[Spaceships]If Hyperspace is a fluid medium

[Langy]

Originally Posted by gjc8

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.

Ah - that's cool to know. As for why it's more efficient for heat transfer - convection is pretty much always better for heat transfer than radiation.

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.

Yeah - I considered that. There might be some things that use it - say, nuclear power plants - but I doubt that it'd be that common in most things, since it'd also be rather expensive.

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.

How much of a problem would this be? I'm guessing it'd put an upper limit on how long you can remain in hyperspace before you freeze to death unless you've got a reactor capable of churning out excessive amounts of heat, but how long do you think that'd be? Minutes, seconds, hours, days, weeks? I'd prefer it if big ships can last a few weeks in hyperspace without having too many reactors dedicated to just keeping the ship not-freezing.

[vicky_molokh]

Originally Posted by Langy

How much of a problem would this be? I'm guessing it'd put an upper limit on how long you can remain in hyperspace before you freeze to death unless you've got a reactor capable of churning out excessive amounts of heat, but how long do you think that'd be? Minutes, seconds, hours, days, weeks? I'd prefer it if big ships can last a few weeks in hyperspace without having too many reactors dedicated to just keeping the ship not-freezing.

It just means you risk freezing soon if the only thing separating a habitat and hyperspace is a chunk of metal. You need insulation, but that's pretty much it. Does the hyperspace fill vacuum that is inside the ship (e.g. vacuum used for insulation)?

[Langy]

Originally Posted by vicky_molokh

It just means you risk freezing soon if the only thing separating a habitat and hyperspace is a chunk of metal. You need insulation, but that's pretty much it. Does the hyperspace fill vacuum that is inside the ship (e.g. vacuum used for insulation)?

No, definitely not. Excellent - just need to make sure habitats are sealed up like a thermos:p

[Adina]

Got it now, apparently my brain went to bed before I did.

Originally Posted by Anthony

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).

Assumption clash here. I was thinking about RL drives as working like fusion drives, not air-breathing jets. Which I clearly did not communicate.

Also I am not sure how realspace velocity relates to hyperspace. Presumably hyper space is at a velocity well above c since ships in hyper space travel light-years in a matter of hours.

Originally Posted by Fred Brackin

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 hyperspace medium to get the energy to accelerate it you can't treat it like a rocket with infinite fuel.

So if RL drives work like jets then as velocity increases then acceleration decreases as they become inefficient.

But if the hyperspace medium is a fuel, that (for example) rapidly decays into suitable high velocity particles that can be shot out the back, then RL drives would work like a rocket with infinite fuel.

Jeff

[teviet]

Originally Posted by jmurrell

So if RL drives work like jets then as velocity increases then acceleration decreases as they become inefficient.

But if the hyperspace medium is a fuel, that (for example) rapidly decays into suitable high velocity particles that can be shot out the back, then RL drives would work like a rocket with infinite fuel.

In theory, yes, if your engine can convert the hypermedium "on the fly" at an arbitrarily high rate. Power requirement still increases proportional to speed, but your fuel is also coming to you at a higher rate, so you can increase your power production as high as necessary.

Some old-school SF with Bussard ramjets took advantage of this trick to achieve endless constant acceleration. But (in addition to the problems with protium-only fusion) one might question the premise of on-the-fly conversion with arbitrarily high power production. If you have to bring your fuel up to speed with your engine to convert it, then your ship speed will stagnate at the engine's effective exhaust speed.

TeV

[Adina]

Originally Posted by teviet

In theory, yes, if your engine can convert the hypermedium "on the fly" at an arbitrarily high rate. Power requirement still increases proportional to speed, but your fuel is also coming to you at a higher rate, so you can increase your power production as high as necessary.

Some old-school SF with Bussard ramjets took advantage of this trick to achieve endless constant acceleration. But (in addition to the problems with protium-only fusion) one might question the premise of on-the-fly conversion with arbitrarily high power production.

We're defining superscience so most of my premises are fiction. So one possible premise is that the hyperspace medium is unstable in realspace and decays into, say, equal amounts of electrons and positrons. Or whatever particles are usefully high energies.

If you have to bring your fuel up to speed with your engine to convert it, then your ship speed will stagnate at the engine's effective exhaust speed.

Isn't this true for any engine though?

Jeff.

[Anthony]

Originally Posted by jmurrell

Assumption clash here. I was thinking about RL drives as working like fusion drives, not air-breathing jets. Which I clearly did not communicate.

Possibly because that doesn't make any sense given your proposed setup. If you're pushing on the hyperspace medium, you've got a drive that functions like an air (or water) breathing engine.

Originally Posted by jmurrell

But if the hyperspace medium is a fuel, that (for example) rapidly decays into suitable high velocity particles that can be shot out the back, then RL drives would work like a rocket with infinite fuel.

In addition, cosmic power plants become routinely available, and you can probably blow up planets with hyperspace-rip bombs, making near-C rocks an incidental problem at best.

[Adina]

Originally Posted by Anthony

Possibly because that doesn't make any sense given your proposed setup. If you're pushing on the hyperspace medium, you've got a drive that functions like an air (or water) breathing engine.

Uhm, who said anything about pushing on the hyperspace medium?

In addition, cosmic power plants become routinely available, and you can probably blow up planets with hyperspace-rip bombs, making near-C rocks an incidental problem at best.

Problem, yes.

[Adina]

Also if there is a hyperspace medium then there can be wake detectors or sonar equivalents, at least for objects in hyperspace. And FTL communicators as well.

[Anthony]

Originally Posted by jmurrell

Uhm, who said anything about pushing on the hyperspace medium?

It's sort of implicit in the concept of a fluid medium...

Anyway, your latest proposal is a cosmic-powered photon drive. With a power output of 3 terawatts per ton of thrust. Use the Cosmic Power rules (SS31), applying Cosmic twice (i.e. x1,000,000 energy, x100 damage/DR) and then use reactionless thrusters.