Quantum barrier
The quantum barrier was an obstacle in achieving slipstream velocity.

In 2374, the  attempted to break through the quantum barrier while at full impulse. Lieutenant Commander Tuvok had trouble controlling the field parameters and needed more  to the navigational deflector. After auxiliary power was rerouted to Deflector Control and the quantum warp field was made stable, Tuvok was able to focus the quantum field which allowed the ship to enter a slipstream tunnel. ()

See also 
 Warp barrier

Physics