"So short a time?"
Big Mongolfier hurriedly explained, "Your Highness, this is just a test hot air balloon. In the future, we can make it larger to carry more fuel."
Little Mongolfier softly added on the side, "But that will make the inflation time longer when launching..."
Joseph sighed, "What fuel are you using?"
"A mixture of straw and wool, Your Highness."
Joseph thought no wonder it doesn't fly long, how much heat can burning this stuff produce?
It seems that modern hot air balloons use propane or liquefied natural gas as fuel.
Well, that's impossible right now, let's skip it.
Farther back, it should have been using kerosene...
Currently, France's coal tar industry can refine kerosene, but it's still at the laboratory process stage, with very low output and very high cost.
Joseph finally said helplessly, "Then let's use alcohol for now."
