Aviation

[morganism]

Andrew Côté   @Andercot    Sep 26


How Airships could unlock a $650 billion dollar carbon-free long-distance freight market

The engineering scaling laws behind airships are incredibly compelling and could revolutionize transoceanic freight. But, they're unpopular for the wrong reasons.

Here's the econo-physics of our long-lost Zeppelin heritage:

Summary:
- Physics demands airships are big and cruise at moderate speeds of ~100km/hr
- Economics demands airships use hydrogen as lifting gas, target long-haul freight, fill a niche between ocean freighters and air freight in cost / speed.
- Airships using the jet-stream would be 4-5x faster than ocean freight and save 3,375 tons of CO2 on a round-the-trip journey
- Airship renaissance has already begun - both national governments and tech titans like Sergey Brin are developing new designs.

The Airship Cargo niche is providing freight at 1/2 to 1/4 the cost of air freight while 4-5x faster than ocean-going freighters, for far less CO2 impact.

~~ Physical Scaling Laws ~~
The cargo-lifting capacity of an airship scales with its volume, the drag scales with the frontal cross-sectional area. This means bigger is better - the larger the airship, the more efficient it is at carrying cargo.

The drag force is proportional to velocity squared at typical airship speeds, and since power = force * velocity, the power-plant requirement depends on the velocity cubed - limiting the realistic speeds for airship freight.

For every doubling in size, you 8x the cargo carrying capacity and only 4x the drag. So, big is better, slow is better.

Net net: Optimized airship cargo haulers will be massive and travel at moderate speeds ~100km/hr

Take for example a 500-ton cargo airship design study (elidourado.com/p/cargo-airsh…). Here are the specs:
Length: 388 meters
Diameter: 78 meters
Volume, 1,130,000 cubic meters
Gross weight: 1,000,000 kilograms
Cruise shaft power: 3.4 megawatts

This is almost as long as the largest freighter in the world. An appropriate gondola would be the airbus A380, the current-largest airplane in the world.

Adding 60% in payload only increases the length by 15%, netting a 21% improvement in efficiency in fuel.

For intuition, both ocean freighters and airships are displacement vehicles - they carry cargo by displacing a fluid, which provides buoyancy. Water is about 1000 times denser than air, therefore for a given size, an ocean-going freighter can carry about 1000x the freight of an airship. Airships, however, travel about 3x faster.

~~ Economics of Freight ~~
Airships get more cost-efficient the larger they get - but they have to compete with existing freight options. Here's the three most popular forms of freight, priced by what it takes to move one ton a distance of one kilometer domestically:

Air freight: 83 cents / ton-km
Trucking :   11 cents / ton-km
Ocean freight:  2 cents / ton-km

Within the US Trucks haul the vast majority of freight and generate the majority of cargo revenue - they are in the goldilocks zone of time and cost.

Internationally, prices for air and ocean freight are about half (~40 cents and 1 cents per ton-km), and the split is more even in terms of revenue.

Trucks exist in the 'goldilocks zone'  of freight - it takes a couple days, isn't bound to a port or airport, and is medium-cost. Airships would be the trucks of international long-distance freight - medium speed, medium cost, not rely on ports - and could capture a massive part of the market:

If airships captured half of the 13-trillion ton-kms currently served by container ships at 10-cents per ton-km, thats $650 billion in annual revenue.

If you assume each airship carries 500 tons, cruises at 90 km/hr, and is used 2/3rds of the time, you need a fleet of 25,000 airships to the 6.5 trillion ton-kms of annual freight. Thats about the same number of airliners in operation today.

~~ The Case for Hydrogen ~~
It's currently illegal to use hydrogen as a lifting gas for aviation in the United States. Why? The Hindenburg. However, hydrogen is less dense than helium and so provides 8% more gross lift - it's also about 70x cheaper.

Helium is relatively expensive and in scarce supply, and has a wildly fluctuating price. MRI machines consume about half of helium production worldwide. Hydrogen, on the other hand, is cheap and abundant.

500-ton airship filling cost:
Helium: $8 million USD
Hydrogen: $100 thousand USD

Global helium production is only 160 million cubic meters per year - enough for 140 of our 500-ton cargo airships.

An advantage of using hydrogen as your lifting gas is that it can also be used as your propulsion fuel. Since the airship is gigantic and can ride above most weather, tiling the exterior surface in solar panels can also provide on-ship power to separate hydrogen from moisture collecting from the atmosphere - unlimited mid-air refueling.

~~ Airship Unit Economics ~~
Assume we now have 500-ton cargo airships that can do 260 million ton-km/year, at 10 cents/ton-km, for an annual revenue of $26 million / airship. The fuel cost would be around $4 million, leaving $22 million/year for other costs like support, maintenance, and profit.

A trade-study on a much smaller capacity airship of 125 tons suggests annual fixed costs of ~$15m per year and variable costs of $7.5m per year - eating up our $22m budget on a smaller ship [2]. But, size is our friend - go bigger until you hit profitability.

If a 500-ton cargo airship could be manufactured for ~$100 million, it starts to get feasible. If you can charge more than 10-cents per ton-km, perhaps 20-cents per ton-km - suddenly you've hit airship profitability.

~~ Wind-Hacking ~~
The fuel costs for a 125-ton airship could well be over $6m per year [2] (and via scaling law of mass^2/3, net $15m per year for our 500-ton airship). This is a substantial fraction of our freight revenue, it'll be a lot cheaper and a lot easier if your massive airships can just ride the natural wind currents in the Earth's atmosphere.

There are two counter-rotating jet streams high in the atmosphere, created via convection currents and the Earth's rotation. They exist at altitudes of around 10km and maintain average wind-speeds of 135 km/hr.

Scientists have analyzed the jet stream for airship travel and the numbers are compelling [3]. Airships in the jet stream could circumnavigate the world in ~13 days - currently it takes ocean-going freighters 40 - 50 days to achieve the same. Freighters also burn about 225 tons of bunker fuel per day.

Airships could circumnavigate the planet 4-5x faster than ocean-going freighters while saving 1,1250 tons of bunker oil from being burned.

~~ Zeppelin Competitive Landscape ~~
There's currently a few projects that recognize the inherently appealing physics and economics of airships.

- LTA research in California backed by Sergey Bring and is developing the 400-ft long Pathfinder 1
- Flying Whales, supported by both Canadian and French governments, is testing a 650-foot long LCA60T dirgible.
- Hybrid Air Vehicle in the UK is readying production of its Airland 10 blimp, with 10 tons of cargo capacity,

These projects use materials like kevlar, carbon fiber, and new alloys that are lighter and more performant and our ability to safely use hydrogen and detect leaks is far beyond what was available in the days of the Zeppelin. Faster, better, stronger.

They just need to be 50x bigger.

~~ The Market for Zeppelin Cruises ~~
A 2nd-order win in developing airships for cargo is to re-learn our airship manufacturing and deployment capabilities.

I dream of a day we can book cruise tickets on an airship that takes a 2 week tour of the Andes, or Rockies, or Grand Canyon - to float high above the Mongolian Steppes, to see the curvature of the Earth at sunrise before stopping off at a remote Wadi in the Sahara for lunch.

Airships would unlock a zero-impact means of exploring remote areas of the Earth from a unique high vantage point. Unfettered by roads, ports, tourists could see remote wilderness sanctuaries without ever stepping foot in them.

~~ Further reading ~~
[1] elidourado.com/p/cargo-airsh…
[2] isopolar.com/airship-costs-f…
[3] sciencedirect.com/science/ar…

@elidourado's blog post is excellent reading on this topic and I suggest giving him a follow for more atoms-first optimism.

https://nitter.poast.org/Andercot/status/1706786138436846040#m


(And we saw that 70% of ship transport was actually fuels. If we cut out more of that, you get better scaling too...)

[NeilT]

I had some thoughts on this.  One was graphene cylinders filled with Hydrogen at below atmospheric pressure with a pumping system to maintain that differential at different altitudes.

This reduces leakage risk without accident and also allows a very high altitude if required.

[Linus]

I would think that if the modern airship concept is indeed going to become viable, the Airlander 10 project would be the first to show the way.


Hybrid Air Vehicles (HAV), a UK-based leader in sustainable aircraft technologies, and Air Nostrum Group, which includes Hibernian Airlines in Ireland and Mel Air in Malta, have agreed to double the number of Airlander 10 under reservation, to a total of 20 aircraft.

Under the initial agreement, announced in June 2022, Air Nostrum Group had reserved 10 Airlander 10 aircraft, with a 100-passenger configuration. Under the new agreement, Air Nostrum Group has reserved a further 10 Airlander aircraft to underpin expansion of the Airlander network from Spain into the Mediterranean region, including Malta.

With the first Airlander 10 services planned within five years, additional potential route networks for Airlander aircraft were recently presented by leaders from both Mel Air (part of the Air Nostrum Group) and Hybrid Air Vehicles to Transport Malta. Discussions included the advantages of Airlander’s potential land and water-based operations for routes including Malta-Gozo, Malta-Sicily, and other key links with Italy, Tunisia, and Libya.

Air Nostrum has also joined the Airlander 50 Development Partner Programme, becoming the first commercial airline partner in that project.

Airlander 50 is designed to accommodate a 50-tonne payload, and will address the future of freight, moving cargo or people point-to-point with minimal infrastructure and a low environmental impact. The Airlander 50 Development Partner Programme enables key partners and future Airlander 50 customers to influence and enhance Hybrid Air Vehicles’ Airlander 50 specification.

In March 2023, Hybrid Air Vehicles and the South Yorkshire Mayoral Combined Authority of the UK, led by Mayor Oliver Coppard, announced a £7m investment into plans to deliver production of Airlander 10 aircraft in the region. The plans will enable the creation of over 1,200 highly skilled jobs and thriving new supply chains.

https://www.hybridairvehicles.com/news-and-media/overview/news/air-nostrum-group-doubles-reservation-agreement/

[Sigmetnow]

The idea of huge airships transporting large amounts of transoceanic cargo relatively quickly without the use of fossil fuels is an inviting one.
 
But…  there is little in the quoted papers to suggest how such a huge aircraft could be constructed, and managed.
 

…It should be noted that a structure larger than, say, 1 km is extremely delicate. If there is a considerable difference in the wind velocities between the front and the back of the airship, during a storm, it could be torn in half. Thus, it should be built to be strong enough to withstand the shear caused by the winds from different directions. New material technologies might be able to guarantee the robustness and resilience to endure heavy storms.

 

Docking airships is challenging due to their large size, limited control mechanisms, and high wind drag. Another particular issue is to keep the airship attached to the ground during windy episodes. The diameter of the airship hydrogen carrier (Fig. 2) is similar to the height of the Empire State Building in New York. It would be very challenging to keep such large airship from collapsing under strong superficial winds.

 

… Then unload 500 tons of cargo. The airship would suddenly want to pop back up into the air. With 500 tons of weight removed, it would become very buoyant again.
The low-tech way of dealing with this problem is using a lot of water ballast on the ground. Put 500+ tons of water into tanks onboard the airship, then unload the cargo.

(Assuming the structure of the craft could withstand the extra weight. Or, it might require micro-managing additional water ballast as each cargo container is removed.)

Using the jet stream for maximum transit speed means one-way travel, and the dangerous co-mingling of slow airships with the fast planes also using the jet stream for maximum travel efficiency:
 

5.1. Unidirectional, west to east routes
Using the jet stream for airship and balloon transportation has some peculiarities. A major consideration is that the airship has to travel in one direction, from west to east, around the world. For example, an airship would fly from New York to London; however, the return trip would be very difficult.
 
Another consideration is that, most of the energy requirement in airships and balloons is the lift to the stratosphere as the jet stream pushes them to their final destination, thus, long-distance routes should be prioritized.

 

5.2. Competition with conventional planes long haul flights
Long haul flights cruising altitude for conventional planes can reach as high as 14 km of altitude. Given that the pressure levels with the highest average W-E wind speed (165 m/s) is 200 hPa, which is equivalent to an altitude of 12 km, airships and conventional planes will have to share the same altitude range of their flight routes if they want to better use the jet stream. The introduction of airships will then require new regulations to reduce the risks of accidents between planes and airships.

Water created by hydrogen fuel cells would increase the aircraft’s weight, but venting water overboard into the stratosphere may have unforeseen climate effects.

5.10. Artificial precipitation
Airships or balloons could also be used for rainmaking. Some of the hydrogen used to lift the airship could be used to generate electricity with fuel cell using the oxygen in the stratosphere for additional propulsion to drive the airship, or to liquefy hydrogen. One of the by-products from electricity generation with hydrogen is water. One ton of hydrogen produces nine tons of water. The water produced increases the weight on the airship and, thus, reduces the energy required to compress the hydrogen, when returning to the ground. This water could also be released from the stratosphere at a height in which the water will freeze before entering the troposphere where it would melt. Reducing the temperature of the troposphere would increase its relative humidity until it saturates and precipitation begins. The commencement of the precipitation would initiate a convection rain pattern, feeding more humidity and rain into the system.

https://www.sciencedirect.com/science/article/pii/S2590174519300145

[interstitial]

How would a hydrogen bomb airship survive a lightning strike?

[Sigmetnow]

How would a hydrogen bomb airship survive a lightning strike?

Good question.  Hydrogen/Oxygen rockets (as well as those using other fuels) have strict launch criteria that forbid launching near electrical storms, or when the electrical field in the atmosphere is charged. 

Still, rockets are out of the atmosphere and into space within just a few minutes after launch.  But in a vehicle with limited maneuvering, on a trip that takes days, that risk might be hard to avoid.

[NeilT]

How would a hydrogen bomb airship survive a lightning strike?

The same way buildings do, by creating conductors and flowing the power either to storage or leaking emitters.  Whilst the amount of energy is high, it is not impossible to manage it.

Sig, rockets need to reduce weight to an absolute minimum negating comprehensive lightning management structures.  For Airships this is not the same situation.

The differences between mid 1920's technology and 21st century technology are like horse and cart to space rockets.  The gas bags used materials with a very short life for containing hydrogen and the systems to vent overpressure were crude in the extreme. The frames were covered in cotton which was painted with multiple layers of flammable paints to protect the interior.

Original airships used gas bags to contain the hydrogen.  Due to atmospheric pressure differences the gas had to be vented or added to not rupture the structure.

Creating a series of rigid graphene structures which can contain hydrogen at below atmospheric pressure removes a very large amount of the issues with hydrogen leakage and explosion dangers.  These can be bundled inside the frame of the airship and kept out of the environment.  They can also be electrically insulated from the structure.

We are considering hydrogen cars on the roads and trucks on the roads.  Vehicle accidents are far more prevalent than air accidents. 

1930's engines for airships were woefully poor compared to current turboprop engines.  The Hindenburg was designed to have 4 engines but wound up with 10 and it still struggled to navigate in high winds.

If we are ever going to see true airship freight, then some serious lateral thinking needs to be done.

[Sigmetnow]

a series of rigid graphene structures which can contain hydrogen at below atmospheric pressure

Hardly seems “light,” especially for a mega-craft, aiming for the jet stream, which must climb 10 to 20 thousand feet above where airships normally max out.  And hydrogen always leaks, whatever material you try to contain it with.  Even modern valves do not perform perfectly.  See:  Starliner or SLS.

—-
P.S.:

Sig, rockets need to reduce weight to an absolute minimum negating comprehensive lightning management structures.  For Airships this is not the same situation.

The football-field size Airlander is 20 metric tons.
 
The medium-lift Falcon 9 rocket weighs 550 metric tons. The first stage and fairing are hefty enough to endure thermal, vibration and g-forces (more than 1.7 million pounds of thrust at sea level) — over multiple launches and landings — that an airship would collapse just thinking about.  And the Falcon must protect the sensitive electronics of all the satellites it is carrying to space.  (E Field Limit from fairing electronics = 80 dBμV/m from 30 to 18000 MHz)

[Linus]

How would a hydrogen bomb airship survive a lightning strike?

The same way that an aircraft that is loaded with highly volatile avgas (and explosive avgas vapors) would. Although jet fuel is much less volatile, we tend to forget that aviation gasoline was (and still is) in the tanks for many many years of lightning strikes.

Disaster is averted by maintenance of good electrical bonding across the airframe and maintenance of a pathway for exit of the charge via properly bonded static wicks.

[interstitial]

I would not want to be the guy who grounds the airship when it lands.

[sidd]

Re: graphene containing hydrogen

C + 2H2 = CH4

Then another boom with the CH4 + 2O2 = C02 + 2H2O  thing

sidd

[NeilT]

I think that most people are not looking at the massive material strides made in the latter 20th century and 21st century and what it means for an airship lifted by hydrogen.

First, Duralumin (which we know in wheels as mag alloy), needs to be compared with carbon fibre.  Duralumin weight to strength ratio is 9 times heavier than carbon fibre for the same strength.

So that's the entire structure of the airship.

Now let's look at the difference between Gelatine layered cotton and Graphene for the Hydrogen chambers.  Cotton has a density of 448KG per cubic meter.  Graphene has a density of 160 GRAMS per cubic meter.

Of course then there is the cotton outer skin of the ship itself, which, if replaced with Graphene plates, would be a strengthening material that reduces the required size and weight of the internal structure.

Then I mentioned Graphene as the storage mechanism for Hydrogen.  I have found some articles which talk about Graphene as the storage mechanism for Hydrogen.  Theory says that Hydrogen could find its way between the graphite layers.

At 20 atmospheres.

Now what did I say about the hydrogen chambers.  Did I say at a positive pressure?  No I didn't.  I said at a pressure LOWER than atmospheric and using a pumping system to extract hydrogen from the tanks to retain that lower pressure at higher altitudes.

In essence the "valve" holding back the hydrogen in the tanks is atmospheric pressure itself. The extracted hydrogen can go into traditional tanks under pressure to be re-injected as required at lower altitude.  The Hindenburg vented between 1 million and 1.5 million cubic feet of hydrogen during a typical Atlantic voyage.

Taking these considerations into account I believe that a Hindenburg sized airship could easily be built to lift 130 tons of cargo safely using hydrogen, powered by small and efficient turboprops running on hydrogen.

One of the biggest issues with the airships of the 1930's was the ability to navigate with the available thrust.  A quick check of google reveals that Pratt & Whitney do a range of turboprop engines ranging from 1,800 hp to 5,000hp.  The Hindenburg was designed with 4 naval diesel engines with a max output of 1,300hp.  These were massive 16 cylinder engines and weighing 2 tonnes each with oil.  The 6,000hp variant of the turboprop (yes the article says up to 5,000 but the table at the bottom says 6,000) weighs just over 700kg.

Of course you could re-engineer the Hindenburg to use Helium with modern engineering.  It would probably be able to carry about 100t of cargo.  Making it a bit fatter would probably increase that dramatically, the Hindenburg carried twice the lift gas of the original Graf zeppelin simply by being a bit longer and fatter.

However Helium still remains a constrained gas which is extremely difficult to manufacture.  Unless we're rethinking mass scale Nuclear.

Hence my "revisit the engineering advances in the last 100 years" and use the better lift gas which is plentiful and easy to generate more of.  Oh and it fuels the engines too.

That's my thoughts on Airships if we want to go there.

[nadir]

Problem with airships is the winds. Even when now we have infinitely better capability to forecast winds and calculate the optimal trajectory laterally and vertically, each day the flight time will vary, becoming actually infinite when strong headwinds cannot be  circumvented with a practical route.

The problem with this day-to-day variation is that the schedule and even availability of service some days is very uncertain and this creates big logistics and planning issues. Much more unstable service than commercial jets since the airship speeds are much lower, often comparable with prevailing winds.

Edit. Hold the prints… there’s a Spanish Airline company, Air Nostrum, that has ordered 10 helium airships for Barcelona-Majorca route.

https://www.cnn.com/travel/article/airlander-10-air-nostrum/index.html

Delivery date, 2026.

Still, this airship line is backed-up with jet airline. Meaning some days it won’t simply work and will redirect passengers and cargo to commercial jets, or it will risk to take many more hours than the four hours standard to cover the distance…

Edit2. This is a joke, the max speed is 80 mph ~ 70 knot. I bet this airship will not be operating from October to May. Winds in western Mediterranean during Winter are not a joke. For the entire troposphere. And this thing cannot fly above 30,000 feet.

I don’t see this competitive. Pressurized jets were invented precisely to circumvent the weather and to fly ultra fast. Regional commercial flights have no competition in these airships.

[SteveMDFP]

Re: graphene containing hydrogen

C + 2H2 = CH4

Then another boom with the CH4 + 2O2 = C02 + 2H2O  thing

sidd

True of carbon in general.  But the C-C bonds in graphene are considerably stronger than typical C-C bonds, thus more stable..  We'd want experimental data to be sure.  I feel sure that such experiments have been done.

As for graphene cylinders to  hold the hydrogen at below-ambient pressures. I'm  skeptical that they could be light enough to work.  Hydrogen, however, does not appreciably diffuse through graphene, unlike almost all other materials, so it's an  interesting thought.

Perhaps the optimum solution might be to apply a very thin layer of graphene to the gas bags.  To reduce buoyancy when needed, the hydrogen might be compressed into high-pressure containers.  The lifting gas thus gets transformed into additional ballast, temporarily.

[Sigmetnow]

Now what did I say about the hydrogen chambers.  Did I say at a positive pressure?  No I didn't.  I said at a pressure LOWER than atmospheric and using a pumping system to extract hydrogen from the tanks to retain that lower pressure at higher altitudes.

In essence the "valve" holding back the hydrogen in the tanks is atmospheric pressure itself. The extracted hydrogen can go into traditional tanks under pressure to be re-injected as required at lower altitude.  The Hindenburg vented between 1 million and 1.5 million cubic feet of hydrogen during a typical Atlantic voyage.

If solid tanks are providing buoyancy, why use hydrogen in them at all?   
 
Use vacuum pumps to reduce the air pressure to below ambient pressure. (At around 30,000 feet, it’s down to about 265 millibars, less than 30% of sea level pressure.  Fortunately, air is not as tricky to handle as hydrogen.)   For descent, gradually let the air in/ reduce the vacuum / add air from the “traditional tanks”…. 
 
It still comes down to how much all those tanks — and the pump system, the ship, and the cargo — weigh, versus the weight of the atmosphere that is displaced.

[NeilT]

The hydrogen in the solid tanks is providing the buoyancy.

The idea is to keep the tanks 1psi below atmospheric (or less as required), to stop the hydrogen escaping.  Structural strength to withstand that pressure is not difficult, or heavy.

A US Marine captain calculated out materials and specs for pure vacuum.  It is possible but only for incredibly small weights.

Given the weight advantages of modern materials and power plant, the weight of pumps and storage for excess hydrogen would be minimal.

[morganism]

There is also a Euro company that made a hydrogen "paste" as an auto refueling system.
Pull into a station, grab a new tube of paste, and slap it in the slot.

Now if you could use the h20 byproduct to make hydroxyls to vent in upper troposphere, that would be very helpful. Would really help with methane removal. And if we ever have to geoengineer with sulpherized aerosols, much more friendly than jet flights.

The LOON ballons could hold station just by varying altitude for months. I'm pretty sure you can find steering winds at diff altitudes to get you into direction you want to go.
 
The W to E prob is tougher, cause you have China/Russia and Mid East to steer around to tack back onto steering E to W winds. That sets up trading circles just like the masted ships.

[nadir]

Now what did I say about the hydrogen chambers.  Did I say at a positive pressure?  No I didn't.  I said at a pressure LOWER than atmospheric and using a pumping system to extract hydrogen from the tanks to retain that lower pressure at higher altitudes.

In essence the "valve" holding back the hydrogen in the tanks is atmospheric pressure itself. The extracted hydrogen can go into traditional tanks under pressure to be re-injected as required at lower altitude.  The Hindenburg vented between 1 million and 1.5 million cubic feet of hydrogen during a typical Atlantic voyage.

If solid tanks are providing buoyancy, why use hydrogen in them at all?   
 
Use vacuum pumps to reduce the air pressure to below ambient pressure. (At around 30,000 feet, it’s down to about 265 millibars, less than 30% of sea level pressure.  Fortunately, air is not as tricky to handle as hydrogen.)   For descent, gradually let the air in/ reduce the vacuum / add air from the “traditional tanks”…. 
 
It still comes down to how much all those tanks — and the pump system, the ship, and the cargo — weigh, versus the weight of the atmosphere that is displaced.

Can’t you just imagine the energy required to create the vacuum in such huge amount of volume?

100 passengers * 100 kg = 10,000kg
Add another 10,000 kg of structure (being generously short) and 5,000 kg of whatever propels this thing.

25,000 kg of needed buoyancy.

That’s 25,000 m3 of required vacuum volume!!!

Search the internet on how much would it cost to create 25,000 m3 of vacuum.

Or even better, pitch the idea to Elon Musk, he may buy it!

[interstitial]

 Current production methods are focused on making thin sheets of graphene not structural parts. Your balloon (not the right word as it needs to be structural to maintain negative pressure) would be made of something else and coated in graphene.
 
 
 It should be a balloon with above atmospheric pressure as the weight difference for below atmospheric pressure would be large.
 
 
 A graphene sheet may not leak hydrogen but a large structure like a blimp would not be made from one large sheet. The joints however they are made would probably leak. All of the valves and piping would leak and most of those would be inside the craft not outside.
 
 
 You need to actually vent the gas because pumping it into a high pressure tank does not help the buoyancy of the craft.
 
 
 Hydrogen has one of if not the largest explosive range of all gases. It is explosive from 18-60% and flammable from 4 to 75%. That means most concentrations of hydrogen in air are explosive.

Automotive gas (I did not find the range for aviation gas which is different) has an explosive range of 1.4 to 7.6%. Methane (the major component of natural gas) has a flammable range of 4.4 – 16.4%. Nearly all the liquids and gases we think of as highly combustible have much smaller ranges than hydrogen. The practical implication of this is that even when there is a leak there is only a small shell of escaping gases where it is flammable. In the rest of the volume around a leak those gases are not flammable. Near a leak concentrations will be high and dissipate as you go further out. Most gases are not flammable at high concentrations. Any ignition source like a spark is more likely to occur near the surface. Most gases have flammable ranges below 30% and often below 20%. That means hydrogen is substantially more dangerous than most if not all of the gases out there.

[Sigmetnow]

That’s 25,000 m3 of required vacuum volume!!!

Search the internet on how much would it cost to create 25,000 m3 of vacuum.

Now calculate the amount and cost of hydrogen that would be required.  Almost all of which would need to be replenished before every trip.

The idea is to keep the tanks 1psi below atmospheric (or less as required), to stop the hydrogen escaping.  Structural strength to withstand that pressure is not difficult, or heavy.

So the hydrogen tanks are slightly below sea level pressure at liftoff, and gas is continuously pumped overboard to maintain a lower than ambient pressure… thus the gas is just outside the ship during its entire climb through an electrically charged atmosphere?  Yikes. 

Trying to recycle the hydrogen by pumping it from low-pressure solid tanks into high-pressure solid tanks would not change the weight or buoyancy of the aircraft.  It could change aircraft’s trim (attitude, or angle of flight), depending on where in the ship the various tanks are located. 

Descent would then require having enough flexible bags to deflate to make the ship displace less atmosphere. 

[NeilT]

My answer to interstitial is on my pc and I'm mobile right now.

Sig you interpreted my statement with your own view.  I said pump the hydrogen to storage.

BTW anything pumped "overboard" would immediately rise towards the top of atmosphere never mind the flow of air over the airframe at, say, 200mph.

Not that I would waste a valuable fuel.

[kassy]

Maybe high tech zeppelins are not that relevant?

For the world at large it is more important what we do with the planes we use.

[NeilT]

Maybe high tech zeppelins are not that relevant?

For the world at large it is more important what we do with the planes we use.

Perhaps, perhaps not.  Air travel is part of the expectations of society today yet we know that how we do it today is damaging to the climate and the atmospheric gas balance.

High tech Zeppelin's offer a compromise which does not mean we have to forgo air travel.

I'll answer Interstitial anyway.

[NeilT]

Current production methods are focused on making thin sheets of graphene not structural parts. Your balloon (not the right word as it needs to be structural to maintain negative pressure) would be made of something else and coated in graphene.
 
 
 It should be a balloon with above atmospheric pressure as the weight difference for below atmospheric pressure would be large.

I was thinking of Graphene cylinders, not balloons, balls or "gas bags".  These can be made in multi ply layers for strength and can use carbon fibre for additional structure.  Yes the bonding agent would need to be carefully chosen, however, as you recall, I'm not relying on the graphene to stop the hardest to solve leaks; I'm relying on the atmosphere outside the cylinder.

This is the opposite of all other airship designs which require pressure within the lifting envelope to retain structural integrity, creating a pressure gradient through which Hydrogen will leak.

I was thinking of the cylinders working much like the structural pack of a Tesla. Where, unlike the gas bags of prior airships, the lift vessels themselves would be part of the structural frame which reduces the weight of the overall structure.  As we all know from the Tesla battery designs for structural batteries.

There may only be an 8% lift difference between Helium and Hydrogen but at a higher scale it is significant.  The Airlander requires aerodynamics to lift cargo as well as Helium.  Helium is a scarce gas with limited overall supply and in the volumes required for aviation would be prohibitive in cost.

Now as to explosivity, that requires oxygen.

Again, the difference in the design by cladding the outside of the vehicle with rigid graphene sheets means we can do things differently again.  There is no reason why the entire body of the vessel not be filled with N2.  Nitrogen in N2 form is stable and is used in aviation to purge aircraft fuel tanks when empty to prevent explosions.  I did check and you need both high pressure and temperature to create 2NH3 from N2 and H2.  So Ammonia would not happen.  Also N2 is 3% lighter than air.

In this case any Hydrogen which does escape will vent to the top of the vehicle, above the Nitrogen, where it can be separated from the Nitrogen using a membrane.  Either to be vented outside of the vehicle or pumped back for storage.  Something which was not available to 1930's science.

This is far less dangerous on a graphene skin than the skin of a 1930's airship which was both canvas and coated in a mixture of cellulose acetate butyrate and aluminum powder.  Hardly combustion resistant. Graphene and carbon fibre are resistant to temperatures up to thousands of degree C, canvas is hundreds and Duralumin is 500.

So if we have a vessel which is constructed to carry hydrogen with minimum loss, with a radically different weight profile, which contains every safeguard known to 21st century including filling the gas enclosure with an inert gas to prevent combustion, then why cannot it be as safe, or safer than, an automobile, running on hydrogen, which has a high speed crash on the highway.  Or a bus running on Hydrogen which is more relevant, or even an aircraft running on hydrogen?

Then we come down to the ability to manoeuvre in difficult conditions.  Trent T. Metlen, when doing his thesis on vacuum airships, came to the conclusion that most of the issues with airships was the inability to control buoyancy sufficiently well to be able to manage the ship in difficult conditions.  If you read up about the Hindenburg they used ballast bags which were thrown overboard and a complicated moisture reclamation process from the engines in flight to fill buoyancy tanks.

Much as Trent theorises that this can be done by pumping to balance buoyancy, I also believe that by using gasses and pumping, such as N2 in the bottom of the cylinder and H2 in the top, the buoyancy of the vessel can be rapidly and precisely controlled.

I'd go further though.  It is well known that the tail fins on airships were inadequate to laterally control them in high winds.  I'd say that the gyroscopic attitude controls used by the ISS, at a much larger scale, would help with this.

Thinking back to what I looked at before I believe it would be possible, using modern materials and construction,that  building a Hindenburg equivalent could be done in 40 tonnes.  This would leave around 190 tonnes of lift.

The next bit, as they learned in the 1920's, is also relevant for airships.  An increase in diameter of 41% doubles the available lift gas.  Increasing the length a bit and diameter somewhat less achieves the same result.  As was seen between the Graf Zeppelin and the Hindenburg.

Meaning that with a judicious extension of the Hindenburg dimensions, 400t of lift should be possible.

All of these issues have solutions.  Pipes, valves, storage tanks. Already solved.  Otherwise do you believe they would allow a Hydrogen vehicle in an underground parking lot?  Or even in a home garage?

Now what about comparison to current aviation?  I see no reason why an airship of this design could not reach 200mph when driven by turboprops.  Meaning about 16 hours or so to cross the Atlantic.  This is even feasible for a business journey. If we increase the carrying capacity by 10x, this brings the max passengers to 700.

Although the Hindenburg did have a dining room, reading and writing room, lounge and, yes, even a smoking room!  Apparently the kitchen was all electric given that no naked flame was allowed on the ship?

Not that I would expect anyone to go in a Hydrogen ship before it had been thoroughly proven by many freight journeys.

[SteveMDFP]

A graphene sheet may not leak hydrogen but a large structure like a blimp would not be made from one large sheet. The joints however they are made would probably leak. All of the valves and piping would leak and most of those would be inside the craft not outside.

Of course.  But if 90% of the surfaces in contact with hydrogen are coated, then it's reasonable to presume that losses will be reduced 90%

You need to actually vent the gas because pumping it into a high pressure tank does not help the buoyancy of the craft.

Not true.  Nothing can displace a larger volume of air than its own volume.  Reduce the volume of hydrogen, and you reduce the buoyancy.  When the density of compressed hydrogen exceeds ambient air, then it acts as additional ballast.
 

[interstitial]

Ok so make a carbon fiber cylindrical shell then use chemical vapor deposition to seal it with graphene. That makes more sense now but is not really what you said.


For ballast would not compressed air make more sense? For that you want the higher density at a given pressure and its readily available. Further there would be no issues venting it.


Pumping gases into different portions of the air ship even at different pressures does not change the buoyancy at all. Unless you mean something different here too.


I doubt you would get noticeable separation of nitrogen and hydrogen in a tank on your airship. A sensor selective for hydrogen and the ability to flush with nitrogen would probably get the job done.


In my opinion the only reason they have not banned hydrogen cars is because there are not enough of them out there to see what happens when things go wrong. What I do not trust here is use of hydrogen by individuals without supervision. 


Having said that with a good safety program hydrogen can probably be used if the graphene is as impermeable as it sounds.

[interstitial]

Not true.  Nothing can displace a larger volume of air than its own volume.  Reduce the volume of hydrogen, and you reduce the buoyancy.  When the density of compressed hydrogen exceeds ambient air, then it acts as additional ballast.
 

If you have 10 kg of air at 1 atm pressure then you pump it to 10 atm it still weighs 10 kg.


The volume of the ship does not change it has a rigid shell.

[SteveMDFP]

Not true.  Nothing can displace a larger volume of air than its own volume.  Reduce the volume of hydrogen, and you reduce the buoyancy.  When the density of compressed hydrogen exceeds ambient air, then it acts as additional ballast.

If you have 10 kg of air at 1 atm pressure then you pump it to 10 atm it still weighs 10 kg.

Yes, it still weighs 10 kg, but it displaces less air, providing less buoyancy.

The volume of the ship does not change it has a rigid shell.

Not that rigid.  You think the hydrogen reservoirs would be designed to withstand a substantial pressure differential with the atmosphere?  If so, then venting hydrogen would not decrease buoyancy either.  You'd still have the hydrogen reservoirs displacing the same amount of air.

[oren]

I will just go on record that this airship idea will not fly, in real life. Too many engineering and practical hurdles, too few problems it solves economically.
It does fly here at least, nearly 30 posts and still counting.
Check back in a couple of years.

[interstitial]

Not true.  Nothing can displace a larger volume of air than its own volume.  Reduce the volume of hydrogen, and you reduce the buoyancy.  When the density of compressed hydrogen exceeds ambient air, then it acts as additional ballast.

If you have 10 kg of air at 1 atm pressure then you pump it to 10 atm it still weighs 10 kg.

Yes, it still weighs 10 kg, but it displaces less air, providing less buoyancy.

The volume of the ship does not change it has a rigid shell.

Not that rigid.  You think the hydrogen reservoirs would be designed to withstand a substantial pressure differential with the atmosphere?  If so, then venting hydrogen would not decrease buoyancy either.  You'd still have the hydrogen reservoirs displacing the same amount of air.

Pumping hydrogen out would make it lighter and thus increase buoyancy. You can not vent because it is at negative pressure to atmosphere. You must pump it.



The ballast system should be separate from the main balloon. Pump air from outside balloon to inside pressurized tank to add weight. Release pressurized air to atmosphere to make lighter.


I get the feeling we are talking about different things.

[vox_mundi]

There's a reason why nobody uses vacuum to get off the ground ...



1 cu. meter of air weighs 1.2 kg. Remove it and you have 1.2 kg of buoyancy. The buoyancy drops off rapidly with altitude.- 30% at 3000 meters, - 55% at 6000 meters

I worked with an instrument with a vacuum chamber slightly smaller than 1 cu. meter. The chamber weighed 150 kg to resist implosion and the vacuum pumps weighed an  additional 40 kg.

A graphite shell will resist implosion about as well as the OceanGate sub did next to the Titanic

[NeilT]

I will just go on record that this airship idea will not fly, in real life. Too many engineering and practical hurdles, too few problems it solves economically.
It does fly here at least, nearly 30 posts and still counting.
Check back in a couple of years.

I get the point here oren.  But then much of what we are trying to achieve on the AGW front is extreme engineering.  The amount of effort going into producing hydrogen, the extreme engineering going into automotive to make it more efficient and more attractive.

There will come a time when there is a huge lobby, by people who have never really travelled far from home, to block air travel due to climate impacts.  Then there will need to be a solution.  I happen to think that this is actually easier than electric air with 400t of cargo/people.

[NeilT]

Not true.  Nothing can displace a larger volume of air than its own volume.  Reduce the volume of hydrogen, and you reduce the buoyancy.  When the density of compressed hydrogen exceeds ambient air, then it acts as additional ballast.
 

If you have 10 kg of air at 1 atm pressure then you pump it to 10 atm it still weighs 10 kg.


The volume of the ship does not change it has a rigid shell.

OK I get what you are saying, unless I generate the N2 on the airship and vent it then the balance doesn't change.  Fair enough, that idea doesn't work unless I take air and strip the N2, which is probably uneconomical. 

But having high pressure chambers which are empty in which I compress air would do the same thing.  Adding ballast by adding air at a high compression.  It is energy hungry to be sure, but it can do the job.

[NeilT]

There's a reason why nobody uses vacuum to get off the ground ...

Hence the reason I said 1psi below atmospheric with Hydrogen as the lift agent, not 14.7psi below atmosphereic.

[NeilT]

Pumping hydrogen out would make it lighter and thus increase buoyancy. You can not vent because it is at negative pressure to atmosphere. You must pump it.

Yes if you were sacrificing hydrogen.  I agreed below.

The ballast system should be separate from the main balloon. Pump air from outside balloon to inside pressurized tank to add weight. Release pressurized air to atmosphere to make lighter.


I get the feeling we are talking about different things.

Yes I said the same below.  It would do the job and the medium is readily available.  Just pump it in and open it up and let it out.  No water or other gasses needed.

I'd still fill the body of the ship with N2 though, instead of air.  As a fire suppressant.

[NeilT]

Ok so make a carbon fiber cylindrical shell then use chemical vapor deposition to seal it with graphene. That makes more sense now but is not really what you said.

The bit about extreme engineering to solve the problems which come with an airship?

But, yes, it is implied that the cylinders are created and sealed with the lightest and most effective methods known to science of the 21st century.  Which fits with what you say above if it is not practical to do so with pre formed sheets of graphene.

Although I was thinking of graphene formed in cylinders, buttressed by carbon fibre and using a chemical vapour deposition to give the final layer of graphene to the tank to seal it.

Of course if the graphene is not strong enough to do the job then a different fibre could be used for the tank.

Go look up Trent T Metlen's vacuum airship design.  There is a huge amount of research on material strength's and weights.  I just felt that his approach of pure vacuum could be blended with Hydrogen to create a self sealing system which could provide the lift needed using the most advanced engineering and manufacturing techniques and making it safer than a 1930's hydrogen gas bag.

https://core.ac.uk/download/pdf/277528467.pdf

[kassy]

I get the point here oren.  But then much of what we are trying to achieve on the AGW front is extreme engineering.

 

Well we don´t have time to wait for extreme engineering. Fluffy zeppelins are a complete non solution. Time is money so it is not a serious competitor for passengers and it is not needed for freight.

The real issues for aviation are simple. How do we get it to pay for it´s own emissions.

[interstitial]

It is not necessarily that graphene could not be made thick enough to make it structural it is that currently I do not think anyone knows how to do that and they are trying. From what I could find and I did not look real hard graphene is currently made in thin films. Your solution is a materials problem that needs research and mine is an engineering problem that likely just requires some tweaking. That is assuming that carbon fiber would be light enough and rigid enough to work.


It could work.

[NeilT]

The real issues for aviation are simple. How do we get it to pay for it´s own emissions.

Actually that is the real problem here.   We don't need to pay for anything, we need to stop or transform the issues.  So long as AGW is seen as something that can be fixed with finance it is never going to be fixed.

So I see Aviation as something which needs to be fixed.  Not paid for.

I know it is a different viewpoint but I believe it is an important one.  So much of the COP meetings is about money.  In fact it needs to be about actually Doing stuff to change the impact we are making in the world.

No I'm not naive, that costs money.  But that money needs to be used for actual Things and actual Work which stop emissions and start to reduce the CO2 load.

So I think about stuff.  I read about stuff.  I think about how it can be applied.

If you go and look at the Hindenburg photo's you see a whole different world of travel.  Places where people can work, relax, travel without stress.  Now add Starlink to that and mobile working and mobile phone service over wifi whilst travelling.  All of a sudden our 16 hour journey becomes a working platform for many and somewhere that the travellers can work rest, relax and enjoy the journey.

Just as I have been forced to see and accept that they way to travel with an EV is going to change  the way I travel, I see not reason why air travel cannot evolve. Those who need to go fast will have services such as supersonic planes, or even point to point Starship.  Those who have more time can take a less stressful journey.

But this goes back to what I have been saying all along.  You cannot force people to move away from CO2 emissions to a choice wich doesn't work for them.  You need to create choices for them which will work and then remove the CO2 intensive choice.

These are my thoughts on aviation.  Well some of them.  But certainly on one way of replacing current mass aviation with a different form of travel.

The thing about airships is that there is little to no interest in creating something different and designers are working with one hand behind their backs with the need to use Helium.

This is much the way space launch was before SpaceX arrived.  SpaceX proved that with the right drive and the right application of money and with the right person backing it, then things can change and once they have changed everyone starts asking themselves "Why did we do it that way anyway?"

[NeilT]

It is not necessarily that graphene could not be made thick enough to make it structural it is that currently I do not think anyone knows how to do that and they are trying. From what I could find and I did not look real hard graphene is currently made in thin films. Your solution is a materials problem that needs research and mine is an engineering problem that likely just requires some tweaking. That is assuming that carbon fiber would be light enough and rigid enough to work.


It could work.

Have a look at the work of Trent that I posted.  He did that work even though it was from a vacuum perspective.  It Can work.  It has just never been tried in the 21st century.

[kassy]

Most people fly to get somewhere so minimal flight time is preferred. Dream about zeppelins all you like but it is not a current aviation thing. It is not going to be relevant in the near future to aviation emissions etc.

[John_the_Younger]

Sceye completes third test flight for high altitude communications airship
August 21, 2023

...
this is an airship that flies at 65,000 ft and is powered by solar energy captured by the airship's solar 'cape' covering the platform, made of Copper Indium Gallium Selenide Cells and Gallium Arsenide Cells. The Sceye HAPS has been proposed not only to provide connectivity to rural communities and underserved regions, but also to house onboard sensors that can track greenhouse gases in real-time, and provide high-resolution earth observation.
...

This effort is still moving forward, if not slowly!  Sceye website: https://www.sceye.com/

[NeilT]

Yes but the difference is like between this



And this.

[oren]

Setting aside airships, which thankfully moved on to another thread, I think passenger aviation has several reasonable ways to evolve:
* Electric airplanes for short haul flights, with flight envelopes improving over time.
* Renewable synthetic fuels (liquids, not hydrogen) for long haul flights.
* Pay for emissions when using fossil fuels, with a full offset (by carbon capture or whatever), this is probably less economical than the previous two solutions.
* And of course, reduced flying when the above solutions turn out to be more expensive than the current all-you-can-emit.

Freight can go via airplanes or ships as it does now, using renewable synthetic fuels. Ships can use sails and solar panels to save some fuel (out of the scope of this thread).

[Sigmetnow]

Sceye completes third test flight for high altitude communications airship
August 21, 2023

...
this is an airship that flies at 65,000 ft and is powered by solar energy captured by the airship's solar 'cape' covering the platform, made of Copper Indium Gallium Selenide Cells and Gallium Arsenide Cells. The Sceye HAPS has been proposed not only to provide connectivity to rural communities and underserved regions, but also to house onboard sensors that can track greenhouse gases in real-time, and provide high-resolution earth observation.
...

This effort is still moving forward, if not slowly!  Sceye website: https://www.sceye.com/

Google experimented with internet balloons a few years ago, but couldn’t find a way to monetize them.
 
Google says goodbye to giant internet balloons idea - BBC News
https://www.bbc.com/news/business-55761172

 
Low Earth Orbit (LEO) satellite constellations (Iridium, Globalstar, Orbcomm, Starlink) are quickly modernizing world-wide remote communication, now that launch costs are a fraction of what they used to be.  Smaller, cheaper, more numerous and easily-replaced satellites in easily-reached LEO orbits are replacing the historically large and expensive satellites in (distant, hard-to-reach) Geo-stationary orbits which by their nature serve only limited parts of the earth’s surface.

[NeilT]

A while back I theorised that a large enough hydrogen tank, same as I proposed for the airship, kept below atmospheric pressure, until pumped to a full vacuum, could sit on top of the atmosphere for a very long time indeed without any help.  Solar panels, pumps to keep the vacuum solid, probably most of what was being pumped out would by hydrogen and helium.... 

Flights of fancy.

[interstitial]

It is not necessarily that graphene could not be made thick enough to make it structural it is that currently I do not think anyone knows how to do that and they are trying. From what I could find and I did not look real hard graphene is currently made in thin films. Your solution is a materials problem that needs research and mine is an engineering problem that likely just requires some tweaking. That is assuming that carbon fiber would be light enough and rigid enough to work.


It could work.

Have a look at the work of Trent that I posted.  He did that work even though it was from a vacuum perspective.  It Can work.  It has just never been tried in the 21st century.

I tried to open the pdf but I get an error

[NeilT]

I tried to open the pdf but I get an error

Try this.

https://file.io/b1ihde9OaCJM

Perhaps UK universities have location restrictions??

[NeilT]

Sharing files sucks.  This works

https://ufile.io/w4gh1xpr

password is letmein it is there for 30 days.

[interstitial]

I tried to open the pdf but I get an error

Try this.

https://file.io/b1ihde9OaCJM

Perhaps UK universities have location restrictions??

this work and I read parts I am just not sure if I have much to say about it.