A recent paper proposes to bring zeppelins back | Hacker News Reader

A recent paper proposes to bring zeppelins back

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103 pointslxm105 comments

CargoLifter [1] tried to bring Zeppelins back in the late nineties. They started building a gigantic manufacturing building but ran out of money before they even started to build a Zeppelin. The hangar was later turned into an aqua park but ran into troubles because the heating expenses were too high. Not surprising given the hangar was designed to be open at both ends.

[1] https://en.m.wikipedia.org/wiki/CargoLifter

The aqua park is actually doing quite well nowadays https://www.tropical-islands.de/en/

Good to know, I always wanted to visit it. Maybe I'll do...

Seemingly the Airliner 10 is now starting production (but as always happens with this type of stuff better wait until they have actually manufactured a few, 2020 is near enough):

[1] https://en.wikipedia.org/wiki/Hybrid_Air_Vehicles_HAV_304/Ai...

[2] https://www.bbc.com/news/uk-england-beds-bucks-herts-4681015...

[3]https://www.hybridairvehicles.com/

My father actually bought quite a bit of "Cargolifter AG" stocks. Obviously they are worthless now. The guy that founded CargoLifter (Carl-Heinrich von Gablenz) is still at it and his "new" company "CL CargoLifter GmbH & Co. KGaA" actually manufacture balloon cranes much smaller than the original CargoLifter design.

Allied forces went to great lengths in creating specialized bullets to ignite hydrogen from zeppelins. The common conception of zeppelins being wildly flammable seems misplaced in this context.

https://en.wikipedia.org/wiki/Pomeroy_bullet

In my eyes zeppelin travel would be a welcome alternative to current air accommodations. In the same way I prefer taking a room on a train to air travel, I would prefer a cabin on an airship to either. If cargo can be transported, then I would expect a similar arrangement to the existing container ship passages.

In the article they talk about how the airships would be unmanned due to the risk of fire.

Which is a very shortsighted view from them IMO. An unmanned hydrogen filled airship may spare passengers and crew in case of an accident because there is none of either, but if catches fire over a stadium or a highway while carrying 5 grand pianos that wouldn't make it less deadly than the Hindenburg.

In fact, two thirds of people aboard the Hindenburg survived. Since the we had a lot more aircraft landing accidents where all passengers died in the jet fuel fire.

But on the other hand, the whole class made less than 100 flights, which makes it more than a thousand times more deadly than the 737 MAX even with two thirds surviving. So the bad reputation is not just the outcome of exceptional media coverage (I do wonder how the failure rate compares to it's fixed wing contemporaries though, they surely were quite terrible by today's standards as well)

There also weren't many people on board altogether: "Of the 36 passengers and 61 crew aboard, 13 passengers and 22 crew died, as well as one member of the ground crew." [1]

Many aeroplane disasters have involved far more people.

[1] https://en.wikipedia.org/wiki/LZ_129_Hindenburg

If the unmanned zeppelins operate some time without any such incidents, maybe they'll reconsider this aspect.

> An unmanned hydrogen filled airship may spare passengers and crew in case of an accident because there is none of either, but if catches fire over a stadium or a highway while carrying 5 grand pianos that wouldn't make it less deadly than the Hindenburg.

The riskiest bits seem to be takeoff and landing, so one should take care that those don't happen near a stadium, at the very least.

As of today, one more problem with big slow bags filled with hydrogen flying around, is also that any fool armed with a shotgun and explosive bullets, or probably even a small drone carrying a small homemade explosive charge can bring them down. In a perfect world I wouldn't even think about that eventuality, but alas this one is far from being perfect.

Fortunately, there's a lot of the Earth that's not (yet) occupied with stadia or highwaiim.

They can plan routes to avoid places like that, and most space is not populated (fields, etc.)

Compared to a landing accident with a plane an airship is safer.

I remember watching a documentary on the Hindenberg that said it was more likely that the fire was caused by the type of silver paint they used. Apparently it was very flammable.

A wild dream of mine is to build a 1/4 scale replica of an Imperial Star Destroyer that would actually be a zeppelin in disguise.

Just imagine that thing floating mightily in the sky like the actual starship from Star Wars.

You could even jump with a parachute or a wingsuit from the starfighter hangar bay.

If any zillionaire out there wants to tackle this...

Let's try maths on that! An Imperial Star Destroyer is ~1600m long, and has a volume of ~9.3e7m³ [1]. At 1/4 scale, it would be 400m long and have a volume of 9.3e7/4³ ≈ 1.45e6m³. The largest zeppelin ever made was the Hindenburg, which was 245m long and had a volume of ~2e5m³ [2].

I think your dream is unlikely to come to fruition, but zillionaire is in the right ballpark!

[1] http://bbs.stardestroyer.net/viewtopic.php?t=117422

[2] https://en.wikipedia.org/wiki/Hindenburg-class_airship

Bring on the 1/8 scale model!

Let's make it 1/8 scale, then.

Oh, that sounds like so much fun! You'd need to include externally-facing loud speakers so that you can choose to play Vader's imperial theme song upon approaching people/places.

Instead of building a star destroy you could build a full scale Zerg Overlord for much cheaper, may only require a multi millionaire.

And have the loudspeakers blare "EAAAARGH! AAEEEIIGHHH!" at regular intervals.

I've been hearing about the return of Zeppelins since the 1980s. Still hasn't happened.

> But for all their high-tech advances, Hunt said, the new airships would still get their buoyancy from hydrogen, a highly flammable gas that is 14 times lighter than air. It’s the same gas the Hindenburg and the other big zeppelins used in the 1930s.

As a reminder, the Hindenburg was originally designed for helium. They were unable to get the US to lift its ban on the export of helium under the Helium Control Act of 1927.

> As an additional bonus, Hunt said, the fuel cell would generate as a byproduct water that could be released as the craft passed over regions hit by drought.

That's isn't much amount of water, and certainly not enough to affect a drought.

Figuring 2km long x 200m x 200m that's about 3E9 mol of gas. You need some lifting gas for the vehicle weight - call it 1E9 mol or 5E8 mol of water, which is 30K tons. That's 27 acre feet, which appears to be enough for about 15 acres of potatoes for a growing season, using numbers from https://www.ardentmills.com/media/1725/colorado-quinoa-susta... .

And I think I'm highly over-estimating.

Presumably the generated water will be released immediately rather than being condensed to a holding tank, since weight is the enemy of all aircraft (c.f. airliners, which jettison condensate and "grey water" from sinks but hold the foul water from toilets). So there will be a continuous low-volume release of steam/warm water some hundreds of metres above the ground - in dry conditions it doesn't seem likely it will even reach the ground.

eesmith is right; the amount of water is utterly negligible in this context. As it happens, however, the helium airships USS Akron and USS Macon had large condensers to recover the water from the exhaust, to reduce the amount of helium needed to be vented to compensate for the reduction in fuel weight. They can be seen as vertical stripes above the propellers.

https://en.wikipedia.org/wiki/USS_Akron#/media/File:USS_Akro...

Venting hydrogen is not nearly as expensive a proposition as venting helium. Nevertheless, the Graf Zeppelin was fueled by blau gas, which has a density almost the same as air, to avoid the issue.

https://en.wikipedia.org/wiki/Blau_gas

Interesting! I guess that's cheaper/lighter than compressing the helium back to storage tanks. I remember reading that one of the "new Zeppelin" firms planned to rotate the propulsion thrusters to create a downwards thrust when berthing, I think also to reduce problems with excess buoyancy when handling cargo.

Fun fact: the original hangar at Moffett Field in Sunnyvale was built for the U.S.S. Macon.

Note that 15 acres ~= 2km x 30m, i.e. if the ship in 200m ~= 600ft tall, then the area that can be irrigated is only 1/6 of the shadow.

What would the force of the wind be on a structure 2 km long and 200 meter wide? Just a little breeze will require an amazing force just to keep the thing docked. Think that you have to maneuvre the thing into position...

It's 2+ km long when at elevation. From the paper at https://www.sciencedirect.com/science/article/pii/S259017451... :

> 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. On the other hand, balloon hydrogen carriers are not rigid and vary in size. Their volume on the ground is around seven times smaller than in the stratosphere (assuming a maximum operation height of 15 km). This is convenient because the size of the balloon hydrogen carrier on the ground is only 58% larger than the Hindenburg class airship

Well at least for now we are not running out of Helium: www.ox.ac.uk/news/2016-06-28-huge-helium-discovery-life-saving-find

But... we are. We're using it at a rate that's faster than the rate it is produced in.

Just because we find a pocket or two that we haven't found before doesn't mean that the problem is gone. The new pockets are usually more difficult to extract helium from, and storing it and transporting it is a painful process to say the least. The problem won't be truly gone until we find a way to gather it from outer space.

But still there is only a finite amount of it and with each use it disappears into the sky. It's not sustainable and not renewable so it's use must be limited and controlled if we want to leave some of it for future humanity.

Weather is the enemy of airships: three of the four large helium-filled US airships were brought down by structural damage from bad weather. Forecasting is now good enough that bad weather can probably be avoided, but airships are not fast enough to be routed around developing or fast-moving storms, so regions of unsettled weather might be off-limits for days at at time.

would it be possible for them to rise above the storm systems and thus avoid them? Or is that where the jet streams are?

I have wondered about a similar thing in the context of solar panels floating on the oceans: if the weather and the waves get too rough, just go drive to -5 meters or so to avoid damage from the waves and surface after the storm is over. But of course, salt water corrosion and growth of marine life on the panels is going to be a big problem with that

I think you miss the scale of strong storms. Updrafts and their corresponding downdrafts can commonly reach 40,000 feet with severe storms far higher than that. Many storms, especially in the central US can exceed 65MPH in forward ground motion.

I think you miss how high balloons can go. Strong storms top out at roughly 60,000 feet. Weather balloons can easily reach 100,000 feet and are often only altitude-limited by the fact that their skin is designed to burst after they reach a certain point. There's really no reason you couldn't design an airship for flight above storm conditions as long as its weight to lift ratio is kept low enough.

A balloon can be designed with excessive slack for accommodating the dramatic pressure differential between ground level and typical weather balloon altitudes, but neither airships (rigid or semi-rigid) nor blimps could ever hope to come close. Airships would fail to enclose enough volume power structural weight and blimps tailored for high altitude would fail to keep shape at lower altitudes.

Even if the problem was somehow solved for blimps, (perhaps with an internal "diving bladder" filled by compressing some of the carrying gas), their cross section at lower altitudes would be prohibitively big, making them effectively unmaneuverable. A very high altitude blimp would effectively be a one-way vehicle, it could raise as an uncontrolled balloon (then it might even be acceptable to not solve the slack issue at all), then operate as a dirigible at target altitude.

I fail to see why a blimp could not be designed in the same way as a weather balloon with a highly expandable skin. They already utilize bladders extensively. You would have to suspend your payload / drive unit below the balloon the same way a weather balloon does, but that's not a deal breaker. This seems like a materials engineering problem more than a design engineering one.

At launch, a high-altitude balloon is just a bubble of helium in a mostly-empty envelope. An airship with that much room for expansion would be enormous, even by the standards of airships.

In WW1, Germany flew some "height climber" zeppelins, which could reach 20,000 feet (still well within the range of stormy weather), but they could carry very little payload. They were also fragile, vulnerable to damage by quite ordinary weather. I think all other airships were limited to a few thousand feet, at least in practice.

Who are the people always cited as being concerned by using hydrogen, every single time there is an article on airships? Do they exist? If so, are they just contrarians we can ignore? The technology is doomed if every time someone suggests it they start by explaining why it won't explode like that incident that happened 80 years ago that your parents might remember from a Led Zeppelin album cover.

"Unlike blimps built in the last 50 years, the the suggestion is to revert to an even older technology and using hydrogen for lift, cheaper, safer and more environmentally friendly than the alternatives."

Airliners take off full of fuel. Many airliners have ended in fiery crashes. Yet we still fly in them, all the time. Myself included. We drive around in cars full of fuel, that burn, too. People even drive around in hydrogen fueled cars.

Why should Zeppelins be held to a far higher standard than airliners?

Makes me thinking: What is the total energy of a full airplane vs a Zeppelin for roughly same cargo or passenger number.

Just stubby pencil work here because I'm up at entirely the wrong hour and this might help me go back to sleep.

Envelope volume of the Goodyear blimp is ~8.5e6 liters.

Density of hydrogen at STP is ~0.09g/L. If we filled the Goodyear blimp with that we'd have ~765kg of hydrogen gas. Let's round up to cover the slight operating pressure and say we have 800kg of hydrogen.

Energy density of hydrogen is very high, 141MJ/kg. Energy density of Jet A is ~45MJ/kg.

So our hypothetical blimp has the equivalent of 2600kg of Jet A on board.

The Goodyear blimp only holds 8 passengers plus two pilots. A similarly sized jet would be the Learjet 60. It holds 3500kg of fuel.

So, most jets probably have more on takeoff and less on landing.

The Hindenburg carried around 200k m³ of hydrogen, or 18,000kg, storing 2.54 PJ of energy, or equivalent to 56,400 kg of jet fuel. A 747 can carry more than four times that (240k-ish); an A320 or 737 carries slightly more than half (25k-ish). The Hindenburg only carried some 70 passengers, though.

Whoa the Hindenburg was huge: http://thesaratogasake.blogspot.com/2010/06/big-things-again...

Also one should include the operating fuel needed to push the airship.

There is an important distinction in hydrogen fires from jet fuel ones: the moment it is released hydrogen escapes upwards, taking any fire with it. Jet fuel on the other hand tends to pool downward, while releasing its vapor (the part that actually burns) upwards. So it tends to spread fires in both directions.

So a hypothetical of a zeppelin crashing into a building might light that building on fire, but most of the hydrogen from the vehicle would escape upwards into the atmosphere without having contributed to the building's fire.

The likely answer (and perhaps this was a rhetorical question) is marketing.

Indeed - relatively few people are put off from air travel by pictures of airliners enveloped in flames, as in the recent crash at Sheremetyevo.

I once imagined a "double-bagged" airship, in which the bulk of the lift is from hydrogen held within a shell of helium. I also wondered about a non-flammable hydrogen-helium mix, but it would apparently have to be mostly helium. I would guess, however, that modern developments in strong antistatic films and hydrogen detectors would make pure-hydrogen airships safe from fire.

I thought hydrogen was mostly safe, as it inherently floats up and away.

There is a clear sustainability advantage in using hydrogen since we can produce it trivially. Helium is a very limited resource, and its the most challenging to contain due to its small size. Plus the hydrogen delivers so much more lifting force per volume that some extr mass could be used for safety measures.

A completely naïve question: Is there any chance we could get buoyancy from void if the materials are strong enough?

Don't know about the material science behind it. But from a purely physical point of view, the problem there is that void (= vacuum) does not have any pressure. So the frame would have to support itself against the atmospheric pressure instead of the gas doing it from the inside – that is a big technical challenge. The catastrophic failure scenario (hull breach) would be an implosive compression of the entire hull, which kinda sounds worse than a hydrogen-fuelled fire.

I read about this a lot a while ago, the main solution I came across was that in the diamond age when we get to that point in societal development. We'll be able to make tiny diamond bubbles with a vacuum inside, and they can be used to create airships and floating platforms. The airship doesn't have to be a single large vacuum diamond hull, but could also be made from many smaller diamonds which would help prevent a catastrophic failure. The diamond bubbles would be strong and light enough to hold the vacuum.

The wikipedia entry on "vacuum airships, as they're called," is nicely detailed. https://en.wikipedia.org/wiki/Vacuum_airship

If I remember correctly, one of Edgar Rice Burroughs' Pelucidar books involves a vacuum airship as well. His was just made of some sort of future super strong unobtainium type matterial though.

If luck was kind there might be a sweet spot making it possible to make a small lighter-than-air vaccume hull, and then add a lot of those to a craft. Something suspiciously like attaching a large number of balloons to a frame. Maybe some wonder material; carbon seems to do everything according to the headlines.

That'd solve the implosion problem since presumably all the little hulls wouldn't fail at once.

Vacuum has only around 10% (iirc) more buoyancy than hydrogen in the atmosphere, so the gains would be very minimal while the added constraints due to having such a large pressure difference would be huge.

Vacuum airships are an interesting concept but have not advantage compared to gas airships in practice.

I see at least two advantages: compared to hydrogen they are not flammable and compared to helium they don't require a limited resource.

You'd need a very heavy chamber to keep the vacuum balloon from collapsing.

Hook up a vacuum pump to a flask. It isn't going to rise as the air is pumped out. Edison's light bulbs did not float.

> You'd need a very heavy chamber to keep the vacuum balloon from collapsing.

That was my original question: is it technically feasible to make such a chamber from light enough materials (my first guess would be some carbon tubes supporting a carbon fiber tarp or something like that.

> Edison's light bulbs did not float.

One could argue that it was too small (of course I imagine making a massive lightbulb would not make for a good solid structure, also glass is heavy). A hot air balloon does not float either if you lest it too much.

This topic has been discussed for ages, but no feasible solution has been found as of yet.[1]

https://en.wikipedia.org/wiki/Vacuum_airship

It is worth noting that at a helium balloon's upper altitute, vacuum balloons would be more feasable as the air pressure allows thinner materials. Some sort of hybrid for say weather monitoring might be feasable.

Partial vacuum on a steel railroad tank car, for comparison.

https://www.invidio.us/watch?v=Zz95_VvTxZM

Vacuum airships have a long history: "First proposed by Italian Jesuit priest Francesco Lana de Terzi in 1670"[0]. The O-Boot project referenced in some replies aims to fly its first prototype on 13 December 2019 because that is the anniversary of the birth of Francesco Lana.

We'll see, but maybe it is like nuclear fusion energy - always just around the corner.

[0] https://en.wikipedia.org/wiki/Vacuum_airship

Maybe? https://www.o-boot.com/en/

"Our goal is the presentation of the first vacuum airship in history in Brescia on December 13th of this year [2019], for the anniversary of Francesco Lana, the Brescian inventor of vacuum airship, who was baptized in Brescia on December 13th 1631."

My completely uninformed guess: structures strong enough to not be collapsed by the void would be heavy to the point that the combination of void+containment would not be buoyant.

I'd try a huge sphere of polyamide aerogel, wrapped in an aluminum shell, then evacuated. If that didn't work, I'd give up immediately, because vacuum lifters are stupidly difficult when hydrogen exists.

Okay, I wouldn't give up immediately. I'd also try a vacuum onion, with multiple layers of aerogel and aluminum, with each successive layer evacuated to a different pressure.

Yes. But in general you need heavier materials to resist the external pressure (cave in), than materials that need to resist the (inwards) pressure.

In theory, completely possible. In practice, strong enough materials to hold a vacuum are too heavy and nullify the buoyancy.

From https://www.o-boot.com/en/faq/

8<-----------------------snip

6) Have you done structural calculations on the vacuum ballon yet? What material can be strong enough to withstand air pressure and light enough to rise in flight?

There are two models: a basic model and an evolution model. The first one, on which a degree research was done at the Polytechnic of Turin, is a sandwich with ceramic skins and foam in between. This model is lighter than air (obviously if emptied of inner air) and holds an external pressure (with zero internal pressure) up to 1.7 atm.

The second model should withstand a similar external pressure but be lighter and easier to build. If you want, you leave us your email, and we send you the research thesis that was made on the first model, with all the structural calculations. Unfortunately, all information regarding the second model is confidential.

8<-----------------------snip

Fingers crossed for December 13th!

I'm imagining a zeppelin that looks like a starfruit, an evacuated structural fabric over a compression frame.

A monoatomic planar fractal void of some description might work. Sarpinsky triangle or Menger sponge.

A very distant possibility.

There is real no reason to, hydrogen and helium lift approximate the same.

But yes, a vacuum lifts approximately 10% better than hydrogen.

So whatever the structure is, if filled with hydrogen or helium it'd work similar.

If you have some sort of mesh holding in a vacuum it's hard to see it's average density being less than hydrogen or helium or even air at the end of the day.

Point is, everything is possible now. A void wouldn't value add.

There alternatives to zeppelins https://en.wikipedia.org/wiki/Hybrid_airship

I wonder if it is feasible as a miniature version for cargo drones. Probably would add quite a bit of range for the cost of speed.

According to the article, these new zeppelins would be 1) huge, 2) hydrogen-filled, and 3) uncrewed and automatically piloted.

If there are any Hollywood producers reading this, I suddenly have a great idea for an action film involving maleovelent hackers and a slow moving fleet of explosive destruction.

I'm picturing extremely slow moving cinematography like in DBZ in the battle against Cell (which was stretched over weeks' worth of episodes)

Here is a BBC dramatization of Lady Grace Drummond's 1929 sensationalized first-person account (sponsored by Hearst) of an around the world trip on the Graf Zeppelin:

https://www.youtube.com/watch?v=d4jq7oRxw-g

NB, Hearst, William Randolph. Grandfather of Patty. Creater of the eponymous Castle (and a northern cousin). And inspiration of Citizen Kane.

Related: Blimp Boom or Bust? Assessing Airship Business Opportunities for Helicopter Operators > https://www.rotorandwing.com/2018/11/02/assessing-airship-bu...

“The idea would be that the whole process would be automated so that in case you have an accident, no one will be injured — only the equipment and the cargo,”

"And in other news, tragedy struck earlier today, as hundreds were killed when a cargo blimp exploded, dropping its 250 tonnes of cargo 40,000 feet into an apartment block in Chicago..."

Just don't fly over highly populated areas?

I’m sure they’ll make that rule right after!

They've been coming back for 30 years, I think I'll be excited when I see one

It is really cool I saw Airlander flying before its crash and I can almost see the Cardington Sheds from my office window.

And years ago ago I remember seeing Airship industry flying around.

Quite apart from the dangers of hydrogen, zeppelins handle bad weather only so well. The US Navy had a couple of large zeppelins in the 1920s. They used helium, but both, as I recall, were damaged and lost in storms.

The only reason to bring them back is the fancy steampunky look. From the practical side, they would be a step back.

Step back from what? A middle sized autonomous airship carrying one container, would be a huge step up from semi trucks, as it would be 2-3 times faster would not cause damage to roads, could be used in places where there are no good roads, and if thin film perovskite solar cells become reality would generate the energy needed for its flight by itself.

A standard 6m shipping container has a maximum gross weight of 30,480kg. The current Zepplin NT craft have a payload of 1,900kg and are 75m long. So it seems that quite a substantial airship might be required, e.g. a modern version of the 240m long "Hindenburg" would be able to deliver a shipping container, given that [1] quotes it as having about 20,000kg of payload capacity (including crew, passengers, food) but allowing for further weight savings with modern aero engines, etc.

[1] https://medium.com/@Jernfrost/calculating-lifting-capacity-o...

They state the dimensions in the OP: a mile and a half long at altitude, 10 times larger than the Hindenburg, payload of 20,000 tons. No, not 20,000 pounds - tons.

That's the "replace a freighter" model - I was commenting on the parent's "replace a road truck", which seems like a poorer return: since any Zeppelin is going to be inconveniently large may as well go for broke.

Yep, it only makes sense economically (and physically) if it is big enough to carry a few dozen shipping containers.

One of the new Zeppelin firms is right beside the Friedrichshafen airport, and part (all?) of their business is scenic flights. There's certainly a frisson watching a zeppelin rise into the winter sunshine with the Swiss Alps behind it; made the RyanAir flight I was waiting for seem more than usually tame.

Tame, but also quick, cheap, and safe. I'm glad I'm not an investor in such a firm, but also quietly glad that others are.

An electric Airbus Beluga will be a lot more efficient.

The thing about zeppelins is, that (party) balloons give the completely wrong intuition about things that float in air. A balloon does float quite freely and without much air resistance, but by contrast a zeppelin is a substantial piece of machinery with a lot of area to generate air resistance. Actually to the point, where it is less energy consuming to use a plane, instead of fighting against the wind.

According to the first paragraph of the article, these airships would ride the jet stream consistently traveling west-to-east across the globe thereby negating the issue of fighting against the wind. Not sure exactly how your comment relates?

How would the ship get back to the east?

I guess go all the way around. If you're not burning fuel to move, and time isn't a factor, there's no obvious downside. I would guess that a jetstream-bound airship taking the long way around would still be faster than an ocean-going container ship in most cases.

Eh, I wouldn't say that a balloon floats without much air resistance. Trying to throw one to someone else is difficult, for example.

The cheap footballs that are thin skinned - we used to call them 'flyaway' balls when I was younger. Because even those, substantially heavier than a balloon, would go off in random directions due to their susceptibility to wind from the low weight.

But actually, I've never thought of a zeppelin this way before. It gives a good intuition - but for the opposite reason you've stated, that they _do_ act kind of like balloons, and that's not what you want from a directed vehicle!

> Because even those, substantially heavier than a balloon, would go off in random directions due to their susceptibility to wind from the low weight.

Just be sure to keep in mind that while zepperlins, dirigibles and aerostats are subjected to non-negligible amounts of buoyant force due to low density, that does not make them light, nor easy to push around.

If you carry 20kt of cargo, plus the weight of the vehicle (including the weight of the lifting gas), I don't think a wind gust would blow you away, regardless of how strong it is.

Try to push around a big buoy, that gives an idea of the challenge.

Moreover, spheres are one of the aerodynamically poorest shapes (if not the most), actually worse than a flat sail. That's probably the biggest reason for Zeppelin's shape (or the rugby ball, for that matter).

Balloons are drift bodies rather than directed bodies (blimps, dirigibles). The only control is elevation, via dropping ballast, releasing gas, or application or gradual loss of heat (for hot-air / heated-gas balloons). Otherwise, it's your drag itself that's providing directional control by way of winds.

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