When the automobile first rolled onto dirt roads in the 19th century, it allowed us to go places we'd never been, and let us get there in a matter of hours instead of days. Unlike the train, which confined people to stops and schedules, the car gave us an amazing sense of freedom. Today, our cars still give us great freedom, but in many cities that freedom is tempered by the number of hours we have to sit in traffic jams. What used to be a 20-minute drive in some cities is now a commute of an hour or more.
Photo courtesy Millennium Jet
Interest in personal jetpacks is growing as technology makes their future use possible.
But there is hope -- engineers are attempting to give us back true mobility by developing personal jetpacks that will eliminate the need for roads altogether!
Just the word "jetpack" brings to mind images of Boba Fett (the bounty hunter from "Star Wars"), the 1965 James Bond film "Thunderball," and the rocket man who flew into the opening ceremonies of the 1984 summer Olympics in Los Angeles, CA. The latter two used the Bell Rocket Belt, a jetpack technology that has never gotten off the ground for extended periods of time. However, we could see some form of commercially marketed personal jetpack within the next few years. In the section of How Dewsoft Stuff Will Work, we'll take a look at some different kinds of jetpacks that could give us the ability to go anywhere, anytime.
Propeller Powered Jetpacks
The personal flying vehicle closest to entering the commercial market does not look like any flying vehicle we've seen before. The SoloTrek Exo-Skeletor Flying Vehicle (XFV) being developed by Millennium Jet works something like the Harrier jet, lifting off vertically. But instead of jet propulsion, the XFV uses propellers to lift the aviator off the ground.
The Exo-Skeletor Vehicle can fly to 10,000 feet and travel at up to 80 mph.
Once strapped into the vehicle, which has also been called an air scooter, the engines will turn the overhead duct fans at 3,500 to 4,000 revolutions per minute (rpm) to provide adequate thrust to propel you into the air. The device is 7.5 feet (2.3 meters) high, and operators are required to be between 5 foot 4 inches and 6 foot 6 inches (163 to 198 cm) tall and weigh between 115 and 275 pounds (52 to 125 kg) for maximum maneuverability and safety.
Once airborne, you can zip over tree tops at a top speed of 80 mph (129 kph) for 150 miles (241 km) on a 10.5-gallon tank of gas before refueling. Average cruising speeds are between 46 and 69 mph (74 and 111 kph). Because it can climb as high as 10,000 feet (3,048 meters), there's the possibility that the XFV would share its air space with other small aircraft. The compact size of the XFV will allow it to land on any space larger than a kitchen table.
While the company has not said when they will market the vehicle, it reports that there are applications for private use. Initially, it's likely to be used by paratroopers, who would use the XFV to fly into battle. There are four major components of the XFV that will enable it to fly us to work someday:
At the heart of the patented XFV is a 350-pound (130-kg), 130-horsepower, four-cylinder engine that uses everyday 87-octane gasoline, the same gas that you put in your car. Like your car, the XFV has a piston engine. But while an automobile engine and many aircraft engines operate on a four-cycle regime, the XFV engine operates on two cycles. In a four-cycle engine, there are a lot of moving parts that are prone to catastrophic failure, including intake and exhaust valves, pushrods, valve lifters, camshafts, timing belts and oil pumps. The two-cycle engine has fewer moving parts, although it still includes some, such as crankshafts (see How Two-stroke Engines Work for details).
- 130-horsepower gasoline engine
- Drivetrain that drives the ducted fan blades
- Counter-rotating ducted fans (two)
- Steering system
The engine is connected to a system of drive shafts, universal joints and gear boxes, which drive the counter-rotating ducted fans. The ducted fan blades have a fixed pitch, meaning they are rigidly fixed to the central rotating fan hub at a set angle. The fixed-pitch (as opposed to variable-pitch) fan further reduces the number of moving parts at work on the XFV. However, the downside of fixed-pitch blades is that they cannot be adjusted during flight.
In normal operation, users would control the XFV through the use of two hand-control grips and control arms, and by shifting their weight from side to side. The aircraft has three-axis control: forward and backward, left and right, and up and down. By twisting the left-hand grip, you can increase the rpm of the ducted fans to accelerate the speed of the aircraft. The right-hand grip allows you to adjust the tilt of the fans for forward or backward flight or make the XFV spin on its vertical axis. Shifting your weight will allow you to make turns. Like a helicopter, the XFV can also hover in a stationary position for up to three hours. In the case of any catastrophic failure, the aircraft would automatically deploy a parachute to safely bring the craft down.
Millennium Jet recently received $5 million in funding from the Defense Advanced Research Projects Agency (DARPA), which is the research arm of the U.S. military. The XFV has completed nearly 400 wind-tunnel tests at the NASA-Ames Research Center. Millennium Jet is analyzing how to market the aircraft, but hasn't said when it might be available to the public. The price is projected to be comparable to that of a high-performance sports car.
Rocket Propelled Jetpacks
The world got its first look at personal jetpacks in the 1960s when Wendell Moore, an engineer at Bell Aerospace, designed the Bell Rocket Belt. Partially, funded by the U.S. military, this was a small back-mounted pack that could thrust a person into the air for what amounted to a 20-second hop, instead of actual sustained flight. The rocket belt and its test pilot, Bill Suitor, became very famous in the late 1960s touring the world, and even made an appearance in a movie. When Moore died in 1969, Bell Aerospace scrapped plans for the personal rocket belt.
Photo courtesy U.S. Patent and Trademark Office
Wendell Moore filed a patent for this propulsion unit in June 1960. This illustration is from patent number 3,021,095.
In 1995, the technology used to build the Bell Rocket Belt was revived by a group of Texas engineers who designed a slightly enhanced version called the RB 2000 Rocket Belt. The redesigned belt was able to travel 50 percent farther than the Bell Rocket Belt, enabling users to stay airborne for 30 seconds instead of 20.
Rocket packs contain three substances that make up a chemical reaction that produces thrust:
Two metal tanks mounted on the rocket pack are filled with a total of about 6 gallons (23 liters) of hydrogen-peroxide propellant. When the operator opens the throttle, the high-pressure nitrogen gas is released, forcing the hydrogen peroxide into a catalyst chamber. Once inside the catalyst chamber, the hydrogen peroxide reacts with the silver material, which turns the hydrogen peroxide into a high-pressure, superheated steam that measures 1,370 degrees Fahrenheit (743 degrees Celsius).
- Hydrogen-peroxide propellant
- High-pressure nitrogen gas
- Samarium-nitrate-coated silver (which acts as a catalyst)
The steam shoots out through two bent tubes that run from the top of the tank down the side, just behind the operator's arms. The tubes are wrapped in insulation so that no heat is lost. Because of the heat, the operator must wear a heat-resistant suit to prevent burns. Water and vapor exiting from the two nozzles at the end of the exhaust tubes produce more than 300 pounds of thrust, which is more than enough to propel a person into the air for a short rocket flight.
Rocket packs are unlikely to become commercially marketed products due to their drawbacks. While they have been tested at speeds of over 100 mph (161 kph), they lack the agility displayed by Millennium Jet's XFV. Also, a rocket pack uses up its 6 gallons of fuel in just 30 seconds of flight, whereas the XFV can travel for more than three hours on 10 gallons of gasoline. No company is currently working on a rocket-pack design, and the RB 2000 has not been tested since 1995 due to legal battles among its designers.
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