That is absolutely awesome. Well done to everyone in the team. most 'multi rotor copters' are limited to around 20 minutes flight time. As stated in the article several of these hovering over a disaster area looking for heat signatures and human movement would help to identify injured people. they would also be able to give the ground commander a great overall view.
The article states that it could fly at night with a battery. The reason it can fly (in Singapore directly on the tropics), is that it is light and has a relatively large area of cells. For it to fly at night it would need batteries which would immediately increase its weight so it's flight time would be just as short a time as conventional quadrocopters.
Brian M
Absolutely daft and dangerous not to have any battery backup. If sun power is lost/reduced then that is one drone heading for the ground totally out of control!
The use of a LiPo should be mandatory in their design, only has to be sufficient to keep the control system going and with enough lift capacity to gently return the drone to ground automatically.
'a student team from Queen Mary University of London claimed to have built one five years ago.'
Yep so have many hobbyists as well!

Payload weight?
Hmmmm, that's quite a surface area and small motors, one gust of wind and it's in the next county!
You know what? A helium balloon can fly almost indefinitely, with or without sun light, day and night. You only need a tether.
Too wobbly for my liking.
Douglas Bennett Rogers
The solar collector should double as the lift surface as it does in other solar aircraft. Maybe its control system could use the solar panels that way. It could use the rotors as generators while descending or in thermals.
Bob Stuart
Agreed - the solar cells should be on big, slow rotors, but it will be tricky getting it strong enough to fly in brisk, turbulent winds.
These guys should bring this flying machine to Alaska where the sun doesn’t set for a couple of months. Also, could anyone explain why the square solar cells have cropped corners? Surely this would decrease sunlight capture by a few percent?
I like the idea above about the cells being in an airfoil shape because it could glide on thermals too.