Yes, but they need to be quite big, just like the wing needs to be big. I'm not saying a prop can't get you that high, but how fast you get there is another matter entirely.I wasn’t comparing Celera to Pathfinder. I was only saying that props are still capable above 60,000 feet.
Excuse me sir, but you seem like a kind of combative fellow who really doesn't know much to be honest.Claiming the opposite shows that you haven't looked into it deeply enough.
Didn't Helios go beyond 120 000 ft ?Are you making that statement for all propeller driven aircraft, or just the Celera? Though unmanned, Paul Macready’s Aerovironment had the Solar Pathfinder Plus that could fly over 80,000 feet and made three hour flights that sustained over 70,000 feet, all with propellers.