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General Drop Tank Tender?

Spinward Scout

Spinward Scout

SOC-14 5K
Baron
Has anyone ever designed a Drop Tank Tender?

Or are these things disposable and end up as Space Junk just floating around after being disconnected from the ship that used them?

I'm thinking that a beacon could be activated after use and the Tender goes and picks it up. Refuels it and makes it ready for another ship to use.

Does that sound plausible?
 
Sure. Might vary by rules version, though.

Part of the pretext for making them non-reusable is that if the departing ship needs to be 100 diameters distance from the tank, blowing the tank to smithereens makes the 100D radius of the tiny bits really small, reducing the necessary separation.

But even 1g acceleration is overkill to get far enough away in even a couple of minutes. So, I'd figure fragmenting the tanks is optional rather than required.
 
Spinward Scout said:
Has anyone ever designed a Drop Tank Tender?
Click to expand...
You're truly into non-starship territory for one of those ... because no real "need" for a jump drive. The entire operation is "local" for pickup and disbursement.

Ideally what you're going to want is a Fuel Tender that can contain (buffer) LOTS of fuel, however, that big ship is more like a logistics depot. The real workhorses are going to be the fuel shuttles that go wilderness skim unrefined fuel and haul it up to the Tender. The trick is, it's going to take them "a while" to transit the 100D from world to jump point ... and they can USE that transit time to refine fuel while en route! That way, the fuel shuttles skim unrefined fuel, but deliver refined fuel to the depot Tender so as to buffer the logistics load.

You then have ANOTHER set of small craft whose sole job is to runabout and retrieve dropped tanks so they can be brought back in, refurbished and refueled by the Tender depot. Contracts and billing for services all get run through the Tender depot.

Depending on the specifics of the star system and worlds within it (and the number of likely destinations outbound from it) you could wind up with a half-dozen (or more) Tender depot operations plying their trade within a star system at different commonly used jump points.

Basic idea is to keep the fuel depot Tender "on station" near a jump point and then use fuel shuttles to and small craft to do the "legwork" of skimming fuel for transport and recovering drop tanks after use. That then permits the depot Tender to negotiate with multiple outbound ships on a somewhat expedited basis.

After that, it's mainly a matter of choosing a few drop tank sizes to "standardize" on (20 and 50 sound reasonable for free traders and other low end merchant traffic) with a single ship simply "stacking" as many drop tanks as needed to meet their jump fuel quota.

Beyond that ... it's a question of financing, business model and logistics.

Note that this kind of operational scheme is EXTREMELY SIMILAR (although the details are slightly different) to how XBoats and Tenders ought to operate along the Express Network.
 
Agreed. A lot of this can be done with small craft. (Consider a Modular Cutter hauling a 30Td drop tank with two sets of fittings -- one for the cutter, and another set to supply a second ship.)

On the other hand, something of the sort could help with "running jumps" (burn-jump-retroburn) too. Tanker paces outgoing ship -- which is running at its maximum acceleration without being burdened by the tanks -- and hooks up only as they near jump limit.

For example, a Type A Free Trader can't tow drop tanks (Size A M-Drive yields<1g accel if ship is over 200Td). The Cutter could carry the necessary high-volume fuel pumps. (But the free trader might not have compatible fuel filler receptacles...)
 
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Canon had drop tanks as destroyed on use.

There is a very good reason for this.

If a drop tank is reusable then there is nothing to stop you putting an engine on the drop tank.

Once you open that can of worms then thee is no reason for a ship to carry jump fuel internally, use a fueling ship at the jump point.
 
The reason that the drop tank is, eh, destroyed, because it's explosively expelled.

You'd think that's less of an issue in twenty minutes, than six, to establish enough distance between the Event and forty percent of the original starship volume.
 
GJ8.gif


Though, if you think about it, that's a thin metallic skin open to space, so essentially, no volume, therefore, no discernible effect on transition.
 
mike wightman said:
If a drop tank is reusable then there is nothing to stop you putting an engine on the drop tank.
Click to expand...
It's worse than that in T5, a drop tank is a regular hull and presumably any regular hull can be a drop tank.

E.g.:
T5.10, B2, p37:
_ _ The Type CE is a minor naval vessel deployed in a defensive role; the ship is tailored to operate in close formation with larger vessels.
_ _ The ship has three modes of operation:
_ _ Standard with Drop Tanks (400 tons): Jump Drive H in 400-ton hull produces Jump-4. Maneuver Drive H = 4G.
_ _ Without Drop Tanks (300 tons): Although Jump Drive-H in a 300-ton hull can produce Jump-5, in-hull fuel tankage restricts the drive effect to Jump-2 (based on 60 tons of fuel). Maneuver Drive-H = 5G.
_ _ Special (300 tons after dropping tanks): The ship with Drop Tanks and Transfer Pump can process 150 tons of fuel to support Jump-5, with the Drop Tanks shed before Jump initiates.
_ _ The 100-ton Drop Tank can support one HardPoint and associated weapon.
Click to expand...
 
mike wightman said:
What if...

what if merchant ships don't carry jump fuel, the cost of "refined fuel" is paid to the tender company
Click to expand...
You'd be paying Cr500 per ton of refined fuel plus a surcharge of Cr100 per ton for use of the drop tank(s) ... so Cr600 per ton of fuel (basically).

For credit shaving merchant operations, that can be potentially viable as a business model ... but only within a restricted subset of starports. The logistics for drop tank operations effectively requires a logistics tail back to a type A or B starport (for manufacture of the drop tanks as well as maintenance of the craft used in the operation). As soon as you start cutting type C-X starports out of your list of possible destinations, you're going to be limited to a very specific subset of trade routes ... and ... you're going to be HIGHLY DEPENDENT upon third party drop tank services in order to be able to jump AT ALL, which can translate into a Security Hazard™ depending on who is paying whom for what.

So definitely something that is theoretically DOABLE, but the tradeoffs in terms of (limited) available destinations may not be worth it. The entire premise is dependent upon there being a large enough volume of trade (and the operator being able to "capture" sufficient market share of that volume!) to support such a business model. The nice thing about this business model, if you can find places to deploy it, is that because the starship is limited to type A/B starports ONLY, there is "no risk of direct piracy" while en route in space, because type A/B starports have a sufficiently robust system defense patrol presence to drive out any aspiring pirates. Instead, the "piracy" threat becomes more a consequence of financial status (reposession for skipping mortgage payments, lost stake in gambling, etc.) and starport berthing security services (stolen out of the hangar bay) rather than getting shot at and boarded by pirates while in transit between world and jump point.
 
Fuel tenders have been talked to death. The hand wave is that somehow drop tanks are destroyed on release for Some Reason, and thus make Fuel tenders impractical (because they, too, would be destroyed).

Otherwise, they are quite a game changer in interstellar commerce. Fuel tankage is no longer a large portion of ship design, most jump fuel is handled by the tender, which detaches and jets 100D away while the final jump fuel is pumped from an internal tank (perhaps called the buffer tank) and the ship finally jumps.

A J3 ship could easily gain 20% more cargo volume by delegating 2J of fuel to a fuel tender. That's a big deal.

Book 5 has disposable drop tanks at 10,000 + 1000Cr per ton of fuel. Well, when cargo pays 1000Cr per ton, pretty much a losing proposition.

A rough design of a 3000 ton fuel tender runs about 1200MCr. For a 10,000 ton freighter, offloaded 2000 tons of fuel gives 2MCr extra revenue to a 10,000 ton freighter (extra 2,000 tons of cargo @ 1000Cr each). For a J3 10,000 ton freighter, 2000 more tons is a roughly 50% boost to overall capacity. Take 2 of these tenders (one at each end), and a freighter running every 10 days, 36 trips a year, 72MCr extra revenue. 2400 MCr/72MCr = 33 years of "payback". Support 6 ships, and that knocks the payback down to 5 years.

That's not unreasonable in busy systems.

BUT, canonically, it's "not done" for "some reason".
 
whartung said:
BUT, canonically, it's "not done" for "some reason".
Click to expand...
Under T5.10, anything smaller than the jumping craft within a jump bubble misjumps... (T5.10·B2·p.113)
Anything bigger ensures the jumping ship itself suffers a misjump. (T5.10·B2·p.120)

It appears to me to be a case of the ship kicks them off, they don't have to clear the 100, but if they don't, they wind up somewhere other than the departure system...
 
AnotherDilbert said:
It's worse than that in T5, a drop tank is a regular hull and presumably any regular hull can be a drop tank.

E.g.:
...
Special (300 tons after dropping tanks): The ship with Drop Tanks and Transfer Pump can process 150 tons of fuel to support Jump-5, with the Drop Tanks shed before Jump initiates.
_ _ The 100-ton Drop Tank can support one HardPoint and associated weapon.
Click to expand...
Um... WHAT!?

I know what they meant: The ship gets a free hardpoint with respect to its 300Td core hull, because it's built with a 100Td drop tank. I can think of an easy exploit of this, and now that I've stated it this way so can you -- any of you could.

What they really meant though was that they were transposing the HG1 10Td-bay PartAcc into two HG2 PartAcc turrets, then using the drop tank tonnage to justify that second turret, then combining the two turrets into a single weapon approximating the 10Td bay weapon from HG1. Of course, this was done without actually stating that's what they'd done, because that'd highlight that the earlier version had included a now de-canonized 10Td weapon bay.

On the other hand, reading it literally it indicates that hardpoint is mounted to the tank, and goes away with the rest of the tank when you drop it. I can almost buy off on this, especially if it's a plasma/fusion gun that can double as an ejection rocket...
 
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aramis said:
It appears to me to be a case of the ship kicks them off, they don't have to clear the 100, but if they don't, they wind up somewhere other than the departure system...
Click to expand...
I mean, that's fair if that's what's going on. But, similarly, bolt an M-Drive to one of these things, and it should be straightforward to "get out of the way", thus the need for the buffer tank, which gives the tender time to move.

Now, one could suggest that the risk is too dangerous. If the tender doesn't get away in time, perhaps both ships are at risk and this is why it's not done. It could be done, but the risk is too high were it to be routine. Perhaps civilian aircraft don't mid-air refuel for a similar reason (and fuel tenders arguably don't make a whole lot of sense for routine military operations, and drop tanks are more than adequate for special occasions).
 
whartung said:
bolt an M-Drive to one of these things
Click to expand...
You don't even need to go that far.
"Simple" chemical rockets (liquid or solid) could do the job.

1 minute of 1G acceleration is enough to achieve 18km of separation from launch point (probably sufficient for "100D" from the starship that's jumping for most low end/ACS starships).

Additionally, drop tanks that have been "drained of fuel" won't have a tremendous amount of (now) dry mass, so you wouldn't even need chemical rockets that are all that powerful to "toss away" an expended drop tank in order to get it clear (so it can be reused) prior to actually jumping.
 
Grav_Moped said:
I know what they meant: The ship gets a free hardpoint with respect to its 300Td core hull, because it's built with a 100Td drop tank. I can think of an easy exploit of this, and now that I've stated it this way so can you -- any of you could.

...

On the other hand, reading it literally it indicates that hardpoint is mounted to the tank, and goes away with the rest of the tank when you drop it. I can almost buy off on this, especially if it's a plasma/fusion gun that can double as an ejection rocket...
Click to expand...
No, they really mean that the drop tank get one hardpoint. There are no separate drop tanks, they are just regular subhulls, carried in regular clamps. So, drop tanks gets hardpoints (or firmpoints) just like all other hulls.

As drop tanks are regular hulls any regular system can be installed into them, including e.g. weapons or staterooms.
 
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