This is very cliched, but I am interested to hear about the possibility of this. I could safely assume it is implausible, based on how long OTL took. However, that does not make this impossible! Thoughts? If your POD that makes this happen is early on in history, than it would need more explanation probably than one in ex. 1887.
AHC: Spacecraft in the 19th Century
- Thread starter Mental_Wizard
- Start date
In a realistic setting, I suppose you could have horizontally pointed space guns for firing smaller projectiles up into orbit (think the Columbiad from Jules Verne's Moon novels), but without more sophisticated technology, there would be no point to such a satellite-launching endeavour. You couldn't communicate with it, remote-control it, send or receive feedback to science instruments, nothing. At most, you could observe the satellite projectile orbiting the Earth.
Speaking of Verne, even that relatively simple space gun would be a chore to design, build and operate. A space gun using "coilgun"-style magnetic acceleration technology is much more doable and reliable, but it can't be built with 19th century tech. Or our present tech, as we still haven't cracked all the engineering challenges the construction of such an enormous device would entail. (Make no mistake, a coilgun launcher cannon would have to be kilometers long.)
In an ASB or otherwise fantastical setting, you could think up various quasi-scientific crutches to make spacecraft work.
Speaking of Verne, even that relatively simple space gun would be a chore to design, build and operate. A space gun using "coilgun"-style magnetic acceleration technology is much more doable and reliable, but it can't be built with 19th century tech. Or our present tech, as we still haven't cracked all the engineering challenges the construction of such an enormous device would entail. (Make no mistake, a coilgun launcher cannon would have to be kilometers long.)
In an ASB or otherwise fantastical setting, you could think up various quasi-scientific crutches to make spacecraft work.
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History Learner
Banned
Well, there was some serious research being done into rockets by some guy (Can't recall his name) in the 1880s. Maybe some earlier developments on that front combined with a Difference/Analytical engine produced, you could possible get some orbital or sub-orbital missions achieved. I sincerely doubt Human exploration of space was possible, however.
I take the challenge to mean, "without tremendous advances so that technology is generally advanced some 60-70 years." I've seen this challenge before, and would suggest that perhaps it might be possible to achieve orbit with a very large, multistage rocket. The engines would be pressure-fed because making a turbo pump to get the job done would be one of the stumbling blocks. My latest hobby-horse is to speculate on the possibilities of using propane as the fuel with hydrogen peroxide as the oxidant. As any backyard barbecue set owner knows, propane can be kept in high pressure vessels in a liquid/gaseous state; as one vents off liquid the gas expands to fill the volume removed, the mix cools, and ambient heat restores the temperature and pressure.
A modern rocket using this principle would aim at simplicity by the fuselage being one uniformly pressurized shell, divided into a relatively small propane compartment and a larger peroxide chamber, the peroxide being kept in a plastic bag and with a gas vent from the top of the propane chamber to the top of the peroxide one. This automatically guarantees identical pressures for both. The engine would simply open valves to spray propane in to contact with a catalyzed hydrogen peroxide flow that would already be quite hot and "ignited;" on mixing the gases would burn--the sprayed liquid propane would of course flash into gas. The hitch, in pre-1900 terms, would be that there were no plastics available to bag the peroxide in; flexible fabrics would tend to react with the peroxide, while letting gaseous propane contact high test hydrogen peroxide directly seems pretty scary! Perhaps a good piston head could do the job well enough, with minor leaks of either reactant to the other side having only minor consequences. Friction of the piston seals would impede pressurization of the peroxide unfortunately; maybe a spring could compensate? Because the rate of propellant flow would be high and the rocket would soon rise out of the dense sea level atmosphere, it would be necessary to arrange for the propane to be heated somewhat by the combustion chamber or nozzle waste heat, and return a flow of hot propane (calibrated) to the propane tank, where it is metered to provide just the heat of vaporization needed to evaporate just the right amount of propane to maintain pressure of both chambers.
In addition to plastic bags and high-tech materials for the engine we could be quite confident could handle the heat, doing it in the 21st century also offers much lighter pressure vessel materials, such as carbon composite.
The velocity any stage can achieve is a function of the total mass before firing, divided by the burnout mass. Taking the logarithm of that times the effective exhaust speed of the nozzle gives us the change in velocity that can be achieved with a given mass of propellant. It is often the case that first stages fall far short of orbital velocity and this is why multiple stages are necessary. The lighter we can make the structure of each stage, the greater velocity it can achieve with a given payload.
The higher the pressure we can maintain, the more efficient the rocket combustion can be. The higher the exhaust velocity, the more velocity we can get out of a given propellant load--but exhaust velocity will correlate to chamber temperature, and I would worry how high a temperature late 19th century materials could take. A metal combustion chamber and nozzle would probably still have to be regeneratively cooled, by flows of propane or perhaps hydrogen peroxide. Alternatively one might take a page from OTRAG and develop ablative chambers and nozzles from blocks of asbestos. This would be heavy and inefficient unfortunately. But one reason I'm looking at hydrogen peroxide as oxidant is that the mix would burn relatively cool. Another is that the mass ratio of fuel to HTHP is very low; most propellent by mass would be the peroxide, essentially the fuel functions as additive to energize it more.
I'm visualizing the stages as ogive pressure shells with a cylinder with a relatively thin wall down the centerline being the peroxide vessel, the propane occupying the volume between that and the outer wall. It might be possible to have gimbaled sets of rocket chamber/nozzle, but the hydraulics/pneumatics to drive their motion might be very problematic to power and control responsively, so I think they'd go for fixed engines surrounding the periphery of the bottom of the stage, and simply vary thrust with pintle valves as on the modern SpaceX Merlin engines or the Apollo LM descent module engine; differential thrust would give pitch control about two axes with three or more engines--I'd intuitively aim for six. There is no roll control about the axis; in low atmospheric ascent fixed fins on the first stage would tend to stabilize and damp out roll, and for higher stages we'd need vernier engines firing at right angles to the rocket axis.
I suspect that to get the stage body light enough we'd have to cheat on the "Tech as OTL before 1900" rule a bit. Could it be possible for 19th century engineering to develop basalt fiber mat composites? This involves extruding melted basaltic rock through fine high temperature dies to produce basalt fibers, then matting them in a melted metal matrix of some kind analogous to fiberglas. I'd think the metal matrix would be some kind of steel. This might yield sheets of material with very high tensile strength, suitable for shaping into gores that could be bolted together on flanges for a high pressure vessel that is not too heavy. A very thin sheet of the stuff could form the central peroxide cylinder.
Alternatively perhaps if we are using peroxide, we can make turbo pumps using the catalyzed peroxide to drive them. The Soviet R-7 rocket that put up Sputnik and Vostok used engines pumped by HTHP after all, a technology developed by Von Braun's people in Germany and used on V-2 rockets and Redstone and I suspect Juno as well. Since peroxide exhaust is much cooler than the sorts of temperatures used in more advanced fuel/oxidant gas generators and even more demanding later staged combustion engines, maybe it can be feasible with somewhat plausible precocious 19th century metallurgy? Since the HTHP is the main oxidant perhaps it would be possible to dump the gas generator exhaust into the main combustion chamber for the released oxygen to help burn the fuel and for the mass to be included in the main exhaust; alternatively, it could simply be dumped overboard as with the gas generator driven F-1 engine-or those Soviet late 1950s engines.
If we can pump the propellants, then they can be stored at more modest pressures, and we are no longer restricted to propane for fuel; it can be any liquid, such as plain kerosene. We'd still need a pressurant to fill the ullage of the HTHP chamber, but perhaps something like liquid nitrogen heated into ambient-temperature gas can do; then we can dispense with the piston since the nitrogen can contact the peroxide directly without risk of a wildcat reaction.
I can't take too much time to investigate all this in detail right now, but I did mean to suggest that perhaps, 19th Century materials, or anyway stuff that could reasonably have been developed in that time frame without revolutionary advances in general tech level, might be able to provide the raw rocket thrust needed to put something massing a few tons into LEO. Then the question of what kind of spacecraft could be useful in orbit comes up, and obviously except for a mere stunt of putting some inert object into orbit to point at, it would have to be manned to accomplish anything. And that implies either crazy kamikaze scientists who know their orbit is a prelude to suicide, or a means of surviving reentry.
Fortunately I do think that a practical reentry capsule does not require any highly advanced materials. In a pinch cork can serve as an ablative heat shield. What is precocious is the realization in advance that only ballistic reentry is feasible, and doing the math to predict how much ablative is needed and exactly what limited range of reentry angles would be survivable. For orbital maneuvering and control, more pressurized HTHP/fuel mix rockets ought to fit the bill.
For the crew to control the rocket on its way up, by the late 19th century I think electric tech is developed enough that some sort of analog voltage based signal wires can command solenoids to control the valves of lower stage rocket engines, and to command blowing off exhausted lower stages and switch over to controlling the next stage up. A pressure meter can signal the tank pressure of a pressure fed stage; when the last of the propane is boiled off, it would be time to ditch it, and once that reserve is gone, the pressure in the combined tanks would start to fall. If pre-calculation is done correctly, this will happen just as the last of the peroxide is blown out of its chamber.
A modern rocket using this principle would aim at simplicity by the fuselage being one uniformly pressurized shell, divided into a relatively small propane compartment and a larger peroxide chamber, the peroxide being kept in a plastic bag and with a gas vent from the top of the propane chamber to the top of the peroxide one. This automatically guarantees identical pressures for both. The engine would simply open valves to spray propane in to contact with a catalyzed hydrogen peroxide flow that would already be quite hot and "ignited;" on mixing the gases would burn--the sprayed liquid propane would of course flash into gas. The hitch, in pre-1900 terms, would be that there were no plastics available to bag the peroxide in; flexible fabrics would tend to react with the peroxide, while letting gaseous propane contact high test hydrogen peroxide directly seems pretty scary! Perhaps a good piston head could do the job well enough, with minor leaks of either reactant to the other side having only minor consequences. Friction of the piston seals would impede pressurization of the peroxide unfortunately; maybe a spring could compensate? Because the rate of propellant flow would be high and the rocket would soon rise out of the dense sea level atmosphere, it would be necessary to arrange for the propane to be heated somewhat by the combustion chamber or nozzle waste heat, and return a flow of hot propane (calibrated) to the propane tank, where it is metered to provide just the heat of vaporization needed to evaporate just the right amount of propane to maintain pressure of both chambers.
In addition to plastic bags and high-tech materials for the engine we could be quite confident could handle the heat, doing it in the 21st century also offers much lighter pressure vessel materials, such as carbon composite.
The velocity any stage can achieve is a function of the total mass before firing, divided by the burnout mass. Taking the logarithm of that times the effective exhaust speed of the nozzle gives us the change in velocity that can be achieved with a given mass of propellant. It is often the case that first stages fall far short of orbital velocity and this is why multiple stages are necessary. The lighter we can make the structure of each stage, the greater velocity it can achieve with a given payload.
The higher the pressure we can maintain, the more efficient the rocket combustion can be. The higher the exhaust velocity, the more velocity we can get out of a given propellant load--but exhaust velocity will correlate to chamber temperature, and I would worry how high a temperature late 19th century materials could take. A metal combustion chamber and nozzle would probably still have to be regeneratively cooled, by flows of propane or perhaps hydrogen peroxide. Alternatively one might take a page from OTRAG and develop ablative chambers and nozzles from blocks of asbestos. This would be heavy and inefficient unfortunately. But one reason I'm looking at hydrogen peroxide as oxidant is that the mix would burn relatively cool. Another is that the mass ratio of fuel to HTHP is very low; most propellent by mass would be the peroxide, essentially the fuel functions as additive to energize it more.
I'm visualizing the stages as ogive pressure shells with a cylinder with a relatively thin wall down the centerline being the peroxide vessel, the propane occupying the volume between that and the outer wall. It might be possible to have gimbaled sets of rocket chamber/nozzle, but the hydraulics/pneumatics to drive their motion might be very problematic to power and control responsively, so I think they'd go for fixed engines surrounding the periphery of the bottom of the stage, and simply vary thrust with pintle valves as on the modern SpaceX Merlin engines or the Apollo LM descent module engine; differential thrust would give pitch control about two axes with three or more engines--I'd intuitively aim for six. There is no roll control about the axis; in low atmospheric ascent fixed fins on the first stage would tend to stabilize and damp out roll, and for higher stages we'd need vernier engines firing at right angles to the rocket axis.
I suspect that to get the stage body light enough we'd have to cheat on the "Tech as OTL before 1900" rule a bit. Could it be possible for 19th century engineering to develop basalt fiber mat composites? This involves extruding melted basaltic rock through fine high temperature dies to produce basalt fibers, then matting them in a melted metal matrix of some kind analogous to fiberglas. I'd think the metal matrix would be some kind of steel. This might yield sheets of material with very high tensile strength, suitable for shaping into gores that could be bolted together on flanges for a high pressure vessel that is not too heavy. A very thin sheet of the stuff could form the central peroxide cylinder.
Alternatively perhaps if we are using peroxide, we can make turbo pumps using the catalyzed peroxide to drive them. The Soviet R-7 rocket that put up Sputnik and Vostok used engines pumped by HTHP after all, a technology developed by Von Braun's people in Germany and used on V-2 rockets and Redstone and I suspect Juno as well. Since peroxide exhaust is much cooler than the sorts of temperatures used in more advanced fuel/oxidant gas generators and even more demanding later staged combustion engines, maybe it can be feasible with somewhat plausible precocious 19th century metallurgy? Since the HTHP is the main oxidant perhaps it would be possible to dump the gas generator exhaust into the main combustion chamber for the released oxygen to help burn the fuel and for the mass to be included in the main exhaust; alternatively, it could simply be dumped overboard as with the gas generator driven F-1 engine-or those Soviet late 1950s engines.
If we can pump the propellants, then they can be stored at more modest pressures, and we are no longer restricted to propane for fuel; it can be any liquid, such as plain kerosene. We'd still need a pressurant to fill the ullage of the HTHP chamber, but perhaps something like liquid nitrogen heated into ambient-temperature gas can do; then we can dispense with the piston since the nitrogen can contact the peroxide directly without risk of a wildcat reaction.
I can't take too much time to investigate all this in detail right now, but I did mean to suggest that perhaps, 19th Century materials, or anyway stuff that could reasonably have been developed in that time frame without revolutionary advances in general tech level, might be able to provide the raw rocket thrust needed to put something massing a few tons into LEO. Then the question of what kind of spacecraft could be useful in orbit comes up, and obviously except for a mere stunt of putting some inert object into orbit to point at, it would have to be manned to accomplish anything. And that implies either crazy kamikaze scientists who know their orbit is a prelude to suicide, or a means of surviving reentry.
Fortunately I do think that a practical reentry capsule does not require any highly advanced materials. In a pinch cork can serve as an ablative heat shield. What is precocious is the realization in advance that only ballistic reentry is feasible, and doing the math to predict how much ablative is needed and exactly what limited range of reentry angles would be survivable. For orbital maneuvering and control, more pressurized HTHP/fuel mix rockets ought to fit the bill.
For the crew to control the rocket on its way up, by the late 19th century I think electric tech is developed enough that some sort of analog voltage based signal wires can command solenoids to control the valves of lower stage rocket engines, and to command blowing off exhausted lower stages and switch over to controlling the next stage up. A pressure meter can signal the tank pressure of a pressure fed stage; when the last of the propane is boiled off, it would be time to ditch it, and once that reserve is gone, the pressure in the combined tanks would start to fall. If pre-calculation is done correctly, this will happen just as the last of the peroxide is blown out of its chamber.
Note that propane was not isolated and identified as a separate molecule until 1910 OTL. Hydrogen peroxide would also have to be precociously studied and developed.
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Using my free version of RPA software, and assuming ambient temperature propane liquefies at about 5 atmospheres, it seems vacuum ISP would be about 230 sec, and 175 sec at sea level if the mass ratio of peroxide to propane is about 5.5--amazingly low. The software crashed but IIRC chamber temperatures would be in the range of 2300 K.
If we could make a propellant pump achieving 10 atmospheres chamber pressure, and switch to using kerosene, at mass ratio 6 we get about 294 sec in vacuum and 204 at sea level, with chamber temperature under 2900 K and exhaust temperature under 1900.
The latter is really quite as good as early 1960s rockets and I suppose somewhere I must have done something unreasonable to get the outcome.
The former is sadly mediocre though of course really good for 19th century tech. Overall propellant density for the propane rocket would be about 1.122 tons/cubic meter. With a safety factor of 2 for a 5 atmosphere nominal pressure and assuming a steel that can hold 90,000 pounds/square inch tensile stress, a cylinder section 1 meter long and in diameter would need to be about 3.2 hundredths of an inch thick, such a section of pipe would thus mass about 22.5 kg while enclosing 881 kg of propellant. Rounding up the former to 25 kg to allow for auxiliary masses (such as an inner tube separating the fuel from the oxidant) and the latter up to 900 for convenience, we have a ratio of 36 to 1 for structure versus content mass. That is really very good, and I suspect that engine mass (despite the simplicity of a pressure fed system) and necessary auxiliary masses would bring the mass ratio at least up to 1 in ten. At any rate we can see some margin for higher pressure, but I think 5 atm is already high for a storage temperature of 5 C, which is desired to stabilize the peroxide.
With 3 stages, and nominal vacuum ISP but a need to reach "mission delta-V" of 10,000 we would need a given stage to mass 5.62 times its upper stack load. Thus, to put 5 tons into LEO, we'd need a third stage massing 28 tons, a second stage massing 186 tons, and a first stage massing 1231.2 tons for an all up stack of 1450, about half a Saturn V rocket! Thrust would need to be something like 15 megaNewtons on the first stage, implying a mass flow of 8.74 tons per second, thus a burn time of 128.1 seconds with real ISP varying between 175 and say 220 sec, call it 200 for 17.15 MN.
With a kerosene pumped version, a 6:1 prop/fuel mass ratio, propellant per unit volume is about 1.32, and the stages would mass 252.2 tons, 62.12, and 15.3 for a total stack mass of 334.62 tons. Something of comparable capacity to a Saturn 1B would mass about 1200 tons.
With about a dozen or so launches of those, assuming the Victorians can accomplish a workable sort of space suit and good precision docking by eyeball control it might be possible to assemble an Apollo-like EOR/LOR moon landing mission. I'd be very worried about the ability of pilots trying to land a lander on the Moon by eyeball alone!
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Using my free version of RPA software, and assuming ambient temperature propane liquefies at about 5 atmospheres, it seems vacuum ISP would be about 230 sec, and 175 sec at sea level if the mass ratio of peroxide to propane is about 5.5--amazingly low. The software crashed but IIRC chamber temperatures would be in the range of 2300 K.
If we could make a propellant pump achieving 10 atmospheres chamber pressure, and switch to using kerosene, at mass ratio 6 we get about 294 sec in vacuum and 204 at sea level, with chamber temperature under 2900 K and exhaust temperature under 1900.
The latter is really quite as good as early 1960s rockets and I suppose somewhere I must have done something unreasonable to get the outcome.
The former is sadly mediocre though of course really good for 19th century tech. Overall propellant density for the propane rocket would be about 1.122 tons/cubic meter. With a safety factor of 2 for a 5 atmosphere nominal pressure and assuming a steel that can hold 90,000 pounds/square inch tensile stress, a cylinder section 1 meter long and in diameter would need to be about 3.2 hundredths of an inch thick, such a section of pipe would thus mass about 22.5 kg while enclosing 881 kg of propellant. Rounding up the former to 25 kg to allow for auxiliary masses (such as an inner tube separating the fuel from the oxidant) and the latter up to 900 for convenience, we have a ratio of 36 to 1 for structure versus content mass. That is really very good, and I suspect that engine mass (despite the simplicity of a pressure fed system) and necessary auxiliary masses would bring the mass ratio at least up to 1 in ten. At any rate we can see some margin for higher pressure, but I think 5 atm is already high for a storage temperature of 5 C, which is desired to stabilize the peroxide.
With 3 stages, and nominal vacuum ISP but a need to reach "mission delta-V" of 10,000 we would need a given stage to mass 5.62 times its upper stack load. Thus, to put 5 tons into LEO, we'd need a third stage massing 28 tons, a second stage massing 186 tons, and a first stage massing 1231.2 tons for an all up stack of 1450, about half a Saturn V rocket! Thrust would need to be something like 15 megaNewtons on the first stage, implying a mass flow of 8.74 tons per second, thus a burn time of 128.1 seconds with real ISP varying between 175 and say 220 sec, call it 200 for 17.15 MN.
With a kerosene pumped version, a 6:1 prop/fuel mass ratio, propellant per unit volume is about 1.32, and the stages would mass 252.2 tons, 62.12, and 15.3 for a total stack mass of 334.62 tons. Something of comparable capacity to a Saturn 1B would mass about 1200 tons.
With about a dozen or so launches of those, assuming the Victorians can accomplish a workable sort of space suit and good precision docking by eyeball control it might be possible to assemble an Apollo-like EOR/LOR moon landing mission. I'd be very worried about the ability of pilots trying to land a lander on the Moon by eyeball alone!
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You don't actually need rocketry. A spaceship able to reach orbit powered by rapid-fire conventional explosives is perfectly feasible with late 19th Century technology... but it would be a bone-rattling ride!
It was basically done in the book King David's Spaceship.
It was basically done in the book King David's Spaceship.
Deleted member 94708
Let's assume that with a POD in Mongolia in 1000 or so, the Mongolian demographic boom which IOTL manifested itself in a continent-spanning empire instead spends itself in inter-tribal warfare. The Mongol still press the Jin hard, but not hard enough to cause a collapse.
The Song, having as IOTL lost the most densely populated parts of the North China Plain to the Jin, are ITTL in a position to continue the slow development of labor-saving and photo-industrial technologies which they had begun IOTL. While Chinese natural philosophy was such that it would be extremely difficult for a scientific mindset to take root, an engineering tradition develops and spreads through trade to India and the Middle East.
The same POD which has saved China also saves Baghdad, and Islam maintains the traditions of open inquiry and engineering expertise that it has before the devastation of the Fertile Crescent.
Europe, which isn't hit by the Black Death due to the lack of a Mongol Empire, nonetheless suffers a severe demographic collapse by 1400 as Malthusian realities catch up with the over-populated continent. Thus both the Islamic and Christian worlds are well-primed to accept a new engineering and industrial paradigm, and both maintain, as OTL, the philosophical underpinnings necessary to develop a true scientific method.
It's reasonable to assume that Chinese proto-industrial technology has been introduced as to some degree in both by 1500, which means that all three of the centers of Old World civilization (four with India) have access to a technological package which by all accounts varied between "Netherlands in 1650" and "England in 1800" depending on the individual technology in question.
It's not going to take Europe or the Islamic World very long to build on this to develop a scientific mindset as to why these technologies work this way, which will in turn filter back to the Chinese. I would guess that by 1700 all four regions have something resembling the scientific method as it stood in 1800 Europe IOTL, and the Chinese are probably still divided in two as neither the Song nor the Jin was in danger of falling without Mongol intervention, meaning that neither can simply withdraw from the world on the model of the OTL Qing without the other overtaking it.
The effect is going to be that, while the transition from Industrial Revolution to Scientific Method is slower and more haphazard than IOTL, scientific progress will move more quickly afterward. It is possible that the progress that took place IOTL between 1800 and 1960 could take place ITTL between 1720 and 1860. The details of such a world would be difficult to guess at due to the sheer quantity of butterflies but it's certainly within the realm of possibility that such a world reaches space well before 1900.
The Song, having as IOTL lost the most densely populated parts of the North China Plain to the Jin, are ITTL in a position to continue the slow development of labor-saving and photo-industrial technologies which they had begun IOTL. While Chinese natural philosophy was such that it would be extremely difficult for a scientific mindset to take root, an engineering tradition develops and spreads through trade to India and the Middle East.
The same POD which has saved China also saves Baghdad, and Islam maintains the traditions of open inquiry and engineering expertise that it has before the devastation of the Fertile Crescent.
Europe, which isn't hit by the Black Death due to the lack of a Mongol Empire, nonetheless suffers a severe demographic collapse by 1400 as Malthusian realities catch up with the over-populated continent. Thus both the Islamic and Christian worlds are well-primed to accept a new engineering and industrial paradigm, and both maintain, as OTL, the philosophical underpinnings necessary to develop a true scientific method.
It's reasonable to assume that Chinese proto-industrial technology has been introduced as to some degree in both by 1500, which means that all three of the centers of Old World civilization (four with India) have access to a technological package which by all accounts varied between "Netherlands in 1650" and "England in 1800" depending on the individual technology in question.
It's not going to take Europe or the Islamic World very long to build on this to develop a scientific mindset as to why these technologies work this way, which will in turn filter back to the Chinese. I would guess that by 1700 all four regions have something resembling the scientific method as it stood in 1800 Europe IOTL, and the Chinese are probably still divided in two as neither the Song nor the Jin was in danger of falling without Mongol intervention, meaning that neither can simply withdraw from the world on the model of the OTL Qing without the other overtaking it.
The effect is going to be that, while the transition from Industrial Revolution to Scientific Method is slower and more haphazard than IOTL, scientific progress will move more quickly afterward. It is possible that the progress that took place IOTL between 1800 and 1960 could take place ITTL between 1720 and 1860. The details of such a world would be difficult to guess at due to the sheer quantity of butterflies but it's certainly within the realm of possibility that such a world reaches space well before 1900.
Well, have you ever seen Pournelle or anyone else doing the math on that?
Basically, using explosives is tantamount to making a solid fuel rocket. Despite low Isp, solids have good mass fraction, so it is conceivable that 19th century experimenters might hit upon a suitable solid formulation to get the job done.
Solid fuels and explosives are not the same thing though. To get all the chemicals to combine very rapidly so as to get a big sudden bang, explosives use a lot of nitrogen compounds that tend to be able to release a lot of energy very fast, but overall their efficiency in terms of energy per unit volume is less than fuel/oxidant mixes can achieve. This is why we don't power automobiles with dynamite! (Well, that and the fact that air-breathing engines don't have to haul their oxidant along, whereas solid fuel rockets do--but still, one is better off fueling a rocket with kerosene than nitroglycerine). Not to mention avoiding the whole detonation rattling hassle!
If one has good explosives to hand and does not have a good solid fuel mix, or liquid propellant rockets, then maybe in a pinch a succession of explosions can get the job done. Certainly Pournelle was alluding to the scale model firing tests of the Orion concept; propulsion can be achieved that way which was the point, but even though explosive charges might achieve a very good mass fraction (due to casing and detonators not massing much compared to the mass of explosive contained in them) their effective ISP would be so low I doubt any practical assembly can actually reach orbit. Pile enough on and eventually you can do it, but the contraption in KDS was probably far too small; a suitable stack would rival the Great Pyramid of Giza in size I'd guess. Look at what a dramatic difference the gap between 230 and 290 sec ISP made with my hydrogen peroxide suggestions!
Blasting to orbit on cordite might be more practical (assuming cordite does not require air, otherwise we'd be talking about nitroglycerine or TNT I suppose) than developing pumped peroxide rockets at that. But I think the numbers would be prohibitive.
No but as you say they tested the basic idea with the "Putt-Putt" (the nickname for Orion being "Bang Bang").
I found a video of "Putt-Putt" in action.
I also found Goddard's patent for an explosive-powered craft circa 1914.
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I did say that. What they were testing was the question of whether a craft propelled by successive explosions would be controllable or not, not developing an efficient rocket system.
Here is an article on the concept of energy density, including a table listing it for many substances. TNT has energy density of 4.6 MJ/kg; kerosene is ten times that, 46 MJ/kg.
Now then imagine a spacecraft propelled by successive TNT explosions. Say we have the 5 ton capsule I suggested might be adequate, and it has a 1 ton gun on a spring attached to it. The gun has an ingenious mechanism that automatically loads in another explosive charge of TNT (with detonator built in) into the breech of the gun, that has a door that is opened for loading when the gun recoils against the spring, takes the next charge, closes and locks the breech, and detonates the charge when the spring has expanded to zero stress extension. Compressing the spring to full with this size charge takes 1/2 second. The charges thus explode once per second, and propel the whole six ton arrangement at 10 meters/sec^2 average acceleration. To push 6000 kg at that rate, each charge must deliver 60,000 Newton-seconds of impulse.
At 4.6 MJ per kg, from kinetic energy = 1/2 mass*velocity squared, we can see that detonating 1 Kg of the stuff releases enough energy to propel its own mass to 3033.15 m/sec. Thus a 20 kilogram charge is the right size to get the needed recoil on the gun.
This does not admittedly look so bad. With the charge blasting out of the gun at 3 km sec, we appear to have an ISP of 309 seconds!
Well now look at kerosene, credited with ten times the energy "stored" in it. Actually if we read the description of the table, this means how much energy would be released if were burned with the necessary mass of oxygen to combust it all, and does not count that mass. If a unit of a hydrocarbon has about 2 hydrogen atoms and one carbon, its molecular weight is 14, while it would need 3 oxygen atoms massing 16 AMU each. Note that realistic rocket engines rarely burn at the perfect stoichiometric ratio, preferring to be a bit fuel rich. Let's suppose we use 9/10 the stoichiometric ratio of oxygen, for 9/10 the energy release, we now have 41.4 MJ for 4.086 kg of material, or only 10.132 MJ/kg. That still amounts to a velocity of 4502 meters/sec. Ideally. But a realistic kerosene-oxygen rocket does very well indeed to get a nozzle exit velocity as high as 3500 m/sec. But that is still better than 3 km/sec!
This suggests that there may be serious problems I had not allowed for in the TNT gun rocket idea, aside from all the mechanical issues involved with guaranteeing the loading/latching/firing mechanism works. Perhaps for instance a realistic gun barrel will not capture a big fraction of the theoretical exhaust energy available; it would take an infinite nozzle to convert all the thermal energy theoretically available to collimated kinetic energy directed back on the axis. Our intuition tells us even if the gun barrel is fairly long and shaped like an efficient nozzle, what comes out is a puff of very hot dense gas that has a lot of expansive energy left in it--that energy is not contributing to the impulse, which is therefore lower than 3 km/sec effectively. In fact we may be up against some fundamental thermodynamics--a big portion of the energy is entropic and not available to harnessed by any means perhaps. A realistic high efficiency kerosene-oxygen rocket is presumably losing a similar portion of its total energy. If in theory (disregarding thermodynamics) the exhaust could have been a mass at absolute zero temperature moving back at 4500 m/sec, but we really get a hot gas with net backward speed of 35, the speed ratio is 7/9 and in energy terms, that is squared, or 49/81, or just 60 percent of the total energy harnessed to useful thrust. If a similar ratio holds for the same fundamental reasons for the TNT blast drive, the real muzzle velocity of the gas bolus would be 2360 m/sec, and the necessary mass of the charge would be 25.42 kg instead; we'd use up a ton in less than 40 seconds, not 50. That is an Isp of over 240 sec to be sure! So not as good as a mediocre ker-lox rocket, but comparable to von Braun's alcohol-oxygen V-2 engine or all but the most efficient peroxide engines.
I suspect the real ISp, even in a very efficiently shaped gun, would be lower than 240, because high-efficiency ker-lox engines like Russian-made staged combustion engines (we never went for such high Isp in our ker-lox engines here in the States) are working very close to equilibrium, whereas explosions are an example of non-equilibrium processes that inherently produce higher entropy, which is a way of restating they are irreversible processes.
This TNT gun works in vacuum of course. For a realistic launching system, it needs to operate at much higher thrusts, against the atmosphere, which will stall the exhaust somewhat and rob it of more thrust. We need a bigger gun, able to take much bigger charges, and the right size and rate of charges for launching from the ground would be far greater than later phases where half or more of the total magazine of charges has been emptied already.
My computer is too rickety for me to risk running videos on it, but from what I know of Orion, the system demonstrated in the test is a model of the Orion concept, which is a lot less efficient than putting a charge in the breech of a good nozzle-shaped gun and firing it. They could have done an efficient gun for this test and that's probably what some ATl society trying to launch spacecraft on chemical explosions would do, but the idea was to model Orion, where the notion of making a gun to enclose a fission explosion was absurdly impossible; the curved reflector plate concept itself was almost inconceivable until empirical experiences at testing sites demonstrated that solid materials could be protected from being destroyed by nearby nuclear fireballs. Thus, the model shares an inherent inefficiency of Orion, which is that much of the blast will miss the plate completely and what does hit it is inefficiently bounced off at a less than perfectly efficient angle. This will also eat into the effective Isp of any design taking advantage of the simplicity of the plate rather than investing in a collimating gun.
I'd be willing to bet at this point that even a more efficient design than Jerry Pournelle had the desperate natives of Prince Samuel's World bung together would at any rate be far less efficient even than the poor propane pressure driven thing I suggested, not to mention that any mechanical failure spells doom for any crew, if they can indeed survive the battering that a succession of hard bangs will give them, springs or not. The magazine to hold enough explosive charges to put them into orbit will have a large empty mass, unless they stage several sized gun driven stages one after another--as they might have to, since designing for a given thrust is hard enough, but enabling a variable thrust is worse.
Be very steampunk neat if someone can prove me wrong though!
Deleted member 97083
The "beneficial" societal effects after the end of the Black Death were due to the high land-per-person ratio and resources-per-person ratio after the epidemics, which increased peasant wages and urban rights after sudden increases in the price of labor. If the Black Death were replaced by Malthusian collapse, where the population reaches a peak and stays there due to constant mass death, it would have been solely a bad thing and none of the advancing social effects and weakened nobility would have occurred. In fact nobility would be stronger than ever, while being more focused on pillaging their population and exploiting cheap labor rather than investing in new "industries".
However, the Black Death could still happen without the Mongols, there had been plenty of plagues before.
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Trying to move the goalposts by postulating ATLs where 1960s tech exist before 1900 strikes me as cheating the spirit if not letter of the challenge. Obviously if someone imagines a TL where our whole modern technical suite all exists in the year 1000, then a moon landing in 1100 is no big deal--we'd be asking "what's the delay?" instead. The name of the game I think is to figure out how to get someone in orbit (and return them) in a situation where the phonograph and motion pictures are just being invented, and radio is mostly speculations on blackboards, and radioactive decay is just being discovered.
I have seen other challenges along this line take the position that nuclear fission is developed early, but since atomic rockets (at least of the type we can actually make) are really not much good for boosters (too much mass for the core, even if we suicidally operate without shielding) I don't think that even helps.
I have seen other challenges along this line take the position that nuclear fission is developed early, but since atomic rockets (at least of the type we can actually make) are really not much good for boosters (too much mass for the core, even if we suicidally operate without shielding) I don't think that even helps.
Deleted member 94708
Probably, but...
I don't see any conceivable reason, regardless of technical feasibility, as to WHY a 19th century society similar to OTL would ever actually try to launch something into space.