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Post by Kerr on Sept 9, 2017 16:09:09 GMT
Let's assume it is. How does that really matter? if you don't compress it fast enough it explodes, also the injection parts must be kept cool Compress what fast enough? The fusion pellet? The injection parts also have to be kept if you use regular frozen hydrogen isotopes. |
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Post by Enderminion on Sept 9, 2017 16:12:58 GMT
meh I am not a nuclear engineer
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Post by ironclad6 on Sept 9, 2017 19:55:01 GMT
If I read this correctly then I need to A) reduce the speculated thrust power on my ships to 34% if what I presently have to account for losses to bremstrahlung and increase the amount of radiation my crew presently enjoy or 2) Switch to another form of propulsion?
Or is high thrust fusion propulsion basically impossible?
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Post by Kerr on Sept 9, 2017 20:05:39 GMT
If I read this correctly then I need to A) reduce the speculated thrust power on my ships to 34% if what I presently have to account for losses to bremstrahlung and increase the amount of radiation my crew presently enjoy or 2) Switch to another form of propulsion? Or is high thrust fusion propulsion basically impossible? 3) TBH this is actually making me not want to write this novel. I feel bad for having de-railed this thread too. Is there any chance we can get this split out from the original thread? A good story doesn't really care about the setting, and that is what readers pick it up for. If you'd got a good story to tell, write that out first and then insert it into an appropriate setting. A great tool you have at your disposition, as a writer, is that you can keep numbers out of your book, keep descriptions vague and only name-drop a few key concepts to give a veneer of plausibility. Realism is great, but not even the most avid reader cares much about the percentage of fusion power your electromagnetic coils are absorbing. They just want to read that the radiators are glowing and the fusion reaction gives off nasty x-rays. Bonus points for including a second set of radiators that are not glowing and that the fusion engine needs a particle accelerator running the length of the ship. Does any of this need much of the maths going on between you and Kerr ? Another thing I have noticed is that you two started out with vague requirements on travel times, set no limits on the tech level and ran up and down the gamut of options like a xylophone. I am certain that you are fatigued right now from researching the myriad options available and might feel dissatisfied that all that work has not let to a clear solution so far. Problem is, there is no solution. It's your universe. Using NSWR or Orion, D-T or p-B11, laser-driven missiles or Casaba Howitzers... there is no 'right' answer. There's a set of options that might fit a vision better, or might have certain limitations you'd need to work around or secondary requirements which might hurt internal consistency... but would any of it be 'wrong', really? Again, I strongly suggest you return to your list of requirements and add more detail to what you want before you dive in again into all the maths and technology, ok?  View it from a different perspective, if it wasn't for matterbeam and me and some others you would have used your old fusion tech while thinking it was realistic. Does it even matter how much super high tech we assume here? Just to justify your technologies so they seem reasonable from our perspective? |
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Post by Enderminion on Sept 9, 2017 20:15:31 GMT
Orion pusher plates, keep it simple (stupid) why bother with fancy fusion thingys when a good pusher plate works just as well
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Post by Kerr on Sept 9, 2017 20:23:50 GMT
Orion pusher plates, keep it simple (stupid) why bother with fancy fusion thingys when a good pusher plate works just as well Too low Isp. Or having the equivalent of an tera-petawatt laser firing at an pusher plate while only having an max isp of only 100,000. |
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Post by Enderminion on Sept 9, 2017 22:10:12 GMT
Orion pusher plates, keep it simple (stupid) why bother with fancy fusion thingys when a good pusher plate works just as well Too low Isp. Or having the equivalent of an tera-petawatt laser firing at an pusher plate while only having an max isp of only 100,000. Two low ISP? have more bombs, yes you need a mass ratio more then 1, but it's simple as hell |
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Post by Kerr on Sept 10, 2017 5:27:37 GMT
Too low Isp. Or having the equivalent of an tera-petawatt laser firing at an pusher plate while only having an max isp of only 100,000. Two low ISP? have more bombs, yes you need a mass ratio more then 1, but it's simple as hell Wow... You don't even know how the rocket equation works? One of the most basic parts in rocket science. Example: Delta-v: 1Mm/s Mass ratio 2.77 Delta-v: 2Mm/s Mass ratio 7.7 Delta-v 3Mm/s Mass ratio 21 Delta-v: 4Mm/s Mass ratio of 60 Delta-v: 6Mm/s Mass ratio 456 Delta-v: 30Mm/s (0.1c) Mass ratio 19711924989665, if you use 10 Stages instead you have the same speed with an mass ratio of 26600 Delta-v: 30Mm/s Mass ratio 21 using an fuel with an specific impulse of one million seconds. See how an increase in Isp by ten decreases the mass ratio by 900 billion? The tyranny of the rocket equation. |
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Post by Kerr on Sept 10, 2017 7:03:46 GMT
ironclad6www.projectrho.com/public_html/rocket/enginelist.php#avtfusionThis is what I initially suggested to you with the MPDT's. Now that you have them implemented in your Adamites ships you can still use remass with your fusion fuel. 10cm wide 50g D-He³ Pellet surrounded by 5.5mm tungsten absorbs up to 85% of the pellets energy. Heating the 3.7kg to 30 gigakelvin with an resulting exhaust velocity of 2Mm/s. This allows you to have 13.5x the Thrust for the same amount of Thrust power, if you use D-He³. Proton-boron would have comparable performance.
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Post by thorneel on Sept 10, 2017 13:09:39 GMT
Note that you can assume higher-temperature superconductors with a large max power density because future materials to cut down on cooling requirements. I suspect no-one will claim it to be unrealistic as long as it's the Future and you don't give them properties too much beyond current cryogenic superconductors, not even superconductor specialists.
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Post by Kerr on Sept 10, 2017 13:20:01 GMT
Note that you can assume higher-temperature superconductors with a large max power density because future materials to cut down on cooling requirements. I suspect no-one will claim it to be unrealistic as long as it's the Future and you don't give them properties too much beyond current cryogenic superconductors, not even superconductor specialists. I already assume room-temperature superconductors the entire time, and the heat is still catastrophic. Or do you think about superconductors operating at temperatures where most metals melt? |
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Post by matterbeam on Sept 10, 2017 14:47:45 GMT
Note that you can assume higher-temperature superconductors with a large max power density because future materials to cut down on cooling requirements. I suspect no-one will claim it to be unrealistic as long as it's the Future and you don't give them properties too much beyond current cryogenic superconductors, not even superconductor specialists. Agreed. With arbitrarily powerful magnetic fields, the limits become the material strength of the structures holding the magnets against the fusion's impulse. The maximum field strength becomes asymptotic to the tensile strength of carbon nanotubes. |
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Post by Kerr on Sept 10, 2017 14:49:40 GMT
Note that you can assume higher-temperature superconductors with a large max power density because future materials to cut down on cooling requirements. I suspect no-one will claim it to be unrealistic as long as it's the Future and you don't give them properties too much beyond current cryogenic superconductors, not even superconductor specialists. Agreed. With arbitrarily powerful magnetic fields, the limits become the material strength of the structures holding the magnets against the fusion's impulse. The maximum field strength becomes asymptotic to the tensile strength of carbon nanotubes. Is there any handy equation for critical current using tensile strength? |
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Post by Enderminion on Sept 10, 2017 14:51:25 GMT
Two low ISP? have more bombs, yes you need a mass ratio more then 1, but it's simple as hell Wow... You don't even know how the rocket equation works? One of the most basic parts in rocket science. Example: Delta-v: 1Mm/s Mass ratio 2.77 Delta-v: 2Mm/s Mass ratio 7.7 Delta-v 3Mm/s Mass ratio 21 Delta-v: 4Mm/s Mass ratio of 60 Delta-v: 6Mm/s Mass ratio 456 Delta-v: 30Mm/s (0.1c) Mass ratio 19711924989665, if you use 10 Stages instead you have the same speed with an mass ratio of 26600 Delta-v: 30Mm/s Mass ratio 21 using an fuel with an specific impulse of one million seconds. See how an increase in Isp by ten decreases the mass ratio by 900 billion? The tyranny of the rocket equation. you don't hardly need 3Mm/s of Dv to travel around a star system though, 10km/s is enough to do a Holman transfer to jupiter, with 30000km/s of Dv you can get their faster yes, but how much faster? also their is a thing of too much specific impulse |
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Post by Kerr on Sept 10, 2017 15:03:59 GMT
Wow... You don't even know how the rocket equation works? One of the most basic parts in rocket science. Example: Delta-v: 1Mm/s Mass ratio 2.77 Delta-v: 2Mm/s Mass ratio 7.7 Delta-v 3Mm/s Mass ratio 21 Delta-v: 4Mm/s Mass ratio of 60 Delta-v: 6Mm/s Mass ratio 456 Delta-v: 30Mm/s (0.1c) Mass ratio 19711924989665, if you use 10 Stages instead you have the same speed with an mass ratio of 26600 Delta-v: 30Mm/s Mass ratio 21 using an fuel with an specific impulse of one million seconds. See how an increase in Isp by ten decreases the mass ratio by 900 billion? The tyranny of the rocket equation. you don't hardly need 3Mm/s of Dv to travel around a star system though, 10km/s is enough to do a Holman transfer to jupiter, with 30000km/s of Dv you can get their faster yes, but how much faster? also their is a thing of too much specific impulse Me: "But for what do you need so much Dv for? You still have to replenish your food and other vital resources every few months. Most of the time you won't cruise around at dozens to hundred kilometers per second in the system. Creating Stable orbits cost few dozens km/s at most.." ironclad6: "...I'm also dealing with planetary systems with much steeper gravity wells than any in our solar system. Providence, the main planetary sub system I'm dealing with with in my novel is actually about eighty Jupiter masses..." In the context of ironclad6 novel his ships need to do Hohmann transfers every few days, he mainly needs that much Dv so his ships can operate as long as possible with minimal support. Having to refuel every months is much worse than getting a few tons of food every month. There is no such thing as "too much specific impulse", there is only too much relative to something. And what do you think is cheaper? A few kilotons of fusiles generated from seawater and borax for a few cents per kilo or highly enriched uranium? |
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