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Post by zuthal on Jun 20, 2017 9:17:06 GMT
Nitrile rubber is, according to Wikipedia, resistant against aliphatic hydrocarbons, which all the hydrocarbons we have fall under, and PTFE should be resistant to attack by hydrocarbons as well - fluorocarbons are afaik generally insoluble in hydrocarbons.
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Post by zuthal on Jun 19, 2017 20:18:09 GMT
Yeah, would just need an interface really to export a ship not just as a .txt, but as a 3D model file. Though, regarding the scale and such, printing would likely only be feasible for sensible ships - not for laserstars with radiators that go out 100s of km.
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Post by zuthal on Jun 18, 2017 13:19:46 GMT
I don't think defining an LDT for other carbon allotropes would make that much sense - as it is only really useful on materials that are either transparent (diamond, fused quartz etc) or reflective (metals).
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Post by zuthal on Jun 17, 2017 7:05:08 GMT
Hmmm... since CoaDE gives, in the export file, all the parameters of each part, and since from those parameters (and knowing how the parts are defined) you can calculate the actual shape of it... would it be possible to make a program that, for a given CoaDE export file, automagically generates a 3D model of that ship/part?
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Post by zuthal on Jun 3, 2017 20:59:53 GMT
The problem sounds like it is the defender (which is on a doctrine that launches missiles) not using missiles to intercept an incoming Striker fleet, not the Striker fleet not using missiles.
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Post by zuthal on May 30, 2017 9:27:44 GMT
I don't see how carbon clogging is an issue. The engines in my ships only can run for ~10 min until the tanks are dry. I highly doubt that any appreciable soot buildup could occur during that time. Even across multiple full burns and re fuelings this should be a non issue. Even if it is, cleaning the engine should be a fairly trivial task, just attach a grinder to a drone and remove it. The thing is, we are talking about hundreds of kilos to several tonnes of propellant per second, propellant which is >80% carbon by mass, through reactor cores with a total mass of only a few dozen kilos or so. So, even assuming less than 1% of the carbon soot produced deposits, it will deposit an amount of carbon equal in mass to the reactor core within those few minutes.
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Post by zuthal on May 26, 2017 11:04:47 GMT
I wonder... Is dissociation that powerful? Possibly. Dissociation of Metallized Hydrogen, for example, is more energetic than standard (i.e. NERVA) nuclear rocketry. Of course, I doubt hydrocarbons are quite as energetic, otherwise a fuel tanker would have yield in the hundreds of tonnes and if terrorists realized this we'd be super fucked. Metallic H actually has a positive enthalpy of formation - this means that it actually releases energy when dissociating and then recombining into H2 gas. On the other hand, hydrocarbons have a negative enthalpy of formation, so there dissociation (even with recombination of the hydrogen into H2) consumes energy. That was I think also the problem with resistojets violating energy conservation - energy lost to dissociation was not being modeled.
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Post by zuthal on May 25, 2017 20:50:02 GMT
Also if you don't change the output of the laser, the decrease could be due to the beam being too narrow to hit the same spot repeatedly, ie, the the illuminated spot being much smaller than the wobble of the laser. I actually made sure that that wouldn't be the case - the aperture radius at which, for 77 nm lasers, the wobble is equal to the beam spot size (so it just barely always touches the same spot) is, according to my math, 12.4 cm. So, I made sure to always keep the aperture radius below 6.2 cm, ensuring that the laser would always cover at least one spot fully.
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Post by zuthal on May 23, 2017 21:42:03 GMT
Apparently yes, at least if you have a wide-beam laser, i.e. your aperture radius is a lot less than 12.4 cm.
And core2, I do plan on doing that - because while I would expect laser ablation rate to be sublinear with intensity, this is ridiculous.
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Post by zuthal on May 23, 2017 9:55:14 GMT
Inspired by David367th 's laser science thread, I decided to do some more detailed investigations - specifically, in the relationship between laser intensity and burn rate. I started with aramid fiber because, well, it is one of the quintessential anti-laser armour materials, and decided to do it in the wide-beam limit (beam width much greater than laser wobble) and with a 77 nm Ce:LLF laser. It seems that up to a certain point, the burn rate increases linearly with intensity, only to then drop sharply again and get to a roughly constant value at even higher intensities - our standard "critical burn rate" value, which for aramid fiber is about 1.3 mm/s, from the data I have, giving it an anti-laser performance of 1.82 kg/(s*m^2) and 480.48 c/(s*m^2). What confuses me is this peak - is it just an artifact due to the measurement method, a glitch, or a real effect?
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Post by zuthal on May 22, 2017 14:43:48 GMT
I think the thing that makes most sense for a performance metric is kg/(s*m^2) or c/(s*m^2), i.e. how much mass or how much cost you have in armour, if you want to shield 1 m^2 of area for one second. The first one is calculate as (ablation rate)*(armour density), and the second is the first, multiplied by the armour cost. In both cases, lower numbers are better.
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Post by zuthal on May 16, 2017 9:37:31 GMT
Not sure about that, actually - the sublimation point of carbon goes up quite a bit with increased pressure, until its triple point at ~4600 K and ~11 MPa - and given that chamber pressures in our NTRs are often quite a bit higher than that, over 100 MPa, I'd assume that even with 4400K graphene cheese NTRs, you still wouldn't be able to melt or sublimate the carbon.
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Post by zuthal on May 15, 2017 9:21:00 GMT
True, you need to consider intensity as well - though that is mainly a problem for low- to medium-power lasers. For example, with a 77 nm Ce:LLF laser at 28.9% efficiency, to reach 20 MW/m^2 at 1000 km with the critical aperture radius, you need ~100 MW beam power, which corresponds to ~340 MW input power.
High power doomlasers might potentially run into a different issue altogether with that, though - that of the mirror not being able to withstand the intensity, thus forcing you into using a larger aperture.
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Post by zuthal on May 14, 2017 21:10:04 GMT
Vance, on the Discord chat (his forum nickname eludes me currently) has figured out that the inherent wobble of lasers in-game has a diameter of 2.5 mm/km. Both the width of that wobble and the width of the laser beam are linearly proportional to range, and so there is one single optimum mirror radius for each wavelength that leads to the laser beam radius and wobble radius being equal at all ranges - and thus the laser always hitting the target.
This is calculated by solving the equation P/I/((1.25 mm)^2*π) for I, where P is your laser's beam power, and I is the intensity at 1 km that you should aim for. For example, for a 724 kW beam power laser, the optimal intensity at 1 km distance is 147.5 GW/m^2, which, for a 77 nm Ce:LLF laser, corresponds to an aperture radius of 12.4 cm.
EDIT: I did some science with other laser wavelengths, and the relationship between optimal aperture radius and wavelength is proportional, with a proportionality constant of 0.1607 cm/nm. So, just multiply your wavelength in nm by 0.1607, and you have the mirror radius in cm that will make the beam radius just as wide as the laser wobble! Note: This assumes an M^2 of 3.00. Results may contain traces of cerium-doped lithium lutetium fluoride.
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Post by zuthal on May 14, 2017 17:26:10 GMT
Yeah, the boron that results from the decomposition of diborane melts at ~2300 K, so it will be definitely molten inside the core - and then come out as a fine spray, carried along by a jet of hot hydrogen.
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