S replies, T expands on reply. T continues expansion on friction and gravity, B nods, J plays with bottle. J responds, T expands on scenario while J traces trajectory with bottle. T asks about the effect of bottle shape on its trajectory, B explains. T asks about texture, pointing at bottle, asks about the possibilities for rocket finishes.
T then asks about engine effects.
The problem is too big, no response from Ss. T answers own question. Ss speculate on which will go farther and why. Discussion of variation across launches. Shift into question of fins.