Antiballast for flying ship

Question

Your miners find some strange stones - they float to the ceiling of mines.

With those stones you can easily build an airship - just fill a sleek wooden hull with them and give the rowers some wing-paddles.

With a drag coefficient ~0.02, even under muscle power you can get some tens km/h, also you can use favorable wind.

Now you have one problem - there is no way to regulate lifting power. If you let the floating stone go it will go straight to space.

And the ship is constantly losing weight as rowers consume food and water. Also accidents happen - a paddle gets dropped, a rower goes overboard, some barrel gets broken and spills wine. Or you want to drop some flechettes on enemies' heads. And rowers can provide only so much thrust downwards...

You can just let some stones go - but they are very expensive. You can gather rainwater or dew from clouds - but that depends on weather.

Dropping ballast allows you to make the ship lighter. But you need antiballast - a way to make ship heavier in the middle of flight.

So what is an optimal way to increase the weight of, say, a 10 ton ship by at least 100 kg - I guess some reaction to bind oxygen or vapor that is accessible without industrial technology?

Update.

Compression of air is not a very optimal way to do it. Even with modern technology, a balloon weights several times more than air it contains. For preindustial one ratio would be order of magnitude worse.

Likewise, cool air - suppose we have a 10 ton 100 m3 airship with 300K on inside. If we cool it even to -70C then we would get about -30 kg, less than weight of adult. And making the ship bigger would increase drag and make it too slow under manual power.

Answer 1

Volume-based Adjustable Buoyancy

The key here is to not use so many stones that your ships float up. Instead, use as many stones as is needed to make your ship effectively weightless. If 1kg of floating stone(determined by upside-down scale) makes 1kg of normal matter weightless(not falling, not rising)(just guessing, you've left little as far as hard numbers are concerned) then 2.5tons of a 5ton ship will need to consist entirely of floating stone

Doing so will make it possible for you to use an already tried-and-true method of altitude adjustment, namely a hot air balloon of some sort, whose own volume and lift will determine whether the whole of the ship goes up or down. As crew and cargo is loaded the weightless ship will naturally increase in weight and drop/sink, but with the ship's weight itself being accounted for by the floating stone matter you should be able to get away with relying on the balloon alone for lifting both crew and cargo, with the burners supplying the heated air and their fuel being the prime determiner of how far/long a ship can go without getting landlocked(unable to float) and may provide a nice niche for the economy to flourish in. They can also land and have the crew chop some wood for fuel instead of using coal if they're desperate.

Alternatively

You could still go with the weightless ship tactic and do a small amount of hand-waving to say that they've discovered a way to use wooden gears + wooden fanblades + manpower to produce a primitive propeller and engine of sorts whose constant additional lift in addition to the lift from the floating stone provides enough power to move/lift the ship along with its crew and cargo, with going down being as simple as telling the crank crew to slow down the cranking of their cranks(the cranks in this case having replaced the function of oars, with part of the crew being in charge of ship lift and the rest being in charge of ship thrust(if you want a sail-less option or the wind is against you))

Answer 2

Harvest extra ballast water from clouds.

The Graf Zeppelin did this in real life during the 1930s. A set of gutters on the side of the vessel collected the water. The airship brushed against the edge of a cloud or light rain to harvest the water.

In real life, opportunities to do this were somewhat uncommon and irregular -- weather can be unpredictable. Trip planning never counted upon rainwater collection; it was a bonus that conserved expensive hydrogen. But perhaps conditions are slightly more favorable on your world.

(Oh, don't dive into the cloud or rain. The zeppelin officers, mostly veterans of WWI who had lived through hydrogen fires and airship crashes and faced down incendiary machine guns and the bitter North Sea, who had navigated into combat by guesswork upon cloudy nights and seen most of their comrades die...those adrenaline-addicted adventurers considered diving INTO a cloud or rain far too risky to attempt.)

Answer 3

Build a chain which incorporates some of the floating material. The resulting chain will be "weightless" and can therefore be of arbitrary length - instead of ultimately ripping under its own weight.

Whenever you need more weight, lower a few people down to the ground, let them shovel some dirt into a container and pull everything back up.

Answer 4

The stones are expensive, so you dont add so many that the ship becomes weightless.

You essentially build a Heavier-Than-Air airship. It will naturally float down if nothing is done, but by the use of wing surfaces, fans, propellors and even oars designed as fans you can gain the lift required to gain altitude (use only one or a combination).

Answer 5

All matter has mass. The stones are in the mountain because when the mountain was molten, and the material comprising the stones was still there, they did not float away into space.

There is a material in the real world called "sol-gel foam" that is really a very sparse ceramic mesh. Folks have pulled vacuum on it, and coated it in plastic, and it is positively buoyant in air. It is lighter than sea-level air; it acts a lot like helium. It does not repel from normal matter, and wouldn't float all the way up to outer space. It would find its level and try to float there.

A submarine can make itself more dense, and sink, by taking in mass. An airship could take on air, and compress it, and gain mass, and therefore weight, and adjust buoyancy in that manner. There would still be a "local density" based on pressure and temperature to determine how much lift the material provides. (descriptive link)

A hot air balloon gets lower density by heating up air. (descriptive link) If you want more density, then cool it off. You could have cryogen canisters to make "anti-balloons" that pull the ship down. You could also get mileage with propellers.

The Hero-style steam engine (greek) suggests ancient Greek steampunk was wanting a Newton. In your story, you could supply one. Imagine Alexander the great with a railroad, or decent gatling guns. They could also have Da Vinci style air-screws, or necro-robotic wings. Spiders aren't the only Arthropods, so you could have trilobites, butterflies, scorpions, centipedes, and crabs as candidate articulators. The Meganeura Meganisoptera/dragonfly had a wingspan of 2-feet, suggesting insects that operate at least in the envelope of modern birds.

A fun feature of aerogels is they are superb insulators. You would not get a Hindenberg Zeppelin event there. You could bounce flares off it all day long.

Bibliography:

• Necro-robotic articulators at Rice (link).
• Lightweight/buoyant aerogels (have air inside) (link, link)

Answer 6

I'm surprised that nobody else has suggested this. Don't rely 100% on floatium for your buoyancy. Have a hot air balloon that takes your ship over the threshold. You don't need huge blimp-sized balloons with this solution. You can probably get away with one smaller than the ship itself. You just need one big enough to compensate for your live load: the passengers, cargo, etc. that you don't keep on the ship most of the time.

It occurs to me that you would need floatium pallets with the cargo, regardless, because otherwise the ship wouldn't be able to stay on the ground when unloaded.

This connundrum will actually make it difficult to create floatium war ships. Every time you fire a cannonball, you'd have to adjust your buoyancy to match.

Answer 7

Heat the stones. Whatever handwavium takes place to make the stones generate antigravity is reduced when the stones are heated. The Handwavium returns as the stones cool.

Bonus, that is why the stone is so rare. Most of the stones have "evaporated" from the planet because during the formation of the planet if they were near the surface and cooled they just floated away.

Answer 8

I guess we could use reaction of slaked lime with carbon dioxide.

Ca(OH)2 + CO2 → CaCO3 + H2O

But to get 1 kg of weight this way we would need to pass at least 3 ton of air through lime-water. Water vapor loss could negate the effect.

Another way would be to corrode iron fillings

4 Fe + 3 O2 + 6 H2O → 4 Fe3+ + 12 OH− → 4 Fe(OH)3 or 4 FeO(OH) + 4 H2O

But it is hard to do it fast, especially if we do not add water. And if we add water then efficiency is only 29%.

Burning steel wool is fast and efficient, but it was invented in 1896, so it could be hard to produce it in pre-industrial times. Same for burning magnesium.

I guess burning iron fillings / lead, antimony or arsenic is the best option.

Answer 9

1. How about using guide ropes?

They pretty much self-regulate to a great extent.

https://en.wiktionary.org/wiki/guide_rope

2. Make the whole thing a hot air balloon.

Your magic stones will make it extremely efficient, requiring 2% or 5% of the lift to be hot air. This will make your aerodynamics much better than a traditional hot air balloon, but you can still release the hot air to an extent or simply turn down the fire and sink to the ground.

Of course, you are free to combine both technologies.

Answer 10

Ordinary, unheated air.

At jet cruising altitude, outside air is -40 C to -70 C = 203 to 233 K. Comfortable cabin air = 298 K. 218/298 = 73%. Air inside cabin weighs more than 1/4 less than outside air.

Turn off heat. Open all windows. Wear coats - optional, rowing is hard work. Wear oxygen masks - not optional. (Alchemy? Recover from burnt steel wool? Does this planet have nitrogen atmosphere?) Assuming penteconter construction, 30 m x 4 m x 3 m = 360 000 L = 15 000 mol = 470 000 g x 0.37 = 170 kg of mass enters through open windows.

Answer 11

Birds

Dump some bird seed on the deck and play some territorial bird calls. Suddenly every bird in a kilometer radius has landed on your air ship and is weighing it down. You will have to be very careful not to startle the birds though because after they finish eating your bird seed they may take off again making your ship even lighter than it was. But hopefully they can weigh you down enough that you can hook onto a tree or something-- giving your crew the opportunity to go out and secure more bird seed for future landings. If you do this frequently enough maybe flocks of birds start following your ship around waiting for you to give the signal that you're about to dish out more food.

Answer 12

Reduce lift by using a tethered "balloon" to temporarily eliminate the lift of the stones.

Simply throwing the stones overboard is not feasible due to their cost, but you can throw them overboard if you have a means of retrieving them. Store your lift stones in a crate attached to deck via a long rope wrapped around a winch. In the static configuration, the crate provides lift to the ship. By releasing the winch, however, the stones lift the crate alone, and provide no lift at all to the ship. As long as the rope unspools, the ship will descend, although you'll be in the exact same situation of "too much lift" when the rope is completely unspooled. You just need a rope long enough to allow the ship to descend to the ground, at which point it can be tethered down, allowing the winch to be spooled back up.

This wouldn't be well-suited to continuous fine adjustment of the amount of lift, since it only provides a temporary reduction in lift force, and requires landing to actually change the balance of the ship. It could be useful as an emergency measure, however, similar to how a submarine can surface in an emergency by blowing the ballast tanks. This is effectively the opposite, allowing the airship to descend rapidly in an emergency, and mitigates the cost of doing so by allowing the lift stones to be recovered.

Answer 13

Those stones don't "float" (which just means they are less dense than the surrounding medium, and that there's a maximum service ceiling). No, these are really weird stones: the provide a constant, directed force without requiring power. If directed upwards, they start rising, until the cave ceiling stops them. If directed downwards, they start descending (faster than with just gravity), until the floor stops them.

So the solution is to mount them to your ship on a turnable bearing. Mount them in pairs that turn in opposite directions - when you point them at each other, the force cancels out, and gravity takes over.

Answer 14

This also seems to depend on how the floating 'mechanism' of the stones work.

If for instance they work (similarly) like magnets, they are not floating but actually repelling the magnetic field of your world: 100 stones in/attached_to your 'airship' makes it float up. using electric currents through your stones will disrupt their own field rendering them innate.

Want to get down -> add a current to more stones. Want to float up more -> release stones from a current.

But! This solely depends on what level of technology/science is present in your world. If it is known how the stones float, you can tinker around with a way to suppressing that effect without destroying the stones, it could be an electoral current as in my example, or maybe a chemical reversable reaction with the stones, maybe the effect is stronger or weaker based on temperature.

Answer 15

Use a large stone tethered to a long cable spool on a drum. Release the drum and allow the airship to drop whilst the stone rises. Just before the stone reaches the end of the tether release large hinged flaps that drop down to increase the surface area of the ship.

When the stone reaches the top of the tether the ship receives a big pull upward, but a lot of the energy of the upward pull is wasted against the increased air resistance of the flaps. As the ship starts to rise lower the stone on the tether with the flaps out then pull the flaps in and release the stone again.

Answer 16

According to good ol Wikipedia, silica gel has been around since the 1640s, and was used in WWI to absorb vapors in gas masks. (https://en.wikipedia.org/wiki/Silica_gel) It can absorb about 40% of its weight in water without changing their size. This moisture is released when the gel is heated up.

Hydrogel crystals can absorb anywhere from 500 to 1500 times their weight in water (https://www.nature-and-garden.com/gardening/hydrogel.html), and can be made from starch, cellulose, or petroleum. I am not sure if each of these require industrial technology for production.

Another potential solution could be a basket filled with absorbing fibers. The dry basket could be lowered into a lake, river, or ocean to absorb water and then be hauled aboard with the added water weight. Heck, even the bucket could work without the fiber. A gallon of water weighs around 8.3 lbs./3.78 kg. A 15-gallon bucket of water would weigh around 125 lbs. A 50-gallon bucket would weigh around 415 lbs./204 kg. Winch down a bucket, and pull up the water needed to increase your weight.

Adding a source of cold, such as blocks of ice, would cause condensation from the air to form. This could provide a source of additional water without needing to fly through clouds. The ice could be kept insulated until it was needed for condensation capture. There are Dew Point Calculators (https://www.calculator.net/dew-point-calculator.html?airtemperature=70&airtemperatureunit=fahrenheit&humidity=40&dewpoint=&dewpointunit=fahrenheit&x=92&y=23) which are helpful in determining the temperature difference needed to cause condensation to form based on the relative humidity level. The rate of condensation formation is based on the amount of airflow around the condensation point, and the relative humidity in the air. I was not able to find any good calculations for the rate, likely due to the complexity of the subject.

You might be able to do some experiments where you weigh ice cubes before and after they melt while in front of a fan. If you know the relative humidity inside your house, you can time the rate at which the water increased in weight by dividing it by the time it took for the ice to melt. Be sure to include any condensation on the outside of the container as well. “End weight – start weight / time”. It would be a rough estimate, but if there is a lack of a true formula for calculating the condensation rate, nobody will be able to argue.

It would be nice to know if the stones are simply lighter than most other substances or exhibiting anti-gravity properties. If they are simply lighter, then there would be an altitude zone where these stones would hover with neutral buoyancy. As the number of stones in the upper atmosphere increased over time, they could cause global cooling. If they exhibited anti-gravity, then they would leave orbit and head towards deep space.

Answer 17

Aerodynamics can handle this, like blimps do using the lift of their elongated body and tail control surfaces.

If using pre industrial technology, wood and fabric windmills-like propellers, wooden gears and pulleys, wooden shafts, leather belts, powered by arms or legs, could allow to give a vehicle the required speed to be aerodynamically controlled. This vehicle does not need a baloon or enveloppe, just horizontal and vertical surfaces, and a cabin for people to do fitness.

The vehicle has to be slightly heavier than what the stones can lift, the rest is aerodynamic human powered lift.

Answer 18

Floatium is contained in a rotating drum

Depending how much negative force the Floatium induces (does it rise inverse to gravity?) a drum rotated by sailors can be used to induce a tumble effect and "toss" the Floatium and losing contact with the barrel surface. While the Floatium is out of contact with the drums surface and in the "dead space", it's upward force isn't applied to the ship.

1. Barrel rotates
2. Floatium loses rotational momentum and rises
3. Floatium out of contact with surface

These barrels would need to be used in counter-rotating pairs so not to impart roll.