Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_5/V13_543.TXT

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Subject: SPACE Digest V13 #543

SPACE Digest                                     Volume 13 : Issue 543

Today's Topics:
              Re: Why the space station?
             Re: LIGO (was Re: IT'S OVER)
           Re: ESO or MIDAS contact address
Re: The Previous Eco-Venus Discussion (was Re: Ethics of Terraforming)
              Re: Why the space station?
Re: Launch Costs XXIV -- Wright Bros. Flyer to carry tanks to Kuwait!

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----------------------------------------------------------------------

Date: 10 May 91 12:28:44 GMT
From: bu.edu!rpi!zaphod.mps.ohio-state.edu!caen![e-mail]  (Ken Sheppardson)
Subject: Re: Why the space station?

[e-mail] (Frank Crary) writes:
>[e-mail] (Ken Sheppardson) writes:
>>
>>  The requirements for carrying out the sort of vehicle processing
>>  tasks we're talking about are on the order of 14 crew and 150 kW.
>>  You also need a place to put the vehicles while you're working on them
>>  (e.g. to provide debris protection in LEO).
>>
>What are these numbers based on? I would think they would be strongly
>dependant on the type of in-orbit construction, and the desired construction
>time.

They are. The numbers given are for steady-state LTV processing rates as
developed by the 90 Day Study -- they may change as a result of the Synthesis
Group recommendations. If you want exact numbers, I'll need to do a little
more digging. (see the list of sources at the end of the post)

Given PMC as the configuration from which we're required to grow, the power
required to handle 'steady state' LTV processing and do the life science work
necessary to support SEI is as follows:

    75.4  kW  Housekeeping
    22.6      Life Sciences
    21.8      Vehicle Processing
    15.6      International Users
     4.9      GLSF/LSE [support equipment]
     3.9      Technology Development (ext)
     1.5      Technology Development (int)
   -----
   145.7  kW  average power necessary during vehicle processing ops

Crew breaks down as follows:

     3.8      Housekeeping
     1.8      Life Sciences
     4.0      Vehicle Processing
     2.0      International Users
     0.1      Technology Development (ext)
     1.9      Technology Development (int)
   -----
    13.6      average crew necessary during vehicle processing ops


So, in nice round numbers, 150 kW, 14 crew.

Sure--things might be different if you wanted to grow Mir, Skylab, ISF...
whatever (e.g, the housekeeping numbers might be reduced significantly), but
right now we're using what we've been given.

>    >[ I said in respect to the cost of launching Mir]
>    >A 5 Titan-launched-size modules is MUCH cheaper than Freedom
>>
>>  Excuse me?
>
>If it requires a longer statement...

Not necessarily. I just want to make sure I understand what a
'5 Titan-launched-size modules' is.

>The Mir space station, which if it
>had been configured for orbital construction would have been on par
>with Freedom PMC, was/will be launched with (excuse me, my number was
>incorrect) 6 modules launched on a Proton SL-13 rocket. The Proton
>places 20 tonnes into low earth orbit. It is therefore on par with the
>US Titan launcher. Therefore, orbiting Mir would cost about the same
>as launching 6 Titans. Freedom PMC will require 17 shuttle filghts.
>6 Proton (or Titan) launches is MUCH cheaper than 17 shuttle flights.

If I understand you correctly, you're saying that we should design a space
station that looks like Mir because it would take X Titan launches instead
of Y shuttle launches, right? I suppose I can't argue with you there. If
we designed a space station which was to be launched by a different vehicle
it would indeed look different. Sure. It would also look different if we
wanted to launch it with Energia, with or without Buran, on Deltas, Scouts...
whatever. It might also look different if an ALS/NLS comes on line. Right
now we're using what we have. I can't imagine congress endorsing anything
else. ("I see Mr. Truly...you want to spend $30 billion on a station, but
first you want to spend $X billion to develop/man-rate a launch vehicle?
What's wrong with Shuttle?" "Well Senator Gore, you see, it will be
cheaper in the long run. It make take more time, but...")

>>  Sure. Are you saying we should never build space structures larger than
>>  some specific dimension? What do you propose as that limit?
>>
>>  One benefit of a design with lots of open space is that you have lots
>>  of open space. Something you need when you want to attach all sorts
>>  of payloads and vehicles.
>
>No, but I think that a space structure should be as compact as possible.

I agree.

>I do not place a great value on expanding Freedom to fill its truss
>structure. By the time we get around to doing this much, Freedom will
>be VERY old. (e.g. well behind the state of the art.) Based on future
>technology and experience gained from Freedom, I feel a second generation
>space station would be more cost effective and usefull than expanding
>Freedom.

Why would a second generation station be more 'cost effective' than expanding
Freedom? Do you know how much expanding Freedom will cost? Do you know how
much a 'second generation' station would cost? The fact that a system or
vehicle is 'well behind the state of the art' is not, in itself, sufficient
to preclude growth of that system. Take, for example, the F-15, F-14, A-6,
any of the Salyuts, Mir (I doubt the Soviets would argue that Mir is 'state
of the art')...I'm sure others can provide more examples.

>                                 Frank Crary
>                                 UC Berkeley

-------------------------------------------------------------------------------

Just in case anyone asks, here are the sources for the power/crew requirements
I quoted at the beginning:

  "Space Station Freedom Space Exploration Initiative Accommodations - POP 91-1
   Submit" April 1991

  "Evolution Requirements Descoping for the Restructured Space Station Freedom
   Program", Barry Meredith (LaRC SSF APO), SSF Evolution Working Group
   Meeting, Reston VA, April 4-5 1991

  - NASA HQ user representatives-supplied traffic models

    Office of Space Science and Applications (OSSA, 11/90)
    Office of Aeronautics, Exploration, and Technology (OAET, 6/90)
    Office of Commercial Programs (OCP, 6/90)

  - Level II Date

    User Mission Data Base, Rev 4.2 (9/25/90)
    SSFP Utilization Sequence Databook (10/90)
    CR# BM010173A, Laboratory Support Equipment Addback

  - International MOUs

  - NASA 90 Day Study on Human Exploration of Moon and Mars

    OSSA Inputs on life sciences requirements
    MSFC vehicle concepts/requirements
    KSC vehicle processing analysis
    Final Report (11/89)


===============================================================================
 Ken Sheppardson                                  Email: [e-mail]
 Space Station Freedom Advanced Programs Office   Phone: [phone]
 NASA Langley Research Center, Hampton VA         FAX:   [phone]
===============================================================================

------------------------------

Date: 10 May 91 00:17:56 GMT
From: theory.tn.cornell.edu![e-mail]  (Lee Samuel Finn)
Subject: Re: LIGO (was Re: IT'S OVER)

In article <[e-mail]> [e-mail] (Norman J. Meluch) writes:
>
>My question was about the effectiveness of LIGO to detect these waves.
>
. . .
>
>First some background...
>
>Basically the description of LIGO given (please correct me if I'm wrong)
>was that you had to long pieces of matter (poles) arranged at right angles.
>Along with these poles you set up a laser (via a beam splitter) to shine
>down the axis of both poles.  Mirrors (I assume attached to the ends of the
>poles) then reflected the laser beams back toward the beam splitter again
>where the light signal was recombined.

There is a confusion here between two different types of gravitational
wave detectors. In an interferometric (or ``beam'') detector, such as
LIGO, there is no pole or other rigid object. The mirrors are attached
to masses that are suspended so as to act essentially as free masses.
What is meant by ``free masses?'' Here what is meant is that, under
the action of small, transverse (to the pendulumn suspension of the
mass) forces, the fact that the mass is suspended on a pendulumn, or
is otherwise constrained, is insignificant. In LIGO this is acheived
by having the masses suspended as pendulumn with periods on order 1
second. Consequently, small periodic forces with frequencies much
greater than 1 Hz do not sense the pendulumn suspension.

[Illustration deleted]
>
>Now it is assumed (or theorized I suppose) that a gravity wave will manifest
>itsself as a compressional phenomena in the space of one of the poles
>(ie along one of the axis) but not the other.  Thus, one pole will change
>length, and the other will remain constant.  This will, in turn, produce a
>small phase difference in the light at the recombination point, and the gravity
>wave will have been detected.

Another clarification is in order. If the gravitational wave (of the
correct polarization) is propagating perpendicular to the plane of the
detector (which is the direction for which the detector is most
sensitive), then during one half period the lenght of one arm will
decrease and the length of the second arm will increase. During the
next half period this process will reverse itself. The gravitational
wave is manifest as a shift in the fringe (as you have described).
The lengths of both arms change, in concert but in exactly the
opposite sense.

>
>Now for my question (and it's really hard to put this into words so
>bear with me):
>
>Since light used for this experiment is travelling through the same physical
>space as that which the pole (or whatever) exists in, won't it be as
>much effected by the gravity wave as the pole?
>
>I mean, think of the light like a slinky.  It has a certain # of waves
>over a certain distance.  But since the space that the light exists in
>is "compressed" by this gravity wave, won't the light just "compress"
>along with it? (ie have more wavelengths in a smaller "space").
>
>Or have I just missed the point here (and my mind is too rooted to real
>world analogy (which could very well be :-))?

The question you ask is a good one. Experts who wish to review the
calculations can find them in Misner, Thorne, and Wheeler. You can do
the calculation in several different ways: all will get you the same
answer, and all boil down to calculating the round trip travel time
(or the round trip distance travelled) for a photon as it transverses
the arms of the detector. The change in separation of the test masses
at the end of the arms is a cumulative effect of the passing
gravitational wave over some fraction of its period, and not a local
effect on a photon. It is manifest as an actual change in the physical
separation of the masses, and is not a confusion of moving
coordinates.

>
>                        - Norm.
>--
>|~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Norman J. Meluch ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~|
>| Mail: [e-mail]           Fax:[phone]  Voice:[phone] |
>| Note: The opinions expressed here are in no way to be confused with valid   |
>|_______ideas or corporate policy.____________________________________________|

------------------------------

Date: 10 May 91 16:10:56 GMT
From: mcsun!ukc!icdoc!syma![e-mail]  (Philip Taylor)
Subject: Re: ESO or MIDAS contact address

Perhaps it is not widely known, but an email guide to ~7000 astronomers
worldwide is available from here (Royal Greenwich Observatory, Cambridge).
For a copy, email a request to [e-mail]-star


Philip Taylor
Software Engineering Group, Royal Greenwich Observatory, Madingley Road,
CAMBRIDGE, England. CB3 0EZ.

JANET : [e-mail]

------------------------------

Date: 10 May 91 11:46:32 GMT
From: munnari.oz.au!metro!cluster![e-mail]  (Andrew Taylor)
Subject: Re: The Previous Eco-Venus Discussion (was Re: Ethics of Terraforming)

In article <[e-mail]>, [e-mail]
(Ken Sheppardson) writes:
>    ...I haven't read the articles yet, but I look forward to seeing what
> you'all concluded. I won't waste anymore bandwidth until I've done so.

One comment, you should be aware that Henry Spencer's articles in that
collection are well below his usual high standard. For example, he writes:

> There's nothing "record" about the current numbers of extinctions.  Nice,
> kind old Mother Nature has thrown far more species into the fire than we
> ever have.  When I said "greatest ecological disaster", I meant it:  maybe
> 99% of all species then alive on Earth died of oxygen poisoning immediately
> after photosynthesis appeared.  Even the Cretaceous-Tertiary event makes our
> unfortunate recent record look like Mother Teresa's.

I believe E.O Wilson estimates tropical deforestation is currently causing
20,000 extinctions/year and will result in the extinction of 25% of all species
by early next century. Although, in relative terms, this is not as bad as the
75% estimated for the Cretaceous-Tertiary extinction, it is likely to be a
record for total number of extinctions. The increase in species diversity with
the rise of the angiosperms means there are far more species now.

From the perspective of a small forest animal our deforestation would appear
as cataclysmic as some of the proposed C-T extinction scenarios do to us.
I don't think Mother Teresa would appreciate Henry's comparison.

An oxygen-triggered extinction doesn't appear in the biology texts I've seen.
There is little evidence from the times when photosynthesis appeared so
speculation can run unfettered. However all of the models I've seen for oxygen
in the prehistoric atmosphere have it rising very slowly. Significant change
taking 100 millions or billions of years. At this rate the resulting
extinctions, if any, would barely be noticable above the background level.

Andrew Taylor

------------------------------

Date: 11 May 91 21:29:05 GMT
From: agate!tornado.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: Why the space station?

In article <[e-mail]> [e-mail] (Ken Sheppardson) writes:

>If I understand you correctly, you're saying that we should design a space
>station that looks like Mir because it would take X Titan launches instead
>of Y shuttle launches, right? I suppose I can't argue with you there. If

    There are vaild reasons to question the whole truss-layout concept,
number one being still-unanswered (as far as I've seen in trade press)
questions about the repair EVA efforts.

    Another problem with Freedom is the 'station per pound' tradeoff.
We're going to fly 17 shuttle missions to lift and assemble Freedom, and at
25 tons each this is about 425 tons-equivalent to orbit.  If instead we
were to build it in a plug-cans-together manner (no truss, etc) we could
very likely get the same capability for a lot less weight to orbit.  I.E.
5 to 10 Titan launches (100-200 tons).  This is the approach that MIR was
built under.

    Freedom's design concept just hasn't been demonstrated to be
effecient.  If we're not planning to put microgravity experiments on it and
if we can't afford to expand it then there's no need for the truss, which is
going to cost us how much?  Can we build/resupply/refurbish lunar or martian
transver vehicles with Freedom? yes.  Can we do it with a can-based Mir-oid
station? yes.  Which would be cheaper?  Probably not Freedom.

[If someone in the Freedom team would like to change my mind, please do.
Source material that indicates Freedom will be more effecient than possible
alternatives would be particularly appreciated, if it exists.]


  == George William Herbert ==   *   JOAT = Jack Of All Trades = Generalist   *
 == JOAT for Hire: Anything, ==  #########  I do Naval Architecture, ##########
===+++ Anywhere, my price +++=== # Spacecraft Design, UNIX Systems Consulting #
 ==   [e-mail]   ==  # RPG writing/development, and lots of other #
  ==   [e-mail]   ==   ## random stuff, of course.  I'm a JOAT 8-) ##

------------------------------

Date: 30 Apr 91 17:56:32 GMT
From: unisoft!hoptoad!pacbell!pacbell.com!mips!sdd.hp.com!wuarchive!rex!rouge![e-mail]  (Fraering Philip)
Subject: Re: Launch Costs XXIV -- Wright Bros. Flyer to carry tanks to Kuwait!

In article <[e-mail]> [e-mail] (Nick Szabo) writes:

>I agree with the general gist of your comments, that going towards high
>up-front cost, heavier lift vehicles is harmful, not helpful, to developing
>new technology.  IMHO, if an organization can greatly lower development
>costs (eg <$500 million for GEO satcom carrying launcher) _and_ cut
>operation cost by a large factor, then it would be worthwhile to build.
>If we want to cut costs we need to cut costs, not propose yet more $billions
>in the name of cutting costs.  It is well nigh impossible that government
>could do such a thing, much less want to do such a thing.  If industry wants
>to spend their own money on such a project, I'm every bit in favor of that.
>Meanwhile, government should concentrate on advancing the state of the
>art, not developing and operating chemical rockets.

I finally see what you mean. Especially with the raging argument going
on about whether or not the government should build a booster to
launch 100,000 pound payloads or 600,000 pound payloads.

--
Phil Fraering
[e-mail]
Joke going around: "How many country music singers does it take to
change a light bulb? Four. One to change the bulb, and three to sing
about the old one."

------------------------------

End of SPACE Digest V13 #543
*******************