[Spaceships]If Hyperspace is a fluid medium

[lexington]

Originally Posted by jmurrell

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.

You cannot produce an infinite amount of energy without having an infinite amount of mass because they're the same thing. When you burn a log a tiny amount of its mass turns into photons that you experience as heat and light, the same rule applies to everything.

[Adina]

Originally Posted by lexington

You cannot produce an infinite amount of energy without having an infinite amount of mass because they're the same thing. When you burn a log a tiny amount of its mass turns into photons that you experience as heat and light, the same rule applies to everything.

An infinite amount of mass IS what I am postulating though. Assume relativity and the laws of physics are incomplete. Assume FTL and thrusters using an infinite supply of hyperspce fluid exist. Assume hyperspace plus normal space form a closed system. Given these assumptions what other effects could there be.

For example if engines are pulling mass out of hyperspace into normal space what counter-balances this increase in mass? Does the mass that fall into black holes go into hyperspace?

[lexington]

Originally Posted by jmurrell

An infinite amount of mass IS what I am postulating though. Assume relativity and the laws of physics are incomplete. Assume FTL and thrusters using an infinite supply of hyperspce fluid exist. Assume hyperspace plus normal space form a closed system. Given these assumptions what other effects could there be.

For example if engines are pulling mass out of hyperspace into normal space what counter-balances this increase in mass? Does the mass that fall into black holes go into hyperspace?

Its fine to have an infinite amount of remass available. The problem is that energy you use the accelerate it is still going to be finite unless you add a miraculous source of infinite amounts of heat/electricity. Even if your ships get remass for free they can't accelerate it out the back for free.

At least they shouldn't be able to. If they can you'll end up with a setting that makes The Culture look tame by comparison.

[Anthony]

Originally Posted by jmurrell

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

It applies to reaction drives -- based on the exhaust velocity of the propellant. Most reaction drives have very high specific power.

[Anthony]

Originally Posted by jmurrell

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

You can. Just at incredibly low acceleration if your velocity relative to hyperspace is high (a reaction drive's velocity relative to its fuel tank is always zero; an air-breathing engine, which is the equivalent to what you're talking about, has energy cost that goes up as your speed increases).

[teviet]

To expand on what Anthony said: With a rocket, you carry your reaction mass with you. That takes a lot of work up front. But because it's now moving along with you, you can impart a lot of momentum to it with comparatively little expenditure of energy. That is, a given power produces a given thrust regardless of how fast you're moving relative to anything else.

When using an external medium, you don't need to bring that medium up to speed in order to push off against it. But that means it's already moving very quickly past you, and a given amount of energy produces very little change in momentum. That is, a given power produces diminishing thrust as your speed increases.

TeV

[Fred Brackin]

Originally Posted by jmurrell

An infinite amount of mass IS what I am postulating though.

That's okay but you're hitting a problem with the enrgy to accelerate that mass. Many reactionlerss drives not only produce thrust without usiing mass, they also produce more thrust than they can pay for from theri energy sources. Traveller is like this.

Disregarding reaction mass it still requires an amount of energy to acclerate an object to near lightspeed equal to the mass of that object i.e. an object at near c has a kinetic energy more or less equal to its' own mass. C is the place where the kinetic energy equation and the e=mc squared equation meet.

Rocket fuel has the useful property of being first an energy source and then reaction mass. If you aren't burning hypersdpace medium to get the energy to accelerate it you can't treat it like a rocket with infinite fuel.

[Langy]

I've been considering this scenario as well for my own setting, though it wasn't going to use hyperspace's fluid medium for re-mass - it was going to use it as an impossibly giant and efficient heatsink, with the hyperspace fluid being naturally extremely cold. It'd also confound sensors a hell of a lot, at least compared to normal space, getting you a hyperspace that behaves a lot like that of Babylon 5 (navigation's a pain, it's easy to get lost, and you can't see anything a few thousand miles in any direction).

Can you think of any problems there'd be with hyperspace heatsinks? Would they necessarily create perpetual motion machines/etc? I'm assuming there'd be a 'friction' force associated with bringing the hyperspace medium up to ship speed like there is with using the hyperspace medium as re-mass, but I'd think it'd be significantly less powerful than the re-mass one, since I doubt you'd need anywhere near as much coolant as you do re-mass.

[vicky_molokh]

You must decide how heat-conductive hyperspace is. Too little, and it works like vacuum, but too much and it will cool a spaceship very, very fast, up to the heat-conductive limit of the outer hull.

[gjc8]

Originally Posted by Langy

Can you think of any problems there'd be with hyperspace heatsinks? Would they necessarily create perpetual motion machines/etc?

If it's at a different temperature than cosmic microwave background, I think you end up with a perpetual motion machine, albeit potentially a very slow and inefficient one. You can avoid that by having it be at the same temperature, but much more efficient for heat transfer for whatever reason.

One thing to consider: having a big, cold heatsink is useful for more than just spaceships. Even in on planets, etc, hyperspace may be a better heatsink, since CMB is very cold.