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Post by The Astronomer on May 5, 2017 13:48:20 GMT
It's actually pretty simple. The energy of a nuclear reaction is usually given in electronvolts, eV. The 1.602x10^-19 converts electron volts to joules, which is the unit of energy we're interested in for the in-game configs. This is only the energy for one reaction event though (a single atom fuses with another). Avogadro's number is the number of carbon atoms in 12 grams of carbon-12. If we multiply the energy per reaction event by Avogadro's number we get the energy per mole of reactant fused, which we can then divide by 1000 (converting from J/mol to kJ/mol) and use as the value for the enthalpy of formation of the fusion fuel. For B-11 + p I got 837492660.3 kJ/mol. I think something's wrong here. |
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Post by nerd1000 on May 5, 2017 13:53:26 GMT
yes, that should give you the energy per mole of fuel reacted. Convert J to kJ and you're good to go. Make sure to only count energy that's supplied to charged particles.Huh? How? :/ If it's an aneutronic reaction don't worry about it. But for D-T or D-D fusion (the latter is a side reaction for D-He3) we need to make sure we don't count the energy of neutrons produced in the reaction (D-T fusion produces a 14.1 MeV neutron), as those neutrons will go flying out of the engine in all directions and contribute almost nothing to thrust. If you're modelling D-He3, I don't have hard numbers for the amount of energy that ends up in neutrons. Wikipedia says 'probably several percent', so maybe nerf your reaction energy by 5% or so. |
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Post by The Astronomer on May 5, 2017 13:56:55 GMT
If it's an aneutronic reaction don't worry about it. But for D-T or D-D fusion (the latter is a side reaction for D-He3) we need to make sure we don't count the energy of neutrons produced in the reaction (D-T fusion produces a 14.1 MeV neutron), as those neutrons will go flying out of the engine in all directions and contribute almost nothing to thrust. If you're modelling D-He3, I don't have hard numbers for the amount of energy that ends up in neutrons. Wikipedia says 'probably several percent', so maybe nerf your reaction energy by 5% or so. I need you to look into the numbers. My calc said the kJ/mol for B-11 + p should be 837492660.3. Yours' 239262804. Also, I can't find autoignition temp and characteristic length. |
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Post by nerd1000 on May 5, 2017 14:00:17 GMT
It's actually pretty simple. The energy of a nuclear reaction is usually given in electronvolts, eV. The 1.602x10^-19 converts electron volts to joules, which is the unit of energy we're interested in for the in-game configs. This is only the energy for one reaction event though (a single atom fuses with another). Avogadro's number is the number of carbon atoms in 12 grams of carbon-12. If we multiply the energy per reaction event by Avogadro's number we get the energy per mole of reactant fused, which we can then divide by 1000 (converting from J/mol to kJ/mol) and use as the value for the enthalpy of formation of the fusion fuel. For B-11 + p I got 837492660.3 kJ/mol. I think something's wrong here. That's pretty close to my value of 848458800 kJ/mol as used in the p-B11 code I posted. Difference probably comes from expressing Avogadro's number to a different level of precision. And yes, that's around 4 million times more energy per mole than hydrogen-oxygen combustion. Turns out that nuclear fuel is outrageously energy dense.  Edit: You're looking at activation energy! The energy released in the reaction comes from the fuel's heat of formation, which is specified in the material not the reaction. As I mentioned in my PM earlier, the activation energy was calculated by RiftandRend by working out how much energy it would take to heat a mole of reactant to 'ignition' temperature. Same should work for D-He3. |
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Post by The Astronomer on May 5, 2017 14:01:56 GMT
For B-11 + p I got 837492660.3 kJ/mol. I think something's wrong here. That's pretty close to my value of 848458800 kJ/mol as used in the p-B11 code I posted. Difference probably comes from expressing Avogadro's number to a different level of precision. And yes, that's around 4 million times more energy per mole than hydrogen-oxygen combustion. Turns out that nuclear fuel is outrageously energy dense. Wait a min. This is your latest update on this thing: childrenofadeadearth.boards.net/post/19177/threadIs it just me, or the value shown there is wrong? You wrote '239262804' in ActivationEnergy_kJ__mol, apparently... Autoignition temp, characteristic length for D + He-3 wanted. |
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Post by nerd1000 on May 5, 2017 14:30:24 GMT
That's pretty close to my value of 848458800 kJ/mol as used in the p-B11 code I posted. Difference probably comes from expressing Avogadro's number to a different level of precision. And yes, that's around 4 million times more energy per mole than hydrogen-oxygen combustion. Turns out that nuclear fuel is outrageously energy dense. Wait a min. This is your latest update on this thing: childrenofadeadearth.boards.net/post/19177/threadIs it just me, or the value shown there is wrong? You wrote '239262804' in ActivationEnergy_kJ__mol, apparently... Autoignition temp, characteristic length for D + He-3 wanted. Activation energy is the energy needed to get the reaction started: imagine it like pushing a heavy cart up a short hill so it can roll down a much longer hill on the other side. The energy you calculate from the fusion reaction needs to be added to the heat of formation of the fuel element. The characteristic length only specifies the length of the chamber in the engine editor. It doesn't seem to affect engine performance at all beyond that, so feel free to fudge it. A good guideline might be the gasdynamic mirror spacecraft suggested on Atomic rockets ( here). Depending on your level of optimism the chamber might be between 15 and 200m long. Autoignition temperature should be 2.321x10^8 K, based on www.projectrho.com/public_html/rocket/fusionfuel.php#id--Fusion_Reactions and hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/eqpar.html#c2. Side note: I only put the p-B11 fuel mix together as a proof of concept. It's actually very unrealistic because the p-B11 reaction has many problems that should vastly reduce its performance. I feel that you D-He3 has the potential to be a much more realistic representation of what's possible with a 'far future' fusion drive.  |
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Post by The Astronomer on May 5, 2017 14:43:11 GMT
Wait a min. This is your latest update on this thing: childrenofadeadearth.boards.net/post/19177/threadIs it just me, or the value shown there is wrong? You wrote '239262804' in ActivationEnergy_kJ__mol, apparently... Autoignition temp, characteristic length for D + He-3 wanted. Activation energy is the energy needed to get the reaction started: imagine it like pushing a heavy cart up a short hill so it can roll down a much longer hill on the other side. The energy you calculate from the fusion reaction needs to be added to the heat of formation of the fuel element. The characteristic length only specifies the length of the chamber in the engine editor. It doesn't seem to affect engine performance at all beyond that, so feel free to fudge it. A good guideline might be the gasdynamic mirror spacecraft suggested on Atomic rockets ( here). Depending on your level of optimism the chamber might be between 15 and 200m long. Autoignition temperature should be 2.321x10^8 K, based on www.projectrho.com/public_html/rocket/fusionfuel.php#id--Fusion_Reactions and hyperphysics.phy-astr.gsu.edu/hbase/Kinetic/eqpar.html#c2. Side note: I only put the p-B11 fuel mix together as a proof of concept. It's actually very unrealistic because the p-B11 reaction has many problems that should vastly reduce its performance. I feel that you D-He3 has the potential to be a much more realistic representation of what's possible with a 'far future' fusion drive. I don't think fusion is going to be far off anyways... Thanks for the info! I'm running a test now. |
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Post by The Astronomer on May 5, 2017 14:49:28 GMT
ChemicalReaction Deuterium Helium-3 Fusion
Reactants Deuterium Helium-3
ReactantCounts 1 2
Products Hydrogen Helium
ProductCounts 1 2
ActivationEnergy_kJ__mol 1682347151.1
AutoignitionTemperature_K 232100000
CharacteristicLength_m 50 Deuterium + Helium-3  Boron-11 + Proton Can't get it to work somehow ._. |
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Post by The Astronomer on May 5, 2017 15:36:58 GMT
Don't know what's wrong with it, but I can't write a working combustion reaction...
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Post by nerd1000 on May 6, 2017 0:14:18 GMT
Don't know what's wrong with it, but I can't write a working combustion reaction... It looks like you used the pre-existing Deuterium and Helium 3 from the game. Your problem is that the heat released isn't specified in the reaction: it comes from the difference in enthalpy of formation between the reactants and the products. Helium and Hydrogen are both pure elements and have an enthalpy of formation of zero, so any reaction between them that also produces pure elements (like yours) will produce no heat. You'll need to make your own Deuterium or Helium fuel material and edit its heat of formation to match the value you calculated from the fusion energy. |
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Post by The Astronomer on May 6, 2017 2:39:22 GMT
Don't know what's wrong with it, but I can't write a working combustion reaction... It looks like you used the pre-existing Deuterium and Helium 3 from the game. Your problem is that the heat released isn't specified in the reaction: it comes from the difference in enthalpy of formation between the reactants and the products. Helium and Hydrogen are both pure elements and have an enthalpy of formation of zero, so any reaction between them that also produces pure elements (like yours) will produce no heat. You'll need to make your own Deuterium or Helium fuel material and edit its heat of formation to match the value you calculated from the fusion energy. How do I find them? What's this value you mentioned, anyways? ._. This looks tough. EDIT 1: Is it activation energy for both? |
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Post by The Astronomer on May 6, 2017 3:46:12 GMT
nerd1000 - Adviser Rocket Witch - Owner of the material compendium samchiu2000 - β Tester Deuterium + Helium-3 Fusion ChemicalReaction Fusion Deuterium Helium-3
Reactants Deuterium (Fusion D + He-3) Helium-3 (Fusion D + He-3)
ReactantCounts 1 1
Products Fusion Proton Helium
ProductCounts 1 1
ActivationEnergy_kJ__mol 19297066
AutoignitionTemperature_K 232100000
CharacteristicLength_m 50Note: EnthalpyOfFormation_kJ__mol is halved between both component. Material Deuterium (Fusion D + He-3)
Elements D
ElementCount 1
Density_kg__m3 162.4
EnthalpyOfFormation_kJ__mol 841173575.55
BondDissociationEnergy_kJ__mol 0
GibbsFreeEnergyOfFormation_kJ__mol 160.788
MeltingPoint_K 18.73
BoilingPoint_K 23.67
ThermalConductivity_W__m_K .13007
SpecificHeat_J__kg_K 10327.18
Viscosity_Pa_s 12.6e-6
RefractiveIndex Deuterium
Material Helium-3 (Fusion D + He-3)
Elements He-3
ElementCount 1
Density_kg__m3 125
EnthalpyOfFormation_kJ__mol 841173575.55
BondDissociationEnergy_kJ__mol 0
GibbsFreeEnergyOfFormation_kJ__mol 0
MeltingPoint_K .95
BoilingPoint_K 4.222
SpecificHeat_J__kg_K 5193.12
ThermalConductivity_W__m_K .1513
Viscosity_Pa_s .000019
Resistivity_Ohm_m 1e-8
Material Fusion Proton
Elements p
ElementCount 1
Density_kg__m3 70.85
EnthalpyOfFormation_kJ__mol 218
BondDissociationEnergy_kJ__mol 0
GibbsFreeEnergyOfFormation_kJ__mol 203.3
BulkModulus_GPa .1130
MeltingPoint_K 14.01
BoilingPoint_K 20.28
SpecificHeat_J__kg_K 20636.15
ThermalConductivity_W__m_K 1815
Viscosity_Pa_s 8.76e-6
RelativePermeability .9999999751
DielectricStrength_MV__m 1.95
RefractiveIndex Hydrogen
Element Proton
Symbol p
AtomicMass 1
AtomicNumber 1
MolarMass_g__mol 1.0073
IsANonmetal true
FirstIonizationEnergy_kJ__mol 1312.0
MicroscopicThermalNeutronCaptureCrossSection_b .294
MicroscopicThermalNeutronScatteringCrossSection_b 28.966
MicroscopicFastNeutronCaptureCrossSection_b 3.96e-5
MicroscopicFastNeutronScatteringCrossSection_b 3.99
MicroscopicResonanceIntegralCaptureCrossSection_b .149
MicroscopicResonanceIntegralScatteringCrossSection_b 240.23
SolarAbundance 4e10
Emission Hydrogen
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Post by nerd1000 on May 6, 2017 5:39:11 GMT
nerd1000 - Adviser Rocket Witch - Owner of the material compendium samchiu2000 - β Tester Deuterium + Helium-3 Fusion ChemicalReaction Deuterium Helium-3 Fusion
Reactants Rocket Deuterium Rocket Helium-3
ReactantCounts 1 2
Products Hydrogen Helium
ProductCounts 1 2
ActivationEnergy_kJ__mol 1682347151.1
AutoignitionTemperature_K 232100000
CharacteristicLength_m 50Material Rocket Deuterium
Elements D
ElementCount 2
Density_kg__m3 162.4
EnthalpyOfFormation_kJ__mol 1682347151.1
BondDissociationEnergy_kJ__mol 443.3197
GibbsFreeEnergyOfFormation_kJ__mol 0
MeltingPoint_K 18.73
BoilingPoint_K 23.67
ThermalConductivity_W__m_K .13007
SpecificHeat_J__kg_K 5200
Viscosity_Pa_s 12.6e-6
RefractiveIndex Deuterium
Dissociation
Products Monatomic Deuterium
ProductCounts 2
Material Rocket Helium-3
Elements He-3
ElementCount 1
Density_kg__m3 125
EnthalpyOfFormation_kJ__mol 1682347151.1
BondDissociationEnergy_kJ__mol 0
GibbsFreeEnergyOfFormation_kJ__mol 0
MeltingPoint_K .95
BoilingPoint_K 4.222
SpecificHeat_J__kg_K 5193.12
ThermalConductivity_W__m_K .1513
Viscosity_Pa_s .000019
Resistivity_Ohm_m 1e-8
Are the numbers in Activation energy and Enthalpy of formation the one you got from the electronvolts -> Joules per mole equation? If so you should only have that number once, on either 'rocket deuterium' or 'rocket He3'. Otherwise you'll get double the energy you should have. |
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Post by The Astronomer on May 6, 2017 5:44:41 GMT
nerd1000 - Adviser Rocket Witch - Owner of the material compendium samchiu2000 - β Tester Deuterium + Helium-3 Fusion ChemicalReaction Deuterium Helium-3 Fusion
Reactants Rocket Deuterium Rocket Helium-3
ReactantCounts 1 2
Products Hydrogen Helium
ProductCounts 1 2
ActivationEnergy_kJ__mol 1682347151.1
AutoignitionTemperature_K 232100000
CharacteristicLength_m 50Material Rocket Deuterium
Elements D
ElementCount 2
Density_kg__m3 162.4
EnthalpyOfFormation_kJ__mol 1682347151.1
BondDissociationEnergy_kJ__mol 443.3197
GibbsFreeEnergyOfFormation_kJ__mol 0
MeltingPoint_K 18.73
BoilingPoint_K 23.67
ThermalConductivity_W__m_K .13007
SpecificHeat_J__kg_K 5200
Viscosity_Pa_s 12.6e-6
RefractiveIndex Deuterium
Dissociation
Products Monatomic Deuterium
ProductCounts 2
Material Rocket Helium-3
Elements He-3
ElementCount 1
Density_kg__m3 125
EnthalpyOfFormation_kJ__mol 1682347151.1
BondDissociationEnergy_kJ__mol 0
GibbsFreeEnergyOfFormation_kJ__mol 0
MeltingPoint_K .95
BoilingPoint_K 4.222
SpecificHeat_J__kg_K 5193.12
ThermalConductivity_W__m_K .1513
Viscosity_Pa_s .000019
Resistivity_Ohm_m 1e-8
Are the numbers in Activation energy and Enthalpy of formation the one you got from the electronvolts -> Joules per mole equation? If so you should only have that number once, on either 'rocket deuterium' or 'rocket He3'. Otherwise you'll get double the energy you should have. Should I half the number of both down? |
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Post by The Astronomer on May 6, 2017 6:11:01 GMT
Boron-11 + Proton Fusion by nerd1000- Fixed the ActivationEnergy_kJ__mol. ChemicalReaction Boron-11 Proton Fusion
Reactants Hydrogen Boron-11
ReactantCounts 1 2
Products Helium
ProductCounts 6
ActivationEnergy_kJ__mol 837492660.3
AutoignitionTemperature_K 1320000000
CharacteristicLength_m 50
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