Refueling the fleet

[Carlobrand]

I continue to explore ideas for a High-Guard-based FFW campaign (which is going to require some modification of High Guard to suit the milieu assumptions, but that's a different issue). I'm looking now at refueling.

Under TCS, a squadron is streamlined if at least half its fuel tankage is in streamlined ships/boats, partially streamlined if at least half its fuel tankage is in partially streamlined ships/boats, unstreamlined otherwise. An unstreamlined squadron may refuel from a gas giant as long as 10% of its fuel tankage is in streamlined or partially streamlined ships/boats, from a world's water as long as 10% of its fuel tankage is in streamlined ships/boats.

Also in TCS, it takes 7 turns (140 minutes) for a streamlined or partially streamlined ship to scoop a full fuel tank from a gas giant, and 2 turns (40 minutes) to transfer the full load of fuel to another ship. Ergo, a streamlined or partially streamlined squadron can refuel from a gas giant in a little under 6 hours - two trips. An unstreamlined squadron with at least 10% of its fuel tankage in streamlined or partially streamlined ships/boats can refuel from a gas giant in a little under 30 hours - ten trips.

This is consistent with statements about refueling in AHL. Also in AHL, it takes twice as long (6 hours) for a streamlined or partially streamlined ship to scoop and transfer a full fuel tank from a the oceans of a water-bearing world. (Specifics not mentioned, but I'm figuring ~4 turns/80 minutes for the descent, ~8 turns/160 minutes for the scoop, ~4 turns/80 minutes for the ascent, 2 turns/40 minutes for the transfer - however it's mostly irrelevant).

Ergo, a streamlined squadron can refuel from a water-bearing world in a little under 12 hours. A partially streamlined or unstreamlined squadron with at least 10% of its fuel tankage in streamlined ships/boats can refuel from a water-bearing world in a little under 60 hours (2 1/2 days).

Fifth Frontier War permits an unstreamlined squadron to refuel from an ocean or gas giant in one week, presumably using boats or ships of the appropriate type. On the week-long turn basis, the fleet has a week (168 hours, 504 turns) to pull this off - 56 trips through the gas giant, 28 down to the water world and back. Ergo, with relief crews, an unstreamlined fleet ought to be able to refuel in a week given about 1.8% of tankage in streamlined/partially streamlined fuel scoopers at a gas giant and 3.6% for streamlined fuel scoopers at a water world. Ergo, if at least 4% of the squadron's tankage is in streamlined craft, it should be able to refuel pretty much anywhere, albeit at a slow rate.

A battle squadron of 8 200kt J4 DNs has about 100kt in fuel tankage. It needs streamlined support ships with ~4 kt in fuel tankage to meet that minimum. That can be satisfied by a mix of roughly 8kt of streamlined J4 auxiliary ships including escorts - maybe 6 to 8 streamlined destroyer-escorts. Ergo, we move to a 4-5% mark instead of TCS's 10% mark.

Now the fun part:

Given the plentiful supply of alternative hydrogen sources in any given system - ice asteroids, cometary bodies, ice-bearing outer system moons, Pluto-like ice-bearing Kuiper-belt dwarf planets and their moons 30-50 AU out - it may be advisable to allow all craft to refuel in one week at any system. It's in the form of hydrocarbon ices, but these can be processed to free the hydrogen, and a navy is certainly going to equip its ships for that alternative.

As any interstellar government is likely to know the orbital details of any known system's bodies - at least to the extent of picking out a few candidates for such refueling - finding such sources presents no problem. Hoowever, refueling from them would be more involved than simple scooping - frozen ices would have to be mined, then melted and their hydrogen component broken free of whatever chemical it was in. Warships could be expected to carry the necessary equipment, and purification plants would probably be able to handle melting the ices and breaking out the hydrogen, but merchants most likely would not unless someone's made a deliberate effort to purchase and install the equipment.

And then of course there's the starports. I've gotta give them some thought.

Say - for consistency's sake only - it takes a week for any ship equipped with a purification plant to mine ices and convert them into fuel; streamlining is irrelevant as the candidate bodies will have no atmosphere to speak of and little gravity. Ice moons and ice asteroids within a couple of days flight of a system's primary will be carefully watched; if the system has defenders, someone refueling from those sources may be engaged by the defenders before they can complete refueling. Cometary bodies and Kuiper dwarf planets are 4.5 to 7.5 billion kilometers out or more - roughly a week's flight at 4-6 G. These bodies can be jumped to directly or maneuvered to from the inner system in about a week, after which it takes another week to mine fuel.

So, a fleet seeking to avoid contact could do so by spending a week in the Kuiper belt of every system on the route; defenders could not reach him before he refueled and moved on. However, he would be slow, a likely strategic disadvantage. For game balance purposes, we will assume the adversaries have systemwide sensing capabilities sufficient to tell them that someone is out in the far reaches of the system (else the adversaries would be able to establish refueling bases wherever they wanted), but not sufficient to give them details of the force beyond a vague idea of numbers - a couple, a few, or many. They also have sufficient scouts and couriers scattered about to monitor their less settled systems and to report movements back to some nearby naval base.

Likewise, a fleet passing through a system with neither a gas giant nor a water world could spend a week refueling at whatever ice body was handy - again, it's slower, but it prevents the issue of fleets getting stranded when there are ample alternative hydrogen sources.

And, a defeated fleet without fuel for jump could disengage to the outer system, spending a week to get to the Kuiper belt, then spending another week refueling.

 

[McPerth]

A battle squadron of 8 200kt J4 DNs has about 100kt in fuel tankage.

Just a point here, as I think your numbers are wrong:

your 8 200 kdt J4 DNs sum a total tonnage of 1600 kdt. Just jump fuel will amount 40% of it, so 640 kdt of fuel, and to this we must add PP and subordinate craft fuel...

And now some ideas:

About ocean refuelling:

As I see it, the best way to ocean refuelling a ship though subordinate crafts (as the shuttles the AHL has) would be to just take the watoer to orbit and transfer the hydrogen as you electrolize it. The electrolisis time will be in orbit, so being less vulnerable (they can undock at any time), and also the hydrogen so caried in every trip will be about 55% more (18 kl to take 2 tons, instead of needing 28 kl). Oxigen can be vented to space. Of course, the downside is having to deal with impurities (e.g. salt) the water may have, that should be downloaded in the next trip.

About comet (et al) refuelling:

As mining the ice will take time, and then has to be electrolized, etc., personally I'll allow it but taking double time than ocean refuelling (so allowing to so refuelling in 2 weeks, instead of 1), unless special designed ships (mining/refinery ships) are with the fleet, allowing a fixed amount of fuel to be mined/cracked/purified by each such ships per week.

Hope that helps

 

[Matt123]

Consider also "empty" hexes beside strategically important ones. These may be used to create fuel depots, to allow raids with the capability to jump back out to safety. If it is a concern to the defender, they need watching by jump capable craft. It might not stop the initial raid, but at least you will know where they are retreating to.

Empty hexes may also have loose hydrogen floating about & available for mining. I've always assumed enough for PC scale craft if they really have to.

 

[McPerth]

IMHO, this hydrogen in empty hexes is good for player scale ships (and a good way to take them out of a musjump problem), but I have serious doubst it will be enough for a fleet scale mission, and no Aldmiral will rely on them unless laready located and pinpointed (and probably a mining/refinery squadron sent in advance).

Of course, for the strategic game Carlobrand seems to be planning, having each side to know some of those fuel sources may be interesting (and if the same fuel source is known by both sides, it may lead to interesting situations...:devil.

 

[aramis]

Keep in mind: that empty hex hydrogen is likely to be solid ices at -270°C to -220°C (3°K to 53°K) - cold enough to render most non-specialized means of gathering rather hazardous.

 

[Enoki]

As a possible twist to this you could have refueling plants, particularly on smaller ships, that have specific requirements for what types of molecule can be used for refueling. That is, a plant could convert say water but not ammonia or methane to fuel, or some other combination like that. This would mean that not all gas giants and other potential fuel sources are equal in desirability or even potential as a fuel source.

 

[Matt123]

As a possible twist to this you could have refueling plants, particularly on smaller ships, that have specific requirements for what types of molecule can be used for refueling. That is, a plant could convert say water but not ammonia or methane to fuel, or some other combination like that. This would mean that not all gas giants and other potential fuel sources are equal in desirability or even potential as a fuel source.

Interesting thought. Is the differance in methods & equipment needed, enough to warrant specialised ships at say TL11+. (I'm not a scientist!)

 

[Enoki]

Interesting thought. Is the differance in methods & equipment needed, enough to warrant specialised ships at say TL11+. (I'm not a scientist!)

I'd think so. Water is usually broken down by electrolysis into its components for example. Methane and other hydrocarbons are usually cracked with heat first. Methane is also volitle in an atmosphere (like inside a ship) and a gas while water would be a non-flammable liquid.
Then we have ammonia. It could be a liquid or gas and is non-flammable too. If the ship required nitrogen for pressurizing various tanks and such the absence of nitrogen in methane and water would be a problem while the absence of oxygen in ammonia would likewise cause problems if oxygen for breathing etc., was required.
You also would have to deal with waste products like carbon in the case of methane. Would the carbon be bound with something else as a gas or would it be a solid like lampblack?
Then there could be additional problems with mixed gasses that required some sort of seperation process first. Let's say you have a methane-ammonia atmosphere going. You can use the ammonia but not the methane. You have to get that out of the way before you can refine the ammonia.

 

[HG_B]

As a possible twist to this you could have refueling plants, particularly on smaller ships, that have specific requirements for what types of molecule can be used for refueling. That is, a plant could convert say water but not ammonia or methane to fuel, or some other combination like that. This would mean that not all gas giants and other potential fuel sources are equal in desirability or even potential as a fuel source.

Standard ship purif plants can handle GG's & ocean refueling (H2O). So, they should be able to handle any of the above.

 

[Carlobrand]

Just a point here, as I think your numbers are wrong:

your 8 200 kdt J4 DNs sum a total tonnage of 1600 kdt. Just jump fuel will amount 40% of it, so 640 kdt of fuel, and to this we must add PP and subordinate craft fuel...

Oh yeah, my numbers are way wrong. Boneheaded mistake. I'd intended 100 kt/ship, then got lost in the fog of a late-night post. I should've realized something was off: in the squadron I designed, there were 8 DEs and 24 ~1000 dT auxiliaries, mainly high-speed transports carrying missiles and other supplies, that served the need. However, I was planning squadron design for a later post.

And now some ideas:

About ocean refuelling:

As I see it, the best way to ocean refuelling a ship though subordinate crafts (as the shuttles the AHL has) would be to just take the watoer to orbit and transfer the hydrogen as you electrolize it. The electrolisis time will be in orbit, so being less vulnerable (they can undock at any time), and also the hydrogen so caried in every trip will be about 55% more (18 kl to take 2 tons, instead of needing 28 kl). Oxigen can be vented to space. Of course, the downside is having to deal with impurities (e.g. salt) the water may have, that should be downloaded in the next trip.

Interesting thought, but I'm not real keen on taking seawater into the l-hyd tanks. In my view, they'd need to be cleaned after an operation like that before I'd put liquid hydrogen in there again. I'm not sure how tanks would handle having water ice mixed in with the liquid hydrogen, and if a bit of helium from unrefined fuel is problematic, I don't want to think about salt getting into the jump reactor or its fuel lines. That leaves the scooping ship unable to fuel those tanks, and unable to jump, until they were cleaned and refilled.

Under FFW rules, water refueling can only occur at controlled worlds, so time on the surface isn't an issue - plenty of time to crack the fuel on the surface rather than having to clean tanks in orbit. Doesn't do to lose your fueler to an artillery barrage or a grav-tank attack.

About comet (et al) refuelling:

As mining the ice wil ltake time, and then has to be electrolized, etc., personally I'll allow it but taking double time than ocean refuelling (so allowing to so refuelling in 2 weeks, instead of 1), unless special designed ships (mining/refinery ships) are with the fleet, allowing a fixed amount of fuel to be mined/cracked/purified by each such ships per week.

Hope that helps

There's no need for streamlining to set down on a body in vacuum, so any ship could set down. Thus, while it takes more time, I'm thinking any ship with a purification plant has the necessary equipment and can do it, so you're not depending on a few ships to supply everyone.

Also, I'm not sure if all the various hydrocarbons are subject to electrolysis. I was thinking the purification plant subjected them to intense heat - maybe by piping them through pipes threading through the fusion plant - then separated the hydrogen from the other gases and dumped the waste to space.

Consider also "empty" hexes beside strategically important ones. These may be used to create fuel depots, to allow raids with the capability to jump back out to safety. If it is a concern to the defender, they need watching by jump capable craft. It might not stop the initial raid, but at least you will know where they are retreating to.

I've got jump-3 to -4 warships able to refuel unhindered at any system, provided they're willing to spend the extra time out. If they're not, send tankers in with them, refuel the warships immediately when they arrive and have the warships jump on while the tankers spend a week mining fuel in the Kuiper and then return to base. The warships'll arrive at the next system about the same time as the word of their appearance in the previous system arrives. In the Marches, that serves most of the same needs that an empty-hex approach would be needed for.

The only empty spaces of concern are those involving 4-6 parsec gaps (given that the Zho's tend toward jump-3, if they're the aggressor). If I were planning a strike, I'd have serious doubts about an operation of that scale escaping the attention of the enemy's espionage apparatus if my tankers were coming out of anyplace but my own secure space; in the Spinward Marches, at least, the Imperial/Zhodani borders are either close enough that such a plan is not needed or far enough that such a plan does not help. Sword Worlders might use it to extend the range of their jump-2 warships, but I don't know if their strategic goals require such measures.

As an option for small destroyer-sized commerce raiders, it works better. The greater the difference in size between the fueler and the fueled, the more strategic opportunities open up.

Empty hexes may also have loose hydrogen floating about & available for mining. I've always assumed enough for PC scale craft if they really have to.

You understand that this "loose hydrogen" is - at best - about 1/10,000,000,000,000 (1 ten-trillionth) the density of gas at 1 atmosphere? Even if we assume that ships are typically scooping where the Jovian atmospheric pressure is much lower, you're still needing some way to expand the area of your scoops by a factor of hundreds of billions to trillions in order to scoop fuel in a reasonable time. You're talking about fields extending over hundreds or thousands of kilometers - ramscoops. And not all that is ionized, so your scoop fields need to be able to handle neutral hydrogen.

 

[HG_B]

You're talking about fields extending over hundreds or thousands of kilometers - ramscoops.

Plus, moving at a considerable fraction of c

 

[RockyMountainNavy]

PP:F data point

In Power Projection:Fleet, Table 32 is Fuel Availability at Starports. I don't know the provenance of this table (TCS?) but it could also be useful to you as a data point.
Starport/dTons Fuel Available
A 2,000,000 dT
B 1,500,000 dT
C 1,000,000 dT
D 500,000 dT
E or X is No Fuel Available
The rules state that "If the total fuel required by the Task Force exceeds the starport capacity, the player must decide which ships are refueled immediately. The remainder of the fleet must wait a week for the starport's fuel reserves to be replenished so those ships can continue refueling."

 

[Carlobrand]

Plus, moving at a considerable fraction of c

I'm sorry, are you suggesting speed as an alternative to using fields? It'd take a ship at 6g about a week to get up to 12% of C, during which it covers about 11 billion kilometers and - I think - picks up as much gas as if it had flown through a meter of Jovian atmosphere at 1 bar. Still need to find a way to widen the intake "net" if interstellar hydrogen is supposed to be an option.

In Power Projection:Fleet, Table 32 is Fuel Availability at Starports. I don't know the provenance of this table (TCS?) but it could also be useful to you as a data point.
Starport/dTons Fuel Available
A 2,000,000 dT
B 1,500,000 dT
C 1,000,000 dT
D 500,000 dT
E or X is No Fuel Available
The rules state that "If the total fuel required by the Task Force exceeds the starport capacity, the player must decide which ships are refueled immediately. The remainder of the fleet must wait a week for the starport's fuel reserves to be replenished so those ships can continue refueling."

That's from Trillion Credit Squadron. What is "Power Projection:Fleet"?

 

[shield]

Don't forget if you are planning to refuel off comets, ice asteroids, stuff in the outer belts, you have to find it and get there. It could be several days journey to your refuelling source. You must have accurate surveys of each system you are going to do this in. Fine for your own worlds, a problem for operations on independent worlds and probably a secret for hostile worlds.

This should give the IISS survey teams something to do

 

[HG_B]

I'm sorry, are you suggesting speed as an alternative to using fields?

No I'm saying that even with the fields, you'd need the speed to cover enough volume of space in a reasonable period of time, to scoop a meaningful amount of Hy.

 

[Carlobrand]

Don't forget if you are planning to refuel off comets, ice asteroids, stuff in the outer belts, you have to find it and get there. It could be several days journey to your refuelling source. You must have accurate surveys of each system you are going to do this in. Fine for your own worlds, a problem for operations on independent worlds and probably a secret for hostile worlds.

This should give the IISS survey teams something to do

For military applications - and given that I've set an assumption of one week to conduct the fueling from ice sources, for game convenience - it's a minimum of one week out from the primary or else you might get interrupted by local defenders during the process, a bit more if you need to worry about defenders from the local gas giants coming to nose about. I assume that an interstellar government will make the effort to scout out systems and have a plan in place before they get there, as it's essentially impossible to stop the enemy from scouting your Kuiper region.

That sounds vaguely naughty.:devil:

And, yes, I'm certain the IISS spends a lot of time doing exactly that kind of thing.

No I'm saying that even with the fields, you'd need the speed to cover enough volume of space in a reasonable period of time, to scoop a meaningful amount of Hy.

Ah. Thank you for the correction, you're right. The fields either have to be truly huge or you need tremendous speed. Most likely a balance point between the two for efficiency sake. Has anything like a ramscoop ever been mentioned in Traveller?

 

[RockyMountainNavy]

That's from Trillion Credit Squadron. What is "Power Projection:Fleet"?

Power Projection: Fleet is a set of minis rules that are based off the Full Thrust line. See http://traveller.wikia.com/wiki/Power_Projection:_Fleet for more details.

In particular I draw your attention to this line, "There is a campaign system built around a melding of the Fifth Frontier War engine with Trillion Credit Squadron."

I still think Ad Astra sells the item, at least in the US. I also see Amazon has it. Can't recommend this one enough!

 

[Carlobrand]

Power Projection: Fleet is a set of minis rules that are based off the Full Thrust line. See http://traveller.wikia.com/wiki/Power_Projection:_Fleet for more details.

In particular I draw your attention to this line, "There is a campaign system built around a melding of the Fifth Frontier War engine with Trillion Credit Squadron."

I still think Ad Astra sells the item, at least in the US. I also see Amazon has it. Can't recommend this one enough!

Oh, my!

And Christmas right around the corner!

 

[shield]

There are two versions, Escort and fleet. Escort has stuff up to about 5ktn and has some nice zho designs, Fleet is for the big stuff, allows conversion from HG to PPF (and you could work it backward with a bit of work) and a bunch of big zho ships

 

[whartung]

I just don't see casual ice mining being a viable option for the fleet. Most of the fuel scenarios are leveraging existing ships doing what they normally do (skimming, dipping), and then transferring the fuel over to the larger ships.

But ice mining? That needs some specialized gear. It's not parts of the crew walking off the shuttle with picks and wheel barrows.

Let's take the 100K DN scenarios requiring 40K DTon of fuel.

That's (depending on the ruleset), 40,000 Dt * 14m^3/Dt = 560,000 m^3 of fuel.

If you take a meter thick piece of ice, 100 meters wide, it's 5.6Km long. That's a lot of ice. And it's only 0.7% Hydrogen, so you need 80M m^3 of ice. Technically, more, these are numbers for water, and water is more dense than ice, but it's enough to grasp the scope of it.

The HUGE (I mean really huge) power shovels that the coal industry use for strip mining can cut a chunk of roughly 70 m^3. 1.14M Shovels Full of ice. So, if you plan on scraping this up off the ground somewhere, it's going to take some time.

The other way is to locate ice-steroids (80M m^3 is a 235m block), and blow them up in to littler bits, and then hopefully catch them (being a mostly zero gee environment, when things get blasted, they go everywhere -- forever) in something that can then melt them. Then, of course, melt them, which take a bit of energy itself, and finally the cracking process from water to H and O.

I just think that ice mining is going to be very specialized and not something a random destroyer or cruiser is going to be able to do well, much less efficiently. I can see a fleet train showing up and setting up an ice based fueling station, with ground side equipment being a bit different than asteroid based equipment, but it will take some time to get established.