Various propulsion systems based on inertial forces.

Spacecraft side view

Centrifugal inertia propulsion system

Synchronous inertial force propulsion

The picture above is an imagination of an reaction engine similar to Harry Bull inventor invention form 1935. I improve this invention changing the position of reaction engines. In this position the result forces inside are almost equal zero because they act against each other thus external forces can gain the power which are also increased by external springs making particular impulse longer in time. The opposite masses are motionless and the reaction from those masses is null because they are mounted against each other.