How to best use my hypothetical “Heavenium” for airship propulsion?

Question

The inhabitants of my Earth similar world have a preindustrial society, but have managed to create airships. These use plywood, hot air and relatively thick material for the envelope. But these inefficient craft are fully practical thanks to the recent discovery of Heavenium which can reduce the weight of these airships by up to 90%.

How can the inhabitants of my world use Heavenium to propel these airships forward? And are there any obvious inconsistencies with Heavenium?

Heavenium is a light weight red colored substance found in some rare mineral veins. It is inert and has defied all analysis. When it absorbs heat it reduces the effect of gravity in its vicinity. After sufficient heating a large quantity of Heavenium can reduce the effect of gravity in its vicinity by up to 90%.

The effect rapidly decays with distance (inverse square law) so that things more than around 10m away from it feel little effect. The gravity reduction effect lasts for many days after which the Heavenium needs to be strongly heated again.

If used to transfer potential energy into objects by moving them higher the Heavenium become discharged. The amount of discharge is directly related to the amount potential energy transferred (energy is conserved).

Answer 1

Heavenium engine

Take an ordinary water wheel. No water. Put a piece of heavenium under one side of the wheel. The side above the heavenium will become lighter, and the wheel will rotate. Use this heavenium engine to power propellers. Problem solved.

Note that the same principle can be used to power lathes, mills, mechanican looms, spinning jennies, and so on. Heavenium engines will power a fervent industrial revolution.

After the discovery of heavenium, your society won't remain preindustrial for long.

This    This
half    half
is      is
heavy   light
   _____
  /     \
 /       \
|    <>   |
 \       /
  \_____/

       ^^^^^
       heavenium

Answer 2

If you lower the heavenium underneath your gondola after you reach altitude you will start to sink and can then glide your airship if it has wings. Then raise the heavenium again to gain bouyancy and you will rise again. You can change your wings such that you glide as you rise and glide as you fall. Keep doing this and you will move forward till the heat energy is converted into kinetic energy in the atmosphere and you will have travelled.

Answer 3

Heavenium negates a force (the effects of gravity) but doesn't generate any thrust itself and so cannot be used for propulsion.

The 10m radius of effect might be difficult to work with depending on the dimensions and mass distribution of your airship and the amount needed to have the effect. For example, something the size of the Graf Zeppelin would be 236m and 33m high and would need chunks of Heavenium distributed in a 10m grid across the airframe. These chunks would vary in size depending on the mass distribution; lighter parts of the airship would only need smaller chunks. One would need to explain how these chunks in various awkward places in the airframe are accessed so they can be heated. (Looping back to propulsion briefly, it's actually a good thing that Heavenium does not generate thrust or the locations in the airframe would need to be load-bearing too.)

As for conservation of energy, it would be worth doing a quick calculation using the formula for potential energy stored by gravity and the mass of your airship to see how much energy needs to be stored. This will determine how much heat and how much time it would take to charge up the Heavenium; might take a couple of days or even a week in a kiln or something. Also, you say "If used to transfer potential energy into objects by moving them higher the Heavenium become discharged." but does the energy come back when going back down? If not, either the energy is being emitted somewhere or conservation of energy isn't true.

Answer 4

There are autonomous underwater craft which move forward by simply making themselves denser or less dense than water (by compressing or expanding an airbag). This allows them to glide, under either weight or buoyancy, with "lift" converted to forward motion by the airfoil shape of their body.

If you're willing to abandon the traditional cigar shaped envelope, you can certainly do the same in the sky with an airship, using Heavenium, by moving it forward or aft to adjust the centre of buoyancy, and angle the nose up to climb, or down to dive.

It might look a bit like a huge flying butt the Airlander, by Hybrid Air Vehicles. (image : Conde Nast Traveler)

An alternative might copy the blended wing/body concept of the AirbusZeroE, but perhaps without the redundant wingtips.

Here the point of the wing isn't to provide lift : there's no need; but to provide forward motion. You may get a lift/drag of 3 or 4 for the flying buttAirlander giving 1 km forward per 250m climbed; the blended wing may be closer to 8 or 10, giving 1km for 100 or 125m climbed.

Answer 5

Quick reality check:

The Gravitational potential energy is locally

U = mgh

This is for example valid for a stationary object in a stable gravity field. m is the mass, g is the local gravity, h is the height. (Height is relative to an arbitrary point, so that this is mostly useful for measuring differences in potential energy)

When you apply heat to your heavenium, g decreases for objects around it.

This decreases the value of U, resulting in a loss of potential energy.

The energy must be conserved, as you mentioned.

Where does the potential energy go?

Answer 6

Heavenium Jet Engine

The theory of this engine is based in the Archemidean principles, and while it would first be used by civil engineers for fountains and other waterworks) and shipwrights (of seas) it could eventually be adapted for airships.

The principle behind it is simple - a still fluid stays still because every other bit of fluid above and to the sides of it presses it down with the same force of gravity. But what would happen if we put a vertical pipe of heavenium into that fluid?

The fluid inside the pipe would get much lighter and the surrounding fluid would force it upwards, just like a piece of cork under water. And it would draw with it a new amount of fluid, which would get lighter and be forced upwards in a constant stream.

This upwards motion of fluid alone would be godsend for civil engineering - a pump with no moving parts! But that is not all - the fluid that has started flowing still has some momentum to it that can be redirected. Just put a bend in a pipe and it will now flow out sideways propelling the engine and anything that is attached to it sideways.

Air is just a form of fluid - and as boat can float on a water - so can balloon on the air. And in the same way the heavier water would force lighter water upwards - so would air.

Of course there are differences. For one - air is about thousand times less dense than water which means that it will propel the ship with much less force. On the plus side, that means that heavenium will need to be recharged less. Also air unlike water can compress, which means that to get a good flow you instead of a simple pipe you would need a much wider funnel in the intake.

Pros:

• No moving parts
• Simple construction
• Easily controlled (rudder + lid or just mount the whole thing on a swivel)
• Useful in other applications (lower cost and quicker R&D)

Cons:

• Very low thrust in the air
• Difficult to recharge

Possible improvements (possibly incompatible):

• Replace the Heveanium funnel with ordinary funnel + Heveanium mesh on the intake for better pressure profile and efficiency
• Place re-loadable heaveanium bunker above the funnel for easier refuelling
• Add access and fittings for in-place recharging - e.g. burning a breazier of coal right below the funnel

Answer 7

1. I don't see any obvious logical inconsistencies with the concept of heavenium itself. It's like hydrogen only better at lifting: if it's a solid, it can easily be attached to the airship, or anything else people wish to lift up.
2. Given your description of heavenium as a countergravitational substance, I don't see how it can be used for lateral movement. I think your aerogators will still need some kind of motive force, a fan of some kind, or sails, to actually propel their ships forward.

Answer 8

Heavenium violates the Second Law of Thermodynamics. You don't need fuel.

What?

The second law of thermodynamics states that the total entropy of an isolated system can never decrease over time, and is constant if and only if all processes are reversible. Isolated systems spontaneously evolve towards thermodynamic equilibrium, the state with maximum entropy.

[…] In all processes that occur, including spontaneous processes, the total entropy of the system and its surroundings increases and the process is irreversible in the thermodynamic sense. The increase in entropy accounts for the irreversibility of natural processes, and the asymmetry between future and past. […]

[…] Its first formulation is credited to the French scientist Sadi Carnot, who in 1824 showed that there is an upper limit to the efficiency of conversion of heat to work in a heat engine. This aspect of the second law is often named after Carnot. — Wikipedia, used under CC BY-SA 3.0

Why?

All processes that require heat are either entropic in nature (e.g. cooking), or actually require a temperature difference (e.g. Sterling engines, solar panels). All natural processes that extract useful energy (aka do work) from a temperature difference also reduce that temperature difference. In short: without access to sunlight and the vacuum of space, you'll run out of usable energy sooner or later.

Heavenium, however, works on absolute temperature, like entropic processes, but provides useful work, which you can normally only get from a temperature gradient. It's a negentropy source. This stuff's worth more than the Sun.

How?

There are countless ways of making use of this, but I'll start with the simplest to explain.

Heat pump in a box

Make a pulley. One end of the pulley should be a box containing some fancy technology and some Heavenium (I'll get to that in a sec); the other should be weighted so that it goes up when the Heavenium is “off” and down when the Heavenium is “on”. Attach the pulley to a really tall tower.

In the box, wind up some clockwork, and attach it to a heat pump. Set the heat pump so that it'll warm up a compartment containing Heavenium and cool down a compartment containing hot water, then start it going and shut the box. The Heavenium box will go up. Use some of this energy to do work (e.g. winding up some more clockwork). Eventually your clockwork will run out, or your heat pump won't be powerful enough to heat the Heavenium to the critical threshold any more, and the Heavenium will run out of magical lifting ability; you know when this will happen in advance, thanks to your calculations, so you can switch to generating energy from the pulley going the other way.

If you use a Sterling engine to recover the energy from the temperature gradient the heat pump made, you will have:

• Cold water, and a cold box in general; and
• More energy stored in clockwork / used to do useful work than you started with.

With a sufficiently-powerful heat pump, you could start with regular old ambient-temperature water, cool it down, and generate energy for useful work. Of course, eventually, this energy would run out; friction and other losses would see it slowly lost to heat. But you can extract work from heat.

Your airship does not need fuel.

Heavenium engine

Okay, so maybe building a massive tower in the middle of your airship isn't actually all that practical. You need something more engine-like. Take a heavy flywheel, and put it vertically over a well-insulated Heavenium-containing oven (so that the rising side is lighter); insulation reduces the maximum power your heat pump system needs to have to get the Heavenium hot enough. (Frictional losses aren't all that important because a Heavenium engine uses heat as fuel – I still can't get over how overpowered this is!) Fuel this oven with a powerful heat pump (or chain of heat pumps) powered by the Heavenium engine. The energy will eventually get back to the heat pump no matter what you do, but you can speed it along by sticking the “cool” end(s) of the heat pump on whatever's generating most of the frictional losses.

Now simply heat up the oven to the critical temperature, spin the engine a bit to get it started, stick a fan on the end and you're away!

When?

Heat engines have been known since antiquity. The first refrigerator (requiring pretty good heat pumps) predates the industrial revolution by over 75 years. While this technology might not be immediately apparent, since the Second Law of Thermodynamics hadn't been invented yet, anyone who understood fridges and had heard of Heavenium would probably be able to figure it out, and it wouldn't take much longer to develop heat pumps good enough that this would be viable.

Unless, of course, you need to get the Heavenium really hot. Then this is right out.

Answer 9

I can see a problem with Heavenium - at best it only reduces mass to 90% of normal. What this means is a 20 ton airship will plummet out of the sky just as quickly as a 2 ton brick. To overcome this, you suggested hot air to provide lift. So your airship will need to carry a source of heat aloft, which will also require its own fuel. BUT ... all this adds even more weight to your airship.

At first, one would imagine having a crew shovelling wood or coal into a fire which heats the Heavenium with the waste heat being used to lift the now lighter airship. You could have a turbine in your chimney, turning a propeller through a gear mechanism to provide forward thrust. So while the Heavenium itself is not providing thrust, the thrust is generated as a byproduct of the means to lift the airship and heat the Heavenium. Later developments could have more efficient heat sources - gasoline, electricity, nuclear power; jet engines to provide thrust and drive turbines; helium to provide lift (not hydrogen, as it doesn't behave well with flames!); lightweight metals replacing plywood; and so on.

As your airships get larger, you could pump liquified Heavenium around your airship (if the stuff ever melts?), or just pump the heat around your airship heating lumps of Heavenium strategically placed around the structure.

However, there is going to be some tricky balancing between the weight of your airship (structure, fuel, cargo, passengers, etc), the weight reduction properties of Heavenium, the amount of lift provided by hot air/helium, and the air density as it varies with altitude/weather.

Answer 10

Heavenium heat engine

Take a Bhāskara's wheel filled with half Heavenium, half water. Put heat in one rotating side, left other side to lose heat to air. You will have rotacional force generated in place. A little coal could make you very far.

See Renewable Energy from Evaporating Water for inspiration.

Bonus: You can use the residual heat to keep the lifting Heavenium warm.

Answer 11

There are several subtle implications in your "Heavenium":

• how efficient is the heat conversion in potential energy (i.e.: how fast will it discharge when "pushing up")? If efficiency is comparable with steam engines then it's mostly useless as "engine", while retaining it's full power as "keep height" device.
• "perpetual motion spinning engines" as described in other need to be heavy to generate a sizable amount of energy and thus are a bit useless for aircraft motion.
• It's unclear how do you plan to regulate ascent/descent of your aircraft and I assume it is "normal" Archimedes law (corrected with gravity, and thus weight, reduction).
• If the above it's true then "airships" need to be huge to leverage on a certain amount of air weight. This, incidentally, means they will have a large cross-surface winds will act on.
• What happens, exactly, when Heavenium is "discharged"? I will assume it gradually looses it's "power" and thus the nominal "90% reduction" will steadily and gradually decrease as the airship rises up.
• If you want to be "creative" you can make your airship large and flattish and "power" it with two (or more) Heavenium capsules: one near "forward end" and the other near "aft end".
  • start with airship at equilibrium with 80% Heavenium charge (~70% gravity reduction).
  • heat up forward capsule and ship will start raising "nose first". This will cause a forward drag because of ship geometry.
  • heat aft capsule "just enough" to maintain it's power as ship raises.
  • stop heating forward capsule; this will cause a brief "overshoot" (mass is not affected, so airship has a rather large inertia) and then it will start falling, again "nose first" (if aft crew did their job right) and thus, again, producing a forward drag.
  • rinse and repeat: you ll'have a big flat "whale" moving slowly and steadily (in calm air).
• Heavenium (as described) cannot be used directly to produce horizontal (orthogonal to gravity force) drag.
• You can't either use any kind of "sails" because those rely on keel drag, which you don't have.