From: vince@offshore.ai (Vincent Cate) Newsgroups: sci.space.policy Subject: Re: Settle the moon first using tethers References: <9186edb5.0404210736.308d9697@posting.google.com> <409D670B.E41E8F25@earthlink.net> NNTP-Posting-Host: 207.42.133.252 Message-ID: <9186edb5.0405081711.67ac8e7e@posting.google.com> Richard Lamb wrote in message news:<409D670B.E41E8F25@earthlink.net>... > Vincent Cate wrote: > > > > You seem to have overlooked a few minor details I am not sure why you think I overlooked these details. >1) Earth has an atmosphere. Aerodynamic drag comes into the picture. The reusable suborbital rocket deals with the atmosphere but the tether is at orbital altitudes and does not get much drag. It will have some electric thrusters to stay in orbit. >Without an atmosphere, the moon would be an ideal place >to try this contraption. I agree the moon would be an ideal first place to use tethers. I love the idea of sending a probe to orbit the moon and pick up lunar samples while in orbit using a rotating tether. See: http://www.spacetethers.com/cc1.regolith.html >> Note that the space tethers I am talking about can be built >> with existing Spectra-2000 (used for fishing line) and do not >> need any new materials. > >If that statement is true, then based on existing material technology, >you should be able to tell me (order of magniture anyway) >what will this thing weigh (MASS)? > >Which also addresses the cargo/tether mass ratio. > >That's what percentage of the tether mass can be transported. >Ie: how much we can lift in a single package. I can do better than that. I can give you a URL for a graph that shows the relationship: http://spacetethers.com/tethermassratio.gif Also, I have written a tether simulator as a Java applet that will calculate the mass for a tether and simulate it as well at: http://spacetethers.com/spacetethers.html For LEO you might want a tether that is 50 times the mass of the payload. The GEO and Lunar tethers it would be much less (like 3 for Lunar). You also need some ballast, but this is also your solar cells and electric thrusters. We are working with 4,000 Kg payloads in our designs. >> Space tethers also mean that small X-prize type reusable suborbital >> vehicles are probably closer to what we eventually need than the >> big orbital rockets we have now. So they may be the important >> evolutionary path for rockets. Some people have tried to claim >> that X-prize type vehicles are not an evolutionary step toward >> getting to orbit, but with space tethers they really are. You >> need more delta-V, but should be able to grow to the needed speed. > >Maybe, but you skipped a few steps in the equasion... This is just a comment or prediction. Not an equation. To get to a tether you just want a small reusable suborbital rocket. I am really just saying this seems closer to describing an X-prize type vehicle than a big orbital rocket. A reusable first stage on a 2 stage orbital rocket would also be a good fit. The first stage of the Falcon-V looks very good. I am just not sure how reusable it will really be. Anyone know? Also, there is more about tethers on my web site, spacetethers.com. >Since you mentioned it before, I thought it important enough to respond. Thanks! Feedback is part of what makes newsgroups great. >The point I am trying to make is that while the idea may seem "easy" - >it ain't. What parts do you think are the hard parts? It is not so much that I think it is easy, just easier than any other way to get cheap access to space or the moon. -- Vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Vincent Cate Space Tether Enthusiast vince@offshore.ai http://spacetethers.com/ Anguilla, East Caribbean http://offshore.ai/vince ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You have to take life as it happens, but you should try to make it happen the way you want to take it. - German Proverb