From: vince@offshore.ai (Vincent Cate) Newsgroups: sci.space.tech Subject: Re: Rotovator Ideas and Questions References: <9186edb5.0304230613.633ce3cc@posting.google.com> NNTP-Posting-Host: 207.42.133.230 alexterrell@yahoo.com (Alex Terrell) wrote in message > The concept works even better if the up going > mass of Tourist, Colonists, and manufactured products equals the down > coming mass of Tourists, manufactured products and raw materials (such > as platinum, cobalt, etc). Then the whole thing requires no > propulsion. (Even if we don't have expensive metals in the first NEOs, > it would pay us to bring back sand!) With tourists you would expect the same number going up as going down. So this should work out really well. If you grow food in your space hotel you might not have too much one-way traffic once the hotel is built. You can use this two-way traffic trick when sending stuff to the moon by sending regolith back to Earth. No rocket propulsion needed from suborbital Earth to the surface of the moon (except course correction). > However, in the mean time, propulsion is required. Electromagnetic > propulsion requires a straight cable, which is liable to interfere > with the rotating cable. I don't think this is a big problem. You have the wire along your main tether but only thrust when it is angled the right way. So you can not thrust all the time. > Say we used a motor with an exhaust velocity of 60km/s, and we > are providing impulse of 6 km/s to our up going cargo. That means for > every ten tons of cargo, one ton has to be feul. Right. For a tether there is no problem having a huge mass of solar arrays and a bunch of ion-drives thrusting. You just need to store up energy, not accelerate yourself. So mass is not a problem like it would be on a normal space vehicle. So you can use very high exhaust velocity drives. So you need very little reaction mass. > Then we stumble across one of the disadvantages of the rotovator > compared to the hypersonic sky hook. The hardest place for the > rotovator to reach is it's axis. >... > How do you overcome these issues? I think most of the time we will just catch/toss and not go to the axis of a tether. For example, if we are doing two-way traffic between the Earth suborbital and the surface of the Moon (with 2 or 3 tethers) we never need to go to the axis of any tether. I am looking at a tether pickup for a hotel at GEO where the tip speed is slow enough and the tether is short enough that just winching in the tether should work fine. -- 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