Rules for submarines were not included in e20 Lite 0.5, so I came up with some.
Before I get to that, however, I have realized that the Gunnery
skill needs two additional specializations:
- Bombs: Includes aerial bombs (like the ones I posted rules for above) as well as depth charges (just the basic kind; hedgehogs, squids, and other depth-charge mortars would fall under the mortars & artillery specialization while rocket-propelled depth charges would fall under the rockets & missiles specialization).
- Torpedoes: Self-explanatory.
OK, now on to my proposed submarine rules:
To start with, I'm going to discuss a few background concepts:Visibility and light penetration:
When you stand at the end of a pier and look down into the water, you can see a certain depth down, after which everything gets too dark to see. If you've ever looked down into water from a tower or plane, you may have noticed that you can see things quite a bit deeper than if you were standing just above the water. If you get too high, however, you can't see past the surface of the water at all. This effect, of being able to see deeper, then not at all, as you increase in elevation, happens because of the way water and air reflect and refract light. I'm not real keen on the details, so don't ask.
If you go under the water, the deeper you go, the darker it gets. That's because light is absorbed by water and by particles suspended in the water, and the deeper you go the more water and particles there are between you and the surface to absorb light. When you get deep enough, there isn't enough light to support photosynthesis, so plants can no longer survive. This is known as the aphotic zone.
The effects discussed above vary significantly depending on the type of water (fresh or salt) and how clear or murky it is. In the rules that follow, I've based everything on open ocean. If you're dealing with water murkier than that (such as a muddy lake or estuary), visibility and light penetration will be worse. If you're dealing with clearer water (such as a pristine mountain lake), visibility and light penetration will be better.Thermocline:
As you go deeper into water, it generally gets colder. The thermocline is a layer in the ocean (or in a large lake) where the rate of temperature reduction with depth is significantly higher than in the water above and below. The thermocline can move a lot
. In the tropics it's almost always from about 300 feet to about 600 feet. In temperate areas it can get as deep as 3,500 feet, usually in the summer. In the arctic, it usually doesn't exist (the water at the surface is already about as cold as it can get).
The thermocline is important to these rules because it creates a negative sound speed gradient, which reflects and refracts sound waves, making it nearly impossible to use sonar effectively to find things on the opposite side of the thermocline. Submarines can "hide" from ships by going below the thermocline. Of course, they're not hidden from other
submarines that are also below the thermocline.Modern vs. WWII subs and torpedoes:
Submarines didn't change a whole lot from WWI to WWII. They changed dramatically in the post-war years. In WWII and before, a submarine was really a boat that could go underwater for a while in order to escape more heavily armed ships. They spent most of their time on the surface and were optimized more for the surface than for underwater: they couldn't go as fast underwater as they could on the surface. Modern submarines are the opposite. Modern submarines generally only surface to enter and exit port and are completely optimized for movement underwater: they go faster underwater than they can on the surface.
Torpedoes changed significantly after WWII because of the advent of guided torpedoes: modern torpedoes are all
guided (except for some crazy experimental super-speed underwater rockets like the one that blew up the Kursk
). For a missile, the guidance system represents a significant portion of the missile's weight, and weight is always a critical consideration for something that flies through the air, so it still makes sense in some cases to make unguided rockets. Not so with torpedoes: they are already so large and heavy that the guidance system doesn't represent as big a percentage of the total, and while mass is still important, it's not as critical as it is with aerial missiles, so there's no significant advantage in leaving the guidance system out. In addition to changing torpedo tactics (longer-range shots are feasible with guidance, and big spreads of torpedoes are no longer needed), guidance allowed torpedoes to become an anti-submarine weapon. A WWII torpedo would only work against a submarine if that submarine happened to be surfaced at the time. WWII submarines were pretty much useless for hunting other submarines. A modern guided torpedo can attack a submarine at any depth, and submarines are now the best
weapon for hunting other submarines. One other thing changed significantly about torpedoes: the way they cause damage. A WWII torpedo had a contact fuse in the tip and would literally ram a ship just below the waterline, then explode there. This was generally more effective than guns at sinking ships because it created a big hole below the waterline. Modern torpedoes take it to an entirely different level: they use a proximity fuse to explode underneath
the ship. The explosion creates a huge bubble of gas under the water, pushing up on the center of the keel and stressing it. Then, the bubble collapses, leaving the center of the keel unsupported by water. The target ship literally snaps in half. Needless to say, I will be nerfing the damage for torpedoes considerably in order to keep things within the scope of "heroic adventure."Airplanes, Submarines, and Submersibles:
Like airplanes, submarines can move in three dimensions. Actually, it's not very much "like airplanes" at all. Both aircraft and submarines have forces acting on them to push them up, and other forces acting to push them down. They control their altitude or depth by manipulating the balance between these forces. For aircraft, the main downward force is weight and the main upward force is lift. Submarines and submersibles use ballast to make the overall density of the sub about the same as the density of the surrounding water, rendering the sub "neutrally bouyant." A "neutrally bouyant" object in the water will tend to stay at its current depth, neither rising (as a less-dense object would) nor sinking (as a more-dense object would). Subs aren't generally perfectly neutrally bouyant, but they are close enough that the rate of sinking/rising is small enough to be controlled by other means. Where an aircraft needs to manipulate its lift to be in equilibrium with its weight for level flight (or out of equilibrium to climb or descend), a sub is generally always in equilibrium and must introduce other forces to change its depth.
A modern military submarine uses planes (the bits that look like stubby little wings on the sides of the conning tower or the sides of the bow) to change the attitude of the submarine, pointing it up or down. This changes the thrust vector from the screws so that a component of the thrust is either pushing the sub up or pushing it down, with the majority of the thrust continuing to push the sub forward. Because the planes only work if there is water flowing past them, and because the change in depth is achieved through thrust from the screws, and because there are practical limits to how far up or down a submarine can tilt its bow, a submarine must be moving forward in order to change depth and the ratio of depth change to forward movement is limited. Also, most modern submarines, when submerged, have slightly negative neutral bouyancy, which is offset by small amounts of lift generated when the submarine is in forward motion. For this reason, a submarine that stops moving will start to sink slowly. Very little forward motion is needed to prevent this. Because they control their direction using rudders, which only work when water is flowing past them, submarines also can't control their direction unless they are moving forward.
Most research submersibles (such as Alvin
), behave very differently from submarines. They have many different propellers and/or impellers pointed in various directions to provide significantly more agility. They can turn in place, move straight up and down, side-to-side, etc.
All types of submarines and submersibles generally have the ability to purge their ballast in an emergency, which causes them to rise rapidly to the surface. This is a brute-force technique and can't be used half-way: you can't purge your ballast to rise straight up for a round or two, then pump new ballast back in to halt the ascent. Once the ballast is purged, the sub is going all of the way to the surface.
I tried to make depth rules that were similar to the altitude rules, but my main priority was to make them feel right.Nuclear Weapons and Power:
You can't talk about modern submarines without talking about nuclear power and nuclear weapons. Before I say anything else about this, I want to start by clearing up a common misunderstanding: the term "nuclear submarine" refers to a submarine that is powered by one or more nuclear reactors. A nuclear submarine might or might not carry nuclear weapons. In fact, the first submarines to carry nuclear weapons predated nuclear submarines: there were diesel-electric submarines that carried nuclear-armed cruise missiles. As far as I know, all modern nuclear-armed submarines are also nuclear powered. A modern nuclear-armed submarine is called a "ballistic missile submarine" or SSBN.
There are huge advantages to nuclear power: a nuclear submarine can stay submerged indefinitely (this is probably the single biggest advantage, because submarines rely on stealth for survival), can move significantly faster than a diesel-electric submarine, and is quieter than a submarine running on diesel. However, even today diesel-electric submarines are still being built. There are a few reasons for this: first and foremost, not every nation has access to compact reactor technology; second, diesel-electric subs are much cheaper to build and maintain than nuclear submarines; third, when operating on batteries with the diesel engines off, they are somewhat quieter than nuclear submarines. There are some rather impressive recent advances in "air independent propulsion" which allow modern diesel-electric submarines to operate for longer periods of time without their snorkels, but ultimately they still need to snorkel most of the time.
I dabbled with the idea of making up rules for nuclear weapons, but concluded that nuclear weapons should always be handled cinematically. If you're anywhere near a nuclear blast, you're toast ("Roll a reflex save for half damage, DC 1,000. Oh, wait. Even half damage would vaporize you five times over. Go ahead and put down the d20 and pick up some d6s: it's time to roll new characters!"). If nuclear weapons are employed in a game, the characters are either far enough away to be completely safe, or on the periphery where effects are minimal. In either case, a cinematic description by the GM is the most appropriate was to model a nuclear explosion. In the latter case, the GM might want to throw in some minor effects (checks to avoid being blown down, damage from flying debris, etc.), possibly even a skill challenge to get to safety before the fallout starts settling. If you're thinking about using a nuclear explosion in your game, check out Ground Zero
, a tool that projects nuclear blast areas on Google Maps.
All that being said, I did need to come up with some stats for nuclear missiles to include on the ballistic missile submarine (not stats for the warhead, just for the missile). A modern nuclear warhead is remarkably small and light, so I reasoned that any nuclear missile (ballistic or otherwise) would be both high-speed and extended-range: the limited remaining space and weight would be more than enough for a nuclear warhead. I checked wikipedia and found that a Trident II (the missiles currently carried on U.S. subs) weighs about 130,000 lbs and has a range of about 7,000 miles; a Minuteman III (the land-based missiles currently in U.S. silos) weighs about 80,000 lbs and has a range of about 8,000 miles. Under my proposed missile rules, a 6XC high-speed extended-range missile would weigh 100,000 lbs and have a range of ten million squares (just over 8,000 miles). I thought I would have to do some fudging, but the rules I set up scale pretty much perfectly! So, there you have it: an intercontinental ballistic missile would be, in game terms, a 6XC high-speed extended-range missile.Limits on Time Submerged:
Vehicles and equipment designed to carry oxygen-breathers underwater are limited in how long they can stay underwater. Different types of vehicles are generally limited by different constraints:
- Dive gear is generally limited by the size of the oxygen supply. I don't know much about scuba gear, rebreathers, mixed-gas rigs, etc. Hopefully someone who does can provide some stats for such gear, including how long they last.
- Research submersibles are typically powered entirely by electricity, and carry a finite supply of stored oxygen for breathing. The battery and oxygen stores are generally designed so that both would run out at about the same time (in other words, neither is a definitive limiting factor). Typically they're good for a few hours.
- Modern diesel-electric submarines are capable of producing their own oxygen for breathing, so their time submerged is limited by power supply, not oxygen supply. With their snorkels up, they are limited by the amount of fuel they carry (a length of time most likely measured in weeks). With their snorkels down, they are limited by the amount of electrical power they can store in their batteries (a length of time measured in hours, maybe a few days; submarines with air independent propulsion can stay submerged for two or three weeks).
- Like diesel-electric submarines, nuclear submarines are capable of producing their own oxygen. They never need to surface or use a snorkel for purposes of producing power. They are limited in their time submerged by the amount of food they can carry for their crew (a length of time measured in months).
Enough backround...on to the (proposed) rules!Movement and Depth:
When an underwater character changes depth by one square, it counts as one square of movement, so that an underwater character's total speed for a round is the number of squares moved forward plus the number of squares moved up and down.
An underwater character with limited movement can move one square up or down for every two squares moved forward. An underwater character with limited movement that does not move forward at least its space in squares each round cannot turn, cannot move up, and sinks at a rate of one square per round.
Like flying characters, an underwater character with limited movement can have the hover
trait. An underwater character with the hover
trait can turn in place, can move backwards, can sideslip, and can move up or down irrespective of the number of squares moved forward. An underwater character with the hover
trait does not automatically start sinking when it moves less than its space in squares.Speed:
The listed base speed for a vehicle designed for underwater movement (e.g. submarine or submersible) is its base speed when submerged. When such a vehicle is on the surface, its base speed is halved (rounded down, minimum 1). This that means its maximum speed is also halved, as are all of its speed categories. For WWII or earlier military submarines, this relationship would be reversed (listed base speed is surface speed, submerged speeds are halved). A submarine with its persiscope or snorkel up uses whichever speed is worse (in other words, a modern sub with its periscope or snorkel up has speeds as if it were surfaced, while a WWII or older sub with its periscope or snorkel up has speeds as if it were submerged).Depth Levels:
- Near-Surface: Down to 10 squares (50 ft). Objects at this depth level are visible to observers above the water. Most humans cannot go below this level without an air supply (in fact, most humans can't even get near the bottom of this level without an air supply). Submarines must be at this level to use their periscopes or snorkels.
- Very Shallow: Down to 20 squares (100 ft). Objects at this depth level are visible to observers at low or moderate altitude. Scuba divers do not generally go below this level.
- Shallow: Down to 50 squares (250 ft). Objects at this depth level are visible to observers at moderate altitude. Scuba divers need extra oxygen to go to this level and the risk of decompression sickness is significantly increased.
- Moderate: Down to 100 squares (500 ft). Objects at this depth and below are not visible from above the water. Light from the surface is noticeably reduced at this level. Divers with ordinary scuba gear cannot descend to this level; instead, special mixed-gas supplies are needed.
- Deep: Down to 200 squares (1,000 ft). Light from the surface is significantly reduced at this level. Only saturation divers can dive this deep.
- Very Deep: Down to 500 squares (2,500 ft). Very little light from the surface reaches this level, but photosynthesis is still possible. Divers cannot go this deep: humans need a pressure hull to survive at this level or below. This is the deepest level that military submarines can reach.
- Extreme: Everything below 500 squares (2,500 ft). Less than 1% of light from the surface reaches this deep, and photosynthesis is impossible. Only specially designed research submersibles such as the Alvin or the bathyscape Trieste, or robotic submersibles (usually used for resource extraction) can go this deep.
- Thermocline: This isn't a depth level, it's a layer which separates two particular depth levels. At the beginning of any underwater encounter, the GM should announce the location of the thermocline for that encounter. The DC is increased by +10 for all Sense (acoustic) checks against objects or characters on the opposite side of the thermocline. In the tropics, the thermocline should always be between the shallow and moderate depth levels. In the arctic, there should never be a thermocline. In temperate ocean waters, the thermocline should vary with season: between shallow and moderate in the winter, between moderate and deep in spring and fall, and between deep and very deep in the summer. Very large and deep lakes (such as the great lakes) should have thermoclines, but smaller lakes should not. The location of the thermocline is ultimately at the GM's discretion, but should never change over the course of a single encounter.
An underwater character which sinks delow its maximum depth takes crushing damage at the beginning of its turn every round. The amount of damage depends on the size of the character and the number of depth levels below its maximum. The damage one depth level below maximum is 2d12, plus additional damage as if the weapon were of the same size category as the character. For every additional depth level below its maximum depth, the number of dice increase by one step on the standard progression. For example, a colossal submarine one depth level below its maximum would take 2d12 + 30 damage each round, while a huge submersible two depth levels below its maximum would take 5d12 + 4 damage each round.Loss of Control:
An uncontrolled underwater vehicle behaves like a regular uncontrolled vehcile, with one additional effect: depth change. If the vehicle positively bouyant (e.g. a submarine which has purged its ballast) it rises towards the surface at a rate of one depth level per round. Otherwise, it sinks at a rate of one square per round (even if it has the hover
A non-water breathing creature (e.g. a human) who ascends from depth too rapidly risks decompression sickness. This does not apply to characters inside pressure hulls (e.g. submarines). Each time such a character changes to a higher depth level, he must wait at the bottom of the new depth level for a period of time (see table, below for times) or make a Fort Save (DC = 15 + skipped time in minutes). On a successful save, no decompression sickness effects occur; on a failure, the character suffers constitution damage (see table, below for damage) which can only be cured by treatment in a hyperbaric chamber for 5 hours. Whether the save is successful or not, any time skipped is added to the required wait time at the next depth level (cumulative). On a successful save, the damage for a failed save at the next depth level is increased by one dice category (cumulative).
- From Deep to Moderate: Wait time: 20 minutes; Damage: 1d10
- From Moderate to Shallow: Wait time: 10 minutes; Damage: 1d8
- From Shallow to Very Shallow: Wait time: 5 minutes; Damage: 1d6
- From Very Shallow to Near-Surface: Wait time: 2 minutes; Damage: 1d4
- A scuba diver at shallow depth forgets to make a decompression stops when ascending to the surface. When ascending from shallow to very shallow depth, the skipped time is 5 minutes, making the Fort Save DC 20. He fails the save and takes 1d6 Con damage. When ascending from very shallow to near-surface depth, the skipped time is 7 minutes (5 carried over, plus 2 more), making the Fort Save DC 22. He fails the save again and takes an additional 1d4 Con damage.
- A diver on mixed gasses is running low on breathing gas and doesn't have enough left to wait for the full amount of time at each decompression stop. When ascending from moderate to shallow depth, he only stops for 7 minutes, so he skipped 3 minutes, making the Fort Save DC 18. He succeeds at the save, but the 3 minutes carry over to his next decompression stop and the damage if he fails at the next stop is raised from 1d6 to 1d8. When ascending from shallow to very shallow depth he only stops for 4 minutes, so he skipped 4 minutes (1 from this stop, 3 carried over), making the Fort Save DC 19. He succeeds again, but the 4 minutes carry over and the damage at the next stop is raised from 1d4 to 1d8 (he has now made two saves, to it increases by two damage dice). When he ascends from very shallow to near-surface depth, he only waits 2 minutes, so he skipped 4 minutes (all of it carried over), making the Fort Save DC 19. This time he fails, and so takes 1d8 Con damage.
EDIT: Just remembered that there are no full-round actions in e20. Changed Emergency Surface to comply.Power and Oxygen:
- Steep Dive or Ascent (Dex, limited only): An underwater character with limited movement can climb or descend more steeply than normally allowed. At the beginning of a move action, make a control (Dex) check against DC 20. On a success, you can move one square of depth for every one square of forward movement (instead of every two squares of forward movement) for the remainder of this move action. On a failure by 5 or more, your vehicle becomes uncontrolled.
- Emergency Surface: As a standard action, an underwater character with ballast can surface rapidly by ejecting the ballast (e.g. a submarine purging its ballast tanks or a diver dropping his weighted belt). The character rises one depth level per round and cannot take any other actions until one round after it reaches the surface. The character continues moving forward in the last direction it was moving, but its speed is reduced by one speed category each round. A character subject to decompression sickness must roll all Fort Saves as normal.
A nuclear submarine can stay submerged indefinitely. A diesel-electric submarine can stay submerged indefinitely as long as its snorkel is up and working. A diesel-electric submarine with its snorkel down can stay submerged for one day before it must surface or use its snorkel. A battery-powered research submersible can operate for a finite number of hours defined in its statistics.Weapons:Torpedoes:
My proposed rules for torpedoes are similar to my proposed rules for rockets and missiles, but with much less variation. All modern torpedoes are guided (all WWII and earlier torpedoes are unguided). All modern torpedoes move at a speed of 100 squares/round. All torpedoes do 4d12 splash damage (plus size modifiers). A torpedo that is the same size category as the target or larger is treated as if it has the devastating
trait. All modern torpedoes have the penetrating
trait (WWII and earlier torpedoes do not). The smallest torpedo size is Gargantuan. A Gargantuan torpedo has a base range of 500 squares and the range increases by three steps on the expanded progression for each size category larger than Gargantuan. A Gargantuan torpedo has area 10, and the area increases by one step on the expanded progression for every size category larger than Gargantuan. A Gargantuan torpedo weighs 750 lbs and the weight increases by four steps on the expanded progression for each size category larger than Gargantuan. The purchase DC for a Gargantuan torpedo is 35 and the purchase DC increases by 3 for every size category larger than Gargantuan. Just like missiles and rockets, ranges and speeds should be decreased for historical settings and increased for sci-fi settings, with torpedoes smaller than Gargantuan being possible in sci-fi settings. A torpedo tube is designed to fire torpedoes of a particular size, and cannot fire torpedoes of larger or
smaller size categories.
Aircraft can carry torpedoes on hardpoints using the same rules as missiles or bombs, except that they can't carry torpedoes of a larger size category on hardpoints (a specially designed aircraft could carry larger torpedoes inside a bomb bay, however). Torpedoes have a drag multiplier of x2 to weight. Torpedoes must be dropped from low altitude or below, at low speed or below; if dropped from higher altitude or speed than this, they are destroyed upon impact with the water. An aircraft cannot obtain a target lock on a submerged target, so slightly different rules apply for guided torpedoes dropped from aircraft. First, the torpedo must be programmed to a particular depth level (or to the surface) before it is dropped. Once it enters the water, it begins circling and descending: each round, it moves forward at its speed, turns 45 degrees counter-clockwise, and descends one depth level. Before each of these movments (forward, turn, descend) and after the last, it makes a Sense (acoustic) check against any vehicles within its remaining range, out to 45 degrees either side of its nose, at its current depth level and the depth levels immediately above and below. The first time it successfully detects a vehicle, it establishes a target lock on that vehicle and begins pursuing it using the rules for guided weapons I proposed above (if it was programmed to the surface it will ignore targets below the surface, and vice-versa).
Archaic (unguided) torpedoes:
My proposed rules are primarily focused on modern (guided) torpedoes, but employment of archaic (unguided) torpedoes was so different that I wanted to provide rules for using them. Since they were unguided, and because they took significant time to travel to their targets, it was possible to evade archaic torpedoes by maneuvering to not be where they were aimed. Torpedo boats, destroyers, and submarines compensated for this by firing several torpedoes at a time, aimed to fan out in a wedge as they traveled: a spread
of torpedoes. A ship or submarine with multiple torpedo tubes can make a spread
attack by firing more than one torpedo at a time, with the only limit on the number of torpedoes being the nmber of loaded tubes capable of aiming at the target (e.g. a submarine with eight bow tubes and four stern tubes could fire all eight bow tubes at once). The attacker must choose a target square when firing. The center torpedo in the spread will always move directly towards this target square each round (if an even number of torpedoes are fired, the attacker designates one of the two center torpedoes as the
center torpedo). The other torpedoes start in the same square as the center torpedo, moving in the same direction. After every 10 squares of forward movement, the other torpedoes each slide outward to create the spread effect: the torpedoes on either side slide one square away from the center torpedo, perpendicular to the direction of travel; the next pair of torpedoes out each slide two squares away from the center torpedo, etc. If a torpedo enters the same square as a ship, an attack roll is made for that torpedo.
Archaic torpedoes dropped from aircraft could not be fired in spreads, since each aircraft typically carried only one. Instead, they would travel in a straight line along the same direction the aircraft was flying when it dropped them.Torpedo Missiles:
This is a missile which carries a guided torpedo instead of a standard warhead. A particular square is targeted, and when the missile reaches that square it releases the torpedo into the water. Firing this type of weapon requires both Gunnery (Missiles & Rockets)
and Gunnery (Torpedoes)
. Instead of a target lock, a Gunnery (Missiles & Rockets, Int) check is made to program the missile to go to the desired square, which is a swift action. When the missile gets to the target square, the torpedo is released into the water and follows the rules for a guided torpedo dropped by an aircraft. A torpedo missile carries a torpedo one size category smaller (e.g. a Colossal torpedo missile carries a Gargantuan torpedo). All torpedo missiles are considered reduced range and standard speed. A torpedo missile has a purchase DC equal to the purchase DC of the torpedo +2.Submarine Missiles:
Submarines can carry and fire missiles in a number of ways:
Depth Charges (basic):
- Vertical Launch Tubes: A submarine can have vertical launch tubes designed for missiles of a particular size. These tubes cannot hold missiles of larger or smaller sizes, only the exact size they are designed for. These tubes can be fired at the Deep depth level or less, and can be fired with the submarine surfaced. They can only be reloaded at the pier, or when moored alongside a submarine tender in calm waters.
- Mast-mounted Launchers: Medium-size missiles can be mounted in a launcher mounted on a mast (alongside the periscope and radar). These launchers can only be fired with the periscope up (Near-Surface depth level) or with the submarine surfaced. These launchers can only be reloaded at the pier, or when moored alongside a submarine tender in calm waters.
- Torpedo Tube Capsules: Missiles can be enclosed in special capsules which allow them to be fired from torpedo tubes intended for torpedoes of the same size category. For example, a Gargantuan missile could be loaded into a torpedo tube capsule and then fired from a tube designed for Gargantuan torpedoes. These missiles can be fired at the Moderate depth level or less, but not with the submarine surfaced. The missiles can only be encapsulated at land-based facilities, but pre-encapsulated missiles can be loaded into torpedo tubes by the crew within the submarine. Encapsulating a missile increases the purchase DC by one.
These are archaic weapons, no longer in use because they have been completely supplanted by guided torpedoes. This category encompasses barrel-style depth charges rolled off of stern racks on ships, as well as depth bombs dropped by aircraft. Ships stopped carrying depth charges of this type shortly after WWII, but aircraft continued utilizing them at least into the late 1960s.
A basic depth charge weighs the same as a bomb of the same size and does 4d12 blast damage with the same area as a torpedo of the same size. Before an attack is made with a depth charge, the attacker must announce the depth level where it will explode. If the target is not actually at that depth level, the attack automatically misses (although GMs should still have the attack make an attack roll, to avoid revealing the actual depth level of the target). Range penalties are based on the depth of the target:
- Near-Surface: Point-blank range
- Very Shallow: Short range
- Shallow: Medium range
- Moderate: Long range
- Deep: Extreme range
- Very Deep: Beyond maximum range (depth charges can't attack here)
- Extreme: Beyond maximum range (depth charges can't attack here)
Depth charges can be used to make salvo
attacks, but the effects are different: when depth charges are used to make a salvo
attack, each depth charge is set to explode at a different depth (near surface, very shallow, shallow, moderate, and deep), so that one of them will detonate at the correct depth (unless the target is Very Deep or deeper, where depth charges can't reach). No extra damage is done and the area is not increased because the other depth charges all explode at the wrong depth.Depth Charges (mortar):
These are weapons such as hedgehogs or squids, which appeared around the end of WWII. Just like basic depth charges (which these largely supplanted at time), they have since been completely supplanted by modern homing torpedoes. A large number of smaller depth charges are launched simultaneously, aimed to spread out over a wide area and set to detonate at various depths. They do 4d8 blast damage with area 20 at every depth level from near-surface to deep, and have base range of 100 squares.Depth Charges (rocket):
These come in two varieties:
- Long-range rockets that carry nuclear depth bombs. They don't need to be super accurate, for obvious reasons. I'm not going to provide rules for these, for reasons I've already explained.
- Weapons that work just like the mortar depth charges I described above, except that they use small rockets to launch the explosives instead of mortars. These work the same as mortar depth charges excpet that they use a different specialization of the gunnery skill (Rockets & Missiles instead of Mortars & Artillery), the base range is 200 squares instead of 100, and they do 4d6 damage instead of 4d8.
Mines come in many varieties: free-floating mines on the surface or at a particular depth; moored mines at the surface or at a particular depth (like the mines on chains you see in movies); mines that rest on the bottom and explode or release homing torpedoes when a proximity sensor is triggered; etc. They also come in many sizes, and the fuses can be contact (the spikes on the balls you see in movies), magnetic, acoustic, etc. Given the wide variety of mines and the way they are employed, I think it is best to treat them as traps rather than as weapons.New Vehicles:Note:
Some of these statistics I feel really confident about, others not so much. Here's a general breakdown of how much stock you should put in my numbers:
Attack Submarine, Nuclear Powered:
- Crew: An amalgam of real-world examples, fudged to fit the standard or expanded progression.
- Pass: An amalgam of real-world examples, fudged to fit the standard or expanded progression. For submarines, passengers are typically special operations forces.
- Cargo: For submarines, this primarily represents foodstuffs and other supplies needed for the crew and passengers. Based on 5 lbs/person/day for the entire complement (crew and passengers) for 60 days (diesel-electric attack), 90 days (nuclear attack), or 120 days (guided-missile), or 180 days (ballistic missile), plus 50% extra for slop, then rounded to a number of tons on the expanded progression. For the destroyer, I used the same method for 60 days, but with 2x slop instead of 1.5x. For the diver sub, I pulled it out of my rear. For the helo, I made a (very well educated) guess, based on the assumption that the only "cargo" would be things that the crew and passengers would bring along for a flight (survival gear, boxed lunches, passengers' personal affects, etc.)
- CTRL Mod: I made up numbers that looked good in comparison to other units.
- Speed (base/max): An amalgam of real-world examples, fudged to make nice round numbers.
- Defenses (Prm/Frt/Ref): I made up numbers that looked good in comparison to other units.
- Hard/DR: I made up numbers that looked good in comparison to other units.
- HP: I made up numbers that looked good in comparison to other units.
- Size: Spot-on for most of the units. Nuclear attack submarines are right on the line between C and 1XC, so I decided to make them C to emphasize the size difference between missile subs and attack subs. Making them 1XC would have instead emphasized the size difference between nuclear attack subs and diesel-electric attack subs, which I didn't think was as important.
- Abilities (Str/Dex/Int): I made up numbers that looked good in comparison to other units.
- Weapons or Special Equipment: An amalgam of real-world examples, fudged to make nice round numbers.
- Adj Level: I made up numbers that looked good in comparison to other units.
- Purch DC: Where I could find numbers online, I used those (cuz everyting on teh internets is true!). Otherwise, I made up numbers that seemed reasonable.
Attack Submarine, Diesel-Electric:
- Crew: 75
- Pass: 10
- Cargo: 30 tons
- CTRL Mod: -10/+16
- Speed (base/max): 4/70
- Defenses (Prm/Frt/Ref): 6/25/2
- Hard/DR: 5/10
- HP: 100
- Size: C
- Abilities (Str/Dex/Int): 15/18/14
- Weapons or Special Equipment: 8x colossal torpedo tubes (F) with 20 colossal torpedoes and 10 colossal missiles (extended range, standard speed).
- Adj Level: 12
- Purch DC: 54(M)
Guided-Missile Submarine, Nuclear Powered:
- Crew: 50
- Pass: 5
- Cargo: 10 tons
- CTRL Mod: -9/+14
- Speed (base/max): 3/50
- Defenses (Prm/Frt/Ref): 4/23/2
- Hard/DR: 5/10
- HP: 80
- Size: C
- Abilities (Str/Dex/Int): 12/20/12
- Weapons or Special Equipment: 8x colossal torpedo tubes (F) with 20 colossal torpedoes. Mast launcher with 4x medium missiles (extended range, high speed) (T).
- Adj Level: 11
- Purch DC: 50(M)
- Crew: 100
- Pass: 50
- Cargo: 50 tons
- CTRL Mod: -11/+18
- Speed (base/max): 4/60
- Defenses (Prm/Frt/Ref): 4/28/0
- Hard/DR: 5/15
- HP: 120
- Size: 1XC
- Abilities (Str/Dex/Int): 18/16/16
- Weapons or Special Equipment: 6x colossal torpedo tubes (F) with 20 colossal torpedoes. 50x colossal missiles (all are standard speed, half are standard range and the other half are extended range) in vertical launch tubes (T). 2 dive locks. Docking clamps for 2 diver subs.
- Adj Level: 12
- Purch DC: 55(M)
Ballistic-Missile Submarine, Nuclear Powered:
- Crew: 2
- Pass: 6
- Cargo: 1,000 pounds
- CTRL Mod: -8/+10
- Speed (base/max): 2/20
- Defenses (Prm/Frt/Ref): 5/23/7
- Hard/DR: 5/2
- HP: 30
- Size: H
- Abilities (Str/Dex/Int): 10/12/-
- Weapons or Special Equipment: Crew and passenger compartments are open to the water, and so personnel must use underwater breathing gear. This vehicle provides supplemental breathing gas sufficient to supply the crew and all passengers for up to six hours.
- Adj Level: 4
- Purch DC: 41 (M)
- Crew: 140
- Pass: 20
- Cargo: 100 tons
- CTRL Mod: -12/+17
- Speed (base/max): 4/50
- Defenses (Prm/Frt/Ref): 2/30/-2
- Hard/DR: 5/15
- HP: 150
- Size: 1XC
- Abilities (Str/Dex/Int): 16/14/16
- Weapons or Special Equipment: 4x colossal torpedo tubes (F) with 10 colossal torpedoes. 20x 6XC missiles (high speed, extended range) in vertical launch tubes (T).
- Adj Level: 12
- Purch DC: 56(M)
- Crew: 300
- Pass: 30
- Cargo: 100 tons
- CTRL Mod: -12/+18
- Speed (base/max): 4/70
- Defenses (Prm/Frt/Ref): 4/36/-2
- Hard/DR: 5/15
- HP: 200
- Size: 1XC
- Abilities (Str/Dex/Int): 17/18/18
- Weapons or Special Equipment: 30x 1XC missiles (all high speed, half standard range, half extended range) in vertical launch tubes (T). 70x Colossal missiles (all standard speed, 40 extended range, 20 standard range, 10 torpedo missile) in vertical launch tubes (T). 8x Gargantuan torpedo tubes (4 PL, 4 PR) with 20 Gargantuan torpedoes. 1x 5-inch naval gun (PF) with 200 rounds of ammo. 2x 20mm Gatlings (1 PF, 1 PA) with 5,000 rounds each. Helicopter pad and hangars for 2 helos.
- Adj Level: 12
- Purch DC: 52 (M)
- Crew: 3
- Pass: 3
- Cargo: 500 pounds
- CTRL Mod: -5/+6
- Speed (base/max): 20/300
- Defenses (Prm/Frt/Ref): 7/18/8
- Hard/DR: 5/5
- HP: 40
- Size: G
- Abilities (Str/Dex/Int): 12/12/14
- Weapons or Special Equipment: 4x Hardpoints. 1x 50-cal machine gun in door (PL OR PR) with 1,000 rounds of ammo. Dipping sonar OR 10 sonobuoys.
- Adj Level: 9
- Purch DC: 40 (M)
"You’re entitled to your own opinions. You’re not entitled to your own facts."
-Daniel Patrick Moynihan