Flying around with your own personal jet engine, strapped to your back, has been one of the hallmarks of futurism for decades. Which sucks, because futuristic stuff is supposed to eventually happen. So why the hell aren't we all flying to work via rocket power? Because you're about as aerodynamic as a potato, my friend. Here are five reasons the jet pack just hasn't happened yet, despite announcements that "a practical jetpack" will be on the market soon.
1. Humans are not designed to fly. Until you gene-mod a nice aerofoil onto your back, you are never going to soar like a bird. Nothing about the way you are shaped creates lift. That means the jet pack has to provide all the lift via thrust.
2. Thrust burns a lot of fuel. All that lifting power comes at a price, and we're not talking $4 per gallon (it's actually a lot more expensive than that). You can only fly as far as your fuel will take you, which today is about a 30 second flight. No problem, just carry more fuel, right? To get any kind of practical flight time, you need a massive fuel tank on your back. The extra fuel weight requires more thrust, which burns more fuel. It's a vicious cycle made worse by the fact that most "jet packs" are actually rocket packs. They need to carry their own chemical oxidizer along with the fuel.
3. Danger! Jet and rocket packs are notoriously unstable flight platforms. They're really hard to fly. Then there's the altitude problem. With a 30-second flight, you're not going to get high enough for a parachute or any other safety system to do any good. If the engine cuts out or you lose control, you're probably going to create a small crater.
4. Rockets and jets are really, really loud. You're not going to sneak up on anyone with your jet pack, so military uses are mostly out. In fact, you can forget using one anywhere near other people.
5. Inefficiency. There's really no point in flying one person around. Pretty much any practical use you can come up with for a jet pack can be done with a lower tech, cheaper and more efficient solution. This is the main reason the other problems haven't been overcome by awesome engineers yet — beyond looking cool and flying around, we don't really need jet packs.
That said, there are companies still working on this stuff. Many of them seem to be moving in the direction of jet propulsion instead of the old rocket belt technology, which could offer longer flight times. I think Swiss engineer Yves Rossy (pictured) has the right idea. He combined jet engines with a lightweight wing and can use it to do aerobatic maneuvers. You can read more about the history and development of jet packs over at HowStuffWorks.com. Image by: Getty Images.