Science/history challenge: Beat Sputnick

[Mad Rocket Scientist]

17 hours ago, sevenperforce said:

A fascinating possibility. What kind of ISP could that develop, and how would you stage/contain it?

ISP doesn't matter, since you can just add more rocket.  Staging could be as simple as in model rockets, with staging charges at the top of the motor.  Containment and control would be the trickiest bit.  For containment, possible some kind of metal, or maybe even using rope of some sort for a composite shell.  Control: this would be tricky.  Maybe a gyroscope set up to fire small motors arranged radially around the top of the rocket?  So if it tipped to far in one direction, this would fire a rocket in the other direction.  Thrust vanes are another possibility.

[sevenperforce]

17 minutes ago, Mad Rocket Scientist said:

ISP doesn't matter, since you can just add more rocket.  Staging could be as simple as in model rockets, with staging charges at the top of the motor.  Containment and control would be the trickiest bit.  For containment, possible some kind of metal, or maybe even using rope of some sort for a composite shell.  Control: this would be tricky.  Maybe a gyroscope set up to fire small motors arranged radially around the top of the rocket?  So if it tipped to far in one direction, this would fire a rocket in the other direction.  Thrust vanes are another possibility.

If ISP is too low, not even staging can save you. See what-if #24.

[Mad Rocket Scientist]

20 minutes ago, sevenperforce said:

If ISP is too low, not even staging can save you. See what-if #24.

True, but model rocket engines have a low mass fraction just due to their size. 

Here's my thoughts: earth escape velocity ASL is 11.2 km/s.  It takes 10 km/s to reach a 7.8 km/s orbit, so drag, steering, and gravity losses are about 2.2 km/s, call it for 2.5 km/s because of higher drag for our rocket.  That's 13.7 km/s to escape velocity. 

Let's say that the ISP of a early black powder rocket is ~80.  Reversing the rocket equation gives us:
e^[13.7/(9.81*80)] = 1.01760993514
We round that to 1.02.  If I did my math right, that's pretty good.  It does need multiple stages, but that's not a problem. 

Please tell me what mistakes you find in this, when I get it right, I'll continue with a more detailed assessment.

ETA: Wikipedia has a different mass ration equation:

Which gives 11136.4, but now I'm all confused.

Edited February 26, 2016 by Mad Rocket Scientist

[sevenperforce]

I can solve the rocket equation myself, but it's typically easier to just plug the values into something like this calculator (thus avoiding the potential for math errors).

I'm not quite sure why you'd want to use escape velocity; the goal is merely to get to orbit. We can say 10.5 km/s to give ourselves a margin. Unfortunately, using the above calculator shows that with an ISP of 80, you would need over 655 tonnes of fuel for every kilogram of dry mass to get that kind of delta v. That's a mass ratio of 655000:1.

[Mad Rocket Scientist]

24 minutes ago, sevenperforce said:

I can solve the rocket equation myself, but it's typically easier to just plug the values into something like this calculator (thus avoiding the potential for math errors).

I'm not quite sure why you'd want to use escape velocity; the goal is merely to get to orbit. We can say 10.5 km/s to give ourselves a margin. Unfortunately, using the above calculator shows that with an ISP of 80, you would need over 655 tonnes of fuel for every kilogram of dry mass to get that kind of delta v. That's a mass ratio of 655000:1.

That calculator is great!  Thanks.

Escape velocity make a much simpler control system compared to LEO.  However, looking at that, probably the trickier control system is better.

[DerekL1963]

On 2/24/2016 at 1:51 PM, sevenperforce said:

You can equip the ancient civilization with whatever industries are necessary in order to build the rocket, but you only have your own lifetime to do it in. Which means you'll need to limit yourself to stuff which can be done rapidly, without a lot of precursors and development and construction time. Basically stuff where manpower is your limiting variable...because that's where ancient civilizations have the edge.

Then frankly "you are not going to space today", not in anything that can actually lift off and has a better than .01% chance to not blow up before it gets to orbit.   Basically you need high quality steel for the case and nozzle (or tankage and engines) and at least 1930's tech in a wide variety of areas (though especially in gyro's and hydraulics/pneumatics), and all of those require considerable precursors.

Not that ancient civilizations had much in the way of excess manpower, between armies and farmers they were actually usually lacking in those departments.

[sevenperforce]

51 minutes ago, DerekL1963 said:

Then frankly "you are not going to space today", not in anything that can actually lift off and has a better than .01% chance to not blow up before it gets to orbit.   Basically you need high quality steel for the case and nozzle (or tankage and engines) and at least 1930's tech in a wide variety of areas (though especially in gyro's and hydraulics/pneumatics), and all of those require considerable precursors.

Not that ancient civilizations had much in the way of excess manpower, between armies and farmers they were actually usually lacking in those departments.

Ceramic nozzle; banded metal for the body. Guidance is tricky, sure, but we could come up with something. Fuel chemistry is the main challenge. 

[DerekL1963]

1 hour ago, sevenperforce said:

Ceramic nozzle; banded metal for the body. Guidance is tricky, sure, but we could come up with something. Fuel chemistry is the main challenge. 

You can't make the kind of ceramics that will withstand rocket exhaust with ancient world technology - the kilns used aren't predictable enough, don't burn hot enough anyhow (they're wood and charcoal fired), and the ancients didn't use the input materials needed (let alone have any method of purifying them).

Banded metal could mean anything, so you're just handwaving.  If you're riveting, your tank is far too heavy anyhow (and probably won't hold together if you put cryogenics in it).  It probably won't withstand the pressure either...  not without highly trained and experienced riveters.   Either way, welding or riveting, there's a lot of skills and precursors you'll have to bootstrap.  And without relatively modern steels or preferably aluminum, it'll be too heavy because it'll be too thick, welded or riveted.  

Guidance won't be 'tricky' - it will be impossible without at least gyros for reference.

Fuel chemistry is far, very far, from being the main challenge.

[maculator]

I think 1940. I't doesnt help, that you know what to do, you also need the materials and infrastructure.

So I guess late 30's/early 40's would be a good time. Just tell hitler to shut up for a moment and lend you wherner.

He got the financialpower and the guys to do it.

Trying it in the 19th century or earlier would be pretty hard since the materials and technics for rockets arent developped.

WW2 is perfect for this purpose since it boosted the technic and if you show up with a idea like orbiting a superweapon and you already got some blueprints Im sure it can be done in no time.

 

[fredinno]

On 2/24/2016 at 1:51 PM, sevenperforce said:

You can equip the ancient civilization with whatever industries are necessary in order to build the rocket, but you only have your own lifetime to do it in. Which means you'll need to limit yourself to stuff which can be done rapidly, without a lot of precursors and development and construction time. Basically stuff where manpower is your limiting variable...because that's where ancient civilizations have the edge.

Yeah, but ancient civilisations also don't have machinery to make the process go faster.

[sevenperforce]

15 hours ago, DerekL1963 said:

You can't make the kind of ceramics that will withstand rocket exhaust with ancient world technology - the kilns used aren't predictable enough, don't burn hot enough anyhow (they're wood and charcoal fired), and the ancients didn't use the input materials needed (let alone have any method of purifying them).

Banded metal could mean anything, so you're just handwaving.  If you're riveting, your tank is far too heavy anyhow (and probably won't hold together if you put cryogenics in it).  It probably won't withstand the pressure either...  not without highly trained and experienced riveters.   Either way, welding or riveting, there's a lot of skills and precursors you'll have to bootstrap.  And without relatively modern steels or preferably aluminum, it'll be too heavy because it'll be too thick, welded or riveted.  

Guidance won't be 'tricky' - it will be impossible without at least gyros for reference.

Fuel chemistry is far, very far, from being the main challenge.

Upgrading kiln tech to enable better ceramics will almost certainly be simpler than trying to upgrade metallurgy to a comparable level. Plus, you can mix and match properties; you can use a ceramic inner layer for thermal properties with a steel outer layer for mechanical properties. A kludge, perhaps, but a workable one.

We certainly wouldn't be using cryogens, so the goal is to build the SRB body with enough axial compressive strength to support the rocket in flight and enough skin tensile strength to contain the solid fuel combustion gases. The latter isn't as challenging as it seems, because the solid fuel itself will act as a heat sink and load distributor for the majority of the burn period. In fact, stage separation could be accomplished by merely making the upper portion of the booster body too weak to contain the combustion gases at the end of the burn. I'm thinking an internal wooden frame (wood is a good enough insulator to remain strong during the relatively brief burn, and its tensile, compressive, and torsion strengths will be better than metal for weight cost at this era), wrapped in thin beaten metal, with a few thicker metal bands wrapped around the outside. 

Getting gyros to work is hard, I agree. 

[micr0wave]

Some things look harder than they are, we have a huge, and i mean really huge, workforce, we aren't limited by any financial issues.

It's not that we have to sit there 400 years until someone has the idea of putting some more chrome into the steel to make it better, it's all in the iPad (which i suggest to have it copyrighted as first task when arriving in the past ).

We know how to make good materials, we have the blueprints for the production, we know what to do and why, what not. No need for any R&D in a large scale.

Some people have built CPUs in minecraft, i'm pretty sure that there's something even better than redstone mentioned in the iPads library.

Oh, and we want just one rocket, not a whole fleet-

Edited February 27, 2016 by micr0wave

[Stargate525]

11 minutes ago, micr0wave said:

Some things look harder than they are, we have a huge, and i mean really huge, workforce, we aren't limited by any financial issues.

It's not that we have to sit there 400 years until someone has the idea of putting some more chrome into the steel to make it better, it's all in the iPad (which i suggest to have it copyrighted as first task when arriving in the past ).

We know how to make good materials, we have the blueprints for the production, we know what to do and why, what not. No need for any R&D in a large scale.

Some people have built CPUs in minecraft, i'm pretty sure that there's something even better than redstone mentioned in the iPads library.

Oh, and we want just one rocket, not a whole fleet-

No, we're limited by logistical and mechanical ones.

The first copyright was issued in 1662. Before about 1600 no one would have any concept of what you're talking about. And really, you're talking more trademark. Which is still silly, since you won't be able to breach it for hundreds of years.

Yes, but we need to first make the things we need for the production. It's not hard to make a cake 'from scratch.' Unless you need to grow the wheat, tame the chickens, birth the cow, refine the sugarcane, distill the vanilla, and make the bowl, whisk, pan, oven, and grindstone.

I'm pretty damned sure there is no real-world analog to a material that can be mined out with a bog-standard pickaxe, laid down in a powder, and can transmit signal without any mechanical or electrical input over distances of meters.

 

[micr0wave]

That copyright part wasn't meant serious in case it wasn't obvious enough. Redstone acts in that example as transistor mostly which can be made after some time. The rocket hasn't to be built in a week, of course it will take some time to build the tools and gather the materials in a sufficient quality, but a lot of the things are already available.

We know all the discoveries that had to be done to build high quality materials.

It's a bit like a puzzle where all the pieces are scattered around the globe where every person that has one piece has a totally different vision of what the final picture will look like, but you know how it will look, and you know which piece to put where.

A lot of giant leaps in technology are really 'simple', for example rubber, a bit dropped on a hot kitchen stove and bingo. Don't get fooled by current industrial production of things, pretty much all of them are shaped by financial means. Efficiency in making all needed things is no issue at all, we have a whole empire, a worforce magnitudes bigger than NASA ever could dream of.

Edited February 27, 2016 by micr0wave

[Stargate525]

9 minutes ago, micr0wave said:

Don't get fooled by current industrial production of things, pretty much all of them are shaped by financial means. Efficiency in making all needed things is no issue at all, we have a whole empire, a worforce magnitudes bigger than NASA ever could dream of.

I'm not fooled. The problem you're overlooking is that whether we have ten people or ten thousand is irrelevant when we need very precise, uniform objects. Industry can make a lot of an object, but they are also CONSISTENT. Look up the french Chauchat for examples of what happens when mechanical objects aren't built within good enough tolerances.

[micr0wave]

But we know how to QA all the things.

With the magic iPad the poor guys wouldn't have to deal with those bad rifles, they'd run around with AK-47s

You can, in your kitchen, adjust bases, acids on a pretty precise pH just using some natural indicators for example, don't get me wrong, it will be an enormous task, but i wouldn't right out say it's impossible with all the current knowledge.

They will most likely not take measurements with a rope that has a couple knots for scaling, we know better these days.

[Andem]

Quick question, why is everyone assuming that north Africa and Europe would ne the best spot... Wouldn't China be a better location? They already had crude flyers, is it that much of a stretch to assume they would be a better place to start an ancient space program?

Edited February 28, 2016 by Andem
Stupid Autocorrect...

[StrandedonEarth]

China has been mentioned in this thread a few times. They certainly had the manpower and the tech to give it a shot, more so than the Egyptians and at least equal to the Romans. I went with Egypt partly because they *may* have been able to do it earlier, but mostly because I've read Wilbur Smith's Egyptian books. Plant the space bug in Taita's ear and watch out....

[fredinno]

On February 27, 2016 at 8:39 AM, sevenperforce said:

Upgrading kiln tech to enable better ceramics will almost certainly be simpler than trying to upgrade metallurgy to a comparable level. Plus, you can mix and match properties; you can use a ceramic inner layer for thermal properties with a steel outer layer for mechanical properties. A kludge, perhaps, but a workable one.

We certainly wouldn't be using cryogens, so the goal is to build the SRB body with enough axial compressive strength to support the rocket in flight and enough skin tensile strength to contain the solid fuel combustion gases. The latter isn't as challenging as it seems, because the solid fuel itself will act as a heat sink and load distributor for the majority of the burn period. In fact, stage separation could be accomplished by merely making the upper portion of the booster body too weak to contain the combustion gases at the end of the burn. I'm thinking an internal wooden frame (wood is a good enough insulator to remain strong during the relatively brief burn, and its tensile, compressive, and torsion strengths will be better than metal for weight cost at this era), wrapped in thin beaten metal, with a few thicker metal bands wrapped around the outside. 

Getting gyros to work is hard, I agree. 

...but wood burns.

[Bill Phil]

51 minutes ago, fredinno said:

...but wood burns.

And cork's a good heat shield, your point is?

Yeah, wood burns, but technically a bunch of things can. And cars were built with lots of wood, airplanes, military landing craft.

It is 100% correct to say that wood is a very versatile material.

[lobe]

I need help understanding why solid fuel would be a superior choice. From what I have seen looking around aluminum is essential to orbit-capable propellants, and would need a large discovery and electrical industry to get it, as well as complex blends of crude oil derived petroleum products. Liquid fuel, while requiring some special alloys, could have been produced quite early or much more efficiently than any solid fuel. I am talking of course about nitric acid and ethanol/petroleum distillate, though if we hae the infrastructure for nitric acid we might as well make hydrazine too. Quite literally we could pull fuel from the air through the Haber process. Turbopumps wouldn't even be that hard, especially if we go with centrifugal pumps, which might not even need to be designed with special alloys since the turbine might spin under 30,000 rpm.

[sevenperforce]

12 hours ago, fredinno said:

...but wood burns.

Indeed. But it is a good enough insulator that we can construct internal trusses which will remain sturdy even while the surface is on fire. We will know the burn time of each rocket stage, after all. It's going to be a better choice than trying to forge metal with sufficiently heat-resistant properties, because metal is a much better heat conductor.

7 hours ago, lobe said:

I need help understanding why solid fuel would be a superior choice. From what I have seen looking around aluminum is essential to orbit-capable propellants, and would need a large discovery and electrical industry to get it, as well as complex blends of crude oil derived petroleum products. Liquid fuel, while requiring some special alloys, could have been produced quite early or much more efficiently than any solid fuel. I am talking of course about nitric acid and ethanol/petroleum distillate, though if we hae the infrastructure for nitric acid we might as well make hydrazine too. Quite literally we could pull fuel from the air through the Haber process. Turbopumps wouldn't even be that hard, especially if we go with centrifugal pumps, which might not even need to be designed with special alloys since the turbine might spin under 30,000 rpm.

Getting a liquid fuel at high grade might be a little easier than getting solid fuel at high grade. However, storing, pumping, pressurizing, and combusting in a bipropellant liquid-fueled rocket is going to require a set of tolerances far in excess of what we will be able to build without vast, vast industrial capabilities. 

And even if we could build such a rocket within the required tolerances, it would be so much heavier than modern designs that it would be pointless. Solid fuel rockets have excellent thrust to weight ratios, while liquid fuel rockets require extremely precise machining in order to get even decent thrust to weight ratios. I doubt a liquid rocket engine built any time before the 20th century would have sufficient thrust to get off the ground with any meaningful amount of fuel.

[Sanic]

I chose the Renaissance...

 

[lobe]

On 2/29/2016 at 8:47 AM, sevenperforce said:

And even if we could build such a rocket within the required tolerances, it would be so much heavier than modern designs that it would be pointless.

Why would the tolerances matter in terms of weight/mass? I would think that the most negative consequence of a liquid fueled rocket in pre-1700's world would be acid attacks and near sightedness because of the precision. Vernier measuring devices should be ok. 

[Laie]

To summarize, there's several key points:

1. precision parts. Skilled artisans have done miraculous things since 1000BC, but I don't know how many of them you'd have available and they will need time.
2. materials. While making steel is relatively easy, making large things from steel requires a lot of machinery. Hammer & anvil will only take you so far.
3. fuel chemistry. I've yet to see a matching pair of propellants that can be made and stored with pre-1800 tech.
4. sheer scale. Ancient civilizations may have had quite some economy going, but it's nothing compared to us today. I especially don't buy the manpower argument.

As to 1) the A4 rocket motor doesn't look overly complicated but if you have to do every pipe and fitting from scratch, with no better tools than furnace, anvil, and file-to-fit, it represents several man-years of effort. And that's definitely skilled labor, a thousand press-ganged peasants won't do.

As to 4), I've heard somewhere that the human death rate was 93% -- in other words, seven percent of all humans that ever lived are alive today. Never checked, but it rings true. If we were to take the premise and put it on it's head, "could a modern society build pyramids with manual labor" the answer is a resounding yes. The EU currently has what, 500 million people? Of which about one is twenty is unemployed. If you're after a society that could theoretically marshall a lot of manpower on a whim, I wouldn't look in the distant past.