The activity aboard the Abraham Kepler becomes frantic in an instant. Many troopers were relaxing, sorting gear, and settling into their new accommodations. But in the 30 minutes before launch, everything needs to be packed away, doors sealed, and all personnel to designated launch locations where they can be secured to prevent injuries during launch.
The process isn't as dramatic when leaving a space station, since there isn't the same gravity change, just the transition to faster than light travel. Ships the size of the Abraham Kepler also rarely land on planets and aren't really designed for it. Sure, they can survive it easily enough, but it is a huge amount of stress on the structure, even with Kepler's advanced anti-gravity technology.
On the surface, the parties are still in full swing, welcoming the veterans home with no idea that the enormous bulk of the Abraham Kepler is about to take off until the sirens start sounding to clear the area.