I have a question about a movie, its sifi, and its somewhat of an oldie.?

I guess it was a late 60's early 70's movie that was about a planet that was about to hit earth, there was this professor that knew this was happening and had built a space rocket to blast of this mountain side, the rocket ship looked like a missile but it was almost like a Noahs ark, but they where to take off as the the planet was destroing the earth, to land on the larger planet to stay there, for the human race to live on. I must have seen this movie atleast 5 or 6 times when I was younger , just can not remember the name of the movie. All I can really remember is the way the ship took off, it was like a train track that went up this side of a mountain then up into space, and I do remember the professor was in a wheelchair. Please help