From the back of the book:
Orbital 2100 is a science fiction setting for Cepheus Engine and other Classic 2D6 SF games. It has a realistic (TL 9) feel that is set within our own solar system. The Earth us locked in a Cold War with the people of Luna. Both face off, 400,000 km apart, threatening mutual annihilation whilst they compete to colonise the moons of Jupiter and Saturn. Older colonies such as Mars and Mercury are independent and caught up in this struggle for solar system supremacy. Spacecraft use nuclear thermal rockets and create gravity by spinning pods or centrifuges, this is spaceflight as envisaged today!
In keeping with the near-future and hard-science fiction themes, role-playing campaigns focus on real people doing real jobs. The game has rules, technology and advice to allow scenarios based around deep space haulage, asteroid mining, salvage, rescue and exploration.
Should the referee and players decide to stick with the default campaign premise for Orbital, then the player characters will be spacers, the rough and tough crew of a deep space vehicle owned by a corporation that leases its spacecraft out to agencies, individuals and corporations. Like the crew of a salvage or heavy lift ship today, the characters will find themselves engaged in diverse, challenging and dangerous jobs with every mission.