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In a pre-17th century world without gunpowder, can rockets still be developed? Could you perhaps make a naphtha rocket?

RP1 is made from highly refined kerosene, which has been about since at least the 9th century. It makes me wonder if it might be possible to synthesize some kerosene based rocket fuel in the fast, suitable for military rocket artillery.

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  • $\begingroup$ A liquid fuel rocket needs liquid oxygen (or some other, much nastier, liquid oxidizer) and centrifugal pumps. A civilization capable of making them is hardly "pre-modern". (Plus I am curious how small can one make a liquid-fuel rocket, even with modern technology. Liquids start to misbehave when flowing to conduits with small cross-sections.) $\endgroup$ – AlexP Dec 23 '20 at 8:41
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    $\begingroup$ NO need for a pump, pressure and gravity-fed plumbing suffices. And Hydrogen peroxide instead of Liquid Oxygen. Still a very hairy deal, and likely outside of their engineering abilities, but not inconceivable. As for size: look at Goddard's early rocket. 4 ounces of fuel. That small enough? $\endgroup$ – PcMan Dec 23 '20 at 9:31
  • $\begingroup$ Why rocket artillery? Could you define rocket and what you want to do with it? A weapon always has a specific purpose and application. We're talking before the dawn of mass production. They had perfectly suitable weapons back then that killed more % of the population than in any time period in europe. I don't see the tactical advantage of modern rocket artillery and nothing else. You get 5 shots, spend all your money in development and then lose because your mercenaries will no longer get paid. You won't have positions to bombard even. Reach them before they reach you? With what? $\endgroup$ – Raditz_35 Dec 23 '20 at 11:17
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    $\begingroup$ The real trick with most military ordnance is making sure it survives the depot mishandling, improper storage, occasionally being dropped, and then the long bumpy, rainy, dirty, hot trip to the battlefield, all without prematurely igniting or detonating...and then still works as intended in battle. $\endgroup$ – user535733 Dec 23 '20 at 11:20
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    $\begingroup$ @AlexP "Plus I am curious how small can one make a liquid-fuel rocket, even with modern technology." About twenty years ago, you could buy a liquid bipropellant rocket motor -- nitrous oxide and ethanol, pressure fed, ethanol tank piston pressurized by the nitrous -- that was about 1.5 inches diameter, 18 inches long, including propellant tanks. Mail order. Denatured from the hardware store, nitrous from a speed shop. $\endgroup$ – Zeiss Ikon Dec 23 '20 at 17:59
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There is an alternate solid rocket fuel system that was available in (late) medieval times. It was very commonly used in the first generations of "amateur rocketry" by people who wanted something more DIY than buying an Estes pre-made motor and installing it in a kit-built model.

That alternative is zinc and sulfur.

Sulfur, in high purity, forms naturally as "flowers of sulfur" around volcanic steam vents (Mt. Aetna and Vesuvius both have fields of such vents, from pre-Roman times to the present). It's easy to reprocess into powder form.

Zinc was first produced around 1400, in India, by heating calamine with wool (though I know of no reason charcoal or other carbon source wouldn't work as well). It is also easily reprocessed into fine granules.

A correctly proportioned mixture of the two powders can be loaded into a strong tube (seamless steel tubing was commonly used in amateur rocketry in the 1950s to 1960s, but it should be possible to make a bronze tube that would hold the pressure as long as the nozzle isn't too restrictive), either compacted by vibration or pressed (the sulfur will bind together to form a porous solid composition). When ignited, the mix burns very rapidly, produce a short period of very high thrust.

Zinc/sulfur is less efficient than gunpowder as a rocket mix, but it would be accessible in a world that never learned to extract nitrates or chlorates. It's hazardous to make and handle (don't try this at home!), but so is gunpowder, or any other solid rocket fuel prior to the 1960s (when ammonium perchlorate and synthetic rubber propellants came along). And it's readily available, with some hand-waving, as early as Roman times (calamine has been around for ages -- the discovery of its reduction was probably an accident).

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  • $\begingroup$ Thanks, Zeiss! While I like PcMan's idea, and want to explore it further, this seems ideal in its simplicity and history, since I could look up modern zinc-sulfur rockets to judge their effectiveness. From the sounds of it, the fuel would not be expensive to produce (though maybe still more costly than gunpowder). Out of curiosity, I'd like to ask what you think of Ash's answer's feasibility, as he mentioned several interesting possibilities. Thank you again, Zeiss, I really appreciate your input. $\endgroup$ – Johnny Dec 24 '20 at 3:13
  • $\begingroup$ The only liquid oxidizer that might be possible in medieval times is nitric acid. Alchemists were making that by 1300 CE. Concentrating it enough to use in rockets is another issue (concentrated sulfuric acid is the best dessicant, but it's also had/hazardous to make/handle). Having tanks and tubing that it won't eat is yet another. Even in the 1920s Goddard chose liquid air, and later liquid oxygen, as easier and safer than nitric acid, even though he had to make liquid air, vs. buying con. nitric acid. $\endgroup$ – Zeiss Ikon Dec 25 '20 at 20:03
  • $\begingroup$ That makes things really hard for liquid rocket fuel. If they did have liquid oxygen, would this help matters? In the other comments, you made it sound like even with hydrogen peroxide or liquid oxygen, the construction of a liquid-fuel rocket would be a lot of work and prone to material failure. Thanks again, I really appreciate your insight. $\endgroup$ – Johnny Dec 26 '20 at 0:30
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Yes. Lots of alternate fuel/oxidiser combinations are possible.

You didnt specify a minimum range or impulse or delta v. So while it's going to be mightily hard to reach orbit using pre-17th century tech, you could definitely build a rocket of some form.

(It may only get 100m up in the air. But it will be a rocket)

Fuels:

  • Methanol or ethanol. Made using stills.
  • Methane. Captured from garbage or livestock.
  • Sucrose. A toffee or similar solid sugar.
  • Partially refined oil products, eg kerosene, lamp oil. Perhaps also whales oil.

You have a few choices of oxidiser:

  • nitric acid.
  • hydrogen peroxide.
  • if you feel like giving them refrigeration tech then liquid oxygen obviously, but this is a bit of a stretch so probably not going to happen.

You also have pressure vessel options that do not involve combustion. For example capturing high pressure steam from a boiler, and then directing that steam through a nozzle. Unlikely to scale up to orbital heights on an earth like planet, but will act like a rocket.

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    $\begingroup$ I think this is more of a theoretical approach. Oxidizer + fuel = rocket. You haven't convinced me that this would actually work. Handling those inefficient chemicals in the past, well, you make it sound so simple... $\endgroup$ – Raditz_35 Dec 23 '20 at 11:13
  • $\begingroup$ Hey Ash, thanks for giving me so many possibilities! I was considering giving the setting some kind of magical dry ice so they could make cryogenic alcohol which they could use to make liquid oxygen. Though, if hydrogen peroxide is a possibility, it might be simpler? A steam rocket would be very interesting, and they did have some of those during WW2, powered by a ship's engine. Raditz did bring up concerns that these rockets wouldn't be mechanically possible in the past, so I'd like to ask, do you think it is possible to create these with pre-modern technology? Thanks again! $\endgroup$ – Johnny Dec 24 '20 at 3:18
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Naphta: Not on its own: And not easily.

A rocket works by rapid creating a large volume of gas, and expelling it in one direction, thus gaining thrust in the opposite direction.

The creation of this gas usually involves a Fuel, and an Oxidizer burning together.

In the case of gunpowder, this fuel (charcoal) and oxydizer(saltpeter) is pre-mixed, along with some other stuff to facilitate ignition and smooth burning.

Naphta is a most excellent fuel for a rocket, but it lacks a suitable oxidizer. Yes, it can burn with the Oxygen in air, but now you are trying to burn a liquid with a gas, to form a controlled explosion. Very possible, it is exactly what any airliner does, but not easily achievable without some very complicated machinery.

Mixing it with a solid oxidizer is just not on. Yes making a clay-like mixture of Naphta and Saltpeter, or Naphta and Ammonium nitrate makes a very nice explosion, but not a contained explosion. You have basically invented an unstable form of dynamite.

The only remaining option is to make your Naphta rocket with a liquid oxidizer. Specifically Hydrogen Peroxide.
In our history Hydrogen Peroxide was only discovered in 1818, but the manufacture of the substance is not that exotic, and it is very likely alchemists of the 1200's did discover it, they just had no clue what to do with it. One can also reasonably easily (but very inefficiently!) make Hydrogen Peroxide if you have any form of electrical battery to perform electrolysis.

OK. Now you have your Naphta, and you have your Hydrogen peroxide.
You just need to mix the two liquids together in a strong enough combustion chamber, put a suitable nozzle on it, and you have a rocket. The liquids can be pressure-fed from their tanks, so no worry about fancy pumps or anything.

This would make a rocket using 1200's tech.
A very, very expensive rocket. Not at all suitable for mass production, and too unsafe/unstable for broad military use.

p.s. You would get an even better rocket by using concentrated Nitric Acid as your oxydizer.. But that stuff is *nasty to handle, even with modern tools.

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  • $\begingroup$ Making a pressure tank for a liquid fuel or oxidizer may not be easier than making a centrifugal pump... (And making pure hydrogen peroxide is not at all easy.) $\endgroup$ – AlexP Dec 23 '20 at 9:32
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    $\begingroup$ @AlexP Be serious please. A simple glass container, pressurised to about 2 bar, is ample. The romans could do that! $\endgroup$ – PcMan Dec 23 '20 at 9:35
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    $\begingroup$ @PcMan Your combustion chamber pressure can't be even equal to your feed pressure -- there's always some drop across the injectors. And the lower the pressure, the less thrust you get from the engine. An engine running at or barely above atmospheric pressure will have next to no thrust -- it's more like a torch than a rocket. Practically, you need at least about 20 bar chamber pressure to make a rocket that can lift itself and its fuel supply, which means your fuel tank has to hold 30 bar or so. $\endgroup$ – Zeiss Ikon Dec 23 '20 at 13:42
  • $\begingroup$ @ZeissIkon Building up 30 bar of pressure shouldn't be too hard, as a bicycle pump can get up to about 150 bar? Or perhaps I've misunderstood the problem? Thank you for the useful information. $\endgroup$ – Johnny Dec 24 '20 at 2:52
  • $\begingroup$ @Johnny 1 bar = 1 atmosphere = about 101 kPa = 14.7 psi. A bicycle pump can get to around 10 bar if you're big enough. Similar pumps with different design choices can get to 200 bar, but it's a huge amount of work and takes a very long time. Meanwhile, 30 atm is a bunch for a bronze propellant tank, and steel was pretty haphazard before the 18th century. $\endgroup$ – Zeiss Ikon Dec 25 '20 at 19:58

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