Cut to the bottom of the Hudson River where some electrical “transmission lines” rest. Tony in his Iron Man supersuit has his palm-mounted repulsor rays configured such that they create a focused beam, capable of cutting through an iron pipe to reveal power cables within. Once the pipe casing is removed, he slides a circular device onto the cabling. The cuff automatically closes, screws itself tight, and expands to replace the section of casing. Dim white lights burn brighter as hospital-green rings glow brightly around the cable’s circumference. His task done, he underwater-flies away, flying up the southern tip of Manhattan to Stark Tower.
It’s quick scene that sets up the fact that they’re using Tony’s arc reactor technology to liberate Stark Tower from the electrical grid (incidentally implying that the Avengers will never locate a satellite headquarters anywhere in Florida. Sorry, Jeb.) So, since it’s a quick scene, we can just skip the details and interaction design issues, right?
Of course not. You know better from this blog.
In case you were planning on living out some elaborate cosplay fantasy to remake this scene, be aware that subsea cables don’t just sit like that inside of an air-filled pipe, waiting for a leak to short circuit the power grid. The conductive cabling is surrounded by thick plastic insulation. Even the notion of pipes underwater might have been a thing years ago, but modern subsea casings are steel cables embedded in the same insulation. But whatever, we don’t need that for the story.
The cuff interaction is awesome. All Tony has to do to is roughly slide it in position, and then the thing does the rest. The shape and actuators make it so he can place it roughly in the right place, and it does what it needs to do. That might have been overengineered for a single-use device, but whatever, he’s Tony Stark. He might have engineered it over breakfast, and he might already have made a handful for his other buidlings.
The cuff itself is less awesome. If you were a high-profile billionaire inventor superhero putting a device in a place that’s difficult to monitor and connected directly to the electrical systems of your headquarters would you let it glow? Sure, that makes it easy to find later, but that means it’s easy for any supervillain to find, too. Much better is to camouflage it in the original pipe and keep its location secret from malefactors. Bad Tony. No glow.
The welding looks problematic for a couple of reasons. Does the “arc” have a fixed focal length? If so, how does he know what that length is and when he’s straying from it? We can presume it auto-adjusts using some welding subroutine of his on-board artificial intelligence, JARVIS. Then it becomes an issue of aiming. Try this: tape a three-inch pencil perpendicularly to your palm, and then try and fill out a crossword puzzle. Not exactly precise.
But using a bit of apologetics, let’s presume that he’s not using a tool so much as positioning the tool that JARVIS uses. JARVIS can use cameras situated around the suit and perfect 3D modeling to continually adjust the focus and positioning of the repulsor beam to target wherever it is that Tony is looking. Perfectly reasonable given what we know about the technology in the Marvel Cinematic Universe, and moreover, the way it ought to work for its user. He uses the thing his body is expert in, i.e. looking, to guide an agent that takes care of all the details he’s not good at, i.e. controlling the repulsor beam to cut into the pipe at a precise depth. Now it’s not problematic. It’s awesome.