The Tether Connection

[j05h]

This thread is to discuss various tether technologies. I have a few theoreticals to post about, as well as disscussion of existing products. <br /><br />For some background: <br />http://www.tethers.com/TethersGeneral.html<br /><br />Tethers can be used for providing thrust using electrodynamics, be used as structure, provide both drag and electrodynamic deorbit. Some of these features have been demonstrated in space, others at the lab level. What can be done further?<br /><br />One interesting idea I had (and am looking for verification on) would be to create a "magnetic brake" using tethers. This is really theoretical so anyone w/ stronger Physics please sanity-check this. The returning payload to Earth orbit is a small NEO dead-comet, perhaps like Apophis but carbonaceous or cometary. Anchored into it is a network of electrodynamic tethers connected to heat exchangers. A sealed shell of heat-resistant MLI is built under the tether network as the NEO is inbound toward Earth. As the craft enters Earth's magnetic field, the tethers provide "terminator" drag and convert part of that electric current into heat. Ideally the tethers form an integrated structure throughout the NEO, using the same conductive material in a different weave then the external tethers - a passive or throttlable system The first close pass of Earth brakes the object into a highly elliptical orbit and creates a heat mass inside the comet. Subsequent deep passes into the magnetic field continue the melting process. By the time it arrives at EM-L1, it is slagged leaving essentially a muddy lake inside a bubble. If added power is needed to make the break work, it could be a small nuke also inside the NEO, promoting further melting. Once in a useful orbit, the water and minerals are reprocessed into products like pure water and habitat materials (soil, nutrients, some metals). Not a near-term proposal but your thoughts on it?<br /><br /> <div class="Discussion_UserSignature"> <div align="center"><em>We need a first generation of pioneers.</em><br /></div> </div>

 

[nexium]

As you said, not near term. Present tethers can produce perhaps a trillionth of the braking needed to get close to a circular orbit, so we would need a million tethers and a million passes. The asteroid would radiate most of the heat (even with super thermal insulation) between passes.<br />Room temperature super conductors which can tolerate huge magnetic fields would help make your idea useful, but super conductor progress has been very slow in recent decades.<br />It appears that you are constructing the comet nucleus from millions of small peices to get the optimum placement of the individual tethers. What does MLI stand for? Why does the comet need to be dead? Dead comets likely have little water, nor other volitiles. Neil