Flight Project FAQ
Why use batteries?
Lots of people have suggested for the purpose of our prototype tests, we should ditch batteries altogether, and just use a power cable from the wall. No weight of batteries, and unlimited electricity from the outlet! Awesome!
The current system draws around 32kW DC. A typical North American home will have a circuit breaker capable of providing either 24kW AC or 48kW AC.
Our final design is set to draw around 150kW.
Even if we could use a power cable from 6 houses on the street, you would still need to convert AC to DC – which might be easy for small projects, is almost impossible on this scale. A 100kW+ AC to DC converter would cost thousands upon thousands of dollars.
Not to mention the power cable would have to be as thick as your arm. Don’t believe us? Take a look how big the powerlines coming to your house are. The weight of the cable would be more than the batteries!
Different Battery Options:
Car Batteries – Car batteries are Lead-Acid. They are literally made of lead, one of the heaviest common elements you can find. We’re fairly confident it would be impossible to fly with the weight of a car battery.
Lithium Polymer Batteries – These are the batteries we are currently using. They are about three times as energy dense as a lead-acid car battery. That means a lithium polymer battery 1/3rd the size of a car battery, has the same amount of power!
Lithium Ion Batteries – Similar to lithium ion batteries, these have a slightly higher energy density than lithium polymer – but typically they cannot produce as much current. Since our system is VERY power hungry, with each EDF drawing over 150A, it would be very difficult to build a lithium ion battery pack (and time consuming).
Supercapacitors – Lots of people on YouTube show off SUPERCAPACITORS as the next big revolution in battery technology. Maybe they are – maybe they aren’t. But right now, supercapacitors are capable of storing large amounts of electricity – but not for very long. Again, since our system is very power hungry, if we used supercapacitors we’d fly for a few seconds before running out of juice.
Alternative flight options:
We’ve chosen to go with Electric Ducted Fans (EDF’s for short) as the most viable system to use in order to fly “like Iron Man”, while keeping the system compact. Other options include:
Gasoline engine – While fuel has a higher power density then batteries, they are much much bigger and heavier than electric motors. You could potentially use a sport bike engine – but then you’d be building a mini helicopter, not flying like Iron Man.
In case you’re interested, someone has tried to build a gasoline powered drone style vehicle for human transportation. Spoiler! They’re switching to electric for their next revision.
Plain props – The most efficient way to fly with electric motors would be to use large props, like building a giant quadcopter or drone. We actually made a design for this, and the entire craft was about 2.5 meters in diameter. This would work! But again – you wouldn’t be flying like Iron Man.
Rockets – We’ve already tried these. Watch the beginning of the series! Basically, while they have a lot of power, they only last a few seconds, and cost a lot of money. Not to mention the jet plume can burn through Kevlar or even thin sheet metal.
Jet Engines – These would be fun. They’re about the same size as the larger EDFs we want to use, and put out about the same thrust. They’ll last longer since fuel is more power dense than batteries – but they still cost as much or more than EDFs. And they’re also harder to control – for stabilization during flight, jet engines probably wouldn’t work.
Oh, and the exhaust coming out of them is around 800 Celsius, which means we’d also have to protect ourselves a lot more than with EDFs.
It’s also been done before, though more like Falcon’s flight suit than Iron Man.
Hybrid – Perhaps the solution lies in using multiple technologies to fly? Use the power density of jet engines, coupled with EDFs for stabilization, and you might have something that could work!
In fact – it’s been done! It’s called the Flyboard Air – it uses jet engines, and EDF’s. The catch? The jet engines they use are about $50,000 a pop, and the total cost of the prototype was over $250,000. It also represents a few years of engineering by a company that actually makes stuff that flies. In other words – they’re a bit above our level as YouTuber’s working out of a garage.
Making our own parts:
Because of the huge cost of parts for this project, we’ve received a lot of questions about whether or not we could just make our own components. The short answer is no, but we’ll go into a bit more detail.
We’ve received numerous suggestions to design and build our own batteries based on research projects involving Aluminum Air batteries, or even graphene based batteries.
While it may be possible to make some new battery technology fancy enough for a science fair, the power level we need for this project is orders of magnitude higher than that.
It’s estimated that the final system will require around 150kW of power. To put that in perspective a massive wind turbine with a 25m rotor diameter only produces 100kW – which is enough to power 15+ homes.
If we could design any kind of battery that could put out 150kW of power – we’d be patenting it and revolutionizing the battery industry. It’s just not going to happen.
One of the biggest costs to the project are the EDFs themselves, with the ones we want costing nearly $5000 USD.
We are looking into the possibility of 3D printing the blades ourselves which could bring the price down. This is possible for smaller EDFs – but might be difficult for larger ones that we would need.
Remember, an EDF blade needs to be strong, smooth, and perfectly balanced. 3D printed parts typically do not have a good surface finish, unless they are printed on a very expensive 3D printer (which we do not have).
It’s possible you could print the EDF blade on a metal 3D printer – but even using a metal 3D printer can cost thousands of dollars per part. It might even be cheaper to CNC machine.
We are going to keep looking into the possibility of making our own EDFs, but it’s unlikely we’ll succeed.
We’ve even received a few questions asking whether or not we could build our own DC motors for the EDFs. The motors aren’t actually the most expensive part of the project – the EDF blades and duct – as well as the speed controllers.
It is possible to make your motor, or even rewind another motor to put out more power. But remember – the motors we’re using spin at 40,000 RPM and are precision components. Even if we could manufacture them ourselves, the amount of time it would take us to build them… would be less than it would cost to buy them.
Other questions? Leave us a comment!
For more information about the project and our design, check out our GoFundMe campaign at https://gofundme.com/theHacksmith