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Post by argonbalt on Dec 19, 2016 16:26:01 GMT
Generally unless it's a laser boat the engine on a warship is crap for efficiency... it's better to run with near empty tanks on a warship with its crappy combat engines pushing as little mass as possible while a large tanker with kt of fuel runs along side with a high efficiency MPD driving it. When you get near just fill up the tank and go to war Btw I wish there was a way to spawn with droptanks empty and set max tank fill% to facilitate such manoeuvres... properly. How is this more ideal? I understand super reactor+MPD ships get insane amounts of Dv at the cost of only a few micro newtons of thrust, but why not place the MPD directly on the warship?, more to the point, how would you even move your two ships if the main attackers is optimally running on empty? With its more powerful engines would it not just out run and then run out of fuel? This all goes without dealing with the time spans involved
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Post by amimai on Dec 19, 2016 16:57:46 GMT
Because warships have to worry about crossection, form factor, acceleration, armour mass, and return to base fuel reserves... even if you put a large droptank on, there is no way to fit in a large reactor, and another eqaly large internal fuel tank to let you go back home after the fight without the end result being needlessly large and costly.
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Post by argonbalt on Dec 19, 2016 19:21:00 GMT
i guess that kinda makes sense, it still strikes me as strange though. Like imagine an cruiser running on diesel with a sail ship tanker for support. Then when it is time for battle the sail ship refuels the cruiser. I guess it would help to define that when i was working with these designs i was working towards an absolute victory situation were only after you arrive a dedicated tanker would show up and do the RTB refuel and resupply. Of course tankers have benefits, but for insertion phase (especially on a none 200 year time limit) pumping in on drop tanks and switching over sounds far more ideal.
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Post by shurugal on Dec 19, 2016 21:23:47 GMT
i guess that kinda makes sense, it still strikes me as strange though. Like imagine an cruiser running on diesel with a sail ship tanker for support. Then when it is time for battle the sail ship refuels the cruiser. I guess it would help to define that when i was working with these designs i was working towards an absolute victory situation were only after you arrive a dedicated tanker would show up and do the RTB refuel and resupply. Of course tankers have benefits, but for insertion phase (especially on a none 200 year time limit) pumping in on drop tanks and switching over sounds far more ideal. while your example is a bit of an exaggeration, that is exactly what modern navies do.
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Post by argonbalt on Dec 19, 2016 21:59:23 GMT
No no no, of course navies need tankers and supply ships, not to mention modern navies using dedicated air screen cruisers. It is mainly the matter of using MPD ships with their fuck huge reactors, eng and radiators, i mean i know it is more efficient propellant use wise to Dv, but it still strikes me as odd. Maybe i have been away a little too long i know with the huge reactors some new MPD were being made, but people are now also considering Decane, why that fuel exactly?
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Post by shurugal on Dec 19, 2016 22:11:40 GMT
what strikes you as odd about wanting to transport fuel as efficiently as possible? It does little good to have a 50kt tanker that uses 40kt getting to the fleet that needs fuel.
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Post by argonbalt on Dec 19, 2016 22:35:20 GMT
I think i am just out of date with the latest MPD designs, when i last looked at them they were not nearly as good. one thread claimed able to be anywhere in the solar system within a year. Do you know were these designs have been posted i would like to take a look at them.
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Post by amimai on Dec 19, 2016 23:08:25 GMT
My preferred hydrogen MPD outputs 47GW/kg/s thrust, scales up to 700GW/4kg/s, gets a dedicated tanker anywhere at minimum fuel on the cheap. A 10t hydrogen tank is literally all you ever need...
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Post by argonbalt on Dec 19, 2016 23:29:19 GMT
Would you mind sharing engine schematics?
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Post by Easy on Dec 20, 2016 16:51:45 GMT
Okay, drop tanks are awesome.
I highly suggest making heat resistant (not plastic) external tanks that don't detach on your underbelly.
Yes radiators get in the way, but I'm sure you can figure it out.
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Post by goduranus on Dec 20, 2016 17:21:47 GMT
I think i am just out of date with the latest MPD designs, when i last looked at them they were not nearly as good. one thread claimed able to be anywhere in the solar system within a year. Do you know were these designs have been posted i would like to take a look at them. This one View AttachmentView AttachmentHomecoming in 4 months and 18 days.
Theoretically it should be possible to do it in under 4 months. But that would require some very efficient and tight maneuvering. This took me a few tries, and even then I am still wasting a lot of deltaV. The "shuttle" has 437 km/s DeltaV and little over 5 mG of acceleration when the tanks are full. The thruster has an exhaust velocity of 200km/s and is powered by 7 modified 24.7 GW Apophy's reactors ( 173 GW total). The first version had more deltaV but slower acceleration. If you're building ships with a lot of deltaV I recommend keeping the burn time at around 1 month. I sacrificed about 50km/s deltaV, but I compensated that by pulling more Gs, which in this case means I reach max velocity twice as fast and have an easier time making the insertion burns.
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Post by amimai on Dec 20, 2016 18:07:19 GMT
i.imgur.com/L2EWxMN.png?1using MagnetoplasmadynamicThrusterModule 307 km/s 47.7 GW Hydrogen Gimballed Magnetoplasmadynamic Thruster CathodeRadius_m 0.0029 ChamberThickness_m 0.019 AnodeThickness_m 0.001 ThrusterLength_m 1.8 CathodeComposition Potassium AnodeComposition Depleted Uranium InsulatorComposition Boron Propellant Hydrogen Current_A 4.8e+005 Injector Composition Lithium PumpRadius_m 0.092 RotationalSpeed_RPM 220 Gimbal InnerRadius_m 0.14 ArmorComposition Silica Aerogel ArmorThickness_m 0.0001 ReactionWheels Composition Potassium RotationalSpeed_RPM 5300 GimbalAngle_degrees 20 cheap, efficient, fast
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Post by argonbalt on Dec 20, 2016 22:21:08 GMT
Hot damn!
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Post by David367th on Dec 20, 2016 23:10:35 GMT
Everytime I see a really high exhaust velocity I keep thinking its super fast and must be close to C but then I google it and find c is 300,000 km/s and I get sad.
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Post by newageofpower on Dec 20, 2016 23:15:48 GMT
If you check out the Logistics ship thread, I've derailed improved it with my 400 km/s freighters (with 70kt+ of dry mass) and 1000 km/s fuel tankers. MPDs improve linearly to around 80-120 GW, and then slowly curves off a little to about 470 GW. I stopped testing designs larger than that as the game lags significantly when I design a ship big enough to mount enough radiators to get rid of the waste heat. Of course, my MPDs are horridly optimized, neither great at exhaust velocity nor good with thrust; but they all have tiny form factors and can be squeezed between the nozzles of my secondary drives. Everytime I see a really high exhaust velocity I keep thinking its super fast and must be close to C but then I google it and find c is 300,000 km/s and I get sad. Someone made a ship capable of reaching 1.29% C with an Hydrogen MPD.
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