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Post by Enderminion on Apr 11, 2017 14:48:18 GMT
above 9.6Mt the cost explodes because you need plutonium to get 10.2Mt bombs
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Post by Zerraspace on Apr 11, 2017 14:48:37 GMT
newageofpower: Yeah, that is how I was trying to set it up. It's why the larger missiles have nuclear drives where the others don't - the cost of the nuclear drive barely puts a dent in it.
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blkcandy
Junior Member
Burn complete. Crawling back to bed.
Posts: 78 
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Post by blkcandy on Apr 12, 2017 0:05:35 GMT
Because human takes a lot of space, energy, heat, everything, and is one of the worstweak point on a warship. We remove them from the Warship and create 'capital ship class drone' instead.  Javeline Capital Wardrone, 55.9 tons wet and 30.9 tons dry, armed with 10MWe class weapons: three 3.3MWe microflak railguns and a 10MWe laser. Its primary defense is 9 tons of umbrella shield. The shield diameter is 11.5 while the drone total diameter without the umbrella is only 7.43m, the umbrella is more than wide enough to cover the whole drone including its radiators. But what make this drone stood out is not the drone itself, but the achievement of the drone compacting technology:  Our engineers have successfully put a Ø11.5x34.5m (Ø7.43x31 with umbrella removed) drone inside a Ø1.09x34.5m storage capsule made of lithium. And it is stored in a ready to launch state. |
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Post by Rocket Witch on Apr 12, 2017 0:27:13 GMT
For a variety of reasons external to gameplay itself, refuse to ever work with anything remotely involving fluorine. That stuff is a storage accident waiting to happen, and you’ve got to wonder where it’s coming from. For similar acquisition reasons, I’m tetchy about hydrogen deuteride and decane, but have mostly accepted the latter – if you have access to methane, you can produce all the other hydrocarbons industrially from a similar mass. Fluorine is reasonably common (it's rare for a light element, but not rare overall) with a similar abundance to cobalt and copper, and can be extracted from minerals without particular difficulty and stored in steel containers... not that it isn't an accident waiting to happen. Hydrogen deuteride can be extracted from the atmospheres of Uranus and Neptune, similar to how the methane depot is depicted in the story mission. It may be expensive but not prohibitively so, like xenon today in reality. |
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Post by newageofpower on Apr 12, 2017 8:32:04 GMT
ZerraspaceDo note we produce and use industrial quantities of RP1. If you can make dodecane (RP-1), you can probably manufacture Decane as well.
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Post by Enderminion on Apr 12, 2017 10:27:09 GMT
newageofpower, We COULD produce industrial quantities of RP-1 but they it's rare because they are used for rocket propellant only (Rocket Propellant One)
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Post by Zerraspace on Apr 12, 2017 10:55:43 GMT
newageofpower I did say " if you have access to methane, you can produce all the other hydrocarbons industrially from a similar mass." Theoretically speaking, 10CH4 -> C10H22 + 9H2, you can get 887.5 grams or so of decane from a single kilogram of methane and the rest is all hydrogen you can use anyway. That I’m okay with, because we preserve all the mass (and even if we didn't use the hydrogen, that's not a lot of waste) and it comes from a compound that's easy to find. As for fluorine and hydrogen deuteride, in regards to Rocket Witch's comment, they require a lot more effort. In terms of elements overall, yes, fluorine isn’t terribly rare, but there isn’t any place that’s swimming in it. With the exception of the light metals/metalloids (lithium, beryllium and boron), it is the least abundant of the first 20 elements by nearly an order of magnitude. To quote Wikipedia, " Among the lighter elements, fluorine's abundance value of 400 ppb (parts per billion) – 24th among elements in the universe – is exceptional: other elements from carbon to magnesium are twenty or more times as common," and it appears to have a similar solar abundance. This would suggest that to get a single ton of the stuff, you’d have to sift through 2.5 million tons of material, but that's neglecting that most of the mass of the solar system is hydrogen and helium which is mostly in the gas giants and sun -abundance outside these bodies would probably cut that figure by a tenth or hundred, which seems reasonable considering further that it's about 1/10000th as abundant as oxygen (most common non-H/He element) - plus you wouldn't be mining for pure fluorine but one of its compounds. That in itself might not sound so bad, considering we go for far more for certain metals currently, but considering it is basically going to be thrown away, and all the other primary propellants (water, hydrocarbons and hydrogen) can be obtained from compounds that make up the primary composition of several bodies (tenths or more of the surface) and form significant ice reserves/atmospheric gasses even where they aren’t ubiquitous, it seems like quite a bit of hassle. Regarding the other, extracting anything from gas giants is an enormous undertaking due to the gravity wells. Even for Uranus and Neptune, you’re looking at 18-19 km/s of delta-v just to make it out of the atmosphere and into a low orbit. For a 9 km/s hydrogen rocket, that’s a mass ratio of 8.26, and you’d have to expend an enormous amount of propellant for whatever it is you’re bringing out. Now, thankfully the local atmosphere is already mostly hydrogen to grab from, and you can cancel out a good part of that by merely skimming the atmosphere from a low orbit using an atmospheric scoop, but reducing losses means operating high up in the atmosphere which will require a huge number of trips to get anything significant, and that still leaves boosting from aerobraking to a circular orbit then to the nearest moon. Around Uranus, you need 3.94 km/s to boost from a 1000 km circular orbit to get to the nearest moon Cordelia, and 7.08 km/s to get to Miranda (the nearest major moon); around Neptune, you need 4.32 km/s to boost from a 1000 km circular orbit to get to the nearest moon Naiad, and 8.75 km/s to get to Triton. On top of that, hydrogen deuteride is not a major component – 0.01% or less – so your scoop is going to pick up a ton of accessory mass that will have to be sifted through, most of which is regular hydrogen. That in itself is also a problem (though much much less of one) for obtaining methane, and while I’d certainly consider it more worthwhile, if I wanted huge quantities of it I’d rather just get it from Titan or manufacture it from carbon-based compounds and water ice on carbonaceous asteroids, which have the further benefit of being more accessible to the solar system at large (both in delta-v and time), and in the case of the latter, being achievable with solar power. The alternative means of obtaining hydrogen deuteride is to skim through any hydrogenated fluid on other bodies (ubiquitious water ice or hydrocarbons – neither hard to find) and isolating the hydrogen, as a minute fraction of that will be deuterium. You will then have to use a centrifuge or mass spectrometer to separate the two isotopes. That in itself is a bit of work (it's mostly limited to nuclear facilities at present), but the real challenge thereafter is getting the two to mix in a one-to-one ratio; hydrogen and deuterium will react in each other’s presence to form hydrogen deuteride, but it’s a reversible reaction: books.google.com.lb/books?id=UXKw_xJLdYAC&pg=PA97&lpg=PA97&dq=forming+hydrogen+deuteride&source=bl&ots=W6Dcofs8JU&sig=jxXhZ25gvUU5I3GBAxtmynbjsEE&hl=en&sa=X&ved=0ahUKEwiqkquNz57TAhVDORQKHZqnAJUQ6AEIQDAF#v=onepage&q=forming%20hydrogen%20deuteride&f=falseAgain, it seems like a lot of unnecessary work considering how easy it is to get regular hydrogen - which you'll always find lots more of in the process of trying to get the hydrogen deuteride anyway. Obtaining fluorine and HD is less an issue of “ can it be done” (it can, I agree with you there), but rather “ is it worth it when other compounds are so much easier to find in quantity?” That is a somewhat more subjective argument. I'm inclined to think it isn't.
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Post by bigbombr on Apr 12, 2017 12:46:26 GMT
newageofpower I did say " if you have access to methane, you can produce all the other hydrocarbons industrially from a similar mass." Theoretically speaking, 10CH4 -> C10H22 + 9H2, you can get 887.5 grams or so of decane from a single kilogram of methane and the rest is all hydrogen you can use anyway. That I’m okay with, because we preserve all the mass (and even if we didn't use the hydrogen, that's not a lot of waste) and it comes from a compound that's easy to find. As for fluorine and hydrogen deuteride, in regards to Rocket Witch's comment, they require a lot more effort. In terms of elements overall, yes, fluorine isn’t terribly rare, but there isn’t any place that’s swimming in it. With the exception of the light metals/metalloids (lithium, beryllium and boron), it is the least abundant of the first 20 elements by nearly an order of magnitude. To quote Wikipedia, " Among the lighter elements, fluorine's abundance value of 400 ppb (parts per billion) – 24th among elements in the universe – is exceptional: other elements from carbon to magnesium are twenty or more times as common," and it appears to have a similar solar abundance. This would suggest that to get a single ton of the stuff, you’d have to sift through 2.5 million tons of material, but that's neglecting that most of the mass of the solar system is hydrogen and helium which is mostly in the gas giants and sun -abundance outside these bodies would probably cut that figure by a tenth or hundred, which seems reasonable considering further that it's about 1/10000th as abundant as oxygen (most common non-H/He element) - plus you wouldn't be mining for pure fluorine but one of its compounds. That in itself might not sound so bad, considering we go for far more for certain metals currently, but considering it is basically going to be thrown away, and all the other primary propellants (water, hydrocarbons and hydrogen) can be obtained from compounds that make up the primary composition of several bodies (tenths or more of the surface) and form significant ice reserves/atmospheric gasses even where they aren’t ubiquitous, it seems like quite a bit of hassle. Regarding the other, extracting anything from gas giants is an enormous undertaking due to the gravity wells. Even for Uranus and Neptune, you’re looking at 18-19 km/s of delta-v just to make it out of the atmosphere and into a low orbit. For a 9 km/s hydrogen rocket, that’s a mass ratio of 8.26, and you’d have to expend an enormous amount of propellant for whatever it is you’re bringing out. Now, thankfully the local atmosphere is already mostly hydrogen to grab from, and you can cancel out a good part of that by merely skimming the atmosphere from a low orbit using an atmospheric scoop, but reducing losses means operating high up in the atmosphere which will require a huge number of trips to get anything significant, and that still leaves boosting from aerobraking to a circular orbit then to the nearest moon. Around Uranus, you need 3.94 km/s to boost from a 1000 km circular orbit to get to the nearest moon Cordelia, and 7.08 km/s to get to Miranda (the nearest major moon); around Neptune, you need 4.32 km/s to boost from a 1000 km circular orbit to get to the nearest moon Naiad, and 8.75 km/s to get to Triton. On top of that, hydrogen deuteride is not a major component – 0.01% or less – so your scoop is going to pick up a ton of accessory mass that will have to be sifted through, most of which is regular hydrogen. That in itself is also a problem (though much much less of one) for obtaining methane, and while I’d certainly consider it more worthwhile, if I wanted huge quantities of it I’d rather just get it from Titan or manufacture it from carbon-based compounds and water ice on carbonaceous asteroids, which have the further benefit of being more accessible to the solar system at large (both in delta-v and time), and in the case of the latter, being achievable with solar power. The alternative means of obtaining hydrogen deuteride is to skim through any hydrogenated fluid on other bodies (ubiquitious water ice or hydrocarbons – neither hard to find) and isolating the hydrogen, as a minute fraction of that will be deuterium. You will then have to use a centrifuge or mass spectrometer to separate the two isotopes. That in itself is a bit of work (it's mostly limited to nuclear facilities at present), but the real challenge thereafter is getting the two to mix in a one-to-one ratio; hydrogen and deuterium will react in each other’s presence to form hydrogen deuteride, but it’s a reversible reaction: books.google.com.lb/books?id=UXKw_xJLdYAC&pg=PA97&lpg=PA97&dq=forming+hydrogen+deuteride&source=bl&ots=W6Dcofs8JU&sig=jxXhZ25gvUU5I3GBAxtmynbjsEE&hl=en&sa=X&ved=0ahUKEwiqkquNz57TAhVDORQKHZqnAJUQ6AEIQDAF#v=onepage&q=forming%20hydrogen%20deuteride&f=falseAgain, it seems like a lot of unnecessary work considering how easy it is to get regular hydrogen - which you'll always find lots more of in the process of trying to get the hydrogen deuteride anyway. Obtaining fluorine and HD is less an issue of “ can it be done” (it can, I agree with you there), but rather “ is it worth it when other compounds are so much easier to find in quantity?” That is a somewhat more subjective argument. I'm inclined to think it isn't. This is why I use methane as propellant. It has a good performance in NTR's, resistojets and high power MPDT's, is cheap, denser than hydrogen and it one of the most credible propellants. Capturing methane or making it with the Sabatier proces seems easier than industrial scale production of decane or RP-1. Getting worthwhile amounts of noble gasses is also much more of a hassle. The only propellants that are more accessible (that I can name at the moment) are water and CO2, both which produce considerably lower exhaust velocities. |
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Post by Enderminion on Apr 12, 2017 13:07:49 GMT
if you have methane you can make decane though
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Post by bigbombr on Apr 12, 2017 13:11:27 GMT
if you have methane you can make decane though More steps, more energy required, more infrastructure required. |
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Post by Zerraspace on Apr 12, 2017 13:22:00 GMT
Well, out-of-game, hydrocarbons do have the rather major disadvantage that the dissociated carbon would deposit on the chamber walls as a difficult-to-clean-off soot which would probably impact functioning if you left it for too long (though I do wonder how that would work out if your walls are already diamond or amorphous carbon). However, since nuclear reactors need to be opened up occasionally for maintenance and replacement/processing of the fuel rods anyway, and I'd imagine that a spaceship crew has several months of spare time between burns to fill with stuff to do (like looking over every part and keeping it in tip top form), I think that's bearable.
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Post by newageofpower on Apr 12, 2017 15:53:53 GMT
Given that Europa's oceans contain more water than Earth's, Heavy Water (and thus HD) should be readily available in industrial quantities. There are other bodies where water ice is common, though I do agree most craft would be using Hydrogen rather than HD.
Flourine is far more common than noble metals or even many alloying agents, though fuelling entire fleets of warships with this stuff would deplete known deposits rather quickly, due to the sheer quantities involved. That being said, known reserves of Flourite are estimated around 230 million tons on Earth alone, so the concept of HF submunitions carried aboard nuclear-thermal methane drone buses is hardly implausible.
In fact, with advances in storage technology one could use molten lithium hydride + flourine rocketry for even more efficacy
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Post by Zerraspace on Apr 12, 2017 16:07:12 GMT
Knew that was coming up!  If we're going to go with tripropellants, I want H2/O2/Be rockets - specific impulse is pretty close to H2/F2/Li but quite a bit less dangerous. Let's ignore for the moment my own argument - that beryllium is way rarer than any of these, and we really shouldn't be using such a valuable metal as rocket propellant. |
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Post by theholyinquisition on Apr 13, 2017 3:54:53 GMT
Knew that was coming up! If we're going to go with tripropellants, I want H2/O2/Be rockets - specific impulse is pretty close to H2/F2/Li but quite a bit less dangerous. Let's ignore for the moment my own argument - that beryllium is way rarer than any of these, and we really shouldn't be using such a valuable metal as rocket propellant. Actually, if I may quote from Ignition! An Informal History of Liquid Rocket Propellants: "G. M. Beighley, at Aerojet, tried another approach, this one resembling the usual bi-propellant arrangement. His two propellants were liquid hydrogen and a slurry of powdered beryllium metal in liquid oxygen. He was able to report his results by 1966, and they were not encouraging. He never got more than 70 percent combustion efficiency, and was plagued by "burnbacks" of his Be-O2 slurry through the injector. It's really surprising that he didn't manage to kill himself.
At any rate, he didn't continue the work, and as little has been heard of the Be-H-O system in the last few years, it is probably dead. When the combustion difficulties are added to the toxicity of BeO and the price of beryllium, there isn't really much point in continuing with it. "
So, yeah, when the man who worked in propellant chemistry from 1948 until the 1960s says it won't work, it probably won't work. |
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Post by ash19256 on Apr 13, 2017 15:43:36 GMT
Knew that was coming up! If we're going to go with tripropellants, I want H2/O2/Be rockets - specific impulse is pretty close to H2/F2/Li but quite a bit less dangerous. Let's ignore for the moment my own argument - that beryllium is way rarer than any of these, and we really shouldn't be using such a valuable metal as rocket propellant. Actually, if I may quote from Ignition! An Informal History of Liquid Rocket Propellants: "G. M. Beighley, at Aerojet, tried another approach, this one resembling the usual bi-propellant arrangement. His two propellants were liquid hydrogen and a slurry of powdered beryllium metal in liquid oxygen. He was able to report his results by 1966, and they were not encouraging. He never got more than 70 percent combustion efficiency, and was plagued by "burnbacks" of his Be-O2 slurry through the injector. It's really surprising that he didn't manage to kill himself.
At any rate, he didn't continue the work, and as little has been heard of the Be-H-O system in the last few years, it is probably dead. When the combustion difficulties are added to the toxicity of BeO and the price of beryllium, there isn't really much point in continuing with it. "
So, yeah, when the man who worked in propellant chemistry from 1948 until the 1960s says it won't work, it probably won't work.Well, what if we changed that setup so that the beryllium powder was in the Hydrogen instead of in the Oxygen? Sure, you wouldn't be able to use regenerative cooling unless you were using a material that didn't oxidize for a nozzle without risk of either the nozzle oxidizing through or having a buildup of beryllium deposits in the channels, but you wouldn't have that burnback issue, because there isn't any oxygen in the H2/Be slurry, and the O2 doesn't have any fuel in it. And non-regeneratively cooled engines are already a thing IRL (see also, RL-10B2, IIRC). Alternatively, you could have it so that the Be-H2 slurry isn't pre-mixed in the tank, but the Be powder is instead added on the way to the engine, and some of the hydrogen is routed around the powder adding system and instead used to regeneratively cool the engine. |
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If we're going to go with tripropellants, I want H2/O2/Be rockets - specific impulse is pretty close to H2/F2/Li but quite a bit less dangerous. Let's ignore for the moment my own argument - that beryllium is way rarer than any of these, and we really shouldn't be using such a valuable metal as rocket propellant.
