Friday, February 21, 2020

Third Imperium - Starships and Space Combat


In the Imperium, a "starship" is a spacecraft that is equipped with a Jump Drive. A spacefaring craft that is not equipped with a Jump Drive is simply a spaceship, a ship, or a small craft. Spacecraft are rated in "dtons", which stands for "displacement tons", meaning the volume displaced by one ton of liquid hydrogen. A ship must be at least 100 dtons in size to accommodate the power plant, drives, and fuel required to be jump-capable. The term "small craft" is usually reserved for spacefaring craft that are smaller than 100 dtons in size. Ships that travel between stars via slower than light methods such as, sleeper ships or generation ships, are not classified as "starships", but are merely "spaceships". While cruisers, battleships, and dreadnoughts displacing 50,000, 100,000, and even 500,000 dtons are in service, most characters will deal with much smaller ships such as the 100 dton Suleiman-class scout/courier, the 200 dton Beowulf-class free trader, the 200 dton Empress Marava-class far trader, or the Animal-class 200 dton safari ship.

Typical Starship Crew

Running a starship competently requires crew members with a certain array of skills. Running a starship well requires a crew with a more extensive range of skills. Listed below are both the minimal required range of skills and the more expansive range of skills that well-run ships have available.

Bridge Crew

Every starship requires someone with the Pilot [Starship] skill and the Astrogation skill if it wants to successfully use its Jump Drive. Spaceships should have a crewman with the Electronics Operation [Sensors] skill and a crewman with the Electronics Operation [Communications] skill. Although not absolutely necessary, a crewman with the Computer Operations skill is highly recommended. If a ship is equipped with defensive screens such as black globe generators or meson screens, then a crew member should have the Electronics Operation [Force Field] skill. Most ships that player characters have access to are not large enough to have defensive screens. Ships that expect to go into combat usually have a commanding officer with the Leadership and Tactics skills. Note that having a commanding officer with Leadership can give crew members bonuses (and help them avoid penalties) to their skill rolls by coordinating their actions through orders (via a Leadership skill check).

Given that starships are regularly completely cut off from the outside world for week long periods, having crewmen who can perform maintenance and repairs on the various systems on a ship is recommended. A character with the Computer Programming skill and a character with the Electrician, Electronics Repair, or Engineering [Electronics] skill (or some combination of the three) is advisable.

Engineering Crew

A starship should have at least one crewman with the Engineering [Starship] skill as well as crewmen with the Mechanic [J-Drive], Mechanic [M-Drive], and Mechanic [Power Reactor] skills. For starships, a crewman with the Mechanic [J-Drive] skill is critical if the ship intends to try to enter jump-space at any point. Having crewmen with the more specialized Engineer [J-Drive], Engineer [M-Drive], and Engineer [Power Reactor] skills is optimal, especially if the ship intends to be in service for long periods of time. As with the bridge crew, having crewmen who can perform routine maintenance and repairs on the ship is recommended. Having a crew member with the Machinist skill allows for the creation of replacement parts while in flight.

Weapons Crew

Armed ships should have a crew member with the Gunner [Laser] or Gunner [Missile] skill, or both for every turret carried by the ship. Larger ships that have weapon bays or spine mounted guns have larger weapon crew requirements, but most of those ships are so large that he chance one will ever come under the control of a player character is remote.

Medical Crew

As noted before, most starships can expect to be regularly out of communication with the rest of the universe for periods of at least a week at a time. Starships that journey into unknown or hostile areas can expect to be isolated from assistance for longer periods. Consequently, most starships carry at least some medical crew. Crew members with the skills Diagnosis, Physician, and Surgery are generally considered to be an integral part of a ship's crew. Ships that carry passengers always have medical personnel. Within the Imperium, ships that carry low-berths are required to have trained medical personnel as part of their complement.

Miscellaneous Crew

Ships that carry small craft such as air rafts should have at least one crew member with the Pilot [Small Craft] skill. It is recommended that the crew include someone with the Engineering [Small Craft] and Mechanic [Small Craft} skills as well. Ships that intend to carry cargo will find it advisable to have crew members with the Freight Handling and Merchant skills. Ships that carry passengers often find it necessary to include crew members with the Diplomacy and Savoir-Fair skills.


Jump is a means of travelling faster than light by way of entering jump-space. Jump is also the only means of faster than light travel in the Traveller setting. Ships in jump-space are isolated and may not communicate with or be detected by anything in normal space. A ship in jump-space may also not communicate with or be detected by anything else in jumps-space. Jump drives are rated from Jump-1 to Jump-6, which measures the maximum range in parsecs the drive can convey a ship in a single jump. A starship can make a jump equal to or less than its maximum jump range, but normally only in even parsec units - the only exceptions are mishaps or micro-jumps. No matter how far a starship travels, a jump takes roughly a week (specifically 168 hours plus or minus 0% to 10%). Powering a jump requires liquid hydrogen which both powers the creation of the "hole" into jump-space, serves as coolant for the Jump Drive, and provides the jump "bubble" that separates the ship from jump-space while it is in transit. Every jump requires 10% of the ships tonnage in fuel per parsec traveled - even though every jump takes roughly the same amount of time, longer jumps consume substantially more fuel than shorter jumps. A micro-jump counts as 1 parsec for the purpose of fuel consumption.

Skill Checks for Jump

A successful jump requires three skill rolls: A Pilot [Starship] roll, an Astrogation roll, and a Mechanic [J-Drive] roll. If any of these rolls fails, then something will go awry in the course of the jump. A critical failure on any of these rolls can be disastrous. Flying a ship using unrefined fuel imposes a -2 penalty on all of these skill checks. The potential results of a failed check are:
  • Pilot [Starship]: A failed Pilot [Starship] check results in no jump. In a no jump, the jump drives simply fail to operate.

  • Astrogation: A failed Astrogation roll results in a misexit from jump-space. A misexit usually occurs near a world in the destination star system or in deep space as the ship exits jump-space near an unexpected stellar object, planet, comet, or asteroid. A disastrously bad Astrogation roll could result in a misexit in the starting star system as the ship exits near a gas giant or other planet in the originating system.

  • Mechanic [J-Drive]: Failures involving Mechanic [J-Drive] rolls are called misjumps, and can have the most dramatic effects. A misjump can take the form of a no jump, a failed jump, or a misdirected jump. A no jump is identical to the no jump described for a failed Pilot [Starship] roll. A failed jump results in the ship entering jump-space for a week and then exiting in roughly the same place that it started. A misdirected jump or misjump results in the ship emerging from jump-space in an unintended location, usually far in distance and location from the intended destination - misjumps of 30 parsecs are not common, but they are not unheard of either. Until a ship exists jump-space, it is impossible to tell the difference between a failed jump and a misdirected jump.

  • Disaster: A critical failure on any of the three required skill checks results in a disastrous outcome. In addition to the possibility of a misexit, failed jump, or misdirected jump, a disaster may result in the ship being damaged in transit, or potentially even destroyed entirely.
Note that while a ship cannot be detected or communicated with while in jump-space, it can be detected while entering and exiting jump-space using starship sensors. A series of successful Electronics Operation [Sensors] rolls can detect a ship entering jump-space and determine the approximate size of the ship, the time it left the system, and the direction of the jump, although there is no way to determine the distance of the jump. A similar series of Electronics Operation [Sensors] skill checks can detect a ship leaving jump-space as well as the approximate size of the ship, the distance it traveled in jump-space, and the time it entered the system.

Jump Types

When starships emerge from jump-space, they retain the same vector they had when they entered jump-space. As stars (and everything else) are also moving through galactic space, this vector is also imparted to a jumping ship. This means that a ship can choose to try to take advantage of this fact by coordinating its velocity and direction when it enters jump-space with its hoped for speed and direction when it exist jump-space. This results in different types of jumps as follows:
  • Standing Jump: A standing jump is calculated to give the jumping ship the same vector as the destination system. This is usually the safest type of jump, as it minimizes the possibility of colliding with an unanticipated object in deep space.

  • Running Jump: A running jump is made with high speed upon entering jump-space. If properly calculated, the ship only needs to decelerate as it approaches its destination at the end of its jump. If poorly calculated, the ship will exit jump space with a vector that may place it wildly at odds with its intended destination and might be required to make substantial course corrections.

  • Micro-Jump: A micro jump is a jump within a single star system. As with all jumps, a micro jump takes about a week, and it uses up as much fuel as a one parsec jump. In some cases, a micro jump is a quicker way to move about a star system than using M-drives.
100-Diameter Limit

Matter in normal space interferes with ships in jump-space. If a ship in jump-space passes within a 100-diameter sphere of an object of more than 1 mile in diameter, the ship is usually "precipitated out" of jump space into normal space. This tendency tends to protect ships from exiting jump-space within another object. The primary job of a ship's Astrogator is plotting a course that avoids such objects to prevent exiting jump-space early. It is possible to enter jump-space within the 100-diameter limit, although it makes a successful jump more difficult. Attempting to jump from within the 100-diameter limit imposes a -4 penalty on all three of the required jump-related skill checks. Attempting to jump within 50 diameters of an object imposes an additional -4 penalty on all such skill checks, while attempting to jump while within 10 diameters imposes a further -4 penalty to jump-related skill checks. These penalties are cumulative, so attempting a make a jump from within 10 diameters of an object using unrefined fuel requires all checks to be made at a -14 penalty.

Any failure of one of the three required skill checks while attempting a jump from within the 100-diameter limit results in a misjump, with potential effects identical to a normal failure of the Mechanic [J-Drive] skill roll. Many of the most dramatic known misjumps are the result of crews attempting to jump from deep within the 100-diameter limit.

Spaceship Combat

Space combat in Traveller takes place on a two-dimensional hex map. Once again, this is an abstraction made for game-play reasons. One could construct a means of conducting combat in three dimensions, but that would be more time consuming than practical. Each hex in space combat is approximately 10,000 miles across. For reference, this means that the Earth and the Moon would be 24 hexes apart. Earth is about 0.8 hexes in diameter, and the Moon would be 0.2 hexes in diameter. On this scale, a light-second is about eighteen hexes.

Combat takes place in 20 minute turns, with each turn comprised of seven phases. Each ship is represented by two counters: One showing its current location, and one showing where it will be next round (its "vector counter"). Note that action in these phases is more or less simultaneous. All ships make detection rolls, then all ships engage in maneuvers, and so on. The seven phases are:
  • Detection and Communication: Ships can make Electronics Operations rolls for each type of sensor they have (usually some combination of Radscanners, PESA, and AESA). If a ship has multiples of the same type of sensor, they only make one check for that type using the one with the combination of operator skill and scan are the highest. One individual may make checks for more than one type of sensor, but each extra sensor that a character tries to use imposes a -2 to all of his Electronic Operation [Sensor] rolls as he has to divide his attention among multiple systems. Note that beam weapons can only be directed against foes detected with AESA or PESA. Detecting an object with one type of sensor does not automatically detect it with other types of sensor, although it can give a bonus to do so. Radio communications must be declared in this round, but if communications are opened, they may be conducted freely throughout the round.

  • Maneuver: All ships with working maneuver drives may maneuver, starting with the ships with the lowest acceleration and then proceeding in reverse order to the ship with the highest acceleration. If two ships have the same acceleration, then the larger ship goes before the smaller ship. If the ships are still tied, then their commanding officer (or pilot) must engage in a contest of tactics skill with his counterpart from the the opposing ship, with the winner going second. The pilot (or gunner for a missile) determines how the spacecraft will maneuver by placing the ship's vector counter a number of hexes in any direction to a maximum of that ship's acceleration. Ships that have an acceleration rating of less than one G can only accelerate fractions of a hex each round (meaning their maneuvers are only effective once every couple of rounds).

  • Movement: In the movement phase all ships move according to their movement vectors determined in the previous phase. Basically, place a placeholder counter on the ship's current location and move the ship to the vector counter location. Then take the vector counter and place it the same number of hexes away from the ship as the ship is from the placeholder along a straight line drawn from the placeholder to the ship. Spacecraft that pass close to objects with lots of mass, such as a planet or moon, will have their motion affected by the gravity of such objects. If a spacecraft's movement intersects with a planet, the ship may collide with the planet or land on the planet. If a ship (or missile) ends its movement in the same hex as another ship, it may attempt to ram the other ship.

  • Direct Fire: Ships may fire beam or gun weapons at one another in this phase. All combat is simultaneous, so all attacks are resolved before any damage is applied. Each gunner must choose whether to shoot and who to shoot at in this phase. Each gunner can only shoot at a single target in a round. Each weapon only makes one attack roll in a round - weapons with a high rate of fire gain a bonus to their attack roll rather than multiple attacks. Gunners attack using their appropriate Gunner skill, with an attack roll scoring a number of hits equal to half the margin of success of the attack roll (rounding down, with a minimum of 1). Spacecraft with at least 0.1 G of acceleration may attempt to Dodge incoming fire. Ships attempting to ram other ships may not Dodge point defense fire. Once all attacks are calculated and applicable Dodge rolls made, all damage is applied to all ships that suffered hits.

  • Collision and Point Defense: Ships attempting to ram other spacecraft do so in this round. Defending spacecraft may use point defense fire as a last resort, attempting to destroy an incoming "ramming" opponent. Attacks are made as normal for beam weapons in a point defense attack, but gain bonuses due to the close range. A single gunner may make multiple point defense attacks depending upon the rate of fire of his weapon. If both spacecraft are attempting to ram one another, the collision automatically happens. Otherwise, the pilots of the respective ships engage in a contest of Piloting skill (Gunner's piloting missiles use their Gunner skill for this contest). If the rammer loses or ties, it misses the target. otherwise, the collision happens. Ramming an asteroid, moon, or planet usually won't destroy the target, but can devastate an area.

  • Launch/Docking: Ships can launch missiles and other craft in order from lowest to highest captain initiative (conduct a contest of Tactics skill among the commanders of the various ships to determine this initiative order, with the ships with the better results going after the ships with the worse results). Ships can also dock with other ships if they have matched courses and velocities. One of the two docking spacecraft must be able to maneuver, and the other must either cooperate or be crippled and unable to maneuver. Neither spacecraft may maneuver in the next combat round, and the docking maneuver isn't complete until the start of the next docking round. Docking can be performed more quickly, taking only a single docking phase to complete, but doing so requires a Piloting skill roll and the ships suffer collision damage if this skill roll fails. Docked spacecraft can maneuver while docked provided they continue to match courses and do no exceed 1 G in acceleration. Undocking requires only a single phase and does not restrict maneuvering. A ship can recover smaller craft into a spacedocking or vehicle bay using the same procedures as required to dock with another spacecraft.

  • Damage Control: As the name of this phase implies, engineers on the various ships can attempt to repair damage to their spacecraft. An engineer can repair either hull damage, damage to a specific subassembly such as a turret or bay, or to a major subsystem such as the M-Drive or Power Plant. Such attempts require mechanic or Engineer rolls with penalties if the hull or subassembly is disabled. A chief engineer coordinating repairs can give other engineers a +1 to their skill rolls with a successful Leadership roll. The number of points of damage repaired are equal to the margin of success of the applicable engineer or mechanic rolls. Repair teams repair damage equal to the average margin of success multiplied by the number of members of the team. A critical success doubles the points of damage repaired, while a critical failure can cause injury to the engineers working on the system and additional damage to the ship. Repairs can be rushed, potentially restoring large numbers of hit points to the ship in a short time, but any failure is treated as a critical failure.
Small vessels often have a single crewman occupying multiple roles on a ship. If a crew member fills multiple roles during a space combat, he suffers -2 penalty to all skill checks for each extra task he is performing. Actions counted as a single task for purposes of space combat are: Piloting, firing a single weapon or set of linked weapons at a single target, controlling a missile or salvo of missiles, acting as a sensor operator, damage control, engaging in complex communications such as coordinating a squadron or tracking a signal, or operating a meson screen. For ships attempting to enter jump-space while in combat, Astrogation is counted as another task. If a ship has two or more crew members engaged in multiple tasks, it should have a commanding officer who does nothing but give orders who can make a Leadership roll; otherwise the crew will suffer an additional -1 to their skill checks.

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