Alternative to drop tanks

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baithammer
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Re: Alternative to drop tanks

Postby baithammer » Tue Apr 30, 2019 2:52 am

Drop tanks were never supposed to be about being economical, but to allow for extending operational range.
HalC
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Re: Alternative to drop tanks

Postby HalC » Tue Apr 30, 2019 4:17 am

Note too - that despite drop tanks being introduced in Traveller in the early years, few ships ever used the Drop Tank per any of the supplements that were put out. Off hand (and I'll bet I'm wrong since I don't have ALL of the books from ALL of the systems to be sure!!!) - I can only think of one ship that has drop tanks in its design. That of course is the 300/400 dTon Gazelle
PsiTraveller
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Re: Alternative to drop tanks

Postby PsiTraveller » Tue Apr 30, 2019 8:15 pm

Extending range has to be somewhat economical or in the realm of feasibility. If a 1000 ton J4 ship was costing 10 million credits per jump it would not take many jumps to have high command buy an extra ship or two. (25 000 per ton @400 tons)

The L Hyd tanks cost 200 000 per ton, which is even worse by a factor of 8.
baithammer
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Re: Alternative to drop tanks

Postby baithammer » Tue Apr 30, 2019 9:03 pm

PsiTraveller wrote:
Tue Apr 30, 2019 8:15 pm
Extending range has to be somewhat economical or in the realm of feasibility. If a 1000 ton J4 ship was costing 10 million credits per jump it would not take many jumps to have high command buy an extra ship or two. (25 000 per ton @400 tons)

The L Hyd tanks cost 200 000 per ton, which is even worse by a factor of 8.
Only for merchants, the military has a higher priority on capability. ( If they can get the politicians to fund it.)
Condottiere
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Re: Alternative to drop tanks

Postby Condottiere » Wed May 01, 2019 5:28 am

They're subsidiary hulls, and bunkerage by default is technically free, beyond just calculating raw tonnage.

Then add clamps, explosive bolts, and plumbing.
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Re: Alternative to drop tanks

Postby Linwood » Wed May 01, 2019 10:49 am

Should we look at drop tanks as breakaway hulls then?
phavoc
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Re: Alternative to drop tanks

Postby phavoc » Wed May 01, 2019 3:28 pm

I would not treat a drop tank as a breakaway hull item unless you build and price it as hull.

Drop tanks by design should be cheap and disposable since they are meant to be disposed of when no longer needed.

Personally I don't think the current idea of drop tanks was very well thought out. And the book designs do not take advantage of them when they have some very clear advantages, which leads me to feel they should not be used as written.

Which, I think, means they should be more along the lines of breakaway hulls instead of drop tanks. The Gazelle class ship really has more of conformable fuel tanks than drop tanks. But we have to be careful of the aerial equivalent analogies.
Condottiere
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Re: Alternative to drop tanks

Postby Condottiere » Wed May 01, 2019 4:23 pm

Streamline them and they become conformal.

The difference between breaking away and dropping off are the explosive bolts, which means that the drop off needs to be sudden.

This is another case of a legacy trying to be shoved in to fit whatever the current, doctrine, is.
baithammer
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Re: Alternative to drop tanks

Postby baithammer » Wed May 01, 2019 5:00 pm

Linwood wrote:
Wed May 01, 2019 10:49 am
Should we look at drop tanks as breakaway hulls then?
Breakaway hulls require their own power source and bridge at the bare minimum.
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Re: Alternative to drop tanks

Postby HalC » Wed May 01, 2019 5:26 pm

As pointed out, the idea about drop tanks seems to have issues, but why not examine the practice to see what is involved?

What happens when we have an enemy fighter of 10 dTons nearby when a ship attempts to jump away? Anything? Ok, let's turn it into a 40 dTon boat instead of even a 50 dTon cutter? Exactly how far away does a drop tank need to be before it is no longer an issue? Can a 5,000 dTon destroyer inhibit any other ship's jump just by being within some arbitrary zone of distance of the jumping ship?

Let's say that we have satisfactory answers to all of that - the laws of physics are such that we can estimate the force required to move a given mass a given distance. It shouldn't be all that difficult to either confirm the possibilities as viable or not right? But let's take a moment to think outside the box...

What if those tanks, instead of being propelled by explosive bolts, was instead, powered by battery powered reactionless motors instead? What if the tanks were made with bonded superdense material instead of cheap materials? What if, to borrow another aviation metaphor, we used a drogue like approach and used a high pressure fuel hose to feed into a specially designed fuel intake valve and permit the fuel tanker to cut the line just as the jumping ship is accelerating away for its jump? In other words, the jumping ship need only be outside the so called danger zone when it finally jumps.

CT concepts have evolved over time. It used to be that there was only the entrance into Jumpspace and exit from Jumpspace that mattered. If a craft was within 100 diameters of a body, it could impact on the transition into Jumpspace. Why should anything change with the advent of drop tanks? Why not simply set the rules to where either the tanks are far enough away or they aren't?

Imagine self-propelled tanks such that they have 6G's of acceleration, contain 80% of a ship's hydrogen fuel needs to jump, and were all battery powered. No fusion power plants, no bridge requirements, no life support requirements - just boosters for jumps?

Me? I'm not a fan. But if they are to be a part of the game universe, at least make the rules internally self-consistent so that we can't build other forms of jump boosters, which is really all drop tanks are. They permit the drop tank users to temporarily increase volume without the volume being counted at the moment the ship enters Jumpspace.
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Re: Alternative to drop tanks

Postby phavoc » Wed May 01, 2019 6:17 pm

For that matter you don't even need batteries or a power source for the jump drive. Super-conducting cables could be used to transfer power to the ship that is jumping to power the jump drive.

If you can have collapsible fuel bladders then you could place them outside the ship and the would collapse as you pulled the fuel from them to generate your jump bubble (since we have no specifics on how fast this takes, it's reasonably fair to say you could have an open cargo hold with the base of the collapsible tank sticking out, and as you are powering up your jump field the tank is contracting as you vacuum out the Lhyd, thus you maintain equilibrium till the bubble is fully formed and tank complete empty.)

This is also not consistent with any of the published designs but it would fit within the existing explanations.

Which is why as HalC points out, internal consistency across the design system is important. Otherwise there is no point to have any rules as pretty much anything is acceptable (and that's not how reality or gaming systems should work).
baithammer
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Re: Alternative to drop tanks

Postby baithammer » Wed May 01, 2019 7:40 pm

Travellers mainbook and high guard have the rules.

1.) A ship can jump if no objects of a size greater than the ship are within 100 diameters of the ship.
2.) Anything smaller than the ship is destroyed or damaged by the expanding jump bubble. ( Inferred by drop tank rules)

Bladders don't contain any pumping equipment, so can't fuel the jump directly. ( Which is where drop tanks come in.)
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Re: Alternative to drop tanks

Postby phavoc » Wed May 01, 2019 8:33 pm

You don't need any internal pumping equipment in a bladder for it to work (Lhyd requires low temperatures and pressure to say liquified). A simple vacuum pump can suck it dry while transferring to the main tanks or elsewhere with no issue and no loss in fuel transfer time. This is no different than current designs with ships fuel in tanks places in various places around the ship.
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Re: Alternative to drop tanks

Postby baithammer » Wed May 01, 2019 8:38 pm

phavoc wrote:
Wed May 01, 2019 8:33 pm
You don't need any internal pumping equipment in a bladder for it to work (Lhyd requires low temperatures and pressure to say liquified). A simple vacuum pump can suck it dry while transferring to the main tanks or elsewhere with no issue and no loss in fuel transfer time. This is no different than current designs with ships fuel in tanks places in various places around the ship.
Ship tanks include the pumping gear, bladders don't. ( They are meant as a cheap knock down extension of fuel supply and not a replacement for tanks.)
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Re: Alternative to drop tanks

Postby phavoc » Thu May 02, 2019 2:18 am

Adding a pump is very easy. Or, failing that, just connect the bladder to the system.

This is very easily done using even today's tech.
baithammer
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Re: Alternative to drop tanks

Postby baithammer » Thu May 02, 2019 4:31 am

Or just use Dedicated fuel/cargo containers from DSE handbook.
Condottiere
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Re: Alternative to drop tanks

Postby Condottiere » Thu May 02, 2019 8:02 am

I think I've explored most options regarding bunkerage ages ago.

If I wanted to game the system, I'd place a piston wall at one end of the fuel tank; as the fuel tank empties, the wall closes and the tank is exposed to space.
Annatar Giftbringer
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Re: Alternative to drop tanks

Postby Annatar Giftbringer » Sun May 05, 2019 6:02 pm

HalC wrote:
Fri Apr 26, 2019 9:17 pm
Annatar Giftbringer wrote:
Fri Apr 26, 2019 10:59 am
The Traveller Companion has a chapter on gas giant operations and fuel skimming.
Alas - without a job - not a viable option.
I’ll try to summarize the chapter below:

Gas giants are divided into layers. The deeper you go, the thicker the atmosphere (obviously!). There are rules for how sensors and beam weapons are affected by the layers, as well as how to travel between them. It also gets increasingly difficult to manoeuver your ship the deeper you go.

Fuel skimming is done in passes. A single pass lets a ship fill 1% of its tonnage and typically takes 2D6 minutes, modified by current layer density. Staying in the shallow layers means refueling takes longer, but it’s also safer.

Thanks to how the layers interfere with sensors and weapons, it’s possible to play hide and seek within gas giants, kinda like submarine warfare.
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Re: Alternative to drop tanks

Postby HalC » Sun May 05, 2019 7:26 pm

Thank you for the sneak peek Annatar, I could almost HATE you for that... *teasing grin*


I owe my wife a steak dinner with my first paycheck assuming I get the job I'm hoping to get (just completed an interview! Yee Haw!). I'm permitted to spend some money on Traveller Stuff with the second check, but bills have to be paid down as you might imagine (that and repairs after a particularly nasty wind did some shingle damage!).

Now there are THREE things I'm going to want to pick up from MgT (despite my not playing it as a rule). A good idea is a good idea, and the Companion sounds like it has a few good ideas here or there. ;)

As it stands now? My collection of MgT material is up to 9 books. Time will tell what I end up picking up over time. Thank you for the kindness in sharing a glimpse into the product, as that does whet the appetite a little. You should get a commission for the sale if I do end up buying it.

;)
Annatar Giftbringer
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Re: Alternative to drop tanks

Postby Annatar Giftbringer » Mon May 06, 2019 6:36 pm

Haha, I assure you there were no cruel intentions behind the preview, I merely wished to give you a glimpse of what the book says on the matter :)

Dinner and bills first sound like a very sensible plan, good luck on the job front! Yes, I'd say that the Companion is basically a huge collection of good ideas. Most chapters are quite short (the gas giant chapter is just three pages, for example) but in return there are a lot of them, and while one might choose not to use all of the additional rules and ideas just having them available if or when the situation arises can be a good thing :)

Out of curiosity, what are the other two things you want/need?

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