Alternative to chemical engines --- warp?

[Guest]

What's is the point of your question? nobody can claim to have a complete understanding of the universe, we know that the light speed limit is real, and that breaking it will bring consequences such as breaking causality and time travel. You can't claim that just because our understanding of our universe is incomplete the warp drive is a possibility, that's just wishful thinking.

You're wrong. Alcubierre drive doesn't break the speed of light, nor does it violate causality. This is what makes it different from FTL travel. Turns out that mathematics work out pretty well in it's case, though the specifics depend on which theory you prefer. From a purely mathematical point of view, Alcubierre drive is possible if you make certain assumptions. Now, we do not know if those assumptions apply to our universe, but that's what we're trying to find out.

Also, looking at this discussion, none of you understands what Alcubierre drive is all about. It does not, in fact, cause anything to travel faster than light at any point. Instead, it sort of reshapes the fabric of the universe itself to bring our destination closer to us, and our departure point away from us. And there's no fundamental, proven, physical limit saying "no, you can't do that". In fact, Universe did expand faster than light at some point of it's existence. Now, there as well might be a limit that would prevent it from ever becoming usable for exploring the stars, but we don't know that yet. Even mathematics that would be needed for that are not quite there yet.

Imagination is needed for progress of any sort. Iterative improvements can be made by people who know the limits, but the real breakthroughs are made by people who either don't know them, or knowingly reject them. By following a paradigm you reach the limits of that paradigm, but if you step out of the paradigm, you can exceed those limits. It's not like methane-LOX engines were impossible at any point in the past, it's just that noone thought of them (well, Glushko did, but nothing came out of that, as cost didn't matter that much back then) until Elon Musk. The result could a Ford model T of spaceflight. There are two kinds of people. Those who think off new ideas and those who slap themselves on the face thinking "why didn't I think of it?".

Edited April 13, 2014 by Guest

[xcorps]

Have you read how the Alcubierre drive works? It follows the laws of physics.

No it doesn't. The Alcubierre drive does not exist. It is speculation.

It might work, if certain conjectures turn out to be verifiable in the proposed experiments a few centuries from now under the right conditions. Maybe.

[m4v]

You're wrong. Alcubierre drive doesn't break the speed of light, nor does it violate causality.

Any form of FTL travel can be used for travel back in time and create causality problems.

And I would really drop the "none of you understands" line.

[R0cketC0der]

Any form of FTL travel can be used for travel back in time and create causality problems.

And I would really drop the "none of you understands" line.

How would it allow you to travel back in time?

[m4v]

How would it allow you to travel back in time?

I don't know, I don't understand that part myself, but any physicist will tell you that.

[Comrade Jenkens]

The whole point of this drive is it doesn't exceed the light speed barrier locally at any point and so doesn't have the causality problems. Any two objects can travel faster than light relative to each other without breaking the speed of light locally.

As for the warping of space it is well known that it is possible. Whether we can do it artificially though is another matter entirely.

[rtxoff]

The whole point of this drive is it doesn't exceed the light speed barrier locally at any point and so doesn't have the causality problems. Any two objects can travel faster than light relative to each other without breaking the speed of light locally.

As for the warping of space it is well known that it is possible. Whether we can do it artificially though is another matter entirely.

According to Einsteins theories this is not true. None of two objects can travel faster than light relative to each other even if they move away from each other at light speed. :-)

It is weird but this is something many people do not understand about the theory.

[Scotius]

It's like surfing. When you are pushing the board with your own muscles, you can reach only few km\h. Anything faster is physically impossible, because our muscles can generate only so much power. But when you ride on top of a wave, you are moving much faster. Current world record is about 39 km\h or so.

[rtxoff]

The only thing right now we know for sure that warps space is mass. Attaching a black hole in front of your vehicle and keeping it there will create your warp drive ;-)

P.S.: You will loose your warranty with the struts by doing so.

Edited April 13, 2014 by gpisic

[TheGatesofLogic]

As I understand it, it allows you to change your position in space without changing your velocity. Say you were travelling away from an object at 20m/s and you warp closer to it, once you exit the warp bubble you are still travelling away from it at 20m/s.

again, no, it's a heck of a lot more complicated than that, and understanding it requires an advanced understanding of general relativity and spacetime metrics, I hardly understand the actual math at all really, but it just isn't as simple as people make it out to be.

IIRC the gist of it is that you would accumulate all the acceleration you would otherwise accumulate from gravity over the time-period of the "warp" that you ought to accumulate from local spacetime curvature. This means that you can't warp to the opposite side of a star and slow yourself down with "gravitational drag" because the ship's relative velocity after the warp would instead be towards the star, rather than away from it due to the curvature of spacetime. (don't quote me on that.)

Edited April 13, 2014 by TheGatesofLogic

[K^2]

I don't know, I don't understand that part myself, but any physicist will tell you that.

Physicist, checking in. No, Alcubierre Drive, by itself, does not allow for time travel. An arbitrary FTL drive is, indeed, a time machine, but there are restrictions on Alcubierre Drive specifically that prevent you from using it as such in flat space-time.

One can come up with a suitable curved space-time which will have closed time-like curves which can be navigated under Alcubierre Drive. It is not certain if such curvature exists naturally, however. Creating something like that artificially is not something we can do with physics as we know it.

On the other hand, principles that go into creating a warp bubble in the first place might be usable to construct a time machine completely independently. That, however, is not actually a problem with any of the physics we know.

[m4v]

On the other hand, principles that go into creating a warp bubble in the first place might be usable to construct a time machine completely independently. That, however, is not actually a problem with any of the physics we know.

So temporal paradoxes are not a problem?

[K^2]

So temporal paradoxes are not a problem?

I'm not going to speak for moral, theological, or legal issues. But in terms of underlying physics, no, they are not a problem. Field theory only requires causality locally, which there is no known way of violating, and global causality violations are not actually a problem. The fact that there are paradoxes in classical limit is just a reflection of the fact that we've built assumption of global causality into classical limit. In other words, our "every day physics" isn't built to deal with time travel, but that's the problem with our description, and not with the concept itself.

[Scotius]

And how does it look from layman's PoV? We can't cause local paradox - so it's impossible to travel to the past and kill Hitler, preventing WWII. But what is allowed by global causality? We can do anything, as long as it does not influence our own timeline? For example we could go to the past of distant, barren planet and seed life where it should not exist normally - and it would be possible because up to this point, there was no interaction between our local causality "areas"?

[Random Tank]

For these people that say: 'The Alcubierre drive isn't possible because FTL travel breaks the laws of physics and would result in impossible time travel (or something along those lines)'; this isn't true because using an Alcubierre drive doesn't move anything FTL.... In fact it doesn't move anything at all!

Simple analogy time!

You have Earth, and a ship that is 5 billion km away. The ship activates its Alcubierre drive; before it activated it, neither object was moving (relative to each other); after it activated it, neither object is moving. The only actual change is that the gap between them is now 10 billion km; because space expanded. If you could measure rate of expansion, you'd find it was faster than the speed of light, but it isn't a speed; nothing ever moved, the gap between the 2 just got bigger....

[m4v]

For these people that say: 'The Alcubierre drive isn't possible because FTL travel breaks the laws of physics and would result in impossible time travel (or something along those lines)'; this isn't true because using an Alcubierre drive doesn't move anything FTL.... In fact it doesn't move anything at all!

Doesn't matter, having a working Alcubierre drive means that time machines are possible, although K^2 said that they aren't a problem.

[KASASpace]

Well, an Alcubierre Drive to LEO isn't practical, as the extreme gravity "wells" in front and in back would destroy, pretty much, almost everything.

[K^2]

And how does it look from layman's PoV? We can't cause local paradox - so it's impossible to travel to the past and kill Hitler, preventing WWII. But what is allowed by global causality? We can do anything, as long as it does not influence our own timeline? For example we could go to the past of distant, barren planet and seed life where it should not exist normally - and it would be possible because up to this point, there was no interaction between our local causality "areas"?

Edited April 14, 2014 by K^2

[KASASpace]

It wouldn't really destroy anything. There can be too much radiation due to residual atmosphere impacting the warp bubble. That can cause warp bubble to collapse as well. So yeah, you'd probably want to leave LEO before you engage warp drive. Could still be pretty decent way to get around the Solar System, though.

The gravitational fields would have to be fairly strong.

Although, leaving the Earth into space could be done with negative matter, which is ejected later on if done so.

[m4v]

how easy! if we only had such thing.

[Mazon Del]

Actually, KASASpace, we may not require negative matter at all, if you look up the 2013 Starship Congress videos, I believe on day 3 (could be wrong) a physicst steps up to discuss a line of research that may allow us to 'conventionally' create the effects brought on by negative/exotic matter. This makes for great news because effectively the only part of the warp drive we don't have an idea how to produce is the back part (where space expands). The front part is comparatively easy, it just requires you dump a good bit of energy into a small enough location, which our friend Harold White at NASA's Micro Warp Field Interferometer is investigating creating. Based on his math, the energy levels required to send a several ton spacecraft at 10 times the speed of light is not as much as Alcubierre originally feared. Alcubierre's original design stated that it required converting the mass equivalent of Jupiter into energy. Harold found ways to alter the design (instead of a sphere that is always on, it is an egg-shape that flickers on and off) that drastically dropped the energy requirements to something possible within the near future (<50 years if we were trying, <100 if we weren't).

Additionally, for a great addition, the same technologies that will make a warp drive possible are the same technologies required to manufacture traversable wormholes. Imagine sending a ship using the warp drive from Earth over to Alpha Centauri, having it pop out a wormhole station that leads back to Earth Orbit, and now you've got yourself a lovely little window from star to star.

[KASASpace]

Actually, KASASpace, we may not require negative matter at all, if you look up the 2013 Starship Congress videos, I believe on day 3 (could be wrong) a physicst steps up to discuss a line of research that may allow us to 'conventionally' create the effects brought on by negative/exotic matter. This makes for great news because effectively the only part of the warp drive we don't have an idea how to produce is the back part (where space expands). The front part is comparatively easy, it just requires you dump a good bit of energy into a small enough location, which our friend Harold White at NASA's Micro Warp Field Interferometer is investigating creating. Based on his math, the energy levels required to send a several ton spacecraft at 10 times the speed of light is not as much as Alcubierre originally feared. Alcubierre's original design stated that it required converting the mass equivalent of Jupiter into energy. Harold found ways to alter the design (instead of a sphere that is always on, it is an egg-shape that flickers on and off) that drastically dropped the energy requirements to something possible within the near future (<50 years if we were trying, <100 if we weren't).

Additionally, for a great addition, the same technologies that will make a warp drive possible are the same technologies required to manufacture traversable wormholes. Imagine sending a ship using the warp drive from Earth over to Alpha Centauri, having it pop out a wormhole station that leads back to Earth Orbit, and now you've got yourself a lovely little window from star to star.

I was referring to getting into space, negative matter "defies" gravity and thus will simply leave the Earth, although eventually it would get trapped, because gravity is everywhere(maybe that's why we haven't seen much of it, it's trapped)

[Mazon Del]

If the negative matter you are referring to is the kind that has the opposite polarization of gravity (IE: It pushes instead of pulls) then these are the same thing. That is the part that is missing from the warp drive. We need something that can 'push' space in order for the ship to exist in a flat spacetime for the full alcubierre warp drive to work. Without the back, we just have a pretty snazzy engine technology.

[K^2]

Eh. Sort of. It'd be enough to lower energy bellow zero point. That would still repel from masses, albeit, more like bubble surfacing in a liquid. But you wouldn't be able to use it to lift something out of gravitational field, because everything you need to produce such negative energy density will be much heavier. So net mass will always be positive. That's not a problem for warp ship. We can work with this, and that's the main reason people are hopeful about the idea overall. But you can't use it to escape the star system. You'll still need reaction drives to do that. So to escape a star system, or a planet, you'll still have to use ion drives or conventional rockets to accelerate to escape trajectory. But then you can use warp to speed up the process, so that instead of months, you could reach outer Solar system in hours.

I don't share your enthusiasm for wormholes, however, Mazon Del. Yes. Same principles that can be used to build a warp ship can be used to make an untraversable wormhole traversable. In fact, FTL ship can traverse some untraversable wormholes already, because it can follow time-like trajectories. Problem, however, is in making a wormhole of any kind in the first place. The kind of wormhole you are thinking of requires a change to topology of space-time, and there is no mechanism for that. We can alter geometry, but only within existing topology. Which means, if we were to find a natural wormhole, we could move its openings to where we need them and make it traversable. But we can't make one completely from scratch.

[KASASpace]

Eh. Sort of. It'd be enough to lower energy bellow zero point. That would still repel from masses, albeit, more like bubble surfacing in a liquid. But you wouldn't be able to use it to lift something out of gravitational field, because everything you need to produce such negative energy density will be much heavier. So net mass will always be positive. That's not a problem for warp ship. We can work with this, and that's the main reason people are hopeful about the idea overall. But you can't use it to escape the star system. You'll still need reaction drives to do that. So to escape a star system, or a planet, you'll still have to use ion drives or conventional rockets to accelerate to escape trajectory. But then you can use warp to speed up the process, so that instead of months, you could reach outer Solar system in hours.

Unless you, you know, quite obviously DON'T carry all the equipment required to GET the negative matter.

I don't share your enthusiasm for wormholes, however, Mazon Del. Yes. Same principles that can be used to build a warp ship can be used to make an untraversable wormhole traversable. In fact, FTL ship can traverse some untraversable wormholes already, because it can follow time-like trajectories. Problem, however, is in making a wormhole of any kind in the first place. The kind of wormhole you are thinking of requires a change to topology of space-time, and there is no mechanism for that. We can alter geometry, but only within existing topology. Which means, if we were to find a natural wormhole, we could move its openings to where we need them and make it traversable. But we can't make one completely from scratch.

I believe he meant one that we ALREADY knew of.

Plus, wormholes would take too much energy, I would suggest "chords" or pot-holes.

A pot-hole is where only a small area of space is "folded" rather than the entirety.

Taking all of space and folding makes no sense energy-wise.