Kayra Posted May 12, 2006 Report Share Posted May 12, 2006 The real issue with getting a mirror to reflect light from the sun down to earth is to keep it in a stable orbit. The design for the collectors I had in mind was an inversed umbrella of stiff cloth. Spun at high speed, it would use centripedal force to hold it's shape, and solar pressure to keep the parabolic form. The edge would have to be studded with many Ion thrusters powered by the sun. These would be used to spin up, sping down, and correct the orbit of the system. Would this work? Quote Link to comment Share on other sites More sharing options...
Jay-qu Posted May 12, 2006 Report Share Posted May 12, 2006 :esmoking: Im first year astro-physics.. it sounds plausible, but would probably need some adjustments to be fully functional and remember that 90% was a just a fair guess. Quote Link to comment Share on other sites More sharing options...
cwes99_03 Posted May 12, 2006 Report Share Posted May 12, 2006 The key to getting low loss is the material you make your reflector out of. You want a reflector that is near perfect for a wide array of frequencies which is a little more difficult than it sounds. Best bet is on some type of composite metallic material. You'd be looking for a material that gives total external reflection (the inverse of what fiber optics do to channel light). Quote Link to comment Share on other sites More sharing options...
Kayra Posted May 12, 2006 Report Share Posted May 12, 2006 The key to getting low loss is the material you make your reflector out of. You want a reflector that is near perfect for a wide array of frequencies which is a little more difficult than it sounds. Best bet is on some type of composite metallic material. You'd be looking for a material that gives total external reflection (the inverse of what fiber optics do to channel light). I was hoping for something in the 99.9% range, which would require a material that could withstand considerable heat. Borrowing from light sail technology and research, I came across this:http://www.space.com/businesstechnology/technology/carbonsail_000302.html It is what actually gave methe idea for this. Quote Link to comment Share on other sites More sharing options...
cwes99_03 Posted May 15, 2006 Report Share Posted May 15, 2006 You're missing the point, the material doesn't have to withstand lots of heat if it is that efficient. It will only get really hot if it is inefficient and even then it won't get hot. Just think of the space shuttle. It doesn't reflect the light efficiently but it doesn't get super hot either just sitting out in space. Am I right? Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted May 15, 2006 Report Share Posted May 15, 2006 Quite right. The main problem is getting the energy down to Earth, if that's where you need it... Quote Link to comment Share on other sites More sharing options...
learnin to learn Posted May 15, 2006 Author Report Share Posted May 15, 2006 how do yall propose getting energy down to earth????? other thatn lasers???? Quote Link to comment Share on other sites More sharing options...
Kayra Posted May 15, 2006 Report Share Posted May 15, 2006 how do yall propose getting energy down to earth????? other thatn lasers????Quite right. The main problem is getting the energy down to Earth, if that's where you need it... If that is the case, take the 30% loss and just use the collected and reflected sunlight directly. It is dead simple, and requires virtually no maintenance in space. The energy does not all have to go to the same place. divide it up and sell to the highest bidder. Let the businesses on the ground figure out the best way to make use of the 0 fuel, massive heat capabilities you can provide. With multiple locations, direct the energy to the locations that are reasonably cloud free.(I suspect most ground businesses would choose locations that have low cloud cover.) I suspect though, that even at 99.9% reflectivity, the smaller collector at earth orbit will likely see energies at 100 * the sun. The space shuttle does have heat dissipation problems, and often has to open the bay doors to give it more area to radiate heat from. Hmm. We will have a massive surface area to use (the backside of the reflector) to radiate heat, so I guess your are correct. Quote Link to comment Share on other sites More sharing options...
ronthepon Posted May 16, 2006 Report Share Posted May 16, 2006 I'll just say it again. Why not package the energy in a concentrated form by putting it into some highly capable batteries?Then send the batteries back in any method, since sending matter is way easier, sometimes, than sending raw and unpackaged energy. Sending, recieving, transporting, using energy will be so simplified!The only unsimple part will be figuring out the truly useful batteries (or energy reservoirs) Quote Link to comment Share on other sites More sharing options...
Jay-qu Posted May 16, 2006 Report Share Posted May 16, 2006 but then you have to transport up and down to and from orbit, if you want to store enough charge so it will be useful for wide scale energy supply then you are going to need a lot of batteries -> large payload = lottsa $$$ this is where that space elevator could be handy! just need to have the collector somewhere up there near the counter weight and a few thousand km of low resistance wires to transmit the electricity directly. Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted May 16, 2006 Report Share Posted May 16, 2006 The space elevator idea is doomed by Coriolis, but it does make far more sense to have a satellite tethered by two widely separated conducting cables and have only the current travelling along them. Using a very high voltage, you have less loss of power. I'm not however sure about feasiblity, those wires would be very long..... even a kiloampère would be dissipating quite a bit of power. Quote Link to comment Share on other sites More sharing options...
ronthepon Posted May 16, 2006 Report Share Posted May 16, 2006 And, such long wires would have a tendency to snap by some minor disturbances (asteroids? spacecrafts incorrectly oriented?) But! If we get some really strong superconductor in the future, I guess that most of the wire would be naturally cooled below critical temperature. We would have to do around ...um... 300-500 km of wire...? Quote Link to comment Share on other sites More sharing options...
Kayra Posted May 16, 2006 Report Share Posted May 16, 2006 Coriolis effect and cable breakage could be mitigated by using a 3 meter wide non-conductive ribbon that is connected as a loop or conveyor belt. If we insist on not beaming the energy directly to the earth, then do not convert it to electricity, but to rotational energy. Apply that directly to the conveyor belt ( no losses in transmission), and convert it at the ground back into electricity by having it turn a generator. (damned big one :confused: ) As a side benefit, any excess heat could be carried away by the same conveyor and radiated into space. Quote Link to comment Share on other sites More sharing options...
ronthepon Posted May 16, 2006 Report Share Posted May 16, 2006 Now that's a very good idea! But how will we rotate the conveyor so fast in the first case? Now... come to thinl of it, won't the sattelite start to spin itself? Well, no, if we add a something big spinning in the opposite direction. This needs some working out.But it's a great concept to start upon anyway... Quote Link to comment Share on other sites More sharing options...
Qfwfq Posted May 16, 2006 Report Share Posted May 16, 2006 We would have to do around ...um... 300-500 km of wire...?:confused:More like, almost 36000 km of wire!!!! I don't see the point of mechanical transmission either, I think the greatest bet would be low electric resistance and high tensile strength. I've been figuring a bit though and it wouldn't be easy, even a kiloohm would be troublesome unless it could be designed for very many megavolts. Quote Link to comment Share on other sites More sharing options...
ronthepon Posted May 16, 2006 Report Share Posted May 16, 2006 :confused:More like, almost 36000 km of wire!!!! I don't see the point of mechanical transmission either, I think the greatest bet would be low electric resistance and high tensile strength. I've been figuring a bit though and it wouldn't be easy, even a kiloohm would be troublesome unless it could be designed for very many megavolts.No no. I mean't we would have to refrigirate 300-500 km of wire, the one left in the atmosphere. By the way, am I right?I happen to be a forgetful chap, when it comes to statistics... Quote Link to comment Share on other sites More sharing options...
Kayra Posted May 16, 2006 Report Share Posted May 16, 2006 I don't see the point of mechanical transmission either He was a proponent of the concept .. (sort of) Ron, there is a really simple design that requires no counter spinning wheel . The point of it was that is was a method that allowed for the transmission of energy with 0 losses, while serving as a method of moving things between space and the ground. Had a rather long thread on this, and covered quite a few of the issues. http://hypography.com/forums/space/5641-another-space-elevator-concept.html Quote Link to comment Share on other sites More sharing options...
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