From: jimv@corsa.ucr.edu (james vassilakos)
Newsgroups: rec.games.frp.gurps
Subject: Planetary Probabilities
Date: 11 Sep 1995 16:03:57 GMT
Organization: University of California, Riverside (Dept. of CS)
 
I've been fooling around a little with the probability
data given in GURPS:Space. Here's a summary of the chances
of various stars having worlds (the estimates are a bit
high since I didn't take empty orbits into consideration
and interpreted the "+2" rule on the margin of p99 to
refer to the total roll, rather than per die). Let me
know if you think these total figures are screwy or not.
 
OIa:   Planets not possible
OIb:   Planets not possible
OV:    Planets not possible
BIa:   Planets not possible
BIb:   Planets not possible
 
       solo    binary
BII:   0.5% /  0.0% chance of 4 to 19 planets
BIII:  0.5% /  0.0% chance of 4 to 19 planets
BIV:   0.5% /  0.0% chance of 4 to 19 planets
BV:    1.9% /  0.0% chance of 3 to 18 planets
AIa:   0.5% /  0.0% chance of 6 to 21 planets
AIb:   0.5% /  0.0% chance of 5 to 20 planets
AII:   0.5% /  0.0% chance of 5 to 20 planets
AIII:  0.5% /  0.0% chance of 4 to 19 planets
AIV:   1.9% /  0.0% chance of 3 to 18 planets
AV:    4.6% /  0.5% chance of 2 to 17 planets
FIa:   1.9% /  0.0% chance of 6 to 21 planets
FIb:   1.9% /  0.0% chance of 5 to 20 planets
FII:   1.9% /  0.0% chance of 4 to 19 planets
FIII:  1.9% /  0.0% chance of 3 to 18 planets
FIV:   9.3% /  1.9% chance of 3 to 18 planets
FV:   83.8% / 62.5% chance of 2 to 17 planets
GIa:   9.3% /  1.9% chance of 6 to 21 planets
GIb:   9.3% /  1.9% chance of 5 to 20 planets
GII:   9.3% /  1.9% chance of 4 to 19 planets
GIII:  9.3% /  1.9% chance of 3 to 18 planets
GIV:  16.2% /  4.6% chance of 2 to 17 planets
GV:   98.1% / 90.7% chance of 1 to 16 planets
GVI:  98.1% / 90.7% chance of 3 to 13 planets
KIa:  50.0% / 25.9% chance of 5 to 20 planets
KIb:  98.1% / 90.7% chance of 5 to 20 planets
KII:  98.1% / 90.7% chance of 4 to 19 planets
KIII: 98.1% / 90.7% chance of 3 to 18 planets
KIV:  98.1% / 90.7% chance of 2 to 17 planets
KV:   98.1% / 90.7% chance of 1 to 16 planets
KVI:  98.1% / 90.7% chance of 3 to 13 planets
MIa:  98.1% / 90.7% chance of 3 to 18 planets
MIb:  98.1% / 90.7% chance of 3 to 18 planets
MII:  98.1% / 90.7% chance of 3 to 18 planets
MIII: 98.1% / 90.7% chance of 3 to 18 planets
MV:   98.1% / 90.7% chance of 1 to 16 planets
MVI:  98.1% / 90.7% chance of 4 to 14 planets

One person I talked to about this made that point that
the propensity of having planets should depend solely on
the star's angular momentum and the abundance of 2nd and
3rd generation material (Population I).

Does anybody have angular momentum figures of any sort for
these classes of stars?

He mentioned that the M stars which are long lived are
probably going to be 1st generation (Population II, very old)
and hence not likely to have anything but lots of hydrogen
and maybe the occasionaly captured planetoid.

However, in GURPS:Space, it says that 1st generation (Population II)
stars inhabit the core and the galactic "halo" almost exclusively and
are found in the galactic "disk" (which I assume is where Sol is
located) only rarely (1% of all disk-area stars). Well, there are lots
and lots of type M stars around Sol. The majority of stars around us
are type M stars. So, it would seem that according to GURPS, most
type M stars are 2nd or later generation (population I).

Does anyone have any reasonably reliable source which indicates that
type M stars are usually 1st generation regardless of locale?

In short, how good do you think the GURPS:Space guestimates are?

jimv@cs.ucr.edu
 

Date: Mon, 11 Sep 1995 17:03:33 -0800
To: jimv@cs.UCR.EDU (james vassilakos)
From: llvogel@teleport.com (Laura L. and Allan Hayes Vogel)
Subject: Planetary possibilities

Dear Jim,

The information that you're looking for about angular momentum values for
different classes of stars can be found, along with a lot of other info
that the authors of GURPS Space used, in Stephan Dole's Habitable Planets
for Man (1964). Dole made a few errors, there have been a few significant
advances in planetary science since then, and the fellows at GURPS didn't
do a realistic estimate for oxygen concentrations on terrestrial planets
IMO, but then neither they nor Dole are (or were) ecologists. Another good
gaming reference for such parameters is "Traveller 2300."

I don't think your source who claimed "that the M stars which are long
lived are probably going to be 1st generation (Population II, very old) and
hence not likely to have anything but lots of hydrogen and maybe the
occasionaly captured planetoid" is correct. As I understand it, the initial
mass of the protostar has more to do with the observed stellar class, but
stellar evolution isn't my speciality. Furthermore, there's been a claim
that Barnard's Star, an M5 star about 6 lights out from Earth, has two
superjovians/brown dwarves in orbit around it, one with a mass of 10
Jupiters. Although this report has not been confirmed to my knowledge (and
I may be a bit dated here), but if it's correct, that would disprove your
source.

I've followed this topic for over 25 years as a research scientist
interested in the possibility other habitable planets and I think GURPS
Space have several errors in their (listed) probabilities of habitable
planets. Another thing is that it's not an either/or situation of
habitability; what about marginal worlds? I'll bet that there's a lot more
marginals than perfects out there. (As an aside, now speaking as a
professional ecologist instead of a gamer, the opportunities for confirming
many of our hypotheses about the environmental and evolutionary processes
would be tremendous if we had _even just one_ more planetary biosphere,
even a marginal world's biosphere, to measure, study, and compare with
Earth - Man, would I love to have the chance to study it!!).

I have also written a BASIC program to generate terrestrial planet
parameters though it's now a bit dated as I've been mainly occupied doing
other work. However, you're welcome to a copy of it if you're interested,
use a Macintosh and don't mind waiting a few months until I get around to
uploading an edited version onto the Internet.

Hope this helps you.

Sincerely,

Allan Hayes Vogel, Ph.D.
ZP's Taxonomic Services
P.O. Box 20895
Keizer, OR 97307-0895
Phone: (503) 390-4684
E-mail: llvogel@teleport.com


From: james vassilakos <jimv>
Subject: Re: Planetary possibilities
To: llvogel@teleport.com (Laura L. and Allan Hayes Vogel)
Date: Mon, 11 Sep 1995 18:56:59 -0700 (PDT)
 
> The information that you're looking for about angular momentum values for
> different classes of stars can be found, along with a lot of other info
> that the authors of GURPS Space used, in Stephan Dole's Habitable Planets
> for Man (1964). Dole made a few errors, there have been a few significant
> advances in planetary science since then, and the fellows at GURPS didn't
> do a realistic estimate for oxygen concentrations on terrestrial planets
> IMO, but then neither they nor Dole are (or were) ecologists. Another good
> gaming reference for such parameters is "Traveller 2300."

Yeah, I've looked at 2300 also. However, I'm thinking of using the
GURPS:Space chart as a basis for some starsystem generation, however,
I want to get some ideas toward modifying it. In particular, the table
on page 104. How, specifically, would you modify it?
 
> I don't think your source who claimed "that the M stars which are long
> lived are probably going to be 1st generation (Population II, very old) and
> hence not likely to have anything but lots of hydrogen and maybe the
> occasionaly captured planetoid" is correct. As I understand it, the initial
> mass of the protostar has more to do with the observed stellar class, but
> stellar evolution isn't my speciality. Furthermore, there's been a claim

The key difference between the pop-1 (2nd and later generation) and pop-2
(1st generation) stars is that the pop-2 stars only have hydrogen present
in their systems while the pop-1 stars have heavier elements present.

> that Barnard's Star, an M5 star about 6 lights out from Earth, has two
> superjovians/brown dwarves in orbit around it, one with a mass of 10
> Jupiters. Although this report has not been confirmed to my knowledge (and
> I may be a bit dated here), but if it's correct, that would disprove your
> source.

It may be the case that the gas giants around Barnard are totally composed
of hydrogen. They'd probably appear a milky white with no bands of various
other elements. They'd be entirely uniform because they'd be composed
solely of hydrogen. This is assuming that Bernard is a 1st generation
star.
 
> I've followed this topic for over 25 years as a research scientist
> interested in the possibility other habitable planets and I think GURPS
> Space have several errors in their (listed) probabilities of habitable
> planets. Another thing is that it's not an either/or situation of
> habitability; what about marginal worlds? I'll bet that there's a lot more
> marginals than perfects out there. (As an aside, now speaking as a
> professional ecologist instead of a gamer, the opportunities for confirming
> many of our hypotheses about the environmental and evolutionary processes
> would be tremendous if we had _even just one_ more planetary biosphere,
> even a marginal world's biosphere, to measure, study, and compare with
> Earth - Man, would I love to have the chance to study it!!).

Agreed. It's too bad we don't have more to go on. However, at least this
presents lots of opportunity for speculation.

> I have also written a BASIC program to generate terrestrial planet
> parameters though it's now a bit dated as I've been mainly occupied doing
> other work. However, you're welcome to a copy of it if you're interested,
> use a Macintosh and don't mind waiting a few months until I get around to
> uploading an edited version onto the Internet.

I'd be interested in seeing it. In the meantime, if you have the time,
please take a look at the following classification system and other
material I'm trying to put together and let me know if you have any
ideas about it or have any suggestions about stuff that you think
needs changing.

BTW, the following is assuming a population I star (heavy
elements present).


                   Shares of Likelihood by Orbital Zone
                      Contact  Inner  Biozone  Outer

A: Solar Companion       -       -       -       -
B: Gas Giant             -       1       1      20
C: Magma Ball            5       3       -       -
D: Primordial            -       3       2       -
E: Asteroid              -       2       3       4
F: Planetoid             -       2       2       2
G: Vacuum Ball           -       2       2       2
H: Snow Ball             -       -       1       3
I: Ice Planet            -       -       1       3
J: Shallow World         -       2       2       2
K: Barren World          -       -       2       2
L: Marginal World        -       -       2       -
M: Garden World          -       -       2       -
N: Desert World          -       -       2       -
O: Water World           -       -       2       -
P: Belch Ball            -       2       2       2
Q: Greenhouse            -       3       2       -
R: Exotic                -       -       2       -
S: Liquid World          -       -       2       1
Z: Special               -       -       -       -
 : Empty                 1       4       6       8

   Total Shares/Zone     6      24      38      49

Zones: Inner, Biozone, and Outer orbital zones are pretty self-
explanitory. The contact zone is that which actually makes
contact with the stellar material but is still outside the
vaporization radius (this zone can only occur in red giants and
some orange supergiants).

Factors of Planet Type: So far, according to this system, the
only influencing factor of what sort of planet you end up with in
a given orbit is the planet's orbital zone. Granted, O, B, and A
stars aren't supposed to produce planets due to their ridiculous
level of luminosity (and as corroborated by their high angular
momentum), however, we only have a few type A stars in the near-
star data we're working with, and I think they are all of the
smallest type, so I may overlook this consideration.

Explanation of Shares: Under this system, the program will first
determine the orbital zone of the world it is generating, then it
will go to the chart above, map out a probability spectrum, roll
the dice, and see which world type gets chosen. So for an outer
zone orbit, there is only a 20/49 chance of a gas giant being
chosen (this may seem low to you, I dunno).

What I need from you: I assigned various numbers to the
chart above, indicating how likely I thought each world type was
to occur in each orbital zone. What I need from you are
suggestions toward modifying that chart. There is also the
latest version of the planetary classification system to
consider (presented below). I'm not looking for the absolute
in technical sophistication, obviously. Just something easy
to work with and somewhat plausible given what little we know
about what's out there.

   Solar Companion: Not technically a world but not the main star
      or even a part of the close-binary pair.
   Gas Giant: Fairly obvious. Great for wilderness refueling if
      you use hydrogen to get around.
   Magma Ball: Ouch, this place is hot. This planet is either
      very close to the primary or is on its way to becoming a
      primordial world. It is possible that such a world is
      tidally locked to its sun. Then, one half would be a
      sea of lava, and the other half would be frozen.
   Primordial: A very young world. Atmosphere poisonous (usually
      reducing, being composed primally of nitrogen and carbon
      dioxide with variable amounts of water vapor, ammonia,
      methane, carbon monoxide and hydrogen sulfide).
      Geologically instable. Lots of volcanos and magma seas.
   Asteroid: A large chuck of rock which is part of an asteroid
      belt.
   Planetoid: A large chuck of rock which isn't part of an
      asteroid belt. Not necessarily round. Could be a
      captured planet.
   Vacuum Ball: Like the moon, essentially. Lots of rock. No
      atmosphere. Too big to be called a planetoid.
   Snow Ball: Like a planetoid, but composed primarily of ice.
      Usually found only beyond the star's biozone.
   Ice Planet: May have a breathable atmosphere so long as there
      is the ecosystem to support it. More likely a dead planet
      without a breathable atmosphere.
   Shallow World: Has some atmosphere, but it's not something
      you'd want in your lungs even assuming there was enough of
      it to breathe, which there isn't. This place will require
      gobs of terraforming if you really want to live here, and
      it probably won't be worth the effort when you're done.
      Mars might be an example.
   Barren World: Generally a non-breathable atmosphere, but there
      will probably be water tied up as ice crystals in the
      soil. Oxygen will probably reside in oxidizing compounds
      such as ferric oxide or in various nitrates. World may be
      volcanically active. Probably on its way to becoming a
      shallow world. No life beyond bacteria.
   Marginal World: Complex lifeforms either never evolved on this
      planet or went extinct sometime within the past couple
      million years. Perhaps the sun flared and knocked out the
      entire ecosystem, or maybe a slew of meteors struck,
      churning up enough dust that the sun was blotted out for
      several decades. Irregardless, this world is ripe for
      colonization. Some terraforming will be required, however,
      if the world is to remain habitable over the long term.
      Mars might have been a good example eons ago.
   Garden World: Earth is a prime example. Not only can you
      breath the atmosphere without mechanical aid, but life,
      either native or transplanted, thrives in abundance.
   Desert World: This world isn't entirely desert, but the
      hydrographic percentage is relatively low. Most likely, the
      atmosphere is somewhat thin, and the change in temperature
      from day to night is fairly extreme. Assuming an ecosystem
      is present, however, the atmosphere is probably breathable.
   Water World: Over 90% covered by water and ice. Probably a
      breathable atmosphere. Possibly a teaming native ecosystem
      which got evolutionarily stuck due to the total lack of any
      freestanding continents.
   Belch Ball: Lifeless terrestrial planet with a poisonous,
      toxic, or possibly even borderline-corrosive atmosphere.
   Greenhouse: A world gone to hell because of too much
      greenhouse gases (ala Venus).
   Exotic World: This planet has life, but not as we know it.
      The atmosphere is poisonous to humans and may even contain
      lethal micro-organisms. The temperature, however, is
      probably moderate enough that an individual can walk around
      unscathed by the environment so long as he has a self-
      contained oxygen supply. Many alien homeworlds will
      be exotics.
   Liquid World: Surface predominantly covered by ammonia or
      liquid methane. In the former case, the world may contain
      a teaming alien ecosystem. In the latter, alien life is
      less likely. Of course, other (non-water) liquids are also
      possible.
   Special: This world cannot be placed in any of the previously
      defined categories. It may be an artificial planet or
      perhaps a fluke of nature. GM's discretion advised.


Date: Wed, 13 Sep 1995 23:57:04 -0800
To: james vassilakos <jimv@cs.UCR.edu>
From: llvogel@teleport.com (Laura L. and Allan Hayes Vogel)
Subject: Re: Planetary possibilities

Dear Jim,

In answer to your questions and comments:

>Yeah, I've looked at 2300 also. However, I'm thinking of using the
>GURPS:Space chart as a basis for some starsystem generation, however,
>I want to get some ideas toward modifying it. In particular, the table
>on page 104. How, specifically, would you modify it?

First, I'd drop everything above an A5 and all Size I and II's because, as
you noted later in your e-mail, no planets are likely orbitting the
brighter classes. Nor are giants [and white dwarves] likely to have
planets. Second, I'd add individual subclasses between A5 and K5 at every
half class interval; the increase isn't excessive if you've dropped the
brighter classes.

>I'd be interested in seeing it (- my planetary parameters program).

Okay, I'll e-mail a copy to you when I'm finished.

>What I need from you are
>suggestions toward modifying that chart. ... I'm not looking for the absolute
>in technical sophistication, obviously. Just something easy
>to work with and somewhat plausible given what little we know
>about what's out there.

In general, a very good system and, more importantly, probably a very
playable one. The following are some comments on it from my perspective.
Don't take them too seriously, or as heavy critisms; I want to be
constructive, not destructive, in my observations.  -  :-)

>   Magma Ball: Ouch, this place is hot. This planet is either
>      very close to the primary or is on its way to becoming a
>      primordial world. It is possible that such a world is
>      tidally locked to its sun. Then, one half would be a
>      sea of lava, and the other half would be frozen.

Mercury, I presume? (said Stanley) A low probability planet, I suspect;
your odds (i.e., shares of likelihood) aren't bad for this group.

>   Primordial: A very young world. Atmosphere poisonous (usually
>      reducing, being composed primally of nitrogen and carbon
>      dioxide with variable amounts of water vapor, ammonia,
>      methane, carbon monoxide and hydrogen sulfide).
>      Geologically instable. Lots of volcanos and magma seas.

Very low probability as most worlds have already passed through this stage
a long time ago (>4 *10^9 years ago for Earth in a 4.5*10^9 year long
history); I'd downgrade the number of shares to _much_ less than one in the
biozone - about1/10.

>   Asteroid: A large chuck of rock which is part of an asteroid
>      belt.
>   Planetoid: A large chuck of rock which isn't part of an
>      asteroid belt. Not necessarily round. Could be a
>      captured planet.
>   Vacuum Ball: Like the moon, essentially. Lots of rock. No
>      atmosphere. Too big to be called a planetoid.

Why don't you split up the planetoid class between the other two classes?

>   Shallow World: Has some atmosphere, but it's not something
>      you'd want in your lungs even assuming there was enough of
>      it to breathe, which there isn't. This place will require
>      gobs of terraforming if you really want to live here, and
>      it probably won't be worth the effort when you're done.
>      Mars might be an example.
>   Barren World: Generally a non-breathable atmosphere, but there
>      will probably be water tied up as ice crystals in the
>      soil. Oxygen will probably reside in oxidizing compounds
>      such as ferric oxide or in various nitrates. World may be
>      volcanically active. Probably on its way to becoming a
>      shallow world. No life beyond bacteria.

Yes, I would call these two very low G worlds in different stages of
development, so probably lump them.

Parallel to these classes, I would include a superterrestrial class, a
rocky, high-density-core world with a planetary mass between 2 and 10 times
Earth and an extremely thick atmosphere with a share of one in the biozone.
Of course, my ex-college roommate, G. David Nordley, may be correct in his
Analog article of last year that such don't exist, but the fellows that
publish in Icarus seem to like the idea still, so I'd keep it until Gerry
can prove them wrong.

>   Marginal World: Complex lifeforms either never evolved on this
>      planet or went extinct sometime within the past couple
>      million years. Perhaps the sun flared and knocked out the
>      entire ecosystem, or maybe a slew of meteors struck,
>      churning up enough dust that the sun was blotted out for
>      several decades. Irregardless, this world is ripe for
>      colonization. Some terraforming will be required, however,
>      if the world is to remain habitable over the long term.
>      Mars might have been a good example eons ago.

I think that you may be lumping too much possibilities together here
although your category makes perfect sense. Some may never be good
colonization targets however.

I would also include in this group optically-reversed-protein worlds, moist
(as opposed to runaway a la Venus) greenhouse worlds, and heavy metal
worlds (i.e. worlds with too high concentrations of heavy metals for
terrestrial organisms, although the native biota has evolved tolerances
(and possibly even requirements) for large amounts of heavy metals as other
possibilities. (And lest you think that my last example is crazy or only a
minor possibility, first, heavy metals are one of my research specialities
as an ecologist - I did both my M.S. and Ph.D. on this subject, and second,
there was a so-so SF novella published about 30 years ago in either IF or
Worlds of Tomorrow - the sibling publications of the late [and mourned]
Galaxy magazine - using this very idea as its theme.)

>   Desert World: This world isn't entirely desert, but the
>      hydrographic percentage is relatively low. Most likely, the
>      atmosphere is somewhat thin, and the change in temperature
>      from day to night is fairly extreme. Assuming an ecosystem
>      is present, however, the atmosphere is probably breathable.

Last point is very doubtful if the percent land over 90%. (I call anything
over 45% land a desert world as the percentage of desert gets too high for
good oxygen generation - see note below.)

>   Water World: Over 90% covered by water and ice. Probably a
>      breathable atmosphere. Possibly a teaming native ecosystem
>      which got evolutionarily stuck due to the total lack of any
>      freestanding continents.

Ja, only I use 80% in my program, and I'm not sure about the breathability
- see note below.


BREATHABILITY PROBLEMS,
or why habitable (i.e. garden) planets may be harder to come by than we'd like

Humans require a minimum partial presssure of oxygen of 60 mm Hg. The
amount of oxygen produced is quite variable depending upon the type of
surface producing the oxygen.  This variability greatly reduces the
likelihood of garden worlds and increases the probabilities of marginal
ones when it is added to the "equation".

I have attempted to model this variability in my program, using a
biogeochemical text of mine as my data source. I combined all non-desert
biomes into one. The resulting mean productivity was just under 1.0 (0.98)
as mm Hg of oxygen produced per one million square kilometers. For all
oceanic biomes, the resulting value is 0.15, and the value for terrestrial
deserts is 0.034. A good first order estimate for the amount of desert on
an inhabitable world is the square of the percent land. If you take the
surface area of your planet relative to Earth and multiply by 510, then
multiply it by the following term for the effectiveness of oxygen
production, you should get a quick estimate of the amount of oxygen
available to breathe in mm Hg.

Relative effectiveness of oxygen production =
        %ocean * 0.15 + % land^2 * 0.034 + (1 - % ocean - % land^2) * 0.98

[I call the last term, 1 - % ocean - % land^2, the % fertile land, because
it's doing most of the oxygen generation.]

(The earth standard value for this term is 0.312; you can probably
normalize it fairly easily.)


Consequently, I'd increase marginal worlds by one share and decrease garden
worlds by one share in your system.  [Ain't it the pits to have someone
pointing out a whole new set of problems? - I never liked it either -  :-)
]

Another minor thing you might consider is that water worlds will tend to be
heavier worlds than desert worlds as high gravity will tend to "smooth out"
differences in elevation, so make the oceans both shallower, hence
displacing the water in the deep basins so covering more of the planet.
However, that complication shouldn't mess up your game table. (I'd ignore
this comment in your position, it's just a detail.)

>   Belch Ball: Lifeless terrestrial planet with a poisonous,
>      toxic, or possibly even borderline-corrosive atmosphere.

Chlorine, anyone? Of course, out of the biozone, it should be methane and
ammonia.

>   Greenhouse: A world gone to hell because of too much
>      greenhouse gases (ala Venus).

Correction, greenhouse worlds are terrestrial planets which are too close
to their primary. Earth has the same amount of carbonates proportional to
its mass as Venus has in carbon dioxide. Venus just got cooked is all (it's
really too bad that Venus and Mars weren't switched; "Minerva" [as it's
known to some of us in biogeochemical circles] would have been another
inhabitable world - not breathable, but easily inhabitable.) Anything with
an E > 1.5 ought to get cooked, so become a greenhouse world. I recommend
dropping the greenhouse shares in habitable zone to zero (if there's a
greenhouse world in the habitable zone, it's clearly a specific, and
artifically-caused, situation, i.e., an example of your special category)
and set the total in the inner zone equal to the combined total of garden,
desert, water, and marginal worlds.

>   Exotic World: This planet has life, but not as we know it.
>      The atmosphere is poisonous to humans and may even contain
>      lethal micro-organisms. The temperature, however, is
>      probably moderate enough that an individual can walk around
>      unscathed by the environment so long as he has a self-
>      contained oxygen supply. Many alien homeworlds will
>      be exotics.

Nice idea!

>   Liquid World: Surface predominantly covered by ammonia or
>      liquid methane. In the former case, the world may contain
>      a teaming alien ecosystem. In the latter, alien life is
>      less likely. Of course, other (non-water) liquids are also
>      possible.

I suggest combining this with the Belch Ball category into a Toxic World
class, and reduce the shares of the resulting group by at least half,
possibly to one third or one fourth.

>   Special: This world cannot be placed in any of the previously
>      defined categories. It may be an artificial planet or
>      perhaps a fluke of nature. GM's discretion advised.

Ringworld, yes?

Please take all of my comments with a large grain of salt; I'm a
perfectionist at heart and am overly fond of realism which can very easily
spoil a good gaming idea. Don't forget S. Holmes's admonition to Dr.
Watson, "The game's a foot!"

Best of luck in using my ideas for your game.


From: james vassilakos <jimv>
Subject: Re: Planetary possibilities
To: llvogel@teleport.com (Laura L. and Allan Hayes Vogel)
Date: Tue, 19 Sep 1995 00:08:00 -0700 (PDT)
 
> Why don't you split up the planetoid class between the other two classes?

Wanted to distinguish between a zero-gravity rockball which is part
of an asteroid belt and one which isn't.
 
> Please take all of my comments with a large grain of salt; I'm a
> perfectionist at heart and am overly fond of realism which can very easily
> spoil a good gaming idea. Don't forget S. Holmes's admonition to Dr.
> Watson, "The game's a foot!"

Yeah, the more I look at this whole mess, and the more I talk with other
people, the less and less hospitable the universe looks. There are so
many factors to planetary development, and just one can ruin your whole
day. Not the sort of universe we're used to from television or the
movies.
 
> Best of luck in using my ideas for your game.

Thanks. Your comments did yield quite a few counter-comments from a
friend of mine in Germany. I'm going to be starting-up a mailing list
for the development of this sfrpg, and he and another friend in Sweden
are going to be on it. If you'd like me to add your address as well,
I'd be more than happy to have your input as we go further with the
setting-design.
 

Date: Wed, 20 Sep 1995 07:03:30 -0800
To: james vassilakos <jimv@cs.UCR.edu>
From: llvogel@teleport.com (Laura L. and Allan Hayes Vogel)
Subject: Re: Planetary possibilities

Hi-

Re: your recent e-mail response:

>> Why don't you split up the planetoid class between the other two classes?
>
>Wanted to distinguish between a zero-gravity rockball which is part
>of an asteroid belt and one which isn't.

Sounds reasonable; however, it's likely to be a low probability occurrence
based upon our present understanding of the formation of this solar system.

>Yeah, the more I look at this whole mess, and the more I talk with other
>people, the less and less hospitable the universe looks. There are so
>many factors to planetary development, and just one can ruin your whole
>day. Not the sort of universe we're used to from television or the
>movies.

Yep; however don't lose all heart, sometimes that unhospitable universe
works in our favor. In the latest Scientific American (the October issue),
beginning on p. 134, there's an interesting article on double star
formation. It seems that it's more likely than not and that planets may
form around solar-type doubles and triples if they're far enough apart. It
was real nice to see a favorable (for life in the universe and gaming)
hypothesis clearly supported.

Another example of how sometimes things work in our favor is that it
appears that once life begins, life tends to persist (according to the
revised version of Lovelock's Gaia hypothesis). And even in the absence of
life, according to Kastings, et al. (in an earlier Scientific American
review article), there's a negative geochemical feedback loop which keeps
terrestrial planets above a minimum size from turning into iceboxes.
Apparently you can have running water on any world with an E above 0.45 if
it's big enough to still have geothermal heating. Unfortunately there isn't
an equivalent one for preventing a greenhouse.

>> Best of luck in using my ideas for your game.
>
>Thanks. Your comments did yield quite a few counter-comments from a
>friend of mine in Germany. I'm going to be starting-up a mailing list
>for the development of this sfrpg, and he and another friend in Sweden
>are going to be on it. If you'd like me to add your address as well,
>I'd be more than happy to have your input as we go further with the
>setting-design.

Sure, count me in; I'm always interested in planetary design ideas. If your
German friend doesn't mind, I'd also like to see what he disagreed with me
on and what his sources were. I don't read German and there's always a
chance that there might be something that hasn't translated into English
yet which I could use to improve my program. But please pass this part of
my message on to him and ask him first. Thanks.


