The original edtions of Star Fleet Battles included a preliminary set of rules for "sub-light battles". This covered the period of Y0-Y62, before the invention of Tactical Warp Power. Ships could (barely) move over strategic distances using a warp field generated by their impulse engines, but could not fight at speeds faster than light.
The rules were never really finished, and never really worked. The theory was to someday publish SFB MODULE Q: SUBLIGHT BATTLES. Various vague plans existed for this product, but no work was done on it. Speculation included the idea that it might even include a "momentum movement system" where ships could "coast along" without using their engines. Module Q became the first in a long series of "product titles which were never published". It never ranked very high in the polls of "which new product do you want" but to this day it has a small number of loyal fans.
We present below a copy of the original draft rules, some of the original sublight SSDs, and some SSDs that were created later by enthusiastic fans of the sublight era.
Will Module Q ever be published? Perhaps. It gets listed in player polls every year, and perhaps the data here will help its loyal fans build support for eventual publication.
Rules from the SFB Designer's Edition
SFB Sub-Light Game
Sub-Light Damage Allocation Chart
Module Q Rules PDF
Federation Sub-Light Heavy Cruiser SSD
Federation Sub-Light Light Cruiser SSD
Gorn Sub-Light Battleship SSD
Gorn Sub-Light Destroyer SSD
Klingon Sub-Light D6 SSD
Klingon Sub-Light Frigate F5 SSD
Kzinti Sub-Light Cruiser SSD
Kzinti Sub-Light Frigate SSD
Romulan Sub-Light Hawk Destroyer SSD
Romulan Sub-Light Warbird Cruiser SSD
Sub-Light Base Station SSD
Sub-Light Freighter SSD
Sub-Light Romulan Snipe
It should be noted that many of the Romulan "Eagle-series" SSDs already published have sublight versions which can be used with these rules.