Saw this article over on the solarpunk subreddit and wanted to bring it over here with my own opinion attached.
For being a near-zero way to travel in the air it's solar, but the reasons the author criticizes solar-electric propelled airships make it punk. The issues pointed out by the author - slow travel time, lower passenger counts, and windows of time for viable travel, a need for sleepers - could also be seen as its strengths.
For one, slow travel time and lower passenger counts make it a lot easier to meet and connect with strangers with little social risk. They also wouldn't need sleepers. With tight spaces like that, they're less comfortable than economy. My wife and I took a long distance train here in the U.S. (which has its own issues), but we loved the social interaction and actually preferred our economy seats over the sleepers. Two years later, we still like to chat about some of the folks we met and speculate on how they're doing.
The long transit time and specific travel windows would force people to rethink how badly they actually wanted to travel overseas and consider a more local scope. If that's not solarpunk...
I like this idea, the views could be fantastic. The article mentions the problem of prevailing winds - so plan circular trips following the trade winds, as sailing ships used to do. For example, from Spain to the Carribbean, up the coast, back further north (recall - global empires were run without plane-speed, people traveled the world and had interesting lives). Complement the network with sleeper trains overland where practical - for example train down the african coast, down brazilian coast, airship to cross narrowest gap). 48 hours transatlantic, that's nothing compared to a week or more on trans-siberian (although a modern tgv could do Paris-Shanghai in about 48 hrs - if political will instead of obstacles).
Side thought - is there an issue regarding supply of Helium (or energy cost to separate it ...?) if scaling this up?
Great connection to old maritime practices. I wonder if by following those routes at altitude could lead to a transatlantic of less than 48 hours? I imagine a big derigible with sails like pectoral fins and a dorsal and tail fin to steer in addition to solar propulsion.
I agree that supplementing with passenger rail is a must, especially to get from terminal to terminal. What you said makes me think of airport terminals, but they're countries away instead of a mile away. However, I do wonder about the impact on fauna that high-speed rail would has while cutting across continents, and if the airships are a way to skip that issue entirely.
As far helium...iirc, helium on Earth is a byproduct of the radioactive decay of certain elements. There definitely would be ecological consequences of helium "mining", if we were to source from the ground as is typical. Perhaps a breeder reactor could be built to produce in a way more cost effective (not monetarily). Another thought is an interplanetary drone that slurps up atmosphere from the gas giants and tows it back here. Keep the helium collection and corresponding pollution off planet (does this even work in a solar punk world)?
I like the reactor idea. It'd also be a huge boon for the medical field, since helium is necessary for some devices and is currently a limited resource.
There's also the option to just use hydrogen, since you can produce it with electricity and water. Hydrogen gets better lift, and doesn't require petroleum-style drilling. It's flammable, as we saw in the past, but with modern engineering, modern materials, non-conductive pressure vessels, emergency release valves, no ignition sources or sparks in proximity, it seems like it could be done pretty safely. Modern aviation has a lot of problems but it is, I think, admirably safety-focussed, in everything from engineering to operation. I think solarpunk is very much about picking and choosing which parts of our society to keep and which to reexamine to see if they can be done better. Today's aviation safety seems very much worth keeping to me - I think they could find ways to do hydrogen airships safely.
I suspect the impact of train tracks on wildlife would be less than the current highway system, but could also be mitigated via animal overpasses and by raising the tracks on bridges or over tunnels.
Except those doors and engines on the 737 MAX. I've always thought hydrogen could be made to work in the 21st century. It's been 100-years... surely something must be better than doped cotton.
To make the most of the wind they'd need a flexible route adapting to the weather forecast (about 5 days in advance), a deal with rail companies to complete journeys along coasts would help make that doable.
Indeed the fences along railways are an issue, but likewise for big roads, eco-bridges with trees can help (there are examples eg in netherlands iirc).
An interplanetary drone to harvest gas for gentle wind-driven balloons back on earth, interesting combination of tech... but first priority I guess would be to keep the He on our planet (avoid leaks -> lost due to escape velocity).