Surely by now you’ve seen the Avengers, think of the SHIELD helicarrier? What is your opinion on a nuclear fuelled flying fortress? Feasible, possible, absurdly extravagant?
Well, there’s a few points to be made here, first and foremost of which is that the SHIELD helicarrier is not exactly an original concept. Gigantic flying aircraft carriers are a staple of science fiction and can be seen in everything ranging from Doctor Who to Sky Captain to Captain Scarlet. They’re a progression from the zeppelins and other airships that were common in the first half of the twentieth century, in the sense that I imagine people are thinking “Well, if we could do that with a glorified balloon then just think what we could do with jet engines!” The idea of a flying airbase isn’t a bad one in and of itself, and if you want proof I believe one of the things that was on the drawing board as part of the US military’s ever-expanding drone program was essentially a drone surveillance blimp that could stay aloft for weeks at a time and also serve as a refuelling station for other lightweight drone aircraft1.
However, the “blimp” part is important. As long as you’re dealing with something lightweight, a blimp/zeppelin/balloon can float around for far longer than something which is constantly burning fuel and energy to stay airborne. The SHIELD helicarrier on the other hand would be a variant of VTOL aircraft, just like a helicopter or a Harrier jump jet. With that in mind, let’s have a little look at what it would take to keep the SHIELD helicarrier aloft.
It’s been a little while since I saw the film so my memory could be a little bit rusty, but the helicarrier looked like it was just a bit bigger than a large sea-going aircraft carrier so I’m going to use the Nimitz-class supercarrier as my point of reference. The Nimitz has a displacement of 100,000 tons. This is the amount of mass our VTOL engines are going to have to lift. The SHIELD helicarrier has what look like turbofan jet engines strapped to the side, but I’m prepared to accept the possibility that they may be a weird sort of rotary wing instead so I’ll consider both possibilities.
Jet engine — The problem with a jet engine is that you have to compress and heat your air intake very very quickly through the combustion of aviation fuel so that it exits the nozzle at the rear of the engine in the form of a high velocity jet that drives the aircraft. For regular jet engines there is no way of getting around this fuel requirement; you have to heat the air intake, which means you have to burn some kind of fuel substance. This is kind of handy for me, because it means I don’t have to crank through the calculations to see whether or not jet engines could lift a mass of 100,000; they’re notoriously inefficient for VTOL purposes (which is why you never see them on anything bigger than a jet fighter, as well as being the reason the US Marines have invested quite heavily in their tiltrotor Osprey to provide the same VTOL capability to a larger aircraft) and so it’d be pretty much impossible for them to do it anyway, but even if they could the helicarrier couldn’t carry anywhere near enough fuel to stay aloft for more than a few minutes at a time. And there’s no sidestepping that with nuclear power or Arc reactors or whatever.
Rotary wing – Slightly more plausible as they merely need some sort of power source to make the rotor blades spin. While they don’t need liquid fuel I’d question the ability of electrical motors to provide the sort of power a rotary wing would need to generate lift, but this thing has Tony Stark aboard so I’ll just assume he’s fixed that little problem. It’s just a question of whether or not rotary wings could lift a mass of 100,000 tons. For reference, the most powerful transport helicopter in service today has a carrying capacity of 28 tons and a maximum takeoff weight of 56 tons. It would take 3,500 of them to lift a Nimitz carrier. Even assuming that the engines fixed to the helicarrier are far more powerful and that the helicarrier might be made out of super-lightweight alloy or something, it’s not something that I would regard as being remotely plausible.
So the concept of the helicarrier as seen in the Avengers is slightly ridiculous. That’s okay, though; that film had a Norse god and a giant green man punching flying metal fish right in the face so it’s not like it broke my suspension of disbelief or anything. What did bug me was the initial reveal where the carrier transitions from sailing to flying and the engines rise out of the ocean where they’ve been submerged for god knows how long, which would be a hilariously bad idea because salt water is super corrosive and would fuck those engines right up. But hey, maybe Tony Stark made them out of magic metal too. It’s a comic book film, which makes it one of the few instances where I can turn my brain off and accept comic book logic. Just don’t expect to see the SHIELD helicarrier flying around anytime in the next, oh, forever, because it’s just not going to happen.
1. This is mentioned in P.W. Singer’s excellent Wired for War, a somewhat disturbing overview of the history of robotic warfare so far and where it’s likely to be going in the future.