Imagine you have any kind of conditions for the world, any time period — assuming airships are working on laws of physics (no steampunkish "deus ex machina" garbage), what would make an abundance of airships or balloons actually make sense?
A zombie apocalypse!
No, wait! I'm not kidding. That would be a perfect opportunity to bring back lighter-than-air transportation. After all,... the vessels are lighter than air.
If you have an army of staggering undead rampaging around on the earth below you, wouldn't you want your vehicle to remain airborne even if it runs out of gas?
It uses less fuel than planes and other air transportation, and it is faster than trucks, trains and ships as the image from http://www.lockheedmartin.com/ so elegantly explains.
It means the best of two worlds. Cheap and fast. And it is able to get through to difficult terrain.
Also it could be used as a cruise ship for the same reason that people sails around in tallships, they are not as efficient as other cruise ships either in crew or in speed, but they have charm and nostalgia - and some people are willing to pay for that.
Airplanes are economically feasible only because fuel is still relatively cheap. But if fuel gets much more expensive, airships are a good alternative to airplanes: Still faster than ships (and not bound to navigable water bodies), but much less fuel use.
In that expensive-fuel world, airplanes would only be used if a really fast transport is needed (for example emergency aid transport; also the military will certainly continue to use them). For most overseas cargo, ships would continue to be the ideal solution, but passenger transport would likely be done primarily by airship. Over land, airships would basically take over the role airplanes have now, although they would feel the competition from trains and trucks more than airplanes do, as their speed advantage is less.
One advantage of airships over a combination of vehicle and ship is that when part of the transport is over land, and part is over water, expensive transshipping can be avoided, as the airship can fly over land as well as over water. OTOH, the lower fuel consumption and greater capacity of ships may still make the ship more economical in those scenarios.
Most land-based transport is only efficient if it can go almost straight on almost horizontal floor. Trains cannot go through sharp corners at all, and cars are slowed down very much by them. Making cars and trains that can climb steep slopes is expensive, and they will also be slowed down.
There are ways to get this artificially (tunnels and bridges), but if the terrain is sufficiently difficult not only locally, but almost everywhere, using airships may be more economical than building and maintaining lots of tunnels and bridges.
No connected oceans
In our world, all oceans are connected, while landmasses (continents) are often separated by oceans. Now imagine a planet where things are the other way round: All land masses are connected, but the oceans are not. That means ships cannot simply go from one ocean to another. In that world, airships will have a great advantage over ships simply from being able to transport things everywhere.
Easy to get lighter-than-air gas
Let's assume there's a natural source of molecular hydrogen of helium that doesn't require developed technology to use. Alternatively, assume an atmosphere composed of much heavier gases, so that some of the gases that are naturally produced by volcanism fit that bill.
Given natural and obvious availability of light gases, the concept of lighter-than-air travel would likely have been discovered earlier, especially given that its basics are much easier to figure out than the basics of winged flight.
Earlier development of airships means a longer period to establish them before airplanes are invented.
I’ve read about real cases today where gas lifting hybrid vehicles are developed. I think it was in Popular Science, where it was meant for the logging industry. The gas lifting was cheaper to use than the conventional helicopter.
Being hybrid, not lighter than air, it still had sufficient power to maneuver and keep station in real weather conditions (and the overall size is reduced, reducing the wind problem).
So where it can complete is in the sky crane applications, especially where lifting needs to be maintained for long periods of time.
I see companies are still holding high hopes for such ideas.
Here are the main points:
- Safety. The ships have to be seen as mostly safe to have the number of passengers needed to make them economically feasible.
- Cheaper. It can be the fuel, it can be the way it's built, but this method of travel will have to beat out the competition.
- Efficient. It's going to have to do a better job of getting people or cargo from point a to point b. So it either has to be faster or be able to carry more than other methods.
- Marketing. I suggest you look at the advent of mass air travel and the ads for inspiration.
- Beta testing on a smaller scale, AKA war. Before airplanes became a mass transit thing, they were used in war. The funding provided by countries allowed it to be developed so that the tech could be expanded.
You say any time period. We have the tech to do it, but the above covers ANY time period. Look back to when ballooning was first developed--we're talking the late 1700s. If that tech had been funded and developed for war then and developed in the fashion laid out above, planes might not have been developed--or if they were, it would be less advanced because we already had a method of air transportation. I can see planes being developed later to compete with balloons, but if they are already entrenched in society, they will be seen as dangerous to begin with, and might eventually edge out balloons/airships later on.
Let me throw you a link to another question with tech-type answers here on the earliest it could be developed. And the answers on this one covers fuel efficiency. And these answers cover ways to make them better equipped for war.
Airships fell out of use for a variety of reasons:
- Spectacular incidents. The Hindenburg going up in flames is pretty bad publicity for the whole industry, even today that's the kind of thing you think about when someone says "airship".
- Lack of interest from the military. WWI saw the introduction of fixed-wings aircraft on the battlefield and WWII further accelerated the development of planes. Planes could fill every role better: air supremacy, bombing, transportation and reconnaissance.
- Because they were slower than planes, they were discarded for civilian passenger transport as well.
However, if we take a look at existing solutions, we find that:
Boats are great for carrying loads of stuff but they are rather slow. The biggest limitation of boats is of course being boats, i.e. they don't go on land.
Planes are fast which makes them unbeatable for passenger transport.
On the obverse, freight air transport can get pretty expensive, and more importantly, it requires an airstrip. That means long stretch of flat hard surface, and that's the kind of infrastructure that can be prohibitively expensive to maintain for a small, isolated town.
Ground transport requires appropriate roads (for truck) or tracks (for trains). Trucks win over trains for the amount of places they can go to, however they are smaller and slower. In any case, they still require a road. In remote areas, that can be a real problem. Sure, you can build a temporary road (e.g. ice roads), but that's neither cheap nor safer.
Helicopter are just ridiculously expensive. It's just... why would you even?
So airships fit right in the middle of this. Their niche: high-volume transportation for low accessibility areas. Whether you live in northern Canada and they just don't have roads, or in the heart of Africa where there aren't much more roads, an airship can bring you supplies there in a moderate amount of time, for a moderate price, all year-round, in pretty much any weather.
Excessive and wasteful subsidies
A horribly corrupt government that showers the airship industry with ridiculous subsidies would make airships competitive to other forms of transportation because the heads of state are big friends of airship tycoons who would rather boost their own profits than to have people use cheaper and more economical methods of travel/freight.
Or a permanently nostalgic society that sees airships as a part of their culture heavily subsidizes airships to keep a sense of the glory days before airplanes become better options.
Either way, you asked for what would make airships economically viable. You didn't necessarily indicate that making airships economically viable had to be a rational economic decision.
In the wealthy Hamptons communities on Long Island, there is currently a vicious debate between the super-rich hedge fund managers and the like who fly to Manhattan on their noisy helicopters on Monday and back on Friday and the residents who would rather keep things quiet. It drives the locals insane.
The WHOLE POINT of the Hamptons is to make a ton of money elsewhere so you can live in a peaceful, quiet community for the rest of your life, shut out from the humdrum of the big city. It truly is a delightful, peaceful place, until some helicopter slices your quiet day to shreds.
So perhaps the local government levies enormous and punitive taxes on airplanes and helicopters, but airships - because they are quiet and less intrusive - are allowed as an acceptable middle ground between the desires of the community and the needs of the wealthy people who made it what it is, because who wants to drive on the Long Island Expressway during rush hour?
Filling the gaps in the market.
As various other people have mentioned, airships are coming back into fashion.
They have a set of specific advantages over other aircraft.
- VTOL, helicopters can do this, but helicopters are expensive, complicated and need a lot of maintenance.
- Staying airbourne for long periods, this one is a real winner for airships. The Goodyear blimp being the best known example.
- Flying slowly, again helicopters can do this, expensively, noisily and uncomfortably, but there is often a need for aircraft to move slowly and airships are a good fit for that role.
They have certain downsides, lack of speed, power and handling in high winds for example. Often considered the biggest problem hanging round them is the Hindenburg, but there have been a lot of plane crashes since then and it's not so fresh in people's minds.
One idea that comes to mind is keeping the vessel in a (relatively) static area in the sky for long periods. Observatory balloons (e.g weather balloons, guard "tower" balloons) are in everyday use.
This is not a full answer (I agree with all of the above and would like to add), but here's something to look forward to, once we construct some graphene balls:
Basically, a vacuum airship is much more lighter-than-air than known gasses, and it's non-combustible. When the tech to contain a vacuum with a really light weight material that will retain it's shape (and the vacuum) comes to be (I'm thinking graphene containers), we'll have cheap and efficient airships.
And why stop there? This tech can be used to reduce drones's energy requirements, and small carriers (air-cars) can use these as well. You can have platforms/houses/cities in the air, the sky is the limit (pun intended) :-)
Also - check this out: https://www.youtube.com/watch?v=8zO9h_9g2eQ
They make a lot of cheap clean power and are easily transportable.
- Infrastructure (and regulations) which allow airships to dock on mooring masts in the city center, while planes are restricted to airfields on the outskirts. For instance, they need to be free to rain water ballast onto pedestrians.
- Access to cheap helium.
- A clever inventor who finds some tweaks early, like gas engines.
That might give airships their chance until they are replaced by helicopters.
They are economically viable now - the problem is reputation. Everyone has seen the Hindenburg picture, and that is hard for people to deal with. Humans are terrible at risk assessing situations.
For transport of massive items, the only viable options currently are ships, trains, trucks and airships. The first three of those are restricted as to where they can travel (sea, canal, rail and road) so getting something big to an inland wilderness in a cost effective way can only be done by airship!
So... Fix the reputation of large airships (Zeppelin and larger) and the rest falls into place naturally.
I would look at the modern popularity and revival of sailboats for delivering freight as a similar situation. Speed is similar to modern cargo ships, and emissions is zero. I think these two situations is enough for people to explore the possibility of sailing cargo, or in your situation, the revival of air ships.
Blimps are quite fashion nowadays, they can lift heavy payloads and they are indeed "greener" : low fuel consumption, and as the engines don't have to be really powerful they are quieter than common aircraft. In addition to that, their shapes don't redirect the noise to the ground, unlike airliners.
Furthermore, you can easily put electric engines on a blimp, and as they present a big, useless and static surface (unfortunately not flat), adding solar panels to power up those engines is much more realistic than the Solar Impulse model. By doing so, you almost never have to touch the ground.
Finally, the problems are that blimps are not happy when used in bad weather with strong wind or so, and they are really slow compared to other aerial transportation systems. But for limited-access jobs or commercial cruises they could be a great solution. By the way, some companies already trust in lighter-than-air aircraft like the French Flying Whales. So, for a quieter and greener future, blimps could be a part of the solution.
Since airships don't require complicated landing infrastructure and can fly over difficult terrain, they are most useful in areas that have poor accessibility by more conventional modes of transport, such as airplanes, trains or automobiles.
For example, according to this article about the Hybrid Airship from Lockheed Martin and Hybrid Enterprises, about 90% of the mineral resources in Africa are already in use, and the last 10% is not economically viable due to poor access. Enter the superblimp. Since it has nice lifting capabilities and can safely land in a fairly level area of two to three (American?) football fields, it can push at least some facilities to viability.
Blimps would make the most sense in a world where building infrastructure would be prohibitively expensive or difficult.
Redesign and Repurpose.
The classic blimp shape and design is old and stodgy and introduces a major single point of failure. We have lighter, stronger materials and the know how to make something truly remarkable, something sexy, something safe.
The airship should be purpose built. Right now it's one size fits all. Wrong Wrong Wrong. Airships were used because they were the best bet for the technology available. We are way past that. Combine airship and drone technology for remote piloted workhorses or trick it out with the latest tech for the next "big" thing in luxury cruising.
In short, make it sexy, make it safe, make it relevant.
Nothing, really, because of their very low speed and being really big sails. It's also the exact same reason that sailing ships have disappeared.
The thing is that (except in the rare cases of really strong storms) internally powered (air, sea and land) craft go where we want, when we want, no matter what the weather is like. That's why we ditched sailing ships and lighter-than-air craft as soon as technologically feasible. Enthusiasts try to make them viable, but don't succeed because these ships aren't practical.
A high-tech U.S. military blimp designed to detect a missile attack came loose on Wednesday and wreaked havoc as it floated from Maryland into Pennsylvania while dragging more than a mile of cable and knocking out power to thousands.
i don't know what tech level the setting is but assuming it is around current tech
- higher air density makes airships more viable
- you can run them on solar
- they fail in a safer manner
- they require less infrastructure
- availability of lifting gas
- need to beat competition in at least some case
- because (at least some) humans like them
Higher air density/pressure
since an airship works with buoyancy the lift is the mass of the displaced volume, a higher air density reduces the volume required. this does also increase the ease of creating rigid wings airplanes but the added air resistance will make the fly slower than on earth(unless you fly high)
if you have light and efficient solar cells you can use electric driven props/turbines for propulsion. with current solar panels you get quite a lot of power, an airship the size of Hindenburg run on solar gets about the same power as the Hindenburg engines (but only during daytime). the availability of fossil (or similar high energy density fuel) fuel might be a problem for airplanes and other heavier than air vehicles.
a airplane when it fails will fall out of the sky like a stone, an airship on the other hand will slowly lose altitude (unless the lifting gas explodes). during ww1 the airships was hard to shoot down, bullet holes caused them to leak but not enough to down them in a timely fashion, it is even harder if the airship is built with internal compartments within the lifting gas.
planes need landing strip several km long and in quite nice condition, an airship does only need clear space for it self to land, or it can hover in place and load/unload with a crane.
abundance of lifting gas
hydrogen is abundant and the best lifting gas by performance and you can also use it as fuel, but it has the downside that is is very flammable. hydrogen is abundant, it does require some trivial chemistry to extract it from water or other sources. but hindenburg...
helium is very rare on earth since it evaporating into space quite quickly, but it is the next best lifting gas and it is safe... but expensive, today all helium on earth comes from natural gas deposits that has trapped alpha decay(helium).
hot air is also a lifting gas, it is safe and abundant but requires a constant energy input to keep it warm
on earth hydrogen, helium and hot air is the only options since other stuff in not lighter than air, on say Venus our normal air is a potent lifting gas
in order for airships to be commercially viable there can't exist a clearly more viable alternative - airships is probably not a viable option for bulk transport the same way modern airplanes isn't, but in some areas of the world it is the only option. but airships can pull of tricks like hovering a 100t load for precise placement like a crane. - trains will probably win out in bulk transport over land, at least if the terrain is flat enough to run trains on and high enough demand to invest on the infrastructure - cargo ships will win when transporting bulk over water, but it requires a fright harbor in the ends and a continuous stretch of water in between. - road transport is mostly the same as trains
human does all kinds of illogical things for example there might exist a religious rule that says it is a sin to fly like a bird, or that some other people pointed out that is some government policy that benefits airship over other modes of transport.