Surface Action!

Surface Action! is a Striker II-based set of rules for aero-naval combat.  These rules are completely compatible with Striker II and may be used to resolve naval actions in any House Rules system.  Additionally, campaign rules are included which can be fully integrated into Striker II's campaign rules.  And finally, specific rules are given for resolving combat in the Space 1889 universe.

Conventions

Displacement Tons
The displacement tons referred to in these rules are Traveller displacement tons (14m�).

Tonnage
Tonnage refers to the metric mass of the vessel.

New Rules

Damage Control Crewmen:
Maintenance crew can be used in the damage control process, as can any gunners not firing their weapons that turn.

Green Crews
Green crews are not as well trained as Trained, Line or Crack crews.  To simulate this, it takes four damage control crewmen to reduce Waterline Hull hits by one per turn.  Additionally, each Green damage control crewman can reduce the level of fire by only 30 instead of 60 per turn.

Crack Crews
Crack Crews are top of the line, highly trained and motivated folks.  To simulate this, it takes only one Crack damage control crewman to reduce a Waterline Hull hit by one per turn.  Additionally, a Crack damage control crewman can reduce the level of fire by 120 instead of 60 per turn.

Flyer Movement
Flyers may climb one cm at the cost of 1cm of forward movement.  Flyers may dive 2cm at the cost of 1cm of forward movement.

Damage
Hits by weapons with a penetration less than or equal to the armor value have no effect.  For rounds which penetrate, roll 1D20 and compare the result to the vehicle's displacement tons.  If the roll is equal to or less than the size of the vehicle, roll on the Damage Severity Chart below.  If the roll is greater than the vehicle's displacement tons, the vehicle is completely destroyed and the crew is killed

Damage Severity Chart

1 Hit:  Roll once on the Damage Table below.  In addition, roll a Morale Check with a DM -1 for the aircraft pilot or boat CO.  If unsuccessful, the aircraft or boat breaks off the action and flees.

2 Hits:  Roll twice on the Damage Table below.  In addition, roll a Morale Check with a DM -2 for the aircraft pilot or boat CO.  If unsuccessful, the aircraft or boat breaks off the action and flees.

Critical:  Roll 1D10 times on the Damage Table below.  In addition, roll a Morale Check with a DM-3 for the aircraft pilot or boat CO.  If unsuccessful, the aircraft or boat breaks off the action and flees.

Damage Table
Roll 1D20 on the chart below and check the damage result.  The Armor column indicates which of the vehicle's armor values is used to determine penetration.

Notes
*Roll an additional damage result.
Belt or Belly:  Use the belt armor value for surface vessels and the belly armor value all other vehicles.
Hull/Superstructure:  Roll 1D6.  1-3 Hull, 4-6 Superstructure.   At long and extreme range substitute the deck armor value for any hull hits.   Attacks by flyers always use the deck armor value instead of the hull armor value.
Hull/Superstructure/Turret:  Use the appropriate armor value for the location of the gun.  If the gun is in an open mount and has a gunshield, use an armor value of 5 for the gun's armor.  If an open-mount gun has no gun shield, the armor value is 0. Hits by small arms, regardless of final penetration, do not affect guns; if the gun is in an open mount without a gunshield, mark the hits as crew casualties among the gun crew, otherwise the hit has no effect.

Results

Waterline Hull/Lifter: Divide surface vessel tonnage by 10. This is the number of hull hits per row. There are three such rows for each vessel. Each waterline hull hit causes flotation hits equal to the final penetration of the weapon minus the ship’s armor. This is the number of flotation hits marked off each turn. Each pump in operation reduces this damage by one per turn. Two damage control crewmen not otherwise occupied can reduce the flooding level by one per turn.  When the first row is completely marked off, the ship's speed is reduced by half.  When the second row is marked off, the ship is dead in the water.  When the third row is marked off, the ship sinks.

Early (TL 1-3) vessels do not have the watertight compartmentation that later ships do.  To simulate this, double all waterline hull hits against early tech level ships.

For flyers, divide the maximum altitude of the flyer, in meters, by 10. This is the number of rows of damage the flyer can take. Each row has check boxes equal to the displacement tons (14 m�) of the flyer. As each row is marked off, reduce the maximum height of the flyer accordingly.

Waterline hull/lifter damage is typically accompanied by other damage.  To simulate this, roll an additional damage result on the table and implement it immediately.  If waterline hull/lifter is rolled a second time, implement the damage and roll an additional result.  In this way it is possible to literally sink a large vessel or knock a large flyer out of the sky.

Cargo/Passengers: Tonnes of cargo equal to the final penetration of the round minus the armor value of the ship’s hull are destroyed. If the ship is carrying passengers, there is a 50 percent chance that passengers will be affected; in this case passengers equal to the final penetration of the round minus the hull’s armor value are made casualties. Passenger casualties do not count against the morale of the vessel.

Crew: Crew members equal to the final penetration of the round minus the appropriate armor value are rendered casualties. Divide the ship’s tonnage by 100. When the ship takes crew casualties equal to this number the commanding officer must check morale that turn and every subsequent turn. Subtract one from the CO’s morale for each morale check point reached. For example, the CO of a 13,000-tonne ship must check morale at a –1 when casualties reach 130, a –2 when casualties reach 260, a –3 when casualties reach 390, etc. Regardless of actual numbers, when a ship takes 50 percent casualties it will break off from combat if possible. If this is impossible, the CO rolls one more morale check with no modifiers. If he passes, the crew abandons ship and the ship is scuttled to prevent it falling into enemy hands. If he fails, the ship surrenders.

Fire: Divide the ship’s tonnage by 10. This is the maximum level of fire the ship can take. Subtract the armor value of the hull from the final penetration of the round to determine the initial level of fire. This increases by 60 every turn. Each damage control crewman not otherwise occupied can fight the fire, reducing its level by 60 each turn. If the fire ever reaches the maximum level, the ammunition and fuel aboard explodes destroying the vessel.  Fire results on a hydrogen-filled airship automatically destroys the airship.

Rudder/Screw: The vessel is reduced to half speed until the damage is repaired. Total the number of damage control crewmen working on repairing the damage — this is the number or less on 1D20 that must be rolled to repair the damage.

Engine: The engine is rendered inoperable and the ship is dead in the water. The vessel must be towed to dry-dock to affect repairs.  Additionally, no system requiring power may operate; this includes all pumps.  On sailing vessels and kites an engine hit destroys one mast.  On a man-powered craft such as a screw galley the final penetration minus the craft's armor value is the number of rowers or turncranks rendered casualties.   Fixed-wing or rotary-wing aircraft automatically crash, but the crew has time to bail out.  All uninjured crew are considered to have done so.

Fuel: The final penetration of the round minus the armor value of the hull is the percentage of fuel lost. This is also the percentage chance the fuel will ignite. If the fuel ignites, the percentage of fuel listed above is also the initial fire level.  If the vessel has no fuel, ignore this result.

Ammunition: The final penetration of the round minus the armor value of the hull is the percentage of ammunition lost. This is also the percentage chance the ammunition will explode. If the ammunition explodes, the ship is destroyed and the crew is killed.  If the vessel has no ammunition, ignore this result.

Pumps: Pumps equal to the final penetration of the round minus the armor value of the hull are destroyed.  If the vessel has no pumps, ignore this result.

Gun: If the final penetration of the round is greater than the armor value protecting the gun, the gun is destroyed and the crew become casualties.  If the vessel has no guns, ignore this result.

Radio/Sensor: One radio or sensor set is destroyed.

Sight/Vision: One sensor or vision aid is destroyed.

Advanced Rules

Collisions and Ramming
When two vehicles are within 1 cm of each other, there is a chance they will collide.  Avoiding a collision is a short-range task (include any target size modifiers), but both ships must pass the task.  If the vessels do collide, each vessel suffers waterline hull or lifter damage equal to the net speed of the two vessels, in cm, times the tonnage of the other vessel, minus the ship's belt or belly armor value.   If one ship was successful in its throw to avoid collision, halve the number of hits.

If the armor value of the vessel's belly or belt armor is greater than the other vessel's net speed times tonnage, no damage results, and no additional damage is rolled.

Ramming is handled the same way as a collision, except that the ramming vessel rolls to hit the other vessel, and only the attacker's roll gets the target size modifier.  If the attacker's roll succeeds and the defender's roll fails, implement damage normally.  If the attacker's roll fails, regardless of the defender's roll, no damage is done.  If both the attacker's and defender's roll succeed, halve the number of hits each vessel takes.  If the attacker is equipped with a ram, and succeeds in hitting the defender, double the number of hits against the defender and halve the number of hits against the attacker.

In both cases, roll one additional damage result on the table and implement immediately.  If an additional waterline hull or lifter hit is achieved, implement and roll again.  In this manner, a successful ramming or collision may sink the largest vessel or knock the largest flyer out of the sky.

In all cases, vessels and flyers of 10 displacement tons or less are destroyed by a successful ram or collision.

Running Aground
When a ship runs aground (enters water shallower than its draft), it takes waterline hull hits equal to its tonnage times its speed in cm minus its belt armor value.   Additionally, roll 1D20 for the number of turns the vessel remains stuck.  On a roll of 19 or 20, the vessel is stuck fast and must be pulled free by another vessel.

Towing
Flyers and vessels may tow one-another.  For every five-fold increase in tonnage the towing vessel must pull, reduce the vessel's speed by half.  For example, a 200 ton vessel pulling a 1000 ton vessel reduces its speed by half.  If it was pulling a 2000-ton vessel, it would reduce its speed to one-quarter.

Infernal Devices

Torpedoes
Treat unguided torpedoes as any other weapon, with a short, medium, long and extreme range.  Guided torpedoes are treated as guided missiles, with a single range - short.  In both cases, use any target speed and size modifiers.  Halve the target size modifier when firing from directly ahead or astern or the target. When determining the penetration of a torpedo, add the Traveller concussion value of the torpedo to its penetration value.

Aerial Torpedoes
Aerial torpedoes are treated as ship launched torpedoes with the following exception:  for every 10 cm of altitude from which the torpedo is dropped, increase the hit difficulty by one level.  For example, an unguided torpedo dropped from an altitude of 1 to 10 cm treats short range as medium, medium range as long, and long range as extreme.

Tether Mines
When deployed, tether mines float 1 to 20 cm above the deploying vessel or facility.  If the deploying unit flies directly beneath a flyer, or if a flyer passes directly above the deploying facility within the altitude range of the deployed tether mine, the mine may hit the flyer.  Both the flyer and the deploying unit roll a short range task, though the attacking player may use the target size modifier.  If the attacker is successful and the defender fails, the attack succeeds and damage is handled normally.  If the attacker fails and the defender succeeds, the attack fails.   If both succeed, halve the penetration of the torpedo before assessing damage. If both fail, the attack fails.

Drogue Torpedoes
When deployed, drogue torpedoes hang 1 to 20 cm below a flyer.  A flyer with its drogue torpedo deployed halves its movement.  If the flyer passes directly over another vehicle, and the vehicle is within the altitude range of the deployed torpedo, the flyer may attack the other vehicle.  Both vehicles roll a short range task, though the attacking player may use the target size modifier.  If the attacker is successful and the defender fails, the attack succeeds and damage is handled normally.   If the attacker fails and the defender succeeds, the attack fails.  If both succeed, halve the penetration of the torpedo before assessing damage. If both fail, the attack fails.

Barrage Balloons
Barrage balloons are suspended 1 to 40 cm above the vessel or facility which is deploying them.  Any flyer which moves above the vessel or facility within the altitude range of the deployed balloon collides with it.  When a flyer collides with a barrage balloon, the balloon explodes and the flyer suffers lifter hits equal to 1D20.   This roll is also the initial fire level started on the flyer by the explosion.   Additionally, all gun crews in open mounts become casualties and the flyer takes 1D10 additional casualties.

Torpedo Nets
Torpedo nets are either deployed or stowed.  Stowed torpedo nets have no effect.   Deployed torpedo nets quarter the deploying vessel's speed, but will stop any torpedo attacks from abeam on a roll of 1-12 on 1D20.  Attacks from directly ahead or astern are not affected by torpedo nets.

Spike Droppers
Flyers may drop anti-personnel spikes on other flyers or on surface vehicles or facilities.  Roll 1D20 and subtract the altitude difference, in cm, between the attacker and the defender.  The result is the number of crew casualties the target suffers.  Note that only crew members in exposed positions (open-mount guns, crew in open-topped vehicles, etc.) are affected.  If the number of hits exceeds the number of exposed crew, additional hits are wasted.

Liquid Fire
Flyers may drop liquid fire on other flyers or on surface vehicles or facilities.   Roll 1D20 and subtract the altitude difference, in cm, between the two vehicles.   This is the initial level of fire on the target vehicle.

Submarines
Submarines are treated in most respects as surface ships.  Submarines must be able to spot their targets in order to fire; submarines equipped with sonar can use the sonar to spot the target without coming to periscope depth; submarines not so equipped must use periscopes or surface to acquire a target.  Submarines at periscope depth may be spotted by flyers at one difficulty level higher.  Submarines using periscopes or snorkels may be spotted by anyone at normal difficulty levels.  Submarines using active sonar are automatically spotted by ships equipped with sonar.

Depth Bombs
Attacks against submerged submarines may be made with depth bombs.  The attacking player sets the depth of the bomb in cm.  If the submarine is within twice the burst radius of the bomb in any dimension, it is attacked with a penetration equal to twice the concussion value of the bomb.

Optional Rules

Scales
For really large actions, divide the ground scale ranges and movement by 10 and round to the nearest whole number.  This yields a ground scale of 1cm = 100m (1:10,000).  The turn length remains unchanged (5 minutes).

Abandon Ship
Crews may abandon ship before the vessel sinks or explodes.  The commanding officer must order the ship to be abandoned at least one turn before it explodes or sinks.  Roll 1D20 and multiply by 5.  This is the percentage of the surviving crew which successfully abandons ship that turn.  If additional turns are available, use the same procedure to determine how many of the remaining crew manage to abandon ship during each subsequent turn.

Campaign Rules

Campaign Turn
Each campaign turn is eight hours long.

Campaign Scale
The campaign is played upon a map with a scale of 20 km per hex.

Campaign Moves
Multiply the combat move of watercraft and long-endurance aerial flyers (grav vehicles, liftwood flyers, zeppelins) by three to determine the number of hexes the vehicle moves per campaign turn.

Logistics

Ammunition
Self Explanatory.

Fuel
Again, self explanatory.

Rations
Each crewman requires 25 kg of rations per week at a cost of Cr10.  The crews of TL 4- watercraft, and of long-endurance flyers of any tech level double the above ration requirements (the vehicle needs to carry water for the crew, too).  Storage for 100 kg worth of rations are included in the accommodations for the crewman; additional rations may be stored at 1 m� per tonne. 

In-Port Replenishment
Ships inport can take on tons of supplies equal to the ship's size, in displacement tons, divided by five, per tactical (5-minute) turn.  Consequently, ships can take on 20 tons of supplies per displacement ton of size per strategic (8-hour) turn.

Underway Replenishment
Ship's may transfer cargo at sea.  This is knows as underway replenishment.  To conduct underway replenishment, both vessels may not travel faster than half the speed of the slowest vessel.  Divide the displacement tons of the smallest vessel by 10, rounding fractions to the nearest whole number.  This is the number of tons of cargo that may be transferred between ships per tactical (5-minute) turn.  Consequently, ships can take on 10 tons of supplies per displacement ton of size per strategic (8-hour turn).