Which mechanism initially constrained the operational altitude of early hot air balloons?

💡 Explanation

When ascending, atmospheric pressure decreases, leading to lower oxygen partial pressure, causing hypoxia in the balloonists. Therefore pilot hypoxia was the limit, rather than fabric tearing, burner failure, or rope breakage which would depend on structural or fuel constraints, independent of altitude.

• Which property primarily determined wood selection for 18th-century shipbuilding hull planking?
• Which navigational error increased during trans-Atlantic voyages when chronometers initially drifted after being set?
• During early steam engine development, which limitation caused atmospheric engines to be less efficient than later designs?
• Which optical phenomenon underlies the operation of an Ibn al-Haytham's 'camera obscura' used for astronomical observations?
• Which observational consequence results from atmospheric refraction during astronomical observations at low angles, specifically at sunrise/sunset, with astrolabes?
• Which navigational error rapidly accumulates when a chronometer is abruptly mechanically shocked during a lunar observation?