Glisten

[rancke]

I have been thinking of a ringworld on a much smaller scale, lit by an artificial lightsource in the middle. I've no idea what dimensions would be practical at TL15, but it would (IMO) be a decent substitute for a "real" ringworld.

I thought that's what he meant by a "small" ringworld": a ring city. Basic spinning ring habitat, but with a clear inner wall/roof and a reflector at center to reflect sunlight through the roof of the ring. Dimensions, I think, depend on whether you spin it up or use artificial gravity. If it's not under load, it can be larger. On the other hand, if you're using artificial gravity, you could just make a plate.

Surfing the net I find that others -- many others -- have been there before me with smaller ringworlds, so I can't call dibs on that idea. What a pity.

On reflection, I realize that I'm actually thinking about two quite different concepts. One is a ringworld or Stamford tube that can be built at TL15, and thus possibly to be found in places like Glisten. (Also versions that are practical at lower tech levels).

The other is something built by the Ancients at a smaller scale than a true ringworld, but still huge. Something like the surface area of a hundred Earths, give or take an order of magnitude.

The spinning ring is good for gravity. A 200km diameter ring can generate 1G with 1 rotation per 15 minutes (well, 3 seconds shy of 15). 10000km does it in 106 minutes.

What would be the size of one that rotated in 24 hours?


Hans

 

[aramis]

What would be the size of one that rotated in 24 hours?

1,854,336 km, according to SpinCalc

 

[Carlobrand]

Bah humbug to you too, pal.

???

... I'm not sure that grav technology is needed to lighten the load. A lot of this depends on materials. ...

Whether or not it's needed is not the question. One can obviously build a ring without it. Point was that by not spinning it, or by spinning it minimally, you put less tension on the ring and can build it larger, but then you'd need the grav generators to supply the gravity that people would expect.

This is an interesting site, a forum where people discuss physics issues, in this case the physics of a habitat ring:

http://cosmoquest.org/forum/archive/index.php/t-111850.html

They suggest a maximum radius of 4.2 kilometers for a steel structure under 1G spin, 14 km for a structure all of titanium, with an adequate built-in safety factor. The steel they discuss assumes a tension strength of 680 MPa, halved for that safety factor; they didn't mention the titanium. They also suggest some exotic materials could do a lot better, but the limiting factor seems to be the tension placed on the material due to the spin needed to provide 1 G. One option they discussed was molecular nanotechnology (MNT) - far future stuff, but I've no idea when it might show up on the Trav tech level progression. Anyway, they suggest this stuff could produce tensile strengths in the vicinity of 5 x 10¹⁰ Pa, which being about a hundred times stronger than steel, produces a structure up to a thousand kilometers in radius (somewhat less after figuring in the mass of the stuff and people living on the ring). They also discussed carbon nanotubes, where apparently there is a potential for tensile strengths in the tens of thousands of MPa.

http://en.wikipedia.org/wiki/Ultimate_tensile_strength

Niven's Ringworld, by comparison, encountered a tension stress of 7 x 10¹⁶ Pa according to this site:

http://www.alcyone.com/max/reference/scifi/ringworld.html

An interesting aside was the discussion of metal fatigue and wear, suggesting that whatever the thing is build of, it needs essentially to be able to be "rebuilt" ever 40 years or so in order to replace materials fatigued from stress, the way you'd rebuild a freeway: in short scheduled stretches every year. We might comfortably double that to 80 years, but it still means the structure needs to be constantly maintaining itself at a cost of 1.25 to 2.5% of its base cost every year.

Lacking any information on the base cost of the materials or the labor involved, I've no way to calculate the cost of the structure or the cost of such maintenance. We could perhaps use the High Guard hull costs as a basis. That's Cr100,000 per dTon, implying an annual maintenance cost of Cr1250 to Cr2500 per dTon. That's High Guard, which assumes grav plates and other such tidbits. Gets real expensive calculating real estate that way.

A better model might be MegaTrav, except that leaves you calculating the hull and then the environmental stuff and such separately, and it does some difficult curve thing after 10,000 dTons to generate hull costs, so I don't know if we can extrapolate just by doing multiples of 1,000,000 or would need to determine their cost formula to calculate larger structures. Still, by doing the multiples, at MCr891 for a million dTons plus MCr4200-7000 for the life support (assuming basic and extended, depending on how much is covered by extended), it's a steal compared to a High Guard hull: less than Cr5000-8000 a dTon, implying annual maintenance costs around Cr60-100 to Cr120-200 a dTon. How much it would actually cost per person would depend on how generous you were with the real estate (and how much of that real estate is under extended life support): an acre represents about 900 dTons flat ground. The maintenance rate is already ten or twenty times the higher city real estate tax rates; of course a habitat will have many sources of revenue to pay that charge from, but it will also have additional costs such as staff.

The only Trav exotic material I know of is bonded superdense, but it's an armor optimized for absorbing kinetic and electromagnetic energy. There are likely to be building materials that are optimized for tensile strength, and I have no idea what the upper limit there might be.

This site offers an equation to calculate the maximum size based on the tensile strength of the material:

http://www.zyvex.com/nanotech/nano4/mckendreePaper.html#RTFToC18

By comparison, the Babylon 5 station was a basic barrel - an O'Niell cylinder - about 8 kilometers long and maybe a kilometer wide, housing about a quarter million people.

 

[G. Kashkanun Anderson]

It should be noted that the understanding of most asteroids as shoals of smaller bodies loosely bound together into rubble piles was only realized in the last 18 years or so; it was widely believed in the 1980's that most asteroids would be solid bodies.

And this is actually still the case, at least according to the European Space Agency:

Aside from composition, there are other important differences in the internal structure of the asteroids. Most are solid, indicating that they must have been molten at some point in their existence. Others are 'rubble piles'. This means that they are loose collections of 'pieces', held together by the force of their gravity. These asteroids were formed in collisions.​

Traveller is a product of the eras in which it was written.

In this case I would say it's the mistaken notion of the belt as an H2O-free zone. We now know that is absolutely not the case; in fact, there is some indication that there's more water on Ceres than there is on Earth.

Thus, whether updated science likes it or not, there are big rocks in Glisten, and they are dense and solid enough to tunnel through. From this, we presume that there was a planet there a mere 300,000 years ago, and it got blasted.

I don't get that from that. As I already mentioned, that's certainly a possibility in The Marches, but our asteroid belt is chock full of gigantic, solid bodies, so it certainly can happen elsewhere.

Then again, the Ancients were in our system, too.

I can't help my frowning over the "Gliss-ten" stuff. But it is indeed canon.

You must really hate Boring, Oregon then. And that town in Austria that I can't even mention here for fear of getting a nastygram from the mods.

 

[Ulsyus]

the Elysium station was said to be sufficient to house a half million people. That's 2000 for the first billion people. Manufactured by experienced tradesmen, how many could be completed per year? I imagine that it would be like opening up a new subdivision now and again.

The Elysium station was the one that came to mind for me: something pretty large but not so much so as to be beyond the construction capacity of a TL12 mob.

O'Neill Cylinders can house and feed about a half-million people, based on one conservative set of calculations. At 8 km diameter and 32 km long, they are large and spacious. By design, these are deployed in pairs for counter-rotation. They are like sturdier than torii of any comparable population, and they quite obviously use different lighting set-ups.

If a habitat ring was built, then expanded by adding further rings to it over the years, then eventually an alternative light source would be needed as the edge of the habitat extended away from the center point. After enough additional ring were added the thing would come to resemble an enormous oversized O'Neill Cylinder holding several million people.

Thinking on this, you don't actually NEED a light source at center.
...
Tilt the ring in respect to the star, and use shutters for day/night, and a shiny arced central pillar that focuses to the ring, and you can get a ring that no one aboard really notices the rotation unless they look out the window.

This is what I was thinking of when I mentioned angling it off, as in ensuring its axis of rotation wasn't perpendicular to the direction of the primary from the station, so that the ring itself provides the shadow for the evening. However given your calcs for the period of its rotation that idea falls pretty flat.

 

[rancke]

1,854,336 km, according to SpinCalc

That sounds like Ancients-level technology.

If the structure was 1000 km across, we'd have a surface area equal to 11.4 Earths. Assuming 50/50 land/sea split, we'd get an effective land surface area of 19 Earths (unless I've made a decimal point error somewhere).

That would support a big population, big enough to be a powerful world, but not so big as to be overwhelmingly powerful. Something worth further thought, IMO.

However, if something like that had been built by an Ancient, it would be scaled to Eskaloyt's rotation and gravity¹, which would not be the same as Earth's. It would be necessary to decide on these figures. Slightly less than 24 hours and somewhat less than 1G?

¹ Well, wouldn't it?​

Hans

 

[rancke]

The only Trav exotic material I know of is bonded superdense, but it's an armor optimized for absorbing kinetic and electromagnetic energy. There are likely to be building materials that are optimized for tensile strength, and I have no idea what the upper limit there might be.

I suggest you call it 'bonded supertense' D) and make its tensile strength roughly as much better as bonded superdense is a better armor. Cost it in the same ballpark as bonded superdense.


Hans

 

[Ulsyus]

An interesting aside was the discussion of metal fatigue and wear, suggesting that whatever the thing is build of, it needs essentially to be able to be "rebuilt" ever 40 years or so in order to replace materials fatigued from stress, the way you'd rebuild a freeway: in short scheduled stretches every year. We might comfortably double that to 80 years, but it still means the structure needs to be constantly maintaining itself at a cost of 1.25 to 2.5% of its base cost every year.

Thus providing a renewal of generations of wise-cracking cynics in Water & Power coveralls/vacc suites wearing hard hats/helmets to extend an element of Terran cultural continuity into the future.

A better model might be MegaTrav... The maintenance rate is already ten or twenty times the higher city real estate tax rates; of course a habitat will have many sources of revenue to pay that charge from, but it will also have additional costs such as staff.

This would be where increasing automation, year on year, could eventually produce results that do make it feasible for people to live there. Another option is to increase the population density significantly. Think New York in the mid C19. The idea was explored in the Jovian Chronicles setting as a result of mass refugee migration from Terra, with some interesting ideas on how a society would change some of its values and functions.

Too, the acreage may be expensive, but if the residences are stacked 10 stories high then that's a fair few people that can be accommodated still.

The only Trav exotic material I know of is bonded superdense, but it's an armor optimized for absorbing kinetic and electromagnetic energy. There are likely to be building materials that are optimized for tensile strength, and I have no idea what the upper limit there might be.

The question would be is that the best material for the job, or would an analogous material be developed for habitat construction? You've put up some really interesting points (though I'd seen carbon nanotubes referenced in an episode of The Big Bang Theory recently) but does care need to be taken to avoid getting into a Star Trekian fantasy technobabble narrative?

 

[G. Kashkanun Anderson]

Having checked the GURPS book, I have to note that there is one significant problem/contradiction in their data on Glisten. Whilst they state that the Glisten belt is in Gliss's Habitable Zone, they place the belt at about 0.7AU out from the star. This would be in the warmish area of the HZ for a G3V star, but it simply can't work for a K9V star, which is what the book (and a few other sources I've found) says Gliss is. A K9V is really just a glorified red dwarf, which would mean Glisten would have to be at Traveller Orbit 0 (0.2AU from the primary) if this were the case.

If this placement holds, I think this reduces the odds of Glisten being a blasted mainworld somewhat. On the plus side, it's also way out beyond the frostline, so there should be plenty of water and other useful frozen compounds for Glistenites to exploit.

I also noted in the skimming that Bilstein Yards has a sub-specialty in constructing habitats (in the GURPS, I believe). This is a brilliantly placed factoid, making me appreciate that $2.99 quite a bit more. Surely ("Don't call me Shirley") that hints that Bilstein has taken local contracts -- indeed, it may have started into starships after first being "Bilstein Construction Co." and operating thousands of yellow Caterpillar Modular Space Tractors.

Bilstein Yards is a family-owned, boutique manufacturer of high end starships, specializing in non-streamlined designs. They built the Leviathan class ships, for example. The GURPS book does note that they build the occasional space station and floating grav palace, but it's really not what they're known for.

And space tractors? Definitely not. For that you want Ling Standard Products, three rocks down and to your left. Ask for Eneri.

 

[Carlobrand]

Adding to my previous:

Tunneling offers clear advantages in the CT setting but fewer advantages in the MT setting. In fact, it costs more to tunnel a million dTons than to build a million dTon hull in MT. Smaller places - a base camp for your mining team, a small town of miners - are cheaper by a small bit: mining costs roughly 3/4 what building a hull would cost from about 100 dT through about 10,000 dTons. However, where CT got the life support free with the hull, even the asteroid hull, MT pays for life support equipment, so your asteroid home is a good deal more expensive than it would be in the CT world: a free-floating base would cost only about 4 to 6% more. Figure roughly Cr1000 per dTon for tunneling and then another Cr4200-7000 per dTon for the life support equipment (again, depending on how much of the volume is getting extended life support and how much is just getting air, sealing and so forth).

About the only real advantage is you don't have to worry about the thing flying apart if you fall on hard times and can't keep up with the maintenance - and that likely applies only to that last 10% or 20% of your maintenance budget, since I presume a rotating habitat would prioritize structural maintenance over other maintenance precisely to avoid such a fate. On the other hand, an abandoned asteroid outpost is simply an airless hole for centuries to come; an abandoned ring likely breaks up within a few decades of being abandoned - which most likely means such things would be targeted for planned demolition to prevent their remnants becoming a hazard in space.

 

[Ulsyus]

On the other hand, an abandoned asteroid outpost is simply an airless hole for centuries to come; an abandoned ring likely breaks up within a few decades of being abandoned - which most likely means such things would be targeted for planned demolition to prevent their remnants becoming a hazard in space.

Or it's components could be scrapped if there was any way to reuse the material. If it was a large structure, sections could possibly be cut away and used to build smaller structures.

 

[rancke]

I've dug out my copy of GT:Glisten, and the description seems to imply that most settlements are built with an asteroid as a base. One exception (the only one mentioned) is the main starport.

One thing that annoys me is that there are only two companies mentioned and they both happen to be ones that had been mentioned elsewhere, Bilstein Yards and Barracai Technum. I always find the 'kitchen sink' approach (wherein you use an element just because it exists) annoying. If it had been my choice, I would either have made up two new ones or (if word count allowed) mention half a dozen, of which Bilstein and BT were just two more).


Hans

 

[aramis]

About the only real advantage is you don't have to worry about the thing flying apart if you fall on hard times and can't keep up with the maintenance - and that likely applies only to that last 10% or 20% of your maintenance budget, since I presume a rotating habitat would prioritize structural maintenance over other maintenance precisely to avoid such a fate. On the other hand, an abandoned asteroid outpost is simply an airless hole for centuries to come; an abandoned ring likely breaks up within a few decades of being abandoned - which most likely means such things would be targeted for planned demolition to prevent their remnants becoming a hazard in space.

You don't have to worry much about falling apart of the ring, either. Once the seals rot (and typically, that will be before the metal), you vent to vacuum.

Orbital photos of the apollo lander descent stages and rovers show them still visible and intact... 40 years of vacuum exposure.

Note that steel cables under tension tend to hold well for decades even in atmosphere with little to no maintenance. There are 20+ year abandoned steel buildings that are still structurally sound... Like the MacKay building in Anchorage. Abandoned from 1982 to 2006... now refurbished and reoccupied.
Been condemned twice...

What you won't have is living occupants as after the seals fail.

 

[Carlobrand]

...Note that steel cables under tension tend to hold well for decades even in atmosphere with little to no maintenance. ...

Well, I did say, "within a few decades," although why it didn't occur to me that they could just despin it and leave it there or break it up for salvage, I don't know. Alzheimer moment, maybe.

 

[Travellerspud]

I suggest you call it 'bonded supertense' D) and make its tensile strength roughly as much better as bonded superdense is a better armor. Cost it in the same ballpark as bonded superdense.


Hans

Snort

great name though!

 

[Ulsyus]

You don't have to worry much about falling apart of the ring, either. Once the seals rot (and typically, that will be before the metal), you vent to vacuum.

Orbital photos of the apollo lander descent stages and rovers show them still visible and intact... 40 years of vacuum exposure.

But those metals wouldn't have a fraction of the stresses placed upon them that material in a decommissioned ring or cylinder would have, would they?

I don't know why it didn't occur to anyone that they could just despin the things and leave them there or break them up for salvage, I don't know. Alzheimer moment, maybe.

 

[G. Kashkanun Anderson]

One thing that annoys me is that there are only two companies mentioned and they both happen to be ones that had been mentioned elsewhere, Bilstein Yards and Barracai Technum.

Actually, Hans, there might be one that you missed: The Glisten Coordinating Authority (GCA), the government of Glisten itself.

The GT:Glisten text says that the GCA was originally known as the Gliss Ten Coordinating Corporation, a closely-held spinoff of Liisharara Dii (which itself was spun off from the wreckage of Zhunastu Industries). The early GCA was definitely a for-profit concern, even as it gained legitimacy as the official government of the system. It's profit structure may have changed with the Second Constitutional Convention of 785, but the text is unclear on this, except to say that the GCA switched at that time from a fee-based income generation system to general taxation.

Interestingly, nothing at all is said about how the corporate ownership situation was handled. Were they bought out? Diluted into a public-private partnership? Or are the original owning families still there today, living off dull (but sizable) incomes from quarterly dividends, like little old ladies with utility stocks? I suppose that's up to the referee to decide.

There are also a few historical corporations mentioned on pages 4-5 that I'd never heard of before. But aside from Liisharara Dii/GTCC/GCA, they're all either extinct or booted out of the system.

Oh, and for the record they also mention the First Bank of Glisten and the Glisten Stock Exchange (GTX), which are also previously unknown corporations. But... yawn.

 

[rancke]

Actually, Hans, there might be one that you missed: The Glisten Coordinating Authority (GCA), the government of Glisten itself.

For various subjective reasons I don't count them or the others you mention.

BT might be powerful enough to rate a mention at the level of detail covered by the book. There's no reason why they should be, but no reason why they shouldn't, so put it down to a not too strange coincidence that they rated a mention (I'd still argue that there must be other subsector-wide companies in Glisten that rival BT, not to mention sector-wide companies with a presence in the system). But be that as it may, Bilstein Yards are definitely small fry (Comparatively, that is). The only reason for mentioning them and not one of a score or a hundred of others is the meta-reason that they were mentioned in previous published material.


Hans

 

[G. Kashkanun Anderson]

For various subjective reasons I don't count them or the others you mention.

BT might be powerful enough to rate a mention at the level of detail covered by the book. There's no reason why they should be, but no reason why they shouldn't, so put it down to a not too strange coincidence that they rated a mention (I'd still argue that there must be other subsector-wide companies in Glisten that rival BT, not to mention sector-wide companies with a presence in the system). But be that as it may, Bilstein Yards are definitely small fry (Comparatively, that is).

I'd say Bilstein still merits a mention based on their reputation as the go-to manufacturer of yachts for the high nobility of the Marches, up to and including Archduke Norris. Basically, everybody spinward of Deneb knows that owning a Bilstein yacht means you've Made It.

Yeah, this effectively means Baraccai Technum were cruising around the 'Outrim Void' in the Far Future equivalent of a space Maserati. Maybe that was their way of telling the other merchant lines that they were now a force to be reckoned with?

Also, for what it's worth, GT:BtC mentions a colony world in District 268 (Binges) that was basically foreclosed on by the First Bank of Glisten, so there is canonical evidence of it having pull in that subsector, at least. And New Rome (SM 1938) is run from Glisten, so the GCA isn't precisely confined to its home system. Another world (Aster/SM 1739) is run by Glisten Mineralogical LIC.

These are straws, sure; but they're not nuthin'.

 

[Aramais]

Also, for what it's worth, GT:BtC mentions a colony world in District 268 (Binges) that was basically foreclosed on by the First Bank of Glisten, so there is canonical evidence of it having pull in that subsector, at least.

Oooh...A chance for a repossession adventure. "Get those mutated cattle into the ship -now-, Farmer."

On a more serious note...this could spawn a "Grapes of Wrath" in space.