Launching Things - Timing

Do space ships launch on a schedule?

In most movies the heroes hop in their spaceship, cruise on up to their space station and that’s it. If you’ve ever watched a SpaceX launch though you’ve noticed they have a countdown. That’s not just to make it more dramatic. That’s because, whatever they're trying to reach is zipping around the planet at tremendous speeds. If SpaceX launches at the wrong time, they'll end up over Australia while the International Space Station is cruising over Europe. IIn which case, Houston, we have a problem.

In this specific case if both ships are following the same orbital path, but they're not at the same place at the same time. This is called having an orbit that is out of phase. The way to correct this is by either dropping to a lower orbit, where you move faster and catching up to the target. Or, by going to a higher orbit, ie moving slower, and letting it catch up to you. Both waste valuable fuel, which is why timing with space matters… a lot.