The Jetpack thread

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Doggzilla

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So for quite a while inventors have been trying to create a functioning jetpack, with many resorting to strapping a number of RC model engines to themselves.

One of the inventors, Frank Zapata, just had a failed attempt to cross the English channel on one, failing about halfway through.

https://www.npr.org/2019/07/25/745330126/franky-zapata-falls-in-english-channel-trying-to-cross-it-on-high-speed-hoverboa?utm_medium=social&utm_term=nprnews&utm_campaign=npr&utm_source=facebook.com&fbclid=IwAR2kmXkUADEip8_frbEN7z7gAS-3FgQ9ROO3yRN3HcxPzXVcxl-a0y0jDNI

I think this deserves its own thread to keep track of jetpack developments.
 

Scheny

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This is another "super efficient" and "super easy to learn" hoax as all the others. Just put a guy with a gun on it and pretend to investors that military loves your design.

The argument with best power to weight ratio is bullshit, as he admits it takes a galleon of fuel per minute. So, if you include fuel to the equasion, it is not better than a design with fans and lithium batteries which would also work for 10 minutes. As far as I have heard, he crashed it during refueling. So, how much is crossing the channel worth, if you have to refuel in the middle. It is not more than a PR stunt.

In addition, the jet engines are reacting very slow (~3 seconds at that size) and they need 5 thrusters +2 for steering. It can withstand a failure of one turbine each. If they would use a multicopter (aka drone) with electric motors, it would need 6 (ideally 8) motors, which each have a hundred times higher reliability. Electric motors also react within milliseconds, so you could incorporate an active control mechanism, whereas the flyboard relies on a rider who balances it mostly by his feet... Basically it is just a jet-powered version of the previous water-powered flyboards they used to create before. These utilize a firehose connected to a jet-ski engine and this is what they are using to teach the riders before they transition to the jet version.

Coming to the price, these turbines are 2500€ each, if built for model planes, or even 5000€ if built for manned purpose. You can get a lot of motors and lithium for that price...

Last but not least, the license. I am really curious which country would allow to fly these without a license. Here in Europe you can only use this below 100ft and above private property. I was really baffled to see they let him fly above a huge crowd. Just imagine he would suffer a twin failure (very likely for this toy turbines) and land with 5 remaining jets torching dozens of people...
 

Doggzilla

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Very valid points.

The best solution is probably somewhere in between.

Instead of having a bunch of small inefficient turbines it should have one larger generator turbine driving electric fans and a 30 second backup battery for emergencies.

The large turbines are several times as efficient, and have higher power to weight ratio, which would likely overcome the additional weight of a generator.

Just from the efficiency increase alone it should make it possible.
 

Doggzilla

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Oh, and even a very small set of wings would vastly increase speed. The Chinook did this once and the performance increase was very impressive.

He’s got over 1:1 thrust ratio, and being able to divert even a third of that to forward thrust would give him a effective forward thrust of 1:3. That’s as good as a business jet.

So even very small wings would free up vast amounts of thrust.
 

Mad MAC

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I guess we should also note that the Martin Jetpack (aka Martin Aircraft Company) is no more one. Apparently in part due to the difficulty in dealing with an engine failure below the effective height of a ballistic chute (there are other reasons as well apprently).
 

Doggzilla

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Unfortunately that does not surprise me.

But their results were still outstanding from a technical point of view. Over 700lbs of thrust from 200hp. That is almost identical to a 200hp lycoming with prop.

I wonder how efficient that design would be with one larger ducted fan instead of two. Because those are really good efficiency numbers for a ducted fan.
 

Scheny

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Instead of having a bunch of small inefficient turbines it should have one larger generator turbine driving electric fans and a 30 second backup battery for emergencies.

The large turbines are several times as efficient, and have higher power to weight ratio, which would likely overcome the additional weight of a generator.

Just from the efficiency increase alone it should make it possible.
The best turboshaft engine in this size (the Jetcat) has an efficiency of 3000g/kw/h. Just for comparison, a car engine is in the area of 200g/kW/h...

Airbus helicopters (former Eurocopter) has proved that It even makes sense to exchange the 10x more efficient turbine they have in a H-145 by a diesel engine. In order to keep the MTOW, the fuel is decreased by 50%, but also consumption is decresed by that amount. So range and power stays the same, but the amount of JET-A1 is wayyyyy less and also servicing is cheaper for a combustion engine.
 

Scheny

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Apparently in part due to the difficulty in dealing with an engine failure below the effective height of a ballistic chute (there are other reasons as well apprently).
This argument will not count for them :cool:. A company which describes a product as safe and easy to use, where you have to balance with your full body has different safety standards than the average pilot. As a certified safety manager I can tell you, that I never met someone in my field who tried to fix something by adding more redundancy (more engines, we need more engines!!!).

Just one question: Why is everyone flying with a single Lycoming instead of using 10 pieces of lawn mower engines?
 

Aesquire

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The Zapata Flyboard is for young, athletic, and talented people. Not for the average Joe.

First time I saw the jet powered version, I immediately noticed how rigid and controlled his body was. This is a pro who has hundreds of hours flying a water jet version, minimum. I'm willing to bet he is expert at skate & snow boards too. He also has far above average leg strength and control. Very high balance & kinesthetic abilities.

I've watched the evolution of the water jet "boards" from stunt man experiments to tourist money vacuums. In the process, the jet nozzles moved up the body and seats & body bracing handle bars were developed. Basically powered by a hose attached to a Jet Ski impeller. Tourist models retain the standard Jet Ski controls so a life guard/rental company employee can shut off the flow and rescue the stunned or incapable tourist after he slams into the water. Here is one company that sells the Zapata brand, among others.

http://www.jetpackamerica.com/phone/index.html

You might notice the proliferation of shoulder high nozzles as originally used on the Bell rocket belt. This puts the thrust above the C.G. & is much more stable, reducing the skill needed. The board variants demand balance, fit legs with strong knees and ankles, and talent.

I freely admit bias here. Hundreds of hours with a hang glider that while it demands some kinesthetic skills, can be flown by the average 14 year old, but my board riding experience is far less. The last skateboard I owned had steel wheels, so... Iron age before polymer wheels. Obsolete and many decades out of date attitude. I have snow boarded, on regular ski hills, but that experience too dated from near the commercial beginnings of the sport. I was already an intermediate snow skier, took a lesson in the a.m. & plummeted down the ski hill from the top in the afternoon. However, I never did flips and stunts on boards or skis. Competent to turn and stop, but not acrobatically talented or trained.

With those limited abilities, my initial reaction to the water Jet boards was " great! Twist the throttle & hit the pier! "

Oh, I'd love a Martin back pack flying machine if I didn't have cyborg knees, and a pre-arthritic spine, or a copy of a rocket/jet pack. But those require an order of magnitude less skill & athleticism of a Jet board controlled by legs and ankles. There's no inherent stability in these boards designs.

https://mashable.com/article/bastille-day-hoverboard-france/

I've also seen another version with jett engines on the forearms for additional control, allegedly inspired by the Iron Man movies.

In conclusion, back pack designs appear to require far less athletic skill than board types. Personally, I would fly the more stable backpack designs, but will leave the stand on type to the talented jocks.
 

Doggzilla

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The best turboshaft engine in this size (the Jetcat) has an efficiency of 3000g/kw/h. Just for comparison, a car engine is in the area of 200g/kW/h...

Airbus helicopters (former Eurocopter) has proved that It even makes sense to exchange the 10x more efficient turbine they have in a H-145 by a diesel engine. In order to keep the MTOW, the fuel is decreased by 50%, but also consumption is decresed by that amount. So range and power stays the same, but the amount of JET-A1 is wayyyyy less and also servicing is cheaper for a combustion engine.
The size has a noticeable effect on this.

Was just comparing the fuel consumption of different sizes and with the Jetcat using one 80lb thrust instead of 4 20s saves 30% in fuel consumption.

The new models of Kingtech are roughly 30% better than that (870g/min @70lbs vs 1300g/min at 84lbs)

There is also a roughly 10% improvement in thrust to weight ratio as well, not including additional accessories or removal of mounts. I imagine it will be closer to 20% weight savings with that included.

I can’t find the larger 120-150lb class turbines they used to make, but it’s probably safe to say they would increase range by 40-60% if used in a hybrid electric just from the weight and fuel savings of using a larger turbine.
 

MadProfessor8138

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Uuuummmm...guys.....
That has already been done....
There was a 2 hr 15 min documentary on the subject a few years ago in every theater around the world.
And they also released the plans for free download.....

F3611RQH994BU7B.LARGE.jpg
730b3_glider.jpg

Sorry....I couldn't resist getting a laugh on the subject.

Kevin
 

MadProfessor8138

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All kidding aside.....
The problem with technological advancements stems around economics.
Take the economics out of the equation and watch technology advance by leaps and bounds.
The reason the military has such advanced technology is because they are government funded and dont worry about being unemployed if they dont produce a profitable product.
Now,for a private company.....they need to finance their R&D through private funds and wont venture into areas that wont produce a profit for them.
We put men on the moon,sent a probe past Pluto and it's still going,have a golf cart cruising around Mars....etc....but yet, to this day,we dont have products in our every day lives that should have been there 30 years ago.
Why hasn't battery technology advanced ???....there's a gentleman that has developed a lipo that wont short out or catch fire if it's over charged or even cut in half...its made like a bandage....he's had to develop it on his own....and it works great,btw.
Why hasn't biotechnology advanced and given civilization mechanical limbs,eyes,organs...etc.
Once again,the research has been privately funded and advances are extremely slow.
Where are the clean cities,advanced civilizations,technically advanced products..etc....that you see in the tv shows and movies from the past to the present ???.....Star Trek,Buck Rogers....
Our society isn't like that because theres no profit in it......we are driven by money !
Take the money out of the equation and everyone will have their jetpack.......

Kevin
 

Doggzilla

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Ya, it definitely needs to find a profitable niche.

I was reading something a few years back that showed that the vast majority of helicopter hours were harvesting Christmas trees because it was so much faster to get them from the hills to the trucks. Something close to 2 of 3 hours was christmas tree harvesting at the time.

Jetpacks need something similar. Put 3-4 jetpacks together and it could lift over 500lbs useful load.
 

Aesquire

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The problem with jetpacks isn't money. ( It's always money, anyway )

It's the landing gear.

Fuel = weight. Doesn't matter if the fuel is hydrogen peroxide or Jet A or batteries. A typical human can't carry enough weight to give any reasonable range. Going from rockets to turbofans to ducted fans may more than double range, but that's from under one minute to under a dozen. Incredible gains! But still a toy since only several magnitudes of energy storage improvements are needed to get to the traditional $1000 hamburger.

However, add landing gear, and the human leg & spine limits are gone.
 
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