Change Log for 6.40 Discussion

[alex_brunius]

Your memory is correct, but it's not really low.  Rotational energy of 1.3E12 J, which is not a small number at all.  And the angular momentum is about 1.3E13 kg*m^2*s, which is also very large.  If you're launching your projectiles from the outer edge of the cylinder at 3000 m/s, you'll need to fire approximately 1.7E7 kg, with a total energy in the projectiles of 7.7E13J.  

Why would we launch projectiles at 3000 m/s when our ships go 3000 km/s in Aurora?

[bean]

Why would we launch projectiles at 3000 m/s when our ships go 3000 km/s in Aurora?

That's going to drive the energy budget up significantly.  I think about three orders of magnitude.  Launching all the excavation fragments is probably your best bet.

[Shipright]

I believe most asteroids would roll apart pretty quickly.

I don't know about you,but I always just imagined that space ships had "artificial gravity" through some kind of transnewtonian magic floor paneling. If ships can have it, why can't colonies?

Thats why I suggested actual components for gravity on ships. No gravity for early ships, rotating sections a little later, and some scifi magic generator in late game. The amount of gravity on a ship could be used for lots of things like crew endurance, max crew training, etc. If you lose gravity due to damage...

Also while I know Steve mentioned rotating the actual body in his post on this feature, if you RP it it doesn't have to be that way. Nothing prevents you from excavating a cylinder and spinning a centrifuge in it for gravity. Once you get about a diameter of 170+ meters you can simulate gravity without a rotation rate that will make the normal person sick.

[Paul M]

Sadly, your knowledge of physics is horribly wrong.  For Ceres, rotating fast enough to have 1G at the equator, and neglecting Ceres's own gravity (because I forgot when I did the math) it would have rotational energy of 9E26 J.  To put this into perspective, the gravitational binding energy of Ceres is only 7.4E25 J.  That alone settles if spinning up a body of that type is possible. 
No, they aren't.  Iron meteorites only compose about 6% of all meteorites, and IIRC the proportion of nickle-iron asteroids is similar.  Also, they aren't solid blocks.
Wrong again.  The amount of energy and momentum involved is substantial. 
It masses on the order of 2E9 kg and has a moment of inertia of 6.4E13 kg*m^2.  That's pretty big in my book.
Your memory is correct, but it's not really low.  Rotational energy of 1.3E12 J, which is not a small number at all.  And the angular momentum is about 1.3E13 kg*m^2*s, which is also very large.  If you're launching your projectiles from the outer edge of the cylinder at 3000 m/s, you'll need to fire approximately 1.7E7 kg, with a total energy in the projectiles of 7.7E13J. 
Theoretically, you could make it work so long as you have a definite long axis to the body.  However, balance would make it better.

I'm not going to argue with wikipedia about composition of asteroids.  I don't much care what is typical you aren't going to try and do this on something that will fly appart during the process and that means you will be doing it to a metalic asteroid.

The rest of it is a perception problem.  O'neil colonies are of the same size and mass and I've never heard an engineering objection to them.

I have no idea why you care about the angular momentum.  That is relevent only when I go to change that rotation, until then it maters not in the least, outside of the inertia I have to overcome to get the process going.  If the body can survive the induced gravity gradient without internal stress issues then the angular momentum will only come into play when I try to change the spin which I would say you aren't likely to do.  It will also serve to defend the colony against shifts to its rotational axis...any attempt to displace that axis will face strong objection. 

1 m3 of water is 1000 kg, the density of most metals is 3+x that.  So I need to launch in total 600 m3 of metal from the surface from multiple launch sites over a period of days.  That is like 20 m3 from 30 or so sites over a week.  That is about one dumptruck worth per day (must be at least 4 m3 in a dump truck?)  A few thousand m per second launch velocity is easily achievable.  In aroura your mass drivers fire material at 1000 km/s.  Mind you doing this creates a hell of a no fly zone...

I would expect that during the hollowing out process you add an internal structure to support the shell to deal with any issues arising from the spin up process.  I will say again I don't see the practical value of doing it...as building a space station is likely easier and since you design it you can ensure that you don't get any surprises near the end of the process.  O'neil colonies are essentially identical objects and you best use of the asteroid would likely be as raw materials for the O'neil colony.

[MarcAFK]

Have I mentioned how much I love the scientific detail and accuracy that goes along with discussions in this forum?
Thx for pointing out the flaw in my earlier calculation, I was going off some energy requirement numbers I found for a much larger body then modifying them based on possibly flawed calculation using the idea that double the mass would require a square of the energy.
Anyway, I think we're mostly on agreement that it doesn't really make sense to actually spin a large body to create artificial gravity, after all that's what orbital habitats are for and we already have them in the game.
I would debate that the energy requirement isn't ridiculous considering the kind of energy requirements needed for travel in aurora anyway, but it's obvious that it's not the most efficient way of making such a body habitable.
I want to point out again that I support the proposed underground habitats entirely, I just want this debate to steer somewhere towards the point where they'll make some kind of sense, perhaps we've hijacked this thread enough to require a new one entirely for the subject?
Perhaps artificial gravity makes the most sense, or hell even magnetic boots or whatever would work enough to make a colony work, who cares about osteoporosis when earth is overcrowded and someone's offering you a free ride to an exciting new underground colony where you can spend 16 hours a day using a plasma torch to hollow out living space for people to be stacked like sardines into a plastic lined crate equipped with free wifi, stims, and robot hookers ™.

[bean]

I'm not going to argue with wikipedia about composition of asteroids.  I don't much care what is typical you aren't going to try and do this on something that will fly appart during the process and that means you will be doing it to a metalic asteroid.

Do you think Steve is likely to implement a test for metallic asteroids in the game?  Also, I have serious doubts about making it work for metallic asteroids (see below).

The rest of it is a perception problem.  O'neil colonies are of the same size and mass and I've never heard an engineering objection to them.

The two are very different.  The designer of an O'Neil colony has much greater control over the final product, particularly the materials involved.  I'd have to check my notes from materials class, but the strengths involved are probably a factor of two or three apart, and the colony isn't going to have hidden flaws. 

I have no idea why you care about the angular momentum.  That is relevent only when I go to change that rotation, until then it maters not in the least, outside of the inertia I have to overcome to get the process going.  If the body can survive the induced gravity gradient without internal stress issues then the angular momentum will only come into play when I try to change the spin which I would say you aren't likely to do.  It will also serve to defend the colony against shifts to its rotational axis...any attempt to displace that axis will face strong objection. 

I care about the angular momentum because it's the controlling factor in spinning up the asteroid.  Angular momentum is conserved in exactly the same way linear momentum is, and unlike on Earth, you don't have a big momentum sink to dump into. 

1 m3 of water is 1000 kg, the density of most metals is 3+x that.  So I need to launch in total 600 m3 of metal from the surface from multiple launch sites over a period of days.  That is like 20 m3 from 30 or so sites over a week.  That is about one dumptruck worth per day (must be at least 4 m3 in a dump truck?)  A few thousand m per second launch velocity is easily achievable.  In aroura your mass drivers fire material at 1000 km/s.  Mind you doing this creates a hell of a no fly zone...

What about the stresses this is going to impose on the asteroid?  It's not a show-stopper, but it's not exactly trivial, either.

I would expect that during the hollowing out process you add an internal structure to support the shell to deal with any issues arising from the spin up process.  I will say again I don't see the practical value of doing it...as building a space station is likely easier and since you design it you can ensure that you don't get any surprises near the end of the process.  O'neil colonies are essentially identical objects and you best use of the asteroid would likely be as raw materials for the O'neil colony.

This I will agree with. 

[bean]

Thx for pointing out the flaw in my earlier calculation, I was going off some energy requirement numbers I found for a much larger body then modifying them based on possibly flawed calculation using the idea that double the mass would require a square of the energy.

Well, moment of inertia for a sphere is .4*m*r^2, so assuming constant density, MOI (I) will scale with mass^(5/3).  If the angular velocity is the same, that's how energy requirements will scale.  If we're trying to maintain a constant centrifugal 'gravity', then the required angular velocity(w) (neglecting local gravity, which will be proportional to the cube root of mass) will scale with 1/radius^.5.  Angular momentum is I*w, while angular energy is .5*I*w^2.  So angular momentum should be proportional to mass^(7/6) while energy is proportional to mass^2/3. 

I would debate that the energy requirement isn't ridiculous considering the kind of energy requirements needed for travel in aurora anyway, but it's obvious that it's not the most efficient way of making such a body habitable.

It's not the energy requirements themselves that are the problem, so much as what they imply for the structure.

Perhaps artificial gravity makes the most sense, or hell even magnetic boots or whatever would work enough to make a colony work, who cares about osteoporosis when earth is overcrowded and someone's offering you a free ride to an exciting new underground colony where you can spend 16 hours a day using a plasma torch to hollow out living space for people to be stacked like sardines into a plastic lined crate equipped with free wifi, stims, and robot hookers ™.

Osteoporosis is not the biggest problem with magnetic boots.  Bathing is.

[Wolfius]

You're over-thinking it, folks.

Don't spin the rock, build the habbitat in a circle or ring and spin that. Doesn't even need to be all of it, just enough of it that colonists will spend enough time there to remain healthy.


Complaints about UG infrastructure being weird because people assumed that normal infrastructure was by default underground are also backwards; it just means your assumptions were wrong. Which makes a certain level of sense; even prefabricated PDCs, which are underground complexes, need minerals and BP to assemble, while instalations you usually have to transport in segments can just be unloaded, so why would you just be able to dump kilotons of infrastructure on the surface and expect underground habitats? At most they'd be fairly shallow.


I like the idea of UG infrastructure as a specialist hostile enviroment alternative to the normal stuff you can mass produce and ship in from your empire, sometimes ending up with huge surpluses as worlds finish terraforming. It's specialised planet-specific infrastructure that addresses specific challanges and makes use of local conditions for best results; instead of just piling on more and more general-purpose stuff you build localised specialist equipment that is more expensive but also more efficent, effectivly reducing high colony cost values in exchange for other trade-offs.

[bean]

You're over-thinking it, folks.

Don't spin the rock, build the habbitat in a circle or ring and spin that. Doesn't even need to be all of it, just enough of it that colonists will spend enough time there to remain healthy.

While this is somewhat easier than spinning an entire asteroid, it's not trivial either.  Big wheels are delicate and difficult to build, particularly when you need to get people and stuff in and out without stopping them.  The other issue with 'only for health' is that gravity is generally better for operations than zero-G.  Bathing is the most obvious example, but even working at a desk is easier, as you don't have to worry about things floating away. 

[Theodidactus]

I ask again, wouldn't it be easier to just put magic transnewtonian floor panels all over the colony? This is sort of what I imagine anyway because when I play pretend, I don't like imagining my military high command on Euphrates colony (.30 gs on the surface) holding court in an environment where you can throw books like ping-pong balls. I think most of us imagine artificial gravity aboard our starships, maybe not.

[Steve Walmsley]

I ask again, wouldn't it be easier to just put magic transnewtonian floor panels all over the colony? This is sort of what I imagine anyway because when I play pretend, I don't like imagining my military high command on Euphrates colony (.30 gs on the surface) holding court in an environment where you can throw books like ping-pong balls. I think most of us imagine artificial gravity aboard our starships, maybe not.

I think the artificial gravity idea is definitely the simplest. However if we have artificial gravity instead of an underground colony, we have the issue of other environmental conditions, such as temperature. I suppose the argument could be that the low-grav infrastructure is effectively the same as crew quarters plus hull on a spacecraft but based on the ground. Just like a spacecraft it doesn't worry about the outside conditions. However, that isn't really any different that building orbital habitats, plus there is no reason not to build it elsewhere and ship it.

For RP reasons, I like the idea of the underground infrastructure because it leads to the idea of hollowing out small moons and asteroids. I agree that the existing techno-babble probably doesn't make sense though. I like the suggestion of rotating sections underground as that does leave the essential idea intact while having a reasonable scientific explanation. I'll give it some more thought. I'm also inclined to create some type of shipyard that can be built within an asteroid as a permanent fixture but not towed away (more for the idea of finding old abandoned but intact facilities than building new ones).

[wilddog5]

I think that Underground Infrastructure should act like cost 3.0 on all planets (except gas to be clear). This is because if you want to colonise a very hot planet it would make sense to make them underground where they are not exposed to the sun/environment the rock keeping the place cool while for a cold planet the rock would act as an insulator.

Thus setting a col on these worlds (5.0+) would go basic Infrastructure + factories/ construction team > Underground Infrastructure > Tforming if possible rather than just waititng for the planets to get Infrastructure via traders.

The benefit would be counteracted by the cost/extra management and would work really well as a concept for planets like Venus where it takes decades or more to TForm

[Theodidactus]

In my game I RP several of my colonies as being underground for a variety of reasons: one is located not that far from sirius and anything on the surface would be baked into cinders in minutes, ect. But my largest underground colony is basically the nucleus of my military. I imagine this colony is underground because it provides the following benefits which maybe the "real rules" for underground colonies can incorporate:

- it's easier to support tens of millions of people on what would otherwise be a lightless, airless world
- it is difficult to nuke from space
- it is difficult to SEE from space

[Jorgen_CAB]

From all the real science that I have read about realistic colonization of our solar system there are some fundamental problems. Gravity is one problem. Many even think that colonization of Mars will be a problem long term unless we can make everyone exercise a lot or there are new medical treatment for this in the future.

In my opinion infrastructure on planets would be both underground and above. I'm pretty certain most places that requires this infrastructure will be built by dome like structures where you have artificial atmospheres that shield from lethal radiation but at the same time can use the very important sunlight. Using pure underground facilities are not practical since you must fabricate healthy sunlight conditions.

If you build a base on any body in our solar system they would have to be mostly underground on the basis of all the lethal radiation. Things which an atmosphere shields from. Radiation would be a much bigger problem than gravity in many ways.
So, building a colony deep inside an asteroid save you a lot of resources from shielding you of that radiation. In our asteroid belt the big bad boy is Jupiter that spew out very harmful radiation which make human travel to the asteroid belt very dangerous. Short trips when Jupiter is not near is not a problem, but more permanent installation would be a problem.

I usually go with the solution that trans-Newtonian technology include artificial gravity in some form. Bases in asteroids would use that, and building them upside down might still be a good idea even with anti-gravity. I also see the reason for why such installations is very expensive and permanent.

That's my two cents worth of information...  

[Mel Vixen]

Spinning "rings" inside Asteroids and lowgrav moons would  be interresting AND it would make sense with the 3.0 costs. You just need a ton of people for the maintenance with all the spinning and enginering.

Sunlight isnt that much of a problem. LEDs are rather good at immitating that one. You would have halls and internal domes with artificial skies for the psychological effects (Small rooms and tunnels make us depressive no matter what the conditions are) either way.

Depending on the distance between star (if even it has the right spectrum) and asteroid you will want to shield yourself from the sunlight if you are to close thanks to the UV output. On the outer Asteroids  the sun is to week to give you your healthy dose UV...or enough light to see. In both cases you would opt for some sort artificial light powered either by solar or some sort of generator.