Cheap Method Orbital Fabrication of Habitats

[rogers_buck]

I'm thinking about a method for fabrication of large solar sail, solar collector, or even orbital habitat structures. The idea is that you orbit a tank of liquid polymer that will harden when exposed to UV - fairly common stuff. The tank would be equipped with an axial dispenser on one of its ends. The method of deployment would be to spin the tank at a pretty good RPM with the dispenser facing the sun.<br /><br />As the polymer is pumped out of the tank it will naturally form a disk by balancing cohesive and centrifugal forces. The sun's UV will then freeze that polymer so it will no longer spread out. Polymer is being continuously pumped onto the center of the forming disk by the dispenser from the side of the forming disk shaded by the sun. This is important, because the solidified polymer will screen the liquid polymer from the UV until the new liquid polymer fans out to the edge of what was solidified adding to the circumference of the disk before it too is solidified by UV (no longer shaded). And so on until the desired diameter is achieved and the polymer tank is empty.<br /><br />The physics of this are quite interesting and the growing surface area that needs to be covered is automatically accomodated by a slowing down of the rotation of the tank-disk system. The pump needs only excrete the polymer at a steady rate. The natural physics take care of all the dynamics.<br /><br />Using this method it should be possible to construct a large flat disk of polymer film with an extremely simple mechanism. The ultimate size of such a disk is constrained only by the strenght and cohesive properties of the polymer.<br /><br />Once a disk is fabricated in this manner, it can be aluminized by an electric evaporation of aluminum or gold.<br /><br />To create a space habitat from two such prepared disks, the disks would need to be docked together and a robotic welder could crawl along the circumferences of the disks joining them together. After the edges are welded togethe

 

[chriscdc]

Interesting idea, it's similar to spreading a resist on a substrate in semi-conducting manufacturing. Can't help but think that things wouldn't be that easy to do in practice.<br /><br />There probably aren't any materials that would make that method better than a pre-prepared method. You could probably make thinner and pre-prepared stuff. <br /><br />This could be a way of applying a coat to a pre-laid surface (attraction between a solid surface and the coating, would make spreading easier).<br /><br />Also IIRC the resists (well resist) I worked with, needed to have the volatiles driven off. I guess most resists and polymers use a solvent, which takes up alot of mass.

 

[nexium]

In the vacuum of space the volitiles should be mostly gone in a few days, if not hours. Neil

 

[rogers_buck]

>> Interesting idea, it's similar to spreading a resist on a substrate in semi-conducting manufacturing. Can't help but think that things wouldn't be that easy to do in practice. <br /><br />Funny you should say that. I first thought of doing this back in 82, about the same time I was taking a graduate industerial semi-fab course. I have done the photo resist thing on the spinning wafer several times... Not too sure that isn't what made me think of this!<br /><br />The advantages of making a thin film disk like this would have to be size of deployment device and any benifits in the material itself formed in this way. One thing that comes to mind is that a disk made this way might actually be of a thicker material than would be practical to fold or wad up. Another advantage might be with the aluminization layer acting as a laminate between two polymer disk layers. Two aluminization layers bought into contact in the vacuum of space would weld. You could stack these layers pretty deep.<br />

 

[rogers_buck]

Let's figure out how big a disk you can get for 200 liters of polymer. Let's assume the thickness of a layer to be .2mm and that the material doesn't change size when UV cured. Taking r = sqrt( (2 x 10^5mm^3) / ( pi x .2mm) ),<br />which is about 100,000/pi or ~28m radius, or 56m diameter.<br /><br />Assuming a Pegasus sized launcher of about 500kg x a s.g. of ~ water, that would suggest a 100m disk could be spun with such a launch. Two such disks welded together would give a sphere of about r = 100m/pi, ~60m diameter sphere.<br /><br />Unless I made a mistake, thats a pretty good sized sphere in orbit for cheap.<br />

 

[j05h]

One of the guys I met at ISDC is working on something very similiar to this. Let me see if I can get his attention to this thread.<br /><br />What you are discussing would be easier to make as a sphere instead of disk. There was a thread last winter or fall about blowing glass in a vaccuum - surface tension makes perfect spheres fairly simple. O'Neill discusses it in High Frontier. Blowing poly bubbles is surely possible, would save a lot of manufacturing steps and be safer once deployed. <br /><br />Josh <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[chriscdc]

Yes, but what I meant was that the solvents had to be there to begin with, taking up mass on launch.

 

[chriscdc]

What you could do is have a 'walker' that moved along the edge of the disk. On one side it has a teflon substrate (catapillar track so it doesn't move relative to the previous layer) and on the other it has a spray gun. Now the polymer is sprayed onto the teflon substrate as well as overlapping the previous layer slightly and left to cure. Thus you can have a spiral shaped distribution method.<br /><br />Now the spinning method. Trying to spin up the whole mass would be too hard and I wouldn't know where to start mathematically modelling it. If you put a drop on the substrate as it was spinning and let it form a ring which then moved to the edge (which is far nicer for me to think about) then you would need to increase the rotation of the disk. Actually if you spun up the drop first then that might be easier.<br />Any slight clumping through would produce a center where there could be resultant forces. Simply that the drop ring would break into smaller droplets rather than staying as a doughnut.<br /><br />My brain hurts thinking about the physics of this, so most of what I say is probably wrong.

 

[rogers_buck]

It would be an inverse piorette (sp) as the angular momentum of the spinning cylinder filled with polymer is tranferred to the disk. You'd probably start out finning real fast and wind up at a lower RPM. I don't think you would want to alter the rotation during the excretion because that would introduce more torque.<br /><br />This does however, give me a new idea inspired by the recent work producing nano-scale fly eyes.<br /><br />LINK.<br /><br />There isn't much detail in that link, but the tech involved UV cured polymer in which optical waveguides formed naturally by UV light penetrating the material. The UV cured state has different optical properties than the uncured material and thus channel the UV light deeper into the material, thereby increading the size of the optical waveguide. In the case of the artificial insect eye, the uncurred material was rinsed away with a solvent leaving only the waveguides and perfect natureally formed lenses.<br /><br />Ok, so what? I'm thinking that the right kind of material might have some interesting optical properties. It would be a dense mesh of optical waveguides bonded together. UV striking the top of the disk would be efficiently transported to the back of the disk through the nano-waveguides. Now turn the disk into a sphere by inflating two edge-joined disks and you have an giant spherical lens focused at the center of the sphere.<br /><br />Perhaps it is way too ambitous to think of this as an optical quality effect (even for a bulk concentrator) but perhaps the tendency to form waveguides as the material is cured could be used to inttroduce grain into the material or to create an organic semiconductor by exploiting the formation of these directional waveguides and changing the chemistry of the material being spun out. Material A spins out and forms waveguide threads, material B spins out and forms onto the back o

 

[chriscdc]

Hmm, the ability to form an area of constructive intereference at the centre of a large sphere. I suspect that you could do alot of interesting physics with the energies that you could obtain.<br />I've heard that they have used holograms in order to concentrate light onto solar cells instead of mirrors, and that resulted in massive savings. Recent copies of the guiness book of records have examples of having a hologram of a spherical mirror. I have no idea how they can do that. All I managed to ever do was make a hologram of a few chess pieces and a bit of fools gold. The fools gold hologram actually glittered as you moved a light around it, which was excelent, but I still only got a C for art GCSE, damn modern art obsession with shallow ideas.<br /><br />Then there has also been the meta-materials. Which they have modelled the structure that would allow a sphere of the material to become invisible. If topology has taught us anything, it's that any solid shape can be fundamentally reduced to a sphere. So there should be a way to make any solid shape transparent.<br /><br />That was just some random stuff about optics that I've picked up over the years but haven't had an opportunity to mention/gloat on this forum yet.

 

[publiusr]

A bigelow module could be covered with UV activated materials for an instant hard shell. Good.<br /><br />Ares V could launch an independant facility capable of making very large structures.<br /><br />Very good ideas.

 

[rogers_buck]

I'll have to think about this a bit, but perhaps you could spin out first one disk with a doped polymer and then a disk on top of that with a differently doped polymer. The purpose would be to make a large oraganic solar cell. An aluminized coating on the back would reflect sunlight back through the disk to increase power and to act as an electrode. A transparent electrode would be spun out last on the top.<br />

 

[rogers_buck]

Kinda like toasting a marshmellow...<br />

 

[virusxp]

The troubling thing about this IMHO very great idea is that if IMAGINOVA decides to go into space buissiness after some time, they are completely allowed by you (when you registered) to use your ideas posted here in whatever way they find apropriate. Without paying you a dime, of course <img src="/images/icons/laugh.gif" /><br />But otherwise, i like these ideas, seems simply asking for somebody to do the engineering math and pay for the launch <img src="/images/icons/laugh.gif" />

 

[rogers_buck]

Hah, hah. If Lou Dobbs some day can afford a villa nestled on the bluffs of Olympus Mons, then I am happy to donate crack-pot ideas. But then again, I am contractually obligated to surrender all ideas to another party... Humm. No problem theough, I'm rogers_buck the untraceable!!!<br /><br />Actually, this forum constitutes the "public domain". By placing ideas here you are insuring that they cannot be patented, even though the copyright is held by Uplink and yourself for the actual text entered.<br /><br />

 

[virusxp]

Now some other ideas after wondering a while about this.<br />It would be hard to make a perfect disk, a slightly curved would be piece of cake, just like a true hemisphere. Now to take this into another dimension, so to say, what if we instead of one such structure made two at a time. It would be done by tying two such polymer dispensers together by a line. Place them so that both are equally irradiated by sun (its not like with 'head' to the sun as in the original idea, more like 'side' to the sun). Now spin them to start making the traditional structure and to irradiate all sides of it periodically. Finally, the fun part, spin the whole structure also around an axis that is pointing to the sun. In this way, you can accelerate the polymer to move to the ends more quickly, and thus you can make ellipsoids.<br />If spheres are for orbital domes, rooms or whatever, the ellipsoids could very well serve as skyways, literally <img src="/images/icons/laugh.gif" /><br />Also, if you can carefully synchronise the dispensing with the exposure to the sun and stuff, you could even avoid making a full hemiellipsoid, you could just make one side of it (like a shield against micrometeorites or whatever you need it for <img src="/images/icons/laugh.gif" />).