Difference beween Escort Destroyer and Fleet Destroyer?

[whartung]

In Traveller, there is a huge disparity in tonnage between ship categorizations as compared to historical ones.

Yea, it's called "Book 5".

 

[Condottiere]

Using Mongoose rules, you'd want to make fleet destroyers ten kay tonnes plus, with light cruisers starting at around the twenty five kay mark.

 

[Matt123]

There is also likely a distinction between how you would use each class in peace versus war.

In wartime, Escort Destroyers would be used to screen BBs & CRs to take damage and destroy small threats on behalf of the big boys. BB captains do not want their spinal mount degraded in an attack launched by a random rogue merchant. Swatting the merchant is not the problem, leaving station for several months to get repairs is. The alternative of facing En BBs at anything less than full capability can amount to dereliction of duty by the Captain. Better to use DEs which are cheaper and faster to repair and leave the serious ships on station.

In peace, Escort Destroyer squadrons would be spread through a sector engaging in anti-piracy ops, waving the flag and interdiction. They would gather to replace the DFs in war as DFs will immediately be tasked with other missions.

In wartime, Fleet Destroyers could undertake a wide variety of operations. A key one would be screening Fleet CVs (likely reinforced by a CR, in any case the DEs would be too light), but others would include many CR missions such as deep strike where the goal is to avoid taking damage (while inflicting it on infrastructure) and force the opponent to chase n DFs with n+ CRs (which then are not in the front line).

In peace, while FDs are very capable of doing the piracy suppression role, they are expensive assets for this and if damaged when war breaks out, are not available for more pressing missions. My pick (YMMV) would be to use them to screen individual BBs on flag waving missions or to train on forward key worlds. Be an independent presence that can take advantage of the war scenario without waiting for Fleet orders. Underlying orders will be to distract En fleet assets, while taking minimal damage (squadron survival is paramount). This strategy is a variant of "a Fleet in being", where the squadrons mere presence behind the lines demands the enemy compromise his plans.

On design (based on CT Bk5) all destroyers should get one or more missile bays #9, the rest of the weapons should be defensive in nature, a mix of energy, laser and sand. Marines would be useful on DFs (a platoon sounds good), less so on DEs (maybe a section of ships troops). Both should have 50tn ship's boats. The DE for anti-piracy ops (board from the ships boat while the DE stands off) and for fleet use in war. The DF to allow supporting multiple surface operations in war (using the platoon as surface raiders) and for refueling operations at main worlds. I like 10tn lifeboats too, but that's a personal thing, nothing in the game supports or requires lifeboats

On tonnage and jump, for me these fall out of the mission each class engages in. Missile bay = minimum 1000tn. Working with Fleet means keeping up = J4 (J3 for older Fleet BBs). Making life difficult for chasing cruisers = J5 (the wider the jump radius the more En ships have to be tasked, reducing En fighting ships available for offensive action).

Just my 2cr, YMMV.
Cheers
Matt

 

[BlackBat242]

So I see that in your version, upon the declaration of war all independent merchant activity ceases, and the only non-military vessels that still go into space are either ones converted to armed merchant cruisers or those that have been "requisitioned" and move as part of task forces - since you see the need to protect merchant vessels as no longer being in effect during war.

In actual war, any polity that has any degree of reliance on interstellar commerce MUST keep that commerce flowing, or face economic collapse.
Most of such commerce will not move with task forces - but will actually avoid areas where combat is taking place.
Thus, there is an absolute reliance on some form of armed escort for those merchant vessels in order to keep that commerce flowing - due to enemy "armed merchant cruisers", "pirates", and fleet escorts off on independent commerce-raiding missions.

Just as in any war in our history where commerce warfare was active, actual warships WILL be diverted to both commerce-raiding and commerce-protection - this is exactly what escort destroyers are built for!

 

[Matt123]

So I see that in your version, upon the declaration of war all independent merchant activity ceases, and the only non-military vessels that still go into space are either ones converted to armed merchant cruisers or those that have been "requisitioned" and move as part of task forces - since you see the need to protect merchant vessels as no longer being in effect during war.

lol, I leave those roles to Close Escorts (under 1000 tn). Against most light threats they are sufficient, cheaper and hopefully present in greater numbers.

Relying on bigger escorts also implies fewer and larger convoys which drives merchant efficiency down significantly. For example, queing for access to port facilities, waiting for everyone to be ready, potentially waiting for Fleet assigned escorts.

Of course these effects are exactly what I hope to force the En to suffer when throwing squadrons of DFs behind the lines. It would be pleasantly surprised if they weren't playing the same game.

In actual war, any polity that has any degree of reliance on interstellar commerce MUST keep that commerce flowing, or face economic collapse.
Most of such commerce will not move with task forces - but will actually avoid areas where combat is taking place.
Thus, there is an absolute reliance on some form of armed escort for those merchant vessels in order to keep that commerce flowing - due to enemy "armed merchant cruisers", "pirates", and fleet escorts off on independent commerce-raiding missions.

Just as in any war in our history where commerce warfare was active, actual warships WILL be diverted to both commerce-raiding and commerce-protection - this is exactly what escort destroyers are built for!

Totally agree, up to the point that the job requires 1000 tn plus escorts.

Put another way, a couple of 400tn CEs will see off most armed merchants. Those they can't will probably defeat a 1000 tn DE as well (eg: 3000tn DFs, 10000tn plus CRs). If the job needs something more, it will more likely be a task force dedicated to hunting the raider, rather than protecting the merchants.

 

[khadaji2002]

Matt123, you hit it on the head. For merchant escorts the Navy should use smaller, nimbler ships to head off pirates and/or commerce raiders. If something too big for them to handle comes in their job is to get as much information on the threat as possible and get back to base so a larger task force can be sent to deal with the source of the threat. This leaves the larger destroyers available for the tasks mentioned above.

IMTU the PCs are merchanters so they have very little contact with the Navy, per se. So I have not detailed most of the Naval assests in their area. That said, if the PCs decide they want to play Navy types, I will start them in a 400-600 ton anti-piracy craft for this very reason. They'll get to deal with a lot of different captains, chase pirates, and possibly have to decide between saving a merchant ship or getting the data their superiors need back to base.

 

[AnotherDilbert]

There are no submarines in Traveller, and hence no need for ships specialised for hunting subs, which is what WW2 frigates (or DEs) were as far as I know.

Merchant ships need no escort in jump space, you just need to patrol within the 100D limit.

All war-spacecraft face the same combat environment, so will need the same armament and defences. The variables we have to play with are jump range and size (hence cost). All sub-spinal warships will be similar, just as all spinal warships are similar.

So the difference between a frigate and a destroyer would be size and/or jump performance and not much else.



It's difficult (in most systems) to build a combat-worthy ship of less than 1000 Dt. The common patrol corvette has very little combat value and is easily killed by a 1 - 10 kDt merchantman with a few auxiliary turrets...

 

[Condottiere]

I'm not sure how a space convoy works, but let's assume the merchantmen are organized into cube formations, separated by speed and destination/range.

Slightly faster escorts will patrol along the edges, a small spearhead of escorts will lead the cubic convoy, and the faster escorts bringing up the rear.

 

[Matt123]

There are no submarines in Traveller, and hence no need for ships specialised for hunting subs, which is what WW2 frigates (or DEs) were as far as I know.

Merchant ships need no escort in jump space, you just need to patrol within the 100D limit.

True. Of course most reasonably developed systems have a large amount of in-system traffic. Some will jump, some will be sub-light. Most of it will be easy pickings to raiders if local resources are stretched when patrolling beyond the main world. The off-world infrastructure (mining, science faculties, manufacturing, etc) are also highly vulnerable..

All war-spacecraft face the same combat environment, so will need the same armament and defences. The variables we have to play with are jump range and size (hence cost). All sub-spinal warships will be similar, just as all spinal warships are similar.

So the difference between a frigate and a destroyer would be size and/or jump performance and not much else.

Kinda ignores a lot of other factors. A good argument tho for only having BBs in your Fleet.

 

[Condottiere]

Numbers count.

Historically, not only does the battleship cost quite a chunk of change, it's also quite expensive to run and crew.

You can use near obsolescent battleships as escorts for large convoys, which your intelligence reports are within operating range of very large and well armed raiders.

 

[AnotherDilbert]

True. Of course most reasonably developed systems have a large amount of in-system traffic. Some will jump, some will be sub-light.

The real-space traffic might need escorts, but not necessary ships. A 1000 Dt SDB will be very similar to a 1000 Dt frigate, but with less jump fuel and more weapons.

Kinda ignores a lot of other factors. A good argument tho for only having BBs in your Fleet.

Not really, the question of dispersed power versus concentrated power remains unchanged.
A 1 kDt "frigate" may look very similar to a downscaled 10 kDt "destroyer", since space combat work the same for both, but you can still use them for different tasks, depending on how concentrated power you need.

 

[Matt123]

The real-space traffic might need escorts, but not necessary ships. A 1000 Dt SDB will be very similar to a 1000 Dt frigate, but with less jump fuel and more weapons.

And the 1000tn SDB will be a lot more combat effective. Some more design choices to make though.
- Up armour (#15) and streamline for hiding in oceans or GGs +130MCr
- Up armour (#18) and Planetoid hull +20MCr. No hiding, limited capacity to refuel based on small craft or support ships.

Both of these tho would need to be supplied by the Fleet, as TL15 worlds are not typical. So add in a Fleet Tender or two each subsector to distribute the SDBs about and arrange transport back for yearly maintenance.

Of course locally built SDBs will have smaller computers and less armour making them considerably cheaper--- err no. Just calculated that and at Tech 12, the first option above (armour #12) is +630MCr, while using a planetoid hull (armour #7) is +200MCr. (mostly from increased PP costs).

Given a TL 15 1000tn frigate costs ~850MCr these are significant investments for SDBs.that are less combat effective and due to costs, less numerous.

The other consideration is that most systems cannot afford and do not want to pay for large SDBs. Serious defence is what they get for their Imperial tax Cr and most civilian threats can be chased away by 400tn escorts or fighters.

Not really, the question of dispersed power versus concentrated power remains unchanged.
A 1 kDt "frigate" may look very similar to a downscaled 10 kDt "destroyer", since space combat work the same for both, but you can still use them for different tasks, depending on how concentrated power you need.

Dispersed versus concentrated sums up the debate nicely. It also explains why the Imperium uses 400tn Patrol Cruisers extensively, but only if you adopt a different metric to size and jump range and consider cost instead. How do you maintain control over a wide area cheaply so as to allow greater budgets for your concentrated fighting power.

For the same cost as a single 1000tn DE (~850 MCr each), the Imperium can acquire 3 or 4 Patrol Cruisers (~238 MCr each) allowing greater dispersal and providing better intelligence.

From a campaign perspective, it should be fairly apparent that by threatening frontier worlds with lightly armed merchant raiders (pressed into service from the civilian fleet) the response advocated is to commit many times the cost in defence. The pitifully armed merchants don't even need to be effective to achieve this.

 

[Condottiere]

A Free Raider is the equivalent of an armed trawler, which means a fighter bomber should be able to mess it up.

A Subsidized Far Raider might be able to infiltrate and cause some chaos behind the lines, but once identified and localized, fairly easily run down.

Ye traditional surface raider has four and six inch guns and torpedoes, Hilfskreuzers have the potential to take down unwary light cruisers.

 

[mike wightman]

There are no fighter-bomber or torpedo analogues in OTU Traveller ship combat, you can make them for ATU fun...

I've considered making a 'meson torpedo' - a 5t or 10t 'missile' that is mostly armour, electronic countermeasures and engines, its payload consists of a single shot battlefield meson gun. If you can get this thing inside the screens and point defence of a BB it stands the chance of causing serious damage, a lucky shot could mission kill.

A fighter-bomber becomes a delivery system for these meson torps - or rather a forward controller.

 

[kilemall]

A few ways to skin that fighter-bomber cat.

You can allow for point blank strafing with Californium rounds via a VRF Gauss Gun. The idea would be that you get close enough to a warship and it can't bring nuclear damper nodes to bear on so many incoming rounds fast enough or possibly it's own hull getting in the way.

Not much is going to survive 1000 mininukes stitching down the hull.

You can allow more damage for close laser/energy weapons- for instance, increase the High Guard weapon factor the closer the target is, like an Imperium-game suicide attack.

At a certain point it doesn't matter that the fighter faces death, especially if it's weapon value goes to A and effectively gets the spinal level of damage.

The computer limits of fighters can be overcome if one allows datalinking to an accompanying shuttle or small SDB for targetting/EW chores. I would assume such a craft would be a primary target to break up fighter swarms, and would be heavily armored.

Finally, missiles delivered at high relative vee should also get their damage ratings increased, to spinal levels even for conventional missiles. Maneuver or some die-roll equivalent would need to be done to establish that value.

 

[kilemall]

From a campaign perspective, it should be fairly apparent that by threatening frontier worlds with lightly armed merchant raiders (pressed into service from the civilian fleet) the response advocated is to commit many times the cost in defence. The pitifully armed merchants don't even need to be effective to achieve this.

And so we arrive at a reason for allowing merchant ships to be armed, and are even encouraged to do so for that sweet Cr25000 mail contract payoff.

Do the mail delivery 20 times a year and that's Cr500,000, well on your way to paying off that new laser.

 

[blair]

A Subsidized Far Raider might be able to infiltrate and cause some chaos behind the lines, but once identified and localized, fairly easily run down.

Ye traditional surface raider has four and six inch guns and torpedoes, Hilfskreuzers have the potential to take down unwary light cruisers.

This looks like the way to go at TL12 and below - maybe TL13 as well, but TL13 is always a force-design swamp. It could be implemented by either by building a ship too hot to operate economically (like a traditional auxiliary merchant cruiser) or by paying to outfit the hold as a big launch facility and loading it with fighters and whatnot in wartime (like a Merchant Aircraft Carrier).

 

[AnotherDilbert]

And the 1000tn SDB will be a lot more combat effective. Some more design choices to make though.
- Up armour (#15) and streamline for hiding in oceans or GGs +130MCr
- Up armour (#18) and Planetoid hull +20MCr. No hiding, limited capacity to refuel based on small craft or support ships.

At TL15 they would both have reasonable armour and agility, and be armed with the same missile bay (presuming CT).
The SDB might replace the jump drive and fuel with planetoid, making it much cheaper.
None of them would be as cheap as GCr 0.8, if they hope to be combat effective.

Dispersed versus concentrated sums up the debate nicely. It also explains why the Imperium uses 400tn Patrol Cruisers extensively, but only if you adopt a different metric to size and jump range and consider cost instead. How do you maintain control over a wide area cheaply so as to allow greater budgets for your concentrated fighting power.

For the same cost as a single 1000tn DE (~850 MCr each), the Imperium can acquire 3 or 4 Patrol Cruisers (~238 MCr each) allowing greater dispersal and providing better intelligence.

The need for dispersed power is why we need warships that are cheaper than battleships.

The 400 Dt patrol "cruiser" is not a warship, is has negligible combat value. A few patrol "cruisers" is no replacement for an actual warship.

 

[BlackBat242]

There are no submarines in Traveller, and hence no need for ships specialised for hunting subs, which is what WW2 frigates (or DEs) were as far as I know.

Merchant ships need no escort in jump space, you just need to patrol within the 100D limit.

True. Of course most reasonably developed systems have a large amount of in-system traffic. Some will jump, some will be sub-light. Most of it will be easy pickings to raiders if local resources are stretched when patrolling beyond the main world. The off-world infrastructure (mining, science faculties, manufacturing, etc) are also highly vulnerable..

All war-spacecraft face the same combat environment, so will need the same armament and defences. The variables we have to play with are jump range and size (hence cost). All sub-spinal warships will be similar, just as all spinal warships are similar.

So the difference between a frigate and a destroyer would be size and/or jump performance and not much else.

Kinda ignores a lot of other factors. A good argument tho for only having BBs in your Fleet.

So every system always has vessels to defend incoming merchants... no matter where the merchants emerge from jumpspace there will always be a defense vessel nearby? That's gonna cost some credits!

And what about those routes that have refueling stops in systems with gas giants but little or no population or tech level? More commerce protection vessels have to be stationed there.

Or you could devote a far smaller amount of resources to providing a much smaller number of escorts to accompany convoys from start to finish (yes, less efficient than free movement, but much safer)

 

[AnotherDilbert]

Or you could devote a far smaller amount of resources to providing a much smaller number of escorts to accompany convoys from start to finish (yes, less efficient than free movement, but much safer)

We can't calculate what will require more ships without knowing how many worlds and how many convoys are involved. We don't know how many convoys would be necessary, so we can only speculate.

Note that 100D escorts can be used every day, whereas jump escorts will spend most of its time uselessly in jump space.

According to Far Trader a medium system like Regina has a trade of about 10 MDt and 6 million passengers per year. That would require something like 70 MDt ship tonnage visits per year, or in the region of 200 kDt shipping handled per day. Since we have to support traffic in all directions it would be inefficient to handle that with a few huge ships, but perhaps around 10 kDt ships would be reasonable. That would mean handling 20 ships of 10 kDt each day of 140 ships a week.

Sending out 5 convoys a week (once a week in 5 different directions) would require 1 escort group permanently in Regina and 1 escort group on the other end of the convoys (about 1/5 escort group in five locations), for a total of about 2 escort groups.

If we instead attach an escort to each convoy we would require 5 × 9 / 7 ≈ 6.4 escort groups, presuming they jump every 9 days on average.

We could send out convoys less often, but that would mean merchantmen waiting for a convoy for a long time, decreasing carried trade per ship, leading to a lack of shipping and hence decreased trade, which I assume we do not want.


This is a very simple example but it does not support the proposition that escorting convoys in jump space would use less resources.