SolarStratos

[Nibb31]

3 hours ago, kurja said:

...A balloon filled with vacuum would be buoyant in vacuum? Maybe not ,)

There's no such thing as filling something with vacuum.

A vacuum balloon can only have zero pressure inside with positive pressure outside. No existing material can be strong enough to maintain its structure with a pressure differential, while being light enough to provide bouyancy.

Edited December 14, 2016 by Nibb31

[magnemoe]

1 hour ago, Nibb31 said:

There's no such thing as filling something with vacuum.

No existing material can be strong enough to maintain its shape with zero pressure inside, while being light enough to provide bouyancy.

Even if it could it would not only have to be lighter than the lifting gas + the thin balloon skin, but also cheaper to build and operate. 
Note that high attitude balloons are disposable. 

[kurja]

9 hours ago, Darnok said:

Not in vacuum, but in tin atmosphere, above 40km.

I intended to respond to flight at karman line, my mistake as you can see, but anyway buoancy should be much greater if in a tin atmosphere ,)

8 hours ago, Nibb31 said:

There's no such thing as filling something with vacuum.

Semantics.

Edited December 14, 2016 by kurja