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suntrack2
2007-Jun-28, 05:41 PM
In other words, how many years will take to start the colonisation on mars, a. very soon, b. in nearest future, c. in hundred years or..

How do you like this idea "the permanent residence on mars" ! will it possible.
or mars is not the proper place for the colonisation?

Noclevername
2007-Jun-28, 05:50 PM
In other words, how many years will take to start the colonisation on mars, a. very soon, b. in nearest future, c. in hundred years or..

How do you like this idea "the permanent residence on mars" ! will it possible.
or mars is not the proper place for the colonisation?

No way to know, as it depends on a number of factors, mainly political, that are basically unpredictable. I certainly think under 100, but I've been disappointed before. The sooner the better, says I, but I can't get those who can afford such things to listen.

I think space habitats built of Near Earth asteroidal material would be a darnsight easier as a first step into space colonization. Once we've established a permanent off-Earth presence, then we can diversify onto Mars & its moons, the Main Belt, and other accessible locations.

NEOWatcher
2007-Jun-28, 06:02 PM
I think space habitats built of Near Earth asteroidal material would be a darnsight easier as a first step into space colonization. Once we've established a permanent off-Earth presence, then we can diversify onto Mars & its moons, the Main Belt, and other accessible locations.
I wouldn't say first step, but a step it is.

I think one of the biggest issues to resolve is self-sufficiency. Even though you may be able to get some raw materials off an asteroid, moon, planet, whatever, you will still have some supplies that must be renewable. Food is a biggie.

Before we venture past a quick rescue jaunt away from Earth, we will need to be able to address a lot of issues that we don't have to worry about now, because we have a supply chain.

Noclevername
2007-Jun-28, 06:30 PM
I wouldn't say first step, but a step it is.

I think one of the biggest issues to resolve is self-sufficiency. Even though you may be able to get some raw materials off an asteroid, moon, planet, whatever, you will still have some supplies that must be renewable. Food is a biggie.

Before we venture past a quick rescue jaunt away from Earth, we will need to be able to address a lot of issues that we don't have to worry about now, because we have a supply chain.


Right, so we find a NEO with low delta-V to reach, ship materials to Earth orbit, and build a prototype hab. Much of the equipment and parts will still need to come directly from Earth at first. But the sooner we start, the more time the infrastructure and long term life-support methods will have to mature before it's actually practical to ship large numbers of people into space.

Saluki
2007-Jun-28, 06:42 PM
Based on the progress we have made in manned space exploration in the last 33 years, I would say we will never colonize Mars.

If the current Mars initiative holds up past the initial return-to-the Moon phase, then maybe there is hope, but I would be very suprised if it happens in my lifetime (I am 39).

I hope I am pleasently suprised someday.

Peter Wilson
2007-Jun-28, 07:11 PM
I'd send microbes first...from the coldest, most aridest place on antartica. Give them some time to tough it out.

If microbes can't survive on Mars, no way humans can.

Noclevername
2007-Jun-28, 07:13 PM
I'd send microbes first...from the coldest, most aridest place on antartica. Give them some time to tough it out.

If microbes can't survive on Mars, no way humans can.

????????

:think:

Microbes can't maintain or repair their own life-support equipment.

NEOWatcher
2007-Jun-28, 07:15 PM
????????

:think:

Ditto...
Is this a confusion between colonization and terraforming?

Moonhead
2007-Jun-28, 08:29 PM
Are 'we' (meaning: mankind, or rather its divisions of scientist, technicians etc.) already actuablly capable to produce oxygen (like harvesting it at off-earth oxygen farms), or do we have to take it with us from earth to colonies in space stations and planetary domes? And what about water?

eburacum45
2007-Jun-28, 08:37 PM
Not sure what an 'off Earth oxygen famr' is, but yes, we should be able to make free oxygen and collect water in abundance in the solar system. There is many times more water in the moons of the various planets than there is on Earth, and water contains oxygen, and so do many other compounds.

What is required to extract these resources is energy- and that might be a little more difficult to come by.

Moonhead
2007-Jun-28, 08:58 PM
Not sure what an 'off Earth oxygen famr' is,

A misspelling of 'off-Earth oxygen farm' :)


but yes, we should be able to make free oxygen and collect water in abundance in the solar system. There is many times more water in the moons of the various planets than there is on Earth,

Wow, I didn't know that (seriously)! Kind of reassuring actually.


and water contains oxygen, and so do many other compounds.

What is required to extract these resources is energy- and that might be a little more difficult to come by.

I see. And how tough is this difficulty, on a scale ranging from 'just around the corner' to "nowhere even near"?

Noclevername
2007-Jun-28, 09:16 PM
A misspelling of 'off-Earth oxygen farm' :)
Wow, I didn't know that (seriously)! Kind of reassuring actually.
I see. And how tough is this difficulty, on a scale ranging from 'just around the corner' to "nowhere even near"?


Space contains abundant energy, in the form of solar radiation. No night, no clouds. In the microgravity of space or the low gravity of most asteroids, it is possible to build large parabolic reflectors to focus and collect sunlight. Photoelectric generators and solar furnaces can be used to break down various compounds known or thought to exist in many asteroids and moons, resulting in a variety of useful materials including oxygen.

The further from the sun, the larger the reflecting/collecting surface needed.

Van Rijn
2007-Jun-28, 09:17 PM
I see. And how tough is this difficulty, on a scale ranging from 'just around the corner' to "nowhere even near"?

It somewhat depends on what you are talking about. It's going to be awhile before we build settlements on Mars, but it may be possible to extract water from the atmosphere (thin as it is) with little energy expenditure:

http://adsabs.harvard.edu/abs/2003AIPC..654.1124S

In the right locations, it should also be possible to extract water from the ground, though this would be more difficult. Oxygen could be produced either from the water, from CO2 or from minerals containing oxygen. A nuclear reactor would probably be the most convenient energy source (you don't have to worry about day/night cycles, summer/winter variations, or dust).

Assuming you want to minimize shipments from Earth, the bigger issue for a Mars settlement is food production.

Noclevername
2007-Jun-28, 09:23 PM
Assuming you want to minimize shipments from Earth, the bigger issue for a Mars settlement is food production.


For any off-Earth colony, or even long-term settlememnt (i.e. more than a couple of years) some kind of self-contained ecology-- plants to produce food and breatheable air --will almost certainly be needed. Research in this area is currently being pursued only sporadically, and on small scales.

Peter Wilson
2007-Jun-28, 09:37 PM
Ditto...
Is this a confusion between colonization and terraforming?
Maybe :neutral:

Earth would be unihabitable to humans without a foundation of microbes.

To build an "outpost" on Mars, you might be able to get away with a few oxygen/water generators, but to "colonize" it?

Let me rephrase it: if we can't get a self-sustaining bacterial colony going on Mars, no way can we establish a human "colony"!!


There's an interesting book on the subject, Man to Mars!, that details the dangers of a manned mission to Mars. By Hugo Phirst ;)

Van Rijn
2007-Jun-28, 09:41 PM
For any off-Earth colony, or even long-term settlememnt (i.e. more than a couple of years) some kind of self-contained ecology-- plants to produce food and breatheable air --will almost certainly be needed. Research in this area is currently being pursued only sporadically, and on small scales.

For a long term stay on Mars with minimal imports, plants would probably be needed to produce food (though there are some things that could be done with fungi, or bacteria that could then be fed to fish or other animals). But it isn't clear that plants would be needed for air, since oxygen could be produced mechanically from available resources, and scrubbers could remove CO2. It really would come down to cost and safety.

Van Rijn
2007-Jun-28, 09:47 PM
Maybe :neutral:

Earth would be unihabitable to humans without a foundation of microbes.

To build an "outpost" on Mars, you might be able to get away with a few oxygen/water generators, but to "colonize" it?


. . . use more oxygen generators, and collect more water.



Let me rephrase it: if we can't get a self-sustaining bacterial colony going on Mars, no way can we establish a human "colony"!!


By "on Mars" do you mean outside or inside a habitat?

Moonhead
2007-Jun-28, 09:54 PM
if we can't get a self-sustaining bacterial colony going on Mars, no way can we establish a human "colony"!!

This might be true in terms of capabilty. But establishing a bacterial colony is not necessarily one level up towards a human settlement. That is only the case if we were also able to "upgrade" the extraterrestrial ecology we're building: start with your bacteria, then more complex lifeforms until we can come over ourselves.

This is a whole new discipline. As far as I know, the biosphere projects (attempts to build a self-sustaining ecology, including humans, separated from the rest of the earth) were not succesful sofar.

Van Rijn
2007-Jun-28, 10:04 PM
This is a whole new discipline. As far as I know, the biosphere projects (attempts to build a self-sustaining ecology, including humans, separated from the rest of the earth) were not succesful sofar.

If you're talking about Biosphere II, that was a mess. And, again, for a Mars habitat, you don't need plants for oxygen. Essentially, a Mars habitat need not have particularly high closure.

JohnBStone
2007-Jun-28, 10:10 PM
In other words, how many years will take to start the colonisation on mars, a. very soon, b. in nearest future, c. in hundred years or..
I'll take c (a hundred years) at the earliest and probably d (longer than that). It requires fundamental technological breakthroughs or a change in the economic fundamentals.

For those that didn't see it, SF author Charles Stross has a sobering analysis of space colonization here
http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.html

Noclevername
2007-Jun-28, 10:12 PM
As far as I know, the biosphere projects (attempts to build a self-sustaining ecology, including humans, separated from the rest of the earth) were not succesful sofar.

There was only one such major project, and it was handled so badly it was a joke. First, they used uncured concrete in the structure, which absorbs gasses as it cures. Their air pressure kept dropping and they didn't know why; eventually they had to let in outside oxygen so that they could keep breathing (not an option in deep space). And the ecosystems were poorly planned and many would up in death spirals or overrun by vermin. And finally, one of the participants had written a book about the benefits of a low-calorie diet. Well, growing your own food entails farm work, which burns up a lot of calories. Result, they did not have enough food, and two years left them almost emaciated.

The main lesson learned from Biosphere II is, if you're going to build a self-sufficient environment, do better prep work, have more backups and plan for the worst.

EDIT: I have heard of a Russian project but I don't know the details.

Moonhead
2007-Jun-28, 10:24 PM
And, again, for a Mars habitat, you don't need plants for oxygen. Essentially, a Mars habitat need not have particularly high closure.

As you also suggested, we'll probably need plants as a food source. For the overall health, I think a 'holistic' environment would offer the best conditions. And them the lower gravity will also be have to be dealt with. (Actually that would be one of the better things of Venus - its gravity is about 90 % of earth's... although the atmospheric pressure might sorta cancel out that benefit. Not to speak of the temperature and toxic atmosphere).

Noclevername
2007-Jun-28, 10:30 PM
As you also suggested, we'll probably need plants as a food source. For the overall health, I think a 'holistic' environment would offer the best conditions. And them the lower gravity will also be have to be dealt with. (Actually that would be one of the better things of Venus - its gravity is about 90 % of earth's... although the atmospheric pressure might sorta cancel out that benefit. Not to speak of the temperature and toxic atmosphere).


One of the things considered for Venus is floating colonies. An air-filled structure would be boyant in Venus' dense atmosphere, and at the right altitude, pressure and temperature wouldn't be a problem. The corrosive component would be the major worry.

Moonhead
2007-Jun-28, 10:31 PM
There was only one such major project, and it was handled so badly it was a joke. [...] The main lesson learned from Biosphere II is, if you're going to build a self-sufficient environment, do better prep work, have more backups and plan for the worst.

I didn't know it was that bad... I was quite enthousiastic about it when I heard it, and it was a disappointment it hadn't worked out. A shame that they didn't do it more properly.

Moonhead
2007-Jun-28, 10:38 PM
One of the things considered for Venus is floating colonies. An air-filled structure would be boyant in Venus' dense atmosphere, and at the right altitude, pressure and temperature wouldn't be a problem. The corrosive component would be the major worry.

Sounds as a cooler option than Mars, which I've always regarded as a luxury edition of the Moon (although I like the 24.5 hour day, giving you half an hour extra to chill in the evening ;) ).

But on the other hand, Mars's low gravity and location might make it a better port to the outer planets, or is this flawed reasoning?

Noclevername
2007-Jun-28, 10:46 PM
Sounds as a cooler option than Mars, which I've always regarded as a luxury edition of the Moon (although I like the 24.5 hour day, giving you half an hour extra to chill in the evening ;) ).

But on the other hand, Mars's low gravity and location might make it a better port to the outer planets, or is this flawed reasoning?

Mars' moons might, as they have less G, no atmoshere and the added luxury of Mars' nearby aerobraking and gravity slingshot potential. Mostly, it'll likely be the Asteroid Belt that'll see the most travellers from Circum-Mars.

Moonhead
2007-Jun-28, 10:52 PM
Mars' moons might, as they have less G, no atmoshere and the added luxury of Mars' nearby aerobraking and gravity slingshot potential.

Good point. I tend to forgot Mars has moons, because they are just large rocks (not spheroidal).



Mostly, it'll likely be the Asteroid Belt that'll see the most travellers from Circum-Mars.

Speaking of which, would Ceres have anything to offer in terms of settlement?

Noclevername
2007-Jun-28, 10:55 PM
Well, let's see:

http://en.wikipedia.org/wiki/Colonization_of_Ceres

From the article:

Observations indicate that it contains large amounts of water ice, about 1/10 of the total water in Earth's oceans. The solar flux of 150 W/m2 (in aphelion), which is nine times smaller than that on Earth, is still high enough for solar power facilities.


Sounds like a keeper.

Noclevername
2007-Jun-29, 12:17 AM
I'll take c (a hundred years) at the earliest and probably d (longer than that). It requires fundamental technological breakthroughs or a change in the economic fundamentals.

No fundamental technology breakthroughs are actually required, just a lot of engineering. And of course, large-scale access to space, with its wealth of resources, would certainly produce a sea change in our economy. All that's really necessary is a change in priorities.

Noclevername
2007-Jun-29, 01:33 AM
Back to the OP, we could start anytime. The present plans to go to Mars are limited to a one-time-only "T-shirt trip" (as in , I Went To Mars And All I Got...). At present, no one is actively trying to colonize Mars, Venus, Ceres, Near-Earth Orbit, or any other off-Earth location. And it can't get done until it gets started.

Ronald Brak
2007-Jun-29, 03:09 AM
At the moment our ability to utilize resources on the moon and mars etc are pretty lousy, but we are gradually improving in this area year by year. Once we get to a point where we can make a machine that can use solar or other energy to take in carbon dioxide from mar's atmosphere, split it and use the carbon to manufacture a variety of materials, then not even the sky is the limit. Such a device could be landed on mars, and set to work expanding its power collecting ability. After that it could start producing the basic materials required for a colony. After a couple of years, if all goes well, the first colonists could arrive and assemble the components waiting for them, as well as bringing a newer and improved version of the carbon processing machine. Just possibly, we could construct such a device within a couple of decades. (Feel free to pillory me for over optimism.)

Noclevername
2007-Jun-29, 03:24 AM
At the moment our ability to utilize resources on the moon and mars etc are pretty lousy, but we are gradually improving in this area year by year. Once we get to a point where we can make a machine that can use solar or other energy to take in carbon dioxide from mar's atmosphere, split it and use the carbon to manufacture a variety of materials, then not even the sky is the limit. Such a device could be landed on mars, and set to work expanding its power collecting ability. After that it could start producing the basic materials required for a colony. After a couple of years, if all goes well, the first colonists could arrive and assemble the components waiting for them, as well as bringing a newer and improved version of the carbon processing machine. Just possibly, we could construct such a device within a couple of decades. (Feel free to pillory me for over optimism.)


Well, if not carbon specifically, then certainly some sort of automated in-situ processing and manufacturing should soon be possible. It's being worked on now, though not in a very systematic way.

Ronald Brak
2007-Jun-29, 03:48 AM
Well, if not carbon specifically, then certainly some sort of automated in-situ processing and manufacturing should soon be possible. It's being worked on now, though not in a systematic way.

I figure carbon because there is so much you can do with it and sucking in air and extracting it sounds easier and than mining the ground and such a device might be lighter and more compact than something that mines. Of course one of its tasks might be to construct the frames of mining equipment which will then have movement and control devices slotted into it. But just mining the atmosphere can extract carbon, oxygen, and nitrogen and you can even extract water vapour for a source of hydrogen. Depending on how you want to do things and your skill with carbon compounds, atmosphere mining could supply most of what a colony needs. Of course other elements would be required in much smaller amounts, but perhaps extracting these from the ground could wait until humans arrive.

Romanus
2007-Jun-29, 03:19 PM
I'm with Saluki, Stross, and Sterling--I don't see it happening, ever. I think the best we can expect for Mars is something like Antarctica today: teams of scientists working in rotations between launch windows.

If it does happen, I don't think it's likely before 2050.

Ronald Brak
2007-Jun-29, 04:02 PM
It's very hard to know what people in the future will do. A hundred or so years ago there were people who got a thrill out of killing the last members of a species and making them extinct. In the thirties there were plenty of people who thought that paving over every bit of wilderness and gaining "victory" over nature was a good idea. Unless we screw up real bad, I'm pretty sure that before too many decades have passed we'll have the technology to colonize mars or another body at a fairly low cost. I imagine at that point there will be some people nuts enough to try it, but I suppose I could be wrong.

Noclevername
2007-Jun-29, 04:29 PM
I'm with Saluki, Stross, and Sterling--I don't see it happening, ever. I think the best we can expect for Mars is something like Antarctica today: teams of scientists working in rotations between launch windows.


There's too many people who have their hearts set on establishing a colony on Mars for them to give up their dream so easily, IMO.

ADDED: Not many have ever actually lobbied for establishing a permanent society on Antarctica.

Noclevername
2007-Jun-29, 05:20 PM
Of course other elements would be required in much smaller amounts, but perhaps extracting these from the ground could wait until humans arrive.


With all that wind-blown dust, it shouldn't be hard to gather other elements.

jaba
2007-Jun-30, 04:31 PM
What about the lack of a magnetosphere? How would we deal with the radiation?

antoniseb
2007-Jun-30, 04:57 PM
What about the lack of a magnetosphere? How would we deal with the radiation?

Live mostly underground.

Noclevername
2007-Jun-30, 08:15 PM
What about the lack of a magnetosphere? How would we deal with the radiation?

The same as any deep-space colony would, just pile on enough shielding material.

m1omg
2007-Jul-01, 10:13 AM
I'd send microbes first...from the coldest, most aridest place on antartica. Give them some time to tough it out.

If microbes can't survive on Mars, no way humans can.

I guess there are already some....
wiki;

"Viking experiments
Main article: Viking biological experiments

The primary mission of the Viking probes of the mid-1970s was to carry out experiments designed to detect microorganisms in Martian soil. The big difficulty of this mission was that NASA's knowledge about conditions on Mars's surface was limited to the data returned by Mariner 4, and so the tests were formulated to look for life similar to the life found on Earth. Nevertheless, of the four experiments carried out, the labeled release experiment returned a positive result showing increased CO2 production on exposure to water and nutrients. However this sign of life was disputed by many scientists, who argued that superoxidant chemicals in the soil could have produced this effect without life being present. To counter this it has been argued that the labeled release experiment detected that there were so few metabolising organisms in the martian soil that it would have been impossible for the gas chromatograph to detect them. This view is put forward by one of the designers of the LR experiment, Gilbert Levin, who believes the results of the Viking landers are diagnostic for life on Mars[1].

A re-analysis of the now 30 year old Viking data in the light of modern knowledge of extremophile forms of life has suggested that the Viking tests were not sophisticated enough to detect these forms of life, and may even have killed it in the testing procedure[2]. The central idea here is that instead of being destroyed by Mars' high levels of hydrogen peroxide and other oxidants, life on Mars may use these chemicals to help them survive. For example hydrogen peroxide would stop water in a cell from freezing down to -50C and is hygroscopic, a useful trait on such a dry planet. The researchers cite Acetobacter peroxidans as a known example of a microbe that uses hydrogen peroxide in its metabolism.

There are some that now argue that, if there was life at the Viking lander sites, it may have been killed by the exhaust from the landing rockets.[3]"

m1omg
2007-Jul-01, 10:14 AM
The same as any deep-space colony would, just pile on enough shielding material.

And if we will terraform Mars, the atmosphere will do it.

m1omg
2007-Jul-01, 10:15 AM
I wouldn't say first step, but a step it is.

I think one of the biggest issues to resolve is self-sufficiency. Even though you may be able to get some raw materials off an asteroid, moon, planet, whatever, you will still have some supplies that must be renewable. Food is a biggie.

Before we venture past a quick rescue jaunt away from Earth, we will need to be able to address a lot of issues that we don't have to worry about now, because we have a supply chain.

LOL Food?
You can grow your own in a greenhouse.
Stop being too pseudsceptic.

m1omg
2007-Jul-01, 10:20 AM
A misspelling of 'off-Earth oxygen farm' :)



Wow, I didn't know that (seriously)! Kind of reassuring actually.



I see. And how tough is this difficulty, on a scale ranging from 'just around the corner' to "nowhere even near"?

Solar energy is a source on Mars.
If you want something more powerful, mine some uranium on Mars and create your own little Chernobyl ;) .
And water is present relatively abudantly on Mars in form of ice and some vapor, maybe even some underground lakes; see http://en.wikipedia.org/wiki/Mars#Hydrology

Noclevername
2007-Jul-01, 10:21 AM
LOL Food?
You can grow your own in a greenhouse.
Stop being too pseudsceptic.


As Biosphere II showed, creating a viable self-sustaining, isolated long-term biosystem is more complicated than just growing a few plants. On Earth, a greenhouse is still connected to the atmosphere and outside sources of water and fertilizer. It need not be in balance.

"In space, no one can hear you weed..."

neilzero
2007-Jul-01, 01:32 PM
We will start colonizing Mars about the same time we complete the first space elevator, put the first gigawatt, on the electricity grid from fusion or solar power satellites, replace the first billion private cars with flying cars. When depends a lot in how much money we put up in this decade and how skilfuly we use that money. Neil

JohnBStone
2007-Jul-02, 12:11 PM
There's too many people who have their hearts set on establishing a colony on Mars for them to give up their dream so easily, IMO.
As Stross points out the space colonization meme has strong religious parallels, it is more faith or the dream rather than anything technological or economic that is driving it. One that I share to an extent.


ADDED: Not many have ever actually lobbied for establishing a permanent society on Antarctica.
And (channeling Stross again) it is a hugely easier to establish a permanent base there or in the middle of a Desert than on Mars.

The journey and struggle to reach Mars inspire more than I imagine the day to day reality of living there would. I wonder if the children of the first Moon/Mars colonists will think their parents insane? (You left Earth for _this_?)

RalofTyr
2007-Jul-02, 07:39 PM
The future colonists of Mars will probably be highly educated, a mix of nationalities working for a common goal and probably genetically engineered a bit.

Nationalism will come to represent scientific progress and become one and the same.

Society will become communal with everyone knowing their job function. Anyone that doesn't serve the purpose of the colony, will be removed. There will be zero tolerance for mistakes and mismanagement. One mistake could get someone killed on Mars.

Once living space is throroughly established, applicants from Earth will be accepted. Only the best and the most useful will be accepted. Race means nothing.

Noclevername
2007-Jul-02, 08:16 PM
The future colonists of Mars will probably be highly educated, a mix of nationalities working for a common goal and probably genetically engineered a bit.

Nationalism will come to represent scientific progress and become one and the same.

Society will become communal with everyone knowing their job function. Anyone that doesn't serve the purpose of the colony, will be removed. There will be zero tolerance for mistakes and mismanagement. One mistake could get someone killed on Mars.

Once living space is throroughly established, applicants from Earth will be accepted. Only the best and the most useful will be accepted. Race means nothing.

This seems like an overly optimistic scenario. Colonization of Mars could also occur in a variety of other ways.

edward2007
2007-Jul-05, 11:56 AM
In other words, how many years will take to start the colonisation on mars, a. very soon, b. in nearest future, c. in hundred years or..

How do you like this idea "the permanent residence on mars" ! will it possible.
or mars is not the proper place for the colonisation?

Here's a site where I'm a member too, you might find some answers there:

http://marsdrive.com/

No, it's not a hoax, these guys are very serious.

Edward.

GOURDHEAD
2007-Jul-05, 01:21 PM
I'll take c (a hundred years) at the earliest and probably d (longer than that). It requires fundamental technological breakthroughs or a change in the economic fundamentals.

For those that didn't see it, SF author Charles Stross has a sobering analysis of space colonization here
http://www.antipope.org/charlie/blog-static/2007/06/the_high_frontier_redux.htmlStross' points are well taken; however, http://www.redcolony.com/wiki/index.php?title=Portal:Gourdheadian_Approach is a system that could be started within a year or so. It'll take 3 or 4 hundred years to complete the infrastructure sufficently to colonize Mars "the right way". With the infrastructure complete, 40 years one way to the Alpha Centauri system will be a piece of cake---assuming there are no sentients there or they don't object.

The harnessing of stellar energy as indicated in the link using a similar infrastructure is far superior to either fission or fusion power systems for interstellar travel until we master fusion technology to use ordinary hydrogen as a fusion fuel. Even then the mass required to make the process safe to operate at the required energy levels (10^18 to 10^20 watts) may make the process unwieldy.

We are not likely to be able to carry sufficient propellant material and capturing propellant material by a vehicle traveling at several tenths the speed of light without destroying the vehicle is a formidable challenge. Anyone know how to compute the energy penalty required assuming the propellant material has been "laid down" ahead of the vehicle at optimum precapture velocities for each section of the vehicle's path? The vehicle propellant exhaust traveling at 0.5 to 0.9 light speed, by or through which the propellant supply beam particles must pass, won't lessen the challenge. If the particle beam is laid down too far in advance, natural divergence will rob the vehicle of needed propellant material.

But these are the kinds of problems that make life worth the living!!!