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Fleet Train - How to use it?


SOC-14 1K
I had some time at hand and some thoughts on the fleet train, the resupply and maintenance vessels, came up. The result is bunch of random thoughts up for discussion. As a side note, I normally use and accept a "large ship universe" where Azanti's are a mid-sized craft.

Strategic speed

Traveller fleet doctrin calls for a J4 strategic and M4 tactical fleet movement as a minimum. This means a fleet tender must be capabel of at least J4 to be useful, turning 45+ percent of his hull volume over to fuel and Jumpdrives.

This means a fleet tender must be rather large to be useful unless one wants one tender per warship. At the same time, this means light armament without bays or spinal guns

Fleet tankers

Tankers are of limited use since at most they can fuel up one ship of their own size. So they have two possible uses:

1) Filling up non-streamlined/non skimming craft

The Chrysanthemum class is a classical example of this. Small escorts that are used for fleet protection and will ride High Guard while the major units skim and re-fuel. Their small size makes it possible for one tanker to supply a squadron

2) Preparing fuel in advance

In this scenario the tankers hang back and start producing fuel, storing it in fuel bladders that are tethered to the ship. The "tanker" is reduced to a huge refinery and skimmer carrier, surrounded by fuel packs, possible each assigend to a fuel transfer satelite

2a) Two jumps back

A variant of the above scenario has the fleet train and some escorts remain back in a system two parsek away from the combat zone. The fleet refuels and jumps into battle with enough fuel to jump back. Meanwhile the tankers have two weeks to generate the fuel for the fleet. And the enemy will start hunting for them if he can spare some ships. A nice job for Typ T, Midu Argashan or Kinuir

Hull recycling

Since fleet supply ships must be high-jump and most warships are based on flat wide hulls, recycling older hulls and re-building them as supply ships might be an option. Maybe the ships are already designed with that in mind (i.e not relying on the spinal gun for stability), maybe the conversion is a lot of work

An alternate would be to build a supply craft by re-using most of the plans (say a 60-80 percent part commonality).

Repair ships

These ships will specialise in hull sealing and J-Drive repair to enable damaged ships to get back to the next Depot / friendly drydock. Since major repair work on a capital ship is extremly time consuming and requires enormmous scaffolding returning a badly damaged ship to fighting conditions is not possible in the field

The hunted

Hunting down the attackers fleet train is an extremly important job, yet one that is best left to smaller crafts since fleet size is an important part of it. Checking dozends of systems in a short time with enough strength calls for small-mid sized crafts like the Saberwolf (5000dt) or Midu Argashan (3000dt) destroyers operating in squadron strength.

At the same time it means that system patrolls/defence squads even in un-settled systems close (2 Parsek or less) to major systems might be necessary to prevent attackers from gaining a relatively easy and secure base.

Thoughts/comments/How is it IYTU?
Originally posted by Michael Brinkhues:
Strategic speed

Traveller fleet doctrin calls for a J4 strategic and M4 tactical fleet movement as a minimum. This means a fleet tender must be capabel of at least J4 to be useful, turning 45+ percent of his hull volume over to fuel and Jumpdrives.
You should be aware that not all the DN's in Supplement 9 are really J-4, the Tigress in particular is actually only J-3.

Originally posted by Michael Brinkhues:
Repair ships

Since major repair work on a capital ship is extremly time consuming and requires enormmous scaffolding returning a badly damaged ship to fighting conditions is not possible in the field
See: HG2: Design Option: Framework Structures, for another view on the provisioning of this type of structure in the field.

Originally posted by Michael Brinkhues:
How is it IYTU?
There are two issues here.

1) HG2 Strict Combat.

2) Non-HG2 Strict Combat.

By #1, these issues will never apply. Your fleet train isn't even considered and won't be in the line or even reserve (Maybe Trillion Credit Squadron calls for it, but I never had that.)

By #2, we're at the GM-arbitration stage. The only times that encounters with the fleet train on either side of a battle will happen is if the GM mandates it. In that case, what kind of warfare rules are being used? HG2? I declare my fleet train to be in the reserve and then I try and get them out of there. If some other system is being used, I'd have to know about it.

As for tankers, they aren't used except in rare circumstances IMTU. Usually for first-strike situations to system locations where refueling isn't easy and surprise would be likely. After a quick refueling of the fleet, the tankers would refuel themselves just enough to jump back home.

The real-world problems associated with protecting tankers that went along with the fleet deeper into enemy territory would be extensive. First, they're going to be slow 1 to 2G behemoths. They'll have few to no weapons and at most 1 point of armor (that's 2% of mass at TL-15, and more at lower TLs, so even that is questionable). They won't be surviable. Unless you're running the Starship Operator's manual or something similar, the designs will need bulky 4G engines to reasonably do gas giant wilderness refueling.

In T20, forget it, meson bays would annihilate all tankers post-haste.

In HG2, I think 4-5 kdTon craft (big SDB's) armed with 50-ton missile bays and nuke missiles would have an excellent shot at blowing up any tankers.

MT/TNE/T4/GT? I have no idea.
I don't think that the fleet train needs to be able to match the maximum mobility of the warships being supported. Fleet trains need to be able to keep up with the sustained speed of their fleet, not their maximum mobility.

In TRAVELLER terms that would mean having jump drives able to keep up with the warships but not maneuver drives. 2-Gs is enough for any support vessel except maybe a combat tug (for pulling crippled ships out of the line of battle and into reserve).

I see a need for missile colliers (maybe even missile factory ships, with their own asteroid prospector/miners), hospital/frozen watch ships, and mobile repair docks. Maybe a few others.

Fleet trains would of course have escorts: mostly smaller ships with a few cruisers for heavy firepower. Nothing short of a small task force should be able to threaten a fleet train.
The JTAS article (Best of JTAS #1, JTAS Reprints Vol 1, don't know the issue number) on Asteroid mining gives us a good reference point for volume requirements for LS Recharge.

ISTR that it's 50 person/weeks per ton (displacement) of cargo.

So 1 ton cargo space per 25 crewmen per two weeks.

That help the calcs any?
Going beyond the HG combat system to FFW etc. you do indeed find fleet support ships - the tanker squadrons. Add the evidence provided by FSotSI :eek: and the Imperium (and the Zhodani) definitely consider their supply train.

In FFW the tanker units make some pretty sneaky attacks possible...
A bit on the ideas background

I wasn't thinking in terms of HighGuard combat scenarios here, more in general terms of the universe and possible scenarios for a military campaign.

I actually never designed ships outside of MT, TNE and GT so HighGuard is a black hole to me.

Being a MT / GT player mostly, I have browsed through Shattered Ships of the Fighting Empire and the questions was aroused partially be the supply ships there.

On the ideas

+ I agree with low M-Drive performance of most supply ships.

+ Reducing J-rating is something to think about. Maybe special craft for the few occassions (Diaspora) where the range is needed/useful

+ Fast Resupply crafts. Now that's an idea. How fast can one reload missiles/sand canisters?
General terms. Hmm.

Originally posted by RainOfSteel:
</font><blockquote>quote:</font><hr />Originally posted by vegascat:
Well argued but for one point, info travels at speed of travel. An invading force could cross an entire sector before an effective defense force could get in it's way. Thus the need for implaced defense forces.
IMTU . . .

An enemy fleet of 100 or even 1000 vessels or however many, they all jump in-system, near the gas giant or other wilderness refueling site, of whatever defender they are attacking. An event quite impossible to hide from local military scouts. Now, if Supplement 9: Fighting Ships is any guide, the fleet will contain vessels of J-3 to J-5 (maybe with some J-6 Couriers for communications). Likely mostly J-4 ships of the line (Supp. 9's most common heavy military vessel was J-4 M-6, the J-5 vessels were either colonial or light, with some vessels at J-3, and there were no J-6 ships of the line).

Now, the local military scout/couriers will be J-6, and they'll jump out-system as soon as they have a ballpark idea of the size of the enemy forces, possibly within 1 to 10 minutes of picking up the enemy force, and no longer.

Since the enemey fleet is going to be largely constrained by the J-4 limit of its ships of the line, the J-6 military scout/couriers of the defenders will jump to their pre-arranged behind the lines meeting points. Once there, more J-6 scout/couriers, waiting on station, will receive a communications dump from the freshly jumped-in scout/couriers from the just-invaded star system, and they too will jump out in only minutes, to repeat however many times is necessary to reach the local reserve points and laterally one or two jumps to nearby border areas (etc.), and right on to the local Depot so they are kept informed of events, and right on from there to various other important sites. If the military scout/couriers jump through an X-Boat Route world, they can dump a coded signal into that system, and local communications will also be informed (though much more slowly). This means that news of the invaders will reach defenders in the rear long before the invading fleet.

In the meantime, the enemy fleet must spend several hours refueling. Possibly they will have to perform a sweep of the Gas-Giant or ocean refueling site to assure a lack of traps or hidden defensive vessels, and while anything emplaced there (fixed or mobile defenses) can probably be crushed, it'll take extra time to do the scanning. The enemy fleet can avoid this and recklessly go ahead and wilderness refuel without checking, but the whole fleet must still refuel, and IIRC, High Guard practices mean that the entire fleet may not, not even half of it, refuel at once. So it may take enough time for three or four sets of ships to refuel if only 1/3 to 1/4 of the fleet refuels at once.

Tankers might supply enough fuel to jump once more, but refueling time is still required, and having enough Tankers to handle an entire invasion fleet would be very, very expensive, and they would be left behind after the first refueling, vulnerable (or the invading fleet would have to wait around after refueling while the Tankers wilderness refueled and jumped back to safety). Having enough Tankers to refuel the Tankers and have them come along on a second jump would be quite a feat, so many Tankers . . .

Well, that's just my take on the necessary delays imposed on any invading fleet.
</font>[/QUOTE]Note my reference to the "J-4 limit of the ships of the line", as I posted this before I became aware of the errors in the DNs of Supp-9. The actual constraint will more likely be J-3 due to the big battlewagons (in T20, there will be no big battlewagons, unfortunately).
May I ask why there'll be "no big battlewagons" in T20?

TA 7 has quite a number of 200.000dt and bigger ships in it (Plankwell, Tianamen, Diaspora etc)
Because a meson bay armed ship pops them like balloons...

Two or three meson bays on a light cruiser or heavy destroyer would make capital ships the white elephant of T20 fleets.
Getting back on topic...

Check this out for ideas on auxilaries:


Nice write-up on refitting liberty ships (freighters) to be used as aircraft repair centers: similar refits of freighters (Subsidized Merchant and Liner perhaps) might be considered for Traveller ships to support fighter squadrons and / or SDB's in front-line areas.

Scott Martin