Want To Pilot The Solar Impulse Airplane? Check This Out!

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Originally published on 1Sun4All.

While we wait to cheer on the adventurous pilots of Solar Impulse 2, Bertrand Piccard and André Borschberg, to cross the Pacific Ocean, we can virtually fly the solar-powered aircraft with a free web-based flight simulator for Solar Impulse, in real meteorological conditions. This news was just released by solartakeoff.com and is pretty technical, so I’ve included all of their information. I hope those of you who are pilots have an opportunity to “Fly with the wind and the stars …”

Everyone can pilot Solar Impulse around the World

A flight simulator for solar airplanes was released by solartakeoff.com. For now it focuses on Solar Impulse (SI) and its Round-The-World Tour (RTW). Any aviation fan, fond of green technologies or internet gamer may circumnavigate the Earth with SI, in real time, for free. A computer and an Internet connection suffice.

To achieve his project, Sandro Buss, PhD of the Institute for Atmosphere and Climate Science (IAC) at ETHZ could count on the help of computer science students of a professional school in Switzerland: the CPNV (Centre professionnel du Nord Vaudois), under the supervision of Yann Saison. Their expertise in meteorology, physics, aeronautics and computer science allowed to achieve this Internet game, after three years of developments.

Solar Impulse Chongqing-Nanjing
This realization not only allows to participate to SI’s achievements, but to become its own hero. Unlike the real world, virtual pilots may leave their cockpit to have a walk, eat some meal, sleep for a while… between two adjustments of their airplane’s trajectories. Especially when knowing that SI as well as this unofficial simulator do not travel much faster than a car.

“Historical” and “real-time” flights 

Two types of races may be chosen on solartakeoff.com. First it offers to relive the 12 flights undertaken by the HB-SIA in 2012 and 2013 – the historical flights. In the former year, SI flew in 7 legs from Switzerland to Morocco and back. The next year SI crossed the USA in 5 legs. Solar Takeoff allows the pilot to fly any of those legs with the solar radiation and meteorological conditions that prevailed at the time of the flight. One purpose of these revivals is to get prepared to the subsequent real-time games.

As a second choice, from the 9th of March (i.e. since the HB-Si2 took off from Abu Dhabi to Muscat in its first RTW leg), virtual pilots can participate to the adventure, with the latest weather forecasts, in real-time. The goal of the two types of games: be the first to arrive at destination. Therefore, relief must be avoided, winds mastered at several altitudes and the Sun looked after, for the battery load to be managed.

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Even if these two airplane prototypes slightly differ in their aeronautical specifications, the piloting principles are the same. In a refined cockpit design, the heading and the pitch of the air-vehicle must be chosen; so for the power load of the sun-driven motors, as a function of the batteries payload. Doing so, the pilot should avoid mountains, opposite winds and clouds, as those prevent from a rapid loading of the batteries.


Whatever purpose one follows, being it to dream as Icare, plan a route in three dimensions, discover some fundamentals of aeronautics or simply to challenge one’s friends, anyone can participate. A connected computer and an obvious interest in renewable energies is sufficient to join the races. The more players there are, the more interesting the game. Good luck, on the wings of the Sun!

Box 1: High resolution meteorology

For the historical races, Solar Takeoff makes use of the freely available NCEP (National Center for Environmental Prediction) analysis and of its latest forecast for the real-time simulations, both available every three hours and the latter updated four times a day. Concretely, the three wind components and the temperature field (to calculate air’s density, e.g.) are first interpolated from pressure to as much as twenty flight levels, covering the vertical range from the surface to the maximum flight altitude.

Furthermore, the cloud-cover on three vertical layers is used for a detailed calculation of the solar radiation falling on the photovoltaic panels covering the airplane. A module then distributes this energy – the fuel for solar devices – to the four propellers or to load the batteries.

Box 2: Simple but realistic aeronautics

Several simplifying assumptions were made to the full seven degrees-of-freedom physical differential equations, as representing the aircraft as a point mass, carried by the winds. It results in simplified aircraft flight controls, namely the three mentioned commands, which are the horizontal and vertical orientation, as well as the power given to the motors. The model airplane may change its horizontal direction with no restrictions or “banking”.

Box 3: An innovating visualization

The amount of data is impressive: with a resolution of 1° x 1° for the real-time flights (0.5° x 0.5° in a limited area for the historical flights), every meteorological field at any instant represented by 360 x 180 x 20 points. Multiplied with five fields and about 15 forecast times, the visualization gives tens of millions of figures.

It is one thing to compute the aircraft’s trajectory and its battery evolution with those data, but it’s another one to visualize them in a comprehensive manner. Solar Takeoff makes use of a novel pseudo-4D approach representing the data on three sections of the atmosphere: longitude-latitude at fixed height, latitude-altitude along a meridian and longitude-altitude along a parallel. A sophisticated technology allows to slide these horizontal and the vertical cross-sections in order to visualize every nook of the atmosphere. Then, forecast buttons allow the visualization of oncoming conditions.

A combination of factors put the Solar Impulse flight of UTC 25 May from #Nanjing to #Hawaii at risk!

Solar Impulse

Join the Solar Impulse Movement: FutureIsClean.org #FutureIsClean

Would you like to meet the Solar Impulse 2 team? Check out the new website team page!

Image Credit: Solar Impulse | Cartoon Credit: Martin Saive via Solar Impulse 

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Amber Archangel

-- I am an artist, painter, writer, interior designer, graphic designer, and constant student of many studies. Living with respect for the environment close at hand, the food chain, natural remedies for healing the earth, people and animals is a life-long expression and commitment. As half of a home-building team, I helped design and build harmonious, sustainable and net-zero homes that incorporate clean air systems, passive and active solar energy as well as rainwater collection systems. Private aviation stirs a special appeal, I would love to fly in the solar airplane and install a wind turbine in my yard. I am a peace-loving, courageous soul, and I am passionate about contributing to the clean energy revolution. I formerly designed and managed a clean energy website, 1Sun4All.com.

Amber Archangel has 195 posts and counting. See all posts by Amber Archangel