Not a spacecraft. Every mission control room should have a big red stop button called the Ebeling button. Anyone at any time can hit that button with no repercussions.
In a way, there is. The Challenger disaster drastically changed how information is propagated up and down during a launch, including how small an issue can be before a launch is scrubbed. I guarantee you there is no launch where Challenger doesn't run through the mind of every person sitting over the launch in Houston.