All Warships Should Have Drop Tanks

[rancke]

On the one hand you can visualize tankers as simply drop tanks with M-Drives and a bridge. The tanker hard docks to the ship, and the ship starts taking fuel.

There are a number of dodges that OUGHT to work. However, they're all pretty simple to think up, so if they actually worked, someone in the OTU would have done so millenia ago. Hence we must assume that they don't work and invoke our willing suspension of disbelief to avoid thinking about it any more.

The fact that drop tanks use explosive bolts rather than, say, springs or booster rockets or miniature maneuver drives to achieve separation tells us that for whatever reason, it is crucial that separation is achieved in a very short span of time. (It also explains why drop tanks are one-use -- the explosions are aimed away from the ship hull and towards the tanks, shattering them, or at least compromising their integrity).

The other issue with tankers is that for a large fleet, the tanker is a choke point. Basically you need a tanker for each ship so that the fleet can jump at the same time. A jump takes 168 hrs +/- 10%. I assume that when a fleet jumps, they have some coordinated plan that gives them control over that +/- 10% window. Sort of a "we don't know exactly how long it will take, but we know that it will take all of us the same time to get there". Otherwise fleet operations would just be a disaster of ships randomly appearing in system over a 16 (32?) hr window.

There was a Q&A section in an MT publication -- Travellers' Digest, I think -- that said that if you spent a lot of time on the calculations, you could get the variation down to +/- 1% instead of +/- 10%. That would make the window 3½ hours instead of 34 hours. If the variation is distributed along a bell curve, military thought will probably assume that the extremes won't occur, so call it 2 hours instead of 20 hours (guesstimate).

That said, ships can arrive randomly in the system over 2 or 3 or 20 or 34 hours without any problem as long as the attacker doesn't aim for the center of the defending forces. A system is a big place, and there will be no shortage of places that the defender can't possibly cover.

The other question is whether a ship that jumps 1 hr later simply arrives 1 hr later, or is the arrival window based on the exact time of jump, and the greater the time difference between two ships jumping, the wider the window of arrival time.

I believe each jump duration is determined individually for each ship, completely independent of the time and place it takes place. Someone can jump six hours after you and arrive six hours before you.


Hans

 

[Starviking]

Truly a nice idea, if feasible on traveller engineery (I don't know).
I suppose it could be possible by using a logn pile to join the tanker with the ship's fuel system, and just detaching the pipe before the jump (as you whould do with drop tanks) so maintaining hth right distance as not to interfere with the jump (it can need quite a lot of coordination, but too much more than mooring the space shuttle to the space station, and we can do that at TL7-8).
Whorth thinking about...

A long pipe will likely cause serious problems itself - there will probably be turbulence in the flow of the hydrogen at the rates needed to fuel a jump. That would cause variation in the rate of H2 delivery to the jump drive, which I assume would be a no-no for safe jumping.

 

[Starviking]

On the one hand you can visualize tankers as simply drop tanks with M-Drives and a bridge. The tanker hard docks to the ship, and the ship starts taking fuel.

Why not just have the tanker's fuel tankage as drop tanks? They'd need specialised equipment to transfer the tanks to the jumping ship, but after it jumps they can retrieve the tanks and go and top-up - ready for the next ship (that is if drop tanks can be re-used).

 

[Starviking]

There are a number of dodges that OUGHT to work. However, they're all pretty simple to think up, so if they actually worked, someone in the OTU would have done so millenia ago. Hence we must assume that they don't work and invoke our willing suspension of disbelief to avoid thinking about it any more.

And that is the key point of the argument.

The fact that drop tanks use explosive bolts rather than, say, springs or booster rockets or miniature maneuver drives to achieve separation tells us that for whatever reason, it is crucial that separation is achieved in a very short span of time. (It also explains why drop tanks are one-use -- the explosions are aimed away from the ship hull and towards the tanks, shattering them, or at least compromising their integrity).

Explosive bolts aren't particularly dangerous - the explosive in question is just enough to break the bolt holding the two sections together, see http://en.wikipedia.org/wiki/Pyrotechnic_fastener

I would, and have argued that separation must be achieved quickly, in order to clear the drop tank's 100 diameter limit. The explosive bolts would seem to be there in order to assure (at least) initial separation - a non-dropped tank is what caused the Trimkana Brillance disaster after all. We can assume that plotting a higher jump than a ship can achieve on it's current displacement can prove disastrous.

There seems to be a few key facts which we need to establish in order to muse further about drop tanks and jump tankers (at least to keep the discussion OTU) - how quickly does a ship consume fuel prior to jumping? Can a jump be put on hold after the fuel is burnt or whilst the fuel is being burn? Why are drop tanks TL-14? I'm sure there are more.

 

[PFVA63]

Hi

Here is an additional plan view, of the 600 dton Escort Frigate (on the left), showing how three 80 dton tanks could be fitted below it, as well as (my best attempt at) a profile view of the ~1000 dton Destroyer Escort - Convoy Variant (on the right). There wasn't really enough info in the "Traders & Gunboats" book for me to guess at what the profile of the Escort Frigate r the Colonial Cruiser might look like, but the images and deck plans for the DE-CV were reasonable consistent enough for me to sketch up the image below.

Two issues that are not fully clear though are the thickness of the hull plating, especially above and below a deck, and the layout of the engine nacelle type areas. The deck plans show them as only two decks tall (as shown below) but the image in the book kind of makes them look taller (maybe two and a half to three decks tall).

As such, the profile right now is mostly an initial guess.

The little hemispherical shapes on the DE-CV represent some of the turrets on the ship and you can see how the tanks may block the arcs for some of them. There are actually supposed to be ten turrets on this ship, but I could only locate nine in the deck plans. Additionally if the nacelles are deeper than two decks the turrets on the bottom of those would be even lower and the tanks may have to be lowered to compensate.

Regards

PF

 

[PFVA63]

Hi

On the topic of drop tanks, a couple other thoughts have recently crossed my mind. Specifically, recently I read somewhere (maybe even somewhere in this thread, I can't remember) that its kind of typical for merchant ships to more or less come to a stop in real space before jumping into jump space, so that when they exit jump space at the other end they have zero forward velocity in real space there, making it easier (hopefully) to avoid any unforeseen obstacles at the other end. However, the same article noted that for warships it may be more typical to leave real space with some forward speed so that when you exit jump space at the other end you still have forward velocity, which may be tactically advantages for a warship.

In such a situation, with drop tanks, a couple thoughts come to mind. First, since having drop tanks attached in real space reduces you maneuver ability, the capability of getting up to high speeds with them attached is reduced. As such, when exiting jump space a warship may not have the same potential benefits of a high exit speed that a ship that didn't use drop tanks would.

Secondly, if the ship using drop tanks is moving at some velocity in real space before entering jump, then those tanks will also have a similar velocity when discarded, which may make collecting them a bit more challenging, especially if alot of ships are jumping.

Additionally, the though also crossed my mind that if its possible to enter jump space with tanks attached (say for the purpose of transporting them to a new system, etc), then what's to stop some player fro wanted to keep them attached but instead use them as additional cargo space. Admittedly, maneuver and jump performance will of course decrease for a ship, but it may be one of those situations where the extra cargo capacity makes its worth while. And, along a similar note, this could also open up a line for argument by some players that they should be allowed to strap anything that they want to the outside of their ship as long as they assume the maneuver and jump performance of the fully burdened vessel.

In my mind then, unless there is some sort of balance in the system, drop tanks could open the door to arguments for alot of changes in the basic way Traveller works. I suppose that arguments could be made that the drop tanks need a Lanthanum grid to be carried while jumping, but I'm not sure that the current design and cost rules reflect that, or that all vessels/rules sets are based on the use of Lanthanum grids.

Anyway, just some more stuff to ponder.

Regards

PF

 

[Spike]

Regarding using them as external cargo: At least in MongT there are rules for external cargo mounts and cargo ships using external cargo mounts (a more sensible design for fuel tankers, btw: save a fortune in hull costs and you can theorize that each external fuel pod could simultaniously fuel a seperate ship)

Thus: Using a 'drop tank' mount to bolt on a cargo box... or converting an attached drop tank into a cargo box directly, would be allowable, if not exceptionally wise or practical in my view.

 

[Dragoner]

The fact of how they are dropped, which 1) they will retained their intial velocity but 2) they actually need some sort of retro-rockets to clear the craft as gravity will not pull them to the ground or even away; the explosive bolts would be just to positively detach the fitting. So drop tanks become actually complex machinery, not just simple tanks; adding to this the need to pick them up so as for them not to become a hazard to navigation, this adds more complexity.

Tankers seem more useful in the long run, but I wonder how the tankers are to be made, certainly not as complex as a warship.

 

[robject]

[...] 1) they [retain] their intial velocity [and] 2) they actually need some sort of retro-rockets to clear the craft as gravity will not pull them to the ground or even away; the explosive bolts would be just to positively detach the fitting. [...]

This meshes with how I read drop tanks: most suffer a jump mishap due to being close to a jumping ship; most are destroyed.

 

[Dragoner]

I'm curious though to the meaning of destroyed; ie totally disintegrated or just damaged beyond repair. Looking at the schematics posted, they are fairly large objects.

 

[far-trader]

I'm curious though to the meaning of destroyed; ie totally disintegrated or just damaged beyond repair. Looking at the schematics posted, they are fairly large objects.

Large yes, but quite fragile and weak compared to even unarmoured hull material, going by cost. Think disposable, not reusable.

I think at the price in most rule sets they should be restricted to single use, low or no g while attached, no jump possible with them attached*, no value when recovered beyond scrap (think sucked down so fast they partially implode) and that not worth the time for dealers so you have to pay a recovery fee to use them. Oh, and an increased risk of misjump when using them of course. With those and possibly some other restrictions on them I might see them allowable in my TU

As they are, as attested to by this thread and many similar, they open up a huge can of worms that invalidate whole swaths of the OTU if they exist there and beg for scads of new applications of the idea. They really weren't properly or fully thought out imo. Or it was left to the ref to nerf them so they don't wreck the OTU or ATU they get dropped into.

* especially so if your TU is one that uses the jump grid explanation since again, at the price typically applied, they aren't likely to have a jump grid included

 

[Starviking]

This meshes with how I read drop tanks: most suffer a jump mishap due to being close to a jumping ship; most are destroyed.

Ah, but whilst we know that a ship jumping from a position within 100 diameter of another object can cause a misjump - is there anything in canon about it being dangerous to be too close to a jumping ship?

 

[aramis]

I'm curious though to the meaning of destroyed; ie totally disintegrated or just damaged beyond repair. Looking at the schematics posted, they are fairly large objects.

Based upon T5, Rendered into 10cm or smaller pieces, and maybe 60% of mass remaining (the rest being lost into jumpspace).

 

[far-trader]

Based upon T5, Rendered into 10cm or smaller pieces, and maybe 60% of mass remaining (the rest being lost into jumpspace).

That seems to hint at a (return to?) disposable single use only

Might I beg an answer to can you not jump with it attached in T5? That alone would probably make it less TU wrecking, affecting only the slightly broken Gazelle class And that only in that it couldn't jump with the drop tanks attached which was a limited utility anyway.

 

[McPerth]

I think at the price in most rule sets they should be restricted to single use, low or g while attached, no jump possible with them attached

In HG and JTAS 4, the Gazelle CE is told as usualy jump with its drop tanks attached, with a performance J4 M4, while without them just J2 (for lack of fuel) or J5 if droping them just before jump.

 

[aramis]

That seems to hint at a (return to?) disposable single use only

Might I beg an answer to can you jump with it attached in T5? That alone would probably make it less TU wrecking, affecting only the slightly broken Gazelle class And that only in that it couldn't jump with the drop tanks attached which was a limited utility anyway.

yes, you can.

 

[far-trader]

yes, you can.

So if I read you correctly and my confusing poorly worded question above didn't cause more confusion in your answer, then T5 does allow jumping with drop tanks attached. Pity.

I realized from your answer that I worded my question above poorly and probably confused the issue and I've just edited it. I intended that not being allowed to jump with tinfoil drop tanks attached would go a long way to making them less canon destructive, and imo at least much more sensible.

 

[Selandia]

Why not just have the tanker's fuel tankage as drop tanks? They'd need specialised equipment to transfer the tanks to the jumping ship, but after it jumps they can retrieve the tanks and go and top-up - ready for the next ship (that is if drop tanks can be re-used).

If the drop tanks could be re-used, indeed. The tankers you refering to become a cross between Fleet Replenishment Ships and Repair Ships. You can position such tankers at "Coaling station" and keep your logistic alive using Jump Tugs along a chain of stations that do not even need bases or yards, only ferry tankers to run between your FRS and the gaz giant The whole @#$% thing become even more broken for it provide rational to explain why there is 0 fitting time, 0 yard time used, perpetual availability of tanks and fitting personnels, tools and equipment near the jump point and get out of the hands of the referee any attempt to keep a lid on it. Mind you, in TCS Bases are free (unless you consider them priced in the maintenance cost), so why not consider a endless supply of free repair/supply ship

A ton of hull space for fuel is 100,000 Cr
A ton of drop tank is 1,000 Cr + 10,000 per tanks (plus fuel itself, of course)
On merchant ships (no armor needed), only fools would buy fuel hull space 100 time the price of drop tanks given the fact (see Gazelle) that drop tanks can be kept attached for years through jumps.
Yet somehow, no OTU merchant design substituted them to conventionnal tankage ???? MTU rationalisation a posteriori of that OTU Deux Ex Machina: you still need a basic tankage to back fill from

Why Jump tankers beat L-Hyd (provided Jump tankers are real ships that speed away the 100 diameter limit) IF tanks are one use WHEN tanks are dropped?

Because a ship like a Jump Tug will make about 1600 commercial jumps in a 40 years lifespan (1 jump every 8 days, allowing maintenance and some repositionning jumps), even if the drop tank is 100 x cheaper per ton, does not have to pay for MD-1, PP-1, Bridge, lowest possible computer and accomodation, and have 0 incidental cost or troubles, the Jump Tanker end up cheaper than L-Hyd drop tanks if they are to be used as a standard operating feature of a trade route (or fleet logistic tail). Of course, if tanks can be recovered and refilled at no cost other than fuelo::devil:

Of course, if your Gazelle or a "fleet despatch ship" drop the tanks three times a years for an extra long panic jump, you are better of with tanks, specially if you do not loose hard points when droping the tanks :devil:.

Selandia

 

[Theophilus]

I never expected this thing to go over 200 posts. Still, many great points are being brought up. And some new "rules" as well.

First, we need to be careful what Rule set we are refering to. CT, MT, TNE, T4, GT, MgT, T20 etc. since each has separate "rules" which may conflict.
Secondly: even in a rule set, various publishers made up different rules, that is, in CT both GDW and DGP produces "rules" concerning Jump and how it all work's.
Some of which contradicted each other, so let's try to "quote" rules set and publisher when possible.

For example, the discussion on "explosive bolts to detach tank", from which rules set? or just a house rule?

Here's some info from Trillion Credit Squadron:
Page 13, Fuel tankage:
"Other types of Fuel Tankage: There are four varieties of fuel tankage which are not integral to a ship, each with advantages and disadvantages. These are collapsable tanks, demountable tanks, exterior demountable tanks, and drop tanks. These may be added to any ship at any time, and may be added to any ship for TCS provided the cost is paid."
"Drop tanks: (pg14) The disposable tank rule (Book 5, Page 27) allows the construction of tanks which can be dropped from the ship. The reduced ship tonnage, combined with the higher resulting capacity of the ship's drives, can result in increased jump number or maneuver drive number. Power Plant number may increase, but it's energy output remains the same.
When a ship is produced with drop tanks, the total tonnage of the ship without drop tanks determines the number of weapons allowed.
Drop tanks may be built onto a ship when it is originally produced at a cost of Cr10,000: they may be added to an existing ship at a cost of Cr1000 per ton. In both cases the tanks themselves must also be produced at Cr1000 per ton. Building time is 10 weeks: installation time is only a few minutes."

No where in CT, MT, or TNE have I seen references to a "Jump Fuel Tanker" as an external fuel source. However, the Tankers pictured in FSOSI (a very broken product) had long fueling "boom's", which would seem to be the only practical way to refuel. Might I make a suggestion, the fuel fittings from the drop tank entry, at Cr10000 for drop tanks, should also be used for tankers, and thus be placed on any design using tankers or drop tanks to allow a ship to fuel/refuel. Thus a ship may have either Fuel Scoops, External Fueling coupling's or both.

Now concerning Drop tanks only being available at TL14: There are no TL14 worlds in the Island clusters campaign, yet there are rules for drop tanks. Why? There is no reference to Drop tank TL in CT, MT or TNE.

For a moment I would like to consider the statements concerning "there are no designs for drop tank ships, therefore it must not work and can't be done." or such like.
First off, if it can't be done, why have drop tank rules in various rules books and in all the different rules sets? If the rule for use is in the books, it is up to us to figure out how to use the rule. (thus this thread) Obviously there is more to Jump Fuel, and Jumping than just going from hex to hex on a map. Since there are no tanker designs in CT, or TNE then I should infer that Tankers won't work under those rules sets! Obviously not, since there are references to tankers and other fleet auxillaries.

In TNE there are references to deep space refueling caches. Would this be tankers or pre-positioned tanks, either demountable, drop, or fuel bladders. I can't see tankers sitting for years on end waiting to refuel a ship, or building "deep space" stations to hold fuel when a few tanks detached from a tender and left to "drift" would fill the same need.

Just a few more thoughts to add to the mix.
Just a few more thoughts to add to the mix.

 

[Dragoner]

Based upon T5, Rendered into 10cm or smaller pieces, and maybe 60% of mass remaining (the rest being lost into jumpspace).

This here then (to me at least) tells me that the military will not use drop tanks regularly as it would create a chaff cloud. This cloud ala cigarette butts, would be a signature that would give away fleet operations,; an enemy scout being able to pop in and analyze the chaff to be able to estimate what, when, where and how many ships passed through an area.

Also it lights up my OCD (I blame engineering school), that the chaff cloud would be a hazard to navigation (imtu ships all have a minor repulsor field to keep things like the paint chip that cracked a shuttles windscreen from happening) and positively no EVA in chaff.

Thus external tanks only on recon and couriers as Selandia supposed, bigger/capital ships will use strategic tankers.