The objective of Solar Impulse is to, of course, to fly around the world with a solar-powered airplane, an airplane fully autonomous, so using only solar power to propel itself from takeoff to landing.

And to achieve that, we have to be able to fly day and night. So we need an airplane which is very light. That's the size of an Airbus, but that's the weight of a mid-size car. This flight around the world will be done in different steps, from one continent to the next.

Each leg will last up to five days and five nights, with only one pilot on board of the aircraft. The airplane which we are testing currently is the prototype airplane, with which we want to demonstrate we can fly day and night. At Solar Impulse, we are doing the so-called ground vibration tests with the help of DLR.

Our purpose, of course, is to reduce any risk that we may have in different potential flatter cases. To be able to assess this, we had to make the sophisticated vibration test. First time we did it with the basic structure of the airplane, and now with the entire airplane.

And we needed a very experienced team for that, and DLR for us was the best solution. We'll do now parameters, identifications, which will be very useful to improve the quality of our flight simulator, and potentially also to help us to develop the autopilots for the second airplane.

So there are different programmes which are going to be started very soon with the entire DLR group.

We at the DLR Institute of Aeroelasticity in Göttingen are here for ground vibration tests, and we are responsible for this ground vibration test of this aircraft. DLR is also involved in other aspects of the project. Development of the propeller, for example, was done at the DLR Institute of Aerodynamics and Flow Technology in Braunschweig.

And another DLR facility in Braunschweig, the Institute of Flight Systems, is due to take part in flight tests of the aircraft. The special thing here is of course the lightweight construction that really pushes the limits of what's possible.

This is a rib that will be glued to the wing's spar boxes and form part of the airfoil. Here you can see the lightweight construction of this structure in detail. These components weigh almost nothing. At best you can weigh them on a postal scale. Of course the extremely light construction also means that with just the smallest of forces,

we are able to generate clearly visible oscillation amplitudes. As an example, if we apply forces in the range of two to three newtons, or the equivalent of about two to three hundred grams, we have basic wing bending. And we've produced clear oscillation amplitudes that are visible with a naked eye.

The shaker works something like a hi-fi loudspeaker, as there's also a magnetic coil inside this vibration generator. In this case, we use magnetic force to introduce vibrations directly into the structure.

What we see here are the sensors that we use to measure the oscillations of the aircraft's structure.

We've distributed around 160 of them all over the aircraft. The majority of them are located on the wings, including the ailerons for control, as well as the tail unit, the fuselage and the engines as well. These sensors have been placed here and are fastened to the structure. We had to separate the bundles of cables from the structure

in order to ensure that their weight didn't influence the vibration of the aircraft. Of course, I'm happy that I can continue to support such an ambitious project with my expertise and by overseeing this ground vibration test.

The idea of flying around the world without using fossil energy is simply magnificent. We are not only developing an airplane, but above all, we hope to develop a symbol

of what really can be done with the existing technologies. We'd like to demonstrate that we can save energy, and we believe this is a very good example, as we will fly an airplane of the size of an Airbus, but using only the power of small motorcycles. And if we can save energy in the air, we can certainly save energy in many applications,

on the ground, in our home, with our cars, which is the best way to reduce the dependency of fossil energy.