Cargo Airships Are Happening

The (biggest) problem that keeps airships from practical use is that they are huge sails. Big sails mean even small amounts of wind can be powerful forces acting on the airship. In the air a big push from the wind might be safely managed, but if you're near anything solid such as the ground, you can get smashed to bits.

To safely operate a suitably efficient (large) airship, we'd need both huge specialized docks with extremely strong mooring structures to keep wind from smashing the airship into whatever is near it, and a system (such as a 3-axis propulsion system on the airship) that is capable of counteracting wind force acting on the airship when it's near the ground or other solid objects and not docked.

Despite the many attractive advantages of airships, there's yet been anything like a good solution to this problem. There are other challenges too (what do you do when you drop off your cargo and the airship wants to shoot up into the air? Vent gas? Rapidly compress your gas?), this is just the biggest.

> There are other challenges too (what do you do when you drop off your cargo and the airship wants to shoot up into the air? Vent gas? Rapidly compress your gas?)

Not to detract from your overall point, but you do the same thing you do when burning fuel while cruising: Add ballast.

Yes, but how do you add ballast to an airship while it is underway? Simple: condense water out of the exhaust like the zeppelins did.

> Simple: condense water out of the exhaust like the zeppelins did.

Citation? Would not the condenser need to burn fuel, thus lightening the ship?

You are carrying fuel and using oxygen from the atmosphere to combust it. When it's hot, it's a gas. By simply cooling it and recovering most of it, you are potentially left with more mass than you started off with... and Oxygen is relatively heavy.

The article describes electric airships

The GP asked about burning fuel. But in the case of electric airships, you can run an electric condenser, extracting atmospheric water vapor.

This idea of extracting water from air keeps coming back, but every time someone tries it, they learn of the same thermodynamic limits. It is extremely energy-intensive to extract water from the air, and it only really works if the climate is humid enough that there is water in the air to extract. This is exactly what a dehumidifier does, and the off-the-shelf version you can buy at home depot is no more than 5-10x worse than the thermodynamic limits - those generate a pitiful amount of water for a lot of energy intake.