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Post by ironclad6 on Sept 2, 2017 15:25:42 GMT
I also feel like on the basis of this last dozen posts I might need to go back to the drawing board. I've had to make a couple of really unreasonable assumptions such as 90+% efficiency on my power plants, graphene radiators operating at 4600k and a couple of others that really tells me my fusion powered warships are pretty much impossible. I think I need to start looking at speculative materials with higher safe working temperatures (There aren't any.) and other ways of disposing of waste heat. I possibly need to accept much much lower thrust. I probably also need to really dig down and try to understand the physics involved in the magnetic confinement nozzles.
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Post by Kerr on Sept 2, 2017 15:30:56 GMT
Or just use kinetic energy. They should be more practical at 0.01c. Because their blast is directed, meaning nearly 100% go into the target instead of an omnidirectional explosion which has pn impact 50% coupling. 1kT vs. 1.37kT effective yield. And this is if you used an 1kg clump of pure zubrol compared to an 1kg Submunition which could have 100g MH and get 1750m/s Dv to track the target and to perform dodge burns. If your missile's going too fast the whole thing will blast through the enemy ship, leaving a hole, and some, if not most of the kinetic energy will still be on the missile. At these velocities you need an crater excavation equation to find out the impact effect. For my 1kg submunitipn it is a crater 10m deep and 5000m3 in volume. For structural steel. |
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Post by Kerr on Sept 2, 2017 15:41:05 GMT
I also feel like on the basis of this last dozen posts I might need to go back to the drawing board. I've had to make a couple of really unreasonable assumptions such as 90+% efficiency on my power plants, graphene radiators operating at 4600k and a couple of others that really tells me my fusion powered warships are pretty much impossible. I think I need to start looking at speculative materials with higher safe working temperatures (There aren't any.) and other ways of disposing of waste heat. I possibly need to accept much much lower thrust. I probably also need to really dig down and try to understand the physics involved in the magnetic confinement nozzles. Tantalum hafnium carbide, safe use temperature 4250K. For waste heat there are liquid droplet radiators. 90% efficency for what kind of reactor? The physics behind a magnetic nozzle aren't that hard. The math is. Your higher end efficency will be 85%. |
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Post by ironclad6 on Sept 2, 2017 15:59:07 GMT
I also feel like on the basis of this last dozen posts I might need to go back to the drawing board. I've had to make a couple of really unreasonable assumptions such as 90+% efficiency on my power plants, graphene radiators operating at 4600k and a couple of others that really tells me my fusion powered warships are pretty much impossible. I think I need to start looking at speculative materials with higher safe working temperatures (There aren't any.) and other ways of disposing of waste heat. I possibly need to accept much much lower thrust. I probably also need to really dig down and try to understand the physics involved in the magnetic confinement nozzles. Tantalum hafnium carbide, safe use temperature 4250K. For waste heat there are liquid droplet radiators. 90% efficency for what kind of reactor? The physics behind a magnetic nozzle aren't that hard. The math is. Your higher end efficency will be 85%. 90% efficiency for a Stellarator. The most optimistic credible source I've found says I should be looking at about 80% efficiency. |
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Post by Kerr on Sept 2, 2017 16:08:52 GMT
Tantalum hafnium carbide, safe use temperature 4250K. For waste heat there are liquid droplet radiators. 90% efficency for what kind of reactor? The physics behind a magnetic nozzle aren't that hard. The math is. Your higher end efficency will be 85%. 90% efficiency for a Stellarator. The most optimistic credible source I've found says I should be looking at about 80% efficiency. Well, there is the 400 years factor. And I don't see why this couldn't reach 90%. Quenchguns can achieve near 100% electric-magnetic-kinetic efficiency, or electric motors. Also try an liquid droplet radiator web.archive.org/web/20160320231951/http://www.5596.org/cgi-bin/dropletradiator.php |
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Post by Kerr on Sept 2, 2017 16:12:45 GMT
ironclad6Sorry I forgot, Carnot efficiency of an MHD is 65%.
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Post by ironclad6 on Sept 2, 2017 16:17:49 GMT
ironclad6 Sorry I forgot, Carnot efficiency of an MHD is 65%. This effects my calculations how? |
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Post by Kerr on Sept 2, 2017 16:20:20 GMT
ironclad6 Sorry I forgot, Carnot efficiency of an MHD is 65%. This effects my calculations how? Carnot efficiency is the maximum efficiency an heat engine can produce |
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Post by ironclad6 on Sept 2, 2017 16:30:12 GMT
This effects my calculations how? Carnot efficiency is the maximum efficiency an heat engine can produce So I can't have a stellarator with efficiency higher than 65%? |
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Post by Kerr on Sept 2, 2017 16:38:11 GMT
Carnot efficiency is the maximum efficiency an heat engine can produce So I can't have a stellarator with efficiency higher than 65%? I don't know. An Direct conversion device was tested in a lab, it converted 85% of the kinetic energy of charged particles into electric energy. Maybe 65% is just the limit of MHD that works on heat? |
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Post by ironclad6 on Sept 2, 2017 16:40:23 GMT
So I can't have a stellarator with efficiency higher than 65%? I don't know. An Direct conversion device was tested in a lab, it converted 85% of the kinetic energy of charged particles into electric energy. Maybe 65% is just the limit of MHD that works on heat? It would have to be something like that since Wendelstein 7-X apparently reports 80% bottom line efficiency. So, I'm reducing total thrust power to something like 1/3rd of my last baseline. I'm assuming 85% efficiency and running my fusion reactors at 4000k. My radiators are being tripled in size and constructed of graphene. CDE gives a max safe working temperature of Graphene at about 4600k. Does that seem kind weirdly high to anyone else? That seems to make the maths like back up but adds ~20ktons to each design. |
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Post by Kerr on Sept 2, 2017 16:54:24 GMT
I don't know. An Direct conversion device was tested in a lab, it converted 85% of the kinetic energy of charged particles into electric energy. Maybe 65% is just the limit of MHD that works on heat? It would have to be something like that since Wendelstein 7-X apparently reports 80% bottom line efficiency. So, I'm reducing total thrust power to something like 1/3rd of my last baseline. I'm assuming 85% efficiency and running my fusion reactors at 4000k. My radiators are being tripled in size and constructed of graphene. CDE gives a max safe working temperature of Graphene at about 4600k. Does that seem kind weirdly high to anyone else? That seems to make the maths like back up but adds ~20ktons to each design. whats the power of your reactor? |
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Post by ironclad6 on Sept 2, 2017 17:10:32 GMT
It would have to be something like that since Wendelstein 7-X apparently reports 80% bottom line efficiency. So, I'm reducing total thrust power to something like 1/3rd of my last baseline. I'm assuming 85% efficiency and running my fusion reactors at 4000k. My radiators are being tripled in size and constructed of graphene. CDE gives a max safe working temperature of Graphene at about 4600k. Does that seem kind weirdly high to anyone else? That seems to make the maths like back up but adds ~20ktons to each design. whats the power of your reactor? 275 terawatts. |
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Post by Kerr on Sept 2, 2017 17:13:44 GMT
whats the power of your reactor? 275 terawatts. what the? What do you need so much electricity for? |
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Post by ironclad6 on Sept 2, 2017 17:17:20 GMT
what the? What do you need so much electricity for? I don't. However, a fusion rocket is going to impart some of it's heat to the the ship no matter what you do with your magnetic nozzles. |
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