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Post by newageofpower on Dec 11, 2016 6:01:24 GMT
Holy fuck that's inefficient.
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Post by amimai on Dec 11, 2016 7:24:49 GMT
I decided to make a long range MPD driven drone, I have made a monster (that's a 100kW, 4.5km/s railgun on the nose) the rail gun works like a reverse thruster, so once they are in battle they shoot and scoot all over the place  using this: the smallest one! 100kw methane drone MPD (52% efficiency, 76mg flow rate, 10x more efficient then NTR) perfectly designed for driving 20kg drones around the solar system
MagnetoplasmadynamicThrusterModule 36.9 km/s 100 kW Methane Gimballed Magnetoplasmadynamic Thruster
CathodeRadius_m 0.001
ChamberThickness_m 0.088
AnodeThickness_m 0.001
ThrusterLength_m 0.01
CathodeComposition Potassium
AnodeComposition Depleted Uranium
InsulatorComposition Boron
Propellant Methane
Current_A 2500
Injector
Composition Aluminum
PumpRadius_m 0.012
RotationalSpeed_RPM 1.3
Gimbal
InnerRadius_m 0.018
ArmorComposition Silica Aerogel
ArmorThickness_m 0.0001
ReactionWheels
Composition Potassium
RotationalSpeed_RPM 2200
GimbalAngle_degrees 10
mass/radius balanced vs efficiency (you can make a 4.8m wide MPD that drives 100kW with just 34mg flow rate(twice efficiency), but that wont fit on drones) |
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Post by The Astronomer on Dec 11, 2016 8:06:49 GMT
I decided to make a long range MPD driven drone, I have made a monster (that's a 100kW, 4.5km/s railgun on the nose) the rail gun works like a reverse thruster, so once they are in battle they shoot and scoot all over the place using this: the smallest one! 100kw methane drone MPD (52% efficiency, 76mg flow rate, 10x more efficient then NTR) perfectly designed for driving 20kg drones around the solar system
MagnetoplasmadynamicThrusterModule 36.9 km/s 100 kW Methane Gimballed Magnetoplasmadynamic Thruster
CathodeRadius_m 0.001
ChamberThickness_m 0.088
AnodeThickness_m 0.001
ThrusterLength_m 0.01
CathodeComposition Potassium
AnodeComposition Depleted Uranium
InsulatorComposition Boron
Propellant Methane
Current_A 2500
Injector
Composition Aluminum
PumpRadius_m 0.012
RotationalSpeed_RPM 1.3
Gimbal
InnerRadius_m 0.018
ArmorComposition Silica Aerogel
ArmorThickness_m 0.0001
ReactionWheels
Composition Potassium
RotationalSpeed_RPM 2200
GimbalAngle_degrees 10
mass/radius balanced vs efficiency (you can make a 4.8m wide MPD that drives 100kW with just 34mg flow rate(twice efficiency), but that wont fit on drones) How heavy are the projectiles? |
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Post by amimai on Dec 11, 2016 8:11:06 GMT
1g, 15ms (yea its broke, but its hilarious to watch)
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Post by The Astronomer on Dec 11, 2016 8:14:43 GMT
Time to use calculators! But what are the fire rates? (Edit the upper comment not to hijack the topic too much.) |
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Post by dragonkid11 on Dec 11, 2016 8:35:38 GMT
I decided to make a long range MPD driven drone, I have made a monster (that's a 100kW, 4.5km/s railgun on the nose) the rail gun works like a reverse thruster, so once they are in battle they shoot and scoot all over the place using this: the smallest one! 100kw methane drone MPD (52% efficiency, 76mg flow rate, 10x more efficient then NTR) perfectly designed for driving 20kg drones around the solar system
MagnetoplasmadynamicThrusterModule 36.9 km/s 100 kW Methane Gimballed Magnetoplasmadynamic Thruster
CathodeRadius_m 0.001
ChamberThickness_m 0.088
AnodeThickness_m 0.001
ThrusterLength_m 0.01
CathodeComposition Potassium
AnodeComposition Depleted Uranium
InsulatorComposition Boron
Propellant Methane
Current_A 2500
Injector
Composition Aluminum
PumpRadius_m 0.012
RotationalSpeed_RPM 1.3
Gimbal
InnerRadius_m 0.018
ArmorComposition Silica Aerogel
ArmorThickness_m 0.0001
ReactionWheels
Composition Potassium
RotationalSpeed_RPM 2200
GimbalAngle_degrees 10
mass/radius balanced vs efficiency (you can make a 4.8m wide MPD that drives 100kW with just 34mg flow rate(twice efficiency), but that wont fit on drones) Wow, that's neat. I made my own version of railgun drone before but I'm only carried them on another drone because I never figured out how to make tiny MPD drive for it. ... Now that I think about it, I SHOULD try to put MPD drive onto the carrier drone. But won't the drone just goes all over the place since the railgun recoil isn't countered by sufficient amount of counter thrust? |
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Post by amimai on Dec 11, 2016 8:51:51 GMT
MPD on something that small surprisingly give really good turn rates, and once you get to the target acceleration isn't really an issue. Also that drone has 5kg fuel, with 10kg you get double the dV
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Post by dragonkid11 on Dec 11, 2016 9:06:24 GMT
MPD on something that small surprisingly give really good turn rates, and once you get to the target acceleration isn't really an issue. Also that drone has 5kg fuel, with 10kg you get double the dV Huh, so nearly the entire mass of the drone is guns and armor? Neat. Also...some insanity I made for my collection of super micro drone.  It's a 14 kg drone that has 7 conventional cannon, firing 2.5 gram projectile at 10 rounds per second. Because why the hell not? I can most likely improve the design by using a cannon with faster fire rate but this look so much more menacing. |
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Post by jasonvance on Dec 11, 2016 17:01:41 GMT
Holy fuck that's inefficient. Yeah, the highest exhaust velocity you can get off non-MPD Mercury thrusters is around 1.1km/s, produces a lot of thrust though so it could complement an efficient MPD for emergency thrust maneuvering. I personally don't like micromanaging turning modules on and off though. |
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Post by amimai on Dec 11, 2016 18:56:09 GMT
you don't really go mercury MPD for its thrust. Mercury MPD ships are built for being compact and heavily armoured... just stick a couple methane manouvering jets on it and use the ship like an armoured turret.
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Post by newageofpower on Dec 11, 2016 19:48:16 GMT
you don't really go mercury MPD for its thrust. Mercury MPD ships are built for being compact and heavily armoured... just stick a couple methane manouvering jets on it and use the ship like an armoured turret. Listen. I didn't ask for a multipropellant solution. Can you stop butting in randomly when I clearly asked for something completely different in my request? |
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Post by amimai on Dec 11, 2016 20:26:31 GMT
You asked for something?
Oh, indeed you have... the answer is "not as far as I am aware"
You simply can't get mercury hot enough for it to work in thrusters.
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Post by jasonvance on Dec 11, 2016 20:52:59 GMT
You asked for something? Oh, indeed you have... the answer is "not as far as I am aware" You simply can't get mercury hot enough for it to work in thrusters. Temperature has nothing to do with it, and if you look at the design the mercury is 3,800K. The problem is it is too dense to get moving at any efficient speeds. The thing that makes it great for size is what makes it terrible for efficiency. Even MPDs exhibit the same properties but they have such ludicrous exhaust velocities anyways that the trade off for extra thrust makes it worth while). |
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Post by thorneel on Dec 11, 2016 21:33:30 GMT
You asked for something? Oh, indeed you have... the answer is "not as far as I am aware" You simply can't get mercury hot enough for it to work in thrusters. Temperature has nothing to do with it, and if you look at the design the mercury is 3,800K. The problem is it is too dense to get moving at any efficient speeds. The thing that makes it great for size is what makes it terrible for efficiency. Even MPDs exhibit the same properties but they have such ludicrous exhaust velocities anyways that the trade off for extra thrust makes it worth while). I think what amimai meant is that (because of the Rocket Power Equation and the mass of mercury atoms) you need such ridiculously high temperatures to get good efficiency from mercury that it is way outside available technologies. I wonder if we could reach higher temperatures by using an electric arc through the propellant instead of simply heating it up with coils. |
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Post by jasonvance on Dec 11, 2016 21:55:59 GMT
Temperature has nothing to do with it, and if you look at the design the mercury is 3,800K. The problem is it is too dense to get moving at any efficient speeds. The thing that makes it great for size is what makes it terrible for efficiency. Even MPDs exhibit the same properties but they have such ludicrous exhaust velocities anyways that the trade off for extra thrust makes it worth while). I think what amimai meant is that (because of the Rocket Power Equation and the mass of mercury atoms) you need such ridiculously high temperatures to get good efficiency from mercury that it is way outside available technologies. I wonder if we could reach higher temperatures by using an electric arc through the propellant instead of simply heating it up with coils. Possibly, but if we created an apparatus that could contain, say 8,000K, and the exhaust velocity of mercury is now ~1.5km/s, using a lower density fuel, like hydrogen methane or decane plopped into the same 8,000K apparatus would simply yield proportionally more exhaust velocity (~20km/s, 14km/s, 12km/s) at the same rate it currently does comparatively. MPDs basically accomplish what you are suggesting, and they have the same trend, but mercury is more viable there because of the thrust amount they offer (personally I prefer neon in MPDs because of the cost of the propellant). |
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