You don't have to be a 'rocket scientist' [=you don't have to be unusually smart] to understand the instructions.
Sales 'rocketed' from 1,000 units last week to 5,000 units this week.
The job is challenging, but it's not exactly 'rocket science'.
(..) ...so we have to assault with tanks, we roll in the streets. So they send us in first to squat... ...make sure that there are no little.... No Vietnamese waiting with B- rockets to blow the tanks away. So we clear it out and we roll the tanks in... ...and basically blow the place to hell. (..)1987 Full Metal Jacket