The Smoke Ring

[Tom Kalbfus]

What if we had such a smoke ring in Traveller? We could fix the physics, see below:
http://www.larryniven.net/physics.shtml

Here's a big object: The Smoke Ring. It is a torus of gas circling an old neutron star, created from the atmosphere of the planet within the Ring. Its radius is about 26,000 kilometers and it gets light from the star that both it and the neutron star circle. It holds life. By the way, there is a gas torus around Saturn which one of Saturn's SATELLITES (Titan) orbits within (see Niven's N-Space for details on how he was inspired to create the Smoke Ring).

Being so close to the high gravity of the neutron star, things in the Smoke Ring orbit the star pretty quickly. Niven gives a minimum period of 2 hours, while I get a typical period of a little less than 2 MINUTES (using this equation). I don't know what causes the discrepancy, unless it's a mistake on the author's part (this is the mistake I mentioned e-mailing Mr. Niven about). The mass of Voy is implied to be 0.5 solar mass which is about 1033 grams, but to get the right answer, the actual mass of Voy would have to be much less (about 1/10000th of a solar mass), which is a pretty implausible value for the mass of a neutron star mass.

The first time I gave this talk a student asked how a planet could have survived the supernova that created Voy - it's in the book that the planet came later and also that Voy is old enough that it is not rotating anymore and therefore not sweeping a radiation beam through the Smoke Ring periodically. Good questions though.

One of the life forms common in the Ring is the Integral tree. It's pretty big - people actually live on it. Now when people are simply in the Smoke Ring they're in free fall, but what if they live on a tree? It turns out that tides give an equivalent to gravity. The gravity of the neutron star is so great that the ends of the tree should be in significantly different orbits, but instead they're constrained to orbit together. Therefore anything ATTACHED to the upper end of the tree is moving too fast for its orbit and thus feels an acceleration outward.

Meanwhile, anything ATTACHED to the lower end is moving too slowly for its orbit and is accelerated inward towards Voy. The middle of the tree remains in free fall (otherwise the whole tree would accelerate into Voy or out of the Ring) - it's in the right orbit after all. Another way to think about it is that the whole tree is being swung around Voy, which should result in a centrifugal force outward on any object on the tree, but the gravitational force of Voy cancels out the centrifugal force exactly at the center of the tree, too much on the inner tuft and not enough at the outer tuft.

The equation for the acceleration experienced by something ATTACHED to the tree is remarkably simple - it's just 3 times square of the rotation rate of the tree around Voy times the distance of the object from the center of the tree. In other words, it's just the force that would be felt if Voy didn't exist, and the tree were being rotated around its center at the rate omega, plus the differential force due to change in Voy's gravity over the length of the tree (Thanks to Peter Taylor for pointing out a factor-of-3 error in an earlier version of this talk) [Webmaster NOTE: see some writings of Peter Taylor at http://www.ghg.net/redflame].

Unfortunately while the BOOK REPORTS a maximum force of about 1/5 g at the ends of a tree, I get a force of almost 30 gees - probably because of the same miscalculation that caused the error in the period of objects in the Smoke Ring. However, that problem is easily resolved - just make the tree shorter. By the way, the same tidal force that creates pseudo-gravity for objects attached to the tree makes the orientation of integral trees very stable - each end of the tree is being pulled so that it lines up with the radial vector. If the tree ever got out of that orientation, it would oscillate a bit, but then settle down due to the damping effect of air resistance. We'll talk a little more about stability later, but I should note that man-made satellites orbiting the earth sometimes use tidal stabilization to remain oriented with one axis pointing towards the earth.

I see if you add another 0 to the inner radius of the smoke ring to make it 260,000 km the orbital period at the inner edge becomes 53.8855 minutes. Maybe that is Niven's main error, he dropped a zero!

Here is the corrected Version.
Actually according to the Calctool, http://www.calctool.org/CALC/phys/astronomy/planet_orbit the black part of the ring would be at a radius of 456,327 km which would give an orbital period of 125.293 minutes, which is about 2 hours. So the numbers seem to work. the escape velocity at the center of the black part of the ring is 539.377 km/sec, should be more than enough to hold onto a standard 6 atmosphere. By the way, 26,000 km is about 4 times the radius of the Earth, not quite big enough to fit a gas giant within the torus. You know asteroids within the smoke ring would be a "Belter's Paradise" not only do you have a breathable atmosphere in which to mine the asteroids, the supernova explosion which made the neutron star would have left a lot of valuable heavy metals behind, like gold and platinum for instance! How would you use this in a Traveller campaign?

 

[F33D]

What if we had such a smoke ring in Traveller?

For it to have enough pressure, we'd have to use a different universe than ours. Maybe in Jump Space?

 

[Tom Kalbfus]

If the difference between orbital velocity and escape velocity is the same or greater than the escape velocity from the surface of the Earth, it should be able to hold into an Earthlike atmosphere. Recall that the escape velocity is 539.377 km/sec, at a radius of 456,327 km. Using this circular orbit velocity calculator http://orbitsimulator.com/formulas/vcirc.html I calculate the orbital velocity at this same radius as 381.435 km/sec, the difference is 157.942 km/sec, the escape velocity of Earth is a puny 11.18 km/sec. Seems to me that this is enough to hold at atmosphere in a torus at zero gee. Traveller starships with their maneuver drive, and the ability to reach a change in velocity of 6,048 km/sec with their maneuver drive should have no problem getting into the smoke ring and getting back out of it. Now if you like, you could calculate the net gravity felt at the ends of an Integral tree. They are 50 km long and Niven calculated that there would be a 1/5th g pull at the ends Asteroids are found at the trojan points of the gas giant Gold, that gas giant is primarily made up of nitrogen, oxygen, carbon dioxide and water vapor, it replenishes the gases lost to the torus into space. The thing is the gas envelope extends way out into space to places where the difference between orbital and escape velocity is less. Tidal forces cause the gas giant to leak gases into the smoke ring.

 

[F33D]

If the difference between orbital velocity and escape velocity is the same or greater than the escape velocity from the surface of the Earth, it should be able to hold into an Earthlike atmosphere.

It would only work in a 2 dimensional universe. Not our 3D one. Sorry.

 

[GypsyComet]

That just means you have to blame it on the Ancients and not have F33D at your table. Both of those should be easy.

 

[Tom Kalbfus]

That just means you have to blame it on the Ancients and not have F33D at your table. Both of those should be easy.

Unlike the others, this is not a construct. You start with a supernova explosion, the rate of spin slows down so the pulsar becomes a neutron star. A gas giant gets dragged closer towards the neutron star until it gets torn apart by tidal forces, the hydrogen and helium escapes leaving behind heavier gases, life develops.

 

[GypsyComet]

I have read the books, and I suspect the Smoke Ring as presented there would make for an interesting place to be from. As an oddity to be found during a traditional Traveller game it lacks things. It is a challenging environment because it is so low tech. Once discovered by outsiders the social setting disintegrates rapidly, leaving a bunch of Belters (basically) who have no vacc suit discipline.

 

[Tom Kalbfus]

I have read the books, and I suspect the Smoke Ring as presented there would make for an interesting place to be from. As an oddity to be found during a traditional Traveller game it lacks things. It is a challenging environment because it is so low tech. Once discovered by outsiders the social setting disintegrates rapidly, leaving a bunch of Belters (basically) who have no vacc suit discipline.

So, it also has wildlife and weather, something traditional asteroid belts lack. Also the neutron star is the remnant of a supernova explosion, all the objects in the system and smoke ring were formed after that explosion, out of the material left behind in the explosion. Do you know that all the gold, platinum and other precious metals were created in supernova explosions. Lets say the asteroids at the trojan points in the smoke ring have unusual quantities of gold, silver, platinum, iridium and other precious metals, This would sort of make it like a classic boomtown in the old west, because the atmosphere is hospitable to human life, then all sorts of people would be coming here to mine for gold, and the gold would be sent out of the system in exchange for imported high tech items. There wouldn't be much of a manufacturing base, as labor would be expensive, because most of it would be employed in the precious metal mining industry. There would be towns springing up all over the smoke. ring, and of course thieves and claim jumpers, and some lawmen would have to keep order.

 

[Tom Kalbfus]

this brings me to another subject, how would grav vehicles behave in an environment such as the smoke ring? how would people get around?

 

[GypsyComet]

Also the neutron star is the remnant of a supernova explosion, all the objects in the system and smoke ring were formed after that explosion, out of the material left behind in the explosion. Do you know that all the gold, platinum and other precious metals were created in supernova explosions?

I'm aware of the most common model of stellar evolution and its side effects, yes.

Lets say the asteroids at the trojan points in the smoke ring have unusual quantities of gold, silver, platinum, iridium and other precious metals,

Given how violent supernovas are, this would probably have to start as two systems, the old neutron star and the younger system with Gold. At some point a capture occurred, though you would have to survey stellar velocities in the neighborhood to figure out which one did the capturing. It is certainly possible that the younger sun had some formation help from the explosion of Voy, but it would not be the only contributor.

Also, those heavy elements would need to go through the process of system formation, be concentrated in the mantle during a world's cooling, and get extruded into the planetary crust through magmatic and volcanic processes to actually be economically retrievable. The system as presented never had a tectonically active world to perform that billion-year concentration process.

This would sort of make it like a classic boomtown in the old west, because the atmosphere is hospitable to human life, then all sorts of people would be coming here to mine for gold, and the gold would be sent out of the system in exchange for imported high tech items. There wouldn't be much of a manufacturing base, as labor would be expensive, because most of it would be employed in the precious metal mining industry. There would be towns springing up all over the smoke. ring, and of course thieves and claim jumpers, and some lawmen would have to keep order.

One problem with using the original Smoke Ring for this scenario is the trees. They are sufficiently temporary that they can't be used as settlements, and attempts to log one will be felt by the tree as damage which will cause it to blow. Dangerous business at any TL.

this brings me to another subject, how would grav vehicles behave in an environment such as the smoke ring? how would people get around?

Close to Gold they would be better off, but vehicles that were used across the whole Ring would need to either use reaction drives or full Maneuver drives.

 

[Tom Kalbfus]

But in this case a reaction drive could be a propeller driven aircraft. Also solar energy is continuously available here, the Sun just gets dimmer and brighter over a 2-hour period, but the stars never actually become visible, there is no actual night. There would also be two groups of people here, natives and settlers. The natives are the low tech people who are descended from original shipwreck survivors, might even be from an interstellar ramjet from the Tolkein System. from the crowds source subsector, there were humans on that ringworld that managed to take control of an AI-piloted interstellar ramjet a few millenia ago, that ramjet AI had some other ideas, but the crew convinced it to explore the smoke ring. The crew mutinied and left the ramjet behind. The ramjet could not enter the smoke ring because its field wires would get damaged if it did due to weather, the field wires which generate the magnetic fields for scoping up interstellar hydrogen make it a dispersed structure unsuitable to entering an atmosphere. The ramjet still lingers on the outskirts of the system waiting for its "Crew" to return. The settlers come from the OTU, they are the prospectors mining for gold, silver and other precious metals. To indicate how common gold is, locally the exchange rate is 1 50-gram gold piece exchanges for 1 imperial credit, though out of system gold is worth more. Most of the high tech items are imported, and since there is a lot of gold, they fact that they system doesn't have a high tech manufacturing base isn't a problem, people just mine gold or something else and exchange it for whatever they need, local merchants are happy to make deliveries.

 

[simonh]

Also, those heavy elements would need to go through the process of system formation, be concentrated in the mantle during a world's cooling, and get extruded into the planetary crust through magmatic and volcanic processes to actually be economically retrievable. The system as presented never had a tectonically active world to perform that billion-year concentration process.

Interesting thread, it's been a long time since I read much Niven.

I hate to pick nites as I actualy agree with pretty much everything else you say, but I'm not sure about this point. Many asteroids appear to be metal rich, but don't seem to have been formed for planetary bodies. It's true that planet formation fractionates the material from the orriginal cometary and asteroidal bodies that formed the planet, with heavy metals tending to sink to the core leaving lighter strata at the surface, modulo volcanic activity cycling some heavy metals to the surface. But that also means that metals must have been more evenly distributed in the orriginal source objects, so you would expect the average cometary or asteroidal body pre-planet formation to be very significantly richer in heavy metals that our planet's crust.

This is why some commercial ventures are considering asteroid capture and stripping for resources as economicaly worthwhile. Mainly for platinum as it hits a value/abundance sweet spot.

Simon Hibbs

 

[GypsyComet]

But in this case a reaction drive could be a propeller driven aircraft.

Only for very short trips in the context of the Ring, especially as a low tech solution. If you were to map a travel route on your system diagrams above as anything more than three or four adjacent pixels, it will either be the epic journey of the age or will need higher tech and the ability to go anywhere at high speeds without having to worry about air.

Direct solar power is much lower efficiency than is necessary to drive a vehicle around at speed. Using solar to run props is well below the efficiency of a solar sail, and that's not even taking into account the difference in wind resistances.

For "Treasures of the Voya Madre", I'd say go for it anyway, just recognizing that you've slid well into Pulp.

 

[GypsyComet]

I hate to pick nites as I actualy agree with pretty much everything else you say, but I'm not sure about this point. Many asteroids appear to be metal rich, but don't seem to have been formed for planetary bodies.

...

This is why some commercial ventures are considering asteroid capture and stripping for resources as economicaly worthwhile. Mainly for platinum as it hits a value/abundance sweet spot.

Hard rock mining without a seam of precious metals is a grams per ton proposition now, and that's in favorable environments.

In the case of trojan asteroids, the history of the system becomes important in determining the heavy metals concentrations and arrangements. If, by some miracle, they were around when Voy went nova, they might actually be *plated* on one face, though there is very little chance of it (assuming a larger body got plated then pulverized). By comparison, the free-floating gravel of a peaceful system formation could simply have a "high" molecular concentration.

Of course, if recent theories are the case, our own belt is not necessarily a good example, as it may have been very late forming and subject to unknown factors. We aren't looking all that typical at the moment, so belts in other systems might be richer or poorer.

 

[Tom Kalbfus]

But in this case a reaction drive could be a propeller driven aircraft.

Only for very short trips in the context of the Ring, especially as a low tech solution. If you were to map a travel route on your system diagrams above as anything more than three or four adjacent pixels, it will either be the epic journey of the age or will need higher tech and the ability to go anywhere at high speeds without having to worry about air.

Direct solar power is much lower efficiency than is necessary to drive a vehicle around at speed. Using solar to run props is well below the efficiency of a solar sail, and that's not even taking into account to difference in wind resistances.

For "Treasures of the Voya Madre", I'd say go for it anyway, just recognizing that you've slid well into Pulp.

Actually propeller driven aircraft is much lower tech than you think. Everything in the smoke ring is in orbit, you really can't map much of anything besides the general structure of the smoke ring. You have the planet Gold, You have the L4 and L5 points which are in the ring. Everything in the L4 and L5 points are swirling around and changing positions in relation to each other. Most people live on a matter island or one sort or another, whether it be an integral tree or a forested asteroid or a body of water. the stuff in each lagrange point remain in relatively close proximity. Probably prior to the arrival of more advanced settlers, there was no radio communication, the only way to keep track of stuff was with the naked eye. If you could see something, you could travel there. One type of propeller driven aircraft was pedal powered a pilot would pedal a winged aircraft, the wings are used more for steering than for generating lift, and if you wanted to travel spinward, you'd point your aircraft antispinward in order to slow down, as you slowed down you'd fall towards Voy and pick up speed at a lower faster orbit, the winds at the lower altitude would carry you around the neutron star at a faster rate, that those at higher levels in the smoke ring, and this can be quite fast. Generally, you go lower to go faster and higher to go slower, and the various air currents are in orbit with you, so there is no relative wind. the reason the integral trees are shaped like integral signs is because only the center of the tree is moving at orbital velocity, the lower extremity is travelling below orbital velocity for that level and the wind is whipping past it, the upper extremity is moving faster than orbital velocity and it is whipping past the air. If you want to descend, you slow down and fall towards Voy, and you speed up, you catch up with objects above you, and when you are close enough, you speed up, ascend altitude and slow down to intercept.

 

[F33D]

Everything in the smoke ring is in orbit, you really can't map much of anything besides the general structure of the smoke ring. You have the planet Gold, You have the L4 and L5 points which are in the ring. Everything in the L4 and L5 points are swirling around and changing positions in relation to each other. /quote]

Any solid objects "swirling around a La Grange point" would quickly slow down due to friction of the atmosphere and then collapse towards there mutual center of rotation due to gravity. This would happen to all solid objects orbiting with the "smoke".

 

[Tom Kalbfus]

Everything in the smoke ring is in orbit, you really can't map much of anything besides the general structure of the smoke ring. You have the planet Gold, You have the L4 and L5 points which are in the ring. Everything in the L4 and L5 points are swirling around and changing positions in relation to each other. /quote]

Any solid objects "swirling around a La Grange point" would quickly slow down due to friction of the atmosphere and then collapse towards there mutual center of rotation due to gravity. This would happen to all solid objects orbiting with the "smoke".

They would slow down to match the movement of the air around it, that air is also in orbit. the dynamics is similar to a planetary ring, generally circular orbits are preferred. You don't see rings around Saturn that are elliptical. The air in the L4 and L5 position would swirl around in a vortex, being influenced by the gravitation of Voy and Gold. Lets take L5 for example the air is in orbit around Voy, and is pulled toward Gold by that planet's gravity, the air slows down because it is ahead of Gold in its orbit, as it slows down it falls toward Voy, and it falls toward Voy it speeds up in its orbit and pulls away from Gold, and as it speeds up it pulls away from Voy and then falls toward Gold again. With L4 the air is behind Gold in its orbit, Gold pulls it toward itself speeding it up in its orbit, this causes the air to move further away from Voy, as it moves further away from Voy it slows down and falls further behind Gold, as it falls back toward Voy, Gold speeds up up again to complete the cycle. Relative to Voy the air in L4 ane L5 are swirling around in a vortex 60 degrees ahead and 60 degrees behind Gold. Also the air closer to Voy than Gold moves faster, and the air further away moves slower. If you want to move fast, you move closer to Voy where there is a layer of air moving faster with you, if you go all the way to the inner edge of the ring, an orbit takes 1 hour, if you are orbiting at the distance of Gold, an orbit takes 2 hours. The point is, you don't have to move fast relative to the air around you to get somewhere speedily. Lets say you want to travel 180 degrees around the smoke ring in 12 hours, relative to Gold. Gold makes a circuit around Voy every 2 hours, that means in 6 such orbits you want to end up opposite from Gold, so that means each time Gold traveles 360 degrees, you have to travel 390 degrees. If you are closer to Voy, you have a shorter distance to travel to get there and you are also moving faster along with the layer of air you are in. You don't need to create a sonic boom.

 

[F33D]

Any solid objects "swirling around a La Grange point" would quickly slow down due to friction of the atmosphere and then collapse towards there mutual center of rotation due to gravity. This would happen to all solid objects orbiting with the "smoke".

[/quote]
They would slow down to match the movement of the air around it, that air is also in orbit. [/quote]

Right, at which point they would THEN accelerate towards a common gravitic center of the LOCAL large masses at the L points.

Sorry, INESCAPABLE physics.

So, as I stated, all matter would coagulate at the stable La Grange points. ALL of it.

 

[Tom Kalbfus]

Any solid objects "swirling around a La Grange point" would quickly slow down due to friction of the atmosphere and then collapse towards there mutual center of rotation due to gravity. This would happen to all solid objects orbiting with the "smoke".

They would slow down to match the movement of the air around it, that air is also in orbit. [/quote]

Right, at which point they would THEN accelerate towards a common gravitic center of the LOCAL large masses at the L points.

Sorry, INESCAPABLE physics.

So, as I stated, all matter would coagulate at the stable La Grange points. ALL of it.[/quote]
The reason they don't is that tidal forces hold them apart, for the same reason all the matter in Saturn's rings does not coagulate at a single point. The differences in gravitational pull towards the neutron star exceeds the atmosphere's self-gravitation. As this is a game, I think it does not matter, a science fiction writer thinks it would work, you should take it up with him.

Larry Niven is a successful writer, he sold a lot of books, seems to me that if the idea can work for a series of novels it could also work for a role playing game.

 

[F33D]

a science fiction writer thinks it would work, you should take it up with him.

Larry Niven is a successful writer, he sold a lot of books, seems to me that if the idea can work for a series of novels it could also work for a role playing game.

Actually, Larry doesn't believe it would work in the real world. (nor does he believe that the GP hulls are possible) :lol: He lived down the road from me and we frequented the same small rare books store. Fascinating guy to talk to.