OK. But how exactly would the comm system function? Use OrbiterSound 3.5?
Would be perfect, but I consider OrbiterSound 3.5 currently an extension feature - we lack the game data (Sound files) to make use of it.
I would use the annotation approach. We can either use annotations for displaying the last communication and possible replies, or try drawing them directly on the Orbiter screen. Both would be possible, one allows more freedom in design and capabilities, the other would be more compatible with future Orbiter developments.
(Braindump: )
So, lets say, we display the last three lines of communication in the top-left corner. When the player presses TAB, the whole screen area gets used for displaying the replies. We should offer a set of quick replies to the last request from mission control and a number of categories for other communication.
For example, when the roll program takes place, pressing TAB could show "COPY ROLL" as possible quick answer. TAB and Enter could just be a quick "COPY" or "YES" in general. TAB and "N" a quick "NEGATIVE".
Pressing TAB again just aborts the communication - you say nothing at all.
TAB + Escape could get used for getting to the menu for reporting failures, aborts or problems.
This should be possible, like in most better military flight simulator games.
So, when the player enters the game at T-10, at roughly T-9 the communication "Atlantis, go for launch" would get sent from the MCC/LCC simulation (or from improvisatory from the GLS). The keyboard sequence TAB + ENTER would result in the player confirming "COPY, GO FOR LAUNCH".
This would be the moment you start the event timer.