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Post by elouda on Feb 21, 2017 18:21:02 GMT
That's what I was pointing out with my bathtub analogy. We have those "energy cells", they're called capacitors. Well, we don't have them in-game, but we pretty much assume any EM weapon is using them because otherwise that peak power is ridiculous. But like the bathtub, the capacitor can't dump energy it doesn't have. So while the capacitor solves problem 1, you still have problem 2: you can't fire another shot until you've given your capacitor time to recharge. Now, that said, if you have a very large surplus of capacitors, you *could* use them to fire a rapid burst until they are depleted. But once that burst is done, you'll be back to one-shot-per-charge because now all your capacitors are empty. You won't be able to do another burst unless you spend the same amount of time charging as you would have spent firing those shots. And I assure you, no ship is carrying enough capacitors to fire their entire ammo reserve without charging. That would just be way too much mass and volume. Right, but the system I am talking about that the Navy is developing is in addition to the capacitors. At least that's what I got from the article. Did you read things differently? We know capacitors cannot store long term the way batteries or fuel cells can, but only temporarily, correct? They can only supply while they are being fed, while fuel cells can store and release even if not supplied at that time. These fuel cells would supplement the power going to the railgun allowing it to sustain a higher rate of fire than what normally would be possible. Does that make any sense to you based on your knowledge even with future battery tech? Well, there's always research into better forms of energy storage, and from that article it seemed to just be talking about improvements to capacitors and capacitor networks. With regards to the other part, it gets a little more complicated. One of the important things for railguns is that the energy delivered to the system is very high amperage, and this is something you might not be able to provide out of your 'regular' power network onboard the vessel, but only by discharging said capacitors. Thus linking batteries or fuel cells directly to the rails probably won't do much - on the other hand, you could have a supplementary set of fuel cells or even a full on reactor dedicated only to providing energy to recharge the capacitors.
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Post by elouda on Feb 21, 2017 16:59:36 GMT
Yeah, I'm working with a Water NTR atm.
Could I have a hydrogen fuel cell for power please? I don't think its feasible to build a nuclear reactor out of this stuff...
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Post by elouda on Feb 21, 2017 16:46:04 GMT
Biggest challenge here seems to trying to find anything at all that would act as a radshield...at the moment I'm using 40cm silicon slabs, but thats not really ideal.
Also, nuclear reactor design with the materials we have for thermocouples is going to be...interesting.
Would be tempted to just go with conventional rocket propulsion, except none of the fuels are ok.
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Post by elouda on Feb 21, 2017 16:42:42 GMT
Agreed with the above, that would probably be a saner way to do it, and probably easier to handle. At the end of the day projectile energy is the 'business end' of the weapon, and thus that number is interesting from a weapons standpoint.
Thus the weapon listing could become something like '32MJ 3mm Railgun (16MW)', as an example for a system firing a 32MJ projectile every 2 seconds, resulting in a power draw of 16MW (in a perfect system anyway).
If we also get separate handling for capacitors, then the options for how to design these also expand quite a bit.
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Post by elouda on Feb 21, 2017 15:29:09 GMT
The laser point is moot given that we don't have any workable lasing mediums...
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Post by elouda on Feb 21, 2017 15:08:21 GMT
I'm really not sure what there is to comment on it besides it's flat out wrong. It's based on a very limited understanding of physics (as you've just demonstrated above), and I've done my best to try and explain why, but as I said above, I suggest grabbing a highschool physics textbook (or hell, even wikipedia) and doing a little bit of reading. EDIT: Not sure why your responses above this just vanished. Guide us through the errors and revise the original formulas if needed. Just stating that there is an error doesn't advance the discussion. I do get a sense that figuring the energy per shot is a move in the right direction. I did some napkin math on a railgun I made, but probably goofed watts/wh/watt seconds as well. Sorry, I thought I made it clear enough in my responses what the problem was - this approach is dependent upon a very misconceived notion of was 'power' means in this context, and as a result is ignoring the 'rate' factor (energy per second) and as a result does not address the violations of the first law of thermodynamics present currently. Instead it tries to circumvent it by arguing based on a misunderstanding. The only formula I can see if the one at the start (Kinetic Energy / Second = 1/2 * Projectile Mass * (Muzzle Velocity)² / Time between shots), and that is correct. Energy per projectile is certainly useful, and is required for the sanity check right now anyway. The flaw as said is that the 'system' as a whole must also include rate of fire, as this determines the 'power' (in the form of kinetic energy per second) out of the system, and this should be below the input power of the system for it to be physically feasible.
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Post by elouda on Feb 21, 2017 14:48:20 GMT
Are both 233 and 235 Uranium ok? What about dioxides/depleted uranium?
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Post by elouda on Feb 21, 2017 14:21:32 GMT
Any cost/mass/crew/dv limits/requirements? Or is it a matter of 'if it can do the mission, then its fine'?
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Post by elouda on Feb 21, 2017 8:37:21 GMT
Thanks for commenting, please read my post and really think about it, and ponder it first, like really ponder it and come back and tell me if you have any thoughts on it tomorrow. I'm really not sure what there is to comment on it besides it's flat out wrong. It's based on a very limited understanding of physics (as you've just demonstrated above), and I've done my best to try and explain why, but as I said above, I suggest grabbing a highschool physics textbook (or hell, even wikipedia) and doing a little bit of reading. EDIT: Not sure why your responses above this just vanished.
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Post by elouda on Feb 21, 2017 8:34:06 GMT
By definition, power is energy per unit time. In the case of the Watt, it is Joules per Second. It has EVERYTHING to do with "how long it takes to do it". I think cracking open a physics textbook would go a long way here. The opposite, Energy is Power over time. No, energy is power times time. 10W for 10s = 100J.
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Post by elouda on Feb 21, 2017 8:28:52 GMT
Watts, watt-hours and watts per hour all get mixed up. Watts are a measurement of Power not of energy, and this is where the confusion comes in. Watts have nothing to do with time, it is a static measurement of Power (P=V*I) Take a 100 Watt light bulb. This means the light bulb does 100 Watts of "work" but has nothing to do with how long it takes to do it. Check this out, they are better writers. cleantechnica.com/2015/02/02/power-vs-energy-explanation/By definition, power is energy per unit time. In the case of the Watt, it is Joules per Second. It has EVERYTHING to do with "how long it takes to do it". Your P=V*I is also energy per unit time. I think cracking open a physics textbook would go a long way here.
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Post by elouda on Feb 21, 2017 8:11:41 GMT
Energy per second still matters, because of the first law of thermodynamics. In a perfect system, the energy out of the rail/coilgun 'system' would be equivalent to the energy it draws. This means that no matter what, the kinetic energy of the projectiles fired over a period of time, cannot exceed the electrical energy drawn in the same time (this could be directly from the reactor as now, or from capacitors/etc). If you feed in more rounds per unit time, then either the system has to draw more power, or each round has to get less total energy. EDIT: To expand on this, the 'power draw' on the rails is the result of passing a current through them. This current is not constant, but pulses when the circuit is closed by the projectile, drawing power. More projectiles = more pulses = more power required. The round is in contact with the rails for about 5% of a second. That remains the same no matter how rapidly we place rounds into the railgun, as long as we do not "double load". (If that happens, the device will go kaboom.) Each round is only in contact with the rails for that brief moment. The 0.200 MW in question acts on that one round and that one round only. So to accurately measure power in (200,000 W) to energy out (32,004.5 J) we need to look at each round, not seconds which is completely arbitrary. Why seconds? Why not milliseconds? Or microseconds? Or hours? The energy is per shot only. If we are talking about power used over time, as in "more pulses" then we are talking about watt-hours, a measurement of how much power a electronic device consumes over time, but that is a separate consideration related to power plants and reactors powering the railgun, not the railgun itself. Edit: I know how this happened now. Watts, watt-hours and watts per hour all get mixed up. Power and energy get mixed up too. It was in researching this question that I learned this myself and about how these terms are different. en.wikipedia.org/wiki/Watt#Confusion_of_watts.2C_watt-hours_and_watts_per_hourI'm not sure I follow as to how watt-hours have anything to do this this. Its a non SI unit equivalent to 3.6kJ - while its useful for some applications like household energy consumption, its just obfuscation in this case. Why seconds? Because a Watt is a Joule per second. Therefore if you have a 1MW system, it draws 1MJ of energy per second. Therefore the highest possible energy out in that same second (in a perfect system), is also 1MJ. This could be one projectile with 1MJ of energy, or 1000 with 1kJ of energy. You can do the same analysis for a minute if you want, the choice of 'per second' is just because thats what the SI unit is defined as, as hence is the most sensible to work with. Also, the 0.200 MW does not 'act' on the projectile at all. The projectile closes a circuit and creates a current, which draws energy from the energy source. This 'draw' all happens during the the time the projectile is in contact with the rails (which is a lot less than 5% of a second). If the projectile (again in a perfect system) gains 100kJ of energy during its acceleration, then 100kJ will be drawn from the source. If this is done once per second, then the weapon has a power draw (and output) of 0.1MW. If this is done twice (by feeding a second projectile in), then 200kJ is used, and the power draw (and output) is 0.2MW. If 10 projectiles are fed in during this one second, then 1000kJ or 1MJ is used, and the weapon has a power draw (and output) of 1MW.
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Post by elouda on Feb 21, 2017 7:16:37 GMT
Energy per second still matters, because of the first law of thermodynamics. In a perfect system, the energy out of the rail/coilgun 'system' would be equivalent to the energy it draws. This means that no matter what, the kinetic energy of the projectiles fired over a period of time, cannot exceed the electrical energy drawn in the same time (this could be directly from the reactor as now, or from capacitors/etc).
If you feed in more rounds per unit time, then either the system has to draw more power, or each round has to get less total energy.
EDIT: To expand on this, the 'power draw' on the rails is the result of passing a current through them. This current is not constant, but pulses when the circuit is closed by the projectile, drawing power. More projectiles = more pulses = more power required.
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Post by elouda on Feb 20, 2017 15:20:40 GMT
Only two of those should be able to fire in any arc, so it only uses 600kW at most.
EDIT: Seems like 3 can at some angles - this is easy to revise if its an issue, just remove 2 guns to bring it to 4. Theyre backup weapons anyway, and only necessary for the 3rd challenge incase the laser gets shot off (happens to 1 or 2 ships every other run it seems).
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Post by elouda on Feb 20, 2017 13:08:59 GMT
My entry; LOX/RP-1 propulsion, 5.07km/s @ 187mg (with droptanks), 4.47km/s @ 228mg (without droptanks) 6 130kW Promethium-147 RTGs 1 650kW 2800mm NUV Laser 6 300kW 3mm Railguns (4g @ 4.55km/s @ 7rps - efficiency below 100%) Single layer 3cm Carbon armour + additional internal armour Extremely redundant radiator design 34 crew for boarding and other duties 3.82kt, 39.9Mc 5 are required for the 3rd stage challenge UserDesigns.txt (Pastebin Link)
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