Edit: We have an answer... It was "Earth Star Voyager" -- a two part pilot of which, it would seem, I only saw part one.

I need some help from y'all. I recall a TV movie about a spaceship launched with a crew made-up of primarily teenagers because of the duration of the round trip to the planet they were being sent to explore. Before the ship got very far they were attacked and had to construct a makeshift weapon and mount it in a hanger or cargo bay or airlock (something like that) to defend the ship. It cliff-hanged there and, as far as I know, never returned to the air. I think it might have been a Disney movie, or at least aired in the Sunday at 7pm slot Disney movies typically air. This ran circa late 1980s or early 1990s -- I think it was pre-1992 as I believe I was still living in Brighton Beach when it aired (and so it could have aired on cable).

Can anyone put a name to this faded memory of a sci-fi show?