Zero. Remember there is no need to make an accident survivable because an accident can't happen "Failure is not an option" and lots of other macho chest beatin

Zero. Remember there is no need to make an accident survivable because an accident can't happen "Failure is not an option" and lots of other macho chest beating. If the Titanic had been built by Nasa it would have had no lifeboats, a crew of 10,000 safety inspectors but would still have hit the iceberg.