Ad Astra! is a webcomic written and illustrated by A.R. Bowman. It is an original story based on the fictional setting and rules system of the Traveller role-playing game. The following links take you directly to each episode; there are also links on each episode's page to navigate forwards and backwards:
Traveller is a science-fiction RPG first published in 1977 by the Game Designers' Workshop (GDW Games). This makes it the oldest (and probably the most popular) science-fiction RPG ever. Various different editions of the game are still produced by certain publishers.
The author can be contacted through his account on RPG Geek: Judge Death.