From: fcrary@ucsu.Colorado.EDU (Frank Crary)
Newsgroups: sci.space
Subject: Re: what use is Freedom?
Date: 7 Oct 92 01:54:44 GMT
Organization: University of Colorado, Boulder

In article <Cohena-051092150616@l30346.mdc.com> Cohena@mdc.com (Andy Cohen) writes:
>> Actually, Mir (once it is fully expanded) will be roughly the same
>> size as Freedom, with five full-sized modules (about the size of the
>> Japanese and European Freedom modules, and larger than the now-scaled-down
>> American modules) and one half-sized module, slightly larger than the
>> Freedom nodes.

>Perhaps....however, how many watts does Mir provide?  I've heard it is not
>much...certainly not enough for the same number of racks and EVA/IVA
>equipment SSF will have... 

Soviet EVA proceedures don't use all that much power... But currently
Mir should have around 50 kW of power. However, it isn't fully
expanded: It's still got two expansion modules to go. Fully expanded,
I'd guess it would be in the 75kW range.

>...We have also
>learned that Mir has regular power blackouts lasting around 15 minutes or
>so....real fun...

I don't know about blackouts, but they do have occasional power problems.
That's the disadvantage of lacking a truss: They have a limited amount
of solar pannels and problems with one casting shadows on the other.
The question is, is all the effort of the truss structure really
worth it?

>> "Large"? The cupola mock up I saw was around 1.5 to 2m across. Admittedly, this
>> is enough room to put in a treadmill and jog with a _increadble_ view, but
>> its hardly a "large area."

>As far as elbow room IN the cupola itself..it'll be very tight...
>...I was actually
>refering to the space from the node up into the cupola... Did you look up
>inside the mockup of Node 2 or the mockup of the cupola by itself? 

In the cupola mockup itself, but none of the nodes looked like they
had alot of room, either...

>> I'm sorry, but this is totally incorrect: These [truss] structures are _not_
>> necessary. They are necessary if you want an easily expanded station,
>> or if you want to get the highest possible effeciency out of the solar
>> panels. But if you simply want to power the living spaces and experiments,
>> and radiate away the watse heat, you do _not_ need all that structure.

>Sigh... Where'd you get that from? 

The early 80s studies, before the truss configuration was decided on.
(Not that these studies were suffiecient, in my opinion, but they 
raised _some_ relevant trade offs.)

> Measure the width of the radiators and
>the space between the modules and the rotary joints.... There is just
>enough clearance...  

There isn't enough clearance _if_ you want to get full efficiency 
out of the components. Less efficient but more compact arrangements
are possible. The question becomes a trade off between small size
(and thereby ease of construction) and system effeciency (and thereby
system mass). I think the Freedom design is at one extreme.

>Also...I guess you could make the truss smaller...but then the solar panels
>(which are also at the bare minimum for the minimum power reqs) would block
>essential antennas as well as have unnacceptable rotational limits...

Again, it's a trade off between making life difficult, by having the
systems interfere with each other, or having a more compact design. 
Freedom is trying to be a design where each part works at peak 
efficiency, without interfereing with anything else. I think such
a design isn't too realistic and definitely not cost effective.
(Though from the sound of it, this is mostly the result of unreasonable
design requirements, rather than the design itself...)

                                              Frank Crary
                                              CU Boulder
Newsgroups: sci.space