Rhyx wrote:

So if I understand correctly when dealing with a radiator you want to have the largest surface area possible as to diffuse the most heat you can without the radiator radiating the heat into itself (or the others) right? So it's almost like a solar panel in reverse? Which is why the droplet solution seems to be very solid since every drop will radiate in a spherical area (like a mini sun)? Could there be a way of using that waste heat to power secondary systems or even powering other less powerful ships around it, if you're using a cluster fleet approach. And aren't radiators a nightmare when it comes to being detected (since you light up like a gigantic yule log on IR)?

Yes, the total amount of heat you can radiate is proportional to the area, the temperature to the fourth power, and the emissivity (which cannot go above 1). Having a super-hot radiator is great, but it will have to be cooler than your reactor (otherwise you will have to pay extra energy for pumping heat into it) and in practice it is set by heat tolerances of what you build it out of. That is why a plasma would be so lovely. But without that, you want to have a lot of area pointing into empty space. You can use the heat from the reactor to do other things, like boil water or sodium to run turbines giving you electricity, or cooking marshmallows. The problem is that eventually you have squeezed all useful work you can get from it, and are left with plain waste heat. That is what you need the radiators to get rid of. And the total amount of waste heat per second is equal to the reactor power that is left in the ship (the big radiator of a fusion or AM rocket is the exhaust). And yes, radiators are nightmares from a stealth standpoint. They will be glowing *bright* in IR. In my calculations, I found that the Destroyer can be seen across *at least* 8 AU by a fairly modest sky-scan (and some other estimates think the visibility distance is more like 2,300 AU). Fortunately you only need them at full when you are accelerating at full power. When you are merely powering your Laser of Doom you need much less energy and cooling.

King Shere wrote:

What about jettison the heat, For example . heating something up (perhaps a radiator) and launching/jettison it. If it works as a weapon thats a bonus to some.

] Let's do the numbers. The Destroyer is by my latest estimate 800 GW. Let's say just 400 of those gigawatts end up in the ship and need to be radiated. The best thermal capacity you can get is hydrogen, which can absorb 14.30 J/gK. Let's assume you heat it 10,000 K into a plasma from 1 K (ignore changes in thermal capacity with temperature etc). That allows you to get rid of 143 MJ per kilogram. So the total amount of hydrogen metal you need to turn into plasma is 2,797 kg/s. That is, you are vaporizing ~3 tons per second. A typical launch burn lasts an hour or more, requiring you to burn at least 10,000 tons of coolant. This is in addition to the *fuel* of the ship, which weighs ~15,000 tons. Completely unworkable as main cooling, perhaps workable as cooling for lasers during battle. But you will be marking your position with a nice shining plasma cloud. OK, what about the fighter? It has a puny 16.8 MW reactor. That means (assuming 50% efficiency) that it requires 0.06 kg/s - actually quite doable, especially since it is a metallic hydrogen rocket that normally does the same thing for propulsion. It only got about 4 tons of fuel, so it gets just 18 hours of cooling even if it doesn't use any hydrogen for propulsion. Hmm, not *too* bad. Not stealthy by any means, but perhaps worth it during battle.

Using jetisonable heat sinks when a ship is under power is pointless, and no ship is going to have enough spare mass to use them for long periods of time. However, I can definitely see using them in battle, especially when the ship is closing on it's target. In such a situation, the ship does its final (highly visible) burn to get the desired delta-V well beyond the range of any possible attack. Then, the ship shuts down the main engine, turns off all nonessential power and coasts. To prevent it from being tracked, it changes its direction and velocity a bit using a low-efficiency mass driver engine that's designed far more for stealth than high acceleration. To deal with the waste heat from that and from essential systems like life support, the ship would use jetisonable heat sinks. This system would work even better if those heat sinks could be used as the reaction mass for the mass driver, but you'll also need to simply jetison most of the heat sinks in a far less energy intensive fashion. Before it went dark, the ship will also have sent a small group of small drones with excellent sensors ahead of it (perhaps also accelerated with the same mass driver), linked to the ship via QE comms. When it's in attack range, the ship powers up it's drive and weapons and relies upon the QE drones for targeting solutions. At this point, I can see two possible attack strategies and I'm not certain which works best. [B]1)[/B] Once in range of its target, the ship uses a mixture of rapid evasion to attempt to avoid being hit and concentrated weapons fire to end the battle rapidly. Once in range, this battle will likely be over in a few hours. Essentially, the ship jinks around while blasting the target with everything it has until one side or the other surrenders or is destroyed. [B]2)[/B] The ship comes in at a high delta-V and when it's attacking it accelerates rapidly away from the target. The goal is to deliver a single powerful attack (using lasers, missiles, mass driver rounds...) and then get out of range as rapidly as possible (while also evading). Then, the ship would loop around for another pass. Depending upon the relative velocity of the various opponents, this battle might take many days to resolve, and would consist of a series of high velocity passes with brief attacks and counterattacks when the opponents were briefly in range of one another. Obviously, option 1 works better if the attacker is more durable and has better weapons than the target, and option 2 works better if the attacker is more maneuverable and has better acceleration than the target. Thus, it sounds like option 2 would be used mostly for attacking habitats and other locations that might have powerful weapons, but lack their own destroyers. In a battle between two ships or even two fleets, I can see either option 1 or option 2 working, depending upon relative reaction mass reserves and relative strength. Thoughts?

IF anybody wants to add tactical ship-to-ship space combat to their game, check out Warcosm for Precis Intermedia. It's very nice, light, simple but fast and effective.

hi hi I think a lot of the points in that link are perhaps not fully applicable to the Eclipse Phase setting. They are sort of assuming a current technology level/ ∂V budget technology level, where as the ∂V budgets in Eclipse Phase give people a lot more leeway. Brachistochrone trajectories are entirely possible in Eclipse Phase, and while any attack will still be seen coming, mining space is really never going to be practical, at least not in a combat situation. You could maybe rig civilian ships with weapons and get close enough to a target through deception, but even knowing someone's orbital path, space is way too huge to mine. They are confusing the difference between thrust and velocity, which makes me question their propulsion technology assertions. Ion drives will give a craft a higher top speed than chemical rockets, and there is no reason why a ship cannot sport both. Also, combat effective gyroscopes are going to be massive and will significantly effect a craft's ∂V. If you want to point your weapon at a target, you might as well just put it on a turret rather than spinning the entire craft, since the weaponry is likely to be a much smaller fraction of overall mass. You can spin around all you want, but it isn't going to effect an enemy's targeting unless you thrust somewhere, and they'll see that either way. They know enough to realize that space combat will occur over long time intervals, but don't make the connection when talking about how laser weapons will have long recharge rates (supposedly rendering them un-viable), they're assuming a pre-fusion tech level, and don't know about bomb pumped lasers. A giant array of flexible mirrors could make a good orbital bombardment system in the inner system, fold them into a lens and burn targets like ants.

jsnead wrote:

Here are the full design stats that I used for all of the ships - I forgot that I hadn't posted them before: [B]Large Lander and Orbit Transfer Vehicle (LOTV)[/B] Dimensions: 25 m tall, 16 m in diameter (for LOTVs with hydrogen-oxygen engines) 19 m tall, 12.5 m in diameter (for LOTVs with metallic hydrogen engines) Fully Loaded Mass: 450 tons Empty Mass: 26 tons Maximum Acceleration: 2 Gs Performance & Payload: [I]Hydrogen-Oxygen Engine[/I] High Velocity Configuration (total Delta V = 11 km/s) 1 pilot, 6 passengers, 7 tons cargo or 1 pilot, 20 passengers, 4 tons of cargo. Low Velocity Configuration (total Delta V = 7 km/s) 1 pilot, 100 passengers, 40 tons cargo [I]Metallic Hydrogen Engine[/I] High Velocity Configuration (total Delta V = 17 km/s) 1 pilot, 250 passengers, 70 tons cargo Low Velocity Configuration (total Delta V = 8 km/s) 1 pilot, 350 passengers, 120 tons cargo [B]Small Lander and Orbit Transfer Vehicle (LOTV)[/B] Dimensions: 17 m tall, 11 m in diameter (for LOTVs with hydrogen-oxygen engines) 13 m tall, 8.5 m in diameter (for LOTVs with metallic hydrogen engines) Fully Loaded Mass: 150 tons Empty Mass: 11 tons Maximum Acceleration: 2 Gs Performance & Payload: [I]Hydrogen-Oxygen Engine[/I] High Velocity Configuration (total Delta V = 11 km/s) 1 pilot, 2 passengers, 200 kg cargo Low Velocity Configuration (total Delta V = 7 km/s) 1 pilot, 30 passengers, 11 tons cargo [I]Metallic Hydrogen Engine[/I] High Velocity Configuration (total Delta V = 17 km/s) 1 pilot, 70 passengers, 20 tons cargo Low Velocity Configuration (total Delta V = 8 km/s) 1 pilot, 100 passengers, 40 tons cargo [B]General Exploration Vehicle (GEV)[/B] Size: 6 m long, 2.2 m wide, 2 m high 5.5 tons fully loaded, 3 tons empty. Fully Loaded Mass: 5.5 tons Empty Mass: 3 tons Maximum Acceleration: (space) 0.1 Gs Performance: (space) Total Delta V of 3.6 km/sec from metallic hydrogen rocket (land) Top speed 200 kph from wheels or 40 kph from legs. (sea) 60 kph on the surface or 40 kph submerged. Payload: up to 6 human-sized morphs + 1 ton of cargo [B]Fighter[/B] Size: 4.5 m long, 3 m wide, 3 m high, 7 tons fully loaded, 3 tons empty. Fully Loaded Mass: 7 tons Empty Mass: 3 tons Maximum Acceleration: 3 Gs Performance: (space) Total Delta V of 11 km/sec (using metallic hydrogen rockets) Payload: weapons + 1 synth morph (optional). Carrying a synth morph reduces the missile launcher to holding only 4 missiles. [B]SCUM Barge[/B] Size: 300 m long, 70 m wide, 70 m high Fully Loaded Mass: 180,000 tons Empty Mass: 80,000 tons Maximum Acceleration: (space) 0.003 Gs (0.015 Gs using a Fusion Rocket) Performance: Total Delta V of 80 km/sec (using plasma rockets) Ships refitted with Fusions rockets have a Total Delta V of 400 km/s Payload: 20 crew + 20,000 humanoid passengers in cramped long term occupancy, and 4,000 tons cargo [B]Standard Transport[/B] Size: 150 m long, 25 m wide, 25 m high (80 m wide and high with rotating booms fully extended) Fully Loaded Mass: 10,000 tons Empty Mass: 4,500 tons Maximum Acceleration: (space) 0.02 Gs Performance: Total Delta V of 400 km/sec (using fusion rockets) Payload: 13 crew + 200 humanoid morphs in long term comfortable occupancy and space for 1,000 tons cargo [B]Bulk Carrier[/B] Size: 150 m long, 25 m wide, 25 m high + externally mounted cargo pods Fully Loaded Mass: 90,000 tons Empty Mass: 4,500 tons Maximum Acceleration: (space) 0.002 Gs Performance: Total Delta V of 40 km/sec (using fusion rockets) Payload: 10 crew + 100 passengers in comfortable long-term occupancy, and 80,000 tons of bulk cargo [B]Fast Courier[/B] Size: 75 m long, 13 m wide, 13 m high Fully Loaded Mass: 1,000 tons Empty Mass: 300 tons Maximum Acceleration: (space) 0.2 Gs Performance: Total Delta V of 1,600 km/sec (using anti-matter rockets) Payload: 3 crew + 10 passengers in comfortable long-term occupancy, and 100 tons of valuable cargo [B]Destroyer[/B] Size: 150 m long, 50 m wide, 50 m high Fully Loaded Mass: 40,000 tons Empty Mass: 25,000 tons Performance: Total Delta V of 800 km/sec (using anti-matter rockets) Payload: 70 crew and 20 fighter pilots in military style long-term occupancy, + 1,000 tons of weapons & 20 fighters and metallic hydrogen fuel to refuel them twice. [B]Note:[/B] I specifically did not make the destroyer long and thin, in order to make it less fragile - having a ship that you can easily cut in half seemed problematic to me.

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