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Post by newageofpower on May 27, 2017 14:40:00 GMT
10mg should still be fine when your engagement range is multiple solar radii..
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Post by bigbombr on May 27, 2017 18:50:09 GMT
10mg should still be fine when your engagement range is multiple solar radii.. Still pretty decent, 10.4 kt and 3.4 Gc. Most of the cost (4/5) and mass (2/3) is obviously radiators.
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Post by imallett on May 27, 2017 21:17:54 GMT
First assumption problem: assuming you are optimized. childrenofadeadearth.boards.net/post/22998/threadUnder 60kt for a laser warship here, and Apophys is not using modded materials. Ce:LLF based lasers can pass 40% efficiency (although have a lower melt temperature) and in the future we'd be using FELs with 70% or better efficiency. My laser was optimized for output efficiency (and it is ~twice as efficient). If you optimize for mass/cost, you can make it lighter/cheaper, at the expense of needing more power/radiators. So, fair enough. Still, I think the story still plays out. Even though the laser is 40.1x more powerful, it's a 15x bigger target. And again, even if you play games like hiding your radiators along the direction of attack, hitting a 1.1km x 1.17km target window at interplanetary distances is easy-ish. What are your rails? My 200km/s designs firing 1 gram graphene reinforced bullets mass over 800t each... Before power, radiator, fuel etc... It doesn't have to be a particularly special railgun. One would maximize accuracy instead of speed, and then fire a zillion tiny slugs over a, say, 100km^2 area where your laser star is. You continue this for weeks or months, forcing the laserstar to burn constantly in random directions, assuming it actually can dodge every slug (which again, I doubt). The above laserstars have burn times measured in weeks. We need transit times, though. How quickly can you get your laserstar across the solar system to intercept the railgunner, who can move also? Secondly, you'd never deploy a solo ship; send out a wing of recon drones to spot the incoming kinetic shells. This is a good point. I don't have a good intuition of the maximum range of a radar designed to pick up tiny fast movers, but the problem is certainly helped by recon drones. Regarding TIR... Is there a good reason not to use UV or shorter wavelengths? Sub-20nm we'd need diffraction-based focusing, I guess. Generally, shorter wavelengths are better, diffraction-wise. One important point I should continue to stress is that defending missiles, etc., vs. lasers using TIR requires knowing what wavelengths the laser uses (so that you can pick a material with a refractive index less than 1 at that wavelength).[EDIT: Aluminum has a complex-valued refractive index that eliminates the TIR regime, so for that material at least, TIR defense is not possible; sorry.] It occurs to me that a good laser battlestar would have the option of firing on multiple frequencies somehow. EDIT: In addition to FEL tech, we'd never use gigantic radiator panels on a warship. LDRs, my friend, are the future. (Assuming meaning liquid-droplet radiators.) These have problems, but frankly I agree. The other thing I wish were modeled in CoaDE is heat sinks. If my radiators get shot off (or I retract them), I should be able to store at least some waste heat. You should try out the current metagame - with distributed fire, missile swarms are far more manageable with high velocity railguns. Yeah; I really should. I did something of the sort a while back, though to get high-velocity railguns, I seem to always require very long barrels, which don't turn, like, at all.
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Post by Enderminion on May 27, 2017 21:31:52 GMT
You should try out the current metagame - with distributed fire, missile swarms are far more manageable with high velocity railguns. Yeah; I really should. I did something of the sort a while back, though to get high-velocity railguns, I seem to always require very long barrels, which don't turn, like, at all. Van-chrome steel projectiles with a large (4-10mm) bore can get speeds >200km/s
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Post by bigbombr on May 27, 2017 21:38:35 GMT
Yeah; I really should. I did something of the sort a while back, though to get high-velocity railguns, I seem to always require very long barrels, which don't turn, like, at all. Van-chrome steel projectiles with a large (4-10mm) bore can get speeds >200km/s If you're willing to use mods, than graphene projectiles are even better, because they can survive even more extreme accelerations before shattering.
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Post by apophys on May 27, 2017 21:59:23 GMT
It might not play out particularly well in-game, but the main intuition here is that both lasers and k-slug weaponry suffer an inverse square falloff—but for lasers, it's effectiveness whereas for rail-/coilguns it's accuracy. While this is true, there's a fundamental issue. In order to increase effective range, railguns need to increase muzzle velocity, which scales with the square root of power input (perfect accuracy is useless if it can be dodged with nano-G levels of acceleration). In order to increase effective range, lasers need to increase intensity at range, which scales directly with power input and aperture area. When the numbers are large enough, lasers win without real contest. Other points: 1. In the game, comparable kinetics can at best score a mutual kill - the laser will have completed the engagement before the k-slugs have a chance to reach it. 2. A proper kinetic ship will also have large radiators for its power supply. If radiators are a weak point (which they really aren't, since they can be pointed edge-on), the kinetic ship will have its capabilities reduced much sooner. 3. Disabling a laser in reality should not be as simple as poking a 1mm hole in the main mirror. So a larger aperture doesn't give the kinetic ship that much of an accuracy boost (granted, sub-gram flak rounds do help things for the kinetic side). 4. Assuming an intensely accurate but low velocity railgun attacking before the laser is in range, and knowing the velocity of enemy rounds, the laser may simply fire along the intercept with its own expected trajectory to divert away possible bullets by ablation. We need transit times, though. How quickly can you get your laserstar across the solar system to intercept the railgunner, who can move also? It occurs to me that a good laser battlestar would have the option of firing on multiple frequencies somehow. For one point of transit data, I completed Homecoming within 2.5 months by spending 422 km/s dV, using a near-perfect brachistochrone trajectory ( link). No mods, just supercharged MPDs. My time was matched later by a fellow forum user (in the same thread). Indeed, the laser cavity is insignificant in cost and mass compared to the mirror assembly. It shouldn't be that hard to have several optimized cavities for different frequencies and swap between them. However, high frequencies have significantly better intensity at range for the same aperture, so generally the choices taken should be expected to be above visible.
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Post by nerd1000 on May 28, 2017 1:51:02 GMT
Why use railguns when you can use missiles?
Any of these laserstars is a colossal heat signature whose movements are obvious anywhere in the solar system- there's no mistaking what's going on when one of these things leaves port. So rather than attacking with a warship, you build a bunch of MPD powered missile buses at your main base and send them to intercept. Now the laser can of course start shooting at the missiles from 10Gm or whatever, but this is also the point where we go recursive ammo on the laserstar's ass: the buses launch a bunch of smaller sub-buses, which have higher-G NTR drives for course corrections. Maybe we carry 4 per bus. At 10Gm, a fleet of 50 buses becomes 200 sub-buses. The sub-buses finish their burns and release their own submunitions.
Now if we assume that modern computer tech is a good guide, these sub-munitions can be made very lightweight: a simple CCD seeker, computer, battery and so forth should weigh less than 50 grams, so we can have a projectile massing around 300g with mass fraction of around 3, giving a nice supply of delta-V for the terminal stage with chemical rockets. A missile with 3kg payload could carry 10 of them, but there's no reason our sub-buses couldn't be built up to a payload of around 30 kg and thus carry 100 'soda cans of death'. We now have 20000 homing impactors inbound on the laserstar. The impactors spread out into a field that encompasses the entire area the laserstar could maneuver into in the remaining time before impact. Because these munitions are very small, they'll be hard to hit even with a mega-laser and they can avoid the beam by jinking around at random until they're close enough for random walk to be ineffective. With 300g mass at impact velocities of up to 50 km/s, a single impactor successfully striking the target will be an instant kill. It would be trivial to also carry dumb kinetic 'sand' that follows the SCoDs, further enhancing the kill probability. If you suspect that the laserstar will shoot down all 20,000 impactors before they get to it, it is trivial to send more missile buses because they're way cheaper than a laserstar can be.
CoaDE of course doesn't let you mess about with such tiny submunitions, but I was easily able to build a missile bus that has 70 km/s deltaV, 4.5 mg acceleration and carries 30 sub-drones for a little under 5 Mc. Each sub-drone carries 20 13.9 kg flak missiles, for a total of 600 submunitions per bus. For the cost of a single 'Finger of Boron Almighty' I could have 140 buses, 4200 sub-drones and 84000 flak missiles all on a collision course with the laserstar. With such high closure speeds, my missiles don't need to fly all the way in to a hit: they can burn out into a 'shotgun' pattern and detonate their flak bombs long before they enter the range at which the laser can zap them almost instantly, and even if it does kill them the debris is still inbound and will have to be avoided. Missile spam FTW!
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Post by acrosome on May 28, 2017 3:12:40 GMT
The other thing I wish were modeled in CoaDE is heat sinks. If my radiators get shot off (or I retract them), I should be able to store at least some waste heat. For instance, by dumping heat into those gigantic tanks of propellant that you're hauling around...
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Post by apophys on May 28, 2017 3:26:22 GMT
Any of these laserstars is a colossal heat signature whose movements are obvious anywhere in the solar system- there's no mistaking what's going on when one of these things leaves port. So rather than attacking with a warship, you build a bunch of MPD powered missile buses at your main base and send them to intercept. Any MPD drive is a large visible heat signature due to the power required, and a fleet of them is a very very large signature. There is nothing to write home about here. There is no need to focus on each individual munition specifically if they are that small. The beam of the 1 TW laser would encompass ~1570 m 2 at 10 Gm with intensity 24.9 MW/m 2 (and of course its efficiency is a measly 3.92% because it doesn't use mods). Jinking around at random won't get them very far in the time it takes for light to reach them. That's pretty good. But 70 km/s speeds will get the fleet through the 10 Gm killzone in 40 hours... assuming the laserstar didn't decide to accelerate away from you and either dodge entirely or match your trajectory, turning it into a game of shooting fish in a barrel. An MPD-based railgun capital could do more or less exactly the same. Delta-V is king in defining encounters; it goes for both sides. 70 km/s isn't anywhere near enough. I wish we had particle accelerators for another weapon to try; I think they could outclass railguns.
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Post by The Astronomer on May 28, 2017 4:14:21 GMT
Any of these laserstars is a colossal heat signature whose movements are obvious anywhere in the solar system- there's no mistaking what's going on when one of these things leaves port. So rather than attacking with a warship, you build a bunch of MPD powered missile buses at your main base and send them to intercept. Any MPD drive is a large visible heat signature due to the power required, and a fleet of them is a very very large signature. There is nothing to write home about here. There is no need to focus on each individual munition specifically if they are that small. The beam of the 1 TW laser would encompass ~1570 m 2 at 10 Gm with intensity 24.9 MW/m 2 (and of course its efficiency is a measly 3.92% because it doesn't use mods). Jinking around at random won't get them very far in the time it takes for light to reach them. That's pretty good. But 70 km/s speeds will get the fleet through the 10 Gm killzone in 40 hours... assuming the laserstar didn't decide to accelerate away from you and either dodge entirely or match your trajectory, turning it into a game of shooting fish in a barrel. An MPD-based railgun capital could do more or less exactly the same. Delta-V is king in defining encounters; it goes for both sides. 70 km/s isn't anywhere near enough. I wish we had particle accelerators for another weapon to try; I think they could outclass railguns. EHHHHHHHHHHHH? ?? 10 Gm???
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Post by apophys on May 28, 2017 5:12:03 GMT
EHHHHHHHHHHHH? ?? 10 Gm??? Yeah, didn't you see the terawatt laser ship thread? I routed 1 TW of power into a single laser, and its aperture is 478 meters in diameter. The intensity at 1 Mm is 2.49 PW/m 2, so it follows that it would get a very nice 24.9 MW/m 2 out at 10 Gm if CoaDE allowed such range. Needs limit editing of course, but no mods (mods would make it quite a bit better).
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Post by ash19256 on May 28, 2017 5:51:25 GMT
EHHHHHHHHHHHH? ?? 10 Gm??? Yeah, didn't you see the terawatt laser ship thread? I routed 1 TW of power into a single laser, and its aperture is 478 meters in diameter. The intensity at 1 Mm is 2.49 PW/m 2, so it follows that it would get a very nice 24.9 MW/m 2 out at 10 Gm if CoaDE allowed such range. Needs limit editing of course, but no mods (mods would make it quite a bit better). I somehow get the impression that either that's an extreme edge case causing the integrator or whatever to go off the deep end, or TW power level Ce:LLF lasers would be the closest we will ever come to a real life death star.
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Post by nerd1000 on May 28, 2017 6:10:42 GMT
Any of these laserstars is a colossal heat signature whose movements are obvious anywhere in the solar system- there's no mistaking what's going on when one of these things leaves port. So rather than attacking with a warship, you build a bunch of MPD powered missile buses at your main base and send them to intercept. Any MPD drive is a large visible heat signature due to the power required, and a fleet of them is a very very large signature. There is nothing to write home about here. There is no need to focus on each individual munition specifically if they are that small. The beam of the 1 TW laser would encompass ~1570 m 2 at 10 Gm with intensity 24.9 MW/m 2 (and of course its efficiency is a measly 3.92% because it doesn't use mods). Jinking around at random won't get them very far in the time it takes for light to reach them. That's pretty good. But 70 km/s speeds will get the fleet through the 10 Gm killzone in 40 hours... assuming the laserstar didn't decide to accelerate away from you and either dodge entirely or match your trajectory, turning it into a game of shooting fish in a barrel. An MPD-based railgun capital could do more or less exactly the same. Delta-V is king in defining encounters; it goes for both sides. 70 km/s isn't anywhere near enough. I wish we had particle accelerators for another weapon to try; I think they could outclass railguns. Why would I put the submunitions so close together that you can hit more than one at the same time? Your beam has radius 22m at 10Gm, making dodges difficult (22 m/s per jink at 1 light second? not happening, especially over a 40 hour flight) but I could easily have them spaced out so that they're over 1000m from their neighbors during most of the trajectory. I guess the cans should also be polished to laser-mirror level shine: this will let them resist around 1.2 GW/m^2 if the skin is aluminium. If the laserstar accelerates away from my missiles and matches their speed I've won: he might have been able to kill all my munitions, but he's also burned 70 km/s or more of his Delta-V, so he probably won't be able to go wherever he was planning to go (well, not fast anyway). This makes an interesting tactical situation: the laserstar must guess the performance (and numbers- there's no reason to assume all my buses carry the same amount) of my missiles, and decide whether he can simply zap them all while staying on course. If he can, my missiles are totally wasted. If he can't, he has no choice but to spend delta-V to keep them at arms length for long enough to destroy them. At the same time, he may have enough Delta-V for multiple dodges, so I have to decide how many missiles to send in each salvo: too few and they'll be wasted, too many and I won't have enough left to force another dodge later. TBH the way MPDs scale with power means that I'd probably be better off putting more eggs in each basket and having bigger missile buses, possibly to the point where they're a fully crewed 'missilestar' as opposed to a laserstar. The problem with that idea is that once I've built such a large MPD powered ship there's no reason not to put a laser on it, so we end up with laserstar vs. laserstar again. And I agree on particle beams. While they're sure to be shorter ranged than lasers, they also don't need giant mirrors (a pencil sized firing port will suffice) which makes them much harder to destroy with other beam weapons. Speaking of which, how well would your 1TW laserstar fare against smaller counter-laser ships? The mirror appears to be the size of a football pitch, so the counterbattery doesn't really need a big aperture to focus all of its laser energy onto a small part of the beam spreader. Edit: I just redesigned my missile buses. They now cost 9 Mc, carry 60 sub-drones each and have 120 km/s of Delta-V with terminal acceleration of 20 mg, which should be enough to deal with the Finger of Boron Almighty's maneuvering capabilities. I feel that it's a little unrealistic to be pumping 1.02 GW through each of the 180 gram MPD thrusters... But the game let me get away with it.
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Post by RiftandRend on May 28, 2017 7:32:22 GMT
I wish we had particle accelerators for another weapon to try; I think they could outclass railguns. This weapon is somewhat like a particle accelerator. ~12,000 1 microgram graphene needles fired at 2.45% C.
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Post by bigbombr on May 28, 2017 8:08:07 GMT
... I guess the cans should also be polished to laser-mirror level shine: this will let them resist around 1.2 GW/m^2 if the skin is aluminium... If their skin is actively cooled. Otherwise, it would probably last a few seconds at most. Active cooling requires coolant, pipes, a turbopump, radiators and energy. This increases the mass and complexity of your missiles considerably. This means you can field considerably less of them.
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