Alternative FTL

[Omnivore]

I'm currently working on an ATU that, like 2300AD, is hard science fiction with an FTL exception. For various reasons, what I wanted, in effect, was wormholes but without their easy to fortify nature. The following is what I came up with:

Lares drive

FTL travel between star systems uses wormhole like constructs. These constructs connect star systems along semi-permanent pathways. Star systems may be endpoints for more than one pathway, but any circular route requires the same exact amount of time to traverse in any direction. Causality protection is enforced through quantum physics making it impossible to create a closed time-like curve.

These pathways have no macro scale physical existence, however the regions for possible entry and exit may be calculated. The pathways exist as a probability function. The pathway access regions have no correlation to the observable universe's relationship between the systems connected. The pathways themselves have no discernible relationship to the observable universe's cartography. A chart of pathway connections forms a nodal network diagram.

Theoretically pathway access regions may be as large as a 250 light second diameter sphere, practically the access regions are smaller due to technological limitations on detection/calculation and exploiting access. Access regions tend to be roughly located near the ecliptic plane of a system at an average distance of approximately 100 stellar radii. Because there is a definite relationship between access regions and local space time curvatures, access regions tend to orbit stars as if they were an actual body.

The Terran name for the pathway access regions is derived from Roman mythology after the guardian deities fathered by Mercury; Lares. The existence of these pathways and their access regions were first theorized in the late 22nd century, but it was not proven experimentally until 2261AD. The mechanism for manipulating space time through the quantum sea and thus enabling practical access of the pathways is commonly known as a Lares drive.

One common, but not quite correct, explanation of the Lares drive by starship engineers is that the drive expends energy to create a 'lever' upon the vast energies of the quantum sea, simultaneously wrapping the vessel in a spherical bubble of space-time and punching a hole in the universe. This transformation reduces the apparent size of the vessel to subatomic scale and injects it into the temporary wormhole before it can collapse. Most serious physicists of the 23rd and later centuries have been known to laugh hysterically at this simplified explanation.

The practical aspects of the Lares drive is that it causes the containing vessel to disappear in one star system and reappear in another at short, finite, but measurable time later. The actual time required for travel through a pathway varies with each pathway but is constant for the pathway itself.

The energy required to activate a Lares drive is proportional to the log of the volume of the containing vessel. While some shaping of the bubble is possible, the more the vessel's volume diverges from that of a containing sphere, the less efficient the drive.

Energy(Mj) = vol * log(vol) / (2 * sqrt(vol / spherical-v))

// OLD: Energy in Mj = (vol / 1000)^3 /(2 * sqrt(vol / spherical-volume))

Drive vol (m^3) = (23-TL)*0.005 per Mj
Available at TL9+ (At TL9 double required volume).
Lares drives mass 2 tons and cost Mcr 0.3 per cubic meter of volume, min size is (25-TL) m^3.
Minimum power required is 1.1*Energy(Mj)/2000 in Mw, this allows activation in 2 x 1000s turns.
Radiators require a surface area equal to drive volume / 3 in m^2.

A cheaper version of the drive is available which uses hafnium instead of tantalum for the drive coils. It costs only Mcr 0.1 per cubic meter of volume but is generally only used with fully automated vessels due to radiation dangers and increased possibility for catastrophic malfunction.

Note: I believe the design constraints make this a CT LBB 2 style system as far as ship sizes go.

Comments and criticisms welcome, thanks!

PS: still a work in progress, especially for the smallest ships

 

[DangerousThing]

A couple of questions:

1. How long does it take a ship to make a simple trip?

2. You mentioned that the wormholes were semi-permanent. How often does a link change? And what is the probability that a colony would become totally cut off?

3. Are some links more permanent than others? And if so, can this be known?

I ask these questions because of the speed of information exchange. With a relatively stable network, mail can be run on an efficient basis. However, if the network changes every few days, things will have to be recalculated.

Also, the type of interstellar government may depend on the network. If a subsector could be cut out of the network at any time, then you'd better trust whoever is in charge of that subsector.

It does sound interesting.

 

[BillDowns]

Sticking solely to the Lares pathways

• You are saying Sol may or may not have a pathway to Alpha Centauri, or Wolf 359, or Sirius, etc
• Does each pathway connect to one and only one pair of stars?
• Is there a relationship between the mass or stellar classification and the number of pathways present?
• How are you preventing the fortification of these pathway entrances/exits?
• Can two ships enter the pathway from opposite ends simultaneously? What would happen in that case?
• Are these pathways destabilized by passage and have to "rest"?
• How many ships can enter a pathway from the same end at the same time?

 

[Omnivore]

A couple of questions:

Thanks I'll try to answer.

1. How long does it take a ship to make a simple trip?

From the perspective on-board the ship, less than a millisecond. From the perspective of an observer in the star system at one of the endpoints, anywhere from 19 to 29 hours, average of 24 hours. (17+2d6)

The variable time part is optional, I've included it contrary to my initial idea in order to give a similar escape mechanism to standard Traveller Jumps. The 24 hour figure is chosen to give something close to the same overall message transit time as in the OTU for distances such as that between the Imperial capitol and frontier worlds.

2. You mentioned that the wormholes were semi-permanent. How often does a link change? And what is the probability that a colony would become totally cut off?

For a normal star, the Lares pathways are stable unless there is a major change in nearby space, for example a nova. For multiple star systems and other anomalies, pathways may not be stable although they may be periodic.

3. Are some links more permanent than others? And if so, can this be known?

Yes and yes in many cases. It is still possible for an unpredicted nova or supernova to affect local space-time such that old pathways may be eliminated and new ones created.

One point I'd like to make is that the Lares pathways are not wormholes. They are pathways where the probabilities are high for virtual wormholes in the quantum foam to connect the pathway end points. Oddly enough while Lares pathways are pure handwavium invention, virtual wormholes and the quantum foam are real physics.

Thanks for your interest

 

[Omnivore]

More questions I'll try to answer.

You are saying Sol may or may not have a pathway to Alpha Centauri, or Wolf 359, or Sirius, etc

This is an extremely hard question for reasons that may not be obvious.

First, not every star may have a viable pathway associated with it. Second, I'm assuming pathways are always longer than 100 light years or so due to the physics involved.

The hard answer deals with: the aphorism at rec.arts.sf.written goes "Causality, Relativity, FTL travel: chose any two.". If you want all three something has to be seriously bent. There are enough theories out there concerning quantum physics that I chose a solution to causality protection that says, basically, the probability of any quantum event creating a closed time-like curve is zero. So giving causality protection a nod, the probability for a virtual wormhole to exist between two points is, at least in part, related to the distance. Another part of causality protection is represented by the chance for drive malfunction.

A side benefit to this is that attacking a world with relativistic kill vehicles becomes rather more difficult.

Does each pathway connect to one and only one pair of stars?

Yes.

Is there a relationship between the mass or stellar classification and the number of pathways present?

There could be, at least it would make for an interesting bit of detail.

How are you preventing the fortification of these pathway entrances/exits?

The entrance/exit regions are generally over or around 100 light seconds in radius. This gives a volume of roughly 1 x 10^23 cubic kilometers. Mining even a small portion of that volume would be prohibitively expensive.

About the best you could do, I believe, is two place stations in the same orbit at the leading and trailing edges of the region.

Can two ships enter the pathway from opposite ends simultaneously? What would happen in that case?

Yes. Each ship's drive brings a different virtual wormhole into existence. I'm assuming the physics involved prevent wormholes from forming too close to each other for any problem to occur. In any event, this is covered under drive malfunction. The odds are against a problem though.

Are these pathways destabilized by passage and have to "rest"?

No. A pathway contains trillions (actually an innumerable number) of virtual wormholes. They exist only as probabilities, that is potentials, in the quantum foam until realized by a Lares drive. After passage of the ship, the wormhole used by that ship collapses.

How many ships can enter a pathway from the same end at the same time?

As many as you can fit in a 100 light second (or thereabouts) radius sphere.

Thanks for the questions Bill, hopefully my answers made some kind of plausible sense or at least exhibit internal consistency.

PS: The relationship between causality, relativity, and FTL travel makes my brain hurt.

 

[jshiggin]

As many as you can fit in a 100 light second (or thereabouts) radius sphere.

Hmm, 100 light second sphere. That's about 30,000,000 km radius, which means maybe 10E23 ships comparable to a (Classic Traveller) Tigress-class battleship.

So, effectively, no limit on number of ships through your wormhole at once?

 

[Omnivore]

Hmm, 100 light second sphere. That's about 30,000,000 km radius, which means maybe 10E23 ships comparable to a (Classic Traveller) Tigress-class battleship.

So, effectively, no limit on number of ships through your wormhole at once?

Correct, although technobabble-speaking only one ship per wormhole ever since they collapse at the instance of exit, just there's a practically unlimited number of useful ones in the regions of the Lares pathway access points.

The game universe model I'm aiming for permits useful but restricted interstellar travel as traditional macro-scale wormholes would give but without the natural choke points at the entrances and exits. On the large scale, the speed of information transfer across an empire the size of the 3rd Imperium would approximate that of the J-6 X-boat network. On the small scale, the total travel times should be about double that of the normal OTU jump time plus maneuver to/from 100D. Main differences are that with the Lares drive most of the time is spent in normal space.

The short hop travel times are a bit of a red herring for purposes of economic analysis except for surface to surface shipping contracts and perhaps for speculative trade. Most high tech, high volume trade, worlds would likely maintain at least one trading center space station near commonly used Lares points.

If it were not for the logarithmic relationship between volume and Lares drive energy requirements, the natural transit model that would arise would likely resemble Dune's in the respect that major shipping concerns would build huge starships that spent their entire operational lives jumping back and forth between two points. Practically every other non-military craft would be carried aboard the Lares drive starships. I believe the logarithmic energy requirement sidesteps this particular specialization although it still would stand to reason that bulk shipping would use the largest economical starships and transfer cargo purely between space station trading centers.

[NOTE]
The Lares drive has evolved a bit and is now the FTL mechanism in the Dark Stars ATU.
[/NOTE]