DW: Up until now, the ISS has been a symbol for worldwide cooperation in space research. That's changed a little bit. There's a lot of tension at the moment between Russia and western powers at the moment over the Ukraine situation. Is the situation in Ukraine on the ground having an effect up there in space?

Jürgen Herholz: I believe so very strongly because the Russians are trying to tease the Americans in different areas -- why not in space? -- but they're keeping to their obligations and that's important to know.

Well, actually, you could then really see it from the positive side. You could say they've agreed to remain on board for the next 9 years rather than saying in 2024 they're going to be stopping their cooperation. They're also going to be sending up some new modules. What do you think are the most interesting?

I don't know if it's a Russian module, but the most interesting one will be a free-flying laboratory, which would be decoupled from the station and would allow experiments under micro-gravity, which is very interesting because the station itself is not really a micro-gravity environment.

What kind of technology could come out of those tests?

Mostly material sciences, crystal growth for interest, which is of very big interest on Earth for developing new materials.

Roscosmos, the Russian space agency, says it wants to decouple its modules in 2024, making them part of a new national space station. Now it looks like a fairly significant portion of the ISS that they're decoupling. How easy is that going to be? Surely, it's not just loosening a couple of screws...

First, I think it's not important if you look at the scale and the overall functionality. In fact, the Russian part initially was the only part that existed before the remaining 90 percent arrived, but they have lost importance because a lot of, for instance, the altitude control now is taken over by the space station and the Americans certainly will have a manned transport by 2020 and so the two questions relating to the Russian part will be less important.

You just mentioned the subject. What about the commercial aspects of possibly the Americans having a new transport system up and running? What about commercial companies doing that? Is that an option, a possibility?

I have an extremely high regard for Elon Musk and his SpaceX. I had the chance to meet him in the United States. He is a great guy and he has a great undertaking with his Falcon and I am sure by 2018 he will be sending people to the space station.

Well, Jürgen Herholz, up at the space station with commercial air flights by 2018, thanks for joining us.

Elon Musk himself would love himself to go to the space station and to Mars. And that is his objective.

(Interview: Derrick Williams)