"It's not like that."

Yao and Ilyukhina's brains make it alive to Tau Ceti. They wake up one at a time so Mary can help process their waking efficiently for them. Since Yao and Ilyukhina knew what they were signing up for and were given training, their awakening was programmed to give them full memory and control after a few quick checkups from Mary. It's due to this that they both almost immediately become overloaded with overstimulation and stress, as there's simply no amount of training that can simulate the experience, and both set off the suicide command. I'm unsure if either did so intentionally, or if they just felt so deeply and thoroughly horrified at the thought of living as they were, and Mary recognized that as the command. Either way, Grace still wakes up alone.

Seeing as Grace was entirely resistant to going, he was given a memory blocker program and limited controls until he could prove in Mary's checks that he wouldn't jeopardize the mission. Without the human senses to correlate to memory, it comes back to him much more slowly, and he finds himself far more confused with his situation. Sure he can see and hear and- with one particular sensor to analyze gaseous chemicals- 'smell', but it doesn't always reach the same neural pathways that humans use for storing sensory memory.

He can control the many instruments of Mary, but Mary still acts as the autopilot and 'watchguard' of their ship (and keeps check on the brains but he doesn't know that for a while), so Grace doesn't have to sacrifice brainpower to keeping tabs on everything. Many robotic limbs and movement tracks take up a lot of the inside space, while a drone is attached to the outside that can maneuver freely, and docks in the airlock. Grace takes advantage of this, feeling a bit less mentally claustrophobic while flying around. There's also a small drone on the inside in case they ever needed to fix something out of reach of the wall. If Yao and Ilyukhina lived, they would all technically be sharing the same body, but Mary is programmed to allow only one mind in a device at a time, to prevent dual input.

Rocky would have such a weird time at first. They make the tunnel expecting company, but it's just the drone that they heard picking up the canister. No big deal, maybe this alien is just really cautious, that's fair. But as they figure things out together, Rocky gets a little impatient and asks, and feels disappointed that it's 'just' a 'robot' on the ship. I can't decide if eridians would have their own version of AI (actual AI.) or if Rocky has absolutely no idea and thinks they're just talking to some alien metal doodad. I'm thinking Grace has already come to the conclusion he must've been human at some point, but still isn't sure, so his insistence that this is just an extension of his biological self is kind of weak. Rocky still appreciates the drone promising to watch them sleep; it's slightly better than the decades of isolation they've had.

Since they both need far less break time than a human body would need, they break through the language barrier faster than canon. Grace also has slightly improved present memory, thanks to Mary keeping backups that he can instinctually access.

When Rocky finally gets impatient and rolls into the Mary, their disappointment turns a little bitter toward Grace. They've been walking through the ship and commenting, but their excitement turns quiet as Grace's voice keeps coming from the ship speakers. Where's that biological self, huh? Talking to a bunch of scrap metal all this time... At this point I think Grace regains a flash of how he was 'uploaded' and has a very chaotic emotional breakdown at the suggestions that memory gives him. Even Rocky gets a little worried despite them thinking Grace is a robot, and tries to talk Grace down, who in turn mentally shuts down. Rocky is left in a very quiet Hail Mary for a little while.