Take a look at the original sentence again:
The terrified passengers aboard the 747 gripped their armrests as the jet
bucked in a bad stretch of turbulence after
a ride like this one, everyone knew that five minutes on Disney's Space
Mountain would feel like relaxing in a rocking chair.
You wanted to fix it this way:
The terrified passengers aboard the 747 gripped their armrests as the jet
bucked in a bad stretch of turbulence, after
a ride like this one, everyone knew that five minutes on Disney's Space
Mountain would feel like relaxing in a rocking chair.
To add a comma between turbulence and after would cause an equally bad problem, a comma splice. A comma splice occurs when you have two complete sentences joined with just a comma. The terrified passengers aboard the 747 gripped their armrests ... begins the first sentence. After a ride like this one, everyone knew ... starts the second sentence. The spot between turbulence and after needs a stronger break than a mere comma.
You might want to consult the rules for fixing comma splices and fused sentences.
Go back to the sentence to try again.