Path: utzoo!attcan!uunet!cs.utexas.edu!sdd.hp.com!ucsd!ucbvax!ITI.ORG!aws
From: aws@ITI.ORG ("Allen W. Sherzer")
Newsgroups: sci.space
Subject: Re: LNLL Inflatable Stations
Message-ID: <9011122154.AA02573@iti.org>
Date: 12 Nov 90 21:54:49 GMT
References: <7154@hub.ucsb.edu>
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: Evil Geniuses for a Better Tomorrow
Lines: 62

In article <7154@hub.ucsb.edu>:
>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 included in their budgets. They will use (from memory) 3T a year
of fuel for this. An alternative they are looking at is a 10KW ion engine
which will reduce fuel demand by ~80%.

> (already a problem on Freedom), and higher engine duty cycles. Is there any 
> way they can make it smaller ?

An inflatable station could be made smaller for 0G however if they are
to maintain artificial gravity, it is about as small as they can get. It's
not clear which has more life cycle cost. Crew can be left on a spinning
station for a year with no problems.

An inflatable station used as a Freedom replacement could be smaller and
run at 0G if desired.

>There are practical problems with spinning a station.   Need to despin every
>time EVA is needed, expensive on propellant/power.   

Nope. The airlock module doesn't rotate.

>Structure must carry centrifugal loads, makes it heavier.    

Already calculated (see the ILC Dover report). Stresses are welll within
the strength of the materials used.

>Reboost thrusters must be gimballed,

Or reboost partially whenever the thrusters point the right way. Either
way, this has been considered.

>In practice the station will need a spun section attached to a despun
>section.   

As I said, already in there. The airlock is at 0G.

>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.   

Already included in the cost. This has been anticipated, designed, and
included in weight as well as cost budgets.

>Plus lots of lost sleep worrying about when the
>thing will seize or rupture, sometime it WILL do one or the other, or both.

If it fails, the access ports closes and locks. There may be a slight drop in
pressure in the central core but that would be it. The two ends of the
station would also be out of contact with each other until it was fixed.

There would be no loss of either sleep or life.

  Allen

-- 
+---------------------------------------------------------------------------+
|Allen W. Sherzer| I had a guaranteed military sale with ED-209. Renovation |
|   aws@iti.org  | programs, spare parts for 25 years. Who cares if it      |
|                | works or not?  - Dick Jones, VP OCP Security Concepts    |