[Spaceships]If Hyperspace is a fluid medium

[Adina]

I have been thinking about building spaceships for a TL10 setting. I have decided that hyperspace and reactionless thrusters exist and was thinking about appropriate techno-babble.

Both stardrives and reactionless thrusters require a vehicle minimum mass greater than 300 tons, i.e. SM+8 or larger. They are also gravity limited, they can get you in and out of orbit but surface/orbit transfers need fusion torches or other reaction drives.

So it occurred to me that if hyperspace is filled with some type of fluid medium (ether?) it could explain a couple of things.

1) Drag from this medium explains why FTL drives have a top speed rather than an acceleration.

2) "Reactionless" actually use this hyperspace fluid as reaction mass.

Some questions for speculation:

Would reactionless drives be pseudovelocity?

Would their acceleration be felt by the occupants?

If hyperspace + normal-space are a closed system could the various conservation laws remain valid? Would this require a transfer of energy/momentum between hyper and normal space?

What other effects fall out of this setup?

Jeff

[Diomedes]

Originally Posted by jmurrell

1) Drag from this medium explains why FTL drives have a top speed rather than an acceleration.

Presumably drives would still have an acceleration, determining how fast you reach top speed.

Originally Posted by jmurrell

2) "Reactionless" actually use this hyperspace fluid as reaction mass.

That's basically how the Hyperdynamic Field switch works in SS7.

Originally Posted by jmurrell

Some questions for speculation:

Would reactionless drives be pseudovelocity?

Would their acceleration be felt by the occupants?

No and yes, respectively. With a normal drive the crew feels acceleration because the engines push on the ship, which pushes on the occupants. If you distributed the force throughout the ship (say, by generating a gravity well and falling into it) then there would be no felt acceleration.

Originally Posted by jmurrell

If hyperspace + normal-space are a closed system could the various conservation laws remain valid? Would this require a transfer of energy/momentum between hyper and normal space?

That might be necessary.

[Anthony]

Originally Posted by jmurrell

Would reactionless drives be pseudovelocity?

Depends how they work. From that description, probably not (sublight warp drives are a standard type of PV drive, but don't seem to be what you're talking about).

Originally Posted by jmurrell

Would their acceleration be felt by the occupants?

Probably.

Originally Posted by jmurrell

If hyperspace + normal-space are a closed system could the various conservation laws remain valid?

Well, hyperspace fluid has properties that are problematic for relativity, and energy requirements for your drives would tend to be unreasonably high.

Originally Posted by jmurrell

Would this require a transfer of energy/momentum between hyper and normal space?

Yes.

[vicky_molokh]

How do reactionless drives work in TrueSpace?

Closed system in terms of energy is probably best, unless you have some sort of Subspace e.g. for dumping waste heat and running cloaking devices.

As for relativity, you'll have to alter it one way or another. I suggest you find (and optionally resurrect) my thread of questions and ideas about ways to ditch relativity with minimal collateral damage to the rest of physics.

[Adina]

1) Drag from this medium explains why FTL drives have a top speed rather than an acceleration.

Originally Posted by Diomedes

Presumably drives would still have an acceleration, determining how fast you reach top speed.

True, but all I really need is how long it takes to travel from system A to system B.

2) "Reactionless" actually use this hyperspace fluid as reaction mass.

That's basically how the Hyperdynamic Field switch works in SS7.

Ah, yet another reason for me to acquire SS7.

Would reactionless drives be pseudovelocity?

Would their acceleration be felt by the occupants?

No and yes, respectively. With a normal drive the crew feels acceleration because the engines push on the ship, which pushes on the occupants.

Originally Posted by Anthony

Depends how they work. From that description, probably not (sublight warp drives are a standard type of PV drive, but don't seem to be what you're talking about).

Probably.

That's what I was thinking. So I need to consider how high a thrust a human crew can sustain because accelerations up to 6 g's are possible. And I need to consider near-c rocks as well. Perhaps there is a maximum mass that reactionless thrusters can propel above which the vehicles own gravity disrupts them. SM+13 is 300,000 tons, at near-c velocity is that a city-killer, an extinction event, or a planet-cracker?

If hyperspace + normal-space are a closed system could the various conservation laws remain valid?

Well, hyperspace fluid has properties that are problematic for relativity, and energy requirements for your drives would tend to be unreasonably high.

Any FTL is problematic for relativity, what particular problems does hyperspace fluid cause?

Would this require a transfer of energy/momentum between hyper and normal space?

That might be necessary.

Yes.

Ok, what if I postulate that black holes and quasars are transfer points between normal space and hyperspace. What problems and possibilities does that create?

[Anthony]

Originally Posted by jmurrell

That's what I was thinking. So I need to consider how high a thrust a human crew can sustain because accelerations up to 6 g's are possible.

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

Originally Posted by jmurrell

And I need to consider near-c rocks as well. Perhaps there is a maximum mass that reactionless thrusters can propel above which the vehicles own gravity disrupts them. SM+13 is 300,000 tons, at near-c velocity is that a city-killer, an extinction event, or a planet-cracker?

Depends how near to C you are. 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...).

Originally Posted by jmurrell

Ok, what if I postulate that black holes and quasars are transfer points between normal space and hyperspace. What problems and possibilities does that create?

Well, it sort of implies the creation of artificial black holes, assuming hyperspace drives are actually useful.

[ericbsmith]

Originally Posted by Anthony

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

Fit humans could probably manage 1.25 to 1.5G in the long term. However, in any universe with engines which can sustain 6G indefinitely I'd expect that gravitic technology would be good enough to generate artificial gravity that can cancel out those high accelerations.

[Fred Brackin]

Originally Posted by jmurrell

[I]1) . SM+13 is 300,000 tons, at near-c velocity is that a city-killer, an extinction event, or a planet-cracker?

It's between extinction event and planet cracker based on velocity. To cross over with the crach lnading thread, 1000x a jumbo jet (or 3x an aircraft carrier) is a city killer at the 0.1miles per second of a bad landing.

Literally cracking a planet is hard when your impactor is going to flash explode at the first breath of atmosphere. However, you can fairly easily get to the point where the radiation flash not only sterilizes a hemisphere but blows off a large fraction of the atmosphere and renders the place uninhabitable that way;.

[teviet]

Originally Posted by jmurrell

SM+13 is 300,000 tons, at near-c velocity is that a city-killer, an extinction event, or a planet-cracker?

If "near c" means kinetic energy comparable to rest energy, then it's about the same as an asteroid a few tens of kilometers across hitting the Earth at ordinary orbital speeds. Thus, an extinction event.

If you're hyperrelativistic (really close to c), the explosion could be arbitrarily large.

TeV

[vicky_molokh]

For a game, collision rules might be good enough - 186,000 mps is pretty near c, multiply that by 6d by 3 by HP/ST (use dHP/dST for dDamage). Just make that explosive damage.