It's a crap-shoot traveling to another star. Most people survive the journey but there never has been and never will be a trip where everybody does.
Here's the deal. The space between the stars is ruled by what you might call elder gods. Lovecraft was pretty close to the truth. They let us pass through their domain if we are willing to let them have some sacrifices. Human sacrifices. Those selected by the elders spend a millennium slowly being digested.
The government's solution is building huge prison ships that also carry a few passengers.