How were humans expecting to do science?
Here's something I don't quite get. So humans went to all this effort to build a spaceship with lots of science gear and send it to Tau Ceti because it's the one solar system that seems to have been unaffected. What did they think they were going to do once they got there? They don't seem to have had any sample collection equipment besides the astrophage collector on the outside of the Hail Mary. Had Rocky not been there, even if the mission had gone to plan, it would have been a failure.
Seems like the way this would have gone is that after the humans figure what astrophage is, how it works, and decide that they need to go to Tau Ceti, they would have gotten a bunch of astrophysicists and biologists together and had them figure out what sorts of science equipment they needed to bring. After all, you can't get there, decide you don't have the right equipment and do a do over. So, the scientists probably would have sat down and come up with a bunch of hypotheses about why Tau Ceti was unaffected. Perhaps there were no planets with CO2 in their atmosphere (unlikely, but you never know). Perhaps the planets with CO2 had something toxic to astrophage. Seems like biologists would have likely recognized that astrophage is an invasive species and recognized that invasive species don't have issues in the place where they are native because there's something keeping the population in check. So, maybe there's something that eats astrophage there. Etc, etc.
With that in mind, why wouldn't the humans have also packed equipment for sampling and data gathering in the places they know astrophage visits: the surface of a star, space, and the atmosphere of a planet? Instead, they just packed equipment for sampling in space. Seems like they would have packed a few more specialized beetles equipped for sampling in those places too.