New Mars Forums

Well, there has been at least a small setback, I lost my tomatoes.   They started looking kind of wilted and stringy, then started loosing their leaves.  Finally, I gave up, turned off the grow lights and set them outside.  They seem to be doing nothing, I probably shocked them even more by putting them outside without a proper hardening off, but I think that either my lighting or watering was off too much, and figured that it would be best to try again.

I'm having problems obtaining samples of tefzel film, seems like every "distributor" wants to sell me several hundred feet on rolls but not just a few feet.  I'm thinking that I may just buy some and offer the rest for sale, but I have been trying to get in contact with someone at DuPont directly to obtain what I need.  Of course, I was not smart enough to approach this like I would at work and ask for a sample

I have come up with several circuits for monitoring temp, liquid water, pressure and light levels, but am still trying to figure out humidity.  I have a "humidity" sensor that I obtained as an engineering sample, but I only have the one, and small quantities are not readily available.  It also wants a serial data stream, which means that I would have to bit-bang a digital port into a serial interface.  I hope to layout and build the sensor subassemblies (including the circuits that are necessary to convert the output voltages/currents to 0-5 volt so I can read them with the 'HC11's onboard A/D converters over the summer, so that in October I can set up a greenhouse and try this out over the winter.

Bill White - I like the mylar idea, but I was thinking about using those space blankets, so I had large surfaces to work with and could shape them over a frame.  Also, I can get the space blankets for a few bucks from the drugstore.

Instead of a nuclear reactor, how about something like a solid oxide fuel cell?  The operating temp is about 800? C from what I have read, which means there would be waste heat to use, and you could use methane as a hydrogen donor gas, which puts it within the class of "cheap to fuel on Mars"

Finals are over next week, I plan on increasing the amount of time I put into this - incuding putting pictures up on a webpage so I can share what I have done!

I just wanted to update everyone on my progress and see if anyone had further inputs on the direction I am heading.  I've put about 6-8 or so hours of "real work" into this in the last month, I'm not in a hurry and so much of what I am trying to figure out is just basic ideas.

I've been looking around on the web for material that is transparent, has a wide temp range and a good insulation capability. What I have found is that I can pick any two of the above.

So, I decided that what I wanted was a UV shielded plastic that was transparent with as wide of a temp range as possible. Now, the thought is, build up layers separated by air pockets at low pressure, like bubble wrap packing material.  Now, as a vacuum is better at reducing heat conduction, how would you make bubble wrap that has vacuum pockets and make the whole shebang compact enough to fit on a small lander?  (I've arbitrarily decided that I want to target the size of a loaf of bread for this project collapsed, with the size of components determining the size of the greenhouse proper.) What I have figured out is that by using an inflatable support structure, I think I can hold layers of plastic mechanically separate from each other.  The question is 1) does anyone know of a better way to make this work and 2) how can I draw a vacuum through a tube made of readily collapsable material? I think there is a solution here, but I'm not sure yet what it could be.

I've planted 8 microtina tomato seeds, and now have 7 healthy plants.  This is in straight Tagro mix under an 80 Watt flourescent wide spectrum light connected to a christmas light timer on my workbench.  The Tagro does not stink much, it really does not smell like what it is.  I've set the timer to a 14 hour on cycle and the room heat is about 20? C.  They are about 5 cm tall, and have 2 or 3 true leaves above the seed leaves that have yet to drop off.  The whole point of this was only to get myself able to produce a crop indoors and to generate extra seeds for me to use later.  I'm a little low on temp and a little short on light for what USU recommends, but I seem to be doing okay for now.

I have also planted a variety of vegetables outdoors in the Tagro mix, right now only early season stuff like peas and beans but will get later season veggies planted as soon as it warms up. 

I've also started collecting vegan information, so I can decide what crops are most critical to grow.  I figure that I will concentrate on beans, rice and tomatoes.  I know that a wider variety would be desired, but my understanding is that if you have these three, you can survive.  I have also tired several tofu dishes and "meatless" food products (veggie dogs and gardenburgers) and have decided that I love animals, as they taste great.  Not that the vegan products are really awful, just tasteless and bland.

One other thought came to mind - most of these products are soy based, but what about mushrooms?  They would not require a greenhouse, and I suspect that it would be fairly simple to transport a spore impregnated log to Mars without much trouble.  Any thoughts?  What kind of plant based food should I work on growing - is there anything I'm forgetting?

Thanks for your inputs.

Okay, guys - here is what I have so far...

I aquired 2 pickup loads of "Tagro" from the City of Tacoma, WA - they make this compost from sewer solids, sand, and sawdust.  (www.tagro.com) I figure that after a short period of time the ingredients should be fairly easy to come up with on Mars, except for the sawdust.  I still need to do more research on what to use BEFORE the people arrive, but I am leaning toward adding the mass needed to carry a small amount of chemicals to get things started. I put most of the Tagro into raised beds in my back yard, and have planned on planting several varieties of veggies this year.

I have also aquired some MicroTina Tomato seeds from the Utah State University, which are now potted in 6 inch pots on my window sill in a mix of Tagro and potting soil.   I was only given a very limited amount of seeds, so I started several in the hopes of growing plants to generate enough seed to make it through this experiment.  (If I have any left over, I will be happy to share, but you may have better luck getting them straight from USU yourself.)   I figure that space will not be as much of a premium on Mars as it is in transit, so the super dwarf plants will not be as big of a requirement on Mars as they would be on the space station, but I can easily get baseline data from USU for these tomatos.  I need to decide what other crops will make it, I want to keep them small but at the same time I would like to include as much variety as possible.  Any suggestions?  Beans and rice...what else?

As for raising the levels of sulfur and chlorine in the soil simulant, would you guys think that just adding powdered sulfur and a chloinator (I am thinking bleach, but that's sodium hypochlorate - I don't think that will be close enough, but raw cholorine is some pretty nasty stuff to be playing with) would be enough?  I have no way of testing the chemical makeup of whatever I do use, but a general idea would be helpful.  I currently plan on getting the greenhouse roughed out first, then tackling the equipment to prep the regolith.

Another problem I am facing is temp. I can create -40? conditions fairly easily using liquid CO2 (in 1000 psi bottles) but I don't know if I can generate enough delta T to test the materials and heater system.  It would not be too hard to extrapolate the data to Mars conditons, but I don't think it would be accurate enough.  My first thought on this is to generate material that can hold delta T of 200?C+ while staying flexable, transparent and holding 5+ psi of pressure, testing at an elevated temp (160?C internal, -40? external) but I don't think that it would be a good model, as the properties would not be the same.  Anybody know enough about thermodynamics to tell me how to do this?

Finally, a Mars-Mix atmosphere should be easier to deal with, as I have access to liquid CO2.  I guess that I'm going to have to come up with a way to make it, but I don't think it will be too difficult to do - perhaps mix it as a gas in a bag by weight?  Any ideas?

Now, with all this being thought of, keep in mind that I don't mind ommiting parts of reality to keep within the scope of the project.  This is an EE project, realisim will get me an A but the electronics need to work to pass.

Okay, I'm with you. I don't see a flaw in your thinking at this point, although I can't imagine why NASA would bother to cover this up except to keep people from freaking out. (Which, with the state of education in the USA, I can easily see.)  I can just imagine the theological reprocussions among the stupids on this planet, an angry mob of bible thumpers rioting at KSC, and every grey haired old lady across the land would write her senator to tell him how much this has upset the congregation down at Wednesday night bingo. Science is just so evil.

Assuming that there is some kind of bio activity present, what you have told me seems to indicate that I could include the ability to heat sterilze the regolith before closing the "greenhouse."  Although this includes more mass in the package, it leads me down the path of a thermoplastic greenhouse.  Something that I can inflate and is flexible until the temprature is raised above 130? C, then becomes hard.  Perhaps I can do it the other way, use an thermosetting plastic that has a catalist that produces an endothermic reaction to sterilze the regolith?  (I don't know of such a plastic off the top of my head that is also transparent.)  The amount of energy to heat even a small amount of regolith to 130? C is quite large, so it seems the bigger I make this greenhouse the less it will cost to include the sterilizer (in terms of produced food/O2 vs payload weight - when does it become cheaper to just send the product than to send the factory?)

However, I still cannot see the return on investment of the payload in sending a hydroponic setup to when it's entirely dependent of Earth to send the chemicals to keep it running. I would think it would have to be something we could send that could reduce human waste (by mixing it with the regolith) into a useful product, and the answer I come up with is potting soil. (no pun intended.) You know, what do you think about the sterilizer being part of the waste treatment system? I think I could include the possiblity of the system being used at first to treat regolith by itself, then when humans arrive, treating solid waste as well.  I assume that I would want to mix the two, and the heat source could be used to extract water from the regotith as well... Humm.. I have some research to do.

Thanks guys - keep the comments coming.

I assume the superoxides would only exist in the top few centimeters - my understanding is that they are created by the reaction of high radiation on the chemicals in the regolith.  If I discard the top layers, I can bypass this problem.

I'm thinking about a senior project for my electical engineering degree (due in June of 2004) and am considering constructing a self contained "Mars Garden."   The idea is that I could create an inflatable tube greenhouse with a small robot that would tend plants inside.  However, I need to know what to include in the delivery package in the way of nutrients and stabilizers, as I don't want to include the mass of imported planting media.  The idea is that it would be something along the lines of a 25 kg mass could be added as a parasitic load on a precursor mission to Mars so that when the manned mission arrived, fresh food would already be waiting for them.

I came up with this idea when I was thinking about the problems of a centerfuge on a spacecraft being used to create "artificial gravity" and the gyroscopic procession that would be induced if the mass of that centerfuge was large enough to support a sizeable garden onboard.  I know that it can be accounted for, but simply not bringing a centerfuge along would be an easier solution.   Aside from that, what do you do with the centerfuge once you are on the surface?  Frankly, I don't think the return on investment is there for growing plants inflight in a Mars Direct style mission.

My next problem would be the materials needed to construct an inflatable greenhouse - Anybody know of an inexpensive UV resistant clear flexible sheet plastic that is not too difficult to work with?

BTW - I found the answer for my earlier question some time later during a web search, as NASA sells their simulant for $1 a pound.