How is an Alderson Drive supposed to work?

[SMJB]

Jump points are pretty common, and no wonder--you get to have your FTL while still being able to devoting most of your time to less blatantly magical parts of your story--but Niven and Pournelle went to an actual physicist to get their pseudoscience checked out. So, what's the "theory" that explains how Alderson Drives work?

[Simon_Jester]

There is a fifth force associated with stellar fusion. This creates a potential well around each star, equivalent to the gravitational potential well caused by that star's gravity.

Alderson drive jumps can only be made along geodesic curves of uniform "potential energy" with respect to this fifth force. Fly to the endpoint of such a curve (i.e. on the fringes of your star system), engage the drive, and be instantly teleported to the other end.

At least, that's all Niven himself has ever released. Basically, what distinguishes the Alderson drive is that it cannot readily be used to violate causality (a major advantage of jump-point drives), and does not directly conflict with any established physics. Plus, it assumes the minimum of "new forces," since it relies only on an unknown force that interacts weakly with the others, not upon the existence of entire new dimensions of space, or parallel universes where light is faster, or on the ability to generate spacetime warps.

[Jerry the Vampire]

Yeah, the whole point of asking a physicist to design it wasn't to make it possible it was to avoid unintended consequences like "it's essentially a time machine that you could use to solve anything".

[SMJB]

There is a fifth force associated with stellar fusion. This creates a potential well around each star, equivalent to the gravitational potential well caused by that star's gravity.

Alderson drive jumps can only be made along geodesic curves of uniform "potential energy" with respect to this fifth force. Fly to the endpoint of such a curve (i.e. on the fringes of your star system), engage the drive, and be instantly teleported to the other end.

At least, that's all Niven himself has ever released. Basically, what distinguishes the Alderson drive is that it cannot readily be used to violate causality (a major advantage of jump-point drives), and does not directly conflict with any established physics. Plus, it assumes the minimum of "new forces," since it relies only on an unknown force that interacts weakly with the others, not upon the existence of entire new dimensions of space, or parallel universes where light is faster, or on the ability to generate spacetime warps.

I was kind of hoping there'd be some avialiable rules for how, when, and with which other stars stars form such connections.

Yeah, the whole point of asking a physicist to design it wasn't to make it possible it was to avoid unintended consequences like "it's essentially a time machine that you could use to solve anything".

I fully realize that.

[Simon_Jester]

If Dan Alderson ever wrote the equations for this down, they're not public knowledge so far as I am aware.

Alderson himself is twenty years dead so you can't ask him. Niven and Pournelle are still alive (at the ages of 75 and 80, respectively) and might have it somewhere in their notes... if they cared to share.

[SMJB]

Pity.

[Imperial Overlord]

The Alderson points aren't necessarily at the fringes of a star system. The primary one connecting to the Motie's star system is actually inside a red giant, which is an important plot point for The Mote in God's Eye.

[Simon_Jester]

I stand corrected- although that Alderson jump point is nevertheless considerably more than 1 AU from the star's center of mass... it's just that the star happens to be larger than the entire orbital radius of the Earth.

It would be more accurate to say that the jump points are NOT, for instance, "parked conveniently close to habitable planets." This is an important constraint on ship travel in the CoDominium setting; ships can jump across the light-years very fast, but fly at relatively limited speeds between points in the same system, because there's no artificial gravity and people generally cannot bear any acceleration greater than one gravity (or a bit more on a warship).

[Imperial Overlord]

Three gees was about the limit for long periods of acceleration on ships. Warships can manage higher speeds with human frailty being the largest concern. The highest I recall for a human ship was five gees. Vessel First Rank Galen Diettenger of the Fomoria, a genetically engineered Sauron Soldier, was able to lean forward out of his command chair when the Fomoria was fleeing at seven gees.

[Ultonius]

Three gees was about the limit for long periods of acceleration on ships. Warships can manage higher speeds with human frailty being the largest concern. The highest I recall for a human ship was five gees. Vessel First Rank Galen Diettenger of the Fomoria, a genetically engineered Sauron Soldier, was able to lean forward out of his command chair when the Fomoria was fleeing at seven gees.

While pursuing the lightsail probe, MacArthur managed four gees for three and a half days, with two-minute periods of 1.5 gees every four hours for watch changes, and did seem to be well-equipped for prolonged high acceleration. The crew used mobile 'acceleration chairs', presumably similar to a reclining wheelchair, if they had to move about during the watch. If not, they worked from their cots. The chaplain's and first lieutenant's quarters, and presumably those of other officers, had 'gee baths', with a film of elastic mylar over liquid. There's also a mention of Chief Engineer Sinclair using a 'hydraulic bed' in Engineering, which may be similar to the gee bath.