A Lunar Colony

[chriscdc]

Ah, the advantages of just randomly searching the net.<br /><br />http://www.uh.edu/collegium/print/spr03/pages/moon.html<br /><br />PDF warning<br /><br />http://www.aip.org/tip/INPHFA/vol-8/iss-2/p12.pdf

 

[tap_sa]

<font color="yellow">"well, as usual you never deal with the problems suggested. Mylar has not been tested in space. It may not hold up to sunlight and the extreme temp changes."</font><br /><br /><img src="/images/icons/rolleyes.gif" /><br /><br />Echo, Apollo LM descent stage thermal blanket ...<br /><br />

 

[chriscdc]

Yes that repeating is a problem that I have. Momentarily get distracted and repeat a word, no big deal but I pay attention to mathematical equation. <br /><br />Of course mylar was just a suggestion, you could use entirely metallic sheets, perhaps a sheet of metal with a thin layer of very thin metal that is can be layed down as highly reflective. The problems that effect mylar include UV and particulate radiation. UV is stopped easily by the aluminium and there are plenty of examples of this. Particulate radiation is an unknown factor but would be very easy to test. It's light, so it would be easy to replace. Metallic sheets can be easily manufactured using resources in situ. So how many micrometeorites are you expecting to hit the sheet. Also they are micrometeorites, the important bit in that word is micro, in other words it will not rip great big holes through the sheet. It will take millenia before the sheets are worn through.<br /><br />The carbon ribbons do actually exist, they were in the news a few months ago. Amazingly easy to manufacture, one of those eurika moments, and they have been testing it and one thing they discovered was that it can act like a filament. It also generates heat when exposed to microwaves, allowing it to fuse to plastic materials.<br />There are also graphene sheets that could display interesting electrical properties.<br /><br />Well considering how beaming microwaves is a highly efficient form of energy transfer. The rectenna for recieving power can have convert 90%+ of the energy recieved into electricity. No part of the system requires an atmosphere and use electronics that are relatively resistant to the radiation in space. You can make an array of rectennas that is very light weight, think about the wiring on the door of a microwave to get an impression.<br /><br />Why do you think that the polar sats are to convert solar power to microwave energy? I kept saying that they merely reflect light. You might as well use the service modules

 

[nexium]

I agree a modified marine nuclear reactor on the Moon (or elsewhere in space) offers more power than we can expect from solar panels. With present lift capabilities, perhaps 50 separate peices must be delvered, then assembled at location. Waste heat disposal is a major problem. While the reactor is reliable in a submarine, it may not be on the moon and major re-design and repair may be required. Several back up energy systems would be prudent. If these marine reactors were easily scalled back and made much lighter, we would be using them in airplanes and missiles. We can't be sure a practical moon reactor can be developed even if we appropriate 100 billion dollars per year for the next decade or two.<br />The desired scale of solar panels and energy storage is largely untested anywhere in space. Buiding solar panel from moon dirt needs to be tested by building solar panels from roughly equivelent Earth dirt.<br />If we want low risk for the humans we put on the moon, we need to find natural caverns and modifiy them. My guess is 100 meters below the surface may be the best compromise. Near zero radiation will directly reach the humans from the surface, but the cavern walls may be significantly radioactive and moon dust tracked from the surface is likely toxic. Waste heat disposal will be easier at selected locations near the poles of the Moon, but there may be some surprises when the caverns and tunnels to the surface are warmed to a comfortable temperature for humans. A dome with 5 meters of regloth will be less safe in almost every respect and has few, if any, advantages over the deep caverns. Neil

 

[chriscdc]

I just did some maths for a very basic model of the moon surface. <br /><br />Imagine that the lowest edge of the cells is 100km from the pole. In order to absorb the same amount of light as a panel 1km2(perpendicular to light), you would need a field of cells going back 16.6km2 (very approx).<br />Actually the polar diameter makes this calculation irrelevant as the polar diameter is lower than the values that I was using in the calculation. This doesn't take into angled solar cells or the craters near the poles. Also a orbiting solar mirror would easily improve the amount of light falling on the cells.<br /><br />Actually the maths describes the light falling on the cells near the twilight zone.

 

[Swampcat]

stevehw33, thank you for those two excellent posts. They were very objective and informative.<br /><br />Well done. <div class="Discussion_UserSignature"> <font size="3" color="#ff9900"><p><font size="1" color="#993300"><strong><em>------------------------------------------------------------------- </em></strong></font></p><p><font size="1" color="#993300"><strong><em>"I hold it that a little rebellion now and then is a good thing, and as necessary in the political world as storms in the physical. Unsuccessful rebellions, indeed, generally establish the encroachments on the rights of the people which have produced them. An observation of this truth should render honest republican governors so mild in their punishment of rebellions as not to discourage them too much. It is a medicine necessary for the sound health of government."</em></strong></font></p><p><font size="1" color="#993300"><strong>Thomas Jefferson</strong></font></p></font> </div>

 

[chriscdc]

Thinking about the whole system again. It would be more efficient if there were several solar power stations around the equator transmitting power via microwaves to the polar orbiting satellites. The reflective metal mentioned earlier would reflect the microves to the point on the moon that they are reqired at. This gets rid of the problems of the low insolation at the poles. This way you only need rectennas at the pole, which are relatively simple and so less likely to fail. <br />Even if something goes badly wrong at one solar power station, you would have several others ready to take the strain.

 

[rocketman5000]

I like that idea, it would allow a more uniform flow of electricity all month long. Do you have any numbers as to the amount of power lost due to trasmiting via microwaves? I assume rectennas aren't 100% efficient

 

[nexium]

Beaming power by lasers or microwave is low efficiency small scale, likely best medium scale, with rapidly escalating problems at very large scale. At www.liftport.com you can find details on a single wavelength solar panel in infrared that is 80% efficient and the laser to produce that wave length. The plan is to beam the laser energy to the photovoltaic panel mounted on the climber/lifter going up the space elevator which we may build in 10 or 20 years. The climber needs to be powered by the laser beam all the way to Geo sychronous orbit = 36,000 kilometers. Average efficiency is perhaps 1% with soon to be available technology which is acceptable for the space elevator, but not for moon energy needs or to replace fossil fuel use on Earth. Microwave energy beaming may be 10% overall efficiency, which makes it marginal for energy trasmission in most applications. Near term we can use klysitrons which require several amps at 100,000 volts. Ten of them in a series string operating at a million volts dc from a large number of solar panels in series. There is perhaps 5 million watts of energy in the beam (12 million watts from the solar cells) so several of these systems are needed to provide the energy needs desired by a few hundred moon colonists. 100 mylar or other mirrors in low moon orbit can reflect the beam to rectenna sites all over the moon, with typical rectennas receiving a beam 90 plus percent of the time. Some of the reflected beam will miss the rectenna, so 3 megawatts falling on the rectenna is optimistic and 2 megawatts dc output from the rectenna is optimistic. Some applications can use the dc, but 400 hertz 120 volts may be the standard. 100 inverters in series can produce 50,000 volts ac at perhaps 80% average efficiency = 400,000 watts if the output current is ten amps. Locations near each rectenna can be connected to a local grid with a pair of wires carring both the high voltage dc and the hig

 

[chriscdc]

In the time I have available, I wasn't able to find the details you mentioned on liftport.<br /><br />Several differences exist between using infra-red lasers and microwaves exist. The efficiency of generating the beams at the beginning. I do not know at the moment how efficient it is to generate microwaves, but there are several other methods including integrated circuits, which will allow more scalabilty than the klysitrons. There are also Travelling wave tubes that have been used on satellites.<br />The distance that microwaves will need to travel from the equator of the moon to the poles, is around 3000km if low altitude satellites are used. But it might be better to use satellites in higher orbit as they will be over the traget site for longer and so transmitting energy will be easier (slower alignment needed etc). Whereas the elevator has to get through the atmosphere and then has ten times further to go.

 

[nexium]

Hi Steve: Criscdc was assuming that the moon colonists live at ten or more widely scattered location on the moon which would require perhaps 20,000 kilometers of intercoinnecting grid which might have power losses exceeding 90%. Your nucelar plants could be connected to that copper grid, or microwave grid. Failure to have a grid, means most of the habitats typically have twice as much energy as they are using, while one or two have a dangerous shortage of power. Neil

 

[nexium]

High chriscdc: As far as I know traveling wave tubes and klysitrons are approximately the same thing. Many decades ago efficiency was about 50% and magnetrons about 70%, but magnetrons can not be modulated with high speed data, which would be very useful to interconnect the moon habitats. Likely the intigrated circuits used to power satellite down links are even more efficient, but I think thousands of chips are used to produce a few hundred watts, so scale up to megawatts may be impractical.<br />Perhaps worse problems than the efficiency of the microwave source is the enourmous size of the transmitting and receiving antennas and the mirrors. Using a tighter beam produces another health hazzard for the colonists. The international max allowable exposure is 1/10 watt per square centimeter = one kilowatt per square meter, but we can expect hot spots in the beam. A tin foil hat reduces exposure. Neil

 

[rocketman5000]

I don't think initially there will be wide spread settlements. It makes sense to hudle colonist together to create a critical mass of people that has better chance of survival. So initially I believe a power grid wouldn't be neccessary

 

[spacester]

Well there may or may not be a global grid, but certainly we need to think about a local grid. 500V 3-phase delta power can be distributed over moderate distances between various operations in a lunar industrial park. Good old fashioned extension cords. Lunar rated of course, but copper wire will work nicely for a local grid.<br /><br />I agree with the idea to huddle together for that critical mass of survivability, so I think a single large facility needs to be successful first, but global domination would be the next step and in fact the true goal.<br /><br />My vision is for two large domes, one at Earth-Rise, one at Earth-Set, which are there to not only support large numbers of people for the sheer joy of it, but to support a global scientific effort. A third facility on the Far Side would be all about Science, perhaps not so large. These would be developed by consortiums concurrently with space-agency development of the poles. <br /><br />The two large domes are about what I call “fulfilling our destiny” but I suppose most folks see it as “space tourism”. Oh well, I guess I can live with that. <img src="/images/icons/laugh.gif" /><br /><br />The goal of the space agencies would be Science and Utilities. All those things we don’t know about the moon but that we need to know can begin to get answered right away. Since the poles are such prime chunks of real estate, I’m not going to even try to work my off-beat Other Way Lunar Dome strategy into those land-use plans. <img src="/images/icons/laugh.gif" /> I’ll just pick a strategic spot somewhere else and hope maybe someday there will be electricity and water available from the poles.<br /><br />If we don’t want to wait for ‘some day’, we need to make our own electricity. Note that if we stick with robotic operations for a while, we don’t need water or oxygen industries. We just need to establish a local grid for our little industrial park. But we should keep in mind that later on we will be looking to tie in with a global gri <div class="Discussion_UserSignature"> </div>

 

[rocketman5000]

Your comments bring up an interesting point. Here on Earth we have grids for water, electricity and sewage. it really wouldn't be a strech to envision a central faciality for O2 and CO2 that is connected to a grid

 

[chriscdc]

But even at the beginning, there will be reasons to explore.<br />If you plan on going long distances you will need a pressurised hab, and what will power that? Chances are that groups of scientists will want to study areas for a long time, or require diggers or construction equipment to construct lunar telescopes etc. <br /><br />The 2 things that will get a base funded are science and resources, both have reasons to have a number of people separated. Science wants to study the impact craters andbuild telescopes. Business wants to strip mine the equatorial regions for He3 or for valuable metals.

 

[scottb50]

So you want to haul Copper wire to LEO and then to the Moon?<br /><br />It's much easier to use fuel cells. It also lets you isolate problems, if you don't depend on the same wire. <br /><br />I also wince at the word large. Survival depends on increasingly smaller spaces. I envision a self-contained, maneverable Pod that would be private living quarters until all hell breaks lose and then you dive into the nearest Pod.<br /><br />Does this mean I'm parinoid? <div class="Discussion_UserSignature"> </div>

 

[spacester]

I prolly wasn’t clear on the copper wire. I’m talking about short distances (tens of meters) between various pieces of equipment parked near each other in our Lunar Industrial Park. Any kind of global or even regional grid based on wire over long distances is going to be a result of ISRU successes (locally produced aluminum most likely). I’m just saying that if your mission requires that you get power from A to B and you keep your operations close together, you can afford to haul the wire up there. If your mission is *not* to develop more exotic methods like laser beaming, but to build a habitat, well there’s not much more dependable technology than using copper to move electrons. <img src="/images/icons/laugh.gif" /> Yet, ultimately you may find that laser beaming is what allows you to conquer the globe, so you keep it in mind for later.<br /><br />I’ve written some stuff for this thread that I haven’t posted yet because I don’t want to force my dome vision on a good generalized discussion of power systems. But I’ve got fuel cells in the plan. It’s just that I’m trying to land minimum mass to achieve maximum effect and part of the strategy is to support only robots for the first few years. Human helpers can visit and get the robots unstuck, but they bring their own life support. The robot-base construction plan does not require water and oxygen production because there are no humans to consume them.<br /><br />HOWEVER, the whole point of the robot-based construction program is to create permanent human habitats, and the oxygen and water production better be ready long before the people show up to move in. So those systems need to be tested and refined and tested and perfected. This is where the large size of the project works to an advantage: if it takes several years to build the shell of the main building, then you have several years to develop the systems to turn the shell into a habitat. There’s a lot to learn, so it makes sense to match the long-term construction wi <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

ought to consider microwave rectenna power transmission for 'nearby' systems that need power, or else give them their own solar panel installations.

 

[scottb50]

In my opinion the simplest, most cost effective and safest source of power in Space is water, solar power and fuel cells.<br /><br />Modular power units would be added as needed and as demand increased. The same units could also power construction robots, Hydrogen and Oxygen either carried or delivered through a tether. If a Unit fails it can be quickly replaced by another one or Units can be moved as needed to meet demand.<br /><br />I see little need for a power lander to supply an electrolysis unit when there is more than enough Sunlight available even on the moon. I would think it would be fairly easy to project the need during nights and size storage accordingly. <br /><br />What makes it even simpler is the lack of uplift needed to support the system. In a sealed environment I would think you could recycle the same water indefinitely, obviously there will be some lose, but when you figure the water people will need it will easily be serviced when needed. <br /><br /> <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p><br />In my opinion the simplest, most cost effective and safest source of power in Space is water, solar power and fuel cells. <br /><br />Modular power units would be added as needed and as demand increased. The same units could also power construction robots, Hydrogen and Oxygen either carried or delivered through a tether. If a Unit fails it can be quickly replaced by another one or Units can be moved as needed to meet demand. <br /><br />I see little need for a power lander to supply an electrolysis unit when there is more than enough Sunlight available even on the moon. I would think it would be fairly easy to project the need during nights and size storage accordingly. <br /><br />What makes it even simpler is the lack of uplift needed to support the system. In a sealed environment I would think you could recycle the same water indefinitely, obviously there will be some lose, but when you figure the water people will need it will easily be serviced when needed. <br /><p><hr /></p></p></blockquote><br /><br />Keep in mind nights on the moon are 14 days long. Do you have a battery that can supply a lunar lander enough power for 14 days? I can't think of one. Electrolyzing water is a little better, but you are going to need some significant water and fuel storage capacity. Gaseous hydrogen and oxygen take energy to liquify, have storage losses, and also take energy to transport from one location to another (as does water).<br /><br />Some of this could be mitigated by having big balloons on your installations, but one micrometeorite will wreck it.<br /><br />"Simplicity" is an SP-100 radiothermal powerplant, supplying 100kw for a decade.

 

[spacester]

Scott, your last post is one of those I stare at and can’t decide if you are agreeing, disagreeing, just making a comment or what.<br /><br /><font color="yellow">In my opinion the simplest, most cost effective and safest source of power in Space is water, solar power and fuel cells. </font><br /><br />I know. <img src="/images/icons/wink.gif" /> <img src="/images/icons/laugh.gif" /> And I pretty much agree. But the statement is strictly true only if you’re talking about <i>electrical </i> power. A lot of the energy of the sun is in wavelengths solar PV cannot capture. Turning that energy into <i>thermal </i> power is an attractive proposition as well.<br /><br />My goal is to establish the construction of a large facility; my goal isn’t to deploy fuel cells everywhere. I am concerned with minimizing the initial payloads so that I can get started on a low budget. If I can get started without dealing with water, well, that’s what I’m gonna do. I can do that by starting off with a power lander that is equipped with the solar thermal and the electricity needed to get started. Significantly, the power lander is also equipped with all the electrical power conditioning and distribution capabilities we will need for quite awhile.<br /><br />That means that if and when we deliver a large regenerative fuel cell test bed to our site, we can hook it up to the power lander and integrate that subsystem into our grid. If and when we produce solar PV from native materials we have what we need to hook them up and use them. Flywheels will have a place to hook up. In the meantime, small self-contained fuel cell units will be onboard some of our second-generation robots.<br /><br /><font color="yellow">Modular power units would be added as needed and as demand increased. The same units could also power construction robots, Hydrogen and Oxygen either carried or delivered through a tether. If a Unit fails it can be quickly replaced by another one or Units can be moved as needed to meet</font> <div class="Discussion_UserSignature"> </div>

 

[spacester]

Nice posts, stevehw33, especially, from my point of view, this:<br /><br /><font color="yellow">And regarding solar versus nuclear as the main power source for lunar habitats or stations, there is probably an honest disagreement. I don't see how solar can easily and reliably provide the demand/power density of nuclear. And the energy sources from nuclear isotopes are not high density, either.</font><br /><br />{To All: I sense an opportunity for this thread to make progress. I’m going to give another overview of my thinking, for those new to the thread, others should give their big-picture view again as well. Please forgive me for the length of this post, but I have enough info now to get more specific with my plan, and I couldn’t resist. Maybe we can come to some kind of consensus on the overall context we want this thread to go in, I’m not trying to insist my way is anything more than one possibility . . . }<br /><br />I also do not see how solar can easily do the job, but I am interested in exploring the possibilities. I’ve been looking into it for years: is there a way to build a habitat from local materials using solar energy as the mainstay? No matter the habitat design, we sure would like to have a nuke plant if we can get it. But what can be done without one? <br /><br />It’s a political tactic, if you will: if we try our best to design a lunar habitat strategy without nuke power, and things don’t prove to be practical on that basis, then we can demonstrate, not just claim, to our fellow citizens that we really need permission to use the nukes. IOW if we have a good plan for a base/settlement/colony but we just can’t do what needs to be done with solar alone, we can more easily justify the nuke. If we do in fact find a way to do it without nukes, well, let’s get started, why not? Let’s get started and add the nuke later.<br /><br />What I’ve come up with is a construction technique that can start small and grow from there. It’s based on teams of small robot <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p><br />BTW, from previous calcs, 10 kilowatts continuous power for 350 hours is 12.6E9 Joules of energy which is the amount of energy liberated from 37.4E3 cubic feet of gaseous hydrogen (burned with Oxygen) which can be stored in a cylindrical tank 50 ft in diameter and 19 feet high, or alternatively stored as liquid in 44.16 cubic feet such as a 4 foot diameter tank about 3-1/2 feet long. Note that you’re looking at around 3 kilowatts of useful electricity and less than 7 kilowatts thermal energy (steam or other heat exchange liquid) with losses. <br /><p><hr /></p></p></blockquote><br />This is at 100% conversion efficiency in every step. Lets plug some realistic conversion losses in there. It takes more energy to liquify hydrogen and oxygen.<br /><br />Now, 10 kw on the moon requires 30 sq meters of solar cells. As this only provides power that will be used during lunar night, you also need an equal amount of power for the person during lunar day, if not more for AC demands. Thus you are talking 60 sq meters per person, assuming one person can survive on 10 kw constant load for all life requirements.<br /><br />This is important, in budgeting energy: lunar settlers are going to have to develop agriculture. Shipping MREs to the moon will be insanely expensive.<br /><br />Chlorophyll is 3% efficient at converting solar energy. 1kcal = 1.161 watts. A 3000 kcal daily diet for one lunar settler = 3,483 watts. If working in a spacesuit on the moon is anything like living at McMurdo in Antarctica, settlers should budget 6000 kcal daily diets. That 6mcals per day is AFTER the 3% photosynthesis efficiency, thus if your farm is properly shielded from radiation, you will be lighting it with lights powered by solar panels or nukes, unless you learn to get creative with piping light. Assuming we are growing the crops with growlights, and a .90 power factor on the light power supply, agricultural needs for one person on the moon will cons

 

[rocketman5000]

wow that was a long post glad I was reading it at home. I like a lot of what you were saying. Let me ask you to clarify a couple of points. <br /><br />1. your first payload will it be a solar power device? sounds that way from what I infered. I believe this is a good option as the amount of power needed can be spaced out over a longer peroid of time. While you are mapping and testing I assume you could do it 14 days at a time? Maybe use RTG for "sleep" mode communication<br /><br />I wouldn't want to see this thread dy off, but I think the issue of power production system and grid arcitecture might be better served in its own thread. Keeping this thread for bringing to light issues and topics as they are thought out. I think specifics can be handled better where the topic won't bounce around as much. I feel that many times a subject has been caught of early when further discussion could have thrown out good ideas. You are escentially talking about building a new society. There are certianly many varied issues. I don't know just my two cents....