I would have read this novel in the mid to late 1990s to the early 2000s. I believe it would have been before 2003 and the Space Shuttle Columbia disaster.
The story revolves around a space shuttle (I believe it was the Columbia) being heavily modified and used as a deep space ship to populate/travel to another planet.
I believe the story starts off which a shuttle accident similar to the Columbia disaster where a space shuttle breaks up in re-entry. The female protagonist has to evacuate the shuttle by using an escape device which was effectively a pole out of the shuttle that pushed her body past the rear engines and tail fins.
I believe a natural disaster of some kind is going to happen that will destroy life on earth. As such another shuttle is modified for a deep space journey.
The female protagonist is joined by a white haired air force Colonel who ultimately goes crazy on the journey and she has to knock him out/kill him.
I do not remember if they get to another planet or not.
I believe the escape system used in the opening incident was real and the book was heavily researched and tried to be as scientifically accurate as it could be