Ceres

Terraformer · 2008-01-25 07:20:34

Unshielded habitats! In deep space! What person would live in those? You'd be dead pretty quickly of radiation sickness. Unless you dosed up on antiradiation drugs, that is.

Antius · 2008-01-25 09:52:04

Unshielded habitats! In deep space! What person would live in those? You'd be dead pretty quickly of radiation sickness. Unless you dosed up on antiradiation drugs, that is.

The modest amount of shielding provided by the structure of the habitat and pressure vessel would shield out 1MeV solar storm particles. Zubrin gives a good analysis of solar storm shielding in 'Case for Mars'.

For galactic cosmic rays, only very thick layers of shielding weighing tonnes per square metre will give full protection. Cosmic radiation will give doses of 30rems per year to unshielded personel in free space, but the dose will be spread over the whole 365 days. A healthy diet full of antioxidants will counteract most of the damage.

qraal · 2008-01-25 15:25:18

Hi Guys

Unshielded habitats! In deep space! What person would live in those? You'd be dead pretty quickly of radiation sickness. Unless you dosed up on antiradiation drugs, that is.
For galactic cosmic rays, only very thick layers of shielding weighing tonnes per square metre will give full protection. Cosmic radiation will give doses of 30rems per year to unshielded personel in free space, but the dose will be spread over the whole 365 days. A healthy diet full of antioxidants will counteract most of the damage.

One advantage of a bag colony - a few kilometres of air stops GCRs dead (turns them into muon showers.) Are muons sufficiently like beta-rays to be innocuous, or are they more penetrating? They contribute to ~50% of our normal dose of rads though, so our bodies are adapted to them.

GCR damage isn't something easly repaired by the body. They kill non-regenerating cerebral neurones directly - and so GCR damage would progress like Alzheimer's disease with its gradual decline into full dementia. Regular radiation is just in the MeV range, so the body can fix it easily - but +GeV energies leave a track through the body of damage that's hard to fix.

Personally I think John Slough's Plasma Magnet might be the best GCR shielding option. And its mass-density requirements are much lower than a basalt shield. But a few metres of asteroid regolith does the job just as well - thus my preference for digging in on an actual body in space.

Terraformer · 2008-01-25 16:26:54

Thanks for all the ideas and thoughts guys, I think a World Grenhouse woud be the best idea. Ceres has 2.4% of Earths gravity, so such a sky could be supported by literal sky/spacescrapers. The Silicon for the roof would most likely be mined from nearby asteroids. If we have fusion by then (which we should have) lasers on top of the spacescrapers could shoot down debris large enough to pose a threat. A space elevator would be used to catch incoming spacecraft and transport them down to the surface. Any thoughts?

nickname · 2008-01-26 06:59:39

Antius,

Micro gravity is now pretty well documented to the effects it causes.
I think right around 18 months is the serious problem point for humans in near 0g.
Beyond that point humans returning are a little like jello.

On the moon at 1/6th G or Mars at 1/3rd G we just don't have any idea what that does to a human body.
We might encounter a totally different set of problems at partial G.
Almost a guarantee that human biological systems that rely on gravity that get partial returns are going to be pretty mixed up.

I also doubt that staying on Mars for 18 months would be a death sentence, overstated a bit.
But we might find that partial gravity is much worse than 0g on a human body.
Or we might find that partial gravity just extends the stay limit much further than 0G.

We can also compensate a bit on the Moon or Mars with 8 hr exploration walks that require lots of heavy equipment moving in heavy space suits.
Muscle and bone loss should be kept to a minimum doing that.

Interesting that it's such an overlooked issue with going to Mars.
Guess we will get some answers when people are on the moon for extended stays.
Partial G really has a potential to make a human body have all sorts of hormones and glands doing odd things, brain chemistry, cell chemistry etc.

JoshNH4H · 2008-01-26 16:22:57

on ceres, a space elevator would definitely be feasible. Steel or kelvar could do it for sure. and to catch interplanetary ships, just extend it so the end is at interplanetary velocity. Then catch them.

I'm really unsure as to weather .024 g's is really enough to be healthy, though. Most people should sleep in centrofuges.

qraal · 2008-02-09 03:04:37

Hi All

I wasn't satisfied with rough guessing what an atmosphere would do on Ceres, so I set up an iterative model from first principles and have some rough results.

Assumptions -

I haven't tried to model heat absorption, but might eventually.
mass: 9.5E+20 kg
rotation: 9.074 hours
equatorial radius: 483 km

Assumed constant Cp for the gas mixes - which is true (within a few %) for N2/O2, but CO2 changes a bit over the temperature range worth considering for humans. I used a rough average.

Rotation rate means Ceres effective gravity is zero at a radius of 1196 km on the equator. Things will be different for the poles. It's also assumed the atmosphere is rotating rigidly with the surface.

Results:
Po - surface pressure
P1 - pressure at synchronous altitude
To - surface temp
T1 - temp at synch
Do - surface air density
D1 - density at sync

Po P1 To T1 Do D1 Mass
1.01E+05 2.29E+03 2.88E+02 1.76E+02 1.22E+00 4.53E-02 8.60E+05
2.50E+04 3.79E+02 2.88E+02 1.76E+02 3.34E-01 8.28E-03 1.99E+05
2.50E+04 1.72E+02 2.88E+02 1.76E+02 3.97E-01 4.46E-03 1.79E+05
2.50E+04 8.85E+01 2.73E+02 1.48E+02 4.18E-01 2.73E-03 1.70E+05

Sorry it's not a proper table. The Mass column is the Mass (in kg) of the atmosphere (per sq. metre) up to the synchronous altitude. As you can see the atmosphere does rariefy quite substantially. More discussion later.

qraal · 2008-02-11 17:13:13

Hi All

Firstly, the surface escape velocity of Ceres is about equal to the thermal speeds of breathable air, so its atmosphere will leak away. But a mass of air won't just explode freely into space - if its pressure is higher than ambient and its path-length is small, then the gas does work against itself and cools as it expands. So the air traps itself a bit.

Secondly the gravity declines as fast as the volume of individual layers of air increases - meaning the effective weight is constant at all altitudes in an isothermal atmosphere without rigid rotation. Factor in an adiabatic cooling profile and that means the atmosphere thins quite a bit at altitude. The maximum altitude is Ceres' Hill Sphere at 77,400 km radius. Beyond that and the gas is orbitting the Sun, not controlled by Ceres' gravity, but it should thin out to solar wind density before then.

But the solar wind wouldn't need to do much work to scrape away the outer layers. Unlike places like Earth, Venus or even Mars. I would say an atmosphere on Ceres would be marginally stable - it might stick around, or it might not. If we began with an isodense layer then let it freely expand, then it would cool significantly, perhaps creating a cold trap sufficient to keep some air down... if it wasn't for the damned Sun heating it up again *sigh*

JoshNH4H · 2008-02-13 15:48:17

I would say that terraforming ceres in the traditional sense would be nearly impossible.

Antius · 2008-02-14 11:27:54

Hi All
Firstly, the surface escape velocity of Ceres is about equal to the thermal speeds of breathable air, so its atmosphere will leak away. But a mass of air won't just explode freely into space - if its pressure is higher than ambient and its path-length is small, then the gas does work against itself and cools as it expands. So the air traps itself a bit.
Secondly the gravity declines as fast as the volume of individual layers of air increases - meaning the effective weight is constant at all altitudes in an isothermal atmosphere without rigid rotation. Factor in an adiabatic cooling profile and that means the atmosphere thins quite a bit at altitude. The maximum altitude is Ceres' Hill Sphere at 77,400 km radius. Beyond that and the gas is orbitting the Sun, not controlled by Ceres' gravity, but it should thin out to solar wind density before then.
But the solar wind wouldn't need to do much work to scrape away the outer layers. Unlike places like Earth, Venus or even Mars. I would say an atmosphere on Ceres would be marginally stable - it might stick around, or it might not. If we began with an isodense layer then let it freely expand, then it would cool significantly, perhaps creating a cold trap sufficient to keep some air down... if it wasn't for the damned Sun heating it up again *sigh*

Excellent analysis. Would the conclusion be markedly different for outer solar system bodies of a similar mass? For an outer solar system body, it would make more sense to employ artificial light and heat sources on the surface, than to attempt to concentrate extremely meager sunlight.

The gas escaping would escape from the top layers of the atmosphere and would consist mostly of ions. These respond to magnetic fields.

JoshNH4H · 2008-02-14 15:13:27

how would a mag. field affect that?

Antius · 2008-02-15 06:47:06

how would a mag. field affect that?

Electrically charged ions will spiral along magnetic field lines. A planetary magnetic field has the effect of trapping ionised gas, which eventually re-enters the atmosphere at the poles.

The effect can be seen on a massive scale in the vicinity of Jupiter, where the magnetic field acts as a gigantic trap for solar wind ions. The ions at the top of a planetary atmosphere are generally thermalised, with energy orders of magnitude lower than solar wind ions. So a more modest magnetic field should be sufficient to recycle Ceres' escaping atmosphere.

An important question with Ceres is whether terraforming is worth the effort. In the near future one would get far more money's worth by concentrating terraforming dollars on Mars.

JoshNH4H · 2008-02-18 11:41:29

I personally would have to say that it isn't worth the effort.

karov · 2008-02-18 12:51:54

Ceres -- OF COURSE the gravity is not enough to hold atmosphere.

1. Artificial / DESIGNER magnetosphere can do it. The advantage vs. "hardtop" paraterraforming is that with magnetically confined gas envelope we have uninterrupted interface surface-space. The other advantage is that planetary magnetic "bottle" is active / "kinethic" structure. Adaprtive one, with positive backfeed -- as stronger the factors which usualy blow an atmosphere away, as stronger the retention.

Ceres receives about 8-9 times less intense EM and particle insolation.
Designer Magnetosphere ( DMS ) could suspend smart "dusticles" which to provide multiple functions -- tropopause thermal super-trap for volatiles cryopreservation, magnetic and elecctric effects, optic effects. DMS with say, Saturn radius could be running enormous number of functions -- local, global, and inter-planetary. Functions -- optical, greenhousing, chemical & plasma processing, ...
DMS dusticles converting 2-3% of the falling light into usefull energy from radius of dozens of thousands of km... That is times more energy than captured by Earth, hence plenty of energy to process and KEEP gasses around and to EXCHANGE gases with the interplanetary medium.

Yes, such environment will be quite strange -- one could build "skyscrapers" from traditional materials ( say sinthered water ice ) from the very core of Ceres, up to above the Hill radius... Ceres "nature" will be more than 30 times more 3D than the Earth`s one. The bottom of the 1000km deep atmospheric ocean will be bizare place, organisms adapted rather to swim in it than to fly.... photosynthesis concentrated in flying or super-high "trees" with provided vertical paths for the chemical circulation... If designed sub-zero-celsius open environment the water could be exchanged "bottled" or "plumbed" into the biota.

IN SHORT -- I think that any mass of gas, equipped with the necessary plasmic hardware could hold it self together around any body or no body at all. The presence of Ceres-type dwarf planet inside the plasmically self-supporting air cloud is convenient, cause the solid body inside is ready concentration of usefull mass, and that mass provides some G help to the DMS , thus easing the energy processing task.

Hope to have time soon, to put some scenario, with figures and proofs

RickSmith · 2008-02-22 00:03:46

This topic is being moved from the "Reheating the Martian Guts" thread.

Hi RickSmith,
I agree the idea won't work on a body without an atmosphere.
We can't cheat on Ceres to dump rotational energy to the atmosphere.
It might work on Mars because we can dump rotational energy to the atmosphere.
If we fire west with just enough force to soak most of the launch energy into the atmosphere the impactor returns with no east energy.
Now all we would need is a reason to do such a thing on Mars.
To true about moving Ceres being a bit off topic.
Started as a way to re start the core of Mars but the mechanics of moving it expanded it.

Hi Nickname,
It won't work even if it is done on a planet with an atmosphere.

Let us say that we cover Ceres with a thick atmosphere.

Then we build a huge mass driver on the equator pointed east. We take a mass equal to 1/100 of Ceres mass and blast it out of the mass driver in such a way that it pulverizes to dust and sets the atmosphere spinning.

Let us say that we fire the mass fast enough so that Ceres stops rotating completely. OK. Now what happens to these mega-hurricane force winds? They blow up against the sides of craters, they blow against the mountains and ridges and any valleys.

That angular momentum is conserved. As the spinning wind slows down, it pushes on the craters, mountains, etc. and spins up the planet.

Another example, you have a space craft with a big gyroscope centered exactly at the center of mass. You want to point the ship in another direction. You spin it up, and the ship slowly starts rotating. You then slow it down and the ship stops again pointing the way you want. You have taken energy, converted it to angular momentum. However A. momentum is conserved so the ship has to rotate slightly in the opposite direction t

Terraformer · 2011-12-26 18:29:19

Grrr. The first post is quite embarrassing on this thread (though the territorial claim still stands), as are a lot of my posts. Anyway, we had a lot more about terraforming Ceres before the Great Crash of '11... it's quite a shame.

What would the scale height be for a CO2 atmosphere at 223K? Using mgz = kT, on the assumption previously mentioned that effective gravity can be considered constant, and ignoring rotation for the moment, I get a scale height of... well, it's on the scale of picometers, so my calculations wrong. Using mgzR/R(s) = kT... I still can't get it to work. How does H = kT/mg work anyway, since it should always come out to be ridiculously low given how small k is...

Terraformer · 2011-12-26 18:46:09

Ah, problem sorted. I was using Mr rather than m... : embarrassed:

Anyway, now that that's sorted... I'm getting a scale height of 156km for my atmosphere. Grrr, not good, since we're still talking about a pressure of 0.5mb when eff. gravity disappears. However, would the atmosphere rotate with the planet at high altitudes?

JoshNH4H · 2011-12-27 00:04:37

It is my understanding that the best way to model the rotation of the atmosphere is to hold the angular velocity constant, that way there won't be a significant velocity gradient between layers. Assuming you've been through some calculus, I would suggest re-deriving the equation for atmospheric pressure at height h taking into account the fact that the force due to gravity varies with changing altitude. The derivation shouldn't be too nasty, and it will give you a fairly accurate way to model an atmosphere. Sort of.

JoshNH4H · 2011-12-27 00:06:42

Oh, and also you still claim Ceres? I just wonder what you think that claim will actually mean in the real world...

Terraformer · 2011-12-27 05:03:02

Well, it depends who gets there first and stays, doesn't it? It's unlikely a colonisation mission will be launched before I'm old and rich enough to be the one launching it.

Hmmm, assuming a non-rotating planet, we'd need the scale height to be around 100km to have pressure fall by a factor of about 20000 when it reaches a synchronous orbit. That's a pressure of 10 microbars, though I'm still not convinced the atmosphere will rotate with the planet... still, that's an awful lot of drag on our space elevator station. I'd really like to get the scale height down to around 50km, but that requires copius amounts of very heavy gas, which is hard to come by in the forseeable future...

Terraformer · 2011-12-27 12:44:32

Error in the previous post - with a scale height just under 100km, it would only decrease by a factor of less than 3000...

For proteroforming, we're looking at >65mb pressure and >273K temperature during the summer months (given the length of the year - 4x the Terran one - and the size of the planet, it will probably be 6 month long seasons based on the eccenticity of the orbit, rather than ones based on the axial tilt). If the place is going to be worldhoused anyway, we need probably higher pressure (~100mb at least, ideally double this), though with a lower temperature. The atmosphere has to be non-toxic in the sense that a person could walk through it with only a respirator on and remain alive and without serious injury. Any gases that are suitable for this, and denser than CO2? I've thought of perhaps trioxocyclopropane, but I can't seem to find much information about it (okay, so a quick Google check reveals nothing in English about it) - anyway, the French version of Wikipedia says (using Google translate, neatened up by human reasoning - I don't even know French):

However, this compound appears to be thermodynamically unstable [2]. In 2010, it has not yet been synthesized in significant quantities, but in transient amounts, as detected by mass spectrometry[3] .

so there goes that idea. Perhaps trithiocycloprapane will prove better? Anyway, they're harder to get than plain old CO2...

A 60mb CO2/5mb O2 atmosphere that's above freezing would allow for life to exist on the surface, at least. Unfortunately, I get an approximate scale height of 200km, so unless we get lucky and the atmosphere doesn't rotate with the planet beyond a certain point that's lower than synchronous, the sprinkler effect is still in play. Damn. I suppose it'll have to be a Worldhouse, though a thin Martian style atmosphere for meteorite protection is not out of the question (160km scale heigh at 223K, so a 15mb atmosphere will be less than 150 microbars at sync). Of course, rotation changes things...

Rune · 2011-12-27 18:27:02

Err... what's the problem with having an elevator inside an atmosphere? Said atmosphere, through friction with the ground (and nothing else) would rotate with it and speed up (or down) until the relative angular velocity is zero. The elevator, by definition, would rotate at that same speed. Nothing moves with respect to nothing unless you pump energy into it.

Rune. I REALLY want to get back to my desktop computer soon. Posting by tablet is awful (which is why I'm not doing it, that and the holiday food).

Terraformer · 2011-12-28 10:18:44

Well, the issue is mainly that the atmosphere is weightless once you reach synchronous orbit, so it won't be bound to the planet any more. Certainly, the orbits within the atmosphere would be strange - a high subsonic (in the low density atmosphere) craft would be technically in orbit, so the wings mich have to be flipped around to keep it from leaving the atmosphere.

Terraforming - or even just Proteroforming - Ceres will be a lot easier if we can get hold of an abundant, suitably dense, non toxic gas. The closest we get to this is CO2... if we're going with a hybrid worldhouse, it's got to be something that is only toxic in large amounts (like CO2). Something like SF6 or Xenon would be ideal, but...

Now, if we could just despin the planet...

Rune · 2011-12-28 18:01:54

Terraformer wrote:

Well, the issue is mainly that the atmosphere is weightless once you reach synchronous orbit, so it won't be bound to the planet any more. Certainly, the orbits within the atmosphere would be strange - a high subsonic (in the low density atmosphere) craft would be technically in orbit, so the wings mich have to be flipped around to keep it from leaving the atmosphere.

It mat be weightless, but it will still be mechanically coupled with the lower levels of the atmosphere (there will be friction between them). Oh, and if it's weightless, it will eventually go away anyhow.

Of course, all of this is in an ideal setting with no outside influences and infinite time so things go to their lowest energy state. But it's still useful to grasp the general situation.

Oh, and to keep a wing from flying you out of orbit, you just have to set the angle of attack at a certain point. An upside-down plane CAN fly level.

Rune. Hopefully, helpful.

JoshNH4H · 2011-12-29 17:42:35

Terraformer- What Rune said wrt the atmosphere spinning with the planet. It won't happen immediately, but if the atmosphere doesn't spin with the planet there will be some pretty impressive winds. Those will eventually slow down the lowest levels of the atmosphere. Friction between that layer and the layer slightly above it will ultimately bring them to zero motion with respect to each other. The only way to prevent there from being motion between the layers is to keep the angular velocity constant.

Also, seeing as you're talking about the scale height as an absolute number, it doesn't seem that you're accounting for the attenuation of gravity, from its already low (IIRC) 5% of a g will only get lower as you get to GCO, especially if you account for centripetal acceleration.

Anyway, non-toxic gases made from available elements which are heavier than CO2: Kinda depends what kind of pressure you want. I know I suggested water for the Moon, from its vapor pressure. If you're looking for 60 mb, I'm sure there's something pretty heavy and fairly stable that has a vapor pressure around there. It doesn't need to be primarily a gas at room pressure, after all. You might want to look at butane, or even one of the pentanes. At 60 mb hydrocarbon to 5 mb oxygen, you shouldn't have a flammability issue, and they're not awful for health. You might also look at some kind of atmosphere with two gases, one an electron donor and the other an acceptor, so that they form a lewis acid-base pair and increase the effective molar mass.

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