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Beyond Book 2: Expanding the Basic Classic Traveller Starship Design System

This article was originally posted to the pre-magazine Freelance Traveller website in 2002, and appeared in this form in the April/May 2015 issue


When Traveller premiered in 1977, it was printed in the usual three-book format of the period. The starship design system (filling most of Book 2: Starships) was a simple building-block system for ships of 100-5000 tons, with the “standard” designs provided for player-characters ranging from 200-800 tons. All in all, a “small-ship” universe, probably in a “cozy” campaign setting of a subsector or two.

But this was 1977, only months after the premiere of Star Wars, with its Galaxy-wide Empire and huge starships. The only other widespread universe paradigm was Star Trek, another big-ship universe with ultra-high “Trek Tech”. Both of these paradigms emphasized big ships, maxed-out technology, and a wide-ranging campaign area.

Accordingly, early Traveller campaigns tried to push the limit, attempting large ships (up to tens of thousands of tons), a ruling Tech Level of 13-15, and empires about equivalent in size to the later Spinward Marches (a full sector of 16 subsectors).

With the publishing of Book 5: High Guard in 1979, and its revision of 1980 (the revision is generally referred to (unofficially) as “High Guard 2”), larger ships, with a slightly-more-complex design system (primarily geared towards warships) for ships of up to a million tons, were introduced. Traveller’s official universe, the Third Imperium, spanning dozens of full sectors, provided a big universe for these big ships.

Traveller campaigns of this period emphasized big ships, big campaigns, and Tech Level 15, either in the Third Imperium itself or freelance imitations of it. Travellers had their galaxy and large starships—but paid a price.

Most player-characters were still limited by price and numbers to the smaller ships from Book 2—the Type A Free Traders, Type R & M subsidized merchants, and Type T & C paramilitary craft. These ships which player-characters could reasonably expect to own and/or control had shrunk to insignificance beside the megaton monsters coming out of High Guard’s shipyards. In such a big pond, to become a big fish meant starting at or rising to the level of a high-ranking VIP in a strategic-level campaign. Such Imperia had lost their scale for the free-traders and adventurers that made up the typical player-charactersexcept for vermin and pawns skulking around the edges.

Gedankenexperiment: Low-tech Traveller

Sometime in the 1990s, I tried a thought-experiment. Instead of a TL 15 big-universe, big-ship campaign, why not go as far as practical in the other direction? One subsector (maybe two), TL 11 (with TL12 being gee-whiz cutting edge), exclusively using Book 2-designed starships. A “cozy” campaign universe—with 15+ years of hindsight, probably what Original Traveller did best. See how much you could do using only Book 2 starships.

It turned out you could do a lot. Many of the starships from this experiment are now published in The Shipyard—stretched versions of the Type As & Rs, large liners and bulk freighters of up to 6000 tons, heavy scouts, stretched and tweaked small craft, and multi-role refits for the ubiquitous Type T patrol craft.

However, for the Navy, pure Book 2 became a bit limited; there was little difference between a dedicated warship and a well-armed civilian one, much like wooden ships during the Age of Sail. To bring our interstellar navies up to the "modern era", a little High Guard retrofitting was in order.

The following additions to the Book 2 design system retrofit a little of that High Guard flavor without unduly stretching the basic design system:

High Guard 2 Retrofit: Armored Hulls

Book 2: Starships had no provisions for armoring the hull; Book 5: High Guard introduced the concept. Unlike later versions of Traveller (MegaTraveller and later), armoring a ship was a yes/no proposition, with no choice of material—you simply allocated volume to armor according to a formula, applied the cost formula, and that was that.

Armor Allocation
Tech Level Formula
TL7-TL9 4 (DesiredArmorFactor + 1)% of hull rate (tonnage)
TL10-TL11 3 (DesiredArmorFactor + 1)% of hull rate (tonnage)
TL12-TL13 2 (DesiredArmorFactor + 1)% of hull rate (tonnage)
TL14-TL15 1 (DesiredArmorFactor + 1)% of hull rate (tonnage)
Cost of armor is MCr(0.3 + (0.1 DesiredArmorFactor)) per ton

In combat, armor would reduce the number of damage-causing hits.

Damage Mitigation
Armor Factor Effective Damage-Causing Hits
Armor Factor 1 2/3 of hits cause damage
Armor Factor 2 1/2 of hits cause damage
Armor Factor 3 1/3 of hits cause damage
Armor Factor n 1/n of hits cause damage

High Guard 2 Retrofit: Missile Bays

Book 5: High Guard also introduced the idea of missile bays. A missile bay was essentially a giant missile turret, firing enlarged heavy missiles or “torpedoes”. Before the introduction of nuclear dampers and meson guns at TL12, missiles were the primary ship-killing weapon.

Missile Bays
Type Tonnage Cost Crew Capacity Rate of Fire
Small Missile Bay 50 tons MCr12.5 2 50 5/turn
Large Missile Bay 100 tons MCr21 2 100 10/turn

Heavy Missile

An enlarged missile fired from Missile Bays. Commonly called a “torpedo” or “bay missile” to distinguish it from the smaller “turret missiles”. Heavy missiles are one ton each, cost five times as much as a standard (“turret”) missile, and do 1D1D damage.


Mines in Traveller are basically encapsulated light (turret) or heavy (bay) missiles with a special “mine” fire-control/IFF package attached. Instead of being fired directly, they are “laid” in orbital or drift minefields and float in space until activated by coded signal. Once activated, they launch themselves at a target, usually an intruding ship. When a mine fires, it attacks with the EW rating of its Tech Level.

There are four levels of activation:

Weapons Hold:
Fire only on direct command signal to fire, only at target specified in command.
Weapons Tight:
Fire only on targets positively identified as enemy.
Weapons Free:
Fire only on targets not positively identified as friendly.
Fire on anything and everything within range.

In addition, the fire-control package is “smart” enough to obey simple commands like “fire on the first target in range”, “let the first x targets pass, then fire at the next”, “deactivate at a specified time and reactivate later”, “deactivate until receiving new activation signal”, etc.

High Guard 2-inspired Enhancment: Laser Bays

Although not part of Book 5: High Guard, laser bays are an obvious extension of the missile bay concept to lasers: a giant laser turret, mounting 30 lasers firing as one. (These were used in the Foible Federation campaign of 1977-78, where they were known as “bank lasers”.) Laser bays require 10 tons of volume and a crew of 2; the cost to add a laser bay to a ship is MCr16 for pulse lasers, or MCr31 for beam lasers.

Essentially, a laser bay is 10 triple laser turrets ganged together into a single mount for savings in cost and personnel. A laser bay fires as a laser turret with only one “to hit” throw for the entire bay; a hit does 30 hits to the target ship.

Laser bays are found only on military ships as “big guns”.

Enhancement: Multiple Engines

In the original Book 2 starship design system, M-drives, J-drives, and Powerplants were fixed sizes (rated by letters in the usual A-Z sans I & O progression) that cross-indexed into hull size to give the drive and powerplant ratings for the ship.

This resulted in a “topping out” effect at larger hull sizes; the largest (Z) engine could only give a rating of 4 (Jump or Gs) in a 3000-ton hull, 3 in a 4000-ton hull, and 2 in a 5000 to 6000-ton hull. (And, presumably, 1 in a 10000 to 12000-tonner.)

Also, since engine damage was counted by derating the engines to the next (letter) size with each hit, ships above 2000 tons were progressively more vulnerable to engine hits, until a 5000+ tonner was as prone to “one-hit cripples” as a 200-ton Free Trader.

These limitations can be mitigated by allowing a “cluster” of multiple engines in a single hull. Multi-engined large ships can increase performance over single-engined ships, while absorbing more engine damage.

Design Limitations:
  1. All M– and J-drives, and powerplants in a multi-engine ship must be of the same (letter) size.
  2. Each engine in a cluster must have a rating of at least 1 for the size of hull. (This effectively limits Book 2 engines to a maximum hull size of 12000 tons, reasonable for a “small-ship” campaign.)
  3. Each jump drive or powerplant has the same fuel requirements as it would if installed alone. (This has no effect on jump fuel, but brings the Book 2 “ten tons per powerplant number” a little more in line with reality for large ships.)
  4. The drive/powerplant rating for the ship is the sum of all the engine ratings.
In-use Effects:

High Guard 2 Retrofit: Nuclear Missiles

Before the introduction of nuclear dampers at TL12, nuclear missiles (“nukes”) were the heavy-duty ship-killing weapon.

Nuclear missiles are available at TL8+ (while nukes are TL6, getting a small and efficient enough warhead requires a tech level or two more), do 1D the damage of a normal (HE/fragmentation) missile; for simplicity, radiation effects are assumed to be part of the normal damage.

Nuclear turret missile: 1D1D (same as a normal bay missile).

Nuclear bay missile: 1D1D1D.

Cost (when available): 10 a normal missile of the size, more for “Thunderballs”.

Nukes are a mass-destruction weapon, and are tightly-controlled by the military. They would be found only on actual military ships as a “special round”. (At least officially; such a firepower-multiplier is in demand on the black market under the name of “Thunderballs”.)

High Guard 2 Retrofit: Nuclear Dampers

Nuclear dampers are “shields” that neutralize nuclear warheads by varying the strong and weak nuclear forces. First described in Book 4: Mercenary, dampers project an interference pattern of strong- and weak-force nodes from two widely-separated antennae which interfere with nuclear fission and fusion reactions, causing the warhead to fail in a meltdown or much-reduced explosion. The pattern must be focused to hold a node on the incoming missile; for this reason, nuclear dampers require active sensors and precise fire-control.

In CT, nuclear dampers “fire” defensively on incoming missiles, with the base “to hit” throw (as a laser) with an additional DM of the relative Tech Levels of the missile and the damper. If the damper “hits”, the nuclear missile will not explode. Note that nuclear dampers have no effect on normal missile warheads.

Nuclear dampers are available starting at TL12:

Nuclear Dampers
Tech Level Tonnage Cost Crew
TL12 50 MCr50 4
TL13 20 MCr45 4
TL14+ 10 MCr30 4

High Guard 2 Retrofit: Rapid Launch/Recovery Facilities

Though small craft can be launched rapidly (ask anyone who’s seen a full abandon-ship), they are difficult to recover using standard shuttlebay fittings. Rapid Launch/Recovery Facilities (such as on carriers) allow a ship to launch and recover small craft or ship’s vehicles quickly. Book 5: High Guard called these “launch tubes”.

Rapid Launch/Recovery Bays require 25 times the tonnage of the largest craft to be launched/recovered through the bay, and 10 crew. Each bay uses ten hardpoints, and costs Cr2000 per ton displacement. 40 small craft can be launched or recovered per turn.

Each bay requires attached hangar space of 1.3 times the capacity in small craft tonnage, at a cost of Cr2000 per ton displacement. The extra room is required for marshalling the small craft to and from the launch/recovery bay.

Miscellaneous Note: Adapting "Wet-navy" Ships

A lot of the warship designs done under this system (such as the Kanin, Krupny, Venetian, Worcester, and Mogami) were “Travellerizations” of actual wet-navy ships.

These were mostly scaled from the armament, using the following rules-of-thumb:

Triple laser turrets
represent either a twin 40mm or single three-inch (75-76mm) gun mount.
Laser Bays
represent a twin gun turret of five to six-inch (120-155mm) caliber. (Heavier-caliber main guns are outside of this system, but can be represented in High Guard by the varying sizes of spinal-mount main batteries.)
Missile Bays
represent TL6 torpedo tubes or TL7+ missile launchers. A 50-ton bay represents a two- or three-tube torpedo mount or a single-arm missile launcher; a 100-ton bay represents a four- or five-tube mount, a twin-arm launcher, or a VLS missile array.
Rapid launch/recovery facilities
represent a dedicated aircraft-handling flight deck such as on an aircraft carrier; packing a couple fighters in a shuttlebay represents the limited helicopter capability of most TL8+ warships.