Been trying to identify a book I read in the late early 90s for quite a few years now, It was a children's/ young adult sci-fi story.
Plots Summary/Details: A boy (teenager possibly) had accidentally stowed away on a spacecraft [named Orion, this may have been part of the title and was certainly the cover illustration] which had a experimental faster then light drive, called shifts or something similar, and had landed up on a distant planet; the ship returned automatically without him.
There were a race of 'dolphin like' aliens, who were slaves to a race 'horse like aliens' on said planet which the protagonists freed while trying to save the missing boy, before returning home, after having had their ship modified by the aliens.
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