Hydrogen instead of helium is clearly the elephant in the room.
Helium is expensive, limited, and not easily produced, whereas hydrogen is readily available almost anywhere, has no quantitative limits, and provides far superior lift than helium. Of course, hydrogen is extremely flammable and explosive. If there was a way to minimize or completely mitigate this problem then airships would certainly become more viable than they currently are. The article mentions the use of fire-retardant materials as part of its covering. Perhaps this in combination with tens of thousands of isolated gas "sacs" and an outer helium buffer (To isolate the hydrogen from external heat sources, laser-based weapons, static electricity, etc.) could make hydrogen a viable choice?
The bigger problem with hydrogen is making a container it doesn't escape so much faster than Helium as to negate the extra lift advantage.
You can let it leak out, but then you need to carry extra compressed gas above what is already needed for the same issue with helium.
You can build a tighter, multi-layered envelope, but then you're adding weight and quickly negate the extra lift. This is the category your tens of thousands of sacs idea falls in. The problem there is that you are massively increasing the surface area through which the hydrogen can slip out. You have to keep in mind, to a single hydrogen atom, everything we consider "solid" looks more like a fishing net for catching a whale. Our best designs so far usually involve layering and offsetting those nets so as to at least slow the atoms down as they path through the mesh.
You can regenerate hydrogen in flight by (1) condensing water from the air and (2) electrolyzing it. It's so much cheaper and more replenishable than helium that it allows much more flexibility and, ultimately, flight safety, because it can be vented in an overpressure emergency without any hesitation.
I've thought about that one off and on for a while too. Maybe something like an thin wire electromagnetic mesh as the inner layer of the envelope but I'm guessing no one has tried that at scale because the math says no.
Most likely you either have to pump a lot of power through the mesh to get field coverage enough to reliably bounce atoms away from the skin or you have to make the wire mesh so dense that you've basically got a layer of copper as your envelope and are therefore far too heavy to lift off.
It seems like too obvious an option to have simply been missed over the decades.
Still, I have to wonder if someone will invent a way to coat a string of fabric in like 1nm thick copper film. Or maybe graphene will save this idea too.
The realworld differences are slighter than many think, on the order of 20% more lift. The mass of the h/he isn't a significant factor compared to that of the displaced air. And hydrogen is harder to contain, which further limits available lift.
Another less-discussed option is hot air/helium combos, which at large sizes have some distinct advantages.
If you're set up to replace the hydrogen as it escapes then your lifting gas is a fuel you have to buy for every flight in addition to the fuel for your engines and now you're paying an energy tax to haul fuel and lifting gas in addition to cargo. This makes the entire setup an even worse competitor against planes, trucks, and ships.
Many of the ideas we all come up with for airships technically will work and the fact that we keep thinking of these things over and over again through the years speaks to how fascinating the concept of an airship is; however, we've never had a problem making an airship that works. That's the easy part. Making one that anyone would want to use for everyday transport is the hard problem.
An added advantage of using that approach is that as you drop off cargo (or use up food, water and fuel supplies for multi-day passenger trips) you can siphon off some of those cells to power the propulsion motors and thereby increase your effective range.
Indeed. Or you could arrange for waste (water, effluent, waste food) to be dropped down over a pre-selected area for ground crews to pick up). In other words something like thick mylar bags dropped via drogue chutes as the journey progressed with replacement mylar bags (or similar) carried on board. Just pure spit-balling a day after your reply but a mid-point replenishing stage for food and water (for the passenger flights) would make sense especially for something like an 'Across America' flights across the US diagonal from the Atlantic North-East side to Pacific South West side (eg depart Boston destination San Diego or New York to Los Angeles).
North to South because the air would go from colder to warmer rather than from warm air to colder air if done in the opposite direction and the reasons for a diagonal course is because it would cover a lot more 'interesting sights to see from the air' for a multi-day 'air cruise' type cruise (best way to explain that is a literal air-cruise as in a sea-cruise).
For a passenger trip it would have to be an extremely HNV costing (passenger cost/ticket price paid * weight able to be carried) but do-able for say 4 - 7 passengers but Cargo would be the way to go for the bread-and-butter stuff because A) The weights and destinations are pre-known and optimised and B) Going on a diagonal route would beat road and rail delivery speeds and provide some financing to the back-haul of getting the (now empty) air-ships back to the departure point.
[Edit To Update]: Ughh! you can tell I'm not a pilot because cold air is better than hot air in terms of aircraft lifting capacities so South to North would be better and maybe a change of route from Miami to Seattle would also work out ok in terms of shipping ports that intersect with cruise ship ports.
[Double Edit, Sorry]: On second thoughts, North to South for passengers and South To North for cargo is better because cargo is low margin so would need the greater lifting capacity. Or not.... Like I said, pure spit-balling!
Is there a possible future in which lowered cost to orbit and helium scarcity makes it economically viable to harvest helium in giant sacs in space, and then use “gas stations” floating in the upper atmosphere at different buoyancies to shuttle it down to airships?
I have no idea how many problems there are with that, or how diffuse helium is/how hard it would be to harvest from space, but floating airship stations like Bespin would be awesome.
They buried the helium bit! I really had to dig for confirmation that they weren't going to give hydrogen another go, what with the constant comparisons to Hindenburg throughout.
Helium is expensive, limited, and not easily produced, whereas hydrogen is readily available almost anywhere, has no quantitative limits, and provides far superior lift than helium. Of course, hydrogen is extremely flammable and explosive. If there was a way to minimize or completely mitigate this problem then airships would certainly become more viable than they currently are. The article mentions the use of fire-retardant materials as part of its covering. Perhaps this in combination with tens of thousands of isolated gas "sacs" and an outer helium buffer (To isolate the hydrogen from external heat sources, laser-based weapons, static electricity, etc.) could make hydrogen a viable choice?