He had hurled the rock not with his feet, but with a reaction drive.

A reaction drive is a weapon, powerful in direct ratio to its efficiency.

They're all just reaction drives and they're months from home.

That is a very effective reaction drive they are using.

It would have been impossible in the days of reaction drives.

The more efficient a reaction drive, the more effective a weapon it makes.

From there we had to proceed on reaction drive and gravity drag.

Their point defense missiles used reaction drives, for God's sake!

They must have a better reaction drive than we ever developed.

With a reaction drive, the motor and the fuel tanks take up most of the available space.