Main Mount Weapons

At Muan Kwoyen, Albadawi used the bulk of his “new model” battleships—capable of jump-3 and carrying spinal-mount meson weapons—to surprise the Vilani. Suddenly the Imperials faced numbers far greater than they expected. Worse, the Terran battleships poured long-range meson fire into the Imperial line of battle. The Imperials had never developed meson weapons of their own, and knew of them only from fearful ancient legends. Now the Core Fleet faced the mythical “certain death weapon” in bitter reality, as its proudest ships were destroyed by internal explosions. —Interstellar Wars.

As games evolve over different editions, legacy elements shift, mutate, and occasionally break or disappear altogether. These might be due to game-mechanical changes or setting-background changes, and might be intentional or inadvertent. For example, a spell or firearm that was wickedly potent in edition X might get nerfed badly in edition X+1, only to be restored to some measure of glory in edition X+2. Or an alien species or fantasy race that was utterly villainous in an earlier edition gets retconned into one that is admirable or sympathetic in a later one.

Traveller has seen plenty of these changes over many editions as well as translations into new mechanical systems like GURPS or Hero. Designers generally ensure a basic level of continuity, but sometimes things get lost in the shuffle. And perhaps the one area in Traveller most susceptible to incompatibility is starship design: these subsystems are usually very fiddly and it is not uncommon to find a design that worked in a previous edition does not work in a newer one.

I ran into this problem as I converted some older system defense boats and monitors into Mongoose Traveller 2e High Guard. While most elements translated fairly well, spinal weapons often posed a problem. In the Third Imperium setting, spinals are the apex ship weapons in a hierarchy that begins with small 1-ton turrets, moves up through larger barbettes to even larger weapon bays that range from tens to hundreds of tons in size. Spinals are larger still: generally thousands of tons in size, so big that they run the entire length of the ship and so dangerous they can destroy enemy vessels with one shot.

The Cause Rampant, a 60,000-ton Azhanti High Lightning-class frontier cruiser, returned to service in 1086. Note the new meson gun spinal which replaced the old particle acclerator.

MgT has two types of energy weapon spinals: particle beam and meson guns. Both weapons have been in Traveller since the original High Guard (1980). In the Traveller setting, meson weapons are a transformative technology able to penetrate the most advanced ship armor. The ancient Terrans were said to have defeated the much more advanced Vilani Imperium in part because the Vilani had no defenses against the new and devastating Terran meson weapons.

In MgT, spinals cannot occupy more than half the tonnage of their starship. The smallest particle beam spinal is a TL14, 2,800-ton model; the smallest meson spinal is a TL15, 6,000-ton unit. This means the smallest vessel to mount a particle beam spinal is 6,600 tons, and the smallest to mount a meson spinal is 12,000 tons.

The MgT rule is perfectly sensible from a game balance perspective, likely intended to prevent tiny ships from mounting weapons of incredible power. But older editions of Traveller allowed smaller ships to mount spinal weapons. For example, the TNE supplement Gilded Lilly 3: Out of the Darkness features a 5,000 ton Castle-class heavy SDB with a meson gun spinal.

Another change: in previous editions, going all the way back to the CT High Guard, much less powerful meson guns could be mounted in weapon bays as small as 50 tons. However, as Marc Miller worked on Traveller⁵ he evidently decided that he wanted to remove meson weapon bays from the game, at least for Adventure Class Ships of 2,400 tons or smaller. If this is correct, the change helps keep meson weapons special and out of the reach of most PCs. But this shift also potentially invalidates some older ship designs as well as the battlefield meson accelerator, a 15-ton ground-based weapon system that originated in CT Striker (1981).

While meson gun bays are available in MgT High Guard, they are presented as a “high technology” option not normally available in the Third Imperium setting. (A couple of the larger example starships, such as the Skimkish-class or Antiama-class carriers, do feature mesons bays, but it is unclear if this was an error or an intentional exception.)

But there might be another way to get meson weapons on smaller spacecraft. A large weapons bay in MgT High Guard is 500 tons, and as noted above the smallest meson spinal is 6,000 tons. That leaves a pretty huge gap between these two different mounts, and leaves space for a missing weapon mount category. 

As it happens, Traveller⁵ has a mount that falls between the two: Main Weapons, which are “larger than Bay Weapons, but fall short of the immense power of Spines” (T5 Book 1, 152). By introducing Main Weapons into MgT, we can mount meson weapons on smaller spacecraft while keeping with the retcons introduced by Traveller⁵.

Main Mount Weapons for MgT

Main mount weapons, sometimes called baby spinals or lances, are the largest mounts available to ships under 5,000 tons and resemble spinal weapons in several important ways, though they are not nearly as destructive as spinals.

The crew requirements for main mount weapons are 1 gunner per 100 tons of main mount weaponry. All main mount weapons suffer DM-2 when attacking targets of 5,000 tons or less, DM-4 when attacking targets of 1,000 tons or less, and DM-8 when attacking targets of less than 500 tons.

Main mount weapons use a number of Hardpoints equal to their tonnage divided by 100, rounding up. A ship can only mount a single main weapon, and cannot mount both a main and a spinal. A main mount weapon mount cannot exceed a tonnage equal to half that of the ship carrying it.

Main mount weapons are classed as Destructive, but multiply Damage by 50 rather than 10 as with other Destructive weapons.

As with spinals, main mount weapons can be of variable size. The Main Mount Weapons table shows the effectiveness of a main mount weapon at its Base Size (this is also its minimum size). For every multiple of the Base Size, the main mount increases its Damage, Power consumption, and cost by the amount shown.

Main Mount Weapons

Weapon	TL	Range	Base Size	Power	Damage	Cost	Max Size	Traits
Meson	13	Long	500 tons	+150	+2DD	+MCr250	5,000 tons	AP ∞, Radiation
Particle Beam	12	Long	300 tons	+150	+1DD	+MCr150	3,000 tons	Radiation

Meson main mounts ignore all armor.

Main mounts do not become smaller as technology advances, but instead reduce their Power consumption. Each TL improvement decreases Power consumption by -10% and increases the Cost by +10%, to a maximum of three increases or TL15, whichever is lower.

Postscript

Many thanks to the posters over at Citizens of the Imperium and the Mongoose Traveller forums for help with thinking through main mount weapons, in particular AnotherDilbert for offering his ship-design expertise.

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