so the drop tanks are just enough for the 80% and expand the onboard enough to keep the 20%. I'll look at that for the next edit.
Hmm, simplest might be to say the 20% "lost" in the drop tank is due to the rapid transfer requiring a 20% expansion volume aboard the ship. i.e. the drop tank pushes the full 100% a little faster than the j-reactor can burn it. This results in the 20% aboard backfilling until you reach the point of 80% burned, 20% backfilled, and the tank is empty.
Also note the % breakdown for the docking mount is just my own little invention from the rules simple 30% total, so you won't find it in the book.
Critique, cudos, questions?
