Why colonize Mars and not the Moon?

[Stavros Kiri]

But what about gravitational equilibrium in the solar system? Also negligible? (i.e. the perturbation)

 

[mfb]

Deimos and Phobos are held together not by gravity, but by chemistry. It's hard to calculate the exact binding energy, because we don't know much about the interior structure and composition, but a ballpark estimate is that you need ~400x more energy to dissociate Phobos and 1000x more to dissociate Deimos.

Depends on how we want to disintegrate them. Your numbers would mean 40,000 MT for Phobos and 3,000 MT for Deimos. That is still possible. 400 and 30 Tsar bomba style (with the additional fission layer that got removed) nuclear explosions, respectively.

But what about gravitational equilibrium in the solar system? Also negligible? (i.e. the perturbation)

No matter what we do with the moons, it will have no notable effect on anything in terms of orbits. Mars has 60 million times the mass of Phobos and Deimos combined. If we bring the moons down (not trivial with angular momentum), the combined mass does not even change. If we shoot the moons away, the combined mass goes down by 1 part in 60 millions. Completely irrelevant.

 

[Stavros Kiri]

Depends on how we want to disintegrate them. Your numbers would mean 40,000 MT for Phobos and 3,000 MT for Deimos. That is still possible. 400 and 30 Tsar bomba style (with the additional fission layer that got removed) nuclear explosions, respectively.
No matter what we do with the moons, it will have no notable effect on anything in terms of orbits. Mars has 60 million times the mass of Phobos and Deimos combined. If we bring the moons down (not trivial with angular momentum), the combined mass does not even change. If we shoot the moons away, the combined mass goes down by 1 part in 60 millions. Completely irrelevant.

I meant more the forces from the sun and other planets to the moons etc. (that could affect the dynamics of the system - not trivial!) , not the mass itself! That could have been a problem, but may be also negligible. What do you think?

 

[Stavros Kiri]

May be use "small perturbation theory" (on the forces and orbits) ...
The result may be from negligible to ... disasterous (or even chaotic?) to the solar system ... . It depends. As I said, ... not trivial! ...

 

[Stavros Kiri]

Disturbing the equilibrium of a system can always be a problem ...

 

[256bits]

Thanks for correcting us on that one! (simple mechanics! ...)

Just some minor "marsquakes" perhaps ...

Why don't you do some simple calculation before accepting a statement as fact.
You do know the universal law of gravitation.

Pick instead of a moon revolving around a planet revolving around a star.( centre of mass of moon-planet revolving around the star )
Pick two objects of equal mass revolving around their centre of mass far from other objects.

Stop one object in its tracks wrt the centre of mass ( and a line from the COM and the object ) with a "brick wall".
Remove the brick wall - do the objects fall into one another? Does the orbits of either change? Has the COM changed in any way?
( Note: The second object will continue to have an unchanged tangential velocity at moment of impact of the first with the wall )

Stop one object in its tracks wrt to the normal to the tangential velocity of the second object so that the first object acquires the same velocity parallel to the second.
Now do the objects fall into one another? Has the COM changed in any way?

Your conclusion?

 

[Stavros Kiri]

Why don't you do some simple calculation before accepting a statement as fact.
You do know the universal law of gravitation.

Pick instead of a moon revolving around a planet revolving around a star.( centre of mass of moon-planet revolving around the star )
Pick two objects of equal mass revolving around their centre of mass far from other objects.

Stop one object in its tracks wrt the centre of mass ( and a line from the COM and the object ) with a "brick wall".
Remove the brick wall - do the objects fall into one another? Does the orbits of either change? Has the COM changed in any way?
( Note: The second object will continue to have an unchanged tangential velocity at moment of impact of the first with the wall )

Stop one object in its tracks wrt to the normal to the tangential velocity of the second object so that the first object acquires the same velocity parallel to the second.
Now do the objects fall into one another? Has the COM changed in any way?

Your conclusion?

I think you may have read my partially humorous post backwards. I' ve already accepted all that. I know mechanics. But you analysed it for the others. Thanks.
But caution to all that conserv. of momentum is true only for closed systems (or Ftot = 0). So caution for the center of mass as well!
Your examples need to be studied and worked out ...

 

[mfb]

I meant more the forces from the sun and other planets to the moons etc.

I don't understand that sentence.

Even Mars (the whole planet) has a negligible influence on the orbits of other planets. 1/60 millionths of a negligible influence is really negligible.
Kepler orbits are closed, and all planetary orbits are stable over the lifetime of the solar system. Disturbing them a tiny bit, which happens all the time, does not matter.

There is no equilibrium in the solar system.

Please start a new thread if you want to discuss this in more detail, it seems to be off-topic here.

 

[Stavros Kiri]

I don't understand that sentence.

Even Mars (the whole planet) has a negligible influence on the orbits of other planets. 1/60 millionths of a negligible influence is really negligible.
Kepler orbits are closed, and all planetary orbits are stable over the lifetime of the solar system. Disturbing them a tiny bit, which happens all the time, does not matter.

There is no equilibrium in the solar system.

Please start a new thread if you want to discuss this in more detail, it seems to be off-topic here.

The prevailing force is the sun's ...
But I agree ...

 

[Dale]

a total exposure of 1 Sv for a 30 month (6 months going to Mars, 18 months on Mars, and 6 months getting back to Earth) mission duration.

I am going through your references, but 1 Sv dose corresponds to a 5.5% increased lifetime risk of cancer. Describing that as "risky" is fine, but describing that as "suicide" is not an accurate statement at all and it is far from "certain".

I will look through the references, but my skepticism about your claim of "certain suicide" seems justified by the 1 Sv dose you mentioned.

Edit: I finished reading all of each of the references you cited. Not one of them explicitly makes the "certain suicide" claim. Not one of them implicitly justifies the claim. Two of them confirmed the 1 Sv dose, and one confirmed the 5.5% increased risk of cancer. The typical claim that they made was that it is "not exactly a risk-free activity". Frankly, citing those as sources for your characterization as "certain suicide" is a substantial misrepresentation.

 

[Vanadium 50]

orresponds to a 5.5% increased lifetime risk of cancer

And 3.4% of astronauts have been killed on missions, a very similar number. It's risky, sure, but hardly suicidal, and not a huge amount riskier than what is already deemed acceptable.

 

[Dale]

es.
LEO -> Moon surface needs 5700 m/s.
LEO -> Mars surface with aerocapture needs ~4300 m/s, depending on the launch window.
The advantage of Mars is the atmosphere. Going back needs much lower delta_v starting from the Moon, of course. But even starting from Mars, a single stage rocket can work. The same rocket that landed on the surface, which means you just need to fuel it. And that is easier on Mars...

That is truly surprising to me, but very interesting. Certainly Mars is further away in actual distance, but in a very real engineering/economic sense it is closer. In principle, you could ship cargo to Mars less expensively than to the moon since you wouldn't have to worry about cargo getting there fast like you do have to worry about with passengers.

 

[gleem]

One aspect of establishing a independent base on Mars has been only lightly touched on and that is the logistics of setting up a base. Ships cannot be sent to Mars (at least in the foreseeable future) arbitrarily at any time. so that imposes a minimum time restriction on such a project. The previously proposed time for the completing of this project of ten years is out of the question as noted before. Aside from the window of opportunity issue It is fraught with so many unknowns that even a century might be too short of a time but maybe not. Setbacks will undoubtedly occur that will slow down progress. However if ships where prepared to be launched at every window of opportunity about every 26 months you would have about 46 missions available in that century Although probably not launched from the surface. Ships assembled in an Earth orbit seem more likely.

Musk claims he will try and send humans to Mars in a 200 day trip by 2026 to begin a colony. That seems way optimistic. . NASA has said they could put humans on Mars about 2036 with enough money and I don't think they were considering a colony.

No one mentioned the average surface temperature is -80F or the frequent dust storms that might preclude the use of solar energy. One should think our experience in Antarctica might be of value as far as livability in extreme conditions are concerned.

Well I'm genuinely excited that we are actively working on this although I may not be around even to see the initial landing . But hey isn't it all about the trip?

 

[Vitro]

I think we first need to agree on what a colony is. To me it represents a permanent human settlement that's self-sufficient, as opposed to ISS or a research station in Antarctica which even though permanently inhabited they mostly only offer shelter and are fully dependent on external resupply. Self-sufficient doesn't necessarily mean it can produce everything itself and not need any supplies sent from Earth, but it should be able to source locally everything essential to sustain life and grow the colony. It also needs the ability to repair and manufacture every component that's part of the life support system without any help from Earth. Basically it needs to be independent in every aspect that's vital for perpetual survival, and only depend on Earth for non-essentials which cannot (yet) be produced locally. Let's face it, there's no way a space colony can count on Earth for ongoing resupply, politics and economics here change like the weather and public/private support for such an expensive program can vanish in an instant.

As to why we would even want to colonize another space rock, it depends on whether we are talking short or long term. For the short term it looks like we don't, at least not seriously enough, otherwise we would already be doing it. It seems the world has had other priorities after the '70s and continues to do so. Over the long term, so long we maintain or improve our capability to do it, it will happen eventually just because it's in our nature to be curious and explore.

But the big concern is that our ability to colonize space is in decline, not technologically but politically and economically. The cost of maintaining our society and fixing the world's problems keeps getting higher and many things take precedence over space exploration which is becoming a luxury the world may soon be unable to afford. So it's pretty much now or never, whether we have a good enough reason to colonize space or not, if we don't do it now there may not be a later and we'll be stuck on this rock forever, at least the current iteration of human civilization. Maybe the next iteration, if we don't get wiped out entirely, will regain the ability and have another chance to do it.

 

[mfb]

Where do those 10 years come from? No one plans to have anything colony-like on Mars in 10 years, so why does this number get picked up so often?

Musk's optimistic estimate is a few humans on Mars by 2026, with more coming every 26 months, reaching a population of a million and self-sufficiency around the end of this century ("within the next 50 to 100 years"). The latter is just an educated guess of course - we don't have examples of colonies on other planets.

No one mentioned the average surface temperature is -80F or the frequent dust storms that might preclude the use of solar energy.

It was mentioned, discussed, a source was found, and the issue of dust storms looks manageable.
A small Mars base will need heating, sure. A larger, potentially 3-dimensional base might have enough waste heat without dedicated heating.

The cost of maintaining our society and fixing the world's problems keeps getting higher

Does it? Absolute poverty is decreasing rapidly, life expectancy is rising nearly everywhere, often with shortening working hours, with more and more money spent on non-essential things. Crime rates go down in most places, ... It is hard to find any measure where the world isn't getting better every year.

 

[Algr]

By the time humans get to mars, the robots will be so advanced that there won't be any need for humans.

 

[lifeonmercury]

That would be the ultimate slap in the face to be outdone by robots.
With regard to blowing up Phobos to increase the gravity on Mars, I get it that it wouldn't make a huge difference. However, Phobos is in an unstable orbit and is getting closer and closer to Mars. Why not take care of the problem now and eliminate this threat to future Mars settlers?

 

[rootone]

By the time humans get to mars, the robots will be so advanced that there won't be any need for humans.

That's, um, an entertaining thought.
In 1000 years time there could be a self sustaining base on Mars entirely inhabited by robots.
Possibly robots smart enough to devise a plan to inhabit other solar system bodies.
Meanwhile human civilizations on Earth are just interesting historical data.

 

[mfb]

By the time humans get to mars, the robots will be so advanced that there won't be any need for humans.

Maybe. Maybe not. We don't know. Stating a possible future as fact is misleading.

If robots can do research at the level of humans, they can probably build rockets as well, and we can still go easily even if we don't have to,

 

[Algr]

Stating a possible future as fact is misleading.

That's just the nature of the future. Anything you say about it has a chance of not happening.

 

[Stavros Kiri]

In 1000 years time ...
Meanwhile human civilizations on Earth are just interesting historical data.

I still hope not ! ...

 

[Vanadium 50]

Musk's optimistic estimate is a few humans on Mars by 2026, with more coming every 26 months, reaching a population of a million and self-sufficiency around the end of this century

There is no way to do this without transporting 10's of thousands of people every launch window. I point out that the world's record is 0, attempts to send 4 are falling back at the rate of one year per year, and that the total number of astronauts is fewer than 600. It's 300x more than the summer population of Antarctica, a much more inviting place.

 

[Dr Wu]

Mars having a self-sufficient population of around a million by the end of the century does seem wildly optimistic, although I would dearly wish to be proved wrong here. Indeed, ushering in any kind of offworld self-sufficiency remains a formidible challenge, certainly for decades to come. It's worth bearing in mind that the astronauts aboard the ISS are essentially "camping" in space. They're like mountaineers - or perhaps a closer parallel - more akin to those research scientists based in Antarctica (I stand to be corrected here). We don't even know if the 37% surface pull of Mars will be enough to prevent all the disabling atrophying effects that come with living long-term in microgravity conditions. Perhaps advances in space medicine, implant technology, robotics and the like, may solve this and related challenges posed by Mars - or Luna for that matter. In the end, though, going to Mars will depend upon the will of the people, politics etc. But we still need inspirational writers like Robert Zubrin to keep that hope alive.

I understand that the orbit of Phobos, while slowly decaying, will remains stable for many more millions of years.

 

[mfb]

That's just the nature of the future. Anything you say about it has a chance of not happening.

Then don't pretend it would be sure. That is acceptable if the probability is basically 1 ("the sun will continue to exist tomorrow"), but not otherwise ("I will win the lottery tomorrow").

There is no way to do this without transporting 10's of thousands of people every launch window.

No one doubts that.

The first controlled powered flight was made 1903, the first transatlantic non-stop flight was 1919. By 1947 there were more than 10 commercial transatlantic flights per day.
In terms of reusable rockets (=the equivalent to reusable aircrafts), we are somewhere around 1902-1903.

I would expect much more people being interested in a trip to Mars compared to a trip to Antarctica.

 

[Vanadium 50]

The first controlled powered flight was made 1903...By 1947 there were more than 10 commercial transatlantic flights per day.

OK, so we went from the first controlled powered flight to ten commercial transatlantic flights per day in 44 years. The first manned spaceflight was in 1961, so 44 years after that was 2005. I think a reasonable conclusion is that manned spaceflight is not on the same curve.

And while your first thousand colonists will surely be attracted because "it's Mars!", I am not so sure how the last thousand will feel: Mars will have 999,000 people who have been there for up to fifty years, but it's more isolated and less comfortable than Antarctica. You still have the negatives, but it's hardly an exclusive adventure any more.

 

[lifeonmercury]

Ensuring that the colonists have an extremely high birth rate on Mars would eliminate the need to find such a large amount of volunteers to go there.

 

[Vanadium 50]

Ensuring that the colonists have an extremely high birth rate on Mars would eliminate the need to find such a large amount of volunteers to go there.

Nonsense. Complete utter abject nonsense. Seriously, you should think more before you post.

The sort of "extremely high birth rates" that you need to get a million people in a century run into the hundreds. Not only do people not have hundreds of children, you couldn't do it in a hundred years anyway.

 

[lifeonmercury]

I didn't specify how big the original colony would be. Sending 200,000 people who plan on having a high birth rate is easier than sending a million.

 

[Vanadium 50]

would eliminate the need to find such a large amount of volunteers to go there.

Sending 200,000 people

You're contradicting yourself.

It's probably a good time to stop digging this hold you are in.

 

[lifeonmercury]

Was just thinking of a potentially better way to get to a million by the end of the century, which apparently is Musk's goal.

 

[Al_]

There are also traces of water in deserts. That doesn't make them swimming pools.

Most deserts have wells, oases, cave pools, even rivers. The Moon is HUGE! It's size, considering the probabilities, makes many things likely. We just need to find those exceptional places.

 

[gleem]

.

"Following the successful test of the launchpad abort system in May 2015, Elon Musk indicated that the Dragon capsule platform, launched on a Falcon Heavy launch vehicle, could be used to transport robotic space probes across much of the solar system, including Earth's Moon, Mars, or Jupiter's moon Europa.[37] Musk indicated that Dragon could transport 2 to 4 tonnes (4,400 to 8,800 lb) of useful payload to the surface of Mars."

from https://en.wikipedia.org/wiki/Dragon_2

The Apollo capsule and lunar lander had a combined mass of 22, 000 Kg. with a crew of three for a 12 day trip. It seems that it is going to take more than rocket science to put an appreciable colony on Mars in even 100 years. I don't think there is an equivalent Moore"s law for rocket propulsion so shear number of rockets will probably be the answer. I don't think Musk has the money to do it himself and as far as sending astrotourist to get a close up picture of Mars is concerned who will give up a year or more of their live to sit in a confined space for that picture. Even a cruise on a submarine is at most 90 days

Much will depend on the success of Musk's Red Dragon project aimed at making a soft landing on Mars with a launch expected in 2018!

Does anyone know if there is a project to see how well humans could live without support for two years in a hermetically sealed structure in a hostile environment on Earth with present day technology? Living on a fixed supply food, water and oxygen and seeing how long it would take to develop a sustaining environment. And what about the social issues that can arise? Can a hundred strangers live compatibly in a relatively confined environment and for how long? Would it be like living on a submarine? I hope not.

 

[PeroK]

OK, so we went from the first controlled powered flight to ten commercial transatlantic flights per day in 44 years. The first manned spaceflight was in 1961, so 44 years after that was 2005. I think a reasonable conclusion is that manned spaceflight is not on the same curve.

And, commerical air travel has also, largely, technologically stagnated. The supersonic commerical aircraft came and went and now we're still at the same speeds of the 1960's.

In 1976 when Concorde was launched I think most people would have expected that 40 years later the flying time from the UK to Australia, say, would be 4-8 hours (at most). Instead, it's still 24 hours, give or take.

And, although construction has developed, we are still using the Forth Rail Bridge (1890) and the Brooklyn Bridge (1883) and London, famously, has largely Victorian sewage and underground railway systems. And, nuclear power has not taken over from conventional coal, oil and gas as once might have been expected.

Instead, it's been communications, IT and certain areas of medical and genetic research that has surged since the 1960's. Generally, in other areas like, say, car manufacture things have got better, cheaper and more reliable. But, the basic specification is not a lot different from 50 years ago.

One argument against the over-optimistic timescale for Mars is that, in fact, our transport, construction and power capabilities have stagnated to a large extent. Future developments may well be in other areas: robotics, medicine and who knows what else.

There is a naive view in many posts on this thread that technological advancements in all areas go on apace. But, actually, if you look a bit more closely, things tend to explode technologically to a plateau (e.g. commercial air services, the motor car) and then stagnate.

Finally, I would suggest the following prerequisites for large-scale construction on Mars:

1) Construction must first become largely robotic, without the need for hundreds or thousands of human construction workers.

2) Lightweight power source, small enough to be shipped to Mars. A laptop-sized power station: that would be something!

3) Powered space flight. It has to be said. Crawling through space at constant speed isn't going to hack it. Without a propulsion mechanism, I just don't see large-scale space exploration.

That's why I think having more than a few hardy scientists on Mars, like an Antarctic base, is beyond the foreseeable future.

 

[mfb]

The first manned spaceflight was in 1961, so 44 years after that was 2005. I think a reasonable conclusion is that manned spaceflight is not on the same curve.

It is not on the same curve if you throw away your rocket after each use (or need months of repairs in case of the Space Shuttle). We would not have commercial transatlantic flights if you would have to throw away the airplane after each flight.

A new curve is starting right now, with the first rocket recovery just a year ago.

Mars will have 999,000 people who have been there for up to fifty years, but it's more isolated and less comfortable than Antarctica.

With 999,000 people, it is not as isolated, and more comfortable than Antarctica.

Does anyone know if there is a project to see how well humans could live without support for two years in a hermetically sealed structure in a hostile environment on Earth with present day technology? Living on a fixed supply food, water and oxygen and seeing how long it would take to develop a sustaining environment. And what about the social issues that can arise? Can a hundred strangers live compatibly in a relatively confined environment and for how long? Would it be like living on a submarine? I hope not.

Biosphere 2 for the isolation in terms of matter, Mars 500 in terms of psychology with a small group and isolation in communication (they artificially added a realistic light-speed delay).
A Mars colony would never be isolated - it can take CO2 from the atmosphere, water from the ground, and other elements in smaller quantities from the environment as well. Making oxygen out of water just requires ~200 W/person. Food is the more interesting part, and reparing/building stuff independently will need a larger colony.

2) Lightweight power source, small enough to be shipped to Mars. A laptop-sized power station: that would be something!

Solar cells produced on Mars. Probably organic solar cells. They have a poor efficiency, but if you can mass-produce them that is fine. You are not really limited in space on Mars.

That's why I think having more than a few hardy scientists on Mars, like an Antarctic base, is beyond the foreseeable future.

Which part exactly do you see as unrealistic in the ITS concept?

 

[Algr]

What is unrealistic is the reason why people would want to go to mars. In the 18th and nineteenth centuries the appeal of Europeans moving to America was that bountiful natural resources made life easier in America then it was in Europe. There was immigration because of the promise of a better life in the new world. In this thread we are working to show that Mars colonists won't all die. The idea that Mars could offer a better life then Earth has not been suggested. Only very unlikely scenarios ever result in Earth being less habitable then mars.

So much of the talk about Mars colonies seems more like reliving past glories rather then looking to the future. Exploring Mars will be nothing like the moon landing or the western frontier.