The NASA Spaceflight article China conducts first Sea Launch mission with Long March 11 launch of seven satellites links to the YouTube video China’s first sea launch: Long March-11 launches from a ship at sea.
The article says:
The Long March-11 (Chang Zheng-11) is a small solid-fueled quick-reaction launch vehicle developed by the China Academy of Launch Vehicle Technology (CALT) with the goal to provide an easy to operate quick-reaction launch vehicle, that can remain in storage for long period and to provide a reliable launch on short notice.
LM-11 is a four stage solid-fueled launch vehicle equipped with a reaction control system on the fourth stage. The vehicle has a length of 20.8 meters, 2.0 meters in diameter and a liftoff mass of 58,000 kg. At launch it develops 120.000 kg/f, launching a 350 kg cargo into a 700 km SSO. The CZ-11 can use two types of fairing with 1.6 meters or 2.0 meters.
Question: The first half-dozen seconds launch looks a little unusual to me. Once it clears the tower the rocket appears to hesitate slightly, then a sudden bright burst of exhaust happens and at the same time it looks like it starts accelerating much more quickly.
Am I imagining things, or does the Long March-11 increase its thrust after clearing the launch tower?