In my world lives a society with ancient technology. By ancient technology, I mean ancient roman-like tech, with full access to ancient greek-like knowledge (like the antikythera or Archimedes' war machines).
Now, I would like this society to develop a kind of military zeppelin, and I was wondering if it was possible.
The first hot air balloons were small and meant to be manned only by one person, or just a few persons. They would be made of paper sewn with cotton (and I know, that paper per se was not ancient roman tech, but it was ancient chinese tech, and it is not difficult for an ancient people to produce paper, so I'll handwave on this one).
However, I do not know if it is possible to build a zeppelin with paper. Or if they could make the balloon with a kind of fabric that would be accessible for a not-so-modern-people and still air-tight.
Other thing we need to consider is propulsion. Maybe these people could have perfected an engine with the same principle of Heron's aeolipile... but would it be sufficient to move a zeppelin? Or could we use another method of propulsion?
All these things considered, the zeppelin I'm trying to create may not be as large as the zeppelins used on WW1... however, my questions are these:
Would it be possible for such an ancient people to produce zeppelins? And if so, how large could they be while retaining function?
Note: If the problem is costs, remember that my people runs an empire with the same power and strength as Rome's. They would blow off cost-effectiveness just to have some war-machines (even just three or four) that would impose respect over their less advanced neighbors/tributaries