massive gravity effects

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spirochete
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Re: massive gravity effects

Postby spirochete » Tue May 07, 2013 11:32 am

GamingGlen wrote:Thanks for the information. I was using the right equation after all for surface gravity, so it was not as linear as I had thought when I posted.
Heh heh, no test - just remember that all that applies to solid bodies, and fudge the size 1/3 to 2/3 larger when you start adding lots of volatiles.

Here's some related stuff that may be helpful
  • mass m = dr³ = gr² × 5.9736E+24 kg
    radius r = g/d = sqrt(m/g) = cbrt(m/d) = m^1/3 d^(-1/3) × 6,371 km
    density d = g/r = m/r³ = mr^-3 = g^1.5/sqrt(m) × 5.515 g/cm³
    gravity g = dr = m/r² = mr^-2 = m/cbrt(m/d)² = m^1/3 d^(2/3) × 9.80665 m/s²
    esc velocity ve = sqrt(gr) = sqrt(dr²) = sqrt(m/r) × 11.186 km/s
    horizon distance = sqrt(r) × 4.654 km
    surface area a = r² × 510,065,624.78 km²
    volume v = r³ × 1,083,207,324,897.38 km³
Colin
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Re: massive gravity effects

Postby Colin » Thu May 09, 2013 9:08 pm

In writing 2300, I'm handicapped to a degree by what has gone before. King is not a world that anyone in their right mind would settle.

My thoughts: Interface transport: For humans its nuclear-powered spaceplanes. Small capacity, lots of reaction mass. For cargo, it's a catapult. High power consumption. big noise, small capacity. Kept about 2000 km away from any population centre.

King is a result of using an RPG world design system to build a world. Sometimes odd things happen. If they are fun, though, you keep them.

King is a nasty excuse for a planet, and anyone who would send people there is an evil b*stard.

When we get to the American Arm book, I will take a long look at King, and see what I can do to make it a bit more believable, while still keeping it evil.

I recall one unpublished adventure where the author postulated some sort of drug-based adaptation to King, perhaps combined with an exoskeleton for support. This drug therapy could not be used for very long, had some nasty long-term effects, IIRC.

Cybernetics are a possibility, too.
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Re: massive gravity effects

Postby F33D » Thu May 09, 2013 9:42 pm

Wil Mireu wrote:You obviously don't know much about the subject, but please don't make the mistake of using your ignorance to be authoritative about what is actually known.
And, neither do you know much about science since it is untested data. But, please use your arrogance to push your ideas. It is fun to watch. ;)
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Re: massive gravity effects

Postby Lemnoc » Thu May 09, 2013 10:23 pm

Colin wrote:King is a nasty excuse for a planet, and anyone who would send people there is an evil b*stard.

When we get to the American Arm book, I will take a long look at King, and see what I can do to make it a bit more believable, while still keeping it evil.
It's a hell world. Works as a hell world, and if you back down on some of the assumptions it just becomes less of a hell world. :?

It's biggest drawback is it is not a place for casual adventuring, although you can draw up a lot of scenarios for using it in play. The reproduction lottery being discussed a few pages back is one example.
spirochete
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Re: massive gravity effects

Postby spirochete » Thu May 09, 2013 11:54 pm

Colin wrote:King is a result of using an RPG world design system to build a world. Sometimes odd things happen. If they are fun, though, you keep them.
This happens because most worldgen systems (2300 included) use two separate rolls for whatever is used to derive gravity. One roll for size, another roll for density or mass, under the widespread assumption that these variables are independent.

They are not.
spirochete
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Re: massive gravity effects

Postby spirochete » Fri May 10, 2013 12:13 am

Lemnoc wrote:It's a hell world. Works as a hell world, and if you back down on some of the assumptions it just becomes less of a hell world.
What I don't get is why King doesn't have a massive hydrogen/helium atmosphere. It's a Neptune-mass object, and ought to have a hydrogen atmosphere, even according to the 2300 worldgen rules.

If a planet is massive enough to retain a gas, it can (in theory) retain any amount of it.
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Re: massive gravity effects

Postby Wil Mireu » Fri May 10, 2013 1:20 am

F33D wrote:And, neither do you know much about science since it is untested data. But, please use your arrogance to push your ideas. It is fun to watch. ;)
:lol: :lol: :lol:

Hm. I guess I'd better send back my Ph.D. certificate and quit my professional research career then... some random guy on the internet told me I don't know science! :P

Anyway, please be quiet now. Us grown-ups are talking ;)
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Re: massive gravity effects

Postby Wil Mireu » Fri May 10, 2013 1:26 am

spirochete wrote:
Lemnoc wrote:It's a hell world. Works as a hell world, and if you back down on some of the assumptions it just becomes less of a hell world.
What I don't get is why King doesn't have a massive hydrogen/helium atmosphere. It's a Neptune-mass object, and ought to have a hydrogen atmosphere, even according to the 2300 worldgen rules.

If a planet is massive enough to retain a gas, it can (in theory) retain any amount of it.
See, spirochete here is someone who knows exactly what he's talking about. :).

There is the (never-really-described) "Failed Core" option in 2300AD though. I always interpreted that as being a world big enough to retain hydrogen and helium, but not a full-blown gas giant, just a big terrestrial world with a thin (by GG standards) H2/He atmosphere. Maybe most of it got blown off by stellar winds or flare activity, or it didn't have time to collect a huge gas envelope or something. King could fit that bill, though it'd be a very hostile environment with crushing surface pressure, possibly a world ocean, maybe even with supercritical water so it doesn't have a distinguishable surface - nothing like how it's portrayed in the books.
spirochete
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Re: massive gravity effects

Postby spirochete » Fri May 10, 2013 1:46 am

Wil Mireu wrote: There is the (never-really-described) "Failed Core" option in 2300AD though. I always interpreted that as being a world big enough to retain hydrogen and helium, but not a full-blown gas giant, just a big terrestrial world with a thin (by GG standards) H2/He atmosphere.
The book doesn't say much about them. Clues in the ref's book indicate:

● They have an atmosphere
● They only occur in the 'outer zone'
● They have ice sheets

Pretty much any solid body with an atmosphere orbiting beyond the star's ice line.
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Re: massive gravity effects

Postby AndrewW » Fri May 10, 2013 4:01 am

F33D wrote:
Wil Mireu wrote:You obviously don't know much about the subject, but please don't make the mistake of using your ignorance to be authoritative about what is actually known.
And, neither do you know much about science since it is untested data. But, please use your arrogance to push your ideas. It is fun to watch. ;)
*Moderator hat on*

Try and avoid personal attacks. Let's just move on and have a nice friendly discussion.

*Moderator hat off*
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Re: massive gravity effects

Postby Wil Mireu » Fri May 10, 2013 4:43 am

spirochete wrote:The book doesn't say much about them. Clues in the ref's book indicate:

● They have an atmosphere
● They only occur in the 'outer zone'
● They have ice sheets

Pretty much any solid body with an atmosphere orbiting beyond the star's ice line.
Given what we know now though, I guess that some of these bodies could migrate inwards to the habitable zone (or inner zone). "Failed Core" does sound like "oceanic superearth" could be part of their definition to me at least.
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Re: massive gravity effects

Postby GamingGlen » Fri May 10, 2013 5:58 am

Wil Mireu wrote:
spirochete wrote:The book doesn't say much about them. Clues in the ref's book indicate:

● They have an atmosphere
● They only occur in the 'outer zone'
● They have ice sheets

Pretty much any solid body with an atmosphere orbiting beyond the star's ice line.
Given what we know now though, I guess that some of these bodies could migrate inwards to the habitable zone (or inner zone). "Failed Core" does sound like "oceanic superearth" could be part of their definition to me at least.
Ever since I heard about migrating planets I've wondered how they do it and what effects does it have on everything else in the system. But I haven't seen anything said more about it. Is that because no one really knows? Or are there theories/computer models showing what could happen or how it could have it happened?
Glen
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Re: massive gravity effects

Postby spirochete » Fri May 10, 2013 6:07 am

Wil Mireu wrote:
spirochete wrote:The book doesn't say much about them. Clues in the ref's book indicate:

● They have an atmosphere
● They only occur in the 'outer zone'
● They have ice sheets

Pretty much any solid body with an atmosphere orbiting beyond the star's ice line.
Given what we know now though, I guess that some of these bodies could migrate inwards to the habitable zone (or inner zone). "Failed Core" does sound like "oceanic superearth" could be part of their definition to me at least.
They bridge the gap between large icy moons and sub-Uranian ice giants. I had some notes written up old Failed core worlds to help better define them. I remember that thawing into a pelagic superterrestrial during inward migration was one possible outcome. It can also happen when the parent star ages and begins to ascend the red giant branch.

Another outcome was semi-hospitable failed cores - those that are just beyond the edge of the life zone and, though intensely cold could have a breathable atmosphere due to abiotic oxygen photolyzed from the ice (by the UV rays of an A or F star). Completely iced over with no exposed rocks, there's nothing for the O2 to react with, so it just accumulates in the atmosphere until it reaches an equilibrium level. I say semi-hospitable because they would only require a heated arctic suit and facemask for survival instead of a spacesuit.
spirochete
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Re: massive gravity effects

Postby spirochete » Fri May 10, 2013 6:15 am

GamingGlen wrote: Ever since I heard about migrating planets I've wondered how they do it and what effects does it have on everything else in the system. But I haven't seen anything said more about it. Is that because no one really knows? Or are there theories/computer models showing what could happen or how it could have it happened?
Wikipedia has a good article on planetary migration.
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Re: massive gravity effects

Postby captainjack23 » Sun May 12, 2013 9:14 pm

Wil Mireu wrote:
F33D wrote:And, neither do you know much about science since it is untested data. But, please use your arrogance to push your ideas. It is fun to watch. ;)
:lol: :lol: :lol:

Hm. I guess I'd better send back my Ph.D. certificate and quit my professional research career then... some random guy on the internet told me I don't know science! :P

Anyway, please be quiet now. Us grown-ups are talking ;)
Well, speaking as someone who also has one of those, I have to say that unless it is actually in a related field like, say, planetary science, it's pretty irrelevant to the discussion, except as an attempt to add gravitas to what is otherwise just another opinion.
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Re: massive gravity effects

Postby OneTrikPony » Sat Sep 14, 2013 6:46 pm

Please Forgive the thread necro. King is one of the first things that really caught my attention, I have questions but didn't want to start a new thread only to be referred to this one...

My main questions:
What is the appropriate Radius for King given it's 30.42m/s surface gravity and more standard density of 5-6 thousand Kg/m?

If it had a realistic radius would that solve the tide locked issue?

If it had a realistic radius and were switched in position with the planet at the outer edge of the habitable zone would that solve the tide locked issue?

Forgive me for asking these questions after being given the equasions posted earlier;
mass m = dr³ = gr² × 5.9736E+24 kg
radius r = g/d = sqrt(m/g) = cbrt(m/d) = m^1/3 d^(-1/3) × 6,371 km
density d = g/r = m/r³ = mr^-3 = g^1.5/sqrt(m) × 5.515 g/cm³
gravity g = dr = m/r² = mr^-2 = m/cbrt(m/d)² = m^1/3 d^(2/3) × 9.80665 m/s²

I tried but, I simply don't have the math to solve for R
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Re: massive gravity effects

Postby spirochete » Thu Sep 26, 2013 1:50 am

OneTrikPony wrote:Please Forgive the thread necro. King is one of the first things that really caught my attention, I have questions but didn't want to start a new thread only to be referred to this one...

My main questions:
What is the appropriate Radius for King given it's 30.42m/s surface gravity and more standard density of 5-6 thousand Kg/m?

If it had a realistic radius would that solve the tide locked issue?

If it had a realistic radius and were switched in position with the planet at the outer edge of the habitable zone would that solve the tide locked issue?

Forgive me for asking these questions after being given the equasions posted earlier;
mass m = dr³ = gr² × 5.9736E+24 kg
radius r = g/d = sqrt(m/g) = cbrt(m/d) = m^1/3 d^(-1/3) × 6,371 km
density d = g/r = m/r³ = mr^-3 = g^1.5/sqrt(m) × 5.515 g/cm³
gravity g = dr = m/r² = mr^-2 = m/cbrt(m/d)² = m^1/3 d^(2/3) × 9.80665 m/s²

I tried but, I simply don't have the math to solve for R
The appropriate radius is 1.795 earth radii, which gives a diameter around 22,866 km. Mass is a tad under 10 earth-masses, gravity 3.1 G.

This is the upper limit for a solid silicate-nickle-iron exoplanet. The minimum molecular weight retained is less than 2, meaning it retains hydrogen in its atmosphere. Since protoplanetary nebulae contain huge amounts of hydrogen, you'll need some explanation for the mechanism by which King escaped snowball accretion into a gas giant.
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Re: massive gravity effects

Postby spirochete » Thu Sep 26, 2013 1:55 am

OneTrikPony wrote: If it had a realistic radius would that solve the tide locked issue?
No. Increasing a planet's size subjects it to greater tidal braking.
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Re: massive gravity effects

Postby spirochete » Thu Sep 26, 2013 1:58 am

OneTrikPony wrote: Forgive me for asking these questions after being given the equasions posted earlier;
mass m = dr³ = gr² × 5.9736E+24 kg
radius r = g/d = sqrt(m/g) = cbrt(m/d) = m^1/3 d^(-1/3) × 6,371 km
density d = g/r = m/r³ = mr^-3 = g^1.5/sqrt(m) × 5.515 g/cm³
gravity g = dr = m/r² = mr^-2 = m/cbrt(m/d)² = m^1/3 d^(2/3) × 9.80665 m/s²

I tried but, I simply don't have the math to solve for R
The units in the formulas are "earths". For example:

r = sqrt(m/g) , so if m = 0.25 earth masses and g = 0.54 earth gravities, then

r = sqrt(0.25/0.54) = 0.68 earth radii
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Re: massive gravity effects

Postby SSWarlock » Thu Sep 26, 2013 2:14 am

ShawnDriscoll wrote:I'm not fit to be near 3G. Spine compression on top of the hip is no fun.
Spine compression anywhere along the spine is no fun. Think multiple herniated discs occurring at random even when lying down causing nerve compression similar to sciatica. Sustained 3Gs is just bad news all around.
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