Spaceflight

I've been wondering why there's such a big gap between Starliner's expected departure ("early September") and the launch of Crew-9 (no earlier than 2024-09-24).

My least bad guess is that NASA doesn't see much difference in the risk of having Butch & Suni return as (little more than) cargo inside Crew-8's Dragon capsule, and the risk of them returning in the actual standard/proper crew configuration in this Starliner capsule. In which case they might as well get Starliner back ASAP, while making no attempt to bring the Crew-9 date forward (which could have been doable given that the plan as of last month was to be ready by 2024-08-18).

Has anyone got a better guess?

I do know that a standard Starliner departure involves waiting for a suitable opportunity / time window. But there must be suitable opportunities much closer to the 24th, right? Why aren't they waiting for the last possible (or maybe penultimate) opportunity? In the unlikely event of Starliner failing to undock or whatever, it'd be no big deal to delay Crew-9 again, so I don't think that would be the reason.

I had been imagining a much greater level of dependency or 'coupling' between the two events. Perhaps with NASA looking at the Crew-9 launch weather forecasts before deciding whether to undock Starliner about 3 days earlier, or something. Or even (less seriously), the Crew-9 crew strapped into their Dragon, on the launchpad, and hearing on their comms system something like "Starliner has successfully exited the ISS's Keep Out Sphere, so NASA is 'go' for propellant load on Falcon 9".

I was hoping somebody would ask this question during the press conference, but they didn't.