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Post by argonbalt on Jan 18, 2017 19:39:49 GMT
Okay so for whatever reason i ended up generally using Hydrogen for all of my propellant needs. Im not really sure why, maybe i really wanted exit velocity? but that's how it is. So looking at the handy standardisation thread, i was hoping i could get some recommendations for the ideal propellant type. My standard reactor set up is about 10 Gw, so i was wondering what for such a drive would satisfy:
A resisto jet
A MPD
A NTR At the same time/same propellant type. I understand that the ideal for the three is Decane for the RJ, Mercury for the MPD and Methane for the best balance in the NTR, but i was wondering, what is a good mix for all three? or at the very least maybe i should drop the NTR and what would satisfy the first two really well? or is it altogether stupid and i should simply have speciality drives for what i need when i need it (going for ideal propellant for ideal usage).
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Post by jasonvance on Jan 18, 2017 19:50:30 GMT
Imo go with Neon MPD / Resisto jet combo (it is the cheapest propellant and greatly reduces the cost of ships as a result). MPD produces the long distance high delta-v and the resistojet produces the emergency maneuvering thrusters. It can kind of be a hassle to toggle the jets on and off though.
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Post by jasonvance on Jan 18, 2017 19:56:10 GMT
These are just ball parked and not min-maxed but it will give you an idea of what neon can do
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Post by bdcarrillo on Jan 18, 2017 19:59:23 GMT
Take a look in the standards thread, stickied here.
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Post by argonbalt on Jan 18, 2017 20:08:05 GMT
Thanks jasonvance, now i can do a better one to one with the engine parts i got.
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Post by argonbalt on Jan 18, 2017 20:34:38 GMT
okay general question here, is there any advantage to very high exhaust velocity?
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Post by ash19256 on Jan 18, 2017 20:40:22 GMT
okay general question here, is there any advantage to very high exhaust velocity? IIRC, higher exhaust velocities are generally the sign of higher specific impulses for the same level thrust, as you are getting more energy out of the same mass of propellant, meaning you need less of it to achieve the same thrust. I think. I just know that an engine that produces 4 kN of thrust with an exhaust velocity of 5.24 km/s produces a higher specific impulse than a large number of my lower exhaust velocity engines of roughly equivalent thrust when their stats are plugged into a specific impulse equation.
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Post by David367th on Jan 18, 2017 20:42:04 GMT
okay general question here, is there any advantage to very high exhaust velocity? IIRC, higher exhaust velocities are generally the sign of higher specific impulses for the same level thrust, as you are getting more energy out of the same mass of propellant, meaning you need less of it to achieve the same thrust. I think. I just know that an engine that produces 4 kN of thrust with an exhaust velocity of 5.24 km/s produces a higher specific impulse than a large number of my lower exhaust velocity engines of roughly equivalent thrust when their stats are plugged into a specific impulse equation. Specific Impulse is a function of Exhaust velocity. More velocity means longer impulse which means more delta-v.
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Post by argonbalt on Jan 18, 2017 20:46:46 GMT
Hmm see that is what i thought as well, but would you guys agree that with the amounts of juice we can pump into some of these MPD's that that is no longer a real issue?
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Post by Enderminion on Jan 18, 2017 20:50:04 GMT
yes but can you get mega-newtons of thrust with MPDs
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Post by jasonvance on Jan 18, 2017 21:02:33 GMT
yes but can you get mega-newtons of thrust with MPDs yes you can in fact you can do a lot better with MPDs than any other engine type if you get enough power behind it. Here is a modest 70 mega newton MPD that could get you to 1% the speed of light with enough fuel and here is a 290 giga-newton MPD that no one can ever power that could get you to 4-5x the speed of light (game doesn't do relativistic physics)
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Post by jasonvance on Jan 18, 2017 21:07:48 GMT
In the more reasonable power ranges of 10GW and below you can use a reistojet to cover the thrust problem
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Post by newageofpower on Jan 18, 2017 21:19:19 GMT
Hmm see that is what i thought as well, but would you guys agree that with the amounts of juice we can pump into some of these MPD's that that is no longer a real issue? Fuck no. The setup it takes to get to the energies required to achieve meganewtons of thrust from an MPD is so massive your acceleration is measured in milligees. Dozens, not hundreds of milligees.
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Post by jasonvance on Jan 18, 2017 21:35:19 GMT
Hmm see that is what i thought as well, but would you guys agree that with the amounts of juice we can pump into some of these MPD's that that is no longer a real issue? Fuck no. The setup it takes to get to the energies required to achieve meganewtons of thrust from an MPD is so massive your acceleration is measured in milligees. Dozens, not hundreds of milligees. You can get Mercury MPDs in the hundreds of mG (even at low-ish power)... But honestly ship maneuvering is mostly irrelevant you are never going to achieve more thrust than an intercepting missile or some other high acceleration design. Unless you have higher acceleration than what you are trying to dodge you will never dodge it (all it has to do is mirror your burns). So the difference between a 10mG spaceship and a 10G spaceship (which would kill its crew for prolonged thrust) is irrelevant when compared to a 11G missile. If the industry standard is 20G maneuvering ships the industry standard intercepting missiles will be 25G you can't win that battle and there is actually a hard limit on how fast you can accelerate with squishy humans in your ship.
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Post by dorkious on Jan 18, 2017 23:02:50 GMT
Fuck no. The setup it takes to get to the energies required to achieve meganewtons of thrust from an MPD is so massive your acceleration is measured in milligees. Dozens, not hundreds of milligees. You can get Mercury MPDs in the hundreds of mG (even at low-ish power)... But honestly ship maneuvering is mostly irrelevant you are never going to achieve more thrust than an intercepting missile or some other high acceleration design. Unless you have higher acceleration than what you are trying to dodge you will never dodge it (all it has to do is mirror your burns). So the difference between a 10mG spaceship and a 10G spaceship (which would kill its crew for prolonged thrust) is irrelevant when compared to a 11G missile. If the industry standard is 20G maneuvering ships the industry standard intercepting missiles will be 25G you can't win that battle and there is actually a hard limit on how fast you can accelerate with squishy humans in your ship. I'd argue that capital ship acceleration in the 1g plus range can be beneficial for counting sand blast type attacks. Dodging well designed missiles as you point out is probable a bad idea, decoys would be the way to go. But then decoys need to be a hotter target so less power less thrust etc. (Edit) Actually depending on range you can out delta V missiles. If the target can expend more deltaV within the missile closing time than the missile possesses....
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