According to the source, what is the practical limit on exhaust velocity for conventional, non-nuclear hot-gas rocket propulsion systems?

1. The source discusses exhaust velocity as the first of three factors affecting a rocket's acceleration. 2. It states that the practical limit for exhaust velocity is about 2.5 times ten to the third meters per second for conventional, non-nuclear hot-gas propulsion systems. 3. That is far below the far higher exhaust velocities mentioned later for proposed ion-propulsion engines. 4. 25 meters per second is far too slow to be a rocket exhaust velocity at all, given the accelerations rockets actually achieve. _Source: OpenStax College Physics (CC BY 4.0), Ch 8 "Linear Momentum and Collisions", section 8.7 Introduction to Rocket Propulsion_