I'm an English teacher with a modest science background teaching Science Through Science Fiction this fall, and I need some help with the physics in Andy Weir's Project Hail Mary. Here's one question I have. (Light spoilers for the book.)
The ship is going to Tau Ceti (11.9 light years from Earth). Astrophage (their propulsion system) can achieve avelocity of 0.92c. Weir tells us the time that will pass from Earth's frame of reference during the ship's journey is about 13 years.
I don't know the equations, but my intuition says that would make sense for cruising at 0.92c the whole way, but does it account for acceleration and deceleration? The ship would have to accelerate and decelerate with low enough $g$'s not to kill the human crew, which I believe is at least less than 5 $g$'s (borrowing from Kim Stanley Robinson's Aurora). It seems to me this would significantly extend the travel time. But I haven't seen any science critique call this out, so maybe I'm just that hazy on how the math actually works out.
Does Weir's stated time frame make sense or is it not fully accounting for acceleration?
Edit: Catiffiny reminds me that the book states acceleration is 1.5 g. I'm not sure it states this is constant for the whole trip (including when the crew is asleep), but it does at least imply constancy by not mentioning changes anywhere else.
