“Get your mechanized mitts in the air!”

— Spider-Man to Rhino in The Amazing Spider-Man 2 (2014 Sony Pictures)

Created by Stan Lee and Steve Ditko and appearing initially in a story by Lee with art by Jack Kirby in Amazing Fantasy #15 in August of 1962, Spider-Man has been a hugely popular and ever quirky superhero. You can’t help but love Spider-Man’s accessible character played to great effect by Andrew Garfield in the recent Marvel Studios films The Amazing Spider-Man (2012) and The Amazing Spider-Man 2 (2014).

(Thwip! Thwip! Warning: this post may contain some small spoilers for The Amazing Spider-Man 2... please read on at our own risk…)

But this post isn’t so much about ol’ Web Head as much as it is about Spider-Man’s fantastic gallery of super-villainous bad guys. Or, I should say, one of Spidey’s more obscure enemies. I don’t mean Electro, Sandman, Vulture, Mysterio, Hobgoblin or Doctor Octopus (my favorite in this list). It’s not about any one of these “Sinister Six”. Instead I want to look into Rhino, who plays an interesting but admittedly peripheral role in The Amazing Spider-Man 2.

Rhino (aka Aleksei Sytsevich) debuted in 1966 in the pages of The Amazing Spider-Man #41 and is portrayed in The Amazing Spider-Man 2 by the excellent Paul Giamatti. Even though Rhino may not be the smartest of villains—Mike Conroy in his book “500 Comic Book Villains” used the adjective “dimmest”—there are some really compelling things about him.

The main one for me is Rhino’s exoskeleton. I’m hugely captivated by exoskeletons and their applications with real biological bodies. I wrote about exoskeletons in some of my other guest posts here at Scientific American (“Assembling An Avenger”, “Iron Man Extreme Firmware Update 3.0”, and “The Exoskeletons Are Here!”). The way Rhino is portrayed in The Amazing Spider-Man 2 galloping through New York City in broad daylight really does put a spotlight on exoskeletons.

Despite that the surface view of Rhino’s powered up and armored exoskeleton—like that of Iron Man—grabs all the attention, I want to get beneath the surface here and talk a bit about the power problem. How could you provide enough energy to power up the robotic exoskeleton of a raging Rhino?

When I wrote Inventing Iron Man I spoke to my colleague Jim Kakalios, the friendly neighborhood physics professor and author of The Physics of Superheroes about this. Jim was quick to explain that:

“Energy storage in batteries has dramatically lagged behind information storage. If batteries had followed Moore's Law, which describes the increase in density of transistors on integrated circuits, with a doubling in capacity every two years, then a battery that would discharge in one hour in 1970 would last for over a century today. Ultimately, if we don't want to wear licensed nuclear power packs on our backs, we are limited to chemical processes to run our suit of high tech armor, and in that case we must either sacrifice weight or lifetime.”

I’ve tried to represent this issue in the figure to the left where the red line for CPU power can be seen as increasing at a rate far beyond that of battery energy density, drawn in blue (data from Starner and Pardiso 2004).

Fully developed armored exoskeletons like Rhino’s need a lot of power. To give you an example of how much energy would actually be needed to power something simple like stepping movement in a robotic, exoskeletal body consider the work of Masato Hirose and Kenichi Ogawa at Honda Research and Development and Engineering Companies. In 2007 they estimated that the Honda P2 humanoid robot (two prototypes before the well-known ASIMO robot) consumed nearly 3,000 watts during walking, giving it an operational time of only 15 minutes. This is equivalent to about 2,600 kCal of energy, the daily energy expenditure for an average North American male!

So while we wait for cold fusion (sorry, “low energy nuclear reactions”) and the invention of Tony Stark’s arc reactor, what kind of additional tweaks should be built into the exoskeleton of any self-respecting and science-grounded super villain?

The incremental answer is energy harvesting! When Rhino is rampaging around New York City making mayhem, his arms and legs are doing both positive and negative mechanical work. Basically his positive work powers his propulsive stepping and the negative work is occurring in the recovery from each stepping motion. This is an important part of the neuromechanics of moving, but it kind of seems like wasted energy.

But what if there was some way to harvest this wasted energy more directly for other purposes? Over many years, researchers have been thinking about this very question using power from people. This includes ideas around harvesting heat energy, energy from breathing, blood pressure, inertia from moving, arm motion, and energy at heel strike while walking.

A team headed by Dr. Max Donelan at Simon Fraser University developed a device—one of TIME Magazine’s Top 50 best inventions of 2008—that’s strapped around the knee. This “bionic power” energy harvester is basically a frame and generator system mounted on a modified orthopedic knee brace (see image at right). In application, a user would wear one of the 850-gram devices on each leg. Using a clutch and generator system, the negative work during walking is captured and stored. Current devices can generate a maximum of 25 watts of electricity. At a comfortable walking speed 12 watts can be generated, which over of one hour would charge four cell phones.

Donelan agreed that the energy harvesting capacity of his device is “still far less than Rhino would need to take on Spider-Man.” But, he added, “Rhino could use it to charge his phone so he could call in his villain posse to kick some Spidey-butt.”

In the real world, though, this is enough electrical energy to power different mobile devices or an artificial limb. Without question Rhino’s exoskeleton, regardless of the source of major power, would need to make use of this very efficient kind of power storage and reuse.

Using the alliterative naming convention of the great Stan Lee—who gave us both Peter Parker and J. Jonah Jameson—let’s end by saying every little bit of current counts and we can have no watts wasted.