Well. This could be a game changer. New Warp Drive theory

[dangerous_safety]

Doing some simple math:


Lets assume an average seperation between objects more than 1 km across to be 10 AU in the oort cloud and interstellar space, less than the 30 AU suggested previously. This lets us estimate the density of oort cloud/interstellar objects to be 1 per 1000 cubic AU, or one object per 3.35E+27 cubic km.

Let's also assume the front facing cross section of our ship is 100 square km, or 10 km on a side. This is definitely on the larger side, but will illustrate the point.

The distance to Proxima Centauri is 4.24 LY, or 4.01E+13 km. This means during its journey, our craft will traverse through a volume equal to 4.01E+15 cubic km.

Using this, we can find that the expected number of large objects you'd run into is 1.2E-12, or that only roughly one in every trillion ships will run into something of this size.

[Bear]

Right... But where a pebble the size of a wad of bubblegum hits with the force of a nuke, it's not really the distance between kilometer-size rocks that we're worried about.

The colony ship spots the kilometer-plus rocks as it goes by and maybe in a few years somebody shows up to explore them in person or make a new habitat on them.

Or if the colony ship is near maximum population and a tenth or so of them are interested in starting a colony now instead of waiting centuries more for a proper planet near a star, then that group and its equipment get themselves ejected as reaction mass leaving them with a small relative velocity to the rock and the ship with a slightly larger relative velocity away from it. Or if the colony ship has already hived off a dozen colonies this way then they probably need to stop somewhere to resupply with - well, with practically everything - before they go on.

Or if the colony ship has hit one of those nuclear-bomb level pebbles, maybe the whole ship has to dump delta-vee trying to limp toward a rendezvous with one of those larger rocks in order to get some badly needed structural steel for repairs.

[SeanR]

With regard to debris, and running into it with a ship in warp drive.

Would a ship at warp be the same size as in normal space? I have the impression that one of two things would be. Either the ship would wrap space around it, and only the mouth of the distortion would move, in much the manner that Void Ships are described. A moving basement universe. Or, it would stretch out, becoming thousands of times "longer", from the perspective of an outside observer, traveling within its compressed space-time volume at a speed that could be far lower than c, while achieving an apparent velocity that was much higher. Possibly enough so that, as things landed in the compression field, they might have a lower relative velocity to that of the ship, since the ship wouldn't be traveling all that fast, within its compression field, and now that the debris is sharing the field, the ship is only traveling a little faster than it. (if that debris moved an inch, in an hour, in the direction the ship was traveling, then fell out of the field, it might find itself several AU from where it entered the field).

I wonder if a ship at warp might not have a lower apparent density, due to the mass of it being smeared over a fair length, and that maybe that lower density might partially counteract the higher apparent density from traveling at a significant fraction of c. That perhaps a ship stretched to 10,000 times its normal length, might be effected by, at least some, elements of relativity, as if it was traveling at .001c, when it's managed to get its speed up to .1c within its bubble.

It also seems to me that such a stretched-out ship might be harder to interact with from normal-space, and most things wouldn't be in Just The Wrong spot to land in the compression zone, and would therefore be missed, with an inch being quite literally as good as a mile.

I'm spitballing here. I know nothing about this level of physics, and know it. I also understand that, at this level, instinct is Wrong. Very Very Wrong.
My instinct is to treat relativity like sound echoes, and I haven't wrapped my head around why they're different.
And I still wonder if we can use the moment of the "Big Bang" as a, literally, universal reference point, sidestepping causality. Which was my original point. Nothing about stargates.

[stevebowers]

This is the idea behind the Metric Shield. As well as providing a cloud of warp motes that can drag a spacecraft along in real space, the displacement drive or halo drive can affect the characteristics of space directly in front of the ship, creating a 'diverging lens' that tends to push incoming dust and gas away from the vessel. A void drive vessel presumably does the same.
I think that the whole concept of warp propulsion is unworkable unless there is some way to protect the craft using metric manipulation.

I note that Stephen Baxter uses a similar technology in his Xeelee Sequence books; he describes a kind of high-powered conversion drive concept, which he calls the GUT drive, which basically recreates the conditions at the start of the Big Bang to produce an arbitrary amount of energy for propulsion. Spacecraft using this system can accelerate at 1 gee indefinitely, and approach the speed of light quite closely in due course. (Older members of OA may remember that we used to have a drive system called the' GUT drive' back in the early days, which presumably used a similar method). But (of course) such a ship would encounter massive friction from the interstellar medium.
Baxter describes how the problem is solved using a shield of negative energy at the front of the ship, the same negative energy used to keep wormholes open. Basically Baxter is describing a divergent metric shield, probably the best defence against dust and gas at these velocities.

[Bear]

A matter of perspective. The 'diverging lens' you mention that deflects dust and gas away from the vessel is a region of warped space (and time, but mostly space). As observed from a point in front of the ship, the ship is narrow as a needle. As observed from the ship, the space ahead is viewed through a 'fisheye lens' effect.

As seen from the side, I think there'd be "gravitational lensing" off the shield, at a point in front of the ship, more or less as if the ship were following something like a small black hole, but with a volume of compressed space instead of an event horizon.

At least as best I can work it out. Gotta admit I'm not entirely sure how 'warp motes' are supposed to interact with physics, so I'm guessing. If anybody knows better, feel free to correct me.

[stevebowers]

I tried to depict this effect in this image, showing a reactionless drive vessel seen from the side. As seen from the front the ship would presumably appear very narrow.

[weirdspecter]

Hey, folks.

Bit sad that y'all beat me to talking about this, as I was rushing on here after a friend sent me a link to an article about this.

There are, however, some thoughts which occurred to me while reading up on this.

Firstly, it'd be neat if the SFnal dream of faster-than-light travel was solved through this method. The paper itself (https://arxiv.org/abs/2006.07125) does directly mention superluminal travel being possible through this method, as does a lot of the literature talking about this. Of course, this raises all the usual issues of causality, and I'd imagine something like the Unruh Effect would probably destroy any vessel attempting FTL travel.

Secondly, and most importantly for the OA setting, both the mass and energy requirements laid out in this piece of work sound far, far more reasonable than the requirements of the void/alcubierre bubbles we described in our various reactionless drive pages. The positive mass described is considerable (though the author believes it can be reduced by as much as 60 ORDERS OF MAGNITUDE!!!) but the drive requires no finnicky, high S-Level exotic matter. If these drives work for subluminal travel (and they seem to be about as plausible as the alcubierre-natario metric?) they might:

- A) drastically reduce the mass-energy requirements for the creation of reactionless drives
- B) possibly place the manufacture of at least some of these drives within the hands of, if not modos, low transaps?

At the very least, some classes of reactionless drive may fall within the purview of High-S Ultratech (that is, ultratech provided by S4+ archai), which would allow modo polities to build their own reactionless ships, revolutionising travel.

Would love to hear folks' thoughts on this -- especially if we can get the bat signal working and call in Adam Getchell to take a look at the physics!

[Drashner1]

Hey, folks.

Bit sad that y'all beat me to talking about this, as I was rushing on here after a friend sent me a link to an article about this.

There are, however, some thoughts which occurred to me while reading up on this.

Firstly, it'd be neat if the SFnal dream of faster-than-light travel was solved through this method. The paper itself (https://arxiv.org/abs/2006.07125) does directly mention superluminal travel being possible through this method, as does a lot of the literature talking about this. Of course, this raises all the usual issues of causality, and I'd imagine something like the Unruh Effect would probably destroy any vessel attempting FTL travel.

I wouldn't be too sure about the Unruh Effect since - technically speaking - anything inside a warp bubble is at rest and the bubble itself isn't really moving in the conventional sense of the word. Space-time itself is not really subject to the same rules of physics as everything inside space-time, which is part of the reason things like cosmic inflation (and warp drives which use a similar effect AIUI) can allow the universe to expand at a vast multiple of light-speed for a brief time.

It has been suggested - and OA presumes this to be the case - that causality issues would trigger a sort of Visser Effect inside a warp bubble attempt to achieve or exceed lightspeed - basically virtual particle creation goes thru the roof exponentially, flooding the interior of the warp bubble with high energy radiation to such a degree that even magmatter can't survive. Hence, why OA warp bubbles can get tremendously close to c, but can't actually achieve or exceed it.

Secondly, and most importantly for the OA setting, both the mass and energy requirements laid out in this piece of work sound far, far more reasonable than the requirements of the void/alcubierre bubbles we described in our various reactionless drive pages. The positive mass described is considerable (though the author believes it can be reduced by as much as 60 ORDERS OF MAGNITUDE!!!) but the drive requires no finnicky, high S-Level exotic matter. If these drives work for subluminal travel (and they seem to be about as plausible as the alcubierre-natario metric?) they might:

- A) drastically reduce the mass-energy requirements for the creation of reactionless drives
- B) possibly place the manufacture of at least some of these drives within the hands of, if not modos, low transaps?

At the very least, some classes of reactionless drive may fall within the purview of High-S Ultratech (that is, ultratech provided by S4+ archai), which would allow modo polities to build their own reactionless ships, revolutionising travel.

Would love to hear folks' thoughts on this -- especially if we can get the bat signal working and call in Adam Getchell to take a look at the physics!

Speaking editorially, I don't think we'd want to put reactionless drives within the purview of lower S minds. We rather like them as being the tools of the AI Gods and it would also be a lot of work to make such a change.

Also - even if this latest theory turns out to be totally correct - we still don't know how to create a warp bubble and therefore it remains just as plausible that they are beyond human/low transapient intelligence and remain the tools of the AI Gods.

Note that OA does not currently state in the EG exactly how much mass-energy is required to make a warp bubble or how exactly the procedure works - so for all we know this theory is correct and that's exactly what's in play in OA.

Barring some truly definitive RL results (the consensus in physics becomes that this kind of thing is both correct and about as doable for humanity as any other kind of starship if not more so; someone actually builds an experimental rig or even a drive that works; etc.) I think our general approach on this would be to keep an eye on it and let it percolate before making any changes to the OA setting itself.

My 2c worth,

Todd

[weirdspecter]

Hmmm, s'pose that's fair, Todd.

I was thinking back to the legacy drives which were a part of the setting -- things like the differential sail -- which seemed (from the old articles I've found on the wayback machine) to be in the hands of ordinary sophs? I think it's fair to put the magic in the hands of the gods to some extent, it's just a shame we don't get to see more of those technologies precisely because they're largely held above modos and low transaps.

As for mass-energy usage, I was thinking specifically about the article about warp bubble production at different S levels and the extreme requirements involved -- multiple Earth mass black holes orbiting sol-mass holes, knotted cosmic strings, exotic basement universes with gravitational gradients -- if these soliton... drives? can be produced in less extremal conditions, that would at least be interesting for the setting, and would potentially lessen some of the logistical issues of the void bubbles in setting, what with these proposed drives not relying on exotic matter.

Definitely agree on letting it percolate, though -- could be that even though it's passed peer review, this paper is totally wrong. It does strike me as... *optimistic* to say the least that the authors has talked about building FTL drives 'within a lifetime' in some press releases on his work.

[stevebowers]

I think that in the very earliest days of the OA scenario, technologies like the Differential Sail were built by hyperturings - which were just barely transapient. Every polity or megacorp might be expected to have at least one hyperturing, and perhaps a lot of them. Wormholes and reactionless drives were built by megacorps, in the earliest incarnations of OA.

The concept of multiple singularities came along slightly later, and we didn't really assign tech levels to these layers until a couple of years later. So the question of how these abandoned technologies related to toposophic levels is interesting, but irrelevant to the current concept of OA.