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From: 3001crad@ucsbuxa.ucsb.edu (Charles Frank Radley)
Newsgroups: sci.space
Subject: Re: LNLL Inflatable Stations
Message-ID: <7154@hub.ucsb.edu>
Date: 12 Nov 90 18:52:10 GMT
References: <1221@iceman.jcu.oz> <9011081333.AA24041@iti.org>
Sender: news@hub.ucsb.edu
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Since LLNL is a large lightweight structure it will be subject to high drag, 
compared with, say Freedom.  This means more reboosting, more propellant  
 (already a problem on Freedom), and higher engine duty cycles. Is there any 
 way they can make it smaller ?
There are practical problems with spinning a station.   Need to despin every
time EVA is needed, expensive on propellant/power.   Structure must carry
centrifugal loads, makes it heavier.    Reboost thrusters must be gimballed,
Freedom is gravity gradient stabilised, so reboost thrusters always point in
the right direction, 3-axis (non-spinning) control allows direction to be fine
tuned.   In practice the station will need a spun section attached to a despun
section.   Crew transfer between the two is tricky.  EVA transfer hazardous.
And designing a leak-free IVA tunnel with slip rings and airtight bearings is
at least a few hundred $M.   Plus lots of lost sleep worrying about when the
thing will seize or rupture, sometime it WILL do one or the other, or both.