Science/history challenge: Beat Sputnick

[peadar1987]

1 hour ago, sevenperforce said:

Yeah, that's basically what I was thinking as well.

You might be able to get liquid N₂O or high-test hydrogen peroxide as a liquid oxidizer to help your ISP a bit. Coal dust is one potential fuel; you could also mix in a variety of metals to increase energy. Clockwork-separated staging isn't necessary if you can rig an explosive charge to fire and separate stages once the lower stage burns out (e.g., by having one of the lower stages burn through its own upper cap and ignite the charge).

Definitely a lot of stages.

In this design, I'm guessing that the limiting factor would either be the temperature/ablation resistance of the nozzle, or the pressure-bearing capacity of your body.

Yeah you wouldn't have much pressure resistance, either from the nozzle or the body. I think you'd have to have lots and lots of short-burning, small stages, to limit temperatures and pressures, which would push up the non-fuel fraction of the rocket even more.

[sevenperforce]

2 minutes ago, peadar1987 said:

Yeah you wouldn't have much pressure resistance, either from the nozzle or the body. I think you'd have to have lots and lots of short-burning, small stages, to limit temperatures and pressures, which would push up the non-fuel fraction of the rocket even more.

Wood can actually have pretty descent structural integrity under temperature loads. It's a really good insulator, so even if the outside is on fire, the inside can still support high loading.

Since you expect the rocket to burn up anyway, you can construct a sturdy internally-trussed cylindrical framework out of wooden beams, nail the thinnest metal you can manufacture to the outside, and then wrap it in high-tensile strength wire/cord at intervals. There's your SRB. All you need is a nozzle.

[wumpus]

1 hour ago, peadar1987 said:

Let's face it, you're not going to build a liquid fuelled rocket in Roman times. You just aren't. It would take tens of thousands of trained people. Industries that wouldn't yet exist. Probably centuries of development.

If I had to do it, the best way would be and OTRAG sort of affair. Solid rocket motors using Saltpetre as an oxidiser, mixed with something like coal dust as your fuel. Make a nozzle out of clay. Your ISp would be lousy so you'd have to have a big, multistaged design, set up with clockwork to separate the stages. Set it up so it reached orbit passively. Try lots of times, fail lots of times, hopefully eventually get a payload to orbit, but I wouldn't fancy my chances.

This is pretty much it.  Going liquid fueled means either pressure fed or turbopumps.  Going turbopumps pretty much means 20th century, and pressure fed is probably even worse.

You need a better [solid] fuel.  Even assuming you can make better "motors" than https://what-if.xkcd.com/24/ you still have the "build the great pyramid in less than 50 years" problem.  One huge "cheat" you can do is use old records to find exactly what minerals you need (from mining records) that are extremely close to ground level and send legionares to go scoop it up (works for any sufficiently large empire).  Note that Randal Monroe's calculation had an Isp ~90.  I'm guessing that if you can't get an Isp over 200 using stuff Romans can find on the ground (and brew in low-pressure vats), you are stuck waiting for the German chemical engineers of the late nineteenth century.

The rest of the basics are still hard.  I'm guessing you can get enough stabilization with fins through the atmosphere and spin stabilization otherwise (some gyroscopic adjustment is conceivable, but I'd hate to have to go there.  "Clockwork" won't, normal solids have nasty vibrations and this stuff will only get worse: no chance for roman-constructed clockwork.  Fuses will probably be used for all time and similar controls, with little room for anything else.

As far as the shear number of attempts and failures, try to do most of them in the 21st century (when you can do a lot of cheating).  By the time you jump to Roman (or Germanic, if you need real chemists) Empire times you should at least a proven design using period materials.  Even then you need *lots* of contingency planning, and how to work the design under *any* condition.

Finally, expect the little things to bog you down.  You need hundreds of engineers and thousands of slaves?  Easy.  Hundreds of drawings for those engineers?  Better build a printing press.  Hint: printing presses pretty much require paper and don't work with roman writing materials...  Best guess is to spend a couple decades proving the idea in the 21st century, a decade or so building the tools, another decade or so building your supply line, and finally a decade of launching test after test into space to get one to work.

[sevenperforce]

43 minutes ago, wumpus said:

You need a better [solid] fuel.  Even assuming you can make better "motors" than https://what-if.xkcd.com/24/ you still have the "build the great pyramid in less than 50 years" problem.  One huge "cheat" you can do is use old records to find exactly what minerals you need (from mining records) that are extremely close to ground level and send legionares to go scoop it up (works for any sufficiently large empire).  Note that Randal Monroe's calculation had an Isp ~90.  I'm guessing that if you can't get an Isp over 200 using stuff Romans can find on the ground (and brew in low-pressure vats), you are stuck waiting for the German chemical engineers of the late nineteenth century.

The rest of the basics are still hard.  I'm guessing you can get enough stabilization with fins through the atmosphere and spin stabilization otherwise (some gyroscopic adjustment is conceivable, but I'd hate to have to go there.  "Clockwork" won't, normal solids have nasty vibrations and this stuff will only get worse: no chance for roman-constructed clockwork.  Fuses will probably be used for all time and similar controls, with little room for anything else.

As far as the shear number of attempts and failures, try to do most of them in the 21st century (when you can do a lot of cheating).  By the time you jump to Roman (or Germanic, if you need real chemists) Empire times you should at least a proven design using period materials.  Even then you need *lots* of contingency planning, and how to work the design under *any* condition.

What's the best solid or hybrid fuel which could reasonably have been brewed by the Romans? Or, going further back, the Egyptians?

Spin stabilization is a no-no, I think; it will be hard enough to handle axial stress without introducing radial stresses. Getting it into a gravity turn is going to be tough but I'm sure we can come up with some way.

Having determined all this, then...

...I now propose the ultimate Geek Project. Get a bunch of Renfaire nerds and a bunch of KSP nerds together and have them build a period-viable orbital-class rocket.

[Stargate525]

6 hours ago, peadar1987 said:

Let's face it, you're not going to build a liquid fuelled rocket in Roman times. You just aren't. It would take tens of thousands of trained people. Industries that wouldn't yet exist. Probably centuries of development.

Which would still have your first launch in the early 1000s.

You guys are missing the big lack of limit here. Nowhere in the challenge does it state that YOU have to launch the rocket. Going back to 2000BC, even if the rocket takes a thousand years to build after all the bootstrapping, is still better than going to 500ad and doing it in ten.

[K^2]

6 hours ago, Bill Phil said:

Most of that is due to inefficiencies in the engineering process. Usually due to beauracracy. It makes things take forever.

But the Romans already had a society that had large outputs. Go to a guild and teach them about making steel. Or you could just build a factory.

Most of the required tech already existed. It just took time to put it all together. Knowledge of chemical processes was limited, but we ca easily bring it to them. I think that no other civ other than the Romans, at the height of their power, could've accomplished it. It wouldn't be easy, no. But it could be done. It might take a lifetime, but who cares? You've advanced civilization by 2000 years!

A steel mill requires tons, literal tons, of machinery constructed from steel and other tough alloys. You aren't going to have any success at dropping in on a bunch of blacksmiths and telling them, "Here is how you make industrial grade steel." At best, they'll look at it and ask you, "Alright, where do we get all this machinery." More plausibly, they won't even know what you're trying to explain to them, because they don't even have concepts of alloys other than "forged and folded iron is stronger than iron ingots." And all of this with a fiat that for some reason, they are actually listening to you, and trying to do what you tell them.

If you spend a lot of time studying modern metallurgy and its history, you can explain to these people how to build stronger materials, which can be used to build primitive machinery, which can be used to make materials of early industrial quality, which can then be used to create machines resembling modern machinery, which you can use to create materials of quality you actually need to build something interesting. The problem is that they have to start building up to that initial stage with no way to build so much as a steam engine, because brass doesn't make for a particularly great construction material beyond making low-stress tools like the Antikythera Mechanism. That means it will take literal generations of work before there is enough machinery to get you up to that early industrial stepping stool that you need to produce the actual machinery you need to make the materials you need. Just getting to that twice-removed stage is beyond the scope of what you'll likely have time to accomplish. And that's just to get yourself to the position you'd be in if you started with late 18th century tech.

[DerekL1963]

1 hour ago, K^2 said:

That means it will take literal generations of work before there is enough machinery to get you up to that early industrial stepping stool that you need to produce the actual machinery you need to make the materials you need.

And it's more than the stuff on the factory floor...  The goal is to make industrial quantities of steel with predictable qualities.  Which means you need lab equipment too, and all the industries needed to produce it.

Ultimately, that's the thing that most people miss in these alt-history scenarios, most any technology (and especially anything resembling modern technology) is a spiderweb of interdependencies.  Most of them invisible to the casual observer.

[Stargate525]

3 hours ago, DerekL1963 said:

Ultimately, that's the thing that most people miss in these alt-history scenarios, most any technology (and especially anything resembling modern technology) is a spiderweb of interdependencies.  Most of them invisible to the casual observer.

The trick, like I said, isn't to try to force the industrialization. It's to find the one spot in history where a massive dump of knowledge will cut out experimentation and do the most immediate good, and then you let the civilization develop itself. Sputnik will come, not because you're pushing society to do it for some religious ceremonial reason, but because someone will want to or need to do it with the technology they've built up on their own to get all the other luxuries that come with that spiderweb (like running water, sanitation, easy communication with cousin Telemachus in Syria, and the smoothest damn sheets you've ever slept on).

You don't need to give the Roman blacksmiths the blueprints for a foundry (though that might help their grandkids out a lot). You need to explain to them that there's a way to mix coal and iron in such a way as to produce a much, much stronger metal, and this is the basic formula. They'll find uses for it on their own. And when their great-grandkids pour over the library of the man from the future, they'll come across a blueprint for a metal tower that can ride an explosion to the stars...

4 hours ago, K^2 said:

More plausibly, they won't even know what you're trying to explain to them, because they don't even have concepts of alloys other than "forged and folded iron is stronger than iron ingots."

That's blatantly untrue. Your average Roman forgemaster would know about brass, bronze, electrum, meteoric iron (though might not group it as such), pewter, sterling silver, wrought iron, pig iron, and steel (though the concept of making structural materials out of the metal of swords and blades might take explaining). The only thing you've got to teach them is that extreme heat or things other than metals can be used to make these kinds of metals.

 

Edited February 23, 2016 by Stargate525

[razark]

Easy.

Just pop back 2000 years, tell the Romans there's a handful of Celtic tribes on the moon talking smack about them, and hand them the blueprints for everything.

 

Instant lunar program.

[DerekL1963]

1 hour ago, Stargate525 said:

6 hours ago, K^2 said:

More plausibly, they won't even know what you're trying to explain to them, because they don't even have concepts of alloys other than "forged and folded iron is stronger than iron ingots."

That's blatantly untrue. Your average Roman forgemaster would know about brass, bronze, electrum, meteoric iron (though might not group it as such), pewter, sterling silver, wrought iron, pig iron, and steel (though the concept of making structural materials out of the metal of swords and blades might take explaining).

Knowing the existence of the material isn't even remotely the same thing as understanding the concept behind the material.

[Creature]

21 hours ago, K^2 said:

1940, National-Socialist^* Germany. Expecting it to be feasible any earlier is a fantasy. You'd need a lifetime just to build up an infrastructure to produce the necessary materials, and that's presuming you have an established industrial society. Go even further back and it's completely hopeless.

^* The word Nazi should not be censored.

 

I see right through your evil master plan!

 

 

As for the topic itself, if we assume only one trip and let's say the time traveler is 30 years old, lives to 75 via sheer luck (all of you going to B.C times, have fun with the doctors back then) and has to live to see the rocket launch. 1912 Russia would work for sure.

The main issue is that there's just not enough time to develop the necessary infrastructure if you go too far back. Something like 1850 could work in a very optimistic scenario but it's hard to do stuff like this in 45 years. Even skipping all unnecessary studies and super-optimising the education process, it would still take 10-15 years of studying to aquire the required skills to even start building the infrastructure, 10-15 years to build that before the developement of the rocket could even start.

So yeah, I'd say in extremely optimistic scenario, 1850 and one of the european superpowers (also because they can ask help from other superpowers easily) or Russia or possibly China (not familiar enough with chinese history). But in any case I don't think anything before the industrial revolution would work.

[wumpus]

19 hours ago, sevenperforce said:

What's the best solid or hybrid fuel which could reasonably have been brewed by the Romans? Or, going further back, the Egyptians?

Spin stabilization is a no-no, I think; it will be hard enough to handle axial stress without introducing radial stresses. Getting it into a gravity turn is going to be tough but I'm sure we can come up with some way.

Having determined all this, then...

...I now propose the ultimate Geek Project. Get a bunch of Renfaire nerds and a bunch of KSP nerds together and have them build a period-viable orbital-class rocket.

The Egyptians have a single geological area (Nile river valley) [actually, didn't they do some amazing seafaring?  Give them some navigation skills (and things like rudders and jibs) and they might have a better chance of finding things near the coast than anybody].  If you can't find your materials there, you are stuck.  Roman, Chinese, and Assyrian would all have many more choices, and the Chinese and Roman areas would likely have records showing what was mined where.  You really don't want to be forced to make any more precursors than you have to.

 

Is there a chemist or chemical engineer on the board?  When is the earliest you can make aluminum percholarate?  Do we need electricity?  Access to Iceland (where the mineral needed to smelt Al is)?  A quick look at the wiki suggests a solid fuel made from nitroglycerin and nitrocellulose (pick an empire completely indifferent to repeatedly blowing up huge numbers of people), I'm guessing that such a substance could be possible before the 1840s given sufficient precursors and a beeline blueprint to the materials need.

 

Nothing wrong with spin stabilization: vanguard used something like 50rpm.  Using wildly more (several Hz) would hardly put pressure on the rocket.  Consider that the other possibilities include gimbaling the nozzle or putting fins in the exhaust, it is pretty much a given tech for anything we are considering.

 

Metallurgy seems to be a false lead.   For simple steel sheets you can convince Egyptian or later blacksmiths to use the original steel recipe (thin layers of iron mixed with charcoal) and bang them into a single sheet of steel.  Assuming you get your chemical engineering working better, you might get oxygen and a bessemer process: hopefully you can build such a thing out of brick (didn't Bessemer himself?) and get at least some steel to work with (expect a decade of tool building before your blacksmiths can work with the steel you get...).  If you are trying to build up from nothing to turbopumps, you might want to take a long hard look at the industrial revolution: it would be hard to argue that they weren't already doing it as fast as they could (and going from simple steel to machine tools capable of building turbopumps in about 3 centuries).  You best bet is to find a solid fuel that won't melt your simple (layered) steel exhaust bell.

[sevenperforce]

17 minutes ago, wumpus said:

 Roman, Chinese, and Assyrian would all have many more choices, and the Chinese and Roman areas would likely have records showing what was mined where.  You really don't want to be forced to make any more precursors than you have to.

A very good point.

19 minutes ago, wumpus said:

Is there a chemist or chemical engineer on the board?  When is the earliest you can make aluminum percholarate?  Do we need electricity?  Access to Iceland (where the mineral needed to smelt Al is)?  A quick look at the wiki suggests a solid fuel made from nitroglycerin and nitrocellulose (pick an empire completely indifferent to repeatedly blowing up huge numbers of people), I'm guessing that such a substance could be possible before the 1840s given sufficient precursors and a beeline blueprint to the materials need.ell.

Well, yes, you can take back a chemist/chemical engineer in the form of an iPad and a solar-powered charger, with all the chemical engineering information you could ever want.

I hadn't considered Nordic countries...did they have enough manpower?

20 minutes ago, wumpus said:

Nothing wrong with spin stabilization: vanguard used something like 50rpm.  Using wildly more (several Hz) would hardly put pressure on the rocket.  Consider that the other possibilities include gimbaling the nozzle or putting fins in the exhaust, it is pretty much a given tech for anything we are considering.

The thing that worries me about spin stabilization is the issue of tolerances. If you're going to spin-stabilize, you need near-perfect radial axisymmetry. That was easy with Vanguard, but since we're going to be nailing together potentially-uneven sheets of primitive steel, spin stabilization could cause it to rip itself apart pretty quickly.

Compressed-air nose thrusters coupled to a gyroscope using permanent-magnetic couplings could probably do the trick.

30 minutes ago, wumpus said:

Metallurgy seems to be a false lead.   For simple steel sheets you can convince Egyptian or later blacksmiths to use the original steel recipe (thin layers of iron mixed with charcoal) and bang them into a single sheet of steel.  Assuming you get your chemical engineering working better, you might get oxygen and a bessemer process: hopefully you can build such a thing out of brick (didn't Bessemer himself?) and get at least some steel to work with (expect a decade of tool building before your blacksmiths can work with the steel you get...).  If you are trying to build up from nothing to turbopumps, you might want to take a long hard look at the industrial revolution: it would be hard to argue that they weren't already doing it as fast as they could (and going from simple steel to machine tools capable of building turbopumps in about 3 centuries).  You best bet is to find a solid fuel that won't melt your simple (layered) steel exhaust bell.

Yeah, turbopumps are going to be a non-starter at pretty much any point in antiquity.

I wonder if a ceramic exhaust bell might work...or perhaps a steel exhaust bell with an inner ceramic coating/plate.

[Stargate525]

12 hours ago, DerekL1963 said:

Knowing the existence of the material isn't even remotely the same thing as understanding the concept behind the material.

Define 'concept behind the material.' You don't need a degree in metallurgy or physics to understand 'blend metals, get qualities from each.' They've done it, they've MADE those materials.

[DerekL1963]

14 minutes ago, Stargate525 said:

12 hours ago, DerekL1963 said:

Knowing the existence of the material isn't even remotely the same thing as understanding the concept behind the material.

Define 'concept behind the material.' You don't need a degree in metallurgy or physics to understand 'blend metals, get qualities from each.' They've done it, they've MADE those materials.

It means they know the recipes - not the reason why the recipes work, or why they sometimes don't work.   They don't know that adding carbon makes steel, they know "heating in charcoal makes this particular metal harder".   The don't know adding [whatever] makes the material more corrosion resistant, they know "adding a capful of sand collected from the beach of La Mad at high tide will reduce rust".

Knowing how to make something like steel isn't the same as knowing why what you do causes the changes in the materials properties.  The latter is a huge (and largely unrecognized) part of the Industrial Revolution and the modern world - once you know why, you have the ability not only to make material in industrial quantities, but make materials of predictable qualities in industrial quantities.

[sevenperforce]

3 minutes ago, DerekL1963 said:

It means they know the recipes - not the reason why the recipes work, or why they sometimes don't work.   They don't know that adding carbon makes steel, they know "heating in charcoal makes this particular metal harder".   The don't know adding [whatever] makes the material more corrosion resistant, they know "adding a capful of sand collected from the beach of La Mad at high tide will reduce rust".

Knowing how to make something like steel isn't the same as knowing why what you do causes the changes in the materials properties.  The latter is a huge (and largely unrecognized) part of the Industrial Revolution and the modern world - once you know why, you have the ability not only to make material in industrial quantities, but make materials of predictable qualities in industrial quantities.

Indeed, but I'm not sure how one couldn't compensate for this by going back in time with an iPad full of everything we know about practical metallurgy.

[peadar1987]

13 minutes ago, sevenperforce said:

Indeed, but I'm not sure how one couldn't compensate for this by going back in time with an iPad full of everything we know about practical metallurgy.

The problem is more like this (as an example):

-We need to make better steel

-We need Molybdenum to do that

-We need aluminium to use in the Aluminothermic reaction to separate it from its ore

-We need electricity to produce appreciable quantities of aluminium

-We need high-tolerance steam turbines to produce large amounts of electricity

-We need a whole host of advanced metallurgical techniques to produce turbine blades of sufficient quality

-We need to train engineers and operators for our aluminium production and our power plant.

And so on...

It's all interconnected and it's very difficult to raise one area up without having to drag everything else up as well.

[sevenperforce]

1 minute ago, peadar1987 said:

The problem is more like this (as an example):

-We need to make better steel

-We need Molybdenum to do that

-We need aluminium to use in the Aluminothermic reaction to separate it from its ore

-We need electricity to produce appreciable quantities of aluminium

-We need high-tolerance steam turbines to produce large amounts of electricity

-We need a whole host of advanced metallurgical techniques to produce turbine blades of sufficient quality

-We need to train engineers and operators for our aluminium production and our power plant.

And so on...

It's all interconnected and it's very difficult to raise one area up without having to drag everything else up as well.

I'm not saying it wouldn't be a large undertaking, only that the necessary information would all be provided at the outset.

[DerekL1963]

1 hour ago, sevenperforce said:

Indeed, but I'm not sure how one couldn't compensate for this by going back in time with an iPad full of everything we know about practical metallurgy.

Nobody said you couldn't - only that the task is much larger than simply providing information.    You need the tools to make the tools - and this case, that includes considerable chemistry (and the relevant analytical equipment).  Why?  Because you need to know the properties of your inputs in order to predict the qualities of your outputs, that's the basic foundation of modern practical metallurgy.

The modern blacksmith doesn't have the chemistry, but he doesn't need it because he either orders materials with known qualities from a catalog, or selects materials 'in the wild' (such as leaf springs) already known to have certain qualities.  Someone else has already taken care of that end of the process for him.   You'll need the chemistry (and the related equipment) in Ancient Rome because you have neither a catalog nor materials of known quality available - you have to build the whole infrastructure up from scratch.

[sevenperforce]

16 minutes ago, DerekL1963 said:

Nobody said you couldn't - only that the task is much larger than simply providing information.    You need the tools to make the tools - and this case, that includes considerable chemistry (and the relevant analytical equipment).  Why?  Because you need to know the properties of your inputs in order to predict the qualities of your outputs, that's the basic foundation of modern practical metallurgy.

The modern blacksmith doesn't have the chemistry, but he doesn't need it because he either orders materials with known qualities from a catalog, or selects materials 'in the wild' (such as leaf springs) already known to have certain qualities.  Someone else has already taken care of that end of the process for him.   You'll need the chemistry (and the related equipment) in Ancient Rome because you have neither a catalog nor materials of known quality available - you have to build the whole infrastructure up from scratch.

How do we not have materials of known quality available? We know where stuff was mined.

[micr0wave]

A lot of things were forgotten and had to be invented a second time.

When you think about metallurgy for example, copper, bronze, iron were in use for thousands of years, glass also thousands of years in use, gunpowder (ancient china for fireworks and such) or japanese steel for the katanas.

With some copper, iron, wood and a nearby river you'd have electricity pretty quickly. Electrolytic reactions to get some pure chemicals. So the starting tools shouldn't be impossible to get , to magnify that to some small scale industrial complex capable of launching a rocket to orbit will take some serious effort though.

Best approach might be having some educational thing going. Thousands of brains thinking about problems will solve things faster than just one.

Edited February 23, 2016 by micr0wave
typo

[fredinno]

On February 21, 2016 at 8:53 PM, Findthepin1 said:

I vote BCE. Billions BCE. Before Earth had any atmosphere or substantial mass. When it was the size of Deimos. I'd pick up a rock and throw it into orbit.

Well, we probably could get an orbit by jumping, THEN throwing a rock.

[Laie]

On 2/22/2016 at 5:35 PM, sevenperforce said:

This challenge is informed by a more specific question, to wit: what are the poorest, highest-tolerance material properties with which the components of an orbital-class rocket can be achieved?

Coming at it from that angle, I'd say that bronze might have sufficed. Looking at bronze-age arts and crafts, I guess they could have made clockwork and whatnot. Hammering out a rocket 500BC might be possible. Though I'd expect that your (many) artisans will take a while to pick up all the knowledge. Talk about having your mind blown.

 

1 hour ago, sevenperforce said:

How do we not have materials of known quality available? We know where stuff was mined.

I take that as "you can't just walk down to the chemist and order a barrel of UDMH", or gasoline for that matter. You need to make the stuff. Not only the basic chemistry of making, but also to pretty strict standards of purity.
I guess the chemistry might be more of a limiting factor than building a rocket motor, tanks, valves, and even controls.

 

[sevenperforce]

59 minutes ago, Laie said:

Coming at it from that angle, I'd say that bronze might have sufficed. Looking at bronze-age arts and crafts, I guess they could have made clockwork and whatnot. Hammering out a rocket 500BC might be possible. Though I'd expect that your (many) artisans will take a while to pick up all the knowledge. Talk about having your mind blown.

 

I take that as "you can't just walk down to the chemist and order a barrel of UDMH", or gasoline for that matter. You need to make the stuff. Not only the basic chemistry of making, but also to pretty strict standards of purity.
I guess the chemistry might be more of a limiting factor than building a rocket motor, tanks, valves, and even controls.

 

Yeah, the chemistry is very much going to be a case of going a long way from really basic raw materials.

[DerekL1963]

2 hours ago, sevenperforce said:

How do we not have materials of known quality available? We know where stuff was mined.

In some cases, not many, we know the exact location of the mine.   In others, only the broad general area at best.  And it's a dead certainty that there are yet others we have no idea about even the existence of in modern times.   When you study history in detail, it's very frustrating how much we *don't* know and have no way of knowing.

 

1 hour ago, Laie said:

I take that as "you can't just walk down to the chemist and order a barrel of UDMH", or gasoline for that matter. You need to make the stuff. Not only the basic chemistry of making, but also to pretty strict standards of purity.
I guess the chemistry might be more of a limiting factor than building a rocket motor, tanks, valves, and even controls.

That too.   Refining iron requires more than ore of a known composition, it requires various chemicals and additives to strip out what we don't want and to add what we do want.