Complex sentence: These condensation clouds can often be seen appearing round space-bound rockets as they accelerate through the atmosphere; for example, they were frequently seen during Space Shuttle launches around 25 to 33 seconds after launch when the vehicle was traveling at transonic speeds.
Split into simpler sentences: These condensation clouds can often be seen appearing round space-bound rockets as they accelerate through the atmosphere. For example, they were frequently seen during Space Shuttle launches, about 25 to 33 seconds after launch, when the vehicle was traveling at transonic speeds.