Hypothetical effects of the hypothetical Alcubierre drive

[Cmdr. Arn1e]

One could launch such a spacecraft from Earth in one piece, as long as it is small enough. The limits would be on how small the Alcubierre drive could be downscaled, and whether there are launch vehicles able to launch the resulting contraption.

true, or it could be launched empty and stocked once it is in orbit...

Once the van Allen belt and GEO ring is cleared, firing the AD itself shouldn't be much of a problem, other than finding out how to steer the thing from outside the warp bubble.

The steering is the hardest part from what I've just read on wikipedia... anyone trying to control it would be inside the bubble, making it harder still... this is due to how we don't have FTL communications to control it externally, not over any sizable distance at least... and it is not known if communication is even possible between the inside and outside of the bubble...

Think OP should add 'required reading' and link to the Wikipedia Page, I certainly learnt a bit more! Mr White is mentioned a couple of times, and there are even counter-arguments mentioned in the article by Miguel Alcubierre himself heh...

[shynung]

true, or it could be launched empty and stocked once it is in orbit...

Depends on the actual vehicle in question. If it's just a space probe the size of a military spy satellite (they were bigger for containing their acute sensors and cameras, for obvious reasons), a typical Delta/Titan/Proton rocket could loft it merrily. The problem comes when it's manned, or carry things like landers.

The steering is the hardest part from what I've just read on wikipedia... anyone trying to control it would be inside the bubble, making it harder still... this is due to how we don't have FTL communications to control it externally, not over any sizable distance at least... and it is not known if communication is even possible between the inside and outside of the bubble...

This is if the AD was to go superluminal (FTL). If it were to go sub-light, it might be able send radio signals through the bubble sections where the warping effect is at its minimum. How much of the signal remains intelligible, however, is a different story entirely.

[Cmdr. Arn1e]

This is if the AD was to go superluminal (FTL). If it were to go sub-light, it might be able send radio signals through the bubble sections where the warping effect is at its minimum. How much of the signal remains intelligible, however, is a different story entirely.

mmm, very god point... after all, it is speculated that plenty of particles that could pass through/get trapped/be absorbed/released at different rates (probably depending on the nature of the particle) on the journey to wherever, so it is highly possible that waves would be able to pas through... maybe...

The big problem comes when factoring the speed differences - pretty sure waves (light, sound, electromagnetic) move at different speeds at different wavelengths, and so would have an effect on how useful it would be to use the different types, probably for different situations... as I said previously, we currently have no way of communicating at even close to the high-sub-light speeds, and especially not any way of comunicating at light or above-light speeds (otherwise we'd have very fast networks and almost unlimited bandwidth already... heh, we can dream!).

I'm gonna make this my last reply for a while, as I feel I've jumped in and started thread-hogging lol! sure plenty of others have their own ideas and links to relevant info...

[Excalibur]

OP, have you tried the KSP Interstellar mod? http://forum.kerbalspaceprogram.com/threads/43839-0-23-5-KSP-Interstellar-(Toolbar-Integration-New-Models-New-Tech)-Version-0-11

This mod has it's own Alcubierre drive and it's mechanics illustrate how such a drive would potentially work reasonably well.

You are creating a space-time warp bubble around your ship; your ship does not move relative to the space-time which it is resting upon, rather the space-time itself is 'moved' (an over-simplification).

Imagine a toy car driving along a massive tablecloth. It has a velocity of 1m/s North. You can simulate the principle of a warp drive by moving the table cloth and whatever direction you move the tablecloth 'spacetime' in the car will still be doing 1m/s North. In other words, momentum is conserved.

Applying this reasoning to your scenario we can see that what happens to your spacecraft depends really on how far you move it using the Alcubierre drive. The important thing to consider is it's velocity vector relative to the star will not change, only it's distance. Warp a small distance retrograde as you describe and you will end up in an eccentric orbit, warping much further away retrograde and you'll likely be in a hyperbolic escape orbit upon warp exit.

As I initially pointed out KSP Interstellar illustrates this beautifully. With skillful warping you can actually perform planetary rendezvous with barely any delta-v expenditure, simply warp as close to the planet as possible (without actually hitting it - that's a bad day) and as long as your velocity vector upon leaving warp is directly away from the planet the planet's gravity will slow you down. Rinse and repeat as needed.

[Garek]

pretty sure waves (light, sound, electromagnetic) move at different speeds at different wavelengths

Actually, light is an electromagnetic wave, and (in vacum) all electromagnetic waves travel with lightspeed. And I think soundwaves have a similar fixed speed depending on the medium. What actually happens if you recieve a transmission from an object moving away from you is that you recieve that as a longer wavlength as it was send. The effect is of course reversed if the sender moves towards you. If I'm not mistaken, this effect is known as Doppler Shift. You can actually hear the Doppler shift of the sound from a car driving past you - it sounds higher when approaching then when it drives away. With electromagnetic waves, it is often called red-shift and blue-shift respectively, because 'white' light would be shiftet towards red if the source is moving away and blue if the source is moving towards you. But of course, it's only that simple if the space between sender and reciever isn't so much distortet as with an AD. I have no idea what an AD would do to electromagnetic waves.

Bandwith on a network is limited not by the speed of signals (they move always approx. with lightspeed), but by certain technical/physical limitations on how short a signal on a certain medium can be. And how many tricks are used to get around those limitations.

[peadar1987]

So... Can someone with an idea of the physics behind the drive tell me if there would be an "ideal time" to fire up your AD. Say you were in orbit around the earth and wanted to go to Mars. Would it be better to start your AD with the earth and Mars in conjunction, and with your ship on the portion of its orbit where its velocity was opposite to the orbital direction of the earth, seeing as the earth moves faster than Mars and therefore you want to shed as much of your velocity as possible to minimise delta-V to enter a stable orbit once you get there.

[Aethon]

This is a fun topic. It's so hypothetical, no question is stupid and no answer is wrong. :^)

So... Can someone with an idea of the physics behind the drive tell me if there would be an "ideal time" to fire up your AD.

I'm not that guy, but I would guess this: you would wait until your tangential velocity vector aimed towards Mars and then engage your drive. Basically point and shoot.

I suppose I'll mention the elephant in the room, this 'ring of negative energy density'.

Dr. White in the vid., mentions something about using air(?) on his test table. As I understand it we're talking about using unobtanium here. Warp drive requires a ring of matter, the mass of which would be repulsive, as opposed to the attractive mass of 'normal matter'. Now I did a quick E bay search and found nothing like this. Any ideas on this magic stuff and how to get it?

"3. Any sufficiently advanced technology is indistinguishable from magic." Arthur C. Clarke

Edited June 16, 2014 by Aethon

[rtxoff]

OP, have you tried the KSP Interstellar mod? http://forum.kerbalspaceprogram.com/threads/43839-0-23-5-KSP-Interstellar-(Toolbar-Integration-New-Models-New-Tech)-Version-0-11

This mod has it's own Alcubierre drive and it's mechanics illustrate how such a drive would potentially work reasonably well.

I have this mod, and i was thrown into thinking when people mentioned Interstellar does not simulate it very well. I thought about that matter and i concluded for myself that indeed something can not be right with the way Interstellar simulates it. It may be better then a bunch of other warp drive mods but it does not reflect the way an real warp drive would be. First of oll if you activate your AD in interstellar you instantly get accelerated with the predefined speed setting towards the direction your ship is facing. This is fundamental wrong. You won't get accelerated by an AD. The only thing the AD is capable of doing is to shorten you flight path and reduce the time you need to get somewhere. Your ship already needs to have some speed relative to your target to get moving. Activating the AD alone won't get you anywhere. The next questions that comes up, is the ship able to accelerate while the AD is active. I guess this is something particle theoreticians have to find out because i for myself can't imagine what is going to happen if i fire my rocket and the exhaust gases are hitting the expanded spacetime in the warp field behind me. So you can imagine how an real warp drive would feel like, all you need is stock KSP. Start your travel to some other planet by doing an burn and when on the right track activate time warp. Just imagine that the time in the upper left corner runs with it's normal speed but your ship travels very fast towards the target. Thats how the hypothetical AD will behave.

[K^2]

So... Can someone with an idea of the physics behind the drive tell me if there would be an "ideal time" to fire up your AD. Say you were in orbit around the earth and wanted to go to Mars.

Earth passing by Mars. You want to fire up your reaction engines and get roughly up to escape velocity. You probably want to wait until you are far enough from Earth to not be a hazard to any satellites as well. Then you fire up warp and go on an almost straight line trajectory from Earth to Mars, where you will drop out and star breaking heard with reactions to assist the capture. You'll probably end up wasting almost as much reaction fuel as you would with classical transfer, but you'll get there much faster.

There might be some advantages to Earth or Mars being slightly ahead along the orbit, but likely not too much. You definitely don't want them to be in completely different places with respect to Sun. It'd both make for a longer travel and make it way harder on your propulsion.

[SolarLiner]

Earth passing by Mars. You want to fire up your reaction engines and get roughly up to escape velocity. You probably want to wait until you are far enough from Earth to not be a hazard to any satellites as well. Then you fire up warp and go on an almost straight line trajectory from Earth to Mars, where you will drop out and star breaking heard with reactions to assist the capture. You'll probably end up wasting almost as much reaction fuel as you would with classical transfer, but you'll get there much faster.

There might be some advantages to Earth or Mars being slightly ahead along the orbit, but likely not too much. You definitely don't want them to be in completely different places with respect to Sun. It'd both make for a longer travel and make it way harder on your propulsion.

Yes, but no. That method is way to scifi-y. An AD only wraps space and time, it does not offer you a unlimited fuel option. Using an Alcubierre Drive would shorten the Earth -> Mars trip, but in no way the ship will go in a "fire up and go straight line" if the motors are not of some kind of futuristic mega-energetic propulsion, you will not be able to do that. And still the most efficient trajectory is the HTO.

For intra-solar system journeys, the AD would greatly reduce the time of the voyage.

This brings another problem: if a voyage to Jupiter takes 4 years realtime, but only 4 days using the AD, the astronauts will return only 22 days older (counting a 2-week stay+all orbital maneuvers), instead of 8 years older.

So, how does the two "time clocks" kinda "re-sync" together? Or does they? Would this make the ultimate "stay young, go fast" machine?

[rtxoff]

This brings another problem: if a voyage to Jupiter takes 4 years realtime, but only 4 days using the AD, the astronauts will return only 22 days older (counting a 2-week stay+all orbital maneuvers), instead of 8 years older.

So, how does the two "time clocks" kinda "re-sync" together? Or does they? Would this make the ultimate "stay young, go fast" machine?

You have a flaw in this logic. As you already said, the journey will take 22 days with the AD. Why should they be 8 years older after it. For the traveller in an AD ship time will pass at almost the same rate as on earth. Not faster or slower at least not much.

[K^2]

Yes, but no. That method is way to scifi-y. An AD only wraps space and time, it does not offer you a unlimited fuel option. Using an Alcubierre Drive would shorten the Earth -> Mars trip, but in no way the ship will go in a "fire up and go straight line" if the motors are not of some kind of futuristic mega-energetic propulsion, you will not be able to do that. And still the most efficient trajectory is the HTO.

For intra-solar system journeys, the AD would greatly reduce the time of the voyage.

AD has NOTHING to do with your engines. The only reason you need to burn fuel is to make sure your velocity relative to target isn't too high. And yes, it will bring you along an (almost) straight line without needing to expend any fuel. I suggest you read up on the subject.

This brings another problem: if a voyage to Jupiter takes 4 years realtime, but only 4 days using the AD, the astronauts will return only 22 days older (counting a 2-week stay+all orbital maneuvers), instead of 8 years older.

So, how does the two "time clocks" kinda "re-sync" together? Or does they? Would this make the ultimate "stay young, go fast" machine?

And you seem to be extra confused on this part. Travel with Alcubierre Drive is actually faster. Not just takes less time from perspective of the ship. When a warp ship travels faster than light, it's actually going faster than light. With an Alcubierre Drive you can do a round trip to Alpha Centauri and be back before eight years pass on Earth.

Sub-light warp within the system works the same way. You actually get to destination faster. Not just by ship's clock, but by everyone's.

[peadar1987]

Earth passing by Mars. You want to fire up your reaction engines and get roughly up to escape velocity. You probably want to wait until you are far enough from Earth to not be a hazard to any satellites as well. Then you fire up warp and go on an almost straight line trajectory from Earth to Mars, where you will drop out and star breaking heard with reactions to assist the capture. You'll probably end up wasting almost as much reaction fuel as you would with classical transfer, but you'll get there much faster.

There might be some advantages to Earth or Mars being slightly ahead along the orbit, but likely not too much. You definitely don't want them to be in completely different places with respect to Sun. It'd both make for a longer travel and make it way harder on your propulsion.

Okay, so you don't have to put yourself on a Mars transfer orbit or anything?

If there were no issues with satellites or anything, what would happen if you turned on your AD while simply orbiting the earth? Would you continue to orbit the earth, just really fast? Or do you have some measure of control over the warp bubble (it's not just analogous to a ballistic trajectory that you drop off at some point)?

Sorry for all the questions!

[phoenix_ca]

I'd wager the first trip to Alpha Centauri is done in way less time than that. Say with a drive going at at least 3-4C, preferably 8C or more so it takes under a year.

Not that I'll live to see it.

[rtxoff]

Okay, so you don't have to put yourself on a Mars transfer orbit or anything?

If there were no issues with satellites or anything, what would happen if you turned on your AD while simply orbiting the earth? Would you continue to orbit the earth, just really fast? Or do you have some measure of control over the warp bubble (it's not just analogous to a ballistic trajectory that you drop off at some point)?

Sorry for all the questions!

Well this are some really good questions. IMO the easiest way would be to conventionally burn into mars transfer orbit and after that when get enough distance to earth activate the AD and deactivate it shortly before entering Mars SOI.

However if i am going to speculate what would happen if the ship activate it's AD while orbiting earth it would depend in which direction the ship is faced to.

Assuming that the ship is faced prograde and that it is able to hold that prograde direction with reaction wheels it would most probably start to orbit Earth at an higher rate. Now if you turn that ship to look away from earth and activate the AD i guess it would depend on the orbiting altitude and the strengh of the warp field. The question here is how far does the warp field extend infront and back to the ship. However it should have the same effect as suddenly increasing your orbiting altitude but orbiting speed stay the same. If the warp effect is strong enough you could probably leave earth SOI with this trick?

I don't know.

[Cmdr. Arn1e]

If the warp effect is strong enough you could probably leave earth SOI with this trick?

Absolutely correct, because

Your ship already needs to have some speed relative to your target to get moving.

is actually wrong... I suggest you go read the wiki page on the drive, as I linked earlier...

The ship is partly pushed, partly pulled along by the fields created by the AD; the 'problem' of requiring huge amounts of mass to get the ship/drive anywhere has been reduced over the course of the research/theoretical work so far (it has been theorised that a full warp 'bubble' would take more mass than is available in the known universe! this was reduced when another scientist came along and worked out a way of reducing this amount by changing the waveform or something, but not to within usable levels. White has worked out that if it is reduced further, into an off-plane 'ring', or 'doughnut' then the mass is reduced to very small, obtainable amounts that we could work with.)

I'll just link the wiki again, to be sure: http://en.wikipedia.org/wiki/Alcubierre_drive

Also, this is the reson for the update of the mock-up design; it wasn't that it was too thin for the forces it would have to endure, but because of the mass it requires for the drive to work - think about a sailing ship; does it work better when the sails are made out of netting, or more 'solid' cloth?

[rtxoff]

The ship is partly pushed, partly pulled along by the fields created by the AD.

Well no matter what wikipedia writes i have really a problem with this sentence. It tempt's you to think that the ship is building up some speed with the AD which is wrong.

Your initial speed is not changing with an AD. The only variables you are going to manipulate with it is distance/time not your movement speed. If you are not already travelling towards an target it is not going to magically accelerate you towards it. However by skillfully aligning you warp field you could eventually leave SOI and get you going in to the right direction. This however will require some sophisticated navigation skills/computers, it's not going to be like point at your target and fire the AD.

There's no doubt this could be also wrong, all this is hypothetical.

[K^2]

Well no matter what wikipedia writes i have really a problem with this sentence. It tempt's you to think that the ship is building up some speed with the AD which is wrong.

Your initial speed is not changing with an AD. The only variables you are going to manipulate with it is distance/time not your movement speed.

That is actually completely wrong. If it makes it easier for you to think of it this way, you can picture the ship as always moving, but mostly through time. Alcubierre Drive boosts the coordinate system of the ship, so its movement through time ends up being motion through space as well. In other words, ship can be totally static to begin with, and still pick up speed via AD.

Otherwise, you'd end up with a contradiction. If the ship had to be moving to activate warp, what would the observer see that's moving at the same speed as the ship? Relativity is all relative. What works in one frame of reference has to work in all the others as well. If a moving ship can use warp, so can a static one, and vice versa.

Now, when you have a source of gravity, things do get a bit more interesting, but unless you are trying to use FTL Warp to go through a black hole, it's not that much more interesting. Just some extra complications in terms of how your pre-warp velocity relates to your post-warp velocity.

Okay, so you don't have to put yourself on a Mars transfer orbit or anything?

If there were no issues with satellites or anything, what would happen if you turned on your AD while simply orbiting the earth? Would you continue to orbit the earth, just really fast? Or do you have some measure of control over the warp bubble (it's not just analogous to a ballistic trajectory that you drop off at some point)?

You actually have total control over your trajectory during warp. Some might be more energy-efficient than others, and there could be issues with radiation when bubble accelerates, but otherwise, strictly speaking, you could be flying around in zig-zags without the ship itself ever experiencing acceleration. And if the space-time around was completely flat, it wouldn't have any effect on ship's final speed, either.

So in terms of warp bubble itself, there are no problems just leaving earth orbit using warp. However, Earth's gravity is still going to affect the ship and accelerate the ship. It's a very indirect effect, because the space-time inside the bubble is flat, and so gravity's effect is actually on the bubble, which will cause the bubble to shift, which will require you to correct for, which will end up changing the exit velocity of the ship as if the ship was being affected by gravity. But then you're not taking a ballistic trajectory, so the effects of gravity will not be exactly the same as just gravitational force acting on the ship.

I don't know what will happen to the ship if warp takes it out of the system that it didn't have velocity to escape, though. That's an interesting question. I think I'll have to run a simulation on that and see if there is an inherent problem. Might not be. Strictly speaking, energy need not be conserved, since you might be supplying energy via the warp bubble. On the other hand, momentum should be conserved. Otherwise, it's a gravitational wave drive, which is probably the least energy-efficient method of propulsion in existence. You definitely would want to avoid that.

Edited June 15, 2014 by K^2

[rtxoff]

In other words, ship can be totally static to begin with

Well, static towards what? What do you take as you reference point to be static towards? Static against sun would mean 0m/s orbiting speed which leads you to accelerating towards the sun by gravity. I claim that in this case even the AD could not save you anymore, you could however greatly decrease or increase the time before your death while activating your AD facing to or away from the sun.

Otherwise, you'd end up with a contradiction. If the ship had to be moving to activate warp, what would the observer see that's moving at the same speed as the ship? Relativity is all relative. What works in one frame of reference has to work in all the others as well. If a moving ship can use warp, so can a static one, and vice versa.

I never said you had to be moving to activate the AD. The only thing i am saying is that activating the AD will probably not have the effect you desire if you are not already moving towards an target while facing it.

If u assume two ships 2km side by side travelling towards some planet one with AD and one without. The one without will observe the other which is activating the AD, it will see it accelerating toward it's destination. This will happen not because it is faster. It will happen because the ship with the AD is greatly compressing the spacetime between it and the destination. Can't really see an contradiction here.

The thing is to produce a certain effect with an AD you have to be very aware what exactly it will do at the point you activate it.

[Cmdr. Arn1e]

The thing is, the bubble/ring/doughnut (whatever shape you make the warp field) is the thing that is moving, and taking whatever is inside it along with it - but it is moving in time, not space, and it will take whatever is in the field with it, including the light particles (which gets confusing again, because light is both particles AND waves [more quantum mechanics - http://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality]).

Also, absolutely 'static' to me would be to halt ALL movement, and you would watch the sun and planets spin away very quickly as they themselves are moving at "20 kilometers per second or 12 miles per second. Or in units "per hour": 72,000 kilometers per hour or 45,000 miles per hour. This speed is in a frame of rest if the other stars were all standing still." (taken from here)

Further, "The Sun is moving upwards, out of the plane of the Milky Way, at a speed of 7 kilometers per second. Currently the Sun lies 50 light-years above the mid-plane of the galaxy, and its motion is steadily carrying it further away."

so for an normal drive to work, you would have to point it at where the target is going to be, not where it was... but this is opposite with an AD drive, as you might need to aim at where it was instead, due to the time-dilation effects of the drive itself...

[rtxoff]

Also, absolutely 'static' to me would be to halt ALL movement, and you would watch the sun and planets spin away very quickly as they themselves are moving at "20 kilometers per second or 12 miles per second. Or in units "per hour": 72,000 kilometers per hour or 45,000 miles per hour. This speed is in a frame of rest if the other stars were all standing still." (taken from here)

Even then you might be moving. What if the Universe itself is moving? You may then have haltet all movement relative to the center of the Universe. But there would be no way to tell if Universe itself is moving or not cause there might be a possibility that there are more universes. However in this case the term universe would not fit anymore.

[Cmdr. Arn1e]

I think 'Multiverse' would cover that - as in a 'Mulitverse of Universes'... and theoretically, they are all moving relative to each other... only way to be certain would be to measure speed locally against the surrounding atoms/molecules, but even they could be moving on solar winds, so I have to agree, there is no possibly way of knowing 100% if yo are totally 'static'... taken into account at the end of the bit you quoted me on with "if the other stars were all standing still." which they aren't, as we are fully aware!

But the only way we can prove all of this is to come up with a really good quantum theory, which we have an incomplete version at this time, due to forces which we don't understand still messing things up from time to time, randomly... like how black holes actually work... which we could find out if some of the speculation about the AD prove true! (Creation of a 'naked' black hole at one of the poles of the warp bubble/ring/doughnut - meaning it would form and be observable, we so far haven't been able to directly observe a black hole due to the even horizon, but it is speculated that it should be observable in the short time between it forming and starting to suck in everything around it such as light... but, of course, very dangerous for a ship equipped with an AD drive and its occupants!)

[shynung]

Even then you might be moving. What if the Universe itself is moving? You may then have haltet all movement relative to the center of the Universe. But there would be no way to tell if Universe itself is moving or not cause there might be a possibility that there are more universes. However in this case the term universe would not fit anymore.

This elegantly implies that the initial velocity of the ship, whether seen from a co-orbiting ship next to it or from a planet it is orbiting (or practically anywhere else), is irrelevant to the expected effects of the AD. As long as the surroundings are clear, all the ship has to do when it wants to 'warp' is to fire the AD, and it will see itself being moved to whatever it is pointing at.

Edited June 15, 2014 by shynung

[Aethon]

A couple of things I'd like to point out. IRL Earth's 'sphere of influence' is infinite and can never really be escaped. Relativity says nothing can go faster than the speed of light, and the AD won't violate that.

Think of a submarine, which doesn't carry a substance to 'exhaust' out the back. It is embedded in its propellant and uses the fluid around it (water) to move through space. In my visualization of this, the AD uses space and time as a sort of propulsive fluid. The AD latches on to space/time, 'piling' (expanding) it up behind the ship ( while stretching [contracting] space out in front, in a sense, shortening the distance traveled through space and time ). The ship then 'surfs' along on this wave.

I don't think it matters which way you 'point' the ship, what's important is the velocity vector of the craft when the AD is engaged ( tee hee. I can't believe we're far enough into the future to seriously discuss this.... Make it so! :^)

Basically we're talking about an inertia-less (space) time machine.

Edited June 15, 2014 by Aethon

[Aethon]

Even then you might be moving. What if the Universe itself is moving?

K. Remember, all motion is relative to something. There is no 'center of the universe' (probably) to judge motion relative to. When the drive comes on, you have the motion of the solar system, the galaxies motion all built in.... Whoa having a logic problem here that may change all this... must be dividing by zero in my brain. Lemme think brb.