Upthread, there was this post:
The Great Zaganza said:
Alistair Reynolds tries to be as realistic as the scenarios allow.
Stars, planets and other Sci-Fi peeves
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Upthread, there was this post:
Alistair Reynolds tries to be as realistic as the scenarios allow.
I would assume they would have some sort of standardized coordinate system. And they might travel along standardized paths. Plus, it is fiction. The ships have to meet for the story to progress.
What bugs me is when they come upon the site of an ancient battle and all the damaged ships and debris are just floating near each other. They should have drifted apart (or, if massive enough, drifted together).
Also .. smoke trailing behind a damaged spacecraft like it was an aircraft in the air.
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3point14
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So, I went away to Wikipedia to read about this fellow and found out that:
On March 10, 2019 Alastair Reynolds announced that his short stories "Zima Blue" and "Beyond the Aquila Rift" were adapted as part of Netflix's animated anthology Love, Death & Robots. These stories are the first of Reynolds's works to be adapted for TV or film.[22]
Coincidentally, I've watched a fair number of this series (it's good, by the way, but annoyingly, I thought the first one was the best one).
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Thanks for that.HansMustermann
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Speaking of Star Trek...
I don't understand your point, actually. It seems like you are saying that it would be easy for one spacecraft to destroy another. That seems to suggest that combat would be more likely not less.
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Fair point - I'm sort of thinking my way through it as I go.
The whole epic space battle, kilos and kilos of ordinance, armour plated spacecraft with all sorts of weapons. I just can't see it.
All you really need to do to disable a spacecraft and kill everyone on board is knock off whatever device it is that's cooling the thing which, by it's nature, is going to be long, wide, thin and fragile. Then bugger off.
I can't see that there will be the bucketloads of cletaV required for any craft to be anything more than a sitting target, shining like a beacon, on a predictable course made out of the lightest materials that will do the job.
Rather than any extended battles, I would imagine that any engagements would be extremely brief, allowing time for intercepts at orbital distances and velocities, and pretty much always ending with both craft destroyed or so badly damaged (which, doesn't need to be a lot) that everyone inside is already dead.
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That device could be a balloon or something like it that could be retracted in times of danger.
I started a thread once about the idea of just spraying some sort of coolant into space (and then collecting it once it had cooled*). While the idea seemed to be mostly inefficient compared to other options, it seems it would work and it might avoid the problem you are talking about.
*for instance you spray it out one side of your ship toward a little collector vehicle some distance away. By the time it has reached the collector, it's cooled down. The collector then comes back to your main spacecraft with it's cargo of coolant fluid. Repeat. If you want to avoid using up propellant maybe tether the collector to the main ship with a thin cable that it can use for the return.
Oh, absolutely.
To me it depends somewhat on the distances involved. Imagine your spacecraft just makes random course changes every few minutes. Even if the delta-v is tiny, if your enemy is light minutes away they can't predict where you will be, not only when their ordinance arrives, but even when they fire. The question is how realistic it is to be be able to make those sorts of constant changes in course, and I guess that comes down to the details of how frequent and what sort of acceleration would be necessary to avoid enemy fire. That also adds the question of whether or not it would be reasonable to think you could know if you were at risk of coming under fire.
The other question though that I'm not clear on is actually how far away you'd be able to track a spacecraft that is tens or even hundreds of meters long? Sure, it's giving off thermal radiation, but then everything in the solar system is giving off reflective light but as I understand it we are still unaware of the vast majority of smaller bodies.
HansMustermann
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Err, Robo? You know this better than me, probably, but just as a gentle reminder: temperature is a measure of the LOCAL chaos. If you can eject all your coolant going neatly together in the same direction and everything, and it stays that way all the way to your collector, then it's actually a jet of something very COLD.
In reality, a water molecule at 100C or so, goes on the average at about 600m/s (or about 1300 or so miles per hour for you imperial). And when it evaporates in space, it will go in all directions. If the exhaust nozzle is more or less a point, and it spends just, dunno, 10 seconds in space, you need a collector that's 12km across just to get about half your water back.
Plus, it seems to me like you're trying to invent a thermal perpetuum mobile. Because when those mollecules hit whatever you use as a collector, you get their kinetic energy back. It heats your collector. If you get it back as liquid water, you get the latent heat of vaporization back too, so no gain from having it vapourize in space in the first place.
Worse yet, you get the impulse too. So now your collector would have to use some thrusters to even stay at a constant speed. You want it to return? Well, that's extra. Thrusters on means more heat, though, plus the costs of the fuel.
So essentially you got your energy back AND more for the thrusters. As heat dissipation goes, you just invented something that's a net loss.
In reality, a water molecule at 100C or so, goes on the average at about 600m/s (or about 1300 or so miles per hour for you imperial). And when it evaporates in space, it will go in all directions. If the exhaust nozzle is more or less a point, and it spends just, dunno, 10 seconds in space, you need a collector that's 12km across just to get about half your water back.
Plus, it seems to me like you're trying to invent a thermal perpetuum mobile. Because when those mollecules hit whatever you use as a collector, you get their kinetic energy back. It heats your collector. If you get it back as liquid water, you get the latent heat of vaporization back too, so no gain from having it vapourize in space in the first place.
Worse yet, you get the impulse too. So now your collector would have to use some thrusters to even stay at a constant speed. You want it to return? Well, that's extra. Thrusters on means more heat, though, plus the costs of the fuel.
So essentially you got your energy back AND more for the thrusters. As heat dissipation goes, you just invented something that's a net loss.
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HansMustermann
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As a side note, even if you managed to somehow break the laws of thermodynamics to make that work, now instead of having to aim at your small vessel, I can aim at your 12 km collector behind you and disable you that way. Essentially then it replaces a small target with a huge target.
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FWIW, I remember some sprayed-liquid cooling concepts for spacecraft being trotted out in the early or mid 1980s, perhaps by Robert Forward (not sure about that part). The collector end was always firmly mounted to the spacecraft, and the working fluid was not supposed to evaporate during its time in space. The idea was that the mist would have a huge effective surface area, though I suspect that was based on a misunderstanding of what you can do with the effective surface area of a mist. AFAIK these were always just paper concepts and none were actually tested.
Treated reasonably well in
https://en.wikipedia.org/wiki/Downbelow_Station
and sequels - assume a probability-based cone for a ship's current position, based on last known location, velocity and engine capability.
I don't see how it breaks the laws of thermodynamics. It really works exactly the same as any other radiator it's just that the coolant moves freely through space instead of within some pipes.
So, is that a good idea? Well we get to get rid of the mass of those pipes, but they were doing something (containing the coolant). How hard is the collection problem? It's certainly not impossible.
With respect to conservation of momentum: if the collector is connected to the main ship (with a tether or otherwise) the situation is identical to if the coolant was flowing through pipes. If it's not? Remember that as the coolant is ejected it gives an impulse to the ship in the opposite direction. The collector collects it and recieves an opposite impulse. If it's not connected to the ship it will need to fire rockets to catch up to the ship, but the net effect will be the same as if the main ship had fired it's rockets in the same way, so just set it up to go in the direction you want to travel in. If you don't want to change course or speed then a tether is a better idea, but we're talking about a very small impulse here and course corrections are probably going to be required pretty frequently so I don't see this being an issue.
Anyway, I'm not saying it's a good solution to the problem of radiating heat in general. I'm saying it could be a good solution to the problem of radiators being an attractive target. Go for a more complicated and less efficient system of radiating heat in order to make a smaller target.
When I first posted that other thread that was the thought in my mind as well, but I think I was convinced that it really wasn't viable. However, in the special case of people worrying that radiators make a big target in space-warfare, this seems like a possible solution (then again, I have to worry about how big the collector dish has to be).
HansMustermann
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You're answering that to my objection that you'd need a collector that's a 12 km sail floating behind your ship, you know? How in Lucifer Morningstar's good name is that making your vessel SMALLER? Now instead of having a, what, tens to hundreds of meters worth of radiators as a target, I have something the size of a CITY that I can shoot to disable you. Because if your collector is in pieces, you're not going far before you overheat
Hell, I don't even have to completely shatter it. Disable some thrusters on it, and it'll never catch up with you.
You want a smaller vessel, here's a simpler idea: according to Messrs Josef Stefan und Ludwig Boltzmann, the heat you radiate is proportional to the 4'th power of the temperature of your radiator. So you just put a heat pump between your craft and the radiator. Hell, deck the radiator in Peltier plates.
So, say, you want to keep the interior of your galactic battleship at a comfy 25C or so. You know, light uniform kinda climate. You could just circulate your coolant directly, and have your radiators also at 25C (actually, lower, because they've already dissipated some, but let's ignore that for now). Or you could make it a big refrigerator, and have the radiators go up to, say, 325C. The difference is 300K vs 600k when radiating heat, so a 16 TIMES factor per surface unit.
There we go. Now you can make your radiators 16 times smaller.
Assuming the detection isn't the problem I'd see them using intelligent ordinance, the attacking ship throws it out based on a rough prediction of where the enemy will be, then as it gets closer it begins to fine tune its approach. Or even splits into different parts to increase the chance of a hit.
It would be extremely wasteful and any sudden large change of vectors would probably save the shop being attacked.
You must really hate January sails.