The Pacific Drone Challenge, inspired by the Xprize, has the goal of pushing the boundaries of what is possible with civilian drones. You have to do it for your name in the history books as there is no financial prize. Could we see this challenge accomplished by the DIY community? Getting the permits, insurance and having a pilot licence is not for everybody, but many are flying aircraft as a hobby, so it is possible. Right now, the Japanese company Irobotics and the organisation SabreWingAircraft accepted the challenge.

A quick calculation seems to show that battery only is out of the question for that distance. The best gliders have a 70 to 1 ratio. This would mean you would have to start at a height of 100 KM (or realistically, climb 100 km over the whole trip). Even if your plane was only made of batteries and it had perfect efficiency, the energy density of batteries is barely enough to provide the energy required (using an energy density of 950000J/kg). Optimization of the motor, the propeller and the air-frame is will be critical to succeed.

How would you go about this challenge? Build from scratch? Modify a glider? Use a flying wing? Let me know in the comments!

## Comments

This is a joke.....right?

A competition with contestants organising their own authorisations to use the proposed fields and access international airspace? Isn't the whole aim of an organised event to have the organiser arrange these permits so that every team doesn't have to do it?

Other than setting up a web page, what are the organisers actually providing?

My first thought was to build a blimp, giving you 'unlimited' flight time to solar charge batteries etc. My second was that Japan to USA is the same direction as Jet streams flow if I am not mistaken.

In 1998 an Aerosonde UAV (2.7m wingspan, 20cc engine) managed to fly 3200km and cross the Atlantic ocean with 6 litres of fuel over 26 hours.

This new challenge is a little over double the distance, but with an increase in scale and more modern materials it shouldn't be too hard to accomplish (at least technically).

Well, you could adopt an albatross strategy and include perching to solar-recharge, dynamic soaring and thermaling to do the business.

Solar or diesel. Where's the Atlantik Solar team?

With numbers: a 1000kg glider dropping 1000 m and a glide ratio of 1:50 will require (1000kg * 1000 m * 9.81 m/s) = 9.8MJ. Thus, you need 9.8 MJ to travel 50 km. From there, you can figure out the specific energy density needed.

The glide ratio and the mass of the glider allow you to calculate the energy needed to fly a given distance. It is not an approximation: it represent the real energy loss due to aerodynamics effects. A motor will not be 100% efficient, so the actual energy required by an engine will be higher, but this calculation will give you a baseline.

It is an energy based calculation. Gliders have a glide ratio: how much they go forward/how much they drop. If you assume no thermal (it would be difficult over the ocean, but maybe not impossible), the glider will drop of 45000/70 miles, or about 100 km to cross the ocean. Obviously, you cannot go to 100 km altitude, but the glider will have to spend the energy to drop 100 km over the whole flight. Imagine the glider climbs 1 km with a winch, then goes forward 70 km. Repeat this with smaller and smaller steps: in practice, the engine is always on and it acts as your winch, which allows the vehicle to keep its altitude.

Once you have establish the minimum energy required for a given mass, you can look the specific energy of different fuels. It turns out that even a glider made 100% of li-po battery with a perfectly efficient motor would not have enough energy to cross the pacific. You need a fuel with a higher energy density.

Explain me please, what do you mean - climb 100 km?

As I wrote in the post:

or realistically, climb 100 km over the whole trip.:)This would mean you would have to start at a height of 100 KMOh, really? You do not mind the lack of atmosphere at such a height?