I just played through Half-Life for the first time. I launched some rocket for no apparent reason (never really explained) then realized I had to backtrack and go down a ladder in the previous courtyard. So my question is, couldn't I have just gone down that ladder without launching the rocket? And what was the point of the rocket, besides having those blue exploding things that killed me over and over?
The rocket's mission is to deliver a satellite that will close the portal to Xen. This happens all thanks to your launch.
You can't continue the game without launching it. The next part of the map is locked untill you launch and then backtrack.