Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_3/V11_329.TXT

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Subject: SPACE Digest V11 #329

SPACE Digest                                     Volume 11 : Issue 329

Today's Topics:
              Re: Decompression and 2001
              Re: Fermi paradox
            Re: Rename the Earth?
     Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...)
           Re: Space Station Distribution Frequency
              Re: Math/Science Education
           Payload Status for 04/27/90 (Forwarded)
              Re: Re: Rename the Earth?
----------------------------------------------------------------------

Date: 21 Apr 90 00:53:23 GMT
From: news-server.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Decompression and 2001

In article <[e-mail]> [e-mail] (Blake Philip Wood) writes:
> In being exposed to a vacuum
>you certainly wouldn't want to simply open your mouth, because with no
>air in your lungs you have only about 15 sec of consciousness.
>
   I'd be surprised if this were the case for a person who was prepared
for vacuum. Animal tests put the limit at about 15 to 30 seconds, but
you can't tell a rat to hyperventilate.
   When I read the space rescue scene in _Earthlight_ I just had to try
the described procedure myself. I had no trouble at all holding my
breath for five minutes. Since I can't manage more than a minute and a
half when I haven't prepared for it, surely preparation for vacuum can
extend the conscious period by a factor of two or three.
   BTW, the "preparation" is to hyperventilate almost to the point of
fainting, and Arthur C. Clarke recommends throwing one's arms back
during the inhalation to increase lung filling.

>                 Blake P. Wood - [e-mail]
>                 Plasmas and Non-Linear Dynamics, U.C. Berkeley, EECS


--
 Christopher Neufeld....Just a graduate student  | "Like most
 [e-mail]              | intellectuals he is
 [e-mail]          Ad astra! | intensely stupid."
 "Don't edit reality for the sake of simplicity" |  Marquise de Merteuil

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

Date: 27 Apr 90 03:27:21 GMT
From: crdgw1!sixhub![e-mail]  (Wm E. Davidsen Jr)
Subject: Re: Fermi paradox

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

Date: 27 Apr 90 01:57:11 GMT
From: usc!cs.utexas.edu!mailrus!accuvax.nwu.edu!delta.eecs.nwu.edu![e-mail]  (Serafim Efstratiadis)
Subject: Re: Rename the Earth?

So you wnat to rename the "Earth"? Very simple.
Call it "Gea", its ancient Greek name.
I can not think of a better name since you already use it, for example,
in the word: geology = the study of this planet.
(don't get confused with "geo-" instead of "gea-"; it's the Greek grammar!)

Regards, Serafim.

------------------------------------------------------------------------------
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       The Technological Institute, Evanston, IL 60208-3118, [phone]
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------------------------------

Date: 25 Apr 90 15:32:02 GMT
From: van-bc!rsoft!mindlink![e-mail]  (Bruce Dunn)
Subject: Re: PegBlimp (was Re: Pegasus launch from Valkyrie (or ...)


     The velocity imparted by launching Pegasus from a moving airplane and the
reduction in air drag by launching at altitude are not the only reasons for air
launching.  Another major cause of increased payloads is that rockets have a
higher exhaust velocity in a vacuum than in air, and launching above much of
the earth's atmosphere gives a substantial performance improvement to the first
stage.
--
Bruce Dunn   Vancouver, Canada    [e-mail]

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

Date: 27 Apr 90 09:57:02 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Space Station Distribution Frequency

I got this in mail (STRANGE indecipherable NASAmail header!) from Dave
McKissock and am not sure whether he meant to reply or followup to the
article, but the content looks like a followup and my attempt to reply
bounced, so here goes.  I apologize if it ends up being a duplication.

--- forwarded message

From: uunet!gemini.arc.nasa.gov!/C=USA/ADMD=TELEMAIL/PRMD=RESTON.SSFP/O=tmis/OU=8510/S=McKissock/
Date: Fri, 27 Apr 90 06:49 PDT
Message-Id: <NJJA-1521-9097/20@nasamail>
        FN:David,I:B,G:1)

Well, somebody actually read my posting! I'll try to answer your
questions (as I said in my posting, I am an Mechanical Engineer, so I'm
really winging it on some of this stuff)...

"Maximize Control Response"  - I believe the desire is to maximize the
response of the electrical power system (EPS) to changes in loads &
faults. For example, if a load on the EPS were to short out, you would
not want that fault to "backup" through the entire EPS & cause damage to
many EPS components. You would want an EPS box that is close to the load
to recognize that a fault exists & isolate the load (i.e. turn off the
power to the load). I believe, from my conversations with the EE's
around here, that the higher the frequency, the quicker the EPS can
respond to fault conditions.

"Minimize Mass" - I'll quote some numbers from a TRW Phase B report on
their Distribution Trade Study... (while were at it let's throw in cost
& end-to-end efficiency)

              20 kHz    400 Hz, 3 Phase     200 Vdc    440 Vdc

Mass          10,076       14,263           14,708     11,347
(lbs)

Delta from
20 kHz          0.0          4,187           4,632      1,271

---------------------------------------------------------------
Cost ($M)     1034           1140            1046       1070

Delta from
20 kHz         0.0           +106             +12        +36
---------------------------------------------------------------
Efficiency
(%)             87.1          88.0            85.1       87.8

"Delivery of energy under fault conditions" - Again, I'll quote from the
TRW study "With regard to the safety issue, 20 kHz power distribution
has the advantage against competing approaches in presenting minimal
half-cycle energy and higher values of let-go current" (I believe let-go
current is just what it sounds like, if you grabbed an uninsulated
cable, the let-go current is the most current you handle & still be able
to "let-go" of the cable. So the higher the number the better. A picture
in the report clarifies the issue (y-axis is let-go current, milli-Amps,
top curve is dangerous current, bottom curve is let-go threshold):

80    |                                                      *
      |
      |                                                      +
60    |
      |
      |
40    |    *
      |                                       *
      |    +      *            *
20    |                                       +
      |           +            +
      |
0     ----------------------------------------------------------------
      1           10           100           1000            10000

                          Frequency, Hz

Soo, the point of the Figure is that the higher the frequency, the
higher the dangerous current values & the higher the let-go threshold,
which is good.  To continue with the quote from the TRW report "Half
cycle energy values are 31.25 joules and 0.625 joule, respectively, in
400 Hz and 20 kHz systems while let-go current is approximately 40 mA in
a high voltage dc system, 80 mA or more for a 20 kHz system and
approximately 20 mA in a 400 Hz system.

Another point raised by Mr. Spencer in his original posting was that
there was vast experience with 400 Hz in the aircraft industry. TRW also
commented on that... (my editorial comments on the report are in
parenthesis like this sentence is)...  "Technical Readiness. The
technical status of each option was reviewed and the findings point to a
more mature system technology base in dc and 400 Hz systems but from the
component technology status viewpoint, 20 kHz and 400 Hz options are
essentially equivalent. (So 20 kHz loses in the "system" technology area
but is even in the component technology)

Breadboard 20 kHz equipment has been built and tested at power levels up
to 25 kW. Both switchgear and transmission lines are currently under
development.

There is strong 400 Hz heritage derived from military and commercial
aircraft and submarine programs. System characteristics are well
understood but new power equipment would have to be designed and
packages for space applications.  (So althouth there is lots of
experience with 400 Hz in ground applications, there isn't lots of
flight qualified 400 Hz equipment lying around waiting to be used. So we
would have to pay the development costs of 400 Hz hardware).

A high voltage breadboard dc test bed effort is under way at NASA/MSFC.
Switchgear designs have been breadboarded and tested by LeRC (200 Vdc to
1200 Vdc) with power levels up to 50 kW (800 Vdc). Power processor
brassboards in the range of 3 to 12 kW have been built and tested with
high voltage inputs on previous ion engine development programs."

In summary, I would say that 20 kHz offered several advantages over 400
Hz and dc systems. 20 kHz presents less of a safety risk for the
astronauts, is roughly the same cost as the other systems (some studies,
like the one quoted above showed 20 kHz to be the least expensive, other
studies showed slight advantages to 400 Hz or dc), weighs less than
other systems, and has faster controls for quicker responses to faults
in the power system.

Hope this answers your questions about 20 khz

--- end of forwarded message

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

Date: 27 Apr 90 20:13:32 GMT
From: skipper![e-mail]  (Al Bowers)
Subject: Re: Math/Science Education

In article <[e-mail]> [e-mail] ("Michael N. Davis") writes:

>Hold on bucko, I just finished student teaching in math and received a
>math education degree in December and I was well prepared to teach, over
>prepared if you ask me.  For my degree I was required to take 3 courses
>of Calculus, a theoretical course in Algebra (Modern Algebra),
>a theoretical course in Geometry, and a course in Matrices.

Sounds about like what I needed to get my degree in engineering, but
then I also needed differential equations, and advanced engineering
math.  Then they let me do things like physics and statics and
dynamics and...  Well you get the idea.  From what you say it sounds
like you are a one in a thousand, and unfortunately you get painted
with the same brush in generalizations like I do when everyone rags on
NASA.  The point is that we have neglected to teach our kids the
basics and allow them to be motivated.

>My bottom line is that it takes the effort of two people for learning to
>occur, one who is willing to teach and one who is willing to learn.
>If either half doesn't make the effort then learning fails to occur.

That's true, but if you can't motivate them to learn then it really
doesn't matter what you cram into their heads.  Did they end up being
better people for all the work and effort you put in?

>For anyone interested, I have a 360 line journal/flame about my student
>teaching experience for 10 weeks this past fall that I will send upon
>request.  Don't worry I won't send it to the list.

It might be interesting to post a synopsis.

--
Albion H. Bowers  [e-mail] ames!elxsi.dfrf.nasa.gov!bowers

`In the changing of the times, they were like autumn lightning, a
thing out of season, an empty promise of rain that would fall unheeded
on fields already bare.'
                              attributed to Abe Shosaburo by Dave Lowery

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

Date: 27 Apr 90 21:19:00 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Payload Status for 04/27/90 (Forwarded)


    Daily Status/KSC Payload Management and Operations 04-27-90.


    - STS-31R HST (at pad-B) -

    Post launch GSE removal was started Thursday and will be
    completed today.


    - STS-35 ASTRO-1 (at OPF) -

    The payload bay doors were opened Thursday and connector
    safety wiring and BBXRT liquid argon servicing were
    completed.  Today the BBXRT ivt will be performed and the
    hut battery will be removed.


    - STS-40 SLS-1 (at 0&C) -

    Experiment train interface testing continues.


    - STS-42 IML-1 (at O&C) -

    Module pyrell foam replacement, floor staging, and rack
    staging were worked Thursday and will continue today.


    - STS-45 (Atlas-1)-

    Bracket installations were worked Thursday.  Today
    coldplates and the orthogrid will be installed.


    - STS-46 TSS-1 (at O&C) -

    EMP deintegration continues.


    - STS-47 Spacelab-J (at O&C) -

    The light weight rack handling frame fit check is scheduled
    for today.


    - STS-55 SL-D2 (at O&C) -

    Rack 12 staging will continue today.


    - HST M&R (at O&C) -

    ORUC interface testing continues today.

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

Date: Thu, 26 Apr 90 17:20:32 EDT
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Re: Rename the Earth?


>From: cs.utexas.edu!uwm.edu![e-mail]  (Russ Brown)
>Subject: Re: Rename the Earth?

>So instead of standardizing with latin, and having one word for mountain, sea,
>etc., we should force a few hundred thousand students around the world to
>learn four or five equally foreign words?

No, let them learn in the vernacular (their native languages). If they need
to read scientific papers in another language, they should learn the entire
language. There's very little value in looking at a paper and being able to
understand only the place names, except in the very limited case of reading
a map to learn the place names. There's considerable value in Joe Taxpayer
being able to understand that the space probe he paid for has discovered
a mountain, a crater, a plain, etc.

Most other fields of study use different words in different languages, and it
works fine. If you want to translate, just look in one of many multilanguage
dictionaries of technical terms:

ENGLISH      GERMAN       SPANISH      FRENCH       POLISH
-------      ------       -------      ------       ------
copper       Kupfer       cobre        cuivre       miedz
hydrogen     Wasserstoff  hidrogeno    hydrogene    wodor
oxygen       Sauerstuff   oxigeno      oxygene      tlen
silver       Silber       plata        argent       srebo
sulfur       Schwefel     azufre       soufre       siarka

I had to leave out a few accent marks in this example. There was also a Russian
translation, which I couldn't include because it uses the Cyrillic alphabet.
By the way, how do the Soviets refer to places with Latin names? They *can't*
use Latin - their alphabet won't support it. Do they use a phoneticized
version with Cyrillic characters?

As several people pointed out, I had the chronology wrong. I remember hearing
mostly English names as a kid, and should have recalled the history of names
for features on the moon. (The features on Venus, however, are all recently
discovered.)
                   John Roberts
                   [e-mail]

[PS. to match the planet names, Tellus' moon should be named Cynthia. :-) ]

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

End of SPACE Digest V11 #329
*******************