NASA will soon require a retired astronaut to serve as mission commander on all private flights to the International Space Station, according to an agency notice posted today. The policy — which has yet to be finalized — is intended to both increase passenger safety and reduce any strain on existing ISS operations. The former astronaut would provide “experienced guidance for the private astronauts during pre-flight preparation through mission execution." A number of changes also impact space tourists themselves, including new medical standards for private astronauts, more lead time for private research projects, changes to the policy for return cargo and additional time for private astronauts to adjust to microgravity.According to the notice, the new changes were a result of “lessons learned” on last April’s Axiom Space flight, where passengers paid $55 million each to fly on the first private astronaut mission to the ISS. The hectic, two-week trip — where passengers