08-09-2020, 01:42 PM | #21 |
Join Date: Feb 2016
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Re: [Spaceships] Can't find the right propulsion system
I would honestly go with a higher delta-v system. A nuclear thermal rocket provides 0.5g and 0.45 mps per fuel tanks at TL9+. It could even be used for shuttle taxis from the surface to orbit and back.
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08-09-2020, 04:04 PM | #22 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] Can't find the right propulsion system
In general the more delta-V per tank, the more destructive the exhaust. Depending on the details of how it's to be used, it might be better to not use a reaction drive at all (use something like tethers, or something that interacts with EM fields created by a larger vehicle).
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08-09-2020, 05:27 PM | #23 |
Join Date: Feb 2016
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Re: [Spaceships] Can't find the right propulsion system
Well, destructive potential is a related to thrust and delta-v. Doubling thrust usually means doubling mass flow or doubling exhaust velocity. Increasing mass flow will decrease delta-v proportionally to the increase in thrust while increasing exhaust velocity will increase delta-v proportionally to the increase in thrust. Energy is proportional to the square of exhaust increase.
For example, compare the TL9 HEDM rocket (2g/0.5 mps) to the TL9 fission thermal rocket (0.5g/0.45 mps). The former possesses ~2x the exhaust velocity, burns twice as much reaction mass per second, so it is putting out ~8x the energy of latter. While a TL9+ HEDM rocket has exhaust with a temperature of over 26,000 K, the fission rocket is only running at around 6,500 K. While dangerous to unprotected systems, a TL9+ fission thermal rocket is much safer than the TL9 HEDM rocket, dealing ~1/3 as much damage to anything caught in its exhaust flow. |
08-09-2020, 07:04 PM | #24 |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] Can't find the right propulsion system
No it doesn't. The TL9 HEDM rocket has 11% higher exhaust velocity and 4x greater thrust, and thus is putting out 4.44x as much energy, but since you only have to burn it for 1/4 as long the net hazard is 11% higher. It's also running at about a 23% higher temperature (temperature varies with the square of exhaust velocity and not correlated with thrust). In any case, HEDM is also a bad choice, most thrusters intended for purposes like this are things like cold gas thrusters with exhaust velocities up to maybe 1 km/sec and thus delta-V per tank of .03mps or so.
Last edited by Anthony; 08-09-2020 at 07:07 PM. |
08-09-2020, 09:13 PM | #25 |
Join Date: Aug 2004
Location: Wellington, NZ
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Re: [Spaceships] Can't find the right propulsion system
Of the rockets available in Spaceships, the ones that seem to produce decent thrust without too much burning doom or issues with casual anti-matter ownership seem to me to be the basic chemical rocket and a nuclear thermal rocket using water as reaction mass (or hydrogen if delta-vee is more important than thrust). One means having highly volatile fuel and oxidant sitting round, the other having fissile materials readily available to all and sundry.
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Rupert Boleyn "A pessimist is an optimist with a sense of history." |
08-09-2020, 09:29 PM | #26 | |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] Can't find the right propulsion system
Quote:
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08-09-2020, 09:53 PM | #27 | |
Join Date: Aug 2004
Location: Wellington, NZ
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Re: [Spaceships] Can't find the right propulsion system
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A smaller-system (1/3 size) NTR with a single 1/3rd size fuel tank would give 0.167G and 0.15 mps DV using hydrogen or 0.5G and 0.05 mps DV with water. I think you could probably make a pretty simple, reliable, and failsafe NTR unit at TL10, especially if getting optimal thrust/weight and specific impulse out of it wasn't the priority.
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Rupert Boleyn "A pessimist is an optimist with a sense of history." |
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08-09-2020, 11:12 PM | #28 | |
Join Date: Feb 2005
Location: Berkeley, CA
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Re: [Spaceships] Can't find the right propulsion system
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If you want something that isn't ridiculously dangerous, accept low performance; something like 0.05g at 0.09mps/tank is within the reach of storable liquid rockets. |
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08-09-2020, 11:51 PM | #29 |
Join Date: Dec 2013
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Re: [Spaceships] Can't find the right propulsion system
Hmm... suggestion: Spaceships... 9?: Work Pods and Smallcraft?
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08-10-2020, 08:25 AM | #30 |
Join Date: Jan 2014
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Re: [Spaceships] Can't find the right propulsion system
Hm... Low thrust rockets:
Remote Heated Hydrogen: Hydrogen heated by laser/solar power to 5800 K. 0.3 mps per tank/0.01g Microwave Water Rocket: Water heated using microwaves to 3100 K. High Power System. 0.3 mps per tank/0.06g |
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rockets, spaceships |
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