Bringing Iron Man to life: Exoskeletons, armour and jet packs
Power without the muscle of Banner and Captain America
Radiation that gives you super-strength instead of disfiguring or killing you, spider bites that empower you to fight crime instead of threatening your life with a potentially fatal allergic reaction: when it comes to superheroes we need to suspend a decent amount of disbelief.
But what about Marvel's The Avengers, the United States' largest grossing film of the year , which was spun up on many a home DVD player this Christmas? Just how much does science fact surrender to science fiction when it comes to the team of Iron Man, the Hulk, Captain America, Thor and Black Widow? Would it be possible to utilise real-life, workable technology to transform yourself into one of these characters?
It’s a six-person team, but there are only four actual superheroes in The Avengers.
We can discount Thor from the outset. No matter how hard we study, none of us are going to be born in another dimension as super-powered Norse gods.
What about The Hulk? David /Bruce  Banner was the victim of an experiment gone wrong . Banner was caught by a blast of gamma radiation which somehow translated into being able to transform into a green muscular monster while under periods of extreme stress.
Gamma rays are the most energetic form of light and are produced by the hottest regions of the universe, generated by exploding stars. On Earth they can kill living cells and are used in medicine to zap cancerous growths. They would not, therefore, turn you into a green muscular monster and back again.
With Captain America all you’d need is some exotic steroids and limitless time in the gym. Oh, and you’d need a shield that was as effective in attack as it was in defence – capable of absorbing all impacts up to and including the hammer of a Norse god. But Captain America’s shield in the Marvel Universe is made of vibranium, a metal that exists only in the pages of the comic books, so that rules out Captain A.
Of all the heroes, it seems that Iron Man is most based in reality. We already have exoskeletons, armour plating, and even propulsion systems such as jet packs.
The US Army has the Human Universal Load Carrier , developed by Lockheed Martin. It’s a hydraulic unit worn by a soldier and allows them to carry loads of up to 200lb (91kg), with the load transferred to the ground via the titanium exoskeleton’s shoes. There’s also the XOS  originally developed by Sarcos, the Salt Lake City firm that has since been bought by US arms mammoth Raytheon. The firm says it is now is lighter, faster, stronger and more flexible than before - and uses 50 per cent less power.
But the kit that is currently available in 2013 is nothing like you’d see Marvel's billionaire engineer Tony Stark wearing: there’s no armour plating, flexibility isn’t exactly liquid and then there’s power - HULC  runs on li-ion batteries that run flat after a few hours' use. Better take some spares, soldier.
Next, protection. The standard issue for troops, SWAT teams and general law enforcement today is Kevlar, chemically treated nylon specially woven into special patterns to make it more resistant to penetration. The tight weave makes for a cosy jacket but Kevlar is unlikely to withstand the kinds of aerodynamic pressures Stark puts his flying suit through and bullets certainly wouldn’t fly off it – it's more likely they’d just be embedded.
Then there is the armour option.
Stark's form-fitting armoured suit looks to be no more than 3mm thick, but with a density similar to iron (8g per cm3), James Kakalios  estimates it would produce 26,200cm2 of coverage with a mass of around 67kg - and if you add in the weaponry and onboard computing, you'd have quite a hefty costume, something in the region of 76kg. Kakalios is a professor in the school of Physics and Astronomy at the University of Minnesota and a comic book book fan, and wrote Everything I needed To Know About Physics I Learned From Reading Comic Books and The Physics Of Superheroes.
Arc reactor or hydrogen peroxide?
Kakalios estimates that Stark himself tips the scales at around 13 stone (81kg), which means that "his boot-thrusters would need to supply a constant downward force of over 330lb (equal to a mass of 150kg)" just for a fully suited-up Iron Man to do that enchanting wobbly hover thing he does. Duelling with supersonic fighter planes would require rather more than that.
“The only reason I didn’t give this movie a superhero physics A-grade was that... the amount of energy you would have to supply to continuously provide a downward thrust in order to maintain an upward force to counterbalance gravity is enormous,” Kakalios says.
So what about engines and power? In the film, Stark’s Arc Reactor is the engine's - and the weapons' - power source. Other engine options exist, but are limited. We have jet packs that work today but you don’t get to travel very far. One of today’s jet pack makers is Jet Pack International, which builds a hydrogen-peroxide-fuelled device capable of speeds of up to 80mph (128kmph). Problem is, it has a flight time of just 20 to 30 seconds and you'll only cover about a quarter of a mile (402m).
Next, there’s the control system. In the film, if Stark wants to fire his repulsor rays or transfer more power to the boot-jet thrusters, you never see him press a button or even give a voice commands. In the comics it’s explained away by saying that he has a cybernetic helmet that picks up his brainwaves and sends the signals to the suit – amazingly enough, this part is something that can be replicated in reality.
A number of scientists are working on cybernetic helmets.
One is Bin He  of the Department of Biomedical Engineering at the University of Minnesota. He has built a helmet that, like Iron Man’s, enables the wearer to control a computer just by thinking. It works on the principle that the electrical currents generated the brain create electric and magnetic fields, which can be detected by external devices.
“It’s a device that detects the very minute electromagnetic waves that are generated when you think. It amplifies them, interprets them, and can send signals to a computer so that you could move a mouse cursor on a computer screen by just thinking,” says Kakalios.
The basic idea of electroencephalogram (EEG) has been around since 1924, but recent developments in signal processing and analysis have enabled scientists to extract much more detailed information about the personal computer we’re all carrying in our heads.
“The first goal of this research is to treat paralysis or to develop improved next-generation prosthetic devices, but if you asked me as a kid in the '60s which aspect of Iron Man would be the closest to reality in the 21th century I would have said the jet boots, or maybe the repulsor rays. I don’t think I would have said a mind-reading helmet,” Kakalios says.
The device requires a good deal of "training", in the same way that we have to teach voice recognition software how to handle our distinctive intonation. Nevertheless it points the way to a hands-free alternative to the mouse and keyboard. Perhaps one day we’ll all be thinking emails directly to one another - hopefully with hilarious results.
Time for the X1?
NASA, the Florida Institute for Human and Machine Cognition (IHMC) and engineers from Oceaneering Space Systems in Houston are collaborating on a robotic exoskeleton called X1.
The 57lb (26kg) device is wearable robot that can either aid or inhibit movement in leg joints. In the inhibit mode, the robotic device would be used as an in-space exercise machine to supply resistance against leg movement. The same technology could be used in reverse on the ground, potentially putting victims of paralysis back on their feet.
There is a huge overlap between the science community and the science fiction, not just because fans of one work in the other. Robert H Goddard, the man who built the first liquid-fuelled rocket, began his love affair with space travel after reading H G Wells’ War of the Worlds.
And while they may not be able to turn us green, it’ll be interesting to see how much further the world’s scientists can go in replicating super-hero fiction using scienctific fact. ®