Perihelion initial year

[ete]

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[Geo]

Hi all.
Perhaps a bit late to the discussion, but in case you had thought of putting the real perihee (or perihelion) between Alpha and Beta Centauri ingame, the next one is in 2035 (which makes 2115 the first one at when the colonists have established themself on Planet). So, give or take a few (Earth/Mission) years, a decade or so before the real perihelion would occur wouldn't be a bad year to mark as the initial "increased native life" event.

On the same note, I wonder if it wouldn't be possible to have a one/two-turn randomizer in the onset of the event, as Planet might be just moving away from the approaching 'Hercules' in its orbit around Alpha Centauri A, thus increasing its distance between Alpha Centauri B and itself for the next half planetary year... 

Edit: Oh, almost forget, here's where I got the info from: http://en.wikipedia.org/wiki/Rigil_Kentaurus#Binary_system. Last sentence of the paragraph.

[Guv’ner]

It would be ideal to have it be the correct year except the increased native wildlife and there added could finish off a couple of factions if it came that early. It would certainly hamper the AI controlled factions.

My reading is probably wrong but it looked to me as though perihelion for Chiron would occur when Alpha Centauri B was closest to it which might not be when Alpha A and B are closest to each other. I may well need to explain it to myself with a miniature planetarium.

The first missing perihelion could still be explained away in the text popup but I personally prefer moving it to at least make it consistent within the game.

[Lord Avalon]

"Real" year by what measurement?  How much time dilation would there be between a terran clock and Unity's?

[Geo]

Well, in the scope of this 20 Mission years event, Planet would move about 20 times more or less 2 astronomical units away from B over the cause of the event since it orbits A during this time. That's why I mentioned a slight randomizer for the onset of the event (or perhaps even the duration, say 18-22 Mission Years), so the minimum distance between Planet and B would be between 10-12 AU's for about 5 Mission Years when B really comes to its closest point to A.
But to explain away the early onset of the event, you could just think that there are so few colonists initially that Planetmind is simply unaware of them that early in the game. So the next perigee after 2115 would be 2195, which is pretty close to when the event starts now ingame IIRC?

"Real" year by what measurement?  How much time dilation would there be between a terran clock and Unity's?

Earth years. Which is, incidently, the same as Mission Years as I recall. I thought the factions kept using the Earth calendar because Planet's seasons were almost indistinguistable due to the lower axial tilt of the planet. At least, I recall that it was mentioned like this in one of the interludes files (or perhaps the planets file).

[Guv’ner]

This is my last foray into this because I’m clearly treading water with rapidly deflating water-wings, but I thought Planet was orbiting the combined centre of mass of Alpha A and B so perihelion would depend on Planet’s own orbit and where that put it closest to Alpha B? I’m now going to go and lie down.

[Lord Avalon]

"Real" year by what measurement?  How much time dilation would there be between a terran clock and Unity's?

Earth years. Which is, incidently, the same as Mission Years as I recall. I thought the factions kept using the Earth calendar because Planet's seasons were almost indistinguistable due to the lower axial tilt of the planet. At least, I recall that it was mentioned like this in one of the interludes files (or perhaps the planets file).

It seems to me you are missing what I meant by time dilation.  Unity may use the same time measurement as Earth, but due to time dilation, less time will pass on the Unity clock than on Earth.  Therefore you probably can't put the "real perihee" year in the game.

There are too many unknowns to know how much the time difference will be.  Unity is a slowship, having no FTL drive, but how close can its fusion drive approach lightspeed?  How long does it take to reach maximum velocity, and how long is its travel time to Alpha Centauri?

For gameplay purposes, it is reasonable to have Unity arrive just after one perihelion period, if you want to be "realistic" and have the first perihelion event happen 60 years into the game.

[Geo]

This is my last foray into this because I’m clearly treading water with rapidly deflating water-wings, but I thought Planet was orbiting the combined centre of mass of Alpha A and B so perihelion would depend on Planet’s own orbit and where that put it closest to Alpha B? I’m now going to go and lie down.

God no, Planet orbits around Alpha Centauri A, slightly further out then Earth to Sol according to the planetary constants section in the Planet.txt file.

Code: [Select]

Planetary constants                 Earth       Planet/     Ratio
                                                Chiron

  Mass                  kg          5.98E+24    1.10E+25    1.84
  Equat. radius         m           6.38E+06    7.54E+06    1.18
  Dist. from star       m           1.50E+11    1.60E+11    1.07
  Axial tilt            degrees     23.45       2.00        0.09
  Surface area          m2          5.10E+14    7.18E+14    1.41
  Standard gravity      m s-2       9.81        12.85       1.31
  Escape velocity       m s-1       11184       13947       1.25
  Density               kg m-3      5519        6150        1.11
  Size of sun           degrees     0.27        0.27        1.02
  Year                  our days    365.3       388.6       1.06
  Year                  local days  365.3       532.0       1.46
  Day                   hours       24.00       17.53       0.73
  Mountain height       m           10626       8112        0.76
  Horizon distance      m           5051        5493        1.09
  Ocean tide (sun)      m           0.12        0.12        0.94
  Ocean tide (moon 1)   m           0.27        0.18        0.67
  Ocean tide (moon 2)   m                       0.11
  Ocean tide (both)     m           0.39        0.41        1.05

"Real" year by what measurement?  How much time dilation would there be between a terran clock and Unity's?

Earth years. Which is, incidently, the same as Mission Years as I recall. I thought the factions kept using the Earth calendar because Planet's seasons were almost indistinguistable due to the lower axial tilt of the planet. At least, I recall that it was mentioned like this in one of the interludes files (or perhaps the planets file).

It seems to me you are missing what I meant by time dilation.  Unity may use the same time measurement as Earth, but due to time dilation, less time will pass on the Unity clock than on Earth.  Therefore you probably can't put the "real perihee" year in the game.

There are too many unknowns to know how much the time difference will be.  Unity is a slowship, having no FTL drive, but how close can its fusion drive approach lightspeed?  How long does it take to reach maximum velocity, and how long is its travel time to Alpha Centauri?

For gameplay purposes, it is reasonable to have Unity arrive just after one perihelion period, if you want to be "realistic" and have the first perihelion event happen 60 years into the game.

I see what you meant now.
Canon says travel time was 40 years. If that was meant as ship years or Earth years, I don't know. Another tidbit of info that seems to be floating around was that Unity's top velocity was 12% lightspeed (which neatly combines with a 40 year travel time). Speed of light can be reached under a constant one Earth gravity acceleration in about a year. But that should burn more fuel then is strictly necessary, so make it a tenth of g to reach top velocity in a bit more then a year.
The Wiki on time dilation says that the effect only starts to get important above 10% speed of light, with a logarithmic increase as you get closer to it. So at 'only' 12%, I think the effect will be off by less then a year.
Personally, I always went with 2100 Anno Domini (or Common Era if you prefer) as the arrival date, and took it from there (and in the arrival year you have a fudge factor of 11 months as well, whether you arrive in Januari, December, or any month inbetween).

As for gameplay reasons. Again, it is totally reasonable to have Planet not act on upstart colonists since they're not that many in number, and don't cause much ecodamage at that point, so no noticable event (roughly MY 2105-2125) after arrival wouldn't harm. Another issue is that I seem to recall the first perihelion event depends on your difficulty level. The higher the difficulty level, the earlier the event. Perhaps that should be checked as well.

[scient]

As for gameplay reasons. Again, it is totally reasonable to have Planet not act on upstart colonists since they're not that many in number, and don't cause much ecodamage at that point, so no noticable event (roughly MY 2105-2125) after arrival wouldn't harm. Another issue is that I seem to recall the first perihelion event depends on your difficulty level. The higher the difficulty level, the earlier the event. Perhaps that should be checked as well.

There is nothing that prevents the event from being checked and started based on game difficulty.  There might be modifications of the severity once it's actually started.  I'd have to look around.  I did briefly and it was modifying value in bases structure among other things.

[Lord Avalon]

OK, so a 40-yr journey, kinda slow.  Unity clock would only be about 5 months behind Earth.

To use the real date would be to continue to assume that during the actual first perihelion nothing happens and then postpone the first game perihelion by a few years.  I'd rather just leave it unchanged than do that.

[Geo]

A thread for nothing? 

[Lord Avalon]

The discussion is worthwhile.  And it's good to see scient posting.

[Guv’ner]

I should stay out of this given my obvious astronomical numtiness but it’s an itch that won’t quit.

If the perihelion is the point in time when Alphas A and B are at their closest, then shouldn’t that be in the middle of the game’s 20 year period of perihelion?

[Lord Avalon]

Good point, Guv'ner.  I guess it depends on whether the closeness 10 yrs out is enough to start the increase in activity, or if the actual perihelion is.

If taken from the middle, 2115 being the first one during the game, and 2195 the next, so the effect period would be from 2186 to 2205.

Still means ignoring the first period, though.

[scient]

chuft is going to do some testing on heavy fungus maps and see how AI handle perihelion being brought up 30 turns.  I'm leaning towards having it be option in alpha/x.txt since it will alter game balance and difficulty. 

On another note, update to my unofficial patch is progressing.  There are a few more things to do but all patches I've done thus far have been rolled into SMACX and SMAC and have been throughly tested.  Since I've rolled guv's corrections and my text bug fixes into the installer, there are only few additional files that aren't touched as part of official patches.  So, now unofficial patch will automatically apply 2000/XP SMAC patch as well as SMACX v2.0 patch.  This adds like 1.5MB to installer (total ~5MB) but I feel it's worth it in saving steps and time.