Orion in Fiction
Empire of the Atom by A. E. Van Vogt, 1956.
Post-atomic-war interplanetary empire that uses Orion-type nuclear rockets for interplanetary spaceflight. The past atomic war was an interstellar war fought between humans and hostile aliens from another star somewhere between 800 and 8000 years before.
Footfall by Larry Niven and Jerry Pournelle. In the face of an alien siege/invasion of Earth, the humans must resort to drastic measures to get a fighting ship into orbit to face the alien fleet.
King David's Spaceship by Jerry Pournelle
Inhabitants of a planet that is to be re-admitted to the Empire plot to build the spaceship based on an Orion project concept in order to qualify their planet as a higher-developed, Class One Imperial world.
Orion Shall Rise by Poul Anderson.
A post-collapse confederation gathering forbidden nuclear materials for some unknown end -- although the title gives away the true nature of their mysterious project.
The Stone Dogs by S. M. Stirling
An Orion spacecraft is created during an arms race between The Domination of the Draka and the Alliance for Democracy, and used by both sides in their explorations of the solar system and as warships.
The Shiva Option by David Weber and Steve White
An arachnid homeworld is destroyed by converting several asteroids into Orion-drive starships and launching them at it.
Emprise, Michael P. Kube-McDowell
Orion used in the first book of the Trigon Disunity series.
Olympos, Dan Simmons
An Orion-style spaceship, designed by the Moravec machine race to emulate 21st century human technology.
Spaceship Messiah employs an Orion-style propulsion system. Built jointly by the United States and Russia to destroy a rogue comet, the vessel is explicitly constructed and launched from Earth orbit.