On Monday, September 11, 2017 at 10:20:09 PM UTC+3, Duster wrote:
Landed now. Curious; on Sept 3rd when they broke the altitude record by going above 52K' they descended to return even though it appeared they were still in strong lift and could have gone higher. Out of battery power, air (for pressurization), O2 perhaps? Anyone know for sure?

Yes, back down at 25 knots descent rate most of the way! This was the second highest flight for them so far this year. Seems to be hard to get above 35k.

And I agree, they were still climbing pretty well at 52K last week so I don't know why they stopped. Breaking the record was of course a big thing, but why not break it by as much as possible? Who knows when the next suitable day will be. I noticed the battery was down to 30-something percent, while air and O2 were still at maybe 60%. I was surprised at the disparity, and it hasn't happened again.