Fleet resupply

[tzlaine]

The whole reason I want a supply system is that I think it adds strategic depth to have a supply system, since it means that planets, starbases, and whatever else act as supply points, have strategic value. However, I see several problems with having supply ships that are actual on-map units that move about and participate in combat.

Scenario A: Having the supply ships (SS) stay with its fleet and automatically provide supply 1) makes no sense at all, and 2) eliminates the possibility for raiding supply convoys that was cited earlier as a major reason to want non-abstract SS.

Scenario B: Having SS run back and forth between its fleet and the nearest supply point means that resupply happens in somewhat large lumps (i.e. one SS worth of resupply is the smallest amount of resupply that can reach a fleet at once). This has some unfortunate implications:
1) To keep a fleet resupplied, you'll probably want to have a steady stream of SS arrive each and every turn, meaning that you have a small number (maybe only one or two) of SS spaced out at one-turn intervals between your fleet and your nearest supply point (SP).
2) Because of 1, you'll need escorts strung out behind you, also spaced at small, even intervals.
3) Because of 1 and 2, you'll have (at least sometimes) lots of small battles to deal with, unless you choose to resolve them automatically, which is pretty much the point of abstracting these fights.

Basically, I don't want to deal with so many details of keeping my fleet supplied, and I don't want to have to deal with moving all these SS and escorts around all the time.

In addition, I feel that the dynamic I've outlined above will lead to a situation in which you must either attack with such an overwhelming force that running out of supplies won't matter, or attack at very short ranges. I feel that this dynamic will limit the strategic quality of the game unnecessarily, by forcing you to focus on fleet supply as much as fleet operations.

EDIT: Labeled scenarios as A and B for earier reference in posts below.

[drek]

If there is a supply system, I'd keep it as simple as Kohan did. Distance to supply center is the only factor to Kohan, and it's binary: an army is in supply or it's not.

Anything beyond that is difficult to represent on the UI.

Rise of Nations, the RTS from SMaC co-designer Reynolds, also has a supply system that works like this. It accomplishes the goal without being overly complicated.

[Geoff the Medio]

tzlaine: Were you pointing out flaws in a single system, or several systems? If the latter, it doesn't seem like you really know what was being proposed...

The player wouldn't be required to have supply ships (SS) visibily / manually / normally moving back and forth on the map to supply fleets. The SS with a fleet would give you supply every turn, (not lumpy) at a rate that falls according to how far you are from the nearest supply point (SP).

(supplies this turn) = (max supply capacity of SS with fleet) / (round trip travel distance to nearest SP)

The supply route (SR) taken by the SS to the nearest SP would be inerceptable, providing the strategic depth you want. That is, if the enemy puts a raider at a system that the SR crosses, they "catch" some of the SS. If there is no viable SR to the SP for the SS from the fleet, then there can be no supply that turn. Optionally, the SS that appear in battle with a fleet when the fleet attacks/is attacked is a fraction of the total SS, dependent on the round trip length of the SR (as with supply rate). This makes sense, or approximates it.

Implication 1 is irrelivant. For 2, escorts could optionally be assigned to protect the SS of a fleet, so would appear in battle if the fleet's SR is cut. Alternatively, you could put escort groups at the planets along the SR. The SR would preferentially follow safe paths. Implication 3 ignores the fact that some people might want to play out the supply raiding / defence battles. If not, then they can still be autoresolved.

You don't need to move SS manually around the map.

I condsider your plan much more strategically limiting, as if you're out of range, there's nothing you can do about it. With rate dependent on distance (my proposal) you can go arbitrarily far from SP, but risk having the SR cut and receive diminishing returns for SS investment (which makes sense)

If the whole business of the SR being cut and the associated battles bothers you or is too complicated for drek, it can be easily ommitted or replaced with a rule saying the SR can't go through a hostile system... (so no privateers raiding the SR, but they can still cut off your supplies by blocking all possible SR)

[Geoff the Medio]

drek: RoN also had supply wagons that went around with your army...

RoN also doesn't deal with ammo and such, but rather has an attrition rate (which I'm not really fond of... Is that what you'd prefer though?)

Having a "show supply route" button in the UI isn't that complicated. It would just highlight the series of starlanes the supply route follows back to the nearest accessible supply point. It might also show with red / blue / yellow for hostile / friendly / neutral the various systems, thus making it clear why you can or can't have the supply route go through a given system.

[drek]

Been a while since I played RoN. Forgot all about the little wagons.

What I'm trying to emphasise is that it was clear on the RoN and Kohan UIs whether your units where in supply or out.

[tzlaine]

tzlaine: Were you pointing out flaws in a single system, or several systems? If the latter, it doesn't seem like you really know what was being proposed...

I thought I understood your proposal. My Scenario A addresses this:

I wondering about something pretty fundamental: does the supply ships exist on the galaxy map?

I was thinking of a quasi-abstracted system where the supply ships exist on the map, except partly if they're actually doing some suppying.

If supply ship is servicing a fleet, the ship would appear in the fleet window, perhaps specially marked so you'd know it's not "there" in the same sense as the combat ships. If the fleet is attacked, a number of supply ships appear in the battle, roughly the fraction that would be deliverying supplies per turn. (The game could keep track of which ship is there, and which is in transit, and when each will arrive if we want... it could just be random or cycle through them each turn).

On the turns when a particular supply ship isn't actually with the fleet, it would be "en route" with supplies, and not appear on the map. There's various rules to work out concerning what to do when a fleet is completely cut off from supplies... in which case the ships could all appear with the fleet, or could stay in limbo until the fleet becomes unblockaded again. Some provision for running blockades could also be included.

There could also be situations where a supply ship is required to normally fly arcoss the map (not in limbo). The only cases I can think of are:
1) if a fleet's combat ships are all destroyed, so the supply ships are without something to supply and need to get back to their empire
2) the ship is on the other side of your empire than the fleet you want to assign it to supply. We'd need to work out some semi-consistent rules for where a supply ship needs to be to start supplying a particular fleet. The closest world is probly not a good idea, as any blockade could cause the closest world to move significantly, and there could be two nearly equidistant worlds to a given fleet, so which world you'd need to go to would be semi-random.

And my Scenario B addresses this:

I don't think there's any chance of convincing people to support an automated supply / freigther network with ships flying around normally on the map, but automated. Fear of micro is phobia-esque.

I spent a lot more time talking about the last bit of your post, because I think it would be disastrous, for the reasons I stated. However, the first part of your post only differs from my proposal in one major way (though there are several minor differences). The major difference is that I want to abstract out the small raiding/escort engagements, and you want them to be normal battles, optionally auto-resolved.

The player wouldn't be required to have supply ships (SS) visibily / manually / normally moving back and forth on the map to supply fleets. The SS with a fleet would give you supply every turn, (not lumpy) at a rate that falls according to how far you are from the nearest supply point (SP).

I agree; this only applies to Scenario B.

(supplies this turn) = (max supply capacity of SS with fleet) / (round trip travel distance to nearest SP)

You're absolutely right; this is a better model than the one I proposed. It's like mine except for one notable boundary case: I hadn't considered the case in which your SS-provided supply exceeds 100% AND you are outside the round-trip range.

The supply route (SR) taken by the SS to the nearest SP would be inerceptable, providing the strategic depth you want. That is, if the enemy puts a raider at a system that the SR crosses, they "catch" some of the SS. If there is no viable SR to the SP for the SS from the fleet, then there can be no supply that turn. Optionally, the SS that appear in battle with a fleet when the fleet attacks/is attacked is a fraction of the total SS, dependent on the round trip length of the SR (as with supply rate). This makes sense, or approximates it.

Implication 1 is irrelivant. For 2, escorts could optionally be assigned to protect the SS of a fleet, so would appear in battle if the fleet's SR is cut. Alternatively, you could put escort groups at the planets along the SR. The SR would preferentially follow safe paths. Implication 3 ignores the fact that some people might want to play out the supply raiding / defence battles. If not, then they can still be autoresolved.

You don't need to move SS manually around the map.

My proposal did not address SR directly, but I had a similar conception of how SR are determined based on enemy and friendly presence.

I agree that it does make sense to have some SS present in combat, as you suggest (assuming non-abstracted SS combat, of course).

But here we have the only major difference between our conceptions of SS: you would have them in tactical combat and I would not. I can understand that, as you say, some people will want to conduct the SS fights themselves and some will not. But I assert that no one will want to do this for very long. After a certain, relatively early, point in the game, you're going to want to skip these kinds of fights. But since you may be able to squeeze out an advantage through superior tactical skill, you are probably going to end up fighting a lot of these manually, long after you find it enjoyable. This is the essential argument I (and many others) have made: that the opportunity to squeeze out a small advantage through micromanagement, and the potential for losing ones edge if one does not do so, forces micromanagement on the player.

I want to point out one last thing. When you mention the option of the user manually selecting SR, you put us squarely into Scenario B. That is, by offering the option of picking safer/better routes, you end up "need[ing] to move SS manually around the map," in many cases. In fact, when faced with any sufficiently aggressive and intelligent opponent, you will have to do so in the vast majority of cases.

I condsider your plan much more strategically limiting, as if you're out of range, there's nothing you can do about it. With rate dependent on distance (my proposal) you can go arbitrarily far from SP, but risk having the SR cut and receive diminishing returns for SS investment (which makes sense)

Conceded above.

If the whole business of the SR being cut and the associated battles bothers you or is too complicated for drek, it can be easily ommitted or replaced with a rule saying the SR can't go through a hostile system... (so no privateers raiding the SR, but they can still cut off your supplies by blocking all possible SR)

I don't disagree with this at all, as I mentioned above.

Basically, I think our general conception for how supply should work is pretty much the same thing. The only difference, as I mentioned above, is in how we want to resolve SS combat.

[Geoff the Medio]

I can see your point about wanting to autoresolve raids on SR, but not doing so due to the possibility of getting a minor benefit from manually controlling the battle.

I do wonder about how much of an annoying needing to manually control these battles would be though, and thus how relevant the point is. How unimportant does any kind of battle need to be before we declare it trivial and thus not worthy of letting the player manually control? This isn't a clear cut case of supply raids = trivial... there could be lots of other attacks on small groups of ships that occur during a game in which the outcome is obvious, but there might be minor benefits to controlling anyway. For example, catching small groups of enemy ships away from their big fleets is probably a good strategic plan, meaning you'd be always trying to have lots of battles with your big fleet decimating a few straggler enemy vessels. Are these worth manually controlling?

(Granted, there might end up being a SR battle every turn, if the raiders never lose any ships and stay on the SR and the SR doesn't move... this would be tedious after a while, especially if the outcome is only a small fractional change in the rate supplies arrive at the fleet.)

We could just eliminate the idea of escorts for SS accompanying SS in their abstracted invisible journies along the SR. Thus the only way to protect your SR would be to actually station a small escort fleet at a node (system) in the SR. These battles would be less frequent, and perhaps seem less trivial. Conversely, if you cut a SR where there is no escort / defence fleet, then the battle is autoresolved and all SS are destroyed, avoiding trivial battles of this nature. (We can't allow SS capture in this case, however)

I can see some similarity between having to manually move SS around the map to ferry supplies and the micro intrinsic to being able to plot SR manually to avoid raiders, though the latter isn't really the same thing...

Regarding the response to a raid on a SR, if we allow raiding, don't allow manual SR plotting, and have SR the automatically reroute itself to avoid the system where the raid occured, then the SR flipping abuse issue might arise. Alternatively, we could use a system where the SR always follows the shortest nonblocked path from a fleet to a SP, and then either

a) disallow SR raiding altogether, and just have "raiders" (any capital ship) in a system block enemy SR from passing through that system

b) allow a raider fleet to sit at a system on the SR and raid the SR with impunity, until you get some escort ships there to take them out.

Each has pros and cons... I'm not keen on totally disallowing SR raiding... so maybe b) is the way to go? You'd have to be careful to guard your SR though... which might be tedious...

[vishnou00]

Bought from whom? Enemy empires? Conjured from thin... space vacuum, for a few billion credits?

Almost. I assume there is some kind of independant private minor power in the game, like pirate. So you hire a pirate ship (this is why you don't choose the design).

Huh? So a nameless players has to join the game to control everyone's privateers during battles?

No, the player who hired the privateer controls it in battle, but he does so anonymously (so the attacked player doesn't know which enemy empire hired the privateer).

You pay a certain amount of whatever, and then supply ships appear from you supply depots and do the supply thing

How is that any more abstracted than building the ships just like combat ships? (seriously... other than appearing at supply depots instead of shipyards... you've just very vaguely described how to build anything in-game)

Because you don't choose what and where it is you built. If it is based on a % of what you need or have, you don't even decide to built it.

Could there be some advantage to having your supply ships appear in battle, so the attacker isn't left wondering why s/he can't just leave them a few parsecs away while dealing with the battle? Mid-battle resupply is probably too complicated / micro intensive, unless abstracted, and then it would be unstrategic... Other ideas?

<sarcastic>
Ah, that is a good idea, having the opportunity of teleporting a few parsecs away every time you don't want a battle! Why fight a battle you know won't win!
</sarcastic>

I assume that when a ship is part of a fleet, it is at the same place. If someone attacks your fleet, it is to destroy ships belonging to the fleet. You can't just stash away the one you don't want destroyed! Also, the SS in the battle are only a fraction, the one who are not at the supply point and traveling between the fleet and the supply point.

How unimportant does any kind of battle need to be before we declare it trivial and thus not worthy of letting the player manually control?

I would say whenever 2 or more sides have real ships, it's a nontrivial battle. Real ships exclude supply and escort ships.

[Daveybaby]

The solution to this is: the option (1) i presented a few posts back (bottom of page 2). ONLY allow supply ship convoys to be attacked at their fleet location. Thus, combats which involve them are invariably nontrivial. Abstract away all of the actual little ships shuttling back and forth along the supply route.

I know its counterintuitive, but its the best mix of strategic control and simplicity IMO.

[tzlaine]

I can see your point about wanting to autoresolve raids on SR, but not doing so due to the possibility of getting a minor benefit from manually controlling the battle.

I do wonder about how much of an annoying needing to manually control these battles would be though, and thus how relevant the point is. How unimportant does any kind of battle need to be before we declare it trivial and thus not worthy of letting the player manually control? This isn't a clear cut case of supply raids = trivial... there could be lots of other attacks on small groups of ships that occur during a game in which the outcome is obvious, but there might be minor benefits to controlling anyway. For example, catching small groups of enemy ships away from their big fleets is probably a good strategic plan, meaning you'd be always trying to have lots of battles with your big fleet decimating a few straggler enemy vessels. Are these worth manually controlling?

I don't know either how big a problem it might be to deal with a bunch of small supply raids. My feeling is that it will be a pain in the (or at least my) ass.

But I think we can draw a sort of natural distinction between catching small groups of enemy combat vessels and catching supply vessels. To me, the difference is in orientation. I'd rather have the tactical fights be centered upon combat vessels, rather than the supply trains that support them.

So while I wouldn't like to auto-resolve small combats between combat vessels, I wouldn't mind doing so for supply raids.

We could just eliminate the idea of escorts for SS accompanying SS in their abstracted invisible journies along the SR. Thus the only way to protect your SR would be to actually station a small escort fleet at a node (system) in the SR. These battles would be less frequent, and perhaps seem less trivial. Conversely, if you cut a SR where there is no escort / defence fleet, then the battle is autoresolved and all SS are destroyed, avoiding trivial battles of this nature. (We can't allow SS capture in this case, however)

I actually thought you meant all along that you would place raiders and escorts (though under your proposal I assume they are not designated explicitly as such) at systems in SR. I assumed this in my proposal as well. The only difference being that under my proposal, the escorts/raiders would be assigned to their specific duties, and would have an area of effect equal to their range (or something similar).

However, if we have tactical combat for SS, I think we should always have it, if only because 50 SS could not be destroyed by a single raider before most of them escaped. I'm making some assumptions about the combat system here, but you get the idea.

Regarding the response to a raid on a SR, if we allow raiding, don't allow manual SR plotting, and have SR the automatically reroute itself to avoid the system where the raid occured, then the SR flipping abuse issue might arise. Alternatively, we could use a system where the SR always follows the shortest nonblocked path from a fleet to a SP, and then either

a) disallow SR raiding altogether, and just have "raiders" (any capital ship) in a system block enemy SR from passing through that system

b) allow a raider fleet to sit at a system on the SR and raid the SR with impunity, until you get some escort ships there to take them out.

Each has pros and cons... I'm not keen on totally disallowing SR raiding... so maybe b) is the way to go? You'd have to be careful to guard your SR though... which might be tedious...

I like the idea of supply in general, and I also like the idea of raiding, so I'd like for us to come up with a way to do both. So I don't want to go with a). In b) do you mean that until you actually destroy or drive away all hostiles, your SR is disrupted 100%? Or can your friendly force mitigate the disruption caused by hostiles?

As you mentioned at the end there, the tedium of guarding your supply train may make it tiresome to do deep attacks, even when you have the force available to successfully protect all your SS. This is the only reason I'm so in favor of the SS/raid/escort abstraction system.

[Geoff the Medio]

So while I wouldn't like to auto-resolve small combats between combat vessels, I wouldn't mind doing so for supply raids.

I can understand your viewpoint. It seems the best solution would be to not have abstracted escorts accompanying the abstracted SS. Thus all combat is either between groups of combat ships (would be-radiers and raider-hunters) or is a raider attack on a defenceless SS group.

I actually thought you meant all along that you would place raiders and escorts at systems in SR.

There was a suggestion by someone else (actually, most of what I'm championing now wasn't originally suggested by me) that, just as SS are attached to a particular fleet and have abstracted journies back to SP, there would be abstracted escorts assigned to protect those SS, and if you attacked the SR, and caught some SS, there would appear some escorts in the battle.

This would eliminate the need to manually move around small fleets to guard your SR, but would also make every SR cutting battle one that involves capital ships on both sides. The abstract escort is worsened however, by the fact that it's probably a lot annoying to have a bunch of battles pop out of nowhere when you weren't really directly responsible for putting the ships where the battle happened... seems to me that this would get much more tedious quicker...

under my proposal, the escorts/raiders ... would have an area of effect equal to their range (or something similar).

The SS and privateer area of effect is the main point I don't like. Determining, and more so player understanding of, the effects and interaction of these ranges would be difficult, I think. Calling it "area" of effect also implies that it ignores the geometry of starlanes, which is certainly a no-no (esp. if offroad travel is disallowed as you claimed in that programming thread (a claim I have yet to see substantiated, and would hope to change, btw )) AoE supply and raiding also just doesn't sit well with me... I just don't like the concept... though that's not really a good argument against them, in of itself.

50 SS could not be destroyed by a single raider before most of them escaped.

Well, if a turn represents a month or a year (has that been decided btw?) then presumably you could catch and attack the SS group repeatedly during the turn... unless they scattered and hid in the asteroid field or somesuch... or were able to get out of the system where you had the encouter by jumping out... (brings up an issue for the retreat thread... do you *have* to stop in every system you come to? We've basically assumed you do in this discussion)

b) allow a raider fleet to sit at a system on the SR and raid the SR with impunity, until you get some escort ships there to take them out.

In b) do you mean that until you actually destroy or drive away all hostiles, your SR is disrupted 100%? Or can your friendly force mitigate the disruption caused by hostiles?

Allow me to elaborate (probly a bad idea in general). When a raider cuts a SR at an undefended system, an abstracted or manual battle takes place between raiders and SS. The SS that appear in the battle are only a fraction of the SS assigned to the fleet. This is the same fraction that would appear with the fleet if you attacked it directly: (total SS) / (round trip SR travel time). Since they're defenceless, these SS are all destroyed, and the fleet loses those SS from it's associated group of SS, and has a proportionately lowered delivery rate of supplies afterwards. Thus you can't totally stop the supplies to the fleet just by raiding. If there's another viable SR through friendly or neutral systems from an SP to the fleet, the SR reroutes to use it, and to avoid the system with the raiders, which is now not neutral / friendly anymore. You can completely blockade the fleet by putting ships (call them "raiders" if you like) at enough systems to block all paths from the fleet to the SP. Thus no SR can be formed, and thus no supplies. Consequence: If you go behind enemy lines, you get no supplies.

As you mentioned at the end there, the tedium of guarding your supply train may make it tiresome to do deep attacks, even when you have the force available to successfully protect all your SS. This is the only reason I'm so in favor of the SS/raid/escort abstraction system.

It would be possible to design your combat fleet such that it has a large supply storage capability, so is able to operate behind enemy lines for some time without need for supplies... this would have to have significant penalties, however, such that it's much more efficient to use supply ships.

Really, needing to deal with keeping your fleets supplied is a good thing... Instead of being mad you can't rampage at full supply, you'd have to suck it up and only attack and manourve such that you're able to maintain your supply lines without overextending yourself...

[haravikk]

Okay, I'll admit to not having read all of this, but I posted a similar topic so I'll bring a few points/ideas over:

Each ship should have X units of supplies that it requires, this could be worked out from crew and ammo, or just a simple fraction of ship cost.
An empire would then have a few stats to reflect the effectiveness of its supply vessels, such as armour and capacity (in units of supplies).
The required number of supply ships is then worked out for the fleet.
What then happens is that a fleet works out the possible routes to the nearest supply point (non-blockaded planet with enough industrial output or supply depots for the number of supply ships) and picks the quickest and safest route.
The total enemy combat rating on this route is then taken and compared to the overall stats of the supply ships being sent, the number of surviving ships can be worked out.
This result works out how many units of supplies make it to the fleet. This is then compared to how much the fleet needs, giving a % of the ammo restocked, repairs made and so on.

I think that graphically this would be easy enough to represent by simply adding a little re-supply ship icon in the fleet info window with two numbers beside it, the first is how many resupply ships the fleet got last turn while the second is how many it needed. Or even a single percentage showing how much of the required supplies were received would work. If this is too low then there are there are enemies on all routes.

Another idea I had in my thread was to have supply space on ships (or even fleet ships dedicated to storing supplies in case of supply cut-off). This way a ship could have more supply units than it needs per turn, allowing it to fight effectively for several turns without re-supply ships. Re-supply ships would attempt to replenish these stores where possible.

[Geoff the Medio]

picks the quickest and safest route.

These can be mutually exclusive requirements... how do you calculate safety and how does it compare to speed in terms of value for route calculation? How do you explain this to the player, clearly?

The total enemy combat rating on this route is then taken and compared to the overall stats of the supply ships being sent, the number of surviving ships can be worked out.

Ok, so all these ships are being shot down... does that drastically increase the cost of supplying the fleet? It's not really enough to just say there's a drop in the supplies that reach the fleet, as I would expect the ships to carry supplies cost a significant fraction of the cost to make the supplies themselves. For example, if the cost of a supply ship is equal to the cost of the supplies it can carry, and 100% of your supply ships are stopped, then you end up paying 200% supply cost every turn to send no supplies. This is kind of a bad deal... and there should be some way for the player to opt out of this situation... (And it's not clear cut either... there's the whole range of possible amounts of supplies getting through...) There should also be a way to send extra supply ships, to ensure sufficient supplies got through... but the % lost system alone doesn't really work for this...

You didn't specify if the ships were automatically built each turn to supply the fleets, or if they had to be prebuilt like other ships. If the former, it's a bit inconsistent that supply ships don't have a minimum build time like other vessels. If the latter, then what happens if you don't have enough supply ships for all your fleets? Do the supply ships have to be located at a certain place to supply certain fleets, or do they exist anywhere they're needed throughout the empire?

Or are you saying there are no supply ships as such, but rather the supplies get sent automatically to all fleets in an abstracted manner? Would abstract supply ship "stats" always be the best you can make? would there be some additional cost penalty to making better armoured supply ships? would the player have a choice in this, and could certain supply routes have different degrees of armour and cost penalties associated with this?

I think that graphically this would be easy enough to represent
...
two numbers ... resupply ships the fleet got last turn ... how many it needed.

This tells the player how many supply ships arrived, but that's not really useful information, in of itself. The player needs to know what the supply route is, and details of why the given amount of supplies got through, and not more, and some better indication of the consequences of having only, say 45% supply, and not 100%

have supply space on ships. ... This way a ship could ... fight effectively for several turns without re-supply

No objections. Most other systems incorporated supply storage on ships as well... especially for things like ammo and fighters, which don't depete unless you actually use them.

[haravikk]

Well the way I saw it, re-supply is really the result of the money you pour into fleet maintenance. They would be abstracted ships, dealing with individual ships would be tedious IMO.
I also don't think that build time for these re-supply ships is even a concern, they would be just like freighters in MOO3, you simply have them, these would be tiny ships that always reflect the best supply-ship stats you have. Keep it simple.

I don't see that being able to opt out of sending ships to a fleet really matters, you pay maintenance per turn and it's dealt with, they'd really just be a stat and if it goes down you know you have a route to clear out to help your attacking fleet(s). Perhaps some options like the configuration of all supply-ships and how much excess (if any) to send. So if cost becomes a problem you can decrease the supplies sent or try a cheaper supply-ship configuration.

As for speed vs safety, it's really a matter of working out what you can get to the fleet. If you pick a really long route with no enemies then your fleet may have no supplies for two turns before it gets 1 turn of supplies, only allowing it to repair 1/3rd of the damage it has sustained. But if the ships take a riskier but quicker route then the fleet may get 50% of the needed supplies each turn which is better. In other words whichever route maximises the supplies to go through is taken.
In relation to turns, it would be wasteful to keep track of individual supply fleets and where they are. It might be better simply to have them immediately despatched and immediately arriving, but if the journey is 3 turns then the supplies delivered is divided by 3 (for example). So a fleet would get 33% per turn rather than 100% after 3 turns.

I really want a re-supply element to the game, but it should be as simple as possible. All the player needs to know is that supplies are sent to their ships, and if they are getting enough. If you are receiving 0% supplies (thereby only being able to make very minimal repairs) for a fleet then you know you need to clear a route or capture a planet from which you can start receiving supplies.

[Geoff the Medio]

I don't think you've really thought this plan through... Are you describing a plan, or brainstorming it as as you go?

... a fleet ... picks the quickest and safest route ...

... you pick a really long route with no enemies ...

Which is it: The fleet automatically picking a route, or you doing it?

In relation to turns, it would be wasteful to keep track of individual supply fleets and where they are.

If you pick a really long route with no enemies then your fleet may have no supplies for two turns before it gets 1 turn of supplies, only allowing it to repair 1/3rd of the damage it has sustained.

Why wouldn't that one turn of supplies be enough to fully repair? They haven't spoiled during the journey... If you always send out 100% of what's needed, then one batch should be enough to do 100% of reapairs (if that's what supplies are for), whenever they arrives (assuming no additional damage occured in the meantime).

If you're not keeping track of individual supply ships (or fleets) then how can you know how long the delay is between sending and receiving a batch of supplies?

(the following mechanism is better, imho)

... if the journey is 3 turns then the supplies delivered is divided by 3 (for example). So a fleet would get 33% per turn rather than 100% after 3 turns.

This is the same sort of distance dependence in the proposal I'm supporting... except that instead of sending 100% and losing most (thus ensuring you're always undersupplied), the system I support would have a supply transfer capacity based on the number of supply ships assingned to the fleet. The maximum supplies available for a fleet each turn is (capacity) / (supply route travel time). This approximates spreading out your supply ships so that the same number arrive each turn. (Note: supply ships would have to be built and assinged to a fleet, and could be intercepted)

I don't see that being able to opt out of sending ships to a fleet really matters

I think it matters if you have to pay a big maintainance cost each turn and get little or no benefit from it. If there's a big gauntlet of enemy raiders, why would you send your lines of supply ships to be slaughtered? It's much simplier and saner to say a particular system can or can't be passed through by supply ships, rather than to say X% are lost by passing through. (If you can't go through a system, you route around it. If you can't find another route, you fleet gets no supplies) This is also much easier for the player to understand and deal with.

I really want a re-supply element to the game, but it should be as simple as possible.

Perhaps some options like the configuration of all supply-ships and how much excess (if any) to send. So if cost becomes a problem you can decrease the supplies sent or try a cheaper supply-ship configuration.

What qualifies as simple is not well defined, but I don't think this is it...