Dr. Lentz's Warp Drive.

[Scotius]

So, while trawling the Internet, i found articles about newest (still theoretical, sadly) development in the field of FTL propulsion:

https://www.eurekalert.org/pub_releases/2021-03/uog-btw030921.php

In a nutshell: Dr. Eric Lentz from the University of Groeningen (sp?) developed a theoretical model of classic Alcubierre's Warp Drive that does not require negative energy to work!

Even better - it sidesteps the problem of time paradoxes that tend to crop up every time something tries to travel faster than light

Sadly, it still requires exotic shenanigans in the form of "solitons" - but apparently those at least do not break our current understanding of laws of physics. Energy requirements are still rather... steep (100+ masses of Jupiter for decently sized spaceship... *le facepalm* ).

Fortunately, Dr. Lentz says there are plausible ways to significantly cut those requirements to a more realistic size. "Large fission power plant" realistic.

Could it be a real breakthrough?

Or will it remain just a theoretical curiosity, good only for tormenting space nerds with Possibilities?

[KSK]

It'll only be a practical breakthrough if he can drop the energy requirements by the 60 orders of magnitude mentioned in the article, which seems like a tall order. Even if it doesn't turn out to be practical, maybe it'll be one step along the way to a theoretical model that can be made to work: Alcubierre - Lentz - ?? - ?? etc.  Sadly, I have nowhere near the maths to understand the actual paper or decide whether its correct.

In the meantime the Lorentz-Lentz Drive is an excellent name for a fictional FTL engine

 

[K^2]

I'll give it an actual read to confirm later, but in general, the biggest problem with pretty much every model, including Alcubierre, is that they don't take mass of the ship into account. Yes, it might seem insignificant compared to energies involved in the bubble, but it's also where the hard requirement for having negative energy involved comes in. The bubble can do all sorts of nifty things, but at an absolute minimum, you have to cancel the mass of the ship to have any hope to go FTL.

This is a lot easier to show with Alcubierre due to spherical symmetry, but the gist stays the same. You can't have flat space-time beyond the bubble if the ship inside the bubble has mass and the bubble doesn't contain negative energy to cancel it. This can be derived directly from GR. Now, if space-time outside the bubble isn't flat, then the bubble can't reach the speed of light, much less exceed it, for the same reason an ordinary object can't. Accelerating any object that generates curvature requires extra energy the faster it's already moving, and that energy diverges to infinity as you get closer to light speed. So light speed is the asymptomatic limit unless you cancel out the mass of the ship with negative energy in the bubble.

This also ties neatly into some fundamental conservation laws in GR. Again, way easier to show rigorously on Alcubierre, but you can see it in a simple thought experiment. What happens to a ship orbiting the Sun at 1AU (orbit of Earth) if it warps to 5AU (orbit of Jupiter)? It doesn't have enough energy or angular momentum to be up there. It is possible to show in sublight warp with Alcubierre that the bubble will radiate gravitational energy providing propulsion. And in general, any warp bubble that doesn't cancel ship's mass will radiate gravitational energy in such a warp. But this radiation is impossible under FTL. You literally can't have a bubble carry any positive quantity of mass at FTL speeds. The net mass must be zero.

Even under all these limitations, practical sublight warp would be absolutely amazing to develop. And Alcubierre, sadly, requires negative mass even for sublight travel. But there is no hard limit preventing a theoretical warp that carries a ship along its geodesic (so, same orbit it was already on) at a much higher, albeit, subluminal speed. In other words, if you burned conventional engines for a transfer, but then instead of waiting for months or even years to complete transfer, you could be there in days or even hours. That's absolutely a solid win, and nothing in GR flat out says it can't be done without exotic matter. Maybe the idea in this paper is adaptable to that sort of warp, in which case, that would be absolutely fantastic. But I have to call BS on any FTL without negative energy for the same reason I can call BS on any perpetual motion machine with magnets without getting into details.

[KSK]

I wonder if sublight warp is what Dr Lentz actually has in mind and the writers of the article got a bit muddled?

The article mentions travel times of years to Proxima Centauri, which could easily mean travelling at close to c but not beyond it.

[Scotius]

17 minutes ago, KSK said:

I wonder if sublight warp is what Dr Lentz actually has in mind and the writers of the article got a bit muddled?

The article mentions travel times of years to Proxima Centauri, which could easily mean travelling at close to c but not beyond it.

Essentially, traveling at relativistic speed without time dilation affecting the ship?

But doesn't it decouple time from spacetime continuum we live in?

I'm not sure it is positive for the crew. At least from their perspective, time dilation significantly shortens the boring part of the journey

[kerbiloid]

5 hours ago, KSK said:

Lorentz-Lentz Drive

Lentz-Lorentz

Just to sound faster.

L[or]entz for perfectionists.

1 hour ago, Scotius said:

But doesn't it decouple time from spacetime continuum we live in?

It will create its own continuum, with time and shenanigans.

Edited March 28, 2021 by kerbiloid

[Scotius]

5 hours ago, kerbiloid said:

It will create its own continuum, with time and shenanigans.

And Kraken. Because this is how you summon the Kraken.

[K^2]

16 hours ago, Scotius said:

Essentially, traveling at relativistic speed without time dilation affecting the ship?

Technically, you can tune time dilation inside the bubble, but it might require the ship to accelerate, which is exactly the thing you're trying to avoid.

[sevenperforce]

On 3/28/2021 at 5:39 AM, K^2 said:

the biggest problem with pretty much every model, including Alcubierre, is that they don't take mass of the ship into account. Yes, it might seem insignificant compared to energies involved in the bubble, but it's also where the hard requirement for having negative energy involved comes in. The bubble can do all sorts of nifty things, but at an absolute minimum, you have to cancel the mass of the ship to have any hope to go FTL.

This is a lot easier to show with Alcubierre due to spherical symmetry, but the gist stays the same. You can't have flat space-time beyond the bubble if the ship inside the bubble has mass and the bubble doesn't contain negative energy to cancel it. This can be derived directly from GR. Now, if space-time outside the bubble isn't flat, then the bubble can't reach the speed of light, much less exceed it, for the same reason an ordinary object can't.

This is hands-down the best explanation I've ever heard of this. Thanks.

[KSK]

On 3/29/2021 at 6:01 AM, K^2 said:

Technically, you can tune time dilation inside the bubble, but it might require the ship to accelerate, which is exactly the thing you're trying to avoid.

Nah - you just take a jump to the left... and then a step to the right. The rest of the procedure for doing a time warp is skirting the edge of safe-for-forum though.  

[K^2]

2 hours ago, KSK said:

Nah - you just take a jump to the left... and then a step to the right. The rest of the procedure for doing a time warp is skirting the edge of safe-for-forum though.  

This is a serious discussion. You should be ashamed.

 

Eh, what the hell.

LET'S DO THE TIME WARP AGAIN!

[KSK]

 
 

But on a more serious note, I second @sevenperforce’s comment about your earlier post.

I’ve seen a lot of discussions about heavy-duty physics get bogged down in increasingly tortuous analogies because a proper answer requires more maths than anyone in the discussion has.

It’s great to have someone on a forum who gets the maths and can explain it too.

 

[Ethan13]

In the course of our lives, this is absolutely unrealistic. But once the flight of a plane was considered a fantasy. Every year, someone finds errors in previous math calculations or suggests new ones. Perhaps we don't have enough knowledge about physics yet. It would be great if travel above the speed of light were possible without breaking the laws of physics.

[JoeSchmuckatelli]

On 3/30/2021 at 9:46 AM, KSK said:

It’s great to have someone on a forum who gets the maths and can explain it too.

You ain't lyin! 

 

This here Frozen Caveman Lawyer really appreciates the folks with the maths and the patience to explain 

[sevenperforce]

On 3/30/2021 at 9:46 AM, KSK said:

But on a more serious note, I second @sevenperforce’s comment about your earlier post.

I’ve seen a lot of discussions about heavy-duty physics get bogged down in increasingly tortuous analogies because a proper answer requires more maths than anyone in the discussion has.

It’s great to have someone on a forum who gets the maths and can explain it too.

Exactly.

A crackpot talks about science but never does the math.

A scientist knows the math is necessary to do science.

But it takes real skill to understand the math but talk about science without it.

[kerbiloid]

Another well-explained warp drive.

Still no actually working theory.