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Post by captinjoehenry on Jan 29, 2018 17:21:00 GMT
Honestly from my testing if you have accurate enough missiles such as using RCS and you give them half way decent armor even a smallish wave of them can take out a laser star. Yes all of the missiles get killed by the laser star but they get killed far too late so the dead missiles just plow into the laser star anyways. The warheads don't go off of course but even an inert missile traveling at high velocity is more than enough to knock out almost any laser star almost wherever they hit and the laser stars just can't get out of the way in the very few seconds they have between knocking out the missiles drive system and them hitting the laser star. So be it if you use non RCS missiles this wont work as you really need RCS equip missiles in order to pull this off.
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Post by AdmiralObvious on Jan 29, 2018 17:56:26 GMT
This is why I presume the game simplifies the fact that you can be running a multi terawatt reaction wheel, without actually needing to power it from a primary "general purpose" reactor. It'd be interesting to see a NTR being used as another source of power though. P.S. I don't know where the quote went, nor why.
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Post by koganusan on Jan 29, 2018 21:48:07 GMT
Honestly from my testing if you have accurate enough missiles such as using RCS and you give them half way decent armor even a smallish wave of them can take out a laser star. Yes all of the missiles get killed by the laser star but they get killed far too late so the dead missiles just plow into the laser star anyways. The warheads don't go off of course but even an inert missile traveling at high velocity is more than enough to knock out almost any laser star almost wherever they hit and the laser stars just can't get out of the way in the very few seconds they have between knocking out the missiles drive system and them hitting the laser star. So be it if you use non RCS missiles this wont work as you really need RCS equip missiles in order to pull this off. If only missile guidance was a topic mere mortals could reliably figure out, that would open many possibilities.
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Post by matterbeam on Feb 2, 2018 16:14:00 GMT
jtyotjotjipaefvjThese are the efficiency curves of the different semiconductor materials in photovoltaic cells: GaInP has an efficiency greater than 70% between 400nm and 600nm. According to the emission curve of a blackbody at 5300K, this corresponds to roughly half of the total output. All 'wasted' output comes from wavelengths lower than 600nm, which are easy to reflect. Achieving 5300K will require a liquid state or even gaseous nuclear reactor. If you use one of the semiconductors made for lower wavelengths, such as GaAs or Ge, you can get away with much lower temperatures and good efficiency. This concept is known as nuclear photovoltaics.
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Post by jtyotjotjipaefvj on Feb 2, 2018 16:47:31 GMT
jtyotjotjipaefvj These are the efficiency curves of the different semiconductor materials in photovoltaic cells: GaInP has an efficiency greater than 70% between 400nm and 600nm. According to the emission curve of a blackbody at 5300K, this corresponds to roughly half of the total output. All 'wasted' output comes from wavelengths lower than 600nm, which are easy to reflect. Achieving 5300K will require a liquid state or even gaseous nuclear reactor. If you use one of the semiconductors made for lower wavelengths, such as GaAs or Ge, you can get away with much lower temperatures and good efficiency. This concept is known as nuclear photovoltaics. I was pointing out the fact that for a 1325 K output reactor, there's not much you can do with photovoltaics. Maybe you could get a decent efficiency with heat pumps, but I doubt that too. Even when using Ge, only 8.4 % of the emitted power lands in the efficient wavelength area (900 nm to 1600 nm). This means you'd need to radiate 1 GW of heat @ 1325 K, with a radiator efficiency of 8%, realistically even less due to imperfect reflection. The 2m cube reactor would be nice to have in atmosphere, but for space use its temperature is fairly low and it would not get a high energy density nor a high efficiency percentage. For reference, here's the power spectrum of a 1325 K blackbody for the Ge wavelength area:
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Post by matterbeam on Feb 2, 2018 22:18:26 GMT
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Post by jtyotjotjipaefvj on Feb 2, 2018 22:20:01 GMT
that was quite literally my entire point?
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Post by Rocket Witch on Feb 3, 2018 8:06:25 GMT
2. Or you can use droplet/bead radiators and not worry about structure at all. I'm a fan of liquid boron encapsulated in tungsten. Why boron instead of, say, beryllium? Can an LDR ship reasonably evade for the duration of its engagement?
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Post by matterbeam on Feb 3, 2018 14:55:37 GMT
that was quite literally my entire point? But you came up with the problem, based on your own finding of some low-temperature reactor design.
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Post by jtyotjotjipaefvj on Feb 3, 2018 16:41:11 GMT
that was quite literally my entire point? But you came up with the problem, based on your own finding of some low-temperature reactor design. I did not suggest the 2 meter cube reactor, OMGitsWTF did: I looked up a paper evaluating the design, and found that it would be quite poor by the standards of our in-game reactors. Then we discussed potential improvements on the design, none of which would work since the outlet temperature is so low.
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Post by apophys on Feb 6, 2018 2:54:39 GMT
2. Or you can use droplet/bead radiators and not worry about structure at all. I'm a fan of liquid boron encapsulated in tungsten. Why boron instead of, say, beryllium? Can an LDR ship reasonably evade for the duration of its engagement? The latent heat of fusion (energy required to change from solid to liquid or back) for boron is the highest of any material I have encountered in reliable sources, around 4.6 MJ/kg. Beryllium also has a relatively high one, around 1.4 MJ/kg, but not quite in the same tier as boron. Beryllium is also expensive. Making use of this effect allows the radiator to stay at a near-constant temperature while it radiates heat, using the space allotted to it more efficiently. See this thread for how the idea came about, and for other filling material candidates I found in the high melting temperature range: childrenofadeadearth.boards.net/thread/1744/droplet-radiator-calculatorEvasion can be done with clever geometry, or by electrostatically charging beads and forcefully guiding them, or by attaching beads on a string like pearls.
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Post by tangentialthreat on Feb 6, 2018 9:34:38 GMT
CDE ships are set up to maintain their peak power output for months. Warship design starts with accepting that your baby is probably going to be dead, out of fuel, or victorious in a few minutes.
Surviving many kilowatts per kilogram for long enough is very possible if you're a household teakettle. Our NTRs don't melt because they are examples of open-cycle cooling. You start by using your fuel tanks as a heat sink, and if you have kilotons of mercury aboard for the MPD then you should be set for a while.
As desperation increases you begin throwing boiling coolant and fuel overboard. If you are dodging bullets and firing your engines full blast then that's okay because now you have a really great fuel preheater.
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