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Post by RiftandRend on Jan 22, 2017 7:17:02 GMT
Platinum coated internals might help resolve reactivity issues with less volatile propellents.
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Post by RiftandRend on Jan 22, 2017 7:15:08 GMT
<abbr>I'm guessing that it might result in a lower overall exhaust velocity due to the cooling propellants used. I've been thinking the same, actually, but the opposite way around. First superheat the chemical propellants in the nuclear core separately, (probably requires two asymmetric chambers to heat both as much as possible, because both of them are unlikely to have the same thermal properties) only then let them combust together in the nozzle.</abbr> I imagine both setups would work, depending on wether the reactants or products have higher molar mass.
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Post by RiftandRend on Jan 22, 2017 5:58:59 GMT
I was wondering, is there any reason why some sort of Chemical/Nuclear rocket wont work? For example you could burn LOX Decane and then pass the resulting H2O and CO2 through an NTR. This seems like a way to use the chemical energy of propellent that would normally be wasted in an NTR.
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Post by RiftandRend on Jan 20, 2017 23:08:09 GMT
What would you do about radiators? They would have to protrude beyond the armor layer and would be quite vulnerable. Superheavy armor seems like a waste if they can just target your radiators. Radiators would either be mounted in the shadow of the laser armor, or kept paper thin and aligned edge on to any laser fire. I've found that radiators hold up under laser fire pretty well if they're made with high temperature materials, especially when edge on the the laser. Wouldn't shockwaves traveling through the fluid armor snap off thin radiators?
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Post by RiftandRend on Jan 20, 2017 0:53:31 GMT
The most practical laser armor I can think of consists of a rough ultra low loss fused-silica/diamond/sapphire diffusion layer spaced far enough from an actively cooled mirror wall that even a gigawatt of incoming light can be cooled and dumped into radiators. Note: this armor fails as soon as the attacking laser operates at a wavelength that absorbs in the diffuser layer, or gets focused enough to shatter the diffuser layer. Shattering the diffuser layer takes TW/m^2 and dramatically shortens attacking laser range. Peap-hole turrets then allow kinetic guns to hide behind the armor and arc shots onto target. Sooty, ablative armor is likely to be moderately effective. I doubt it'll buy more than a few seconds, but also shouldn't instantly fail at some critical intensity. Good for disposable munitions, and as a last line of defense. Finally liquid metal armor stirred and retained by magneto hydro-dynamic pumps would be my choice for HEAVY armor. (I.e. use as armor Lead Bismuth Tin eutectic alloy, which melts at 95C) As a flowing liquid, it would spread heat well forcing most lasers to boil the whole armor layer. Vs kinetic rounds the density, thickness, and self-healing would make it resistant to all but the most massive shells. What would you do about radiators? They would have to protrude beyond the armor layer and would be quite vulnerable. Superheavy armor seems like a waste if they can just target your radiators.
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Post by RiftandRend on Jan 15, 2017 15:16:12 GMT
That was not at all evident to me in your original post, but I can see what you're saying somewhat in later posts. My apologies. EDIT: Right, so since I can't see the image at all, I'm running off of calcs that other people did later in the thread. So the laser hits in a circle 20 um across, so let's assume that it digs a hemispherical divot with that radius and that all of the diamond in that hemisphere flashes into plasma of T = 75000 K. Some basic PV = nRT calcs using the molar mass of carbon and the density of diamond gives a pressure of 624 kPa, or six orders of magnitude smaller than diamond's yield strength of 1.6 GPa. There's going to be an explosion, yes, but not one that actually deforms the armor to any extent, and the issue is compounded by the fact that there's not really going to be any containment of that plasma, so the pressure might not even build up to that point, it'll tend to just escape into space. Also, how the hell did you get that plasma temp, RiftandRend ? I thought "In order to beat the dead horse even more, I built the strongest laser I could and tested it at the shortest ranges I could." Implied that. I got that temperature through an incredibly simplistic (and inaccurate) calculation. I applied 375 Mj to 9 kg of diamond, roughly what occupies a .020 mm x 300 mm target. I applied it uniformly and instantly, which would not happen. To see the image you're going to have right click on the and open it in a new tab. If there's a better way to display it please tell me.
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Post by RiftandRend on Jan 15, 2017 7:11:09 GMT
I was arguing that the game has an inaccurate representation of laser damage.
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Post by RiftandRend on Jan 15, 2017 0:49:06 GMT
Why? Was my previous post wrong in some way? Also, properly aiming a 28 kt fixed laser is quite difficult so clinical tests are near impossible.
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Post by RiftandRend on Jan 14, 2017 23:45:31 GMT
At 3Km you are hitting a 20um radius circle. The spot you are putting that much energy into is so tiny the effect is minuscule. Maximizing intensity doesn't a good laser make. That 20 μm point should be filled with superheated plasma. With some simplistic calculations I predict the 2cm diamond layer to be heated to 75000k at the point of firing.
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Post by RiftandRend on Jan 14, 2017 16:01:47 GMT
For some reason the image isn't quite working. Right click and open it in a new tab.
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Post by RiftandRend on Jan 14, 2017 16:00:48 GMT
After a certain point, anymore concentrated laser power at a point does not make it better. This is because of vaporized material ends up refracting the laser to uselessness. So cutting things in half like some movie laser isn't going to happen. The amount of energy being delivered would cause the targeted point to explode. 2 Ej of energy will turn any known material to plasma in nanoseconds. That incredibly high temperature plasma would then explode outward from the targeted point. Edit: My calculations were off. The beam should deliver more along the lines of 900 Pj at 3 km. Edit 2: My calculations were totally false. Ignore this post.
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Post by RiftandRend on Jan 14, 2017 12:40:54 GMT
In order to beat the dead horse even more, I built the strongest laser I could and tested it at the shortest ranges I could. I was able to fire it from 2.97 KM for about 3 seconds. For some reason its 2 Ew beam intensity didn't lance through the entire ship, and only destroyed the top 2 cm Diamond and 3 cm Amorphous Carbon layers. As far as I can tell, this laser outperforms fusion ignition lasers by a significant factor so it should be able to cut through a few meters of aerogels with ease.
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Post by RiftandRend on Jan 14, 2017 12:05:03 GMT
Pockets of armor containing gas might be useful. When a laser burns a hole in the armor, the gas rushes out, attenuating the beam and carrying away heat from the armor. Using this technique, you could fill Whipple shields or use it as a last defense against laser damage. In this way it's sort of like reactive armor. Of course, the enemy could just wait for all the gas to escape and then fire again, in which case you're dead. When you vaporize solid you get much more gas, and vaporizing itself require a lot of energy - this is the way ablative shields work. Also, you probably need ridiculously thick armor (i think something like >> 10m), because gases are, hmm, quite transparent. Ahh, thanks.
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Post by RiftandRend on Jan 14, 2017 10:41:22 GMT
But how is that superior to a guided bomb or and RPG? They are not at all similar. A RPG is short ranged, unguided and has to be fired by a friendly person. Friendly people are usually politically important and have expensive life insurance policies. A guided bomb falls from an aircraft into either a GPS waypoint, image matching, IR target or laser spot. The bomb takes about a minute to fall. The bomb cannot decide to hover and fly off to a different target or provide recon for minutes or more. Neither can the bomb choose to send individuals of its swarm to engage separate targets. With a bomb you drop it, and a minute later you get a boom and that's it. Think about the spider bots in Minority Report that can recon an entire building and identify the occupants in a few minutes with zero risk to the human officers. I really should have said "But does that deviate from a guided bomb or an RPG?". What you described was more along the lines of a guided missile than a drone.
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Post by RiftandRend on Jan 14, 2017 0:31:49 GMT
Pretty cool, but what could you possibly arm something so small with? Shaped charges. The drone only fires once, killing itself, like a bee. After all, you've got hundreds of them. But how is that superior to a guided bomb or and RPG?
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