A high nitrogen atmosphere does not make you feel drunk. That's only deep sea divers.

Passing through the central chamber of a rotating spaceship does not just make gravity magically switch directions.

You won't get acute radiation burns from existing in interstellar space, especially in a shielded ship. Or even in an unshielded ship.

The presence of the ship's engine nearby does not act as an adequate radiation shield.

Titan would never be chosen as Earth's first colony location.

A person can easily tell the difference between a screen and a window if they can get close enough to touch it, particularly if there are 2 people in the room looking "outside" from 2 different angles

It's highly unlikely that a ship in a random part of the galaxy will be able to see the same pulsars as Earth

You also can't measure the distance to a pulsar just by listening to one frequency.

Time dilation is not time travel. Things are always traveling through time, and going forward is fine

e=mc^2 doesn't mean that as you get close to the speed of light, you feel yourself gaining mass. It most certainly doesn't increase your BMI.

It's relatively simple to check the location and the date, given appropriate instruments. This is not something that would be difficult for an astronaut.

For a 9-24 month mission, the chance of an astronaut dying due to cancer is the exact same whether you're 17 or 50. There is no excuse for a mission to require 17-year-olds b/c cancer (it's a YA novel)

There is zero chance that a civilization who built their first colony on Titan and failed within a couple days would be successful at building a colony ship to the other side of the galaxy.

There is also zero chance that such a civilization would be able to build a ship that could run for 30,000 years.

The author did not do the math on how much prepackaged food it takes to support 2 people for 15 years.

If cryo-stasis is impossible in your world, then packaging people in plastic like chicken breasts and reviving them from a "coma" is also not possible.

If your astronaut truly thought that a lollipop-shaped ship would somehow magically rotate around the end of its stick end, creating artificial gravity in the ball end, your astronaut doesn't understand physics.

A planet that goes between the two suns of a binary star system is a BAD PLACE to decide to settle.