Thinking about the difference between the Iron Lung/SM-13 and the Hail Mary.
(Disclaimer: I haven't been able to read the book for PHM yet, so this is mainly based on movie canon, with a little bit of book stuff via fandom osmosis.)
The SM-13 is excruciatingly, brutally pragmatic, to the point it harms its own functionality. It claims to not be a 1-way trip but nothing in the design suggests that. Bare metal, rusted out, one single porthole that's dangerous at most depths and useless at all of them. The controls are unintuitive and confusing. There's no CO2 scrubbing or anything to make the air reusable. Its only means of sensing the environment or gathering data blasts radiation into the sub every time it's used. Its only means of gathering data is a primitive "claw" that requires slamming into the object of interest at full speed, endangering the craft (and its pilot) in the process. Said means also has no means of confirming if the collection is successful. There's no reliable communication system for most of a descent's duration.
Meanwhile the Hail Mary, an open suicide mission with no obfuscation or deception as to its nature, takes exhaustive care to try and ensure the crew are as OK as possible. The interior was designed with bright, clean lights with variable settings and for a spacecraft, it's downright roomy. The crew were allowed to bring treasured mementos from their loved ones. The engineers included a room full of screens that could recreate the Earth's natural beauty, a beauty the crew knew they'd never see again. A comprehensive host of Earth art and entertainment such as books, movies, music, and games were all pirated (not even legally acquired, pirated, something else Stratt was consciously adding to her list of Things That Would Catch Up to Her) expressly for the crew. State-of-the-art medical equipment and technology was installed onboard with the knowledge it would never be retrievable. Everything on the Hail Mary was painstakingly designed to account for every contingency they could possibly think of with the time and knowledge they had. Flavorful food, more than bare nutrients, was sent with them. People from around the world made personalized tribute items for the crew to bring along, to help them remember how much they meant to the rest of humanity, how their sacrifice - even if the mission failed - would never be forgotten.
The SM-13 cuts so many corners it actively shoots itself in the foot. The Hail Mary is designed with so much care in mind for her inhabitants that it helps ensure the mission's success. In the eyes of the COI, things like treasured mementos or fancy screens wouldn't contribute to the mission...except that they do, because they help the crew stay afloat emotionally, spiritually, psychologically, which then allows them to better stay on course. The Iron Lung is so utterly miserable to be in and lacking in basic functionality that not only Simon's mission but any mission using the SM-13 was all but doomed from the start (there's barely any real mission equipment onboard - just on its own it's enough to question the overseers' expectations).
Grungy, gutted, hateful; afraid, painstaking, hoping. Both designs reveal much about their worlds. Both were born from a place of desperation, but one with far more resources at her creators' disposal. One was crafted from survivors already at each others' throats, the other "merely" eyeing it on the horizon. There's something to be said for the criticality of that difference in circumstance, how it could have affected the vessels' design, and to be sure, the level of conscientiousness in the Hail Mary's design is known to be at least somewhat about cold, calculated risk management: stressed-out humans are more likely to fail or descend into conflict. Adding a million redundancies and planning around as many angles as possible is absolutely a practical decision. Despite this, it's hard to shake the sense that one world really did care about those it was sacrificing. Sometimes caring is a privilege, but even the most optimistic timelines for the Hail Mary's mission still resulted in staggering death tolls and permanent, widescale ecological damage. Though the entire planet's resources were at Eva Stratt's disposal, time remained at a premium.
There's a powerful undercurrent of humanity all throughout Project Hail Mary; the things we live for, the things we die for, grief, hope, sacrifice, love. Iron Lung is fundamentally about a world constantly trying to prove it's too far gone, and how people respond when death has placed its signature on every inch of the universe. Project Hail Mary's themes are right in the name; it's about people that refuse to give up or abandon their hope, who choose to see - to forge in fire - a chance, even in ever-narrowing odds. It's a theme that's woven into the entire craft's design. Two apocalyptic events, two one-way trips, one world whose people decided never to forego their humanity.
A radiation camera and a handmade quilt.
