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From: crad@polari.UUCP (Charles Radley)
Newsgroups: sci.space
Subject: Re: LLNL size and Fred micrograv environment (was LLNL astronaut delivery)
Message-ID: <2721@polari.UUCP>
Date: 13 Nov 90 05:40:34 GMT
References: <9011072124.AA13810@iti.org> <2688@polari.UUCP> <8700@fmeed1.UUCP>
Organization: Seattle Online Public Unix (206) 328-4944
Lines: 73


+Continuous manned presence *is* a problem for microgravity research.
+So is a shifting CG, which moves the experiments into regions of
+greater or lesser tidal force.
+This is not a benefit, it is a liability.  Ask the micrograv
+researchers.  A free-flyer can be tailored to the job, and
+does not suffer from vibration or CG shifts on the station proper.
-
In an ideal sense this is true.  In practice, experiments fail all
the time, and benefit from human intervention to get them going
again.
 
+On a free-flyer, thruster pulses can be scheduled to coincide with
+dead time, furnace re-loads, and so forth.  
-
It is rather the reverse, the experiments will have to be scheduled
around when the burns are required, which will be once or twice per
orbit.
 
+It may mean a delay between the time something breaks and the 
+time it can be fixed, but if something is broken you don't care 
+about giving it a bit of gee, there is no processing to be 
+disturbed.  
-
What about the non-broken expts ?  Or do you only plan on having
one experiment on the free-flyer ?  if you have multiple experiments,
every failure is a complete loss until human operators return.  The 
other experiments will continue.
 
+On a manned platform, you are going to have vibration any time the 
+crew is moving around, which will be much of the time.  There is work
+which cannot be done on a manned platform, and the Fred design
+doesn't allow for it at all.
-
Indeed.   It is a trade off.  NASA considers human presence to be
of benefit, on balance.
 
---------------------------------------------------------------
+And now for the part I find confusing.  This posting brings an
+apparent contradiction into sharp focus, because it holds both
+parts of it in more detail than ever before in this discussion:
-
I am sorry you are confused, I will attempt to clarify.
 
+>What commercial needs ? It puzzles me why people such as yourself 
+>prefer a small station to a big one.
+Here you are apparently saying that the LLNL+ station would be
+smaller than Fred, but then you say...
-
As a space engineer, by "big" I habitually mean "heavy".   Volume
is of little interest to  practical space engineering.   In fact,
large volume lightweight structres have high drag, so are
undesirable.   Better to have a maximum weight to cross section
ratio.   LLNL is "small" in the sense it has less weight, because
it comprises less hardware with less capability.
 
+There you admit that LLNL would have more volume than Fred (and
+thus more room for equipment).  Well, which is it?  Or were you
+talking about Fred in #1, and not LLNL?  If so, I'm sure there
+is an answer to your question.
-- 
If LLNL plans to have more equipment than Freedom, then it must plan 
to be heavier than Freedom, which means it needs more launch flights
than freedom.   
And if it plans to have more equipment than Freedom, then it will be
more expensive than Freedom too.
  I am rather bored by all this interest in the volume of a station,
there are many problems with Freedom, but 
 
"NASA Scientists Admit Serious Volume Problem on Freedom"  
 
is not a headline I recall seeing anywhere.  LLNL would seem to be
spending a lot of effort solving the wrong problem.