I don't think any embedded systems engineers are programming in Rust for nuclear reactors or subs, and I don't think they are considering it either. No amount of safety constraints in Rust make up for the fact that the Rust team is sometimes willing to forgo backwards compatibility to keep the language clean. Not to mention those are usually legacy codebases from before Rust even existed, and no one is convincing the DoD or the DoE to "rewrite in Rust".