Artificial private world

[rancke]

I've been thinking about how big an artificially constructed world with a habitable surface might be, and find myself unable to reach any useful figures.

Concept:

An asteroid with a diameter of miles, possibly many miles.
Covered by grav plates underneath a layer of soil.
Surrounded by a transparent bag that holds the air in.

Alternative sizes:

Unique: So big only one multi-quadrillionaire in the Imperium has ever built one.

Big: Something a number of multi-quadrillionaires have, but still so expensive that a lot haven't.

Meh: Something most self-respecting multi-quadrillionaires have.

What would you consider plausible, or not entirely implausible, sizes? I'm not looking for actual construction prices, just ballpark sizes.

Note: One problem is that I don't know how rich the Imperium's richest people are. I say multi-quadrillionaire, but for all I know they could be hexilionaires or heptillionaires or more. Basically I'm thinking of, say, the Imperium's Top Thousand umptillionaires.


Hans

 

[CosmicGamer]

What would you consider plausible, or not entirely implausible, sizes? I'm not looking for actual construction prices, just ballpark sizes.

Large size implausible? None?

Too small to be plausible? Needing a stellar body instead of having a habitat or ship built to suit your needs is the "poor" mans option.

Note: One problem is that I don't know how rich the Imperium's richest people are. I say multi-quadrillionaire, but for all I know they could be hexilionaires or heptillionaires or more. Basically I'm thinking of, say, the Imperium's Top Thousand umptillionaires.

In the version of Traveller I predominantly use the government codes allow, among other things, for some rich person to own and act as dictator of an entire planet and have the entire resources of the world at their disposal. So I'd think no size world, moon, or asteroid would be outside the realm of plausibility as it could possibly generate the revenues needed for construction and the current assets of the ruler are not as relevant as the future earnings potential.

I'd say one plausible limit is based on the science - at what point is an object large enough that it creates enough gravity that grav plates are not needed and the atmosphere can be sustained? Although one could make a case for a large dense world being covered in grav plates that lower gravity to normal and have habitats with survivable atmosphere that isn't as dense.

Another question is time, if this is to be a barren rock and one needs to start from nothing and construct it within their lifetime vs taking over a stellar body that is populated and has housing, hydroponic farms, mining, manufacturing, and other facilities already in place that would be needed to support a large effort...

 

[Limburger59]

...Surrounded by a transparent bag that holds the air in.

I can't imagine this working, even enclosed in a ball of transparent aluminum. Even if you discounted the danger of a puncture, the stellar radiation would make it sterile.

I could see a large space station with the first level being a dome enclosed park.Then it could be rotated away from the system's sun during solar flare activity or when passing through a region like the dust "cloud" that causes the Perseid meteor showers.

 

[robject]

Figure out the estate volume, as a set of ship "modules", first. Then get a planetoid towed to the starport for finishing.

A sufficiently large planetoid may be tunneled out at a relatively low cost. Just specify that most of it is NOT tunneled out, but rather just the layout of whatever size estate you'd like (and need for life support). Fit it with an M-drive and power plant, perhaps.

The estate itself is designed as a modular starship, so the grav plates are in the decks, but partially buried into the planetoid (hence the tunneling). A big rad- and flare-protected dome over the crater recreation lake (yes, another "ship" module I guess) would make for a stunning view. Oooh, and don't forget the hangar bays.

 

[rancke]

The estate itself is designed as a modular starship, so the grav plates are in the decks, but partially buried into the planetoid (hence the tunneling). A big rad- and flare-protected dome over the crater recreation lake (yes, another "ship" module I guess) would make for a stunning view. Oooh, and don't forget the hangar bays.

I'm not interested in alternatives. I want a miniature pseudo-world with the illusion of a planetary surface.


Hans

 

[flykiller]

why are you considering this? what purpose and/or role would such a world serve? who would pay for, build, and use this?

 

[rancke]

why are you considering this? what purpose and/or role would such a world serve? who would pay for, build, and use this?

Very rich people who want a private mini-world.


Hans

 

[Carlobrand]

I can't imagine this working, even enclosed in a ball of transparent aluminum. Even if you discounted the danger of a puncture, the stellar radiation would make it sterile. ...

Why? One presumes that if you're going to build the thing, you're going to build safeguards against radiation. Big threat is ultraviolet - there are ways to screen that. Then there's the solar wind - that can be handled too. Solar flares are an issue - massive burst of ionized matter and electromagnetic radiation. That hasn't sterilized Earth.

By coincidence, we're discussing a related question in one of the other forums: can you hold an atmosphere around a ship in space using the tech available in Trav, so that an occupant could go outside and do work without being encumbered by a spacesuit. Nearest we can figure, answer seems to be yes - if you're willing to give it an atmosphere that may extend 80-90 kilometers out from the ship. That last, though, is a killer.

Critical hinge point seems to be gravitics. If you see the grav field as limited to a deck, then you can't build multi-kilometer atmospheres on your planetoid. If you do not - if the floor plate grav field extends upward and beyond the ship that's using it, or if you think grav manipulation technology makes that possible even if the ships presently aren't doing that - then you can. It just takes an incredible lot of effort.

Total mass of earth's atmosphere is about 5.1 to 5.5 x 10¹⁸ kg, depending on your source, which I think depends on how high they're going before they stop counting wisps and traces. Let's go with 5.5 for a spherical shell standing out about 100 km from a (mostly) sphere of about 12,700 km diameter.

http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html

Let's see, 4/3 Pi R³, R is 6371.0, Vol=1,083,657, 777,102.
R is 6471, Vol= 113,442,750,464
R2-R1=50,784,973,362 cubic kilometers. That's roughly the volume of terrestrial atmosphere.

We're going to presume gravitics technology gives us the means to simulate gravity the same way it operates on Earth - i.e. decreasing with range by inverse square of distance. It's a sci fi game, we've already got gravitics, we can stretch credulity just a bit more to do that. We're also going to presume our rich guy has the means to lay down and power all the gravs needed to hold an atmosphere around a little planetoid. That's an impressive level of wealth, but some of these people control megacorps with balance sheets that dwarf the GWP of the largest worlds. So, how much atmosphere does he need for, say, a 1 Km radius asteroid?

4/3 Pi R³, R is 101.0, Vol=4,313,527 cubic kilometers, less the volume of the asteroid, so about 4,313,523 cubic kilometers. That's 0.000085 the volume of Earth's atmosphere, or 4.67 x 10¹⁴ kg. 467 trillion tons of atmosphere.

Is it doable? Yes, the same way it was doable for the Pharoah to build the temple: by a massive commitment of resources over a very long time. I don't know what kind of shipping tonnage our rich man has access to, but we're basically talking about spending hundreds of quadrillions of credits on a project that would take roughly 20,000 200,000 ton freighters 2000 years, give or take a bit, assuming you're borrowing atmosphere from a handy earthlike world in the same system. At the end of which you would have a planetoid with an artificially maintained Earthlike atmosphere.

By way of comparison, there's about 20,000 ships in the Imperial Navy. So, we're talking the wealth and power of a dynasty of several emperors, maybe.

Of course, that's doing it the hard way. Plan B - anything that involves a roof to cut down on the amount of atmosphere you need and to take over the role of protection against solar flares and ultraviolet and such - is quite a bit cheaper and easier. Take your 1 km radius asteroid, add 10 meters of air so you can have short trees, that's only adding 0.127 cubic kilometers of atmosphere: 127 million cubic meters. About 165,000 tons of air. Of course, what you're really building at that point is a nonmoving ship with an unusual outer hull and an asteroid inside it.

 

[rancke]

Critical hinge point seems to be gravitics. If you see the grav field as limited to a deck, then you can't build multi-kilometer atmospheres on your planetoid. If you do not - if the floor plate grav field extends upward and beyond the ship that's using it, or if you think grav manipulation technology makes that possible even if the ships presently aren't doing that - then you can. It just takes an incredible lot of effort.

I do assume that artificial grav fields can be created by just floor plates, so that you don't need something on top too. But I don't espect the field to keep the atmosphere; that's what the "airbag" is for. I'm thinking perhaps a kilometer above the surface. Less if that's not feasable.


Hans

 

[Timerover51]

Something like that should be a magnet for every assassin, terrorist, anti-Imperial group, Sword World raider, Aslan raider, and Vargr corsair in the sub-sector. Just think of the prestige some group could get for knocking it out or taking it over.

 

[flykiller]

Very rich people who want a private mini-world.

oh. well, then it will be as big as they can afford.

seriously, you might want to put it in the category of "if you have to ask then you can't afford it." just design it as you like, and leave the rest to the robot accountants.

 

[McPerth]

IMHO it will depend on many variables:

• How many people is assumed to live there?
• Will it be a world or a starshio (so that, will it have maneuver drives or not)?
• It's assumed to be self-sustained or have regular replenishements (water, air, food, etc...)?

If it is assumed to have MDs, then I guess that will limit the size, as my guess is there's a limit for them (more so if it is not a closed structure, as it seems to be the case). For now I'll asume it won't being just another planet in the system (with the orbit closely calculated for the planet to keep a comfortable temperatura, the heat incoming from star being more or less equivalent to the one radiated to space, mostly by the dark (night) face (that can vary if the "planet" has rotation, as told below).

Also if you want it to be self sustained, this will impose (I guess) a minimum surface for flora to replenish the atmosphere and dispose the wastes (and to produce food), as well as enough water to allow this flora to survive (and probably will want some time of weather simulating with this water). The size of it will in part depend on how many people (and animals) lives on it. Some rotation will have to be given if you want a day/night cycle.

Another thing that night impose a mínimum size would be how far do you want horizon to be (to give you open air feeling).

I can't imagine this working, even enclosed in a ball of transparent aluminum. Even if you discounted the danger of a puncture, the stellar radiation would make it sterile.

I could see a large space station with the first level being a dome enclosed park.Then it could be rotated away from the system's sun during solar flare activity or when passing through a region like the dust "cloud" that causes the Perseid meteor showers.

As we must asume quite high TL here, I guess some kind of matherial (probably some transparent bonded superdense one) will be available. Also, i might be Meshed with a gird (not unlike the one for JDs in MT) that might imitate the magnetosphere, and probably have solar pannels that can power the "planet" (probably through rectenna transmission).

Critical hinge point seems to be gravitics. If you see the grav field as limited to a deck, then you can't build multi-kilometer atmospheres on your planetoid. If you do not - if the floor plate grav field extends upward and beyond the ship that's using it, or if you think grav manipulation technology makes that possible even if the ships presently aren't doing that - then you can. It just takes an incredible lot of effort.

I do assume that artificial grav fields can be created by just floor plates, so that you don't need something on top too. But I don't espect the field to keep the atmosphere; that's what the "airbag" is for. I'm thinking perhaps a kilometer above the surface. Less if that's not feasable.

Even if grav plates are needed both over and under the gravity field, the envelope as told above could handle this...

Something like that should be a magnet for every assassin, terrorist, anti-Imperial group, Sword World raider, Aslan raider, and Vargr corsair in the sub-sector. Just think of the prestige some group could get for knocking it out or taking it over.

Nowere I have read it cannot be armed. If could even have deep meson guns, for what is told to now...

Another thing to discuss is hot to get in/out of it. IMHO it would be cool to have a beanstalk that lifts you to a "space station" in the envelope itself, where incoming ships could be parked.

And it could be called B612 (Le pétit Prince, by Saint-Exupery) .

 

[robject]

I'm not interested in alternatives. I want a miniature pseudo-world with the illusion of a planetary surface.

As it says on the tin, in other words. Okay then.


EXECUTIVE SUMMARY

Surface: Estimate the surface area in square meters and multiply by KCr 100, for the cost of installing grav plates. For every 7 meters of dirt added on top of this ("reverse tunneling"), add 1% to the cost.

Dyson Dome: Estimate the surface area of the dome in square meters and multiply by KCr 100, for the cost of a transparent flashproof, radproof, reinforced stronger-than-starship-hull spherical enclosure for protection and holding pressure. For worlds (Size 1 and up), re-use the world surface area. Atmosphere "installation" is 1% of the cost x Atmosphere digit, assuming atmosphere can be transported in a compressed way and (where possible) mined locally.


NOTES

My suggestion is to work it backwards: back-of-the-envelope calculations for a price, then set that price as something only 1,000 sophonts in X sectors of Charted Space could afford. Scale to taste.

First assumption: costs for tunneling a planetoid approximate the cost for layering sod over the crust of a world, ton for ton.

Second assumption: costs for installing grav plates (let's call them "solar satellite powered" just for convenience) are Cr100,000 per square meter, or something that sounds appropriate.

Calculations: your back-of-the-envelope costs are therefore going to require (1) knowing the sub-surface area of the worldlet for grav plate installation, and (2) knowing the volume of earth to be transported and "installed".


Make it a Size 1 world; 1,600 km diameter.

Surface area is 4 x pi x r x r, or roughly 12 x 1,600,000 x 1,600,000, or 30,000,000,000,000 square meters. At KCr 100 per square meter, grav plating is MCr 3,000,000,000,000. Or, BCr 3,000,000,000. Or, TCr 3,000,000.

Now we'll layer on a surface. Call it 14 meters on the average, making each square meter of surface 14m tall on average, i.e. one volume ton of dirt, rocks, whatever.

Dirt at Cr 1000 per ton for transport, and Cr 1000 for "reverse tunneling" (? Can't remember the actual number) at 30,000,000,000,000 tons, is therefore another MCr 60,000,000,000, or BCr 60,000,000, or TCr 60,000. About 2% of the cost of grav plating.

In other words, the grav plating is the actual cost. A competitive distributor might throw in the dirt for free.


Anyway, for a Size 1 world, just the grav plates and topsoil cover would cost on the order of 3 x 10^18 credits (did I get that right?)


I suppose we can't assume that the grav plates will help hold an atmosphere. Hence, the bag. Maybe Carlo has reasonable numbers for that in his post. Otherwise, assume a transparent structure, as strong as a starship hull, that encloses the Size 1 world at an altitude of... well how about 1 km? In other words, its surface is roughly equal to the world's surface, which we've calculated as 30,000,000,000,000 square meters. Call it 2,000,000,000,000 tons of solid transparent starship hull. Now make a big assumption that 1 ton of starship hull material costs MCr 1. Then the cost for this mini Dyson Capsule world is MCr 2,000,000,000,000, or BCr 2,000,000,000, or TCr 2,000,000.

In other words, the cost for holding in the air is about equal to the cost of the grav plating, depending on what the back of your envelope says (these numbers are sensitive to initial conditions).

Expect to pay TCr 6,000,000, or 6 x 10^18 credits, for a Size 1 world makeover.

 

[robject]

[FONT=arial,helvetica]Example: 100 km planetoid.

Surface: area estimate = 4 pi x 100,000 m x 100,000 m = 120,000,000,000 sq m.

MCr 120,000,000, or TCr 120. Add 21 meters of dirt for TCr 3.

Dyson Dome at 1km: area estimate = 4 pi x 101,000 m x 101,000 m = 122,400,000,000 sq m.

MCr 122,400,000, or TCr 122.4. Add Atmosphere 6 for TCr 7.3.

Total cost: TCr 253.



Surface: Estimate the surface area in square meters and multiply by KCr 100, for the cost of installing grav plates. For every 7 meters of dirt added on top of this ("reverse tunneling"), add 1% to the cost.

Dyson Dome: Estimate the surface area of the dome in square meters and multiply by KCr 100, for the cost of a transparent flashproof, radproof, reinforced stronger-than-starship-hull spherical enclosure for protection and holding pressure. For worlds (Size 1 and up), re-use the world surface area. Atmosphere "installation" is 1% of the cost x Atmosphere digit.


[/FONT]

 

[robject]

Back Of The Envelope "Top 1000"

The top 1,000 sophonts represent 1/10,000,000,000 of the population, and the most expensive thing they can afford to buy and still pay the bills costs TCr 250 (roughly), then

What's their net worth?

I don't know. What I can say is that they can apparently afford things worth hundreds of trillions of credits.

If I made the wild assumption that they pay that thing off over 80 years, roughly 1/1000 of its value per month, then their monthly payment is BCr 250.

Which means they make more than BCr 250 per month.

So their yearly income is more than TCr 3.

 

[robject]

What would you consider plausible, or not entirely implausible, sizes? I'm not looking for actual construction prices, just ballpark sizes.

Once again I've missed the point of your post.

But, in order to answer your question, I had to do back-of-the-math guesstimation with what I do know about the costs of things, then project those forward to a couple of examples to provide ballpark numbers.

What I think I've found is that the 1,000 wealthiest people probably can afford the mortgage on a 10 km to 100 km planetoid with grav plates, topsoil, and a Dyson enclosure to hold in a shirtsleeve environment, with perhaps a 1km ceiling.

I think this is reasonable, since 1,000 of these habitats won't impact the OTU: they're not everywhere, there's probably less than one per 1,000 star systems.



Now I have to think about more implications. Does that mean there are 10,000 SMALLER habitats, i.e. 1 km to 10 km planetoids? And is that unreasonable? That means a major star system is likely to have a few of these. Is that reasonable? It seems OK, at least at first glance.

 

[Carlobrand]

For the local tycoon on a budget, take a million dTon asteroid, a bit under 150 meters radius, install a maneuver drive and you can collect your atmosphere by dipping into a desirable world's atmosphere and then putting on your roof while you hover. Tack on those exterior gravs and a ceiling, put down your soil and construct your garden; you've got about a 24 meter horizon on the surface, looks like you're standing on the top of a small hill - which you kind of are. Almost 274,000 square meters on the surface, 67.7 acres. Well over 700,000 dTons available in the interior after drives and fuel, for offices, suites, ballrooms, pools and what-have-you, unless you want it buffered, in which case you've got a bit under 600,000 dTons. That's still almost 2000 acres - over 3 square miles inside.

Put it in orbit around your chosen world and let the little people look up at you in envy; at about 100 km you're roughly a third the apparent diameter of Earth's moon, at 1000 you're about as bright as Venus or Jupiter at closest approach. Priced affordably in the 70 billion credit range - unless of course you opt for the luxury interior.

Or, forgo the asteroid and build yourself an 18-hole golf course with 10 or 20 decks of suites and ballrooms and so forth below that. That does have the advantage of being far more visible and impressive when viewed from the world below.

 

[savage]

Gravity with atmosphere generators is a solution, but the ST method was hollow world. The sky touched the top of the mountains and it was forbidden to climb the mountains.

Having a hollow world has two advantages; 1. defense. 2. mobility.
Jumping a planet of any size is problematic, but one with an atmo is probably a few TLs above 3I. Now the sky raiders had a nice idea. I created a pseudo replica of it ages ago.