World Sized Starships

[Tom Kalbfus]

In principle, we can design a starship design process for World Size starships. For this, I'll use a new unit of displacement instead of the dton, lets call them xtons, the x is some multiplier times a number of dtons that isn't important right now. As Worldships go there are 10 standard sizes
World
Size
Digit: Volume xtons
1 1000
2 8000
3 27,000
4 64,000
5 125,000
6 216,000
7 343,000
8 512,000
9 729,000
A 1,000,000

The mass of the starship isn't so important, much of its volume can by liquid hydrogen tanks, artificial gravity is applied on the world's surface. A 1g artificial gravity field should be enough to hold onto a standard atmosphere even for a size 1 World starship.
World
Size 1 2 3 4 5 6 7 8 9 10
Drive
XA 2
XB 4 1
XC 6 1
XD - 1
XE - 2 1
XF - 3 1
XG - 4 1 1
XH - 5 1 1
XJ - 6 2 1
XK - - 2 1
XL - - 3 1 1
XM - - 4 2 1
XN - - 5 2 1 1
XP - - 6 2 1 1
XQ - - - 3 2 1 1
XR - - - 4 2 1 1
XS - - - 5 2 1 1 1
XT - - - 6 3 2 1 1 1
XU - - - - 4 2 1 1 1 1
XV - - - - 5 3 2 1 1 1
XW - - - - 6 3 2 1 1 1
XX - - - - 6 4 2 2 1 1
XY - - - - - 4 3 2 1 1
XZ - - - - - 5 3 2 1 1

 

[F33D]

Why bother trying to inhabit the outside of such a ship? You'd just expose people to deadly radiation and have to keep a LONG distance from the system stars you visit.

 

[Tom Kalbfus]

Why bother trying to inhabit the outside of such a ship? You'd just expose people to deadly radiation and have to keep a LONG distance from the system stars you visit.

Planets have a radiation shield called at atmosphere, and a force fields called a magnetosphere. I have a feeling that planets shouldn't accelerate at multiple gees, probably they should only accelerate according to their maneuver drive at 1% to 6% of an Earth gee. Starship planets should be surrounded by geodesic Jump cages, long tubes extend to the surface of the planet and beneath to access the hydrogen under the surface for injection into the jump drive on the cage. The cages have panels that close prior to jump initiation, as you don't want hydrogen mixing with an atmosphere of breathable gases causing combustion. The sky is closed off and artificial light illuminates the planet surface for day while the planet is in jump space. One example of a World Starship is the planet Mongo from Flash Gordon.

 

[F33D]

Why bother trying to inhabit the outside of such a ship? You'd just expose people to deadly radiation and have to keep a LONG distance from the system stars you visit.

Planets have a radiation shield called at atmosphere, and a force fields called a magnetosphere.

We are talking about a starship the size of a planet. Size 1 is your example. The atmosphere thickness on a planet that size would be insufficient. Also, to generate a magnetic field large and strong enough would take a generator comprising most of the mass of the ship.

So, I ask the question again. Why put people on the outside of the ship where they would die?

 

[simonh]

Thruster manoeuvring of a planet sized ship is going to be problematic. For a start the thrust will be transmitted through the structure of the vehicle at the speed of sound for the structural material, which eg for steel is 5km/s so if th vehicle is Earth sized, the front of it won't start moving until over 2000 seconds after the engines at the other end start pushing. The transmission wave will propagate at different speeds in different materials, and different geometries if the same materials, so you'll get shear forces and interference patterns from the structural stresses similar to earthquakes. If you have large fluid bodies like seas or even an atmosphere the motion will cause tides and weather effects. I doubt you'd be able to get away with more than a very small fraction of a G of acceleration without real problems.

If you have gravitic field propulsion though, you can avoid many of these issues. This means a drive which creates a sloped gravity field across a bubble if sace around the vehicle so it 'falls' in the desired direction. Provided the field is highly uniform, this should avoid many of these potential problems.

Simon Hibbs

 

[Tom Kalbfus]

Thruster manoeuvring of a planet sized ship is going to be problematic. For a start the thrust will be transmitted through the structure of the vehicle at the speed of sound for the structural material, which eg for steel is 5km/s so if th vehicle is Earth sized, the front of it won't start moving until over 2000 seconds after the engines at the other end start pushing. The transmission wave will propagate at different speeds in different materials, and different geometries if the same materials, so you'll get shear forces and interference patterns from the structural stresses similar to earthquakes. If you have large fluid bodies like seas or even an atmosphere the motion will cause tides and weather effects. I doubt you'd be able to get away with more than a very small fraction of a G of acceleration without real problems.

If you have gravitic field propulsion though, you can avoid many of these issues. This means a drive which creates a sloped gravity field across a bubble if sace around the vehicle so it 'falls' in the desired direction. Provided the field is highly uniform, this should avoid many of these potential problems.

Simon Hibbs

Well I did envision a sort of cage around the planet, the cage has shutters to let in sunlight when its near a star, the cage also has grav plating, so long as your within the cage you don't feel the acceleration the planet is undergoing, if you are outside it, then you feel the full effects of the accelertion, and I think the acceleration should be slight. Planets are big things, they shouldn't be very maneuverable, a Free Trader accelerating at 1 g should easily be able to catch up with one, maneuver drives for planets should be in the 1% - 6% range, this also makes the size of the maneuver drive about one one hundreth of what it would otherwise be. A fictional example of such a planet is the planet Mongo from Flash Gordon, I'm thinking specifically of that Saturday Morning cartoon, there was a race that was very much like the Aslan from Traveller by the way. I suppose in Traveller terms, the planet is hollow with artificial gravity generators on its surface, also judging by the cartoon, when the planet made its close pass by Earth, it is bigger than Earth, I'd say size 10 perhaps, not the mass of a Size 10 planet of course. The planet after making a Jump would also have to skin a gas giant by orbiting very close and dropping a snorkle into its atmosphere, perhaps with gravity assist to bring all that hydrogen up. About 10% of the planet's volume for each parsec jumped. Now the shutters would have to be closed prior to jump to keep the hydrogen on the outside of the ship, and also so people don't look up into the sky and see jump space, also there is the problem of about a weeks worth of darkness every time the planet makes a Jump. Artificial illumination would be on the inside of the cage powered by the planet's power plant. Hydrogen and an oxygen/nitrogen atmosphere shouldn't mix

 

[ShawnDriscoll]

World-size starships have their own gravity I think. Don't need artificial.

 

[F33D]

World-size starships have their own gravity I think. Don't need artificial.

Yep. Even if just a little as they won't be anywhere as massive as a similarly sized rocky planet.

 

[Condottiere]

Why not just borrow some planet's spare moon, and drill, baby, drill.

 

[F33D]

Why not just borrow some planet's spare moon, and drill, baby, drill.

You wouldn't because of the same reason that it became round. (assuming you are talking about ones that large).

 

[Tom Kalbfus]

World-size starships have their own gravity I think. Don't need artificial.

Well you need a lot of mass to make gravity the old fashioned way. A hollow sphere is easier to push around than a ball of rock, anyway you need a place to store all that hydrogen to fuel the Jump Drive Liquid hydrogen is much less dense than rock. I'd say gravity generators create gravity, not mass, it is still a big ship, so it is massive, it has a rocky crust about 10 km thick, oceans and a store of minable minerals, and multiple races living on its surface, and of course there are the mysterious people who built the artificial planet.

 

[Condottiere]

The size seems to vary from large planetoid upwards, so I would presume a moon would be midway.

I can't see a hollow sphere able to generate anywhere near earth standard gravity.

 

[F33D]

The size seems to vary from large planetoid upwards, so I would presume a moon would be midway.

Earth's moon is all the way. That's why it's round...

 

[Condottiere]

I know of one instance where it detached itself, and apparently, achieved interstellar FTL travel.

 

[Tom Kalbfus]

The size seems to vary from large planetoid upwards, so I would presume a moon would be midway.

I can't see a hollow sphere able to generate anywhere near earth standard gravity.

Why not? Smaller ships have artificial gravity? Just install grav plating on the entire surface of the hollow sphere, and it will have a gravity field just like a planet. Its all handwavium tech anyway, I'm just applying something that was already established for the traveler setting to make hollow spheres with 1 g gravity.

 

[Tom Kalbfus]

Here are the hull and drive tables I came up with.

 

[phavoc]

I dunno about the efficacy of pushing a planet around. It seems so inefficient. Maybe if they were puttering around in O'Neill cylinders it would work out better. Or, if you wanna go that a similar route, mount yourself some Bishop rings around your engine/fuel structure and then you'd be set. Each one would have the surface area of say India. You'd need some sort of torodial mounting mechanism, but it's certainly not impossible to engineer if you can build something like that.

Having multiple ones would allow you to create all sorts of interesting cultures and environments that would replicate all the wildness of a planet with much less material and mass to move around. Heck, if you wanted to you could design your adventures so that the players never left their ship, moving between habitats and cultures and groups all the while staying on the same ship.

You'd need some sort of artificial sunlight, but again that's not a huge problem if you can engineer that to begin with.

 

[Tom Kalbfus]

I dunno about the efficacy of pushing a planet around. It seems so inefficient. Maybe if they were puttering around in O'Neill cylinders it would work out better. Or, if you wanna go that a similar route, mount yourself some Bishop rings around your engine/fuel structure and then you'd be set. Each one would have the surface area of say India. You'd need some sort of torodial mounting mechanism, but it's certainly not impossible to engineer if you can build something like that.

Having multiple ones would allow you to create all sorts of interesting cultures and environments that would replicate all the wildness of a planet with much less material and mass to move around. Heck, if you wanted to you could design your adventures so that the players never left their ship, moving between habitats and cultures and groups all the while staying on the same ship.

You'd need some sort of artificial sunlight, but again that's not a huge problem if you can engineer that to begin with.

See if you could create a Worldship stat sheet just for fun. Not much to detail really.

Lets say the Worldship is called Planet Mongo, the bridge is located at Mingo City, in the Palace of Ming the Merciless. Ming didn't build it, no one knows who did, he just got control of it.

 

[Tom Kalbfus]

Here is a map of the planet Mongo:

As I said before this planet is a starship, it has lots of tunnels underneath, plenty of room for engines, fuel tanks and other things it needs to be a starship.

I think its obvious its not a map of the entire planet. So how big is this planet if each hex is 150 miles? Lets say the hexes are accurate near the equator and the map is part of a mercandor projection. I'll count hexes across to find the circumference. okay, I counted 68 hexes and each equatorial hex is 150 miles across, so how big is this planet? I got diameter of 3246.76 miles, so Mongo according to this map is a size 3 planet about the size or Mercury. What do you think?

 

[Tom Kalbfus]

I stand corrected. Mongo is a size 3 world, not size 10, I suspect like Mercury, it has Mars like Gravity, and it is this gravity that enables Flash Gordon to be such a hero. Ming relies o robot armies according to the cartoon. The cartoon makes Mongo look bigger than Earth, however this map, it covers the full circumference indicates that it is not, unless it is not the complete world map. I'm going to count the hexes from north to south. maybe I'll get a different value.

I counted 46 hexes, north to south, that is 6900 miles, assuming the entire arctic region is not covered, say to 75 degrees north and south, I get a circumference of 16560 miles, divide by pi gives me a diameter of 5271 miles, a Size 5 world, maybe half a gravity on the surface.

I like this number better, gives us some unexplored territory as well. What do you think?