Solar impulse passes 'point of no return' in Pacific

Transcript

A solar-powered plane crossing the Pacific Ocean has passed the point of no return, in what could be the longest ever solo flight in the history of aviation.

Solar Impulse took off from Nagoya in Japan about 25 hours ago.

It's heading for Hawaii - a non-stop flight that will take five days and five nights to complete.

A spokesperson for the team, Conor Lennon, says it's an extraordinary mission.

CONOR LENNON: It's a flight that's never been done before. And in fact not just solar aviation, we think that once the pilot has made it to Hawaii, and we're confident he will, this will be the longest solo flight for any kind of aviation.

GUYON ESPINER: And you're passed the point of no return now I understand.

CL: Yes, quite some time ago we passed the point of no return. And it was a really difficult moment for us actually. Because we've been working on this for 12 years, this flight, and we've done lots of shorter flights, we've even done a 44 hour flight which was two days and two nights - and that in itself was extraordinary. It's a record breaking flight. But I mean psychologically if you think about it like this, we've got to a point where we know if we turn back the pilot is safe and the plane is safe. If we don't, there's no guarantee. Because we have a lot of days ahead, we can't be sure 100 percent what the weather will do. We've got pretty good modelling tools - but you know, weather is very complicated, we can't be sure. And we've got the risk that it might go wrong. With the hope of course that we get to Hawaii, as I say we are confident we will do, and then we will have created something that has never been seen before. A five day, five night solo flight.

GE: So what challenges would the weather present to a solar powered plane? How does this work?

CL: This is the only solar powered plane that can fly day and night. And theoretically it can go on forever because it has been designed as such that the sun propels the plane along and also recharges the batteries such that it can fly throughout the night and then carry on. That's the theory. And we've tested it as I said on one flight for 44 hours. However in order to create such a plane it has to be very, very light. And being light it is also more susceptible to the elements - turbulence for example, precipitation, heavy clouds. And these are things that we have to avoid - not just for the plane but also for the pilot's health. If it's very turbulent the plane is very difficult to control and it means the pilot can't sleep at all. When there is clear air, calm air, the pilot can sleep in 20 minute stretches.

GE: What an incredible psychological challenge too for the pilot to be flying for such a long time.

CL: We often speak to him about this. What he says is that he takes it moment by moment. It really is carpe diem for him. He's living hour by hour, minute by minute. And he has lots to do. He's not bored. And also he has to exercise. He has just enough space in this four cubic metre cockpit to do yoga exercises, to stretch as well, make sure he doesn't get deep vein thrombosis, and he's a big guy so that could be a big problem, and he's got techniques so he can get into really deep sleeps in these 20 minute rest periods.