Where are our jetpacks?

Gernsback Publications / Frank R. Paul / Wikipedia

For more than a century now the jetpack has been a staple of science fiction.

From 1930s comics and 1960s television shows to a resurgence in entrepreneurial interest during the 2000s, the jetpack has continued to capture our collective imagination. After all, a backpack-sized object that would allow any person to take to the sky like Ironman through the power of space-age technology is enough to whet anyone’s appetite.

The technology has always seemed within our grasp, and the days where jetpacks might become part of our daily commute, or at least an affordable pastime for extreme sports enthusiasts, felt tantalizing close. However, our excitement seems to have been premature as commercially viable jetpacks have yet to materialize.

But still we yearn for the future that never came. “Where are our jetpacks?” the people demand. “Where is the version of the future we were once promised?”

So, why aren’t jetpacks readily available by now? And will we ever pilot our very own jetpacks? AeroTime investigates.

The name

First and foremost, it must be established that not all jetpacks are created equal. In fact, not all jetpacks are jetpacks. As the name suggests, a jetpack must have a jet engine and resemble a backpack, at least to some degree.

The former of the two prerequisites is quite problematic. In popular culture, most depictions, such as the King of Rocket Men, a black and white movie serial from the 1940s, or the Rocketeer from the 1991 film of the same name, feature non-airbreathing rocket engines. The most well-known real-life jetpack, flown by James Bond in Thunderball (1965), also uses rockets for propulsion.

The official name of that particular jetpack is the Bell Rocket Belt, which doesn’t quite have the same ring to it. There is simply no denying that ‘jetpack’ entered the public consciousness while its alternatives did not.

‘Pack’, the second prerequisite, also comes with its own share of problems. Many jetpacks, especially those with actual jet engines, are much more complex and extend beyond the dimensions of even the largest backpacks. Some, such as the appropriately named Jet Suit developed by Gravity Industries, have additional engines attached to the pilot’s arms and legs. Others consist of several washing machine-sized turbines that completely erase the standard image of the jetpack altogether.

Some jetpacks have wings, others don’t. Some can perform a vertical take-off and landing (VTOL), others cannot. And while it is tempting to acknowledge that they belong to different categories, such as wing packs, jet suits, rocket belts and turbine pants, two arguments speak to the contrary.

Firstly, all these contraptions aspire to imitate the same model – the compact, sleek, and endlessly stylish jetpack seen in comic books and films. They are based on the idea of an individual flying machine which barely extends beyond the wearer’s body.

Secondly, it is difficult to teach the public the subtleties of differentiating a jet from a rocket and a pack from a suit. Especially when we consider how engrained the idea of a ‘jet pack’ has become in popular culture and how it tends to operate as a catch-all term. Perhaps the typology of individual aerial transportation devices will become more widely known in the future when these devices become as commonplace as bikes. Currently, this does not seem realistic.

Consequently, any similar invention is categorized under the umbrella term ‘jetpack’.

This kind of generalization reflects some of the reasons why jetpacks have not entered the mainstream, mainly the physics behind the ways of making humans fly.

The rocket problem

Fictional jetpacks used rockets for one simple reason – they were conceived before the invention (or at least widespread knowledge) of the jet engine. Many real jetpacks use rockets as they offer significantly better thrust-to-weight ratio.

In order to function, the jetpack must lift the pilot, itself, and its fuel into the air. The bigger the difference between how much the engine weighs and how much it can lift, the better. The thrust-to-weight ratio of most jet engines varies between five and eight, meaning that they can lift five to eight times their own weight. Not bad.

However, the ratio of rocket engines tends to be 10 and more times bigger than that of jet engines. The Merlin 1D, which powers SpaceX’s Falcon 9, has thrust-to-weight ratio of more than 180, illustrating that a rocket-powered jetpack can be significantly smaller and lighter and, therefore, can carry a greater weight.

However, the insane thrust of rockets also comes with an enormous downside as they are incredibly fuel hungry. One Merlin 1D burns more than 30,000 kilograms (66,000 pounds) of liquid oxygen during the Falcon 9’s three-minute journey to the edge of space. 

The Bell Rocket Belt used hydrogen peroxide for fuel and burned 19 liters (5 gallons), allowing for 21 seconds of flight, nearly a liter per second. With such heavy fuel consumption, any practical use of the device went out the window.

The US Army, which ordered the development of the Bell Rocket Belt, dropped the idea of equipping soldiers with jetpacks after it became clear that under no circumstances could a more compact, convenient jetpack with longer flight times be developed. 

The Bell Rocket Belt was relegated to a showpiece, wowing the crowd with tiny hops at various events. During the opening ceremony of the 1984 Summer Olympics in Los Angeles, it nearly killed its long-time test pilot, Willy Suitor (a stunt pilot for Sean Connery in Thunderball), as the fuel tank was slightly over-pressurized, making the whole unit overweight.

It was only Suitor’s mastery with the controls that prevented a horrible catastrophe. After all, not only are rockets powerful, but they are also incredibly hazardous. In the best-case scenario, a crash of an unfortunate jetpacker would result in a fireball, and in the worst-case, poisonous hydrogen peroxide would escape, burning the eyes, lungs and skin of anyone in its vicinity.

While not all rocket fuels are equally dangerous during the event of failure, all rockets are incredibly dangerous when operated. Not only do they expel a tower of white smoke (as seen in popular depictions), but this is also accompanied by an ear-shattering roar and scorching heat.

The Rocket Belt’s nozzles were placed far away from the pilot and directed away from the wearer’s body. However, if an unfortunate pilot had decided to put their leg in the way of the jet stream, the 280 pound-force of the engine could strip the flesh from the appendage in no time. The same would happen if a person decided to stand too close to a working rocket pack.

The jet era

However, technological advancements made during recent decades have reinvigorated the idea of the jetpack. In recent years, it even became possible to build a jet engine small and powerful enough to be suitable for an individual transportation device.

This resulted in an uptick of ventures in the early 21st century all offering various high-tech takes on the jetpack. Air-breathing engines avoid many of the downsides experienced when using rockets and they tend to be less hazardous, and a lot less fuel hungry.

While there is still a danger of losing an unfortunately placed limb, at least now the flight time is not measured in seconds. Gravity Industries Jet Suit, invented by Richard Browning and sold by his company, can stay in the air for one to five minutes depending on the load, thanks to its five gas turbine engines, four of which are attached to the pilot’s arms. Jetpack Aviation’s JB11, with six turbojets in a more conventional backpack configuration, is advertised as having an endurance of 10 minutes, which would be just enough for a flight to the nearest mall in your average floating city.

However, the price for this fantasy trip will have to be paid with very real dollars. Reports from a few years ago indicate the cost of Browning’s Jet Suit as $440,000, while the JB11 comes in slightly cheaper at $340,000, which is the price of a small private airplane. There is little information about maintenance and operational costs of the devices but, given the fact that they are non-mass produced and require some advanced materials and manufacturing techniques, it is quite likely that the upkeep cost would be significantly higher than that of your average Cessna.

And even with that in mind, five-to-ten minutes is barely enough to cover several kilometers before the need to refuel.

“The energy density of the jet fuel still makes the difference quite marginal,” Browning told AeroTime, adding that, in part, this is thanks to the inherent disadvantages that come with the size.

“You lose efficiency. Think of massive modern airliner engines. They’re big because they’re efficient. Ours are tiny and they are not very efficient,” he said

Both the technology and the efficiency of jet engines continue to improve, and the mass production could, in theory, solve the issue of the cost. But it would create a host of other problems.

The human factor

Flying machines tend to be far more difficult to control than those that operate on the ground. The addition of a third direction – ‘up’ – really tends to complicate things, as does the lack of traction. Performing a vertical landing is a whole other level of mastery.

Another reason why the US Military dropped the Bell Rocket Belt was the pilot was required to use both hands to control it, which excluded the possibility of operating any kind of equipment. Controlling the device required a lot of concentration and skill, as the pilot was essentially balancing on the two rocket nozzles.

The problem of controllability has always been a major issue in preventing all kinds of flying machines from gaining mass appeal. Like jetpacks, flying cars have been plagued by these problems, and only recently, with the advent of effective artificial intelligence (AI) that can eliminate the human from the controls, have they become somewhat realistic. 

There is an indication that the same rule also applies to jetpacks, and without making them fully AI-controlled we simply can’t make them safe. But the companies that manufacture them are not giving up without a fight. Both Gravity Industries and Jetpack Aviation offer jetpack flying courses, and both claim to be able to teach a person to fly the pack within a couple of days. However, there is no denying that such flights are for entertainment purposes only. Making short hops in a sparsely populated area is one thing, trusting people to control what is essentially a missile in an urban environment, is another.

Browning himself does not hide the fact that the suit has a rather limited application in the real world due to its cost and complexity. His main target is the military, which has its own way of teaching people to operate complex machinery and making it reasonably safe. Apart from this, and perhaps a jetpack racing series Gravity Industries is currently working on, the potential for the jetpack to enter the mainstream is very limited, Browning claims.

David Mayman, founder of Jetpack Aviation, is equally skeptical of jetpacks being used by the lay public. While his company continues to work on new models of jetpacks, it is also pivoting towards other kinds of air transportation, mainly the Speeder, which is marketed as a “flying motorcycle”.

I don’t think it will be JetPacks that we see carrying people around cities in the future but aircraft like the Speeder, that can be operated fully autonomously, have a great future. Just as there are sedans and also motorcycles on the road I believe there will be large flying cars and also flying motorcycles (carrying 1-2 people),” Mayman told AeroTime via LinkedIn.

While there is no shortage of companies working on the similar concepts, it is still unclear if flying cars – as well as autonomous flying cars – will ever become widespread modes of transportation. However, a future with flying automobiles and bicycles seems far more likely than one with jetpacks.

Continuing on from Mayman’s statement, in such a future the classic jetpack would be like a monowheel with an internal combustion engine. Somewhat impressive, but hardly practical.

Swapping an internal combustion engine for an electric one could make things more appealing, however. According to Browning, there could be a market for this, and his company is already working on an electric version of a jetpack, which (while removing the last trace of ‘jet’ from the device) also tackles some of the dangers posed by jetpacks.

“There are ongoing revolutions in battery technology. Imagine a colder, quieter, simpler to operate, frankly – less-moving-parts-type of setup with an electric version where all the energy to fly for ten minutes is in the palm of your hand,” Browning said, while admitting that such a setup, if possible, is still quite far away.

But there is another more important point to discuss. The main appeal of the jetpack is unparalleled individual mobility, the possibility to take to the skies wherever and whenever the need arises. While lacked in the ‘cool factor’, this is exactly what flying cars and motorcycles will offer.

So, where are our jetpacks? They are here and just as impressive as the comic books predicted. But they are also incredibly dangerous and expensive.

A more practical version remains in the future, but its form may be a bit different than expected.

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