Engine problems look set to delay the flight from the planned date in December to sometime in February.
"They had an engine test they didn't like so they will do another month of testing," said Charles Chafer, chief executive at Space Services Inc.
The plan to send the ashes into space, along with fans' tributes, were set in motion soon after the Canadian actor's death in July aged 85.
One Trekkie fan has suggested a possible cause for the delay: "The engine imbalance is what caused the worm-hole in the first place. It'll happen again if we don't fix it." Presumably if repairs fail they will have warp drive on standby.
Another fan was more upbeat: "Any man who could perform such a feat, I wo'd na dare disappoint. She'll launch on time. And she'll be ready."
But it remains unclear whether the rocket will be heading for Deep Space Nine or holding a steady course before it makes First Contact. One thing is sure: Scotty's remains will boldly go where no ashes have gone before.
Tributes from fans will accompany his ashes on the flight, which will also carry the remains of 200 other people. Fans have been posting tributes to Doohan on Space Services' website.
Doohan's remains, which will be placed into a tube ejected from the Falcon One rocket, are expected to orbit Earth for up to 200 years before eventually burning up when they re-enter the atmosphere. There are two price plans for the flight from the Vandenberg Air Force Base: $995 (£579) and $5,300 (£3,082).
Doohan had been a successful character actor on radio and TV before landing the role in the pilot Star Trek episode in 1966.
Although he became synonymous with the line "Beam me up, Scotty," it was never actually said in the series.
The closest William Shatner's Captain Kirk character came to saying it was in the fourth Star Trek movie, when he said "Scotty. Beam me up."
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