October 21, 2021

I, Science

The science magazine of Imperial College

Ever since the Wright brothers achieved the first manned powered flight in 1903, we have been dreaming of our own personal flight machine. Before that it was gliders and before that, our own set of flapping wings. Over a third of people dream of flying but how close are we to living that dream? Where is my jetpack? And my futuristic supercar for that matter?


Though the German army experimented with jump belts during WWII, achieving a jump distance of about 60m, the Bell Rocketpack of the 1960s would seem to be the first glimpse of a jetpack future. Powered by hydrogen peroxide, it avoided the high temperatures of conventionally fuelled pulse jet engines such as those used on the German jump belt. When the hydrogen peroxide comes into contact with a catalyst inside the Rocketpack, it rapidly decomposes into superheated steam and oxygen, which is directed out of the rocket nozzles to lift the wearer off the ground. However, hydrogen peroxide powered jetpacks have a low specific impulse (low fuel efficiency) and even today’s hydrogen peroxide jetpacks can only carry enough fuel for about 30 seconds of flight. The problem of carrying more fuel is that it makes the total load to be lifted heavier and the pack subsequently uses the fuel up even more quickly.

“We would need new rules about where you can use your jetpack, as well as when, and how fast, you can go. ”

Jetpacks powered by kerosene fuelled turbojet engines can provide much longer flight times but are highly complex and somewhat expensive. The only successful one currently resides in a museum, unused since 1960. Kerosene is also an example of a jetpack fuel that can severely burn the user’s legs in flight.

This May, Yves “Jetman” Rossy, was reported to have jetpacked over the Grand Canyon. He is also credited with crossing areas of ocean by jetpack. However, the Swiss daredevil didn’t start from ground. Not in the jetpack anyway. For each flight he dons his rocket powered wings and jumps from a helicopter or plane. What follows is some impressive gliding, but jumping from a plane and landing with a parachute doesn’t seem to fulfil the jetpack concept.

Florida company Jetlev Technologies have come up with an interesting alternative to jets of air as propulsion for a jetpack. The Jetlev uses jets of water to raise the user into the air. To improve the thrust to weight ratio, they have left the propulsion engine and fuel on the “ground” – on a floating raft attached to the pack itself. Water is supplied to the Jetlev by a long flexible tube which doubles as a tether, keeping the propulsion unit nearby and stopping the pilot from flying above 30m, the maximum flight height of the Jetlev. The company claim that the jets of water mean that the Jetlev is easier to manage than an air propulsion jetpack and that with their training programme, anyone can master it.

Jetpacks using air propulsion are notoriously difficult to control, bringing in safety issues surrounding their commercial use. The upright position of the person using a jetpack is not very stable. We would need new rules about where you can use your jetpack, as well as when, and how fast, you can go. I suspect that Jetlev Technologies have got it right for the time being, concluding on their website that “jetpacks are not practical for commuting and should primarily be designed for recreation”. Online gadget store Firebox is selling the Jetlev Flyer for only £115,000. Hurry, you don’t want to miss out on free delivery!

Aston House Martin

Maybe a flying car is more to your taste. Moller claim that the Skycar, which has a public test flight scheduled for October this year, is an important step on our route towards independence from gravity. Designed to carry four passengers, Moller’s creation is powered by eight rotary combustion engines. A rotary combustion engine does not use pistons, as in traditional combustion engines, but creates the compressed compartments of fuel-air mixture to be ignited using a three-apexed rotor. This avoids the agitation and wear of a traditional piston engine, making it a smoother ride. The Skycar directs thrust from its four ducted fans to enable it to take off and land vertically and to move horizontally. It’s not been seen in flight since 2003 but Moller seems confident that it will be able to perform at its test flight and aim to have the prototype available in 2012.


Whilst flying around might seem very exciting and glamorous, actually creating an air highway would be a logistical nightmare. One or two personal flying devices with good control can easily avoid each other but imagine the aerial-M25 on a Monday morning! The solution might lie in the development of Earth bound vehicles that are able to avoid crashes by themselves. V2V (vehicle to vehicle) communication has allowed a fleet of robotic cars to drive autonomously through the streets of San Francisco and come out unscathed. To work for everyone however, it would need to be fitted in every vehicle on the road and will require a way of communicating with the driver rather than simply being a robot. Cars developed by Volvo, Mercedes and Honda can stop a car from crashing into another using laser and radar systems without communicating with the other vehicles involved. These systems take over control from the driver when it is needed but aren’t perfect and only work to avoid collisions in which the car runs into something else. A system that avoided crashes completely would need to be much more comprehensive.

Flights Of Fancy

Whilst the quest for a personal flying machine will surely continue for many years to come, it doesn’t look like jetpacks are just around the corner yet. The power needed to get a human off the ground vertically and the control required to fly them around safely is more complex than one might first think. Getting a flying car working may well soon be a reality come the Skycar’s October test flight, but the daily commute is probably going to remain on the ground for a while.