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Old 02-23-2020, 02:10 PM   #1
AlexanderHowl
 
Join Date: Feb 2016
Default Coolant [Spaceships]

One of the primary issues with reactionless engines is that they allow for every shuttle to become a WMD, as a SM+6 shuttle traveling at .01c is the equivalent of 100 megaton bomb. One way to deal with this issue is to arbitrarily have a speed limit, which mechanically works but is unsatisfying. Another way to deal with it is to use a consumable to limit the duration of the thrust, either as fuel or as coolant.

I tend to favor coolant because you can use water. For example, a reactionless drive could transform one component of water into steam (which is vented) for every days of thrust acceleration (a spaceship with 4g acceleration would vent four components of coolant every day). Since the thrust required for sustained acceleration would decrease as mass decreased, coolant would effectively function like reaction mass (for example, 10 components of coolant would allow for 14 days of thrust at 1g). When a spacecraft runs out of coolant, it suffers 10% of HP for every combat turn that it continues to maintain thrust, as the waste heat causes massive damage to the drives.

So, would you use coolant to control reactionless drives? Have you used something similar in your games? If so, what was your experience like?
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Old 02-23-2020, 02:12 PM   #2
awesomenessofme1
 
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Default Re: Coolant [Spaceships]

Seems like a solution in search of a problem to be honest. Just incorporate some kind of practical lock against high-speed ramming or just say out of universe "No, that's not a thing that fits into the game I'm trying to make."
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Old 02-23-2020, 02:56 PM   #3
Ulzgoroth
 
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Default Re: Coolant [Spaceships]

If you really want your reactionless drives to have limited delta-V, I'd question why you're using reactionless drives at all.
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Old 02-23-2020, 03:23 PM   #4
AlexanderHowl
 
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Default Re: Coolant [Spaceships]

Because superscience reaction drives that have high thrust and high delta-v are also WMDs in disguise. For example, a TL9^ nuclear saltwater reactor is continuous nuclear detonation that sprays radiative death as its reaction mass and it is the least dangerous of the bunch. A SM+6 shuttle with a TL12^ total conversion drive converts 3g of matter into pure energy per second, effectively detonating a 60 kiloton fusion bomb beneath it every second.

Coolant avoids both forms of WMD while allowing for a pleasing delta-v. A spacecraft with one component of water could achieve a delta-v of 500 mps while a spacecraft with ten components of water could achieve a delta-v of 7,000 mps. Of course, there may be some abuse still, so changing the duration of coolant to one hour per 1g of acceleration may be better (it still gives 20 mps and 280 mps respectively). At that point, spacecraft can get up to an acceptable delta-v without worrying about WMDs.
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Old 02-23-2020, 03:33 PM   #5
ericbsmith
 
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Default Re: Coolant [Spaceships]

Quote:
Originally Posted by Ulzgoroth View Post
If you really want your reactionless drives to have limited delta-V, I'd question why you're using reactionless drives at all.
Really. At that point just take one of the superscience Fusion Torches and adjust the thrust and/or fuel usage to suit your needs.
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Old 02-23-2020, 03:52 PM   #6
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Default Re: Coolant [Spaceships]

Quote:
Originally Posted by AlexanderHowl View Post
Coolant avoids both forms of WMD while allowing for a pleasing delta-v. A spacecraft with one component of water could achieve a delta-v of 500 mps while a spacecraft with ten components of water could achieve a delta-v of 7,000 mps. Of course, there may be some abuse still, so changing the duration of coolant to one hour per 1g of acceleration may be better (it still gives 20 mps and 280 mps respectively). At that point, spacecraft can get up to an acceptable delta-v without worrying about WMDs.
You do realise that at ~3 km/s (~2 miles/second) an object has kinetic energy equal to the chemical energy a lump of TNT of the same mass releases? That means that at 20 mps a 100 ton shuttle impacts with about 10 kilotons of energy. Any spaceship that can traverse interplanetary space at a half-reasonable speed and which is of a decent mass is a WMD, if it follows physical laws as we understand them.

If I was designing a setting from scratch that had fast space travel I'd consider wormholes or other FTL jumps that started in planetary orbit, so spaceships wouldn't need vast delta-vee to travel quickly, and/or inertialess drives that don't retain pre-engagement vectors (though they have other issues, I'm sure), and just throw out hard physics.
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Old 02-23-2020, 03:57 PM   #7
Ulzgoroth
 
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Default Re: Coolant [Spaceships]

Quote:
Originally Posted by AlexanderHowl View Post
Because superscience reaction drives that have high thrust and high delta-v are also WMDs in disguise. For example, a TL9^ nuclear saltwater reactor is continuous nuclear detonation that sprays radiative death as its reaction mass and it is the least dangerous of the bunch. A SM+6 shuttle with a TL12^ total conversion drive converts 3g of matter into pure energy per second, effectively detonating a 60 kiloton fusion bomb beneath it every second.
Torch scorch isn't much of a disguise, and is relatively easy to weaken as a weapon.

Imposing low reaction-stream focus on superscience torches stops them working as long range beam weapons. And at short range that "60 kiloton fusion bomb beneath it every second" isn't actually much like a 60 kiloton bomb - it doesn't stack up the energy into one big pulse, and in an atmosphere the engine is probably destroyed in much less than a second of operation.

There is the threat of holding a vacuum habitat hostage at docking ranges, though.

(NSW, on the other hand, is ludicrously unsafe at a minimum because it's a continuously-operating dirty bomb that makes Project Pluto look environmentally responsible. When operated as intended! And can be easily or accidentally converted into a nuclear meltdown instead.)
Quote:
Originally Posted by AlexanderHowl View Post
Coolant avoids both forms of WMD while allowing for a pleasing delta-v. A spacecraft with one component of water could achieve a delta-v of 500 mps while a spacecraft with ten components of water could achieve a delta-v of 7,000 mps. Of course, there may be some abuse still, so changing the duration of coolant to one hour per 1g of acceleration may be better (it still gives 20 mps and 280 mps respectively). At that point, spacecraft can get up to an acceptable delta-v without worrying about WMDs.
Coolant doesn't avoid arbitrary-velocity kinetic strikes, it just means you need to put in a little effort - you could retain the hot coolant and chill it down with radiators instead of discarding it. That would presumably hit your sustained acceleration pretty hard, but it's really hard to rule that people can't cool hot water.

(Plus that 7000 mps from 10 systems is nearly 0.04c, so if you're considering 0.01 c to be too much kinetic energy to allow, you've failed to produce the desired constraint by more than a factor of 3.)
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Old 02-23-2020, 04:00 PM   #8
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Default Re: Coolant [Spaceships]

Quote:
Originally Posted by Rupert View Post
Any spaceship that can traverse interplanetary space at a half-reasonable speed and which is of a decent mass is a WMD, if it follows physical laws as we understand them.
It only needs to be in orbit, or capable of reaching orbit.
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Old 02-23-2020, 04:04 PM   #9
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Default Re: Coolant [Spaceships]

Quote:
Originally Posted by Rupert View Post
Any spaceship that can traverse interplanetary space at a half-reasonable speed and which is of a decent mass is a WMD, if it follows physical laws as we understand them.
For some fun reading look up the "Rods from God" weapons platform. The basic idea of "Rods from God" is to put some telephone pole sized tungsten rods in orbit and then drop them on targets on the ground. Because of their size, shape, and composition they barely decelerate coming into the atmosphere and they hit with the equivalent force of a small nuclear weapon without any of the fallout.
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Old 02-23-2020, 04:22 PM   #10
AlexanderHowl
 
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Default Re: Coolant [Spaceships]

Tungsten heats up too quickly for that to be effective (it needs only .11 J/K/g, meaning that its higher melting temperature only matters if it does not keep heating up). Iron, by comparison, takes four times as much energy to heat up, and has a decent melting temperature and a decent density. A 10 meter long by 1 meter wide rod with a 10 meter long conical cap would mass around 80 meter and would hit with 800 metric tons of force (a third less than a similar tungsten rods). In addition, iron is everywhere on the moon, so you can just make spikes by the millions and use mass drivers to launch them from the moon.
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