Gravitational Neutral Points

[RogerCooper]

One of things that bothered me about Traveller was the arbitrary 100 diameter limit for activating the Jump Drive. Shouldn't it be based upon the gravity field in some fashion.

The only non-arbitrary point would be the point where all gravitational fields balance. For example for the Sun/Earth system that would be the L1 point (slightly influenced by the Moon and other planets), where the Sun & the Earth both exert a force of about .004G in opposite directions.

What I am not sure about is how to figure in the effects of the Galactic Core, the Virgo Supercluster and the Great Attractor. Does anyone there have the astrophysics knowledge required?

 

[GypsyComet]

At some point you may realize that, for many people, those details *are* the reason for the handwave of 100 diameters.

 

[phavoc]

You are mixing two different things here. It's not that there isn't any gravity at the LaGrange points - it's that the pull from the two gravity sources cancel each other out locally.

The stated rule for jump drives is a gravity well affects the ability of the jump drive to form a pocket universe (MGT speaking). One could equally argue initiating your jump drive at a LaGrange point is impossible because the two opposing gravity wells rip it apart right down the middle.

Or just wave your hand and make it so.

Either explanation works.

 

[RogerCooper]

I don't like handwaving if I don't need to do it. And the 100 diameter limit creates some other problems. For example, ships have mass. Does the presence of nearby ships interfere with jump drives?

Creating specific points has some interesting effects. You can use more realistic drives than the hand-wave maneuver drive. You probably need to aim very carefully to jump. It may be possible to guard jump points. The rules of Traveller have the flexibility to handle this.

 

[dragoner]

Yes, other masses do interfere with jumping, drop tanks, for example, are destroyed when the ship jumps. Jump shadows, often of larger masses could make problems, such as Antares, or any other super giant, world would be deep inside the 100D limit. That said, the earth moves in it's orbit at around 66,000mph and the solar system moves through space at 515,000mph; though the speeds seem great, the distances are greater.

 

[Rick]

No, you can't use Lagrange points - due to the special nature of these points, all sorts of cosmic rubbish end up there, as well as being a favoured location for solar observation satellites (L1 usually). You really don't want to proudly emerge at a planets L4 point in the middle of a close cluster of big rocks! Don't do it - you know it makes sense! :twisted:

 

[Tom Kalbfus]

Would like to delete this post, but don't know how

 

[Tom Kalbfus]

No, you can't use Lagrange points - due to the special nature of these points, all sorts of cosmic rubbish end up there, as well as being a favoured location for solar observation satellites (L1 usually). You really don't want to proudly emerge at a planets L4 point in the middle of a close cluster of big rocks! Don't do it - you know it makes sense! :twisted:

Lagrange points are useful for something, Stargates! If a stargate is a wormhole, its going to have a certain amount of gravity because you need a curvature of space to make a wormhole. A curvature of space is gravity according to Einstein. This gravitational mass is a relative to a black hole, so you don't want it anywhere near a planet, because if it fell into one, it would turn into a black hole.
Okay so a stargate that is 1 nanometer in diameter would have the mass of 6.73966 x 10^17 kg, this is approximately one 100,000th the mass of the Moon, and for convenience we place this stargate at Lunar L4 or L5. To use this stargate for communications would require a finely tuned x-ray laser of a wavelength less than 1 nanometer to fit through this tiny wormhole. To give you an idea of how much mass this is, it is the mass of Epimethrus.

http://en.wikipedia.org/wiki/Epimetheus_%28moon%29
It is a moon of Saturn that is about 58 km in radius. You accelerate one end of this wormhole to near the speed of light, it is rather straight forward to convert matter into energy if you have a wormhole that is 1 nanometer in radius, simply feeding that matter into the wormhole will convert the mass into energy, and you need a shield to reflect some of the resulting gamma rays in one direction pushing the shield in the other, the gravity of the wormhole will in turn pull on the mass of the shield and drag the wormhole along. Probably by converting a mass equal to that of the wormhole, you can come to a fairly decent fraction of the speed of light, and in a few years you can reach Alpha Centauri. Orbit a satellite around the wormhole, have it convert x-rays to radio waves and you can teleoperate a robot on the surface of a planet in real time.

 

[Rick]

This is not a new concept, Tom - Babylon 5 Jump Gates are positioned at Lagrange points relative to one of the planets in a system; they, however, have 1 big advantage over your wormholes - they have negligible mass.
If you have a body at a Lagrange point with significant mass, it will be pulled away by the orbiting planet/moon, then back again by the other bodies in the system - eventually forming an orbit around the Lagrange point, but not in it. The more mass it has, the more it will be pulled out of alignment with the Lagrange point, so you would need sophisticated computer control and powerful station-keeping drives to maintain its position.
Given this, it would probably be more convenient to place a wormhole generator on a large-mass planet so that the variable increase in mass would have little or no effect on its position.

 

[Tom Kalbfus]

This is not a new concept, Tom - Babylon 5 Jump Gates are positioned at Lagrange points relative to one of the planets in a system; they, however, have 1 big advantage over your wormholes - they have negligible mass.
If you have a body at a Lagrange point with significant mass, it will be pulled away by the orbiting planet/moon, then back again by the other bodies in the system - eventually forming an orbit around the Lagrange point, but not in it. The more mass it has, the more it will be pulled out of alignment with the Lagrange point, so you would need sophisticated computer control and powerful station-keeping drives to maintain its position.
Given this, it would probably be more convenient to place a wormhole generator on a large-mass planet so that the variable increase in mass would have little or no effect on its position.

The wormhole I mentioned has the mass of that Saturnean Moon Epimeteus which has a mass on the order of 10^17 kg, Earth's Moon by contrast has a mass on the order of 10^22 kg, so 22 - 17 = 5, a one followed by 5 zeros is 100,000, so the Moon has 100,000 times the mass of this stargate, which is about the size of ten hydrogen atoms placed side by side, so I think this stargate will be fairly stable in its orbit since it mass is 1/100,000 that of the Moon, and would probably be made in part out of material from the Moon, but all it is capable of transmitting is information, so what you need in addition to this is a matter transporter, You need to transmit all the information related to the object to be transported through the wormhole, you beam this information through and you use it to reconstruct the object being transmitted out of local atoms. If you were already software, you probably wouldn't mind this to begin with, but if you were a living flesh and blood creature you might have some reservations about being transported this way, one possible exception would be a corpse, if you are already dead, you ight not mind having your dead body deconstructed and reconstructed some light years away and then brought back to life. Star Trek uses this already in its setting, though only for short distances. Call it a 3 dimensional molecular fax machine if you like. A stargate with an aperture of one meter would have the mass of Jupiter, so you can see why these things need to be kept small!

 

[Lord High Munchkin]

"I was born in a water-world...".

 

[Rick]

2010 TK7 is an Earth Trojan at the L4 point; ahead of Earth, but in the same orbit. It has a mass of 1.38x10^10 kg, considerably less than the wormhole you describe, but it has an eccentric orbit around the L4 point precisely because of its mass - it really doesn't take much to pull something out of alignment. Most of the rubbish at a Lagrange point is dust and pebbles, small rocks orbiting around it, then bigger ones slightly further out.

 

[Tom Kalbfus]

2010 TK7 is an Earth Trojan at the L4 point; ahead of Earth, but in the same orbit. It has a mass of 1.38x10^10 kg, considerably less than the wormhole you describe, but it has an eccentric orbit around the L4 point precisely because of its mass - it really doesn't take much to pull something out of alignment. Most of the rubbish at a Lagrange point is dust and pebbles, small rocks orbiting around it, then bigger ones slightly further out.

I think we would keep track of a wormhole, considering how difficult one is to make. The one I described is 10 hydrogen atoms wide. A black hole of the mass you suggest would have a radius of 2.047582533341106x10^-17 meters. I use this black hole calculator for determining size by the way: http://hyperphysics.phy-astr.gsu.edu/hbase/astro/blkhol.html
Now the wormhole I'm talking about would need a negative mass of this amount, and a positive mass that was greater than that. The negative mass holds the neck of the wormhole open to prevent it from collapsing into a black hole. My guess is a wormhole would need a positive mass greater than the negative mass inside it that props it open, too much mass and it would collapse into a black hole, too little mass and the wormhole would explode. Every wormhole you enter collects you mass on the receiving end, that is for instance if you weigh 60 kg when you enter a wormhole, your 60 kg would be added to the receiving end of the wormhole, and as you left the other end of the wormhole you would be adding 60 kg of negative mass to the transmitting end of the wormhole, if too much mass or energy travels in one direction the end receiving would collapse into a black hole and the end transmitting would explode and then disappear. The explosion would consist of gamma rays and subatomic particles, the positive mass would still be greater than the negative mass, its just that this positive mass would no longer be sufficient to hold this end of the wormhole together, the other end where everything went into would simply remain as an ordinary black hole going nowhere. So the thing about wormholes is they need to be maintained. You also need to control what goes into and what comes out of these wormholes. You can build a sphere around it, the gravity of the wormhole at the sphere's surface would be 1 g for the comfort of those working at the wormhole station. The station would be a sphere 2140 meters in radius. (2.1 km in radius) I used this gravity calculator by the way: http://www.ajdesigner.com/phpgravity/gravity_acceleration_equation.php#ajscroll

 

[Rikki Tikki Traveller]

Not all of the LaGrange points are stable points. The L4 and L5 points are stable, but the rest of them are very unstable and would not be viable for locations of satellites or anything else and they will not be locations for collecting planetary debris.

The L1 point (between the planet and the sun) is quite unstable and nothing will collect there. I played in a game where the Referee decided that jump points could only form at these L1 points, so in the solar system, there were only a fixed number of places that ships could emerge from FTL (1 for every planet and every moon). He was then able to defend a system since the entrances could be controlled.

 

[Tom Kalbfus]

Not all of the LaGrange points are stable points. The L4 and L5 points are stable, but the rest of them are very unstable and would not be viable for locations of satellites or anything else and they will not be locations for collecting planetary debris.

The L1 point (between the planet and the sun) is quite unstable and nothing will collect there. I played in a game where the Referee decided that jump points could only form at these L1 points, so in the solar system, there were only a fixed number of places that ships could emerge from FTL (1 for every planet and every moon). He was then able to defend a system since the entrances could be controlled.

I think if you need specific jump points, you might as well have artificial jump gates.. Jump drives can jump from anywhere except within a gravitational well, they question is why you would want to change that by creating a choke point? If you want choke points, then stargates are the way to go!

 

[Beastttt]

LaGrange points are a finite number
so it would be too easy to define and blockade them from smuglgers ,pirates and enemy states
better to just hand wave so you can enter or leave from anywhere

 

[Tom Kalbfus]

LaGrange points are a finite number
so it would be too easy to define and blockade them from smuglgers ,pirates and enemy states
better to just hand wave so you can enter or leave from anywhere

One thing I do note, it is really hard to have interstellar borders when you have Jump Drives capable of 1 to 6 parsecs. Ships can't be detected while in Jump Space, and no one knows what's about to arrive, and when it does it is at least 100 diameters from whatever planet, or it could choose to emerge even further away. All a ship needs to do after that is find a place to refuel, the Oort Cloud is one possibility.

 

[InexorableTash]

Yes, borders are are a map fiction that delineate the allegiance of the system mainworlds. You're not going to find navies defending empty hexes that happen to have a line around them.

Deep strikes into territories by deep space refueling light-months away from
observation is also possible. But not a good way to grab and hold valuable territory.

 

[simonh]

LaGrange points are a finite number
so it would be too easy to define and blockade them from smuglgers ,pirates and enemy states
better to just hand wave so you can enter or leave from anywhere

I think there's some value in having a defined number of point that offer the most efficient access to a system, but still make it possible to reach it undetencted if you're willing to put in the extra effort.

If the criterion to emerge from jump/hyperspace is a shallow gravitational slope, lagrange points offer one set of cheap emergence points, but if you are willing to emerge far enough away from the main star anywhere beyond a certain distance will also meet the criteria. Far enough out the star's gravitational well will be shallow enough that you won't need the counterbalancing gravity of a handy planet to flatten it out enough to make emergence possible.

Simon Hibbs

 

[Rikki Tikki Traveller]

I am not making a judgement on whether having a finite or infinite number of access points is the "best" way to go. It is really what the Referee wants for his setting.

Using LaGrange points is a pseudo-scientific way to explain those choke points. Don't want them? Don't use them.

Using Star Gates is another great way - but then you have to explain why a gate is placed in a particular location and not some other place more conveniently located to the main world.