In 1978, the now defunct company Heritage Models released a line of Star Trek miniatures. To go along with them, they also released Star Trek: Adventure Gaming in the Final Frontier – the first licensed RPG for Star Trek. This was a year before the first movie, and a decade before TNG, so it was based entirely on TOS and the animated series.
This game is obviously long out-of-print. No official PDF was ever released, though there are scans still floating around.
The rules are pretty simple. 3d6 for stats – D&D style. Some actions are determined by rolling the stat or less on a 3d6. Combat is handled with an opposed single die roll. Constitution is used for hit points.
There are Basic and Advanced versions of the rules. They’re both clearly explained with lots of examples, but the game does feel incomplete with some things missing (Skills, Character advancement, etc.). There are no starship rules. The whole thing feels very much like a set of miniature skirmish rules more than a full RPG. This is unsurprising, as it came from a miniatures company.
More surprisingly, there’s a small active forum about this game: https://oldschooltrek.proboards.com/board/6/heritage-star-trek-1978
The original rules suggested putting or of all the character stats on an index card. Since we’re now living in a futuristic, post-Eugenics Wars society, I thought we could use a nice PDF character sheet. It’s fillable, and will automatically calculate the bonuses for each stat, and a few other things. You can click in the upper right-hand corner to import an image. This is one of my ever-growing list of character sheets.
***UPDATE – I’ve made a revised version to fix a small error