[Spaceships]If Hyperspace is a fluid medium

[Langy]

Originally Posted by vicky_molokh

For a game, collision rules might be good enough - 186,000 mps is pretty near c, multiply that by 6d by HP/ST (use dHP/dST for dDamage). Just make that explosive damage.

For velocities close to c (such as 186,000 miles per second or 0.9985 c) you need to account for the relativistic mass's effect upon kinetic energy. You can do that by multiplying the damage by 1/(1-v^2/c^2)^(1/4) - that's the square root of the Lorentz factor (damage is proportional to the square root of kinetic energy while kinetic energy is directly proportional to mass). In this case, that means multiplying by 4.274.

[vicky_molokh]

Originally Posted by Langy

For velocities close to c (such as 186,000 miles per second or 0.9985 c) you need to account for the relativistic mass's effect upon kinetic energy. You can do that by multiplying the damage by 1/(1-v^2/c^2)^(1/4) - that's the square root of the Lorentz factor (damage is proportional to the square root of kinetic energy while kinetic energy is directly proportional to mass). In this case, that means multiplying by 4.274.

Or just calculate by mps of actual delta-V spent accelerating as opposed to 'raw' speed.

[Adina]

Originally Posted by Anthony

More than a G over the long term isn't acceptable.

Originally Posted by ericbsmith

Fit humans could probably manage 1.25 to 1.5G in the long term.

What is long-term here?

How long can a crew function at 1.5 G's? Minutes, hours?

Specifically what accelerations are reasonable for combat maneuvering? And could a picked crew on a small ship push it a little higher?

[Adina]

Originally Posted by Anthony

However, note that a reactionless drive that operates by the principles you describe will have an energy requirement that varies with velocity relative to hyperspace, with the result that high acceleration will not be possible unless your velocity is very near zero or you have enormous power density available (it appears that 1 EP is on the order of 100 kW/ton. This will allow 1G acceleration if your velocity relative to hyperspace is 10 m/s or lower...).

So acceleration decreases as velocity increases. That would mitigate the near-c issue. I'm afraid I don't understand how you derive the increasing energy requirements.

Jeff

[Anthony]

Originally Posted by jmurrell

So acceleration decreases as velocity increases. That would mitigate the near-c issue. I'm afraid I don't understand how you derive the increasing energy requirements.

Power = Force * Velocity.

1G = 10,000N/ton, so power requirement = (mass in tons) * (velocity in m/s) * 10 kW.

[Adina]

Originally Posted by Anthony

Power = Force * Velocity.

1G = 10,000N/ton, so power requirement = (mass in tons) * (velocity in m/s) * 10 kW.

So how does this apply to reactionless drives and not to reaction drives?

[lexington]

Originally Posted by jmurrell

So how does this apply to reactionless drives and not to reaction drives?

It applies to both but reaction drives are dumping material out the back in order to do it rather than creating motion whole cloth from energy (though some reactionless engines create it from nothing).

[Adina]

Originally Posted by lexington

It applies to both but reaction drives are dumping material out the back in order to do it rather than creating motion whole cloth from energy (though some reactionless engines create it from nothing).

Ah. I was not clear. I was envisioning 'reactionless' drives as using the hyperspace fluid as reaction mass. Essentially using hyperspace as an infinite capacity fuel tank.

[lexington]

Originally Posted by jmurrell

Ah. I was not clear. I was envisioning 'reactionless' drives as using the hyperspace fluid as reaction mass. Essentially using hyperspace as an infinite capacity fuel tank.

You still have the same limits. It a rule that you cannot cheat without producing perpetual motion (which is bad if you want a setting that makes any sense).

Lets say the tank holds 1kg or fluid and expels the whole contents at 2m/s every second. That's 2J of energy moving the ship forward but it also means your engine requires at least 2W in order to operate continuously (because those 2J per second have to come from somewhere).

[Adina]

Originally Posted by lexington

You still have the same limits. It a rule that you cannot cheat without producing perpetual motion (which is bad if you want a setting that makes any sense).

FTL and reactionless thrusters ARE cheats. I'm trying to see what effects drop out of this particular cheat.

Lets say the tank holds 1kg or fluid and expels the whole contents at 2m/s every second. That's 2J of energy moving the ship forward but it also means your engine requires at least 2W in order to operate continuously (because those 2J per second have to come from somewhere).

Yes the engines require power. But given an unlimited amount of hyperspace fluid as reaction mass, why can't you accelerate continuously?

Maybe I'm tired, but I'm not seeing it.