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Post by someusername6 on Dec 25, 2016 13:42:13 GMT
I'm interested in discussing / putting together designs for colony ships -- in particular seeing how far down we can drive the cost per person. I suspect that MPDs imply economy of scale, and that the larger you can make a ship, the cheaper it comes out per person. I also imagine they would require a sizeable delta v, but how much -- 200 km/s? 300 km/s? More? Here's a carrier for 260k people, coming a bit under 16k credits per person, inspired by a previous design on the "go big or go home" thread (and updated with the newest apophys reactors):  Code for all components under the spoiler: MagnetoplasmadynamicThrusterModule 453 km/s 1.00 TW Neon Gimballed Magnetoplasmadynamic Thruster
UsesCustomName false
CathodeRadius_m 0.0029
ChamberThickness_m 0.452
AnodeThickness_m 0.0023
ThrusterLength_m 0.06
CathodeComposition Vanadium Chromium Steel
AnodeComposition Vanadium Chromium Steel
InsulatorComposition Polyethylene
Propellant Neon
Current_A 8.1e+005
Injector
Composition Lithium
PumpRadius_m 0.05
RotationalSpeed_RPM 790
Gimbal
InnerRadius_m 0.35
ArmorComposition Silica Aerogel
ArmorThickness_m 0.04
MomentumWheels
Composition Polyethylene
RotationalSpeed_RPM 14000
GimbalAngle_degrees 90
ThermoelectricFissionReactorModule 25.1 GW Thermoelectric Fission Reactor
UsesCustomName false
ReactorCoreDimensions_m 0.3 0.54
NuclearReactor
Coolant Sodium
Moderator Boron Nitride
ModeratorMass_kg 13
Fuel U-233 Dioxide
FuelMass_kg 228
FuelEnrichment_Percent 0.97
ControlRodComposition Boron Nitride
ControlRodMass_kg 262
NeutronReflector Boron Nitride
ReflectorThickness_m 0.575
AverageNeutronFlux__m2_s 2.2e+020
InnerTurbopump
Composition Diamond
PumpRadius_m 2.5
RotationalSpeed_RPM 470
ThermocoupleInnerDimensions_m 23 30
Thermocouple
PTypeComposition Osmium
NTypeComposition Tungsten
Length_m 0.001
ThermocoupleExitTemperature_K 2400
OuterCoolant Sodium
OuterTurbopump
Composition Titanium
PumpRadius_m 1.4
RotationalSpeed_RPM 510
CrewModule 1000 Crew Module
UsesCustomName false
CrewCapacity 1000
Decks 50
StructureMaterial Magnesium
ShellThickness_m 0.0138
PropellantTankModule 10.0 kt Neon Tank
UsesCustomName false
Propellant Neon
StructureComposition Boron
ReactionMass_kg 1e+007
HeightToRadiusRatio 1
AdditionalArmorThickness_m 0
RadiatorModule 1000x50 Boron Nitride Radiator
UsesCustomName false
Composition Boron Nitride
PanelWidth_m 50
Height_m 50
Thickness_m 0.001
ArmorThickness_m 0.001
Panels 20
SurfaceFinish Diamond
RadiatorModule 1000x50 Lithium Radiator
UsesCustomName false
Composition Lithium
PanelWidth_m 50
Height_m 50
Thickness_m 0.001
ArmorThickness_m 0.001
Panels 20
SurfaceFinish Diamond
CraftBlueprint 260K Carrier
Modules
453 km/s 1.00 TW Neon Gimballed Magnetoplasmadynamic Thruster 20 0.0039 null 0
25.1 GW Thermoelectric Fission Reactor 10 10.275 null 0
1000 Crew Module 20 423.82 null 0
1000 Crew Module 20 424.82 null 0
1000 Crew Module 20 425.82 null 0
1000 Crew Module 20 426.82 null 0
10.0 kt Neon Tank 12 164.98 null 0
10.0 kt Neon Tank 11 433.07 null 0
25.1 GW Thermoelectric Fission Reactor 10 433.32 null 0
1000 Crew Module 20 427.82 null 0
1000 Crew Module 20 428.82 null 0
1000 Crew Module 20 429.82 null 0
1000 Crew Module 20 430.82 null 0
1000 Crew Module 20 431.82 null 0
1000 Crew Module 20 432.82 null 0
1000x50 Lithium Radiator 2 824.09 1000 Crew Module 0
453 km/s 1.00 TW Neon Gimballed Magnetoplasmadynamic Thruster 20 1751.6 null 0
25.1 GW Thermoelectric Fission Reactor 10 11.275 null 0
25.1 GW Thermoelectric Fission Reactor 10 434.32 null 0
10.0 kt Neon Tank 11 165.98 null 0
10.0 kt Neon Tank 12 433.19 null 0
1000x50 Boron Nitride Radiator 4 166.01 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 223.5 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 280.98 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 338.47 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 395.96 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 453.44 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1581.9 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1528.7 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1474.9 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1420.1 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1366.7 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1314.6 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 1258.8 25.1 GW Thermoelectric Fission Reactor 0
1000x50 Boron Nitride Radiator 4 510.93 25.1 GW Thermoelectric Fission Reactor 0
1000 Crew Module 20 424.82 null 0
1000 Crew Module 20 425.82 null 0
1000 Crew Module 20 426.82 null 0
1000x50 Lithium Radiator 2 897.07 1000 Crew Module 0
Armor
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Post by goduranus on Dec 25, 2016 15:21:43 GMT
Beyond the solar system or a moon or asteroid?
I doubt so many people would want to go to a new colony all at once though.
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Post by someusername6 on Dec 25, 2016 16:44:35 GMT
Not sure; I'm woefully under informed about the necessary requirements for each scenario (and created the thread to get consensus on what is reasonable).
I suspect more people would be willing to take a travel somewhere to a colony and back if the costs could be kept down (and the trip short). But then maybe that's not a colony ship.
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Post by David367th on Dec 25, 2016 18:06:56 GMT
Not sure; I'm woefully under informed about the necessary requirements for each scenario (and created the thread to get consensus on what is reasonable). I suspect more people would be willing to take a travel somewhere to a colony and back if the costs could be kept down (and the trip short). But then maybe that's not a colony ship. I think in sci fi terms, a colony ship is a ship that transports an extremely large amount of people to a distance solar system. Then goes to land itself on the surface and converts to a working surface station. |
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Post by newageofpower on Dec 25, 2016 18:20:33 GMT
Nobody has gotten a design far above 1%C. So the nearest system would still take over five centuries of travel, and that's assuming with a laser sail arrangement boosting the ship outwards for years. |
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Post by David367th on Dec 25, 2016 18:59:35 GMT
Nobody has gotten a design far above 1%C. So the nearest system would still take over five centuries of travel, and that's assuming with a laser sail arrangement boosting the ship outwards for years. That's why I was talking about sci fi, like Aurora, Ogame, and what other sci fi strategies are. Hit that black box wormhole-antimatter-FTL-whatever-drive and scoot yourself over to a planet and raise a family. In CDE I think every celestial body has a population on it except for Mercury, Venus, and Earth [citation needed] so the use of massive population colony ships isn't really needed. I'm thinking things like luxury liners carrying a few hundred or thousand is more reasonable. Maybe during the rush of population during the cataclysm had larger transports? |
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Post by someusername6 on Dec 25, 2016 19:06:25 GMT
With a sufficiently large carrying capacity + facilities, you might as well just *live* on such a ship rather than travel somewhere, just parking it somewhere convenient. But that's still not a colony ship, then it is more like a mobile station.
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Post by Pttg on Dec 25, 2016 20:00:55 GMT
I would suggest dividing the given crew size by 100 to represent the algal food systems. If you have 5,000 of reactor endurance, I think you can call the ship good.
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Post by amimai on Dec 25, 2016 23:37:33 GMT
With a sufficiently large carrying capacity + facilities, you might as well just *live* on such a ship rather than travel somewhere, just parking it somewhere convenient. But that's still not a colony ship, then it is more like a mobile station. Ahh the space city, O'Neil cylinders FTW! |
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Post by argonbalt on Dec 25, 2016 23:59:15 GMT
I hope people here are remembering that these things are not "really" great colony ships because they are running on six month Nuclear engines, so unless you are also delineating an appropriate amount of space for nuclear fuel for the journey these things will actually just run out of juice.
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Post by apophys on Dec 26, 2016 0:07:59 GMT
One issue is that reactor fuel lasts only 6 months (in these particular reactors). You'll need spare fuel rods as cargo. With a burn time of 1Y 6M, you need 2 full sets of spare fuel rods in order to hit the designed 200 km/s dV. You will also require some spare rods for powering crew modules while cruising along, and for colonization efforts, however long they need to be (but that isn't anywhere near 1TW of power, so it's hard to estimate fuel rod spares required).
Bare minimum 28 tons here (3 fuel rod exchanges), which is a drop in the bucket (one whole reactor is 247 t, and mass-wise the reactors are not a large percentage).
Extra cargo will probably be required for sustaining humans more than 6 months. Aquaponics can do that indefinitely, but such a system is heavy, and it requires power for pumping and plant growth.
This reduces the human cargo capacity somewhat, but it should be doable. Wikipedia says that solar escape velocity is ~42 km/s from Earth's distance.
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Post by amimai on Dec 26, 2016 1:05:47 GMT
The main problem is not really dV to escape solar system... it's the acceleration and deceleration phases needed to get anywhere in reasonable time. Even the most reliable systems have a lifespan, and that lifespan means that almost every peice of electrical equipment on any colony ship will fail at least once in a 100year trip.
You need to reach speeds of 1000's of km/s (%c)and have the fuel to slow back down at the other end if you want to reach another star alive.
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Post by someusername6 on Dec 26, 2016 1:12:16 GMT
If *you* want to reach the other star alive, sure.
If you want the ship to reach the other star with people alive, I think generation ships might do fine with lower delta v.
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Post by amimai on Dec 26, 2016 1:35:18 GMT
When I say "you" it's a more general "you"...
Electronics do not last. It's a pretty harsh rule of entropy. Too much power putting constant stress on the materials means they will fail eventually, even the best designed electronic system will short, burn, or fail eventually.
And when your electronics die, you die, no mater if that is you or your descendent. That's why a colony ship needs to go real fast.
Think of it this way:
20%c 60year trip, you will probably loose 1/10 ships due to catastrophic technical failure.
10%c 130year trip, you will loose 3/10
5%c 260years, 6/10
2.5%c 500years, 9/10, basically no chance
Something will go wrong somewhere at some time.
The longer your trip is, the more time there is for something to go wrong.
Even if you massively overengeneer those ships, there is a good chance that in 100years+ something somewhere will have a critical failure that will kill you and everyone else on the ship.
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Post by apophys on Dec 26, 2016 2:15:02 GMT
A ship designed to go for centuries should probably have the recycling and manufacturing capability to replace broken things, along with a small stockpile of raw material. By the time it arrives, most of its systems may be rebuilt at least once, with better technology even.  |
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