3 ms·
The numbers don't work for hot air. You just can't get the lift.
by gozur88 9y ago
The numbers don't work for hot air. You just can't get the lift.
- Retric 9y agoIt's altitude and temperature dependent. 100 °C Which is normal hot air balloon temperature. If the outside temp is 27c that's 1-(300/370) or 19% lighter than air vs heliums 1-1/14 = 93% lighter than air. But you lift increases significantly with temperature. The downside is you end up spending fuel to add heat. But hot air balloons also have terrible insulation. Further volume has great scaling if you save 93% with hydrogen having 4x the volume means being ~20% lighter than air provides the same lift. Now yes scaling the airframe adds weight and drag as does the fuel to provide all that hot air. But you can also significantly past 100c before you encounter massive issues.