Hypothetical effects of the hypothetical Alcubierre drive

[rtxoff]

This thread should be some theoretical discuss about the Alcubierre drive in the following abbreviated as AD.

My first question about it is: "If an spaceship orbiting the Sun (100.000.000km stable) decides to activate it's AD in retrograde vector with the same strength as it's current speed, will it stop? And if, will it fall into the sun?"

[xcorps]

It is my limited understanding that there will be no change in velocity, and it won't fall into the sun.

[Guest]

It's velocity in respect to the Sun won't change , however assuming you're pointing retrograde and 'blast' if you will, you should go that distance that way.

[rtxoff]

Well as far as i know there's nothing you can "blast" with the AD. What happens if you bend space only that much to counter your orbit speed.

Is this possible at all? I assume you will get pulled towards the sun as soon as this happens. If u add some counter vector against gravity is it possible to stop your ship completely?

[vger]

Well as far as i know there's nothing you can "blast" with the AD. What happens if you bend space only that much to counter your orbit speed.

Is this possible at all? I assume you will get pulled towards the sun as soon as this happens. If u add some counter vector against gravity is it possible to stop your ship completely?

That gets really hard to think about once you're looking at it relatively. In my mind, anyway, the closest you can get to "stopping completely" is geosynchronous orbit, and that can be done without burning or AD'ing constantly. Complete stop compared to what?

I guess in terms of Earth it would be simple enough. Blast of straight up, engage the AD just enough to counter gravity, and you'd just sit there while the Earth spins below you.

[rtxoff]

That gets really hard to think about once you're looking at it relatively. In my mind, anyway, the closest you can get to "stopping completely" is geosynchronous orbit, and that can be done without burning or AD'ing constantly. Complete stop compared to what?

To the sun. I assumed that obvious. In geosynchronous orbit you still have some orbital speed to counter the gravity but yeah something similliar like that.

Can it be done with an AD?

Edit: It's not that important for me what you take as reference for your stop, only if it would be possible to realise with an AD. So for example have an GO at any altitude you want.

Edited June 12, 2014 by gpisic

[Albert VDS]

My first question about it is: "If an spaceship orbiting the Sun (100.000.000km stable) decides to activate it's AD in retrograde vector with the same strength as it's current speed, will it stop? And if, will it fall into the sun?"

An AD spaceship doesn't have any speed, the warp bubble around it pushes the spacetime inside the bubble forward. The direction is only affected by the possition of the contracted and expanded space time parts of the bubble. So it wont fall towards the Sun.

[Galacticruler]

An AD ship may actually cause an explosion of gamma rays, X-rays, cosmic rays, etc... when it drops out of the warp field. I read this somewhere.

They also have the possibility of shifting the orbits of nearby planets.

[K^2]

An AD spaceship doesn't have any speed, the warp bubble around it pushes the spacetime inside the bubble forward. The direction is only affected by the possition of the contracted and expanded space time parts of the bubble. So it wont fall towards the Sun.

That's essentially correct. An Alcubierre Drive warp bubble can travel along an arbitrary trajectory. That trajectory defines the field's metric, and that, in turn, tells you where you need to pump energy to maintain the field. So unless you want to be falling towards the Sun, you won't be.

An AD ship may actually cause an explosion of gamma rays, X-rays, cosmic rays, etc... when it drops out of the warp field. I read this somewhere.

Not directly, but yes. Any particles picked up by the warp bubble that have not been released during transit will be released with a lot of energy when the ship drops out of warp. That's just one of the reasons why you wouldn't want to arrive or depart from LEO using warp.

[rtxoff]

Well that's no conclusive answers yet, maybe some very primitive drawing can help you with that question.

What will happen here? Is this even possible?

[Aethon]

Here's an hour long video, unfortunately with some really... really poor production values, but It features (former?) NASA employee Howard White explaining the warp concept.

Pro tip : No headphones and turn down your volume for the first min.

[K^2]

Well that's no conclusive answers yet

Suit yourself.

[phoenix_ca]

Not directly, but yes. Any particles picked up by the warp bubble that have not been released during transit will be released with a lot of energy when the ship drops out of warp. That's just one of the reasons why you wouldn't want to arrive or depart from LEO using warp.

Dr. Harold White in the video Aethon linked has a very different take on that. He suggests that instead the particle would pass through the compressed spacetime, into the bit of flat spacetime, and assuming it doesn't hit anything there, straight though and out again. The particle would be translated in position when it pops-out again, but it wouldn't get stuck on the bubble.

[Stargate525]

Here's an hour long video, unfortunately with some really... really poor production values, but It features (former?) NASA employee Howard White explaining the warp concept.

Current. He's got a team working on a machine to generate teeny-tiny warp rings.

[K^2]

Dr. Harold White in the video Aethon linked has a very different take on that. He suggests that instead the particle would pass through the compressed spacetime, into the bit of flat spacetime, and assuming it doesn't hit anything there, straight though and out again. The particle would be translated in position when it pops-out again, but it wouldn't get stuck on the bubble.

That's correct, during uniform travel. But that's not what happens when bubble accelerates or decelerates. While particles do pass through, they take some time to do so. Any particles still in the bubble when the ship drops out, these are released with a lot of energy. I might be able to find the article on that, if you are interested.

[rtxoff]

IMHO as far as i understood the AD:

Creating a warp field, so compressing spacetime in front of your ship end expanding it in the back won't get you anywhere alone. You will need some movement speed relative to something to get you anywhere.

So if you imagine yourself walking on a road, the warp field would shorten the road in front of you but you still need to be walking forward to get anywhere.

So the answer for my question would be that the spaceship would seem to slow down. I guess by intensifying the warp field it would just seem slow it down more and more but you could not reach the point where it completely stops. Also i think gravity won't pull you towards the sun because you still have orbiting speed,just in an very expanded space in front of your ship. So i guess the dV requirements will stay the same with an AD or without it. To leave sun's SOI you will still need some conventional form of propulsion but the time you are going to travell after your burn can be reduced greatly with an AD.

Or maybe i am on an dead end with my thoughts.

What do you guys think?

[MonkeyFuzz]

That's correct, during uniform travel. But that's not what happens when bubble accelerates or decelerates. While particles do pass through, they take some time to do so. Any particles still in the bubble when the ship drops out, these are released with a lot of energy. I might be able to find the article on that, if you are interested.

From the video, Dr. White answers a question about particles being caught in the warp field. Large objects (stuff bigger than bits of radiation) would enter and exit the warp bubble, having had their exit position transposed by the effects of the field. My understanding of his answer for radiation caught in the field was that particles would not get caught for a substantial amount of time in it. As part of his warp equation, the field is adjusted in strength/size (this is supposed to reduce the amount of mass-energy required versus earlier equations that kept the warp field at a set intensity/thickness). Each time the field dips it would spill captured particles/radiation. I think.

[K^2]

From the video, Dr. White answers a question about particles being caught in the warp field. Large objects (stuff bigger than bits of radiation) would enter and exit the warp bubble, having had their exit position transposed by the effects of the field. My understanding of his answer for radiation caught in the field was that particles would not get caught for a substantial amount of time in it. As part of his warp equation, the field is adjusted in strength/size (this is supposed to reduce the amount of mass-energy required versus earlier equations that kept the warp field at a set intensity/thickness). Each time the field dips it would spill captured particles/radiation. I think.

Doesn't matter. When you drop out of warp, you'll still have some particles in the bubble. Space is nowhere near as empty as some people seem to think. White's design might reduce the effect, I have not seen it being worked out for an oscillating field, but it's still going to be there. And it's still going to make warp entirely too dangerous in Low Earth Orbit. But there is no reason to use it in LEO. You are still going to need conventional thrust to get yourself going, because of the way gravity interacts with a warp ship, and so you can just wait until you pull away to a safe distance from Earth before engaging warp. Same deal with approaching any station. There is really no reason to go into warp or drop out of it right at your origin/destination.

[rtxoff]

Next question:

Can the AD reduce the amount of thrust you need to slow you down to orbital speed from a high speed approach?

[Cmdr. Arn1e]

Copied from the recent Gizmodo article on the subject;

"A spaceship equipped with a warp drive would allow faster-than-light travel by bending the space around it, making distances shorter. At the local level, however, the spaceship wouldn't be moving faster than light. Therefore, warp drive travel doesn't violate the first Einstein commandment: Thou shall not travel faster than light."

So, technically it would bend even gravity around itself too, as gravity is part of space-time... being inside a 'warp bubble' would negate a lot of things theoretically...

The article in question finishes up with 'If his work is successful, he says that we would be able to create an engine that will get us to Alpha Centauri "in two weeks as measured by clocks here on Earth." The time will be the same in the spaceship and on Earth, he claims, and there will not be "tidal forces inside the bubble, no undue issues, and the proper acceleration is zero. When you turn the field on, everybody doesn't go slamming against the bulkhead, which would be a very short and sad trip."'

"No tidal forces" to me indicates that my previous statement about gravity may be true...

Further, no, you don't 'accelerate' in the traditional sense of the word... it lays the 'warp bubble' down in front of it, and kind-of pulls itself along using this ever-expanding and contracting 'bubble', a bit like some underwater creatures such as dolphins use... (they actually 'slipstream' through the water using tiny bubbles that decrease the water drag!) but using one big bubble instead of lots of little ones...

[SolarLiner]

Next question:

Can the AD reduce the amount of thrust you need to slow you down to orbital speed from a high speed approach?

As said by Cmdr. Arn1e, it's only externally that the AD does its magic. Inside the "wrap bubble", nothing gets changed.

And AD wraps space, so it wraps time. Acceleration and deceleration would seem shorter, but in fact, time is really passing by faster, so no. Assuming that thrust is a force counted as "external", because if "internal" in relation to the "wrap bubble", it won't change at all.

And to answer the first question (if not already, TL;DR), the AD doesn't have a force, thus it does not have a vector. You do not "point" an AD, you use it. So using the AD in your solar orbit would seem to make the orbtal velocity faster.

[shynung]

And to answer the first question (if not already, TL;DR), the AD doesn't have a force, thus it does not have a vector. You do not "point" an AD, you use it. So using the AD in your solar orbit would seem to make the orbital velocity faster.

So a spacecraft would still need standard reactive engines such as rockets, and do all the necessary transfer maneuvers (either Hohmann or Brachistochrone, depending on delta-v budget) to go from A to B.

[Cmdr. Arn1e]

So a spacecraft would still need standard reactive engines such as rockets, and do all the necessary transfer maneuvers (either Hohmann or Brachistochrone, depending on delta-v budget) to go from A to B.

Yep, the 'warp' would not be usable for 'normal' spaceflight (depending on findings, there are 2 levels of warp travel, sub-light and FTL...) and would need some other sort of engine for maneuvering - be this a traditional liquid engine or a more advanced form of propulsion is also yet to be seen...

Just to throw something else out there, I don't think we would be able to build and launch this type of vehicle terrestrially; I think it would need to be built in some sort of space dock... which would also cut down on the amount of fuel required for maneuvers...

[KvickFlygarn87]

The AD will move you, not change your speed.

[shynung]

Just to throw something else out there, I don't think we would be able to build and launch this type of vehicle terrestrially; I think it would need to be built in some sort of space dock... which would also cut down on the amount of fuel required for maneuvers...

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. 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.