Doohan, who played chief engineer Scotty in the cult sci-fi TV series and a number of films, passed away on July 20 2005 after losing his battle with Alzheimer's disease and pneumonia aged 85.
Instead of a regular funeral service, the star requested that his remains be launched into orbit, as a tribute to his most famous role.
Houston-based space burial firm Space Services had originally planned to blast Doohan's remains into the earth's atmosphere last year, but the proposed trip had to be delayed so further tests could be carried out on the rocket.
A spokeswoman for the company, Susan Schonfeld, has now confirmed a flight carrying Doohan's ashes - and the remains of 100 other people, including astronaut Gordon Cooper - will take place in October.
However, after this trip the rocket will return to earth with the capsules.
A second rocket flight, which will take place in December or January 2007, will blast Doohan's encapsulated remains into the Earth's orbit.
They will remain in orbit for a few years before falling and burning up in the Earth's atmosphere.
To mark the intergalactic 'burial', the actor's family will hold a service for 'Star Trek' fans so they can pay their final respects to the much-loved star.