From: Vincent Cate (vince@offshore.ai)
Subject: Re: Mars Colonization 
View: Complete Thread (45 articles)  
Original Format 
Newsgroups: sci.space.policy
Date: 2004-01-02 03:41:47 PST 
 

"Paul F. Dietz" <dietz@dls.net>:
> You're assuming 1/6 gee (O'Neill colonies were 1 gee), you use
> water for shielding (O'Neill colonies use lunar or asteroid waste
> materials, which not be so rich in hydrogen and so will be less
> effective per unit mass at particle radiation), you're using a high
> tech material (spectra) as your load bearing element, and you're
> going along with a higher radiation load than the original space
> colonies were designed for.

Thanks.

> OTOH, I don't know why you're using 20 km of tether.  At 1 rpm,
> you get 1/6 gee at r ~ 160 m.  The mass of tether required goes
> up in proportion to the radius for a fixed centripetal acceleration
> (as long as tether mass is small compared to the end masses.)

True.  I am extending tethers from either hotel to catch/toss
human payloads on a Geo-transfer orbit.  This is a higher
delta-V.  I need a low rpm so that I can get low G loading on 
the humans with this extended tether.  

The other way to say it is my V^2/R has the same RPM but a 
higher V, so I need to be able to have a big R.  Since
V2/R2 = V1/R1 (same rpm) the original R1 needs to be large too.

  -- Vince