Li's Jetlev-Flyer uses twin water pumps to thrust the rider into the air. And the high-velocity water streams do, in fact, give the rider an altitude of up to 30 feet, and they can steer the device by pushing on the handlebars to properly angle the stream.

However, the use of the Jetlev-Flyer is extremely limited. Because an enormous mass of water is required to achieve the necessary level of thrust for any amount of time, the water cannot be carried on the jetpack itself. Instead, a small vessel is dragged behind the jetpack, pumping water into a long hose attached to the back of the pack. Thus, the Jetlev-Flyer only works near a body of water and is essentially a Jetski, albeit a rather epic one.

Li plans to put the Jetlev-Flyer on sale later this year. So, if you have about 130 grand to burn, you too can have your very own pseudo-jetpack.

[Popular Science]

I am no stranger to the jetpack dream. This may be a surprise to Montandon, since his book made frequent note of the dearth of women in the jetpack-sleuthing world, but that future he imagines — the one with new gadgets and better engines — will bring gender equality as well. Conversations with my half-female group of aerospace engineer friends at MIT often ended with one of us blurting out, "We should just build a damn jetpack already!" With a jetpack, we could get to class faster, which would leave us more time for personal projects, like building jetpacks ... and perhaps that's the conundrum.

Jetpack Dreams is certainly food for the souls of people like us, whose eyes leap to the sky to search for contrails every time we hear an engine. Montandon, who has written for The New York Times and Salon, uses his considerable talent and experience to craft an engaging and accessible narrative of North American jetpack dreamers. His book is at once a history of and update on the emergence of this futuristic device: Montandon starts with the 1951 Jet Vest (which never flew) and ends with his own test flight of Jet Pack T-73. Though his lack of engineering training shows — he explains the concepts of lift and drag in vague and utterly basic terms, recounts the jokes and activities of jetpack engineers with undisguised bewilderment, and even refers to one fellow dreamer as "Super Geek" — his writing still shines. His description of experiencing a zero-g parabola in a small airplane, for example, is spot-on; he deftly catalogues every detail of the "voluptuous panic" that is flight. Making your way through Jetpack Dreams will put you right at Montandon's side for his journey, which means you get a front-row pass for conventions, demonstrations, and even intimate conversations with jetpack enthusiasts.

You also get a front-row pass to his life: Montandon spends time introducing his wife, his daughters, his father, and several of his friends — along with, of course, jetpack builders, jetpack pilots, and jetpack financiers. This nonfiction story of the jetpack's evolution reads as easily as chick lit, and it rewards with adventures through aerospace. It could be a fun holiday read, but it's also a necessity for the library of anyone who wants — to take a line from the book — "[to kick] gravity's ass like it [has] never been kicked before."

JetpackDreamsTheBook.com

In addition to fantastic dialog (Weng: "Shall we get it on?" Irma: "Yes, my darling, bare your bod!") the movie features some truly epic character acting, as you'll see from our second clip, of a conversation between the evil Mr. Giant and his captured scientist, Dr. Von Koehler, who refuses to hand over the N-bomb.

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.