Reminds me of the line from Snowcrash: "dirigibles that can ship North Dakota all the way to New Zealand for a nickel". It was published in 1992 so I'm assuming there must have been talk even back then about the coming dirigible renaissance.
Cargo airships could be big
331–340 of 385 posts
Re: Cargo airships could be big
#332Earlier quoted context omitted.
I think the key is in the wikipedia article: You only gain 14% lift with a vacuum vs helium. The tradeoff is either: - Build a pressure vessel to withstand the differential to the atmosphere - Let the helium do the pushing from the inside but make the thing 14% bigger I don't see how the vacuum ever wins.
> I don't see how the vacuum ever wins. 3 ways. - Vacuums aren't combustible. - Vacuums can be created without sourcing a gas. - Vacuums allow you adjust buoyancy without requiring you to carry extra gases. The major downside of a vacuum is finding something ridged enough, light enough, and cheap enough to maintain a vacuum.
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Re: Cargo airships could be big
#333I'd like to draw your attention to " killing 35 of the 97 people on board in the inferno. " The Hindenburg had 7 million cubic feet of Hydrogen gas. It was the biggest aircraft disaster of its time. It had such rudimentary technology that the cockpit looked more like a sailing ship than an aircraft[1]. Despite that, well over half the passengers jumped out the windows[2], ran away and survived with few or no injuries…
> (NB. people now want aircraft which can legally be pushed horizontally by hydrogen, but cannot legally be pushed upwards by hydrogen.)
I laughed out loud when I read that, thank you!
Re: Cargo airships could be big
#334Probably a very stupid question, but can someone help me understand the following: once you have airships that have a rigid shell, why isn't using a vacuum better than a lifting gas? Isn't the buoyant force simply the result of displacing some volume of air with something less dense? (i.e. any excess lifting force comes from the fact that the mass of the hydrogen or whatever is less than the mass of the displaced air…
I looked into this a while back, and there's simply no feasible way to construct an airship from known materials that could sustain a vacuum of the necessary volume without being crushed by atmospheric pressure. You can keep reinforcing the vacuum chamber, but by the time it's strong enough, it'll be too heavy for the buoyant forces to lift it.
Instead of additional mass, you could add additional energy.
For example, a small maglev running around the inside of the vacuum sphere would steady outward pressure on that part of the sphere. Add more trains at different angles to even out the forces.
As a bonus, this kind of "active structure" can dynamically vary its structural strength as atmospheric pressure changes with altitude or weather.
See Orbital Rings for more info.
Re: Cargo airships could be big
#335Earlier quoted context omitted.
There is not. The costs of dealing with pressure differentials are extreme, and there are a lot of small thorny issues. For one, if you have a pressure differential, you need to care very much about even the tiniest leaks. A surprising fact about airships is that they don't actually have to be very gas-tight to work just fine. As people found to their surprise in both world wars, you can shoot an airship full of smal…
Yes, if you just shoot a hydrogen airship, not much happened, only after they introduced incendiary rounds, strong damage was done.
No idea why this was downvoted, but in case anyone believed it was imaginary:
Re: Cargo airships could be big
#336Earlier quoted context omitted.
And what are we going to do there? Mine sulphuric acid from the clouds?
Build a second basket for our eggs. There are obviously better baskets than Venus though. I'd sooner choose an orbital habitat.
There is no second basket possible and the idea that there is one is a recipe for disaster
Re: Cargo airships could be big
#337Earlier quoted context omitted.
Twice as fast as a cargo ship is still only 50kph right? And the Jet stream only goes one way and only West to East (in the northern hemisphere) and only at certain latitudes right? So if you're only competing against cargo ships. And you happen to want to head East (only, no returns). And you need to go faster than a ship, but not over 100kph. And you are already at the right latitude and so it your destination. And…
You're exactly right, but perhaps missed that the trade route you're describing is China to Los Angeles, which alone accounts for $132 billion in trade every year, and perhaps that cargo vessels allegedly account for 20-25% of anthropomorphic carbon emissions. Also probably worth pointing out that airships going against the jetstream are still faster than cargo ships which are also going against sea currents. I'll re…
I also find the idea of "they have to land at a airport" pretty murderous for autonomous vehicles. Like no they do not. They can deliver cargo to autonomous barges, which then deliver the cargo slow and steady and reliable to cargo terminals. No autonomous vehicle ever has to touch land..
Re: Cargo airships could be big
#338The airship renaissance is the fusion of transportation world. It's always ten years away. Seriously, I've been hearing about the great promise of modern airships for twenty years. Where are they? Are there any airships operating commercially now outside of niche applications?
No, the airship renaissance was over a decade ago. Cargolifter tried, and failed. From what I heard so, the water and holiday park they built in the ex Cargolifter hangars has to be quite good so.
One thing they struggled with was ballast. If you plan on carrying 100+ metric tons, what do you do once you're done? Suck up the nearest lake maybe and dump it back at base when you load your next cargo? Now this restricts your use cases. Not that many lakes people wanna part with in Africa...
Re: Cargo airships could be big
#339Earlier quoted context omitted.
No, the airship renaissance was over a decade ago. Cargolifter tried, and failed. From what I heard so, the water and holiday park they built in the ex Cargolifter hangars has to be quite good so.
They mostly had trouble with landings and takeoffs. Cargo ships could have specialized cranes load and unload cargo while airborne.
That would be very tricky with conventional airships (and even trickier with hybrid ones). You would need to keep the system rougly at the density of air as you are tensioning the crane hoists. Probably by shedding ballast at the same rate you are appying tension on the lifting ropes. While the ship is blown about. And any cable failure would result in the airship violently jolting into the sky.
With hybrid airship this is even trickier, since they relly on airspeed to generate some portion of their full lift.
Re: Cargo airships could be big
#340Why not simply put a lot more stuff on trains and accept that it takes a little more time to Amazon to deliver your new gadget? I'm always baffled by the lack of analysis of a "let's just slow down" scenario.