When the first trailer for Avengers: Endgame dropped, one of the things that stood out most was Robert Downey Jr.'s Tony Stark being lost in space after losing to Thanos on Titan. He's clearly broken, mentally and physically, trying to send a message back to Pepper Potts on Earth that he may not have much time left in the spaceship he's commandeered with Nebula.
However, a theory popping up on Reddit has offered a suggestion as to exactly how Tony is managing to survive months of being marooned off-planet, floating in the dark recesses of the cosmos. And it all has to do with his clever use of nanotechnology.
In the latest TV spot, the eagle-eyed theorist spotted a shot of Tony trying to repurpose a piece of technology with Nebula, no doubt so they can find their way back to whichever Avengers survived Thanos' Decimation. But it's not the technology in Tony's hands that's important -- it's the one under his shirt. As we can see, his nanoparticle housing is beneath the shirt, rather than above or outside it as we saw in Infinity War, or even in the first Endgame trailer.
It hints that, after he tries to send Pepper his message, Tony decides to fuse the housing to his chest, basically giving himself an arc reactor once more. This fusion would allow nanotech to be integrated into his body, turning him into a half-human/half-machine hybrid similar to Ray Fisher's Cyborg in Zack Snyder's Justice League, allowing him to survive without food or water. It's a clever twist by the Russos if this is indeed the case, with Tony resorting to a last-ditch effort to stay alive by creating what's effectively a hybrid of the Bleeding Edge and Extremis suits.
The Bleeding Edge armor first appeared in 2010's Invincible Iron Man #25 and stands out as the most intriguing armor Stark ever created. It was fluid, which allowed the suit to be stored inside of Tony’s bone marrow via nanoparticles, which meant he had his Iron Man armor with him at all times. All that was needed was a mental command and the suit would bleed out onto his body, similar to what we saw the housing doing in Infinity War. Only now, this adjustment makes the connection more physical than mental, as it's literally a part of Tony's body, acting like a battery and keeping him alive.
One key function the technology had in the books was its ability to create layers of artificial muscle over Stark's body, upon which additional structures were assembled. This is why the armor could self-repair and came off as almost invulnerable, as it basically studied Tony's body and was able to transform and heal itself.
With these constantly replicating nanomachines replacing anything that is lost or used up, so long as the power output from the arc reactor isn't interrupted or terminated, then Tony would have an immortal suit, so to speak. This means that, once the technology adapts to his body, as this theory claims, it's not just muscle tissue, but his actual metabolism and internal functions that could be preserved too.
The result would be similar to Iron Man 3's Extremis, but one that certainly would be more stable. Created by Maya Hansen and Aldrich "Mandarin" Killian, Extremis granted the human body healing abilities and other unique traits. These included regenerating severed limbs in a very short time span, various physical enhancements the exothermic ability to shoot fire.
The last ability aside, it's clear from the first two components that internal repair could be done to the body, which means that, if Tony's new retrofitting of his nanotech housing really is a hybrid of these two pieces of engineering, he may finally have found a way to become more iron than man. Iron Man upgrade in such a way and out for revenge is definitely not good news for the Mad Titan.
Avengers: Endgame will arrive on April 26. Directed by Joe and Anthony Russo, Marvel’s Avengers 4 stars Robert Downey Jr., Josh Brolin, Mark Ruffalo, Tom Hiddleston, Chris Evans, Chris Hemsworth, Jeremy Renner, Chris Pratt, Elizabeth Olsen, Chadwick Boseman, Sebastian Stan, Benedict Cumberbatch, Paul Bettany, Samuel L. Jackson, Cobie Smulders, Benedict Wong, Zoe Saldana, Karen Gillan, Vin Diesel, Dave Bautista, Pom Klementieff, Scarlett Johansson, Tom Holland and Anthony Mackie.