Elon Musk says he will put millions of people on Mars.

[D Tibbets]

One misconception (not mine I hope)-
The Earths magnetic field is not a result of friction between a rotating core and the mantle- continental drift, seismic activity, etc. It is due to the dynamo effect of the Earths rotating liquid (iron) core. If the core was solid, then there would be no magnetic field as there cold be no differential rotation. There might be configurations that would work- solid inner core, liquid outer core, etc.
I don't think Mars has a liqud core. Most of the measured magnetic fields are localized fossel fields, possibly remnants of iron asteroid impacts. And the magnetic field only protects from solar wind= charged particles. UV radiation is a different concern.

As far as water , I think Mars has lots, it is just buried in higher latitudes,. You would need to mine for it, and perhapas only to a few feet depths.

As far as heating it up, water is a much better green house gas than CO2, it would feedback to heating once you could get enough into the air.

As far as spinning up the planet with a large asteroid impact, it certainly could happen. To do it purposefully would be be difficult to say the least.
But, here you are adding angular momentum to the whole planet. Demolishing/ liquifying the crust, probably losing most of the water already present. And this would not necessarily liquify the core, It might create some differential rotation of the planet layers, and this might create a dynamo effect that lasts for millions of years. And after only a few hundred millions of years the surface may be seismically stable enough to risk living on.

In the long term view, Mars may be relatively attractive. In a few billion years when the Sun goes to rad gient, the Earth will be uninhabitable. Even very deep bunkers would only buy a few thousand years. Mars would then be very warm, if not too warm- need space mirrors diverting light away as opposed towards the planet. Mar's gravity and atmosphere(if it survives long enough) may be much more attractive than living on asteroids (as Ceres being a possible exception.

The only pratical reason I can see for living on Mars is a Goldilocks scenario. The gravity well is much easier to escape than Earth's, yet it is great enough to be comfortable. And with a large space based civilization, it might be more economical to exploit the Martian resources- mining, manufacturing, launching compared to Earth, or other extremely small moons and asteroids. The Earth's Moon would be attractive in this respect, except for the scarcity of water. The small moons of Mars would also make excellent space stations.

PS: I'm not sure the sSolar Wind, cosmic ray radiation would be a proble on Mars. The martian atmosphere, thin as it is may be evough to protect against this. It is the UV radiation that might be the major concern. The solar Wind is mostly high speed protons, they are not very penitrating. It is the secondary radiation they produce that is a problem for space craft. If the protons meet there fate in the upper Martian atmosphere, ther is miles between the you and the decay products. Many products would further decay or be absorbed befor reaching you. The biggest problem with lack of magnetic fields is that the solar wind strips away light elements away from the top of the atmosphere much quicker. Hydrogen and thus water is depleted much more rapidly. That is part of the reason why there is very little water on Venus.


Dan Tibbets

[GIThruster]

While I love the intentions of colonizing space, I still think it's absurd to even postulate how to do it without a "SpaceDrive". Once you have propellantless propulsion, all the numbers are so changed that it overwhelms. If we can believe any of the evidence that someone is visiting Earth, either what we ignorantly call "aliens", "UFO's", "saucers" or "ancient ancestors", or whether we believe such sightings are best described as humans traveling through time, either/or, the evidence is that SOMEONE is using some advanced form of propulsion that makes a mockery of rocketry.

IMHO, it's not a worthy endeavor to expend precious brainpower on how to colonize using rocketry. We need to solve the "SpaceDrive" puzzle as defined by Marc Millis during his Breakthrough Propulsion Physics review a decade ago.

So just saying, look forward to Woodward's coming book on how to build propellantless propulsion, warp and wormhole. Mach Effect physics has the answers we seek and IMHO, there is already sufficient evidence that this is not fiction, to focus on M-E physics to the tune of a Manhattan Project type endeavor. Certainly, we need more evidence that the physics is correct before we spend hundreds of billions of dollars on it, but even a million dollars would yield answers that could make all Musk's plans, old hat.

Why even consider trillion dollar investments with no financial return, when a program of space exploitation many orders magnitude cheaper and that would pay for itself, is within our grasp?

why, Why, WHY?

[Betruger]

Because there's no such certainty such a thing's "within our grasp".

[Skipjack]

We aren't going to sit around on Earth surface doing nothing for millenia, waiting to reach this technological readiness. Colonization now is better

I would not sit arround for millenia. The moon is close and we should be able to colonize it in the near term.

The Earths magnetic field is not a result of friction between a rotating core and the mantle- continental drift, seismic activity, etc. It is due to the dynamo effect of the Earths rotating liquid (iron) core.

True.

I don't think Mars has a liqud core. Most of the measured magnetic fields are localized fossel fields, possibly remnants of iron asteroid impacts. And the magnetic field only protects from solar wind= charged particles. UV radiation is a different concern.

I read that Mars does have a very weak magnetic field. I think that Mars' core is not completely solid, but that there is not enough rotation going on anymore. Also, the rotation itself should provide for heating and thus liquidation. Either way, the problem is that if you were to create an atmosphere on Mars with whatever means, without a strong enough magnetic field, the solar wind will just blow it away again.

UV radiation is a different concern.

Yes, you need an atmosphere for that.

As far as heating it up, water is a much better green house gas than CO2, it would feedback to heating once you could get enough into the air.

Yes

But, here you are adding angular momentum to the whole planet. Demolishing/ liquifying the crust, probably losing most of the water already present. And this would not necessarily liquify the core, It might create some differential rotation of the planet layers, and this might create a dynamo effect that lasts for millions of years. And after only a few hundred millions of years the surface may be seismically stable enough to risk living on.

Hmm, as I said, it would have to be calculated well. It is only a theory that I am toying with anyway. I could imagine colonists being able to settle on the side of the planet opposite to the impact crater first. It would certainly be tough and no walk in the park, but I am sure it would be manageable for a civilization advanced enough to do the feat I described.
In any case one could use smaller more focused impacts to just evaporate the frozen water to cause a green house effect and add more atmospheric pressure too. The problem is that the solar wind will gradually blow that atmosphere away again, if there is no magnetic field protecting the planet.

[Skipjack]

While I love the intentions of colonizing space, I still think it's absurd to even postulate how to do it without a "SpaceDrive". Once you have propellantless propulsion, all the numbers are so changed that it overwhelms.

I think that fusion propulsion as proposed by several different entities would be enough for colonization of the solar system, which should be the mid term goal (next two millenia or so). That could be in reach soon.

[GIThruster]

IIUC, fusion has a much lower power density than fission. Fusion rules when it comes to avoiding nasty by-products; not in what it takes to generate propulsion.

Either way, fission and fusion rockets CANNOT give us cheap and easy access to this planetary system, and certainly not the stars.

[williatw]

On earth our shielding from radiation from space is both the earth's magnetic field and our thick atmosphere. After all my understanding is during pole shifts the earth's magnetic field fails for an unspecified period of time. The last one was about 700,000 yrs ago. If our atmosphere gave us no protection from space radiation, then there should have been a massive die off of life on earth(which there wasn't). The fact that we are here proves that (think homo erectus was around then). The super greenhouse gas would cause the CO2 and water to outgas, doing most of the warming. We would end up with a thick atmosphere warm enough for liquid water to exist on the Martian surface. Said thick atmosphere would give us considerable some protection from space radiation. Also a domed over crater could have and inner an outer dome with water filling the space in-between. Water makes good shielding. You could also have superconducting cables set up above the domed crater that would deflect away incoming charged particles from the Sun or cosmic rays.

[williatw]

IIUC, fusion has a much lower power density than fission. Fusion rules when it comes to avoiding nasty by-products; not in what it takes to generate propulsion. Either way, fission and fusion rockets CANNOT give us cheap and easy access to this planetary system, and certainly not the stars.

The stars I would agree..but why the solar system? If Musk succeeds in building cheap reusable chemical rockets to orbit why couldn't nuclear rockets be used from earth orbit and beyond? Nuclear powered upper stage of chemical rocket not switched on until beyond earth's atmosphere. Eventually larger more massive nuclear powered vessels launched by reusable chemical rocket by components and assembled in earth orbit, for use going from earth orbit to mars orbit and beyond. I am assuming you don't think nuclear rockets could ever be made reusable?

[GIThruster]

Well I do think something like TRITON could give us a cheap enough propulsion system for explorers to take us vicariously to other worlds in our system. That's why I made the recommends I did to the Augustine commission. However, that doesn't mean such a system could ever be economical enough to take the average Joe off planet.

Forget billionaires' dreams. For the average Joe to use space transport much as he does modern age air transport, we need to reduce the costs many more orders magnitude than what chemical, fission or fusion can give. We need to leave off with rockets of all sorts and have a propellantless form of propulsion.

[Aero]

... Also a domed over crater could have and inner an outer dome with water filling the space inbetween. ...

This sounds like a good idea, but if you are thinking about having a breathable atmosphere under the dome, there is a problem. It has to do with the difference in pressure needed for humans to breath under the dome, and the existing pressure of the Mars atmosphere. On Mars, the "mean sea level" atmospheric pressure is 0.087 psi while pressure under the dome would need to be near 10 psi. A small habitat dome of maybe 1000 square feet (~ 92.9 square meters) would experience a lifting force of 1,440,000 pounds, or over 700 tons, (~650 tonnes) due to air pressure. A large dome over a crater would experience a large lifting force from air pressure. Need a really good anchor system, or a lot of water in the layer between the domes to weigh it down. How much water? Mars gravity is ~38% of Earth gravity and 650 tonnes of water is 650 cubic meters on Earth, but on Mars you'd need 1710 cubic meters of water weighing down the 92.9 square meter dome. That is, you need 18.4 meters or 60 feet of water to keep your internal atmospheric pressure from blowing your dome away. One nice thing is, though, you could make a very big dome, over a crater say, and 60 feet of water would still hold it down.

Of course, the above only considers one design. Their must be a way to anchor domes on Mars. But big domes are going to be hard to stablize. For example, seal an underground lava tube to live in, but don't let it blow out from internal pressure.

[williatw]

Well I do think something like TRITON could give us a cheap enough propulsion system for explorers to take us vicariously to other worlds in our system. That's why I made the recommends I did to the Augustine commission. However, that doesn't mean such a system could ever be economical enough to take the average Joe off planet.

Forget billionaires' dreams. For the average Joe to use space transport much as he does modern age air transport, we need to reduce the costs many more orders magnitude than what chemical, fission or fusion can give. We need to leave off with rockets of all sorts and have a propellantless form of propulsion.

Perhaps...but if you are talking about a permanent mars colonist, he/she is making a once in a lifetime trip. And if the consortia that I hope finance the bank of mars foots the bill no problem. Also long term the value of colonizing space is that the human race gains access to the material and energy resources of the solar system at large. Thousands of times the recoverable resources than on earth alone. Hopefully insuring our long term survival. Even if >99% of the human race stays on earth the space wealth would effectively make our footprint on earth less. Move the polluting high energy processes in space where there is room. Powersats, asteroid mining, I mean screw the lunar He3, the atmospheres of the gas giants for instance contain trillions of tons of He3. Anti-matter can even be mined/produced by taking advantage of the natural high energy particle stream from the sun and using the magnetic fields of the earth(an eventually the gas giants stronger fields) to funnel it to some kind of target. http://nextbigfuture.com/2011/08/confir ... apped.html

[williatw]

This sounds like a good idea, but if you are thinking about having a breathable atmosphere under the dome, there is a problem. It has to do with the difference in pressure needed for humans to breath under the dome, and the existing pressure of the Mars atmosphere. On Mars, the "mean sea level" atmospheric pressure is 0.087 psi while pressure under the dome would need to be near 10 psi. A small habitat dome of maybe 1000 square feet (~ 92.9 square meters) would experience a lifting force of 1,440,000 pounds, or over 700 tons, (~650 tonnes) due to air pressure. A large dome over a crater would experience a large lifting force from air pressure. Need a really good anchor system, or a lot of water in the layer between the domes to weigh it down. How much water? Mars gravity is ~38% of Earth gravity and 650 tonnes of water is 650 cubic meters on Earth, but on Mars you'd need 1710 cubic meters of water weighing down the 92.9 square meter dome. That is, you need 18.4 meters or 60 feet of water to keep your internal atmospheric pressure from blowing your dome away. One nice thing is, though, you could make a very big dome, over a crater say, and 60 feet of water would still hold it down. Of course, the above only considers one design. There must be a way to anchor domes on Mars. But big domes are going to be hard to stabilize. For example, seal an underground lava tube to live in, but don't let it blow out from internal pressure.

Well the water could be continuously filtered(so you could see the stars/sun through it) and perhaps in partitions that could be emptied filled as needed to stabilize the dome. Sixty feet thick of water is a lot of shielding, Marsopolis should be pretty safe for pregnant women young children. After the martian atmosphere thickens up..you could reduce the amount water between the domes

[KitemanSA]

Can you say "O'Neill"?

Years ago I read that weightlessness causes severe atrophy of muscles and bones, and that it is impossible for the human body to remain healthy for long periods of weightlessness.

Living in the weightlessness of space is not something the human body can evolve to tolerate in the short term. It is contrary to our current nature. Now if someone could come up with some artificial gravity...

I repeat, can you say O'Neill? Large spinning colonies, centripital acceleration in lieu of gravity.

[KitemanSA]

then again, why would anyone in theoir right mind climb out af a deep well only to jump down another?

Once you are in space, colonize SPACE.

Can you say "O'Neill"?

The problem is that you have to bring all that material to make an O'Neill colony up the gravitational well too. So I am not so sure that you would really save that much energy.

Wow, try wiki-ing the name/concept before making such statements. Moon? Asteroids?

[GIThruster]

Well I do think something like TRITON could give us a cheap enough propulsion system for explorers to take us vicariously to other worlds in our system. That's why I made the recommends I did to the Augustine commission. However, that doesn't mean such a system could ever be economical enough to take the average Joe off planet.

Forget billionaires' dreams. For the average Joe to use space transport much as he does modern age air transport, we need to reduce the costs many more orders magnitude than what chemical, fission or fusion can give. We need to leave off with rockets of all sorts and have a propellantless form of propulsion.

Perhaps...but if you are talking about a permanent mars colonist, he/she is making a once in a lifetime trip. And if the consortia that I hope finance the bank of mars foots the bill no problem. Also long term the value of colonizing space is that the human race gains access to the material and energy resources of the solar system at large. Thousands of times the recoverable resources than on earth alone. Hopefully insuring our long term survival. Even if >99% of the human race stays on earth the space wealth would effectively make our footprint on earth less. Move the polluting high energy processes in space where there is room. Powersats, asteroid mining, I mean screw the lunar He3, the atmospheres of the gas giants for instance contain trillions of tons of He3. Anti-matter can even be mined/produced by taking advantage of the natural high energy particle stream from the sun and using the magnetic fields of the earth(an eventually the gas giants stronger fields) to funnel it to some kind of target. http://nextbigfuture.com/2011/08/confir ... apped.html

Keep thinking that way and you guarantee we get nothing done. This is the O'Neil nonsense that has left us with no progress in space the last 5 decades. So long as space advocates lie to themselves about how space can be made a viable economic option, we'll have these inane dreams supplanting real plans.

ROCKETS WILL NOT WORK. They are not safe, they are not quick, they are not convenient and they are not economical. ONLY A SPACEDRIVE CAN YIELD AN INTERPLANETARY SOCIETY.