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Thread: Mars Colony: Soylent Green?

  1. #101  
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    Quote Originally Posted by moonguy View Post
    Actually, the outlook is not so gloomy for martian agriculture. The hydroponic solutions you buy at the local nursery are solutions of combined dry salts and water. One metric ton of the dry salts would go a long way to maintaining production through several crop cycles. Mars has a serious overabundance of all macro-nutrients in it's soil. Way beyond what would be healthy for food plants. The soil will need to be processed and enriched before it can be used. There are also serious toxins such as chlorates and even hydrogen peroxide. I recommend going with the hydroponics while developing enclosed growth chambers based on 'standard' soil methods of growing.
    Welcome to the forum moonguy.

    Growing food on Mars needs to plan for the worse case scenario. For instance if they were dependent on acres of solar panels, what happens when they have a global dust storm that last for months or even over a year? They will need a guaranteed minimum power output that is modular so that it can be expanded as the population increases without breaking the bank. At the moment the development of small micro reactors is the best solution. Next, solution is to develop low power grow lighting. I haven't heard of LED grow lights yet. But I sure don't see why they can't be produced.
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    The operative words in the title of this thread were 'Soylent Green'. In the movie, people were deceived into believing the Soylent Green was a mass-produced vegetable product. They did not know it contained the remains of dead people. This is very different from a scenario where people are being told, up front, that this is what is being done. My guess is Mars colonists would prefer a faster way to make food than composting anything. Algae-based growths with high protein and carbohydrate content can be used to make foods that resemble meats well enough to be palatable. And you don't have to worry about maybe finding some deceased loved one's gold filling in your algae-burger,
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    Quote Originally Posted by Bad Robot View Post
    Quote Originally Posted by moonguy View Post
    Actually, the outlook is not so gloomy for martian agriculture. The hydroponic solutions you buy at the local nursery are solutions of combined dry salts and water. One metric ton of the dry salts would go a long way to maintaining production through several crop cycles. Mars has a serious overabundance of all macro-nutrients in it's soil. Way beyond what would be healthy for food plants. The soil will need to be processed and enriched before it can be used. There are also serious toxins such as chlorates and even hydrogen peroxide. I recommend going with the hydroponics while developing enclosed growth chambers based on 'standard' soil methods of growing.
    Welcome to the forum moonguy.

    Growing food on Mars needs to plan for the worse case scenario. For instance if they were dependent on acres of solar panels, what happens when they have a global dust storm that last for months or even over a year? They will need a guaranteed minimum power output that is modular so that it can be expanded as the population increases without breaking the bank. At the moment the development of small micro reactors is the best solution. Next, solution is to develop low power grow lighting. I haven't heard of LED grow lights yet. But I sure don't see why they can't be produced.
    Thanks for the welcome, Bad Robot! There are LED growing lights on the commercial market. I do some hydro in my home and the LED's really dropped my electric bill quite a bit. Mars' surface gets the same level of solar flux as Earth's surface due to the extreme thinness of Mars' atmosphere. Unfortunately, food plants are only slightly more tolerant of particle radiation than humans. They will need to be protected by shielding and Mars' regolith is the best solution near term. Powering the agricultural set-up can be done with solar-driven LED's at a 'reasonable' import cost if reflector/concentrators are used instead of additional PVA. Mylar or MLI coated to 85% or better reflectivity is much lighter than even high efficiency PVA. 250 watts/m2 yield per PVA would not be very difficult to achieve with refcons. Other activities such as mining or mineral processing are VERY energy intensive. My solution for that is, well, controversial. I haven't made any enemies here (yet) but if you REALLY want to know, just message me. . . Again, thanks!
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    Quote Originally Posted by moonguy View Post
    Powering the agricultural set-up can be done with solar-driven LED's at a 'reasonable' import cost if reflector/concentrators are used instead of additional PVA.
    I just don't get the idea that using the path sun -> concentrator -> PV cell -> wiring -> switching/conversion -> lamps -> plants is easier or simpler than sun -> window -> plants. The first path varies between 1% and 5% efficient; the second path is ~80% efficient. The first path requires some very high tech (expensive/heavy) equipment; the second path requires glass or plastic. The first requires gearing and tracking equipment, problematic in cold/dusty environments. The second does not require gearing and can be cleaned with a broom.

    There are many cases where high tech doesn't help, and may hurt. When your life depends on a series of expensive and fairly delicate components, simpler is generally better.
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    Quote Originally Posted by moonguy View Post
    Quote Originally Posted by Bad Robot View Post
    Quote Originally Posted by moonguy View Post
    Actually, the outlook is not so gloomy for martian agriculture. The hydroponic solutions you buy at the local nursery are solutions of combined dry salts and water. One metric ton of the dry salts would go a long way to maintaining production through several crop cycles. Mars has a serious overabundance of all macro-nutrients in it's soil. Way beyond what would be healthy for food plants. The soil will need to be processed and enriched before it can be used. There are also serious toxins such as chlorates and even hydrogen peroxide. I recommend going with the hydroponics while developing enclosed growth chambers based on 'standard' soil methods of growing.
    Welcome to the forum moonguy.

    Growing food on Mars needs to plan for the worse case scenario. For instance if they were dependent on acres of solar panels, what happens when they have a global dust storm that last for months or even over a year? They will need a guaranteed minimum power output that is modular so that it can be expanded as the population increases without breaking the bank. At the moment the development of small micro reactors is the best solution. Next, solution is to develop low power grow lighting. I haven't heard of LED grow lights yet. But I sure don't see why they can't be produced.
    Thanks for the welcome, Bad Robot! There are LED growing lights on the commercial market. I do some hydro in my home and the LED's really dropped my electric bill quite a bit. Mars' surface gets the same level of solar flux as Earth's surface due to the extreme thinness of Mars' atmosphere. Unfortunately, food plants are only slightly more tolerant of particle radiation than humans. They will need to be protected by shielding and Mars' regolith is the best solution near term. Powering the agricultural set-up can be done with solar-driven LED's at a 'reasonable' import cost if reflector/concentrators are used instead of additional PVA. Mylar or MLI coated to 85% or better reflectivity is much lighter than even high efficiency PVA. 250 watts/m2 yield per PVA would not be very difficult to achieve with refcons. Other activities such as mining or mineral processing are VERY energy intensive. My solution for that is, well, controversial. I haven't made any enemies here (yet) but if you REALLY want to know, just message me. . . Again, thanks!
    I like new ideas as long as you can show how, why and how much. Are other researchers and scientists working on these ideas and do you have supporting links? So far I've liked what you've said and I've also known many people that have been banned from 2 or 3 other forums, because they wanted to push their agenda more than they wanted to become a part of the forums community. I've found that if you take the time to get to know some of the people they will cut you more slack when you screw up a bit.
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    My solution to the high-power drain operations (mining, mineral processing, fabrication) is to relieve Mars form the task altogether and have that done on Mercury. Nuts? Consider: Mercury has 20 times the solar flux with which to mine and process minerals. Mercury has a 101-day synodic launch window with Mars. This means Mercury has seven times as many launch opportunities with Mars as Earth does. Mercury, using solar sails, can deliver any number of cargoes to Mars at each opportunity - three times per calendar year* - and each cargo can be 100 metric tons. This means Mars Base grows at the rate of 300 tons a year. But wait. . .there's more. By relieving Earth of the need to deliver 90-95% of Mars Colony's mass, they can redirect their launch program to sending more people and/or more productivity enhancers years before it would be otherwise possible. This drastically reduces the time involved in bringing Mars Colony to completion. Every year chopped off the schedule reduces the project's overall cost by five billion dollars. Deferring the 'essential' nuclear power systems also eliminates their development and deployment costs. If the heavy stuff is done on Mercury - where it is easier and cheaper to do - enables the Mars colony to expand its operations on solar power. Eventually, Mercury delivers solar powersats to Mars where multi-Gigawatt power levels could be provided. As I said, my ideas about this are controversial. There are other ways for using Mercury, but that is a subject for another thread. . . *Payloads sent to Mars from Mercury using solar sails may take a year or more to arrive, but they are common materials that would be more or less the same for each cargo unit. Beams, panels, rolled sheet stock etc. A new shipment would arrive every 100 days or so. Who would care how long it took to arrive?
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    Saw a recent comment on Sciencedaily to the effect that Mars is rich in phosphorus. That, along with nitrogen and potassium are what is mostly needed for hydroponics.
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    Quote Originally Posted by moonguy View Post
    My solution to the high-power drain operations . . . .
    All are feasible, but none are practical for any near term Mars colony.

    Every year chopped off the schedule reduces the project's overall cost by five billion dollars.
    Perhaps - but cutting costs by five billion dollars by implementing a many-trillion-dollar Mercury mining program is not a savings.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by moonguy View Post
    My solution to the high-power drain operations . . . .
    All are feasible, but none are practical for any near term Mars colony.

    Every year chopped off the schedule reduces the project's overall cost by five billion dollars.
    Perhaps - but cutting costs by five billion dollars by implementing a many-trillion-dollar Mercury mining program is not a savings.
    That was $5 billion for every year chopped off the development program. Total savings could be $25-30 billion. And where did you get that 'many-trillion-dollar' idea for a Mercury mining program? Transportation costs to Mercury are lower for cargo missions than for Mars. Crewed missions are also lower - hard to believe, I know - and Mercury does some other things that off-set the Mercury operation's costs. Mars' big problem in this context is the ~780-day launch window cycle. All of the mass going to Mars has to be launched within a ~40 days and we only have two launch pads for a heavy lifter to work with. This explains why so many at NASA are keen to establish an unneeded propellant depot at L1. That alone is a $50 - 100 billion dollar project. The L1 station is not needed to explore the Moon. It is not any improvement for interplanetary missions. It is there to support Mars operations. It is not even needed to support Mercury operations. We should talk before you try to dismiss this idea with a sentence or two. There is much to be shared!!
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    Quote Originally Posted by moonguy View Post
    That was $5 billion for every year chopped off the development program. Total savings could be $25-30 billion.
    Right. Now compare that to the trillions it would take to start a Mercury mining program.

    And where did you get that 'many-trillion-dollar' idea for a Mercury mining program?
    Development of:
    1) hardware that will work on Mercury
    2) a vehicle that can launch from Earth, land on Mercury, autonomously mine and refine a lot of ore, then relaunch, deploy a solar sail, fly to Mars and do a soft re-entry/landing is a decades-long, trillion dollar endeavor. And that's just for one. If you want to build a fleet - or even a whole system of reusable launchers, ferry vehicles etc - it's going to be a lot more.

    Transportation costs to Mercury are lower for cargo missions than for Mars.
    They are actually higher. Delta V requirements are higher to begin with. Plus Mercury has no atmosphere so you have to do a 100% powered descent. That means your delta-V requirements are a lot higher - and thus your launch weight is a lot more.
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    One of the things that always amazes me is that most people overlook the Phobos option as a stepping stone. Since landing on Phobos is akin to a docking manoeuvre, rather than a landing through gravity, it is actually cheaper to get people to Phobos than to land them on the moon. A preliminary step before a Mars colony should be to establish a station on Phobos. A special Mars lander vehicle could then be situated at Phobos, and fuel ferried from Earth, or even synthesized on Mars.

    It also seems to me to be sensible to have a specialised interplanetary vehicle. I would look at a space going trimaran. Three hulls, with the two outer hulls rotating round the central one. The central hull would contain the ion drive engines and fuel, plus the control room. The outer hulls would be living quarters, with gravity from the rotation.

    An Earth based shuttle type craft would make up the three needed craft. The Earth based launcher meets the interplanetary craft in orbit, and transfers people, stores and fuel. The interplanetary craft uses its ion drive engines to slowly accelerate to a course taking it to Phobos. From Phobos, the Mars lander is used.

    The interplanetary craft could, of course, be used for other purposes, such as asteroids etc.
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    Quote Originally Posted by moonguy View Post
    Quote Originally Posted by billvon View Post
    Quote Originally Posted by moonguy View Post
    My solution to the high-power drain operations . . . .
    All are feasible, but none are practical for any near term Mars colony.

    Every year chopped off the schedule reduces the project's overall cost by five billion dollars.
    Perhaps - but cutting costs by five billion dollars by implementing a many-trillion-dollar Mercury mining program is not a savings.
    That was $5 billion for every year chopped off the development program. Total savings could be $25-30 billion. And where did you get that 'many-trillion-dollar' idea for a Mercury mining program? Transportation costs to Mercury are lower for cargo missions than for Mars. Crewed missions are also lower - hard to believe, I know - and Mercury does some other things that off-set the Mercury operation's costs. Mars' big problem in this context is the ~780-day launch window cycle. All of the mass going to Mars has to be launched within a ~40 days and we only have two launch pads for a heavy lifter to work with. This explains why so many at NASA are keen to establish an unneeded propellant depot at L1. That alone is a $50 - 100 billion dollar project. The L1 station is not needed to explore the Moon. It is not any improvement for interplanetary missions. It is there to support Mars operations. It is not even needed to support Mercury operations. We should talk before you try to dismiss this idea with a sentence or two. There is much to be shared!!
    You make it sound like getting to and landing on Mercury is an easy thing to do. Mercury has a tight fast orbit. We have to be able to accelerate the space craft to a very high speed catch up to Mercury and then slow down enough to move into orbit around Mercury and then we can land the planet. We were barely able to put the messenger space craft in orbit around Mercury. In any event it seems to me that asteroid mining would be easier, cheaper and something private companies will be doing anyway.
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    Quote Originally Posted by skeptic View Post
    One of the things that always amazes me is that most people overlook the Phobos option as a stepping stone. Since landing on Phobos is akin to a docking manoeuvre, rather than a landing through gravity, it is actually cheaper to get people to Phobos than to land them on the moon. A preliminary step before a Mars colony should be to establish a station on Phobos. A special Mars lander vehicle could then be situated at Phobos, and fuel ferried from Earth, or even synthesized on Mars.

    It also seems to me to be sensible to have a specialised interplanetary vehicle. I would look at a space going trimaran. Three hulls, with the two outer hulls rotating round the central one. The central hull would contain the ion drive engines and fuel, plus the control room. The outer hulls would be living quarters, with gravity from the rotation.

    An Earth based shuttle type craft would make up the three needed craft. The Earth based launcher meets the interplanetary craft in orbit, and transfers people, stores and fuel. The interplanetary craft uses its ion drive engines to slowly accelerate to a course taking it to Phobos. From Phobos, the Mars lander is used.

    The interplanetary craft could, of course, be used for other purposes, such as asteroids etc.
    It will already take 5-6 months to get to mars. This would likely make it a generation ship.
    You could put a nuclear or plasma engine would work better (or fusion if we get it working in time), though at higher cost. Phobos would make a good place for a refinery for asteroid ores (if they aren't refined at the mine or on the ship) or a trade/shipping station for mars. You could also use it as a base to mine Deimos.
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    Unknowable

    The time taken to get to Mars is well known, but that does not make it a generation ship. A generation ship is a vessel for interstellar travel, where the time taken may exceed one human lifetime.
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    Quote Originally Posted by skeptic View Post
    Unknowable

    The time taken to get to Mars is well known, but that does not make it a generation ship. A generation ship is a vessel for interstellar travel, where the time taken may exceed one human lifetime.
    Any ship that requires it crew to have children to provide further crew is a generation ship, regardless of how far it goes. With an ion drive it would take far longer, possibly years, to get there. I was probably exaggerating about the generation thing (only space stations and colonies will likely have those) but still, you want the people to get there as fast as possible to prevent all kinds of problems. The rotation will prevent the gravity related ones, but there will be problems with boredom (and also laziness), atrophied (or over practiced, say from doing too many simulations) skills, ever depleting resources (even worse than a planet or moon where some things can come from the environment). This makes keeping people on a ship for too long a bad idea. Even months could be bad.
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    The ion drive is a very efficient means to get a large logistic ship to Mars--these will probably be unmanned and take a couple years.

    The manned ships we'd want to be as fast as possible to minimize radiation exposure.

    And I think Zubrin's ideas, though focused in a very small manned missions are would work just as well for setting up a colony. Get the stuff there or build it in place including redundant systems with little to no people before the colonist show up.

    Wanted to comment a bit on the Mars dust storms. Opportunity rover probably went through the worst of these and experienced a drop from about 700 watts per square meter (aphelion) to lows near 150 watts square meter for about a week. The storm lasted several months but solar gain wasn't as effects as during the worst parts--the dust scatters quite a bit of the light except during the worst of it. Like anything else in engineering you build in a safety margin or reserve or excess solar collection (say 3x) to survive a month at near the lowest levels to survive.
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    On ion drives.

    These should get people to Mars a lot more quickly than traditional rockets. They have very little acceleration, but they will accelerate at their slow pace over weeks, whereas a rocket may be in blast for mere minutes. Maximum velocity should be much greater with ion drive, and hence the journey time much less. There are some pundits who believe an ion drive vessel might make the Earth to Mars trip in 6 weeks, versus six months for a more traditional craft. And use less fuel!

    The only other drive systems that can compete with ion drive for maximum velocity are nuclear. Like the Orion system, where A-bombs are exploded against the rear of the ship. Acceleration and final velocity are substantial. However, there are numerous technical problems with this idea. Fusion drives might, in theory, be better, but they are still a long, long way off being possible.
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by moonguy View Post
    That was $5 billion for every year chopped off the development program. Total savings could be $25-30 billion.
    Right. Now compare that to the trillions it would take to start a Mercury mining program.

    And where did you get that 'many-trillion-dollar' idea for a Mercury mining program?
    Development of:
    1) hardware that will work on Mercury
    2) a vehicle that can launch from Earth, land on Mercury, autonomously mine and refine a lot of ore, then relaunch, deploy a solar sail, fly to Mars and do a soft re-entry/landing is a decades-long, trillion dollar endeavor. And that's just for one. If you want to build a fleet - or even a whole system of reusable launchers, ferry vehicles etc - it's going to be a lot more.

    Transportation costs to Mercury are lower for cargo missions than for Mars.
    They are actually higher. Delta V requirements are higher to begin with. Plus Mercury has no atmosphere so you have to do a 100% powered descent. That means your delta-V requirements are a lot higher - and thus your launch weight is a lot more.
    Transportation costs for crewed missions is determined by a number of factors, delta-V being just one of them. For a given payload mass, delta-V to Mercury is two to three times that for a flight to Mars. For the Mercury mission, however, the crew module payload is only 45% the mass of the Mars-bound equivalent. This is due mostly to the much shorter flight time (~440 days typically for mound trip with 178 day stay-over) compared to Mars (~900+ days with 540 day stay-over); The size and mass of the vehicle's power system is also much smaller than for Mars because the entire mission is spent well inside 1AU; The crew vehicle in the Mercury mission is built entirely of non-metallic composites. this reduces radiation issues and reduces structure weight to about half that for Apollo/Shuttle-era designs. I could say more, but you get the idea. All totaled, propellant mass for an actual Mercury mission, assuming same number of crew members, would be about 1.2 to 1.5 times the Mars mission. Total flight costs, however, are less because the mission requires no on-orbit infrastructure and only one proximity operation - docking the Mercury Stage with a departure stage. Mars missions of the Mars Direct variety require two consecutive launch windows for a single mission, in effect stretching mission duration to 1600 days. It is necessary to think in terms of 'missions', not just 'flights'. The difference is subtle, but important.
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    The crew vehicle in the Mercury mission is built entirely of non-metallic composites. this reduces radiation issues and reduces structure weight to about half that for Apollo/Shuttle-era designs.
    ?? Same technology can be used in both cases. You need a little more shielding on the Mercury mission (higher risk during solar activity) but otherwise you can use composites, metals, plastics etc on either mission,

    Quote Originally Posted by moonguy View Post
    All totaled, propellant mass for an actual Mercury mission, assuming same number of crew members, would be about 1.2 to 1.5 times the Mars mission.
    Sounds about right. However, this is for a flight to and from Mars orbit vs. to and from Mercury orbit. Actually landing and taking off again is going to put the Mercury mission at a huge disadvantage, since Mercury does not have the in situ fuel resources that Mars does.

    Total flight costs, however, are less because the mission requires no on-orbit infrastructure and only one proximity operation - docking the Mercury Stage with a departure stage.
    Right, and Mars Direct requires no on-orbit infrastructure and no on-orbit proximity operations. One launch to get the return vehicle there, one launch to send the crew.

    Mars missions of the Mars Direct variety require two consecutive launch windows for a single mission, in effect stretching mission duration to 1600 days. It is necessary to think in terms of 'missions', not just 'flights'. The difference is subtle, but important.
    In general several smaller launches are a lot cheaper/easier than one big launch. (Compare a Saturn V launch to a Delta IV heavy launch, and eventually to a Falcon heavy launch.)
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    Quote Originally Posted by billvon View Post
    The crew vehicle in the Mercury mission is built entirely of non-metallic composites. this reduces radiation issues and reduces structure weight to about half that for Apollo/Shuttle-era designs.
    ?? Same technology can be used in both cases. You need a little more shielding on the Mercury mission (higher risk during solar activity) but otherwise you can use composites, metals, plastics etc on either mission,

    Quote Originally Posted by moonguy View Post
    All totaled, propellant mass for an actual Mercury mission, assuming same number of crew members, would be about 1.2 to 1.5 times the Mars mission.
    Sounds about right. However, this is for a flight to and from Mars orbit vs. to and from Mercury orbit. Actually landing and taking off again is going to put the Mercury mission at a huge disadvantage, since Mercury does not have the in situ fuel resources that Mars does.

    Total flight costs, however, are less because the mission requires no on-orbit infrastructure and only one proximity operation - docking the Mercury Stage with a departure stage.
    Right, and Mars Direct requires no on-orbit infrastructure and no on-orbit proximity operations. One launch to get the return vehicle there, one launch to send the crew.

    Mars missions of the Mars Direct variety require two consecutive launch windows for a single mission, in effect stretching mission duration to 1600 days. It is necessary to think in terms of 'missions', not just 'flights'. The difference is subtle, but important.
    In general several smaller launches are a lot cheaper/easier than one big launch. (Compare a Saturn V launch to a Delta IV heavy launch, and eventually to a Falcon heavy launch.)
    The Mars crew module would still have to be larger and heavier even if it is made of the same composites as the Mercury module. It has to take more than twice the food, air and water as the Mercury mission and its power system would have to be larger - though I assume here it would be solar and not nuclear. That would change matters, but then the Mercury craft could be nuclear too. . . The presence of billions of tons of water and hydrocarbons has been confirmed by the MESSENGER mission. So Mercury does have the resources for propellant production - and the energy, which Mars is lacking. Delta-V for landing and lifting off of Mars and Mercury. For Mercury, it is about 3100 km/sec. This is about 50% more than for landing on the Moon. In the Mars case, using its atmosphere to land effectively cuts your landing propellant requirement. The problem is you have to have a heat shield and structure to protect your payload. And you need both to lift-off again, even though they represent lost cargo capacity and dead-load. As for 'several smaller launches' being cheaper than one large launch, Mars direct was predicated on a version of the Ares V that pre-dated the Constellation program, but had the same payload capacity, more or less. At least the Mars Direct case had the Ares V man-rated. . . To summarize, we can get to Mercury using equipment NASA is already planning to build. It would be better to have a Solar Thermal Rocket or even VASIMIR, but we do not need to wait for them to get started. I will start a new thread where I hope to lay out WHY we should go to settle Mercury. . . I hope to see you there!
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    Quote Originally Posted by skeptic View Post
    On energy.
    Any Mars colony will need lots of energy to succeed. It will need to roast rock to get water. To compress atmosphere for CO2. To use electric arc furnaces to get minerals from Mars dust. Electrolysis. Heat. Lighting. etc. etc.

    Solar cells will be weak at Mars surface, and probably impractical with such an enormous demand. Solar cells in orbit would be better, but there are many control difficulties there. Nuclear power, though, carried the energy density required in a relatively small space. The reference to the Toshiba reactor is good. However, it is not the only microreactor under development. The travelling wave reactor, due out in 2020, will also be tiny, and innately 'safe'. The TWR has the advantage that it runs on uranium 238, which is probably accessible on Mars, without the enormous level of technology required to process uranium 235 for other reactors.. It is worth noting that the entire Cassini misson to Saturn is run off a small nuclear reactor, which is way less efficient than the two more modern ones mentioned above.

    In establishing a largely self sufficient Mars colony, a nuclear reactor will almost certainly be one of the first things delivered.
    Roast rocks to make water? Is there something wrong with the ice at the poles?
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    Quote Originally Posted by skeptic View Post
    On ion drives.

    These should get people to Mars a lot more quickly than traditional rockets. They have very little acceleration, but they will accelerate at their slow pace over weeks, whereas a rocket may be in blast for mere minutes. Maximum velocity should be much greater with ion drive, and hence the journey time much less. There are some pundits who believe an ion drive vessel might make the Earth to Mars trip in 6 weeks, versus six months for a more traditional craft. And use less fuel!

    The only other drive systems that can compete with ion drive for maximum velocity are nuclear. Like the Orion system, where A-bombs are exploded against the rear of the ship. Acceleration and final velocity are substantial. However, there are numerous technical problems with this idea. Fusion drives might, in theory, be better, but they are still a long, long way off being possible.
    This still looks very good to me (post#22)
    The 123,000 MPH Plasma Engine That Could Finally Take Astronauts To Mars
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  23. #123  
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    Quote Originally Posted by moonguy View Post
    The Mars crew module would still have to be larger and heavier even if it is made of the same composites as the Mercury module. It has to take more than twice the food, air and water as the Mercury mission and its power system would have to be larger
    Food - agreed. Air and water can be recycled. (A cool byproduct of this is methane, which can be used as fuel or just vented.)

    The presence of billions of tons of water and hydrocarbons has been confirmed by the MESSENGER mission. So Mercury does have the resources for propellant production - and the energy, which Mars is lacking.
    Mercury has no atmosphere, thus there is no easy way to access those water and hydrocarbons. Sure, you can envision a robotic mining/extraction/refining facility but again we are decades away from that. On Mars all you need to do is open a valve and let the atmosphere in.

    Delta-V for landing and lifting off of Mars and Mercury. For Mercury, it is about 3100 km/sec. This is about 50% more than for landing on the Moon. In the Mars case, using its atmosphere to land effectively cuts your landing propellant requirement. The problem is you have to have a heat shield and structure to protect your payload. And you need both to lift-off again, even though they represent lost cargo capacity and dead-load.
    Yes, but again, using Martian atmosphere for fuel greatly reduces the fuel that has to be transported there.

    To summarize, we can get to Mercury using equipment NASA is already planning to build.
    True of both efforts. Mars missions have a lot of planning behind them.
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  24. #124  
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    Moonguy

    Compared to Mercury, it is even easier to land on Phobos or an asteroid. You do not need much fuel for that. If the criterion is ease of landing and departing, then a planet is silly.
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  25. #125  
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    Rather than try and mine Mercury - or Mars - I would try shifting an asteroid into an eccentric orbit that takes it close by the sun and back out to Earth or Mars vicinity; do the heavy energy processes during the solar fly by perigee, offload the processed materials at the more distant apogee. If not a whole asteroid, maybe the processing factory could be in that kind of orbit and it could take on more manageable volumes of raw materials at apogee. No likelihood of rich veins of nuclear fuels though.

    This is hypothetical, because I think we are a long, long way from any viable enterprises in space beyond the close vicinity of Earth - and those will remain dependents of Earth for the foreseeable future. If we don't sort out some serious problems with how we do things here on Earth I think the window of opportunity for mines, factories and colonies in space will never really open. Because nothing less than a very large, successful, sustainable economy here on Earth will be able to afford the long R&D processes to develop the means.
    Last edited by Ken Fabos; September 6th, 2013 at 06:38 PM.
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  26. #126  
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    Quote Originally Posted by billvon View Post
    Quote Originally Posted by moonguy View Post
    The Mars crew module would still have to be larger and heavier even if it is made of the same composites as the Mercury module. It has to take more than twice the food, air and water as the Mercury mission and its power system would have to be larger
    Food - agreed. Air and water can be recycled. (A cool byproduct of this is methane, which can be used as fuel or just vented.)

    The presence of billions of tons of water and hydrocarbons has been confirmed by the MESSENGER mission. So Mercury does have the resources for propellant production - and the energy, which Mars is lacking.
    Mercury has no atmosphere, thus there is no easy way to access those water and hydrocarbons. Sure, you can envision a robotic mining/extraction/refining facility but again we are decades away from that. On Mars all you need to do is open a valve and let the atmosphere in.

    Delta-V for landing and lifting off of Mars and Mercury. For Mercury, it is about 3100 km/sec. This is about 50% more than for landing on the Moon. In the Mars case, using its atmosphere to land effectively cuts your landing propellant requirement. The problem is you have to have a heat shield and structure to protect your payload. And you need both to lift-off again, even though they represent lost cargo capacity and dead-load.
    Yes, but again, using Martian atmosphere for fuel greatly reduces the fuel that has to be transported there.

    To summarize, we can get to Mercury using equipment NASA is already planning to build.
    True of both efforts. Mars missions have a lot of planning behind them.
    I emphasize the last sentence because it is EXACTLY why I brought this to this forum. NASA has never done a comprehensive study of a manned exploration of Mercury. If they did, participants would have encountered all the issues that have been presented here so far - and then considered ways they could be resolved. They would not just cave in and say 'impossible' without a thorough examination. That is what I hope to accomplish here. I'm challenging people here to think through the assumptions and preconceptions. . . I'm definitely NOT asking people to accept my positions without question or challenge. I have begun a thread 'Mercury: A Case For Settlement' for those who feel up to the challenge of working the issues constructively. . . I hope you will look into it. Besides, I don't feel comfortable using someone else's posting to work my proposal. I apologize to the original poster and hope there no hard feelings. . .
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  27. #127  
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    To Ken

    Re asteroid mining.

    There is no need to move asteroids, which would be damn near impossible anyway. (Ever calculate the momentum change required for a body 20 kms in diameter, and travelling at in excess of 10 kms per second?). For early asteroid mining, there are already a number of asteroids whose orbit takes them close to Earth. Unload a pile of robots onto the asteroid as it comes close, and they will go to work. Several decades later, when the asteroid again approaches the Earth, the robots launch space shuttle shaped crafts, each made of a different metal, into low Earth orbit. Of course, I am assuming that, by the time this is attempted, robotics will be developed to a much greater extent.
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  28. #128  
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    Quote Originally Posted by Ken Fabos View Post
    Rather than try and mine Mercury - or Mars - I would try shifting an asteroid into an eccentric orbit that takes it close by the sun and back out to Earth or Mars vicinity; do the heavy energy processes during the solar fly by perigee, offload the processed materials at the more distant apogee. If not a whole asteroid, maybe the processing factory could be in that kind of orbit and it could take on more manageable volumes of raw materials at apogee. No likelihood of rich veins of nuclear fuels though.

    This is hypothetical, because I think we are a long, long way from any viable enterprises in space beyond the close vicinity of Earth - and those will remain dependents of Earth for the foreseeable future. If we don't sort out some serious problems with how we do things here on Earth I think the window of opportunity for mines, factories and colonies in space will never really open. Because nothing less than a very large, successful, sustainable economy here on Earth will be able to afford the long R&D processes to develop the means.
    The Mercury Project is only secondarily about mining. Settlers would have to mine minerals, if only for their own use. However, there are other interesting reasons for settling Mercury. There is more on the thread 'Mercury: A Case For Settlement'. I hope you will check it out and consider contributing. . .
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