On Delta Station

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Rules Overview

On Delta Station is a ruleset intended to narratively replicate the naval battles of WWII and later in a science fiction context. As such it operates under several fundamental concepts:

  • Aircraft (or battlecraft as a more general term) are capable of flight ranges significantly exceeding that of any conventional weapon.
  • Long range detection is unreliable, requiring physical scouting with vehicles.
  • Scouting is an integral part of all battles and rules (in a simple form) for it will exist.
  • Weapons fire and scouting becomes more effective as range decreases.
  • Battles do not continue indefinately; air wings will be depleted of munitions (or aircraft!) quickly and warships will eventually find themselves in a fog of particle shells and waste energy.
  • Aircraft and cruise missiles are "alpha damage" units as compared to conventional warships which are "damage over time" units.
  • Battles fought over large distances will have significant downtimes. This allows for both repairs and the opportunity for a retreat.
  • There is space weather.

Battle Flow

  • Step 1: Reduce range band by 1 (first turn: start at value for environment)
  • Step 2: Roll Scouting vs target formation's Fleet Signature. Each faction gets to roll.
  • Step 3: Scout Intercept. A successful scout intercept gives significant bonuses to all further scouting attempts but the target is not discovered.
  • Step 4: If no faction has discovered the enemy, go to Step 1. If an enemy is detected, go to Step 5.
  • Step 5: Launch Strike; strikes may only be launched one per turn.
  • Step 6: Gunnery; Ships may Gunnery once per pulse. Phase count depends on range.

Pulses: Each turn is divided up into one or more pulses. As a rule the closer the battle is the more pulses happen. This represents ships firing more accurately at closer targets, shorter flight time, etc.
Counterpulses: These are pulses that happen when there is no active battling, giving ships (and other pulse units) time to conduct damage control, regenerate shields, etc. Counterpulses happen after each pulse and the number of Counterpulses after each pulse is determined by distance; longer ranged battles have more 'downtime'. If there is no pulse unit action (such a pure carrier strike) the number of Counterpulses equals the band value.


10 - 1 Pulse, 9 Counterpulses
9 - 1 Pulse, 8 Counterpulses
8 - 1 Pulse, 7 Counterpulses
7 - 1 Pulse, 6 Counterpulses
6 - 1 Pulse, 5 Counterpulses
5 - 2 Pulses, 3 Counterpulses
4 - 2 Pulses, 2 Counterpulses
3 - 3 Pulses, 1 Counterpulses
2 - 5 Pulses, 0 Counterpulses
1 - 10 Pulses, 0 Counterpulses

'Haze' is the general term for the various byproducts of battle such as chaff clouds, expended decoys, scattered blavatsky particle density, electronic interference, smoke from damaged ships, excessive waste heat, space weather and crew exhaustion to name just some. Haze can be considered a battle timer; for a number of turns it will have no effect on battles but thereafter it will steadily increase in effect. The primary effects of haze is command and to-hit difficulties will increase; fighting 'in the haze' is a recipe for chaos.


Fleet units are organized into several stations representing various elements operating together. The different stations are listed below; the two most important are CORE and ESCORT, together these two make up almost every conventional fleet. Note that station in this usage does not imply that all ships are in one specific location, merely a signifier of the broad position and task they are performing.

  • Core units are inevitably the most important units in the formation. Archetypically they are capital ships, but merchants or 'leaders' (ie light cruisers leading destroyers) are also equally valid. Core units are also the units that set the speed of a formation; it is for this reason that escorts are generally fast because they must match (or normally exceed) the speed of the core. A fleet travels at the speed of its slowest ship. As a general rule the core is fairly tight and can provide mutual support; as such the stats of the core units are collected together.
  • Escorts are, as the name implies, the escorting units. They tend to be smaller and more numerous and their main role is to screen and protect the core against enemies. This does not mean that escorts are strictly defensive; they also perform vital roles such as heavy scouting and fixing and, if fitted with torpedoes and the like, are exactly the sort of things that hostile escorts exist to keep far away from the core. Most units explicitly designated as escorts actually represent several individual ships operating together for simplicity. While their naturally dispersed nature means they are less effective at massing firepower at any specific target, this dispersal also means that they can intercept hostiles before they reach the core.
  • Distant Patrol are where ships are deployed in a very loose outer shell to provide scouting of the enemy. This is sometimes done by umbraships which have the advantage of being extremely difficult to detect, but commonly this is taken on by the ubiquitous fleet destroyer or by small, fast light or scout cruisers. There are pros and cons of this, trading out the speed (and expendibility!) of battlecraft for the superior sensors and persistance of warships. This station is (by design) too distant from the core to be directly supported by anything other than battlecraft, hence the importance of speed or stealth; it is about the only realistic defense ships on this station have against a full enemy fleet.
  • Heavy Escorts are a special case were powerful units from cruisers (commonly) right up to fast battlecruisers (not so common) are pushed forward/outwards from the core. This is most commonly done with the intent of engaging and defeating hostile escorts, though the classic 'SAM trap' would also apply. The downside is that this can be a high-risk tactic; a 4,000 ton destroyer may not be worth throwing a carrier strike or torpedo spread at but a 40,000 ton battlecruiser is another thing entirely. And of course if your scouting is wrong you run the risk of having heavy hitters be totally out of place and play no part in battle.
  • Wolfpacks is the station for escorts assigned to the offensive role; their mission is essentially to 'sail towards the sounds of the guns' and engage the enemy. Most escorts are capable of performing in the wolfpack role as well and the difference is generally tactical deployment as opposed to material design differences. The actual use of this station can vary quite widely and it is more commonly found among the Sword and Starship milieu or those taking advantage of loopholes in the VNT regarding small ships. Others, such as the Enduscarans, derivisely call it a 'death ride'. Like Distant Scouts, the Wolfpack station exists outside of effective range of core support. Wolfpacks operate much tighter than Escorts, meaning they concentrate damage more effectively. Of course a wolfpack that has to contend with hostile escorts and the enemy core needs every advantage it can get . . .


While two ships are better than one, it is typical that in a fleet action having twice as many ships is not equivalent to having twice the combat capability. Ships can often be masked by others, suffer fraticidal weapon effects, have overkill and underkill, fire control errors, etc. Effectively, as fleet sizes go up, the effectiveness of each ship goes down. The term for this is Saturation.
As a general rule, Core and Escort will saturate seperately.
Note that not all situations suffer saturation equally; a dozen destroyers escorting a single battleship is not going to materially impede its capacity to shell another battleship, but that same flotilla of destroyers will certainly suffer saturation penalties when defending against an air attack.

Core Unit Concepts

Ships are divided into two functional groups:

  • Core ships are single ships, most notably capital ships but also including heavy cruisers and small aircraft carriers.
  • Escort ships exist as multiples; nominally 4 frigates/destroyers or 2 small cruisers; in narrative terms this is flexible and they do not need to be deployed in exact multiples of 4s and 2s respectively. It is assumed that any oddities are explained by them moving in and out of organization groups or temporary additions/removals. Don't sweat it.


All Battlecraft are Squadron units, which means they are made up of a large number of individual units. As a squadron takes damage down its damage track, it suffers penalties as it has less operational units. This is called the dropout thresholds. Note that in most cases these penalties are a combination of decreased to-hit and lower maximum hit count, but even one lone striker can still manage to put a torpedo into the keel of a ship and cripple it. It just becomes increasingly more difficult to do so.
Battlecraft that have suffered dropout are not automatically lost. They have a survival chance after battle representing planes forces to ditch ordnance and return home with damage. Some weapons may make this more or less likely; DEMP guns and heavy SAMs for example.

Battlecraft types:

  • Scout - (DP, 1 SC) - As the old joke goes, knowing is half the battle. The humble scout is designed to collect information and as such they are affordable and can be carried on most warships. As their primary mission is not to fight but to locate and track the enemy they have good base flight range but extremely limited dogfight ability.
    • Swarmer Variation - (DP, 0 SC) - Short-ranged battlecraft, swarmers are normally drones embarked specifically to provide local cover; they are pure combat and have no real scouting ability.
    • Fighterscout Variation - (DP, 1 SC) - Effectively a souped-up standard fighter loaded with added electronics, fuel tanking and operating in an element-sized formation like regular scouts. Their performance means they can effectively fight for information, even if on the whole they are less resilient compared to a full fighter squadron. They also make a competent CAP for ships unable to support full squadrons of regular fighters.
  • Fighter - (DP, 1 SC) - This is the single most common type of battlecraft and the foundation of essentially every aerospace force out there. Armed with a combination of guns and missiles they are built to achieve aerospace superiority and then support the attack. Some are instead built around a single large weapon (bomb or torpedo, generally) in which case they are known as strikers.
    • Heavy Fighter Variation - (DP, 2 SC) - Heavy fighters are physically larger cousins to regular fighters, trading dogfight performance and speed for improved firepower and survivability. Many of them are deliberately built as 'jack of all trades' capable of delivering heavy firepower against enemy fighters and strike ordnance against ships and ground targets in the same mission.
  • Dominance Fighter (unlock) - (DP, 2 SC) - The absolute last word in aerospace combat, dominance fighters are the elite of the deep sky. Coming in elements as opposed to squadrons they are relatively fragile as a tactical force but can down several times their numbers in a brawl.
  • Superheavy Fighter (unlock) - (DP, 4 SC) - Straddling the line between fighters and gunboats, superheavy fighters can deliver inordinant amount of firepower at anything that happens to wander in front of their gunsights. They also carry as many guns in their turrets as most fighters do in toto and are tough enough to withstand significant fire. While quite fast and agile compared to most other craft their size (by brute force if nothing else) they are still no medium fighter. They are also generally too large to be easily flown off most carriers, requiring either modified motherships or fixed bases. Their spacious frames do give them massive endurance though and they make excellent SPA (Space Patrol Aircraft) and raiders that can look after themselves. Able to all but ignore small-caliber flak, if there's one thing a superheavy fighter does not want to run into is it a warship armed with heavy SAMs. Like dominance fighters, superheavy fighters operate in elements instead of squadrons.
  • Bomber - (DP, 3 SC) - A fairly conventional attack craft, bombers are designed to lug lots of ordnance often over long distances and flatten whatever's on the recieving end. While bombers can fit on regular carriers, they do tend to be a bit of a tight fit.
    • Heavy Bomber Variation - (DP, 5 SC) - The big brother of regular bombers, heavy bombers are even tougher, carry significantly more ordnance and have improved flight endurance. Even larger than superheavy fighters they are essentially limited to fixed bases but can roam across vast areas of space.
  • Superbomber (unlock) - (DP, 6 SC) - Aircraft literally the size of a small warship, superbombers are large enough that they can comfortably dock a handful of regular-sized aircraft onboard.
  • Intruder - (DP, 3 SC) - A hybrid battlecraft, Intruders are midsized vehicles designed for the carriage of infantry (often elite battlesuited assault troops) directly into combat, be they on a planet's surface or a ship in space. Featuring good range, respectable battle ability and serviceble agility they are also seen as overpriced jack-of-all-trades; some militaries swear by them while others swear at them. Intruders normally operate in elements instead of squadrons.
  • Utility - (DP, 3 SC) - Closely related to bombers, utility craft often share critical components such as engines but do away with most if not all of the combat avionics and weapon stores in favor of cargo/passenger volume and cost reduction. Being able to quickly move both passengers and cargo from base to base or base to ship they are a useful if unglamorous addition to any force. They also make easy conversions for support aircraft such as umbral-hunters, patrol craft, tankers and AWACS.
    • Heavy Utility Variation - (DP, 5 SC) - The larger cousins of conventional utility craft, heavy utility craft can carry more individual tonnage further. Many of the same comments apply to these larger craft and they also come in various modified versions. The most significant difference in deployment however is their physically larger size means they cannot normally be landed on carriers and like heavy bombers tend to be flown from surface bases.

Weight variations are significant differences in individual craft weight while maintaining a broadly similar statline. In practical terms, this has several effects:

  • Dropout thresholds are modified, generally by spacing them out more but making the effects more significant (individual craft are harder to take down but losses are more significant)
  • Damage tracks may be lengthened and firepower may be increased.
  • Dogfight and other defensive values may be decreased.
  • Other effects may apply, such as gaining defensive turrets. (dogfight defense)

Battlecraft Stats and Modifications

Battlecraft are inevitably the result of design tradeoffs. Do we construct them with protective armor or lighten them for increased agility? Do we equip them with drop tanks or gun pods?

  • Range - One of the important values for battlecraft is their range, which is measured in bands. Range is the maximum band value that battlecraft can perform missions to. Having short range means you simply cannot act at longer ranges. As a general rule larger battlecraft have longer base range, though scouts - as appropriate for their role - also have high base range. Having excess bands (ie, excess fuel) provides a small bonus as well, as it means your planes can dogfight harder for longer or keep angling for optimal engagement vectors before hitting bingo fuel and having to return home.
  • Deck Points and Size Class are not combat stats but are operationally important. Deck Points (DP) are a measure of how much space is taken up on a ship by the formation while Size Class (SC) is how big any given battlecraft is; a dozen F-14s take up far more space than a single C-130, but good luck fitting said C-130 into the hangar of a CVN. Ships may carry up to their DP in battlecraft, so long as none of them exceed the ship's size class. Ground bases are generally built to much more generous proportions and rarely have significant limits to DP or size class. The baseline size class of different ships and what that translates to is listed below. Ships can be modified to have higher size class and loading oversized craft is possible. For every size class in excess, battlecraft DP requirements are doubled.
SC 0 (Any ship): Swarmers, cruise missiles
SC 1 (Escort carriers, many warships): Scouts, fighters
SC 2 (Fleet carriers): Heavy fighters, dominance fighters
SC 3 (Supercarriers): Bombers, intruders, utility
SC 4: Superheavy fighters
SC 5: Heavy bombers, heavy utility
SC 6: Superbombers

  • Escort Carrier - DP 24, SC 1 - Often derogatorily referred to as Combustible Vulnerable Expendable for the common designation code CVE, escort carriers are indisputably the cheapest and fastest way to get aircraft carriers into the deep sky. Commonly derived directly or indirectly from civilian shipping, escort carriers are often only built during times of conflict when their various limitations are irrelevant next to the needs of more hulls. By far the most significant of these is their lack of speed compared to true battle fleet units, though for many purposes such as escorting merchants or supporting amphibious operations this in fact almost or entirely irrelevant. Note that under the On Delta Station ruleset escort carriers are simply civilian variation light carriers but have been given their own entry because of their ubiquity.
  • Light Carrier - DP 24, SC 1 - Broadly comparable in plane-handling capability to escort carriers, light carriers are warships from the keel up. This means they are tougher, pack better sensors and defensive armament and are significantly faster; many are converted in whole or in part from cruisers. While their air wings cannot compare to those of true capital-tonnage carriers they are much more economical and can effectively fill in secondary theatres or stand in for states unable to afford larger ships.
  • Fleet Carrier - DP 72, SC 2 - The backbone of any serious carrier force, fleet carriers are fast and capable ships. While not fitted for any meaningful gun battles they inevitably have quite significant anti-air defenses and respectable protection. Fundamentally they are the quintessential 'carrier' against which all others are compared.
  • Supercarrier - DP 180, SC 3 - Massive ships that are often more status symbol than military units, supercarriers are intrinsically powerful ships. With a single supercarrier having the battlecraft complement of two or three lesser carriers they can often singlehandedly determine the fate of a battle. Unfortunately their size also makes them tactically inflexible and their tonnage means that they do not have the pace-setting speed of fleet carriers.
  • Battlecarrier - DP 36, SC 2 - Hybrids between carriers and battleships, like most other hybrids they can be a contentious design. With much of their internal volume given over not to hangars but to enlarged turbodynamics to power blast-cannons, heavier defenses and enhanced engines they can have comparable deck parks to fleet carriers but their maintenance abilities are sorely limited in comparison. To some they cannot match a battleship in a line of battle engagement nor match a carrier in fighter wing, to others they can perform quite adequately when more conventional single-role platforms would be little more than targets. Some astrofleets have placed these expensive ships on frontier patrols to good effect.
  • Super Battlecarrier - DP 90, SC 3 - Often seen as the sort of white elephants that give the admirals that actually have to use them headaches, super battlecarriers are exactly what the name suggests; substantially larger counterparts to battlecarriers. In such ships the designers have achieved a one-ship task force by discarding any pretense of budgetary discipline or even common sense. Like most such superships they are often constructed more as vanity projects than anything else though it must be said that craft of such power will always have an outsized influence on any battle they find themselves in.


Imperial Aggrandisement - gain 1 prestige and 1 legitimacy every time you construct a Supership. Lose 2 each every time a Supership is sunk. Superships count double for Show The Flag bonuses.

Misc Thoughts

Attacks will be done via difference dice classes, representing gun calibers/power. Provisionally they are as follows:

  • Flak/Small (autocannons, destroyer caliber guns, etc). Default range 1
  • Medium (mid-sized weapons, cruiser guns). Default range 2
  • Large (capital weapons, battleship guns). Default range 3
  • XL (special superweapon type things).

Ships will have different defenses for different weapon classes. For example destroyers might be fairly vulnerable to small-caliber weapons giving them low Flak defense but slow-firing capital cannons would be relatively ineffectual giving them high defense. A heavily-armored battleship would be the inverse.

Using light ships to scout


Cruise missile attacks (limited use! no reloads!)

Heritage Ships

Heritage Ships are old hulls, often ones that predate the VNT entirely. Typically unique or nearly so, Heritage ships also tend to be more capable or powerful than the serially-produced and treaty-limited capital ships built under the VNT. However, as every heritage ship had a career that lasted four or more decades, once their stats are completed a GM will roll on the following table to determine what happened to them and what their current status is.

Capital ships may be rolled individually or by class, at player request.
Large cruisers or equivalents will only be rolled by class.
Smaller cruisers and escorts are never Heritage Ships.
  • 01-03 - Cursed - This ship has an uncanny and unfortunate history of suffering harm and as such it is all but guaranteed to suffer some manner of (repairable) damage even doing mundane activities. All the repairs from shell impacts and running over fishing boats have perversely kept it in fit condition though.
  • 04-06 - Infamous - Prestige penalty. No matter how many times to repaint them, the Black Ships of Nebka Ctar will be remembered for what they did.
  • 07-08 - Haunted - Morale penalty. If you hear someone banging on the inside of the reactor containment vessel, don't open it. Ever.
  • 09-13 - Worn Out - The ship is just old, general penalty. She shoulda been scrapped ten years ago but there's no budget for a replacement.
  • 14-17 - Tired Engines - Speed penalty. Even hyperalloy thrust casings only last so long before their efficiency drops by a measurable amount.
  • 18-19 - Rusty Guns - Firepower penalty, If we fire any faster we'll blow out the primary grid along with half the keel.
  • 20-21 - Flawed Protection - Armor penalty. The flaws in the protection scheme went undiscovered for decades and there's no feasible fix.
  • 22-24 - Spite - Save vs sinking but always takes damage. Damn the torpedoes, I have not yet begun to fight!
  • 25-30 - Bulged - speed penalty, armor increase. Thicc.
  • 31-33 - Experimental Shielding - Firepower penalty, shield improvement. The hyper-aegis never caught on because it redirected too much power from the main gunnery grid.
  • 34-35 - BBAA conversion - Firepower penalty, AA improvement. Fuck planes. Seriously.
  • 36-37 - Cosmoblaster EX - Firepower and tracking penalty, add megacannon. All hands, prepare for shock and flash.
  • 38-40 - Speed is Armor - armor penalty, speed increase. It never helped anyway.
  • 41-42 - HAL 9000 - Morale penalty, general improvements. [color=red]Friend computer will ensure maximum mission completion at all times.[/color]
  • 43-44 - Freebooter - Firepower penalty, cargo added. Replacing one of the turrets with a cargo hold still leaves you with two more!
  • 45-46 - Royal Yacht - Upkeep penalty, prestige increase. He liked watching gunnery drills from the Admiral's bridge.
  • 47-51 - Refloated and Reconstructed - speed penalty, AA and firepower (fire control) improvement. Even in death I serve.
  • 52-53 - Electronics Testbed - Shield penalty, sensor and EW improvement. A big fat battleship with tons of room is a great place to test new electronics.
  • 54-55 - Missile Silos - AA penalty, +1 cruise missile carrying. Reach out and touch someone.
  • 56-60 - Refitted Cosmoturbines - speed increase. Replacing obsolete drive coils with new ones gives an old ship a new lease on life.
  • 61-63 - Fast Battleship Reconstruction - +1 speed and armor to any ship with -1 armor. Reroll if not. An extensive and expensive project, but well worth it.
  • 64-66 - Comprehensive Reconstruction - general improvements. Ageless warrior.
  • 67-69 - MORE GUNS - Firepower improvement. Modern spin-seperated tibanna gas gives us 20% greater unit bang per unit buck.
  • 70-71 - Machine Spirit - Your ship is haunted, but probably in a good way. What is the nature of the military emergency?
  • 72-76 - Recently Refitted - Like new! The 3rd turbine room still smells of used socks though.
  • 77-78 - Unsinkable - Save vs sinking. Belli dura despicio.
  • 79-83 - Battle of Insert Location - Prestige increase. Insert Location was a glorious day for the astrofleet of Insert Nation.
  • 84-86 - Demi-Carrier - Firepower and shield penalty, +2 carrying. All the carriers got blown up so we got creative.
  • 87-89 - Rebuilt as Carrier - Becomes equivalent carrier hull with same perks and flaws. May be treated as 'Demi-Carrier' if rolled as class, may be rerolled on a Frankenstein result. It was either rebuild her as a carrier or scrap her under the VNT. We chose the former.
  • 90 - Famous Astroguardian - Large Prestige increase, hero shields. Single ship only. The skalds shall sings songs of your actions.
  • 91 - Mysterious Origin - Gains 3 perks, randomly rolled by GM. Single ship only. When the Visitor crashed out of an astral fold two hundred and twenty-three years ago, we all knew the world had changed.
  • 92-94 - Frankenstein - Roll twice and add them together. Convert any duplicated flaws to upkeep penalty, reroll any contradictory results. The number of flaws may not exceed the number of bonuses, upgrade any 'bad' result to an equivalent 'tradeoff' result until net zero is achieved. It's an ugly piece of work but it gets the job done.
  • 95-97 - Very Frankenstein - Roll thrice and add them together. Convert any duplicated flaws to upkeep penalty, reroll any contradictory results. The number of flaws may not exceed the number of bonuses, upgrade any 'bad' result to an equivalent 'tradeoff' result until net zero is achieved. We cut the ship down the middle and welded a hundred-meter section taken from its sunken sistership in. Seems to work.
  • 98-00 - Frankenstein's Monster - Roll five (5) times and add them together. Convert any duplicated flaws to upkeep penalty, reroll any contradictory results. The number of flaws may not exceed the number of bonuses, upgrade any 'bad' result to an equivalent 'tradeoff' result until net zero is achieved. Dear Lord, why?