How Jet Packs Work

The failure to develop a useful jet pack is primarily due to the physics of making a human being fly. We're just not aerodynamic creatures. Nothing in the shape of a human creates lift when we're moved through the air. That means that a jet pack has to create all the lift with pure thrust. Generating that much thrust uses up a lot of fuel -- quickly, too. The true barrier to useful jet pack development is the weight of fuel. We have jet packs, but the reality is that they only work for about 30 seconds. Adding more fuel to prolong flight time would make the jet pack heavier, requiring even more fuel. See the dilemma?

­The­ fuel weight issue has severely limited the usefulness of jet packs. Thirty seconds of flight time isn't enough to do anything other than look for a good place to land. This brings up the second major problem with jet packs: safety. Strapping a rocket or jet engine to your back is inherently dangerous. Shooting yourself up into the air, knowing you only have 30 seconds to get back down, makes it even more dangerous. Since every extra pound that you carry reduces flight time even more, there's not much room for back-up safety systems.

The final flaw with jet engines is one most people don't consider when they fantasize about soaring smoothly through the sky: noise. If you've ever been near a jet engine or a large rocket when it was running, you know they are incredibly loud. One of the early proposed military uses for jet packs was for reconnaissance; however, as soon as the U.S. Army realized that any soldier scouting with jet pack would be heard by the enemy literally miles away, they knew it would never work. ­The noise would be a problem even in applications where you're not in danger of being shot at. Imagine even one jet pack equipped construction worker in a crowded city. The deafening noise would cause a lot of problems for other workers and anyone unfortunate enough to live or work nearby.

Of course, in the more than 50 years since the first jet packs were developed, we've made some amazing advancements in technology. Surely, if we applied our best scientific minds to the problem, we could overcome these flaws and create functional, useful jet packs, right? It's entirely possible that we might, but there's no demand. It turns out there's not much use for jet packs beyond the, "Hey, cool, jet pack!" factor. Just about any use you can think of for a jet pack can be accomplished with a far cheaper and more reliable technology. It's also not very efficient to transport a single person by air. If we need to get someone somewhere through the air, we can use an airplane or a helicopter and take several people or even some extra cargo.

What was the driving force behind the creation of the first jet pack? Who wanted it built and why? Take a look at the next page to find out.

T­he U.S. Army began researching rocket pack technology in 1949 at Redstone Arsenal in Alabama. The Ordnance Rocket Center at Redstone was the agency in charge of the program. Their goal was a back-mounted device that could propel a single soldier into the air. In 1952, Thomas Moore successfully tested a rocket pack which lifted him into the air, but only for a few seconds. A device called the Jumpbelt was demonstrated at Fort Benning, Ga., in 1958 with a slightly greater flight time. News footage of these demonstrations fueled the public's interest in jet packs. The project was then shifted to Bell Aerosystems in Buffalo, N.Y.

Bell developed something they called the Rocket Belt, though the official name was the Small Rocket Lift Device (SRLD). Over the course of the next decade, Bell's Rocket Belt made several improvements in speed and flight time, reaching speeds up to 10 mph. Plans for a jet-powered version, which did achieve longer flight times in initial tests, were scrapped when the military decided it didn't fit the design parameters because it was too large and heavy

[source: Scientific American].

At that point, serious industrial development of jet pack technology came to a halt. Virtually all jet packs developed ever since have been created by amateur inventors or independent companies, and they're used primarily for public demonstrations at thrill show events or for stunt scenes in movies. A prime example of this is Rocketman. There isn't actually a single person known as Rocketman, rather it's a franchise that operates worldwide giving demonstrations of a rocket belt based on the Bell Aerosystems model. Rocketman can be hired for publicity work and movie stunt work, including custom advertising and special performances [source: The Rocketman].

How much horsepower is developed by a rocket belt, and how much can it actually lift? You may be stunned by the answer. Find out on the next page, where we provide you with a few of the more interesting rocket belt technical details.

Rocket belts run on hydrogen peroxide fuel, which is not explosive on its own. This makes rocket belts slightly safer than jet packs. When the hydrogen peroxide is combined with pressurized liquid nitrogen and a silver catalyst, the chemical reaction generates superheated steam that shoots out of twin rocket nozzles at 1,300 degrees Fahrenheit (704.4 degrees Celsius). There's no flame, but it's still extremely dangerous. The result is 800 horsepower or about 300 pounds of thrust [source: CNN.com]. Hydrogen peroxide is a good, reliable fuel, and it's only by-product is water. However, it's very expensive, costing about $250 per gallon (3.78-liters). Each flight uses almost all of the fuel in the tank -- about seven gallons (26.5-liters) per flight.

The typical rocket belt weighs 125 pounds (56.7 kilograms) and the pilot has to weigh 175 pounds (79.4 kilograms) or less, or the rockets won't provide enough lift. The right hand controls the throttle, while the left hand controls yaw, which is side-to-side motion. Although rocket belts have short flight times, they can reach speeds up to 80 mph and they accelerate incredibly quickly. Landing is accomplished by gradually easing up on the throttle [source: Scientific American].

Does all of this make you want to rush out and buy your own jet pack or rocket belt? Are you willing to go through the training? Are you willing to pay the price? Keep reading to find out just how much a jet pack or rocket belt will set you back.

A handful of companies currently offer jet packs for sale to the public. JetPack International (Jet PI) is an American company founded by Troy Widgery, creator of Go Fast energy drinks. Jet PI took 50s-era rocket belt designs and updated them with modern fuels and materials. These efforts reduced weight, improved thrust and increased flight time to just over 30 seconds. In addition to public demonstrations, Jet PI offers some of their rocket belts and jet packs for sale. Their T-73 model is a true jet pack, with a claimed flight time of nine minutes and a sale price of $200,000. They formerly offered a rocket belt for sale for $150,000.

­T­ecnologia Aeroespacial Mexicana (TAM) is a Mexican company that offers a range of rocket-powered products, including the TAM Rocket Belt. The cost is $125,000. Both Jet PI and TAM include a training period in the purchase price. TAM says they include hands-on training and 10 test flights, along with set-up, maintenance and 24/7 technical support.

Thunderbolt Aerosystems has also announced plans to develop a jet pack with a flight time of more than 30 minutes. They originally sold a rocket pack for $125,000, but they claim the design rights were sold for use in "emergency and earthquake rescue operations" [source: Thunderbolt Aerosystems]. Their current model rocket pack has a claimed 75-second flight time.

Extensive training is a really good idea -- jet packs and rocket belts can be very dangerous. There are no reported serious injuries or fatalities as a result of jet pack use, but that probably has a lot to do with how rare they are. In most flights, the pilot is actually tethered to the ground, preventing loss of control. There are no back-up safety systems because the limited flight time of a rocket belt means the pilot will never get high enough off the ground to successfully use a parachute. Flying is very difficult -- the pilot has to navigate in three dimensions, and a human wearing a rocket is not a very stable flight platform. For these same reasons, it's not a good idea to try to build your own rocket belt or jet pack. In fact, the television show MythBusters examined plans for a homemade jet pack available on the Internet. Using high-powered fans, this device was supposed to provide lift via air thrust. The MythBusters team proved that that the plans were not viable.

Would you like to find out more about jet packs, rocket belts and other personal aircraft? Then check out the links on the next page, they'll provide you with plenty of great information.