A Lunar Colony

[chriscdc]

This will be far worse than sand on scuba equipment. The particles will be finer. A lubricant will evaporate in space. You may be able to easily replace it on a space suit, but not on buggies or diggers or lifters.<br /><br />The diamond seals would be polished before being put together. Any remaining dust will be so small that the gaps it would cause would cause negligable loss of atmosphere. Perhaps there could be an inner layer of a plastic material that will seal if there is a pressure difference. Remember that there was an incident were a seal around a thumb failed on a STS flight. The astronauts own skin provided an adequate seal.

 

[mlorrey]

Was just reading the article on 'lunar storms' today, about a ionic storm of dust that occurs at the terminator line, as it seems the voltage between the front side and back side causes the storm at the terminator. This means that dust should be able to be removed pretty easily by Ionic Breeze type air filters, and suits should also be able to repel accumulated dust through electrostatic processes.

 

[rocketman5000]

even more interesting in that article is that every earth days the winds will sweep across the station, and it could change the thermal absorbative properties of your habitat. If you had a sintered dome I don't see this being a problem as the dust should be similiar in color and thermal properties as your dome. <br /><br />Another interesting device would be the lunar vaccum. similiar to a static ball or roller to clean up interior surfaces of the hab of the dust. someone either in this forum or in the technology forum a couple of days ago ask if a vaccumm cleaner would work on the moon. They were talking outside but I suppose you could vaccum outside as well; wouldn't see the point though. <br /><br />One question I have is how long does the lunar dust hold its charge? If it becomes grounded against surfaces in the habitat will it become neutrally charged? could make it harder to clean up if it did, but less of a danger to electronic equipment.<br /><br />lastly what will the dust do to communication during these storms? After these storms will the dust coat the communication dishs and make them inoperable? <br /><br />oy questions questions questions

 

[dan_casale]

stevehw33:<br /> />>Lower temps mean lower solar panel efficiencies.<<<br /><br />quite the opposite, at least for the panels I have. The formulas are Amps 0.00318/deg C and Volts -0.123/deg C. This means that for every degree C below 70C the amperage will fall by .00318 amps and the voltage will rise by .123 volts. The effect is that the panels will produce more power in colder weather. Also the night might not be as dark as initially thought, the Earthshine might be enough to generate some power during the night, as the Earth will reflect more than twice the light of a full moon.<br /><br />This might indicate a possible problem from moon dust. http://science.nasa.gov/headlines/y2005/07dec_moonstorms.htm?list160994<br /><br /> />>As none have supplied reliable and reasonable solar insolation figures for the lunar poles,....<<<br />That figure is known. It is the same as Earth orbit.<br /><br /> />>A nuclear reactor will supply the power, day and night, 24/7 and for decades.<<<br />As you have still not supplied links, and I decided to write a paper on Mars subsystems, here are some links on the SP-100 reactor.<br /><br />RTG (SNAP-27): http://www.nasm.si.edu/exhibitions/attm/nojs/la.s27.1.html<br />(SNAP-10A): http://ieeexplore.ieee.org/iel5/852/2490/00074620.pdf?arnumber=74620<br />Fission (SP-100): http://fti.neep.wisc.edu/neep533/SPRING2004/lecture23.pdf and http://gltrs.grc.nasa.gov/reports/1993/CR-191023.pdf<br /><br />enjoy.<br /><br /> />>The airlocks are going to be necessarily equipped to

 

[mlorrey]

Well, yes and no. Solar cells generate more power if you have a more efficient heat radiator on their dark side, which is why they are working on quantum tungsten matrices as very high quanta extractors. Solar cells are more efficient at higher solar flux levels, which is why solar concentrators are beneficial (beyond just saving the cost of covering a whole area with solar cells).<br /><br />The moon reflects 0.02 lumens or thereabouts, far too little to generate power from.<br /><br />Actually, the 3% efficiency in agriculture is the efficiency of chlorphyll to convert light to atp at earth standard flux levels. You have a number of other efficiencies to calculate in there as well, but ostensibly you really want to be lighting your agriculture with sunlight piped straight through a system to shield against harmful radiation. Otherwise, you bring in the terrible efficiency of PV cells and light bulbs in the middle there, to cut it to below 0.1-1%.... and don't forget heating to keep your plants from freezing....

 

[chriscdc]

Um... you gave me the moon storm page.<br /><br />Interesting links on the nukes though. Annoying how they spent over 90million in one year on it and it still wasn't allowed to go anywhere. I wonder how up to date that 2004 article was as it didn't give any references for the cost installed We graph.<br /><br />On the filtering of moon dust, I'd rather use a centrifuge, just to save on cleaning filters. The sludge could then be removed and the remaing water could be evaporated.

 

[dan_casale]

mlorrey:<br />We agree, heat is the enemy of solar PV power. I agree light tubes would be ideal, but there are better things than light bulbs (of any kind) for making plants grow, because the spectrum isn't optimumal for plant growth. The mix of blue and red LED's improve the power to plant production ratio.<br /><br /><br />chriscdc: />>Um... you gave me the moon storm page.<<<br />Yes. From the article,<br /><br />...a few hours after every lunar sunrise, the experiment's temperature rocketed so high--near that of boiling water--that "LEAM had to be turned off because it was overheating."....<br />Those strange observations could mean that "electrically-charged moondust was sticking to LEAM, darkening its surface so the experiment package absorbed rather than reflected sunlight," speculates Olhoeft.<br /><br /><br />It seemed relevant to the mylar cover in that the temperatures might be much higher than expected. I wonder if the weight of the dust will become a factor. It could become a real problem for that large solar farm I have been proposing. It might require one FTE just to clean panels every few sunrises.

 

[chriscdc]

But this effect will only be significant at the equator where the difference will be most extreme, and the equator is not the place were you need solar collectors. The polar regions where you need the collectors, the ground will be in permanent twilight and so will not experience this change in potential that causes the storm.<br /><br />The easiest system would just be for the system to roll up when it nears the day-night zone. You probably just need a spring that expands when heated. When the spring cools, the reflectors close up. Place passive reflectors in the right position and the collectors will only open at a certain time during the day.

 

[mlorrey]

Well, LEDs are more efficient, about 96%, but they achieve this primarily by being cold light sources. The watts per lumen isn't measurably different from bulb technologies, once you measure the heat that bulbs produce and calculate how much of the bulb wattage is simple black body radiation outside the visible spectrum.<br /><br />That being said, particularly during lunar night, light bulbs are very efficient heaters... <img src="/images/icons/wink.gif" /><br /><br />Now, if you really want to get efficient light, electroluminescent lamps will do the trick, though the industry needs to move beyond the printing technology they use currently in order to allow higher brightness lamps while preserving the long lamp life.

 

[spacester]

I've only a coupla minutes right now, so y'all get a short post for a change. <img src="/images/icons/laugh.gif" /><br /><br />I do not see an error in my energy calc. I chose to use 1% rather than 3% in order to provide a reasonable baseline: 6000 kcal/day at 1% efficiency requires how much continuous power generation?<br /><br />Look at the units, always look at the units. And the parenthesis. <img src="/images/icons/laugh.gif" /><br /><br />I wrote:<br />(6.978 kilowatt-hour/person-day) / (0.01 efficiency * (24 hour/day))<br /><br />Which can also be written as<br />[(6.978 kilowatt-hour/person-day) / (0.01 efficiency)] / 24 hour/day<br /><br />'hour' on top cancels 'hour' on bottom, 'day' on bottom cancels 'day' on top<br /><br />Note that the 24 hour/day needs to be on the bottom of the expression or you end up with<br /><br />(kilowatt * hour^2) / (person * day^2)<br />which is nonsensical. Also note that your result requires 16 MEGAwatts per person - does that seem reasonable?<br /><br />So I stand behind that result in terms of a baseline number that allows one to quickly account for efficiencies other than 1% - if we can do 3%, then the power requirement is 1/3 of the baseline - roughly 10 kw/person. <br /><br />Take another look at the relationship between energy and power, and kilowatt-hours and kilowatts. I explained it much earlier in the thread, let's see if I can find that . . .<br /><br /><font color="yellow">(BTW, there is often confusion, even by good engineers, on power and energy and kilowatt-hours. Power is energy divided by time, and it's that rate of generating energy that matters when designing a power plant. But the folks paying for the electricity are paying for energy, not power. So you multiply power by time to get back to energy. The energy is in Joules, divide by seconds to get watts; but then when you bill the energy usage, you multiply kilowatts by hours.) </font><br /><br />Which perhaps is still confusing, I'll try again.<br /><br />kilowatts measur <div class="Discussion_UserSignature"> </div>

 

[scottb50]

My only difference with the power lander is putting your eggs in one basket. If you had many sources of power feeding a central bus you would have the same thing, continuous power that can have local needs met by tailoring the number of units.<br /><br />Do the hydrolizers the same way, each one has its own private solar array, with the deluxe Sun trackers and Earth trackers if they help, connects to a common bus. Work them around the clock on the moon and daily on Mars. With good, but simple, insulation, it should be easy to store enough Hydrogen and Oxygen to last the night, or several nights. <br /><br />Which in my book means multiple small storage facilities and a Common Bus for every usable product, electric, Hydrogen, Oxygen, Nitrogen, water, data, ect, that connects when a Module docks to any other Module or group of Modules.<br /><br /> <div class="Discussion_UserSignature"> </div>

 

[dan_casale]

Spacester:<br /> />>(6.978 kilowatt-hour/person-day) / (0.01 efficiency * (24 hour/day)) = 29.1 kw/person<<<br />The problem is in the evaluation. (.01 * 24) is 1% of a 24 hour day. The problem is that 1% of 6.978 kilowatt hours is being converted into food energy. Thus the equation must be evaluated as 6.978 / .01 = 697.8 * 24 = 16,747.2<br /><br />But in writing this I see that the entire concept is wrong because we need KWh/Person/Day thus the *24 is redundant or the energy needed for 24 people.<br /><br />6.978 Kilowatt-hours/person/day / .01 efficiency (light to food) = 697.8 Kilowatt-hours/person/day * the number of people to be fed.<br /><br />697.8 KWh/person/day / 24 hrs = 29.075 KWp/person<br /><br />OK, I see your figure now. *smacks head* I assumed that 29.1kw was 29.1KWh not 29.1 KWp. (Where h = hours and p = specific power.)<br /><br /> />>Also note that your result requires 16 MEGAwatts per person - does that seem reasonable? <<<br />It was a little higher than I had previously caldulated but then again the calorie count had been doubled.<br /><br />From my previous post on biosphere systems:<br />"Light from green house lamps @ 5.445 MWp/acre). Now if sunlight is 100w per sq.ft. and an acre is 43,560 sq.ft and we want to provide lighting for 4 acres, we need (100 * 4 * 43,560 / .8 = 21,780,000 watts = /> 21,780 MWp * 24 hr = 522.720 MWh's/day."

 

[mlorrey]

I would say that 1% efficiency is optimistic, using the very best GAs/An solar cells at 33-36% efficiency (i.e. cutting the 3% photosynthetic efficiency by three). This also assumes 100% conversion efficiency in any LH2/LOX fuel cell energy storage system, which is unrealistic. Cracking water is rarely more than 95% efficient. Recombining in a fuel cell has a maximum theoretical efficiency of 80% with hydrogen, typically 60% is more reasonable. All efficiencies need to be piled on top of each other to figure out the efficiency of the entire system, which will decide how many solar cells you need for each person. <br /><br />And this is just the getting light to the plants. You also need to keep them warm enough to stay alive, keep them supplied with sufficient quantities of air and trace gasses, water, etc. And this says nothing about keeping the person alive with air, water, and heat.

 

[chriscdc]

Apart from recycling, is there any reason to need the plants growing through the night? Green houses may be difficult to construct but they allow more of the light through and so will require less area than the solar panels.<br /><br />We just need plants that can be planted and harvested 14 days later. This way you have the stores ready for the night and so you don't need heaters. You would have to store the oxygen generated, but we are already planning on doing that.

 

[nexium]

Hi josh: I'm amazed that signifcant dust levitates electrostaticall to a heigth of 100 plus meters. Perhaps we can use several million volts dc to reduce the quantity of dust in selected areas? Neil

 

[josh_simonson]

At the poles a rotating reflector could continuously shine light upon your crop.<br /><br />I believe that the artificial light option will win out though for several reasons. 1, glass is brittle and could break. Greenhouses would be dangerous. 2, a greenhouse lights one, flat, plane of plants, requiring a large footprint, but small height. 3, cosmic radiation would kill your plants and gardeners unless the glass was several yards thick.<br /><br />Now under artificial light, you can grow many levels of plants stack on top of eachother, fitting into a relatively compact cube shaped volume instead of a huge pancake.<br /><br />4 acres of crops, flat, with a 2m cieling (kinda short but..) has a surface area of 32936 square meters enclosing it.<br /> <br />4 acres of crops in a cube with 2m levels makes a 32m cube with surface area of only 6100 sq meters. <br /><br />Now, can the equipment to generate the power to grow the plants be cheaper than 27000 square meters of outer wall, including 16000 square meters of radiation shielding glass?<br /><br />A hypothetical BFR could launch the 32m cube farm in one piece.

 

[nexium]

Several yards of quality glass has high energy loss. Moon glass several yards thick will deliver almost no light to the plants. Mirrors can however reflect the desired wave length while absorbing or passing though harmful photons, ions, and nuetrons. This was the method suggested for the ONeal colonies, so it may be good science. Neil

 

[mlorrey]

once again, Josh, you are making some unwarranted assumptions...<br /><br />Light piping is already a well developed technology here on Earth. There is no reason not to have solar concentrators concentrating light into periscopes that transmit light through a few mirrors into a pressure dome that is regolith covered.

 

[mlorrey]

During their 'budding' phase of fruit growth, it is found that they can produce bigger fruit faster with longer and longer days, up to as much as 23 hours a day can be tolerated during the fruiting phase to great benefit. if you can find plants that live by 28 or 56 day life cycles, you can cycle your crops well with the lunar day.

 

[nexium]

Light piping for communications, yes, but can I buy a light pipe sky light that delivers even 100 watts of solar energy to my room? Neil

 

[josh_simonson]

>There is no reason not to have solar concentrators concentrating light into periscopes that transmit light through a few mirrors into a pressure dome that is regolith covered. <br /><br />They'll require huge amounts of electrical power anyway, it should be cheaper to scale up the power plant they already need than to create such a complex system that only serves one purpose. <br /><br />High power optics inside a pressurized structure sounds like a recipie for disaster too. A mirror failure or cut cable could easilly burn through aluminum walls or people at a distance. Electricity can only cause damage through contact.

 

[spacester]

This is just getting silly. Has ANYONE bothered to check out the power lander? <br /><br />Periscopes? Mirrors? Bah! Optical Waveguides! <br /> <div class="Discussion_UserSignature"> </div>

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>Light piping for communications, yes, but can I buy a light pipe sky light that delivers even 100 watts of solar energy to my room? Neil <p><hr /></p></p></blockquote><br /><br />Yes, even with passive systems. With an active system that has movable reflectors, it is hard to avoid getting lots of wattage. Suggest googling.<br /><br />This isn't about fiber optics, this is about tubes and mirrors and prismatic diffusion films used to illuminate internal spaces.<br />http://aic.stanford.edu/jaic/articles/jaic32-03-006_4.html<br />http://www.publicworks.qld.gov.au/showcase/tafeLights.cfm<br />http://www.fsec.ucf.edu/Bldg/active/fenestration/solLighting/piped.htm<br />http://www.fsec.ucf.edu/Bldg/active/fenestration/solLighting/index.htm<br />http://www.physics.ubc.ca/ssp/research/solarlighting.htm (check out the videos)

 

[mlorrey]

<blockquote><font class="small">In reply to:</font><hr /><p>>There is no reason not to have solar concentrators concentrating light into periscopes that transmit light through a few mirrors into a pressure dome that is regolith covered. <br /><br />They'll require huge amounts of electrical power anyway, it should be cheaper to scale up the power plant they already need than to create such a complex system that only serves one purpose. <br /><br />High power optics inside a pressurized structure sounds like a recipie for disaster too. A mirror failure or cut cable could easilly burn through aluminum walls or people at a distance. Electricity can only cause damage through contact. <p><hr /></p></p></blockquote><br /><br />Once again, Josh, you are making assumptions without doing the requisite calculations. The facts are that photovoltaics are, at best, 33% efficient, and less so with more affordable units, also less with lower light concentrations (Mars, for instance). Light piping ranges from 60-100% transmission efficiency, depending on the pipe length to width. So, automatically, you need 2-3 times more payload mass for solar panels than you need for light piping... Try to think things through in the future.

 

[j05h]

(way to many Joshs kicking around...)<br /><br />I'm all for domes and bubbles riddled with lightpipes. I think it's a great way to create sustainable ecosystems and high-mass thermal storage (liquid water). Every dome should have a small sea or brackish lake. Direct illumination provides heat and plant growth, fueling the food supply.<br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>