Hi there. I've been observing videos of shuttle launches in the early 1980s, post-Challenger, and post-Columbia. I've noticed that earlier shuttle missions broke the speed of sound slightly later than the final shuttle missions, and also separated from the solid rocket boosters at lower speeds than the earlier shuttle missions. I know for a fact that the solid rocket boosters gained weight after the Challenger disaster due to the addition of a third o-ring, but I don't know how a much a difference that extra weight made. I also know the shuttle received numerous upgrades over the years, example, a glass cockpit over a traditional one, etc. I observed these changes by timing the clocks on the videos...obviously that is not the best way to do it, but I was hoping somebody on here could give me something that would tell me if my eyes are deceiving me or not. Thanks.