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Harold White's warp drive and OA
#1
http://io9.com/5963263/how-nasa-will-bui...warp-drive

This is sort of old news at this point, but on the pages regarding void bubble related tech (displacement drives, halo drives, void ships) it's stated that the energy requirements for producing a void bubble are very high. The paper linked above suggests that a toroidal configuration would reduce the energy requirement down to a few tons. If valid, doesn't this mean that some of the information regarding void bubbles should be updated?

To be clear, I am aware that, despite all the sensationalism surrounding this, such a drive would probably not allow for faster than light travel; with the exception of the high energy requirement, it still possesses all the problems of previous versions as far as I understand them (and what I understand is quite limited).

Sorry about the I09 link. The actual NASA page is down, and the article linked above contains a link to the NASA page. Hopefully it will be back up soon.
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#2
A few tonnes-equivalent of negative mass/energy would still be very tricky to produce, even if that quantity were enough to produce a usable warp bubble. At present the amount of negative mass-energy that can be produced is vanishingly small. I don't anticipate that exotic tech like this will be useful in the foreseeable future -

but maybe sometime in the unforeseeable future it will be...
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#3
(04-20-2013, 09:09 AM)Sim Koning Wrote: http://io9.com/5963263/how-nasa-will-bui...warp-drive

This is sort of old news at this point, but on the pages regarding void bubble related tech (displacement drives, halo drives, void ships) it's stated that the energy requirements for producing a void bubble are very high. The paper linked above suggests that a toroidal configuration would reduce the energy requirement down to a few tons. If valid, doesn't this mean that some of the information regarding void bubbles should be updated?

Not reallySmile Reviewing the relevant EG article here:

http://www.orionsarm.com/eg-article/493f29cc472f0

it actually says:

"However, even such 'efficient' warp bubble effects still appear to require the use of massive external generation facilities and multi-solar mass instrumentalities to create them (although the associated drive node stabilization and control devices appear to be quite compact, perhaps only a few meters across at most)."

Which basically says that it takes a lot of mass-energy to both 'pre-warp' space to help you make a bubble and to generate whatever amount of negative energy is required (it's not clear exactly what sort of machine would be required to do that but it could be pretty large, especially for industrial production levels). It doesn't explicitly say how much is used although it does provide the formula used to calculate how much if we only knew the exact properties of OA warp bubblesSmile

Putting this in more familiar terms, it could take a huge amount of infrastructure to generate even a small amount of anti-matter even with techniques vastly better than what we have now. Something similar could apply here.

On a more general note, at this particular stage White type warp drive doesn't seem to have enough experimental or other backing to indicate that it is clearly the way that a warp drive would be done or that such would require significantly less mass, energy, and infrastructure than what we describe or would be doable by humans. If some more definitive proof eventually comes along, we can then consider revising the website accordingly. However, in the interim, I think we would prefer to leave as is and presume that OA warp bubbles as described either already incorporate properties similar to White warp bubbles or that White's theory (or the machinery to implement it) was ultimately proven to be unworkable/unsolvable by human level minds and so warp bubbles remained beyond the reach of Terragen civ until the S4 archailects came along and figured it out.

(04-20-2013, 09:09 AM)Sim Koning Wrote: Sorry about the I09 link. The actual NASA page is down, and the article linked above contains a link to the NASA page. Hopefully it will be back up soon.

No worriesSmile We don't have anything against I09 per se AFAIK. It would be nice if every interesting article and paper were readily available in its original form online, but that just isn't the case (yet).

Thanks for sharing the idea and please keep posting as new ideas or information (on this or whatever other OA relevant stuff interests you) as you find it.

Thanks!

ToddSmile
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#4
http://www.universetoday.com/93882/warp-...z2FaZsXDuM

Does anyone know if this would apply to (STL) void ships?
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#5
Since the article explicitly says this only happens with FTL warp bubbles and OA warp bubbles can't exceed light speed I'd think not. Beyond that I find this article highly suspect since it includes neither hard numbers nor formulae to calculate any. Saying that a lot of energy is released without providing any context opis kinda bogus. Are we talking energy sufficient to kill anyone within km of where the ship slows down or hundreds or thousands of megatons of energy? They don't say.

Beyond that they say nothing about what numbers they use for the density o the interstellar medium, which is quite diffuse and isn't going to add up to a lot unless the warp bubble is a certain size. And OA warp bubbles are only picometers across from outside and never turn off so the issue doesn't seem to apply. Even a bubble hundreds of meters across isn't going to encounter many particles even across light years.

Finally, and thinking about this a bit, I'm having a hard time seeing how it would be possible for particles to be 'swept up' in the warp field and somehow supplied with massive amounts of kinetic energy such that they are basically relativistic particles when the warp field turns off. Mainly since a warp bubble doesn't actually apply velocity to anything, which is really rather the point and what lets it move reactionlessly or FTL in the first place. Any particles somehow caught up in it should appear to move as fast as the bubble but then come to a halt when the bubble does (the bubble should also be able to either stop instantly or slow down at a rate only limited by the rate at which the warp 'configuration' can be changed. Conventional braking has nothing to do with it). Anything else would seem to require the warp drive to apply energy to the particles in question which would count as inefficiency on its part and likely something you don't want and that would be separate from normal drive operation.

One of our physics gurus may weigh with more info on this, but I'm highly dubious about it at this point, both in general and even more re OA.

ToddSmile
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#6
http://ut-images.s3.amazonaws.com/wp-con...-final.pdf

I found the actual paper. Sorry, I should have provided this the first time around. Unfortunately, my physics knowledge is limited to the I-can-barely-understand-the-abstract level (I'm more of a biology nerd), so any help here is greatly appreciated. I'm a big fan of hard SF, but I often have difficulty with understanding the physics stuff.
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#7
Ok, I read through the paper. Let me start by saying the math is totally over my head, but I think I got most of the gist of what they are saying.

First off, they seem to confirm that the radiation flash associated with a warp drive only becomes an issue at superluminal speeds. As such, it wouldn't be a concern in OA since our warp bubbles can get arbitrarily close to c but can't ever achieve or exceed it.

Second, they seem to be assuming that a warp bubble would be bigger than the ship it contains, both on the inside and outside. This is not actually the theory that OA warp bubbles are based on (they are much bigger on the inside than the outside per one of the current theories about how a warp drive might be made to work). OA warp bubbles are only picometers across on the outside and so will have very few interactions with either particles or photons. So I don't think it would be an issue even if our warp bubbles were FTL.

Third, they don't provide any actual example of what sort of radiation flash they are talking about. However, even if their warp bubble is of macroscale externally, it will have relatively few particle or photon interactions in most cases and I find it very hard to believe that the energies involved would be comparable to (for example) a gamma ray burst or even a solar flare.

As such, while it might not be a good idea to be right next or in the path of a ship as it slows down, I don't think what they describe is going to cook a planet or a solar system or come anywhere close to that. A gamma ray burst striking the Earth would screw up our ozone layer but wouldn't cause any actual physical damage on the surface. A solar flare is only a problem for our technology not biology on the ground.

On a more practical note, the analysis seems to me to be rather like the old paper about amat rockets that concludes that the gamma exhaust from a ship would fry the Earth as the ship boosted out of orbit. It apparently never occurred to the author that a ship might coast or use other methods to move well away from habitable planets and such before lighting up the main drive. In a similar vein, a warp ship could slow down well away from any inhabited areas and then either 'hop' to the final destination or travel there at sub-light speeds via warp or any number of conventional methods. For that matter, the old SF trope of FTL ships coming out of stardrive practically in orbit or next door to their destinations seems highly unlikely and is only there for dramatic effect. In practice, crossing light-years of distance is going to result in a certain amount of fine-tuning being required along the way and a ship probably won't be able to pinpoint its destination that closely in one jump even if it wants to.

Overall, I'd conclude that this isn't an issue for OA type warp drive and probably not even an issue for FTL warp drives if they ever become possible.

My 2c worth,

ToddSmile
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#8
Thank you very much for the informative response. As you said, even if this is a problem, it would just be another in a long list of problems for FTL warp drives, which doesn't surprise me nor do I find it disappointing since I actually prefer space opera without FTL (OA-style wormholes are the exception since they're not true FTL).
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#9
The distortion of spacetime around a fast-moving ship is quite counterintuitive. Even for a sub-light spacecraft travelling at relativistic speeds there are some curious effects, such as relativistic beaming
[Image: AGN_Jet_Aberration.png]
http://en.wikipedia.org/wiki/Relativistic_beaming
and the searchlight effect
http://www.relativitybook.com/resources/aberration.html

Another weird phenomenon is the Unruh effect, an increase in the apparent temperature of empty space as observed by the vessel.
http://en.wikipedia.org/wiki/Unruh_effect
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#10
http://spaceref.com/nasa-hack-space/prop...ogram.html

Interesting investigation relating to the recent Popular Science article on the subject. Unsurprisingly, it seems as though the author of the Pop-Sci article got some things wrong.

Here is the wiki article on his research: http://en.wikipedia.org/wiki/White-Juday...rferometer
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