Alderson Drive

[Steve]

I've recently begun toying with including in my campaign a method of star travel based on a version of the Alderson Drive, used by Jerry Pournelle in his stories.

 

Here is my take on how star travel works. Once within an "Alderson Point," navigation involves tuning the drive to match the quantum-entanglement resonance of a destination point. A capacitor charge is then used up to initiate jump, briefly collapsing space-time. Failure to tune the drive properly (missing the Navigation roll) still causes the ship to go someplace, just not to the desired destination. I wasn't sure how to show that. A second Side Effect? I am also including Jump Shock as an always occurring Side Effect, but I am not sure how to model it in Hero terms.

 

 

Alderson Drive (Civilian Model):  Teleportation 5m, MegaScale (1m = 10 lightyears; +4 1/2) (27 Active Points); Extra Time (20 Minutes, -2 1/2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), 2 Recoverable Charges (Capacitor Charge; -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), Side Effects, Side Effect occurs automatically whenever Power is used (Jump Shock; -1), Requires A Roll (Navigation Skill; -1/2). Real Cost: 3 Points.

 

Alderson Drive (Military Model):  Teleportation 5m, MegaScale (1m = 10 lightyears; +4 1/2) (27 Active Points); Extra Time (5 Minutes, -2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), Side Effects, Side Effect occurs automatically whenever Power is used (Jump Shock; -1), Requires A Roll (Navigation Skill; -1/2), 4 clips of 6 Recoverable Charges (Increased Reloading Time: 2 Full Phases; Capacitor Charge; -0). Real Cost: 4 Points.

 

Military models have faster navigation computers and more banks of capacitors to use. I'm currently thinking that a charge recovers in an hour, feeding off of the fusion power plant. This means that a civilian model can move up to a hundred light-years every two hours, limited by the Alderson Points along its course. Some jumps may be short and others up to the maximum, depending on the star systems.

 

 

Extended Jump:  Megascale (1m = 10,000 lightyears) (+3/4) for up to 5 Active Points of Teleportation (4 Active Points); Can Only Teleport From Fixed Points Near Large Solar Masses (-2). Real Cost: 1 Point.

 

In addition to the basic drive, each vessel must also buy the "Extended Jump" option, By initiating a jump near a star of eight or more Solar Masses, much further jumps become possible. Such stars act as hubs for trade and exploration, enabling ships to cover the galaxy, so long as they use the right route. I'm also considering that even larger masses would enable even farther jumps, extra-galactic, but that would require a star of many more Solar Masses. I'm not sure what number to set though,

 

 

Alderson Point:  Teleportation: Fixed Location (1 Locations), Area Of Effect (1m Radius; +1/4*), MegaScale (1m = 1,000 km; +1 3/4) (3 Active Points). Real Cost: 3 Points.

 

Stars have varying numbers of "Alderson Points" that they generate around them. They are vaguely amorphous zones that are difficult to detect.

 

 

Natural Spacer:  Life Support  (Immunity: Jump Shock)

 

Some people are immune to "Jump Shock" through either a natural immunity or modified genetics.

[IndianaJoe3]

Here is my take on how star travel works. Once within an "Alderson Point," navigation involves tuning the drive to match the quantum-entanglement resonance of a destination point. A capacitor charge is then used up to initiate jump, briefly collapsing space-time. Failure to tune the drive properly (missing the Navigation roll) still causes the ship to go someplace, just not to the desired destination. I wasn't sure how to show that. A second Side Effect? 

 

I don't think it requires any sort of mechanics - it's just the effect of getting lost. 

[Steve]

I don't think it requires any sort of mechanics - it's just the effect of getting lost.

 

Good point. I don't know what I was thinking.

[pinecone]

For the "mega" jumps how about Pulsars, and/or Black Holes? Maybe one limiting factor is having to travel to such a point "the old fashioned way" at STL. So you can jump close, then travel for a short time subjective, but up to 3 years  outside your light cone...

 

Such a Universe could really benefit from artificial black holes. Micro blackhole might turn out as being a super advanced "portable alderson " For alien super tech and the like...

[Steve]

After some thought, I've revised the jump distances a bit. The military model has greater sensitivity in the drive coils, so it can tune into more distant Alderson Points.

 

Alderson Drive (Civilian Model):  Teleportation 3m, MegaScale (1m = 10 lightyears; +4 1/2) (16 Active Points); Extra Time (5 Minutes, -2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), 2 Recoverable Charges (Capacitor Charge; -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), Requires A Roll (Navigation Skill; -1/2), Side Effects, Side Effect occurs automatically whenever Power is used (Jump Shock; -1/2). Real Cost: 2 Points,

 

Alderson Drive (Military Model):  Teleportation 6m, MegaScale (1m = 10 lightyears; +4 1/2) (33 Active Points); Extra Time (1 Minute, -1 1/2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), 4 clips of 2 Recoverable Charges (Increased Reloading Time: 2 Full Phases; Capacitor Charge; -3/4), Requires A Roll (Navigation Skill; -1/2), Side Effects, Side Effect occurs automatically whenever Power is used (Jump Shock; -1/2). Real Cost: 5 Points.

 

Extended Jump:  Megascale (1m = 1,000 lightyears) (+1/2) for up to 4 Active Points of Teleportation (2 Active Points); Can Only Teleport From Fixed Points Near Large Solar Masses (-2). Real Cost: 1 Point.

 

A civilian ship has one bank of capacitors, and a bank is able to hold enough charge for two jumps. Because of piracy, the second jump is usually held in reserve and pre-calculated.

 

Military vessels have four banks of capacitors and more sensitive drive coils, enabling much greater range. That said, it is possible to mount more capacitor banks and obtain more sensitive drive coils. The above just shows the typical difference between civilian and military vessels,

 

I'm thinking of increasing the charging time for the capacitors, since that is another limiter on the distance that a vessel can travel in a single day, If it takes twelve hours to charge a capacitor bank, then a civilian vessel can move up to 120 light-years per day around normal stars, or up to 12,000 light-years by means of high-mass stars. Such stars are the "freeways" of the galaxy.

 

A military vessel could move 960 light-years per day or 96,000 light-years by means of high-mass stars.

[Steve]

For the "mega" jumps how about Pulsars, and/or Black Holes? Maybe one limiting factor is having to travel to such a point "the old fashioned way" at STL. So you can jump close, then travel for a short time subjective, but up to 3 years  outside your light cone...

 

Such a Universe could really benefit from artificial black holes. Micro blackhole might turn out as being a super advanced "portable alderson " For alien super tech and the like...

 

That's a possibility. My current thinking is that past eight solar masses, the distance increases by a factor of a hundred. Perhaps at sixteen masses or more, it goes up even more. I like the idea of long-distance jumps, but I need to think about how I want the numbers to break down.

[BlueCloud2k2]

perhaps each 8 solar masses increases it by a certain amount.

 

8 Solar Masses: Base distance squared

16 Solar Masses: Base Distance Cubed

 

etc, etc

[Steve]

Another possibility I might consider is if links between Alderson Points have a minimum distance involved. While a jump of up to 20 light-years is possible for a civilian vessel, what if there is a minimum of five light-years? If you can't jump a distance shorter than five light-years (or maybe two parsecs), that would mean no jumps from Sol to Alpha Centauri directly.

[Cancer]

Here is my take on how star travel works. Once within an "Alderson Point," navigation involves tuning the drive to match the quantum-entanglement resonance of a destination point. A capacitor charge is then used up to initiate jump, briefly collapsing space-time. Failure

In addition to the basic drive, each vessel must also buy the "Extended Jump" option, By initiating a jump near a star of eight or more Solar Masses, much further jumps become possible. Such stars act as hubs for trade and exploration, enabling ships to cover the galaxy, so long as they use the right route. I'm also considering that even larger masses would enable even farther jumps, extra-galactic, but that would require a star of many more Solar Masses. I'm not sure what number to set though,...

Careful here. Remember that more massive stars have shorter lifetimes, so that trying to jump to a very massive star (say, 20 solar masses) that you see in any galaxy outside the Local Group will already be gone by the time its light reaches us. For intergalactic jumps I think you may have to target black holes, but the environment around those can vary strongly with time, and can be really, really nasty.

[Steve]

I'm not really going to mess around with extra-galactic jump capability in my planned campaign. The galaxy will be a big enough place to work with, but the players will likely hear about theories using supergiants for longer jumps. In the campaign, larger stars will be hubs allowing vessels to cut travel times, assuming they can make the routing work.

 

I ran some simulations using Astrosynthesis in a ten thousand light-year bubble to see how my distances would determine routes, and I might need to cut things down a bit more, maybe to twenty light-years per jump for civilian vessels and forty-fifty for military vessels. Since Alderson points form in pairs in my setting, I'm also thinking of having minimum distances for jumps, like no smaller than five light-years allowed. I'm still playing with Astrosynthesis to get the right fit for movement rates. I'm already going faster than Traveller, perhaps edging up to Star Trek Warp Five distances per day. I'm also really tempted to increase the capacitor recharge time. For a civlian vessel moving four jumps per day (two jumps, recharge and then another two jumps) is probably about right, giving a distance of eighty light-years per day if I drop jump distances to twenty light-years maximum per jump.

[Christopher]

A fixed point to fixed point FTL rarely needs a rule writeup. The connections are as easy or hard as you want them to be/need them to be at any given time. Even one and the same conenction might have different times to navigate at any one point.

 

An idea regarding the time:

Instead of a time limit on the Engine/teleport, make it the time for doing the Skill Roll wich is largely based on the specific point.

The military nav computers then are giving skill points - both general and to rush the skill roll (using the usuall appraoch used for speedsters).

Or another idea is just giving each point a "difficulty". Civilians normally lack skill bonuses from nav computers so they have to take time to get it right.

 

In addition to the basic drive, each vessel must also buy the "Extended Jump" option, By initiating a jump near a star of eight or more Solar Masses, much further jumps become possible. Such stars act as hubs for trade and exploration, enabling ships to cover the galaxy, so long as they use the right route. I'm also considering that even larger masses would enable even farther jumps, extra-galactic, but that would require a star of many more Solar Masses. I'm not sure what number to set though,

Take the super-massive black holes in the center of the galaxies. Those are plenty heavy. Of course they also have a very messy neighbourhood. With them only eating about 5% of the mass they attract, there is a lot of hot matter and radiation around them. And that is before you include the jet's comming out of both poles.

[Steve]

After some thought, I've revised the drive types into three categories. The Mark I is typically used by civilian vessels and the Mark III by the most modern military vessels.

 

Alderson Drive (Mark I):  Teleportation 10m, Safe Blind Teleport (+1/4), MegaScale (1m = 1 lightyear; +4 1/4) (55 Active Points); 2 clips of 1 Recoverable Charge (Increased Reloading Time: 1 Turn; Capacitor Charge; -1 1/2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), Extra Time (5 Minutes, Only to Activate, -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), Requires A Roll (Navigation Skill roll, -1 per 5 lightyears modifier; -1/4), Side Effects, Side Effect occurs automatically whenever Power is used (Side Effect occurs when character stops using power; Jump Shock; -0). Real Cost: 9 Points.

 

Alderson Drive (Mark II):  Teleportation 20m, Safe Blind Teleport (+1/4), MegaScale (1m = 1 lightyear; +4 1/4) (110 Active Points); 2 clips of 1 Recoverable Charge (Increased Reloading Time: 1 Turn; Capacitor Charge; -1 1/2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), Extra Time (5 Minutes, Only to Activate, -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), Requires A Roll (Navigation Skill roll, -1 per 10 lightyears modifier; -1/4), Side Effects, Side Effect occurs automatically whenever Power is used (Side Effect occurs when character stops using power; Jump Shock; -0). Real Cost: 19 Points.

 

Alderson Drive (Mark III):  Teleportation 40m, Safe Blind Teleport (+1/4), MegaScale (1m = 1 lightyear; +4 1/4) (220 Active Points); 2 clips of 1 Recoverable Charge (Increased Reloading Time: 1 Turn; Capacitor Charge; -1 1/2), Can Only Teleport To  Fixed Locations (Alderson Points; -1), Extra Time (5 Minutes, Only to Activate, -1), Can Only Teleport From Fixed Locations (Alderson Points; -1), Requires A Roll (Navigation Skill roll, -1 per 20 lightyears modifier; -1/4), Side Effects, Side Effect occurs automatically whenever Power is used (Side Effect occurs when character stops using power; Jump Shock; -0). Real Cost: 38 Points.

 

Extended Jump:  Megascale (1m = 1,000 lightyears) (+1/2) for up to 40 Active Points of Teleportation (20 Active Points); Can Only Teleport From Fixed Points Near Large Solar Masses (-2), Can Only Teleport To Fixed Points Near Large Solar Masses (-2), Extra Time (1 Hour, Only to Activate, -1 1/2), Requires A Roll (Navigation Skill roll, -1 per 1,000 lightyears modifier; -1/4). Real Cost: 3 Points.

 

Alderson Point:  Teleportation: Fixed Location (1 Locations), Area Of Effect (1m Radius; +1/4*), MegaScale (1m = 100 km; +1 1/2) (3 Active Points); Perceivable (-1/4). Real Cost: 2 Points.

 

Each recoverable charge represents a full capacitor bank and takes twelve hours to fill, so a vessel can thus make a maximum of two jumps each day. I admit this is a bit like Traveller, just at a much faster rate of movement. A vessel can use up both capacitor banks in a few minutes, but then the capacitors still need to refill and the drive coils cool down. The Extra Time represents the calculation time needed. Mark I drives impose a -1 penalty per five light-years due to their lower drive coil sensitivity, Mark II's are -1 per ten light-years and Mark III's are -1 per twenty light-years. Precalculated course charts are available, only requiring the last few variables of stellar drift and other item be calculated when needed (the charts giving a bonus to the calculation depending on their quality).

 

I shrunk down the Extended Jump to keep things in this spiral arm rather than a full galaxy. Alderson Points come in linked pairs, so jumping from one Supergiant requires going to a paired Alderson Point at another Supergiant.

 

Alderson Points can be found by their EM signature and vary in size. Most are too small to use, the smallest a meter in radius.

[Cancer]

This is a subtle point, and one most people don't recognize, so they don't know they're ignoring it.

 

Not only are stars at considerable distance from each other, but they are also often at different velocities. If your drive doesn't neutralize momentum vectors in the act of jumping across space, then a ship popping into a new system will emerge from the discontinuity with a velocity that's the vector sum of the velocity vector of the ship at the instant of drive trigger at the initial point, plus the vector difference in the two stars' velocities in their orbits around the Galaxy. Even among nearby stars this can be appreciable: for a pretty hard sci-fi game I co-GMed over a decade ago, I worked out that between Sol and 61 Vir (a real nearby sunlike star -- 8.6 parsecs from us -- I picked out to be a host to multiple planets, one of them occupied by another starfaring race) the space velocity difference has a magnitude of a bit more than 100 km/s. (For contrast, Earth's velocity around the Sun is 30 km/s.)

 

Depending on your tech, this could go away magically. I explicitly chose tech that preserved velocity vectors in the jump, which meant that on entry into a system you almost always had a lot of high-thrust maneuvering to do to bring your ship to rest with respect to the star ... depending on your navigation roll and equipment, part of that difference could be "harvestable", i.e., some of your pre-jump velocity vector went into the post-jump velocity you wanted to carry yourself from the end-of-jump point to the inhabited station or planet you wanted to rendezvous with. It makes for an extra navigation hazard in the jump, and depending on your tech can give all arriving ships some hours to days of tedious engine burn to dump the old velocity and get the one that let you move safely through the new system.

 

Between a disk star and a halo star or globular cluster (these will be rather old stars, which might matter for your plot, or might not) the velocities are going to range up to 300-400 km/s.

 

Again, this might not matter for you, if the jump delivers incoming ships to, for instance, zero velocity with respect to the mass creating the jump point. Depends on the tech flavor you want. It can add a dimension of "terrain features" to your star map, since those interstellar velocity vectors are fixed things, and the emergent velocity for incoming ships will be known quantities. Trips between stars which are near each other may not be as economical as long jumps, if their velocity differences are large; this could shape interstellar commerce in interesting ways, if you want that.

[Steve]

Thank you for letting me know about the relative motion issue. I'd heard about it before, but I wasn't thinking about it in this case. I might handwave it, since an Alderson point stays in one place near a star instead of orbiting it, so eliminating the relative velocity between stars might be considered a feature of using them.

[Cancer]

Alternately, the drive might convert the pre-jump kinetic energy into thermal energy, and heat up by an amount that goes as the square of the velocity difference. A large thermal ballast mass might be necessary if this is the tech effect you adopt. It would be a reason for ships to carry a few thousand tons of water, or metal armor, above and beyond what might otherwise seem necessary.

[Tom Carman]

It's been a while since I read the books, but I seem to recall that ships came thru a jump with little relative motion. This became an issue when the Moties started trying to jump out of their system thru the Empire's blockade: the Moties managed to make the jump at some considerable velocity to try to evade them.

[Steve]

I like the idea of thermal energy buildup as a result of jumping, which I might include as part of my general structure about how the drive works. That's probably more realism than I need though. It's probably sufficient for me to say that a ship can jump a maximum of two times a day.

 

I'm not intending to do an exact write-up of the Alderson Drive, but a version that does what I need. Travel can be interdicted at "choke points" this way, allowing me to place patrol ships or bases near some of them.

 

Part of the reason I chose to use Alderson Points as a means of star travel is that the setting is emerging from a Dark Age caused by many of the Alderson Points shutting down across a vast stretch of the galaxy due to a supernova going off in this spiral arm of the galaxy. Smaller, pocket empires were able to form in the chaotic aftermath. Now the different regions are reconnecting, providing an opportunity for exploration and trade.

[DShomshak]

Lois McMaster Bujold's "Vorkosigan" series has similar "wormholes." That interestellar travel is only possible along these specific routes is an important part of the setting: The history of series hero Miles Vorkosigan's home planet was shaped by its sole jump point closing shortly after colonization, leading to the barbaric, centuries-long Time of Isolation; when a new wormhole opened, Barrayar's sole exit route led to the planet Komarr, whose only resource is that it's a hub for several jump-point routes; and after a very bad invasion abetted by the Komarrans, the Barrayarans conquered Komarr to make sure they controlled their own front door, leading to further story-shaping consequences.

 

Since Cancer brought it up, I notice that Bujold's wormholes cancel relative velocity. (It's noted in a couple novels that ships must deliberately move away from the wormhole afterwards, to make sure they don't collide with other ships coming through.)

 

Presumably, the ship's energy gets stored in the five-space vibrations of the wormhole. In one book, someone finds how to pull energy out of the wormhole -- though not in a particularly controllable fashion, and that's not what the people were trying to do.

 

Starships need a living pilot who's had his brain specially wired to interface with the ship's jump drive. Exactly what the pilot contributes is not clear in the stories, but they are necessary: No robot ships. This becomes important in the first book, when the Barrayarans use the technique to cover their retreat from a military debacle. If you detonate a nuke mid-jump, the resulting five-space vibrations block the wormhole for some weeks... which means sacrificing a ship and its pilot. Cordelia Nismith, from the ultra-civilized planet Beta Colony, is gobsmacked that the Barrayarans would use a suicide tactic -- and that a pilot would volunteer.

 

Dean Shomshak

[sinanju]

It's been a while since I read the books, but I seem to recall that ships came thru a jump with little relative motion. This became an issue when the Moties started trying to jump out of their system thru the Empire's blockade: the Moties managed to make the jump at some considerable velocity to try to evade them.

 

Yes, the Empire's ships came to a stop before jumping--for a couple of reasons. First, it's hard to precisely plot an Alderson jump point. If you don't hit it exactly, you burn up a lot of fuel powering the drive...but go nowhere (or more accurately, you jump...then reappear at your starting point). Second, because the jump was hard on both humans and computers. So they shut down all the computer systems and the humans all strap themselves in before the jump. When the humans have recovered, they can start powering up the computers again.

 

Jumps are even harder on the Moties. But they're so darn smart that even so they figured out how to hit the jump points at ludicrous speeds, so they pop out of the destination jump point moving at that same ludicrous speed...not that it helped.