Watching the launch of the Shenzhou-11 mission on a Long March 2F, I noticed a number of items falling off the exterior of the rocket. I'm used to seeing chunks of ice sheet coming off of cryogenic launchers, but Long March uses non-cryogenic hypergolic fuels, and the pieces were squared-off, clearly manufactured items. There were quite a few of them - at least 10 coming off the launcher in the first 20 seconds of flight. Here are a few screenshots showing the debris:
Those falling particles seem to be parts of a protective sheet that shields the opening around the interstage lattice between first and second stages. Only the Long Marches launched from Taiyuan and Jiuquan during colder times of the year have such cover.
The following are a few examples to illustrate the presence and absence of the sheet in different times of the year.
TanSat (Long March 2D, TSLC, August 2016)
SuperView (Long March 2D, TSLC, December 2016)
Tiangong-2 (Long March 2F, JSLC, September 2016)
Shenzhou-11 (Long March 2F, JSLC, October 2016)
- News reports suggest that those are insulation sheets that kept the rocket warm against cold winter.