Working on Tau Ceti for ArcBuilders

[Michael Kilderry]

Yep, the new Thoosa textures look better, more original too. The old low-res looking texture reminded me of another fictional planet I've seen before.

[Dollan]

The old Thoosa was using a highly color-corrected portion of a satellite view of the Sahara. I've noted that the Sahara seems to be a favorite for those who are creating desert or other wise dry planets. In fact, the original texture of the inner world of Tau Ceti, I believe, used a different portion of the Sahara.

But you might be thinking of the texture for Tatooine, which is also using the Sahara.

This texture is actually a portion of an Antarctic ice flow, color-corrected and tweaked a bit. One thing that I should have done was to include an overlay of a cratered region, but for now I'll argue the point that the surface is constantly under the barrage of sand storms, and so craters are buried or erased on a time frame of only a few decades.

...John...

[bdm]

The old Thoosa was using a highly color-corrected portion of a satellite view of the Sahara. I've noted that the Sahara seems to be a favorite for those who are creating desert or other wise dry planets. In fact, the original texture of the inner world of Tau Ceti, I believe, used a different portion of the Sahara.

It's my favourite too because it's quick and easy.

It's why I'm taking a little more time with my next desert world. Instead of just straight Sahara, I'm blending in bits from other deserts to mix it up a bit.

[Dollan]

Here's a brief image of the primary world of Igom, for Tau Ceti. Because of the system's low metallicity, I assumed more icy material went into the making of the terrestrial worlds, and Igom retianed most of this as water. So the land masses are relatively small. Also, the increased ocean size would, I believe, lead to an increase in cloud cover.

I was tempted to say that the world was, over all, cooler because of the dimmer star, rather than figure in the greenhouse effect of a somewhat thicker and cloudier atmosphere. But I can also offset this by having something of an ice age occuring, I suppose.

Anyway, here's the main planet. I'm still trying to figure out the asteroid belt that Scylla and Charybdis are supposed to be in the middle of.



...John...

[Tech Sgt. Chen]

OK, I know I've been in the dark about a great many things but, what the heck is ArcBuilders? Is it a SciFi show? I haven't watched any television for over two years so, if it is, I wouldn't know. I've seen reference to it here in the forums and even at the motherlode (I think).

[Dollan]

**chuckles** the ArcBuilder Universe is a science fiction setting that I and my wife first created several years ago, when we were in high school. It was, I'm embarressed to say, very Star Trek like. In recent years, I've taken arenewed interest in it, and am working on turning it into a respectable setting, hopefully worthy of publication in one form or another in the relatively near future (I can only get so much done in my spare time).

I've been trying to turn it into something of a "hard science" setting, thogh of course I'm not even close to such a stage. nonetheless, I work on the assumption that if I remain tru to the rules of the setting, then it doesn't matter if I break a few real rules here and there. Some of the things I am avoiding, however, are FTL travel, humanoid or Human-looking aliens, Star Wars/WWII space fights, and other soft science fiction cliches.

A link to the setting is always provided in my sig file at the bottom of my posts. And the site is *always* under construction!

[bdm]

ArcBuilders is broadly similar to the Orion's Arm universe in principle, in that both settings are hard-SF and lack FTL travel, humanoid aliens and the like.

I am also working on a setting with the same broad principles, with a current working title of Canopus Arc. My setting has less technology because it focuses on the beginning of interstellar exploration 1000 years in the future. With less emphasis on technology, I focus more on the social tensions.

Dollan, what is the difficulty that you are having with the asteroid belts? Do you need any help here?

I like the Igom texture, by the way.

[Dollan]

Dollan, what is the difficulty that you are having with the asteroid belts? Do you need any help here?

I like the Igom texture, by the way.

Well, I wanted Scylla Charybdis to be located within a gap, pretty much dead center of an asteroid belt. But the generator I use, courtesy of Cormoran, isn't up to the task. If you'll look back on the first page of the thread, there are a couple of screenshots of the belt as I had it (I think I've since deleted the asteroid ssc file). Not very good.

I've tried to use your generator, but my experience with Excel is pretty much nil, and so far I've managed to do nothing but screw up the spreadsheet.

When it comes down to it, though, I don't know if I could *have* a double body in such a gap, at least not for the presumed age of the system. For a refresher, here's the portion of the ssc file detailing the double planet:

Code: Select all

"ScyllaCharybdis" "Tau Ceti"

   {
   Class      "Invisible"
   EllipticalOrbit
      {
      Period      3.4
      SemiMajorAxis   2.35
      MeanLongitude   10
      }
   }

"Scylla" "Tau Ceti/ScyllaCharybdis"

   {
   Class      "Planet"
   Texture      "Scylla.jpg"
   BumpMap      "Scylla-bump.jpg"
   BumpHeight   1.0
   Radius      4758
   # Mass      0.373
   # Density      0.2164
   EllipticalOrbit
      {
      Period      1.069375
      SemiMajorAxis   2013.071
      Eccentricity   0.0036
      Inclination   26.72
      MeanLongitude   0
      }
   RotationPeriod   25.665
   Obliquity      26.72
   Albedo      0.55
   }

"Charybdis" "Tau Ceti/ScyllaCharybdis"
   
   {
   Class      "Planet"
   Texture      "Charybdis.jpg"
   BumpMap      "Charybdis-bump.jpg"
   BumpHeight   1.0
   Radius      3116
   # Mass      0.093 # Earth masses.
   # Density      0.9487
   EllipticalOrbit
      {
          Period      1.069375
      SemiMajorAxis   8073.929
      Eccentricity   0.0036
      Inclination    26.72
      MeanLongitude   180
      }
   RotationPeriod   25.665
   Obliquity      26.72
   Albedo      0.35
   }

I've been told there are problems with the double planet itself, but I don't want to worry about that until I get this belt hammered out.

And thanks for the comment of Igom/Glaucus (Glaucus was the colonial name, Igom was the indigenous name). It was a quick and easy task, though I'm not really out to make ground breaking add-ons (I'm saving that for some sort of special add-on, someday).

...John...

[bdm]

For a refresher, here's the portion of the ssc file detailing the double planet:

Code: Select all

"ScyllaCharybdis" "Tau Ceti"

   {
   Class      "Invisible"
   EllipticalOrbit
      {
      Period      3.4
      SemiMajorAxis   2.35
      MeanLongitude   10
      }
   }


I think the period and semimajor axis are incorrect here. When I use these figures to calculate the mass of the star, I get a mass of 1.123 solar masses. (M=D3/P2). Tau Ceti has a mass less than that of the sun.

[Dollan]

I was told ages ago that the way to find the planetary period was to cube the semi-major axis, and then find that result's square root.

So... What is the correct method, that I should have been using for the past decade?

Gar, I'm horrible at math, too....

...John...

[bdm]

I was told ages ago that the way to find the planetary period was to cube the semi-major axis, and then find that result's square root.

So... What is the correct method, that I should have been using for the past decade?

Gar, I'm horrible at math, too....

...John...

The formula you have quoted is roughly correct, but only if the central star is a star of 1 solar mass, the period is measured in years, and the distance is measured in AU. If the star is not of 1 solar mass, the mass term must be included.

P = SQRT(D^3/M)

This is only an approximation because the units are somewhat ambiguous. It should be good enough for a Celestia file.

[Dollan]

Well, of course that would make sense, wouldn't it? I should have really caught on to that long, long ago. Even with my genetic predisposition towards math-illiteracy!

Anyway, I don't suppose you have any thoughts on the asteroid belt-planet set up, do you?

Specifically, I have three main tasks as far as I can tell. One is to determine how far from Scylla/Charybdis the belt's edges are. The second is to actually get the belt rendered into an ssc file. And the third is to determine where Kirkwood gaps should go, and to modify the ssc file accordingly.

HOWEVER... the Kirkwood gaps may not be neccessary. I'm not looking to make hundreds of asteroids, but only a representative number, perhaps 50 or so for both the inner portion and outer portion of the belt. With that number, I'm sure no Kirkwood Gap would even be evident.

...John...

[Dollan]

Alright, here's the revised belts around Scylla and Charybdis, utilizing BDM's Excel generator. Scylla and Charybdis' orbit is highlighted. The first view is from above the plane of eccliptic, and the second is from the plane.





Oddly, there are some asteroids that apparently cross the orbits of the inner main planet, Igom, and the outer gas giant, Phorcys.

...John...

[bdm]

Alright, here's the revised belts around Scylla and Charybdis, utilizing BDM's Excel generator. Scylla and Charybdis' orbit is highlighted. The first view is from above the plane of eccliptic, and the second is from the plane.

Oddly, there are some asteroids that apparently cross the orbits of the inner main planet, Igom, and the outer gas giant, Phorcys.

...John...

That's not unusual. Even in the solar system, there are asteroids that cross the orbits of the planets. When I was experimenting with the Asteroid Maker, on one occasion I had an asteroid whose eccentric orbit passed within a few radii of the central star!

If you look closely at these orbits, you will find most of them are inclined, so they don't actually pass very close to the planet. Those few that do pass close to the orbit of a planet may need to have their eccentricities or inclinations tweaked by editing the SSC file to remove this close passage.

[Dollan]

I'm not worried about these "stray" asteroids. If anything, they might provide fodder for stories if they are close enough or of great enough interest.

At any rate, I'm glad that I'm finished with this portion, and very glad that I figured out the spreadsheet. It'll be kind of fun to play around with the thing in future belts as well.

Next up, I need to rework the textures of Scylla and Charybdis themselves. I'm thinking of creating some very large impact basins, reflecting the worlds' history in the center of this belt.

...John...

[Michael Kilderry]

Can't wait to see Scylla and Charybdis. Igom and the Asteroid belt are looking good so far.

[Tech Sgt. Chen]

Sorry for the delayed response and I have to apologize for not visiting your website earlier; there just doesn't seem to be enough time for anything anymore.
Tomorrow was supposed to be a day off for me but, it seems I've been scheduled for tactical training so, it's off to school in the early AM for me.
Wow,
I'm impressed with your site!
The ArcBuilders is no ordinary undertaking as I see it. It's quite contrived and very imaginative! In light of this, I feel a little silly about the inquiry I posted about it. I've bookmarked your site for further exploration since it'll take some time-managing to familiarize myself with it. Great stuff though!

[Dollan]

Thanks for the reply! I'm glad you liked the site; the ArcBuilder setting has been a long time in the making, definitely. There are some things on the site that I'm thinking about changing or in the process of changing, but as you say, it seems like there is no time. And occasionally, I simply have to step back and work on another section of the site so I don't get burned out.

Enjoy your visits to it when you do have time, and sorry about your lost day off!

...John...

[Cormoran]

Greetings folks,

Been off the air for a little while (blame online rpgs)

Dollan, can you do me a favour and email me the problems you've encountered with the belt generator? Hopefully I can fix them quick, since I was aiming to let it out into the wild in the near future. I've made a few modifications already, but it would appear more are in order.

Anyway, the system looks great so far

Cheers,

Cormie

PS: Welcome back Chris, and I'm glad to know you're back too Malenfant

[Dollan]

Hi, Cormoran, welcome back!

Thanks for the comments. I think I emailed you back. I'm just coming off of a case of acute bronchitis, so I might be mis-remembering. The past week has been something of a nasty blur!

Anyway, development of Scylla and Charybdis has been somewhat delayed, but I hope to get back on it very soon.

...John...