If you're writing an application that could kill someone if it crashes, you'd better not be relying on the type system to catch those crashes for you, since it will only catch the most obvious ones.

For any life-critical system you want first and foremost to have a battery of end-to-end tests that run the software on the target hardware under various operating conditions. No amount of software-only testing/formal methods will give you this part.

Then, you want to have a formal specification of your program that can be run through a model checker - this would be the industry standard, though, if you have a team of PhDs at your disposal, you could also try to go with full formal verification a la Coq.

Finally, you want unit testing, integration testing, and possibly a type system to help day-to-day development. But do note, none of these should be critical for assuring the system works as indended - if typos in your code aren't caught by your end-to-end tests, what hope is there that they will catch complex dynamic behaviors?