Here's a clearinghouse for some of the things that have come out in chat.
- The ship does not have enough resources to maintain everyone awake at the same time
- Let's say 75 people, with 75 in cryosleep.
- We can 3D print most medical stuff.
- AR goggles are a thing, just like tablets and computers.
- Opening your brain is somehow to the ship network, CyberWeird.
- There was a revolution some generations back, or maybe it was a cryo accident. Either way, no Engineers. Just Maintenance.
- We have synthetic humans. Easy to pass visually or with non-augmented human senses. Impossible to pass medically.
- The engine busted, and it puts out constant thrust. Occasionally it shorts out on fuel, and we spend a day or week drifting until the hydrogen cells recharge.