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Subject: SPACE Digest V12 #593

SPACE Digest                                     Volume 12 : Issue 593

Today's Topics:
              Re: Save our Shuttle data?
    NASA to use world's fastest supercomputer (Forwarded)
           Light bulbs, thorium, space applications
          Re: NASA Prediction Bulletin Distribution
           Re: Commercial Shuttle Proposals
          Re: NASA Prediction Bulletin Distribution
              Re: Photon engine
          Re: NASA Prediction Bulletin Distribution

Administrivia:

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

Date: Sat, 24 Nov 90 00:19:38 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Save our Shuttle data?


>From: van-bc!rsoft!mindlink![e-mail]  (Bruce Dunn)
>Subject: Re: Save our Shuttle data?

>> [e-mail] (Doug Mohney) writes:
>> [regarding the difficulties in reviving the F1 LOX/Hydrocarbon engine]
>> Pretty bizarre to think we've come 20 years, with CAD/CAE and materials
>> engineering and we can't build something which was put together in the '60s.
>> Kinda scary.

>     However, there are other examples of the difficulties in replicating old
>technology.  Old does not mean non-sophisticated.  We are still struggling to
>reproduce the playing qualities of centuries-old violins.
>...There is often a lot more art in engineering
>than the textbooks would indicate.

>Bruce Dunn   Vancouver, Canada    [e-mail]

It has been implied recently that much of the credit for the quality of Mr.
Stradivari's violins is due to the properties of the materials he had
available to him. In particular, the logs that were to be made into the
wood for the violins were floated in the harbor for delivery, altering their
composition and causing them to be impregnated with various substances, and
the varnishes used at the time often contained gem dust, which got into the
grain of the wood and increased stiffness, thus altering the modes of
vibration.

Whether or not these particular features turn out in the long run to be
relevant, the point is that many details of this type may not have been
under the control of or within the knowledge of Mr. Stradivari, so that
even if he had wished to reveal his violin-making formula to the world,
in order to work it would have to specify particular products of particular
dealers, and if any of these went out of business or changed fabrication
techniques, it might not have been possible to find suitable substitutes.
All of this is in addition to any peculiarities of fabrication Stradivari
may have consciously or unconsciously employed.

I think Bruce has found a very good analogy to the problem of reverse
engineering launcher systems. That too is a materials problem, with emphasis
both on the specific materials selected, and the exact nature of their
treatment during fabrication, with loss of information at each interface
between "contractor" and "subcontractor".

As far as the SSME's are concerned, I think they show that with extraordinary
care, design with very tight tolerances and margins is possible but not
necessarily economical. I suspect, however, that much of their design will
be applicable to future systems, particularly as the qualities of available
materials continue to improve.
            John Roberts
            [e-mail]

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

Date: 22 Nov 90 04:36:44 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: NASA to use world's fastest supercomputer (Forwarded)

Sarah Keegan                                    November 14, 1990
Headquarters, Washington, D.C.
(Phone:  [phone])


RELEASE:  90-151

NASA TO USE WORLD'S FASTEST SUPERCOMPUTER


     NASA researchers will have access to the world's fastest
supercomputer as a member of the Concurrent Supercomputing
Consortium, a newly-formed group of the nation's premier research
organizations.

     Consortium members will be able to access Intel
Corporation's Touchstone DELTA supercomputer system, slated for
installation at the California Institute of Technology (Caltech),
Pasadena, Calif., next spring.  The DELTA system has a peak speed
of 32 billion floating point operations per second, making it the
world's fastest computer.

     The consortium will tackle some of today's most demanding
computational and scientific challenges, such as global climate
modeling, space science data analysis and pattern recognition of
DNA sequences in the human genetic makeup.

     NASA will use the DELTA system as part of the agency's High-
Performance Computing Initiative (HPCI), an ambitious program to
accelerate the computing research capabilities required to
maintain U.S. aeronautical and space science leadership in the
21st century.  For example, DELTA will dramatically improve
NASA's capability to simulate the performance of integrated
aerospace vehicle systems throughout their flight regimes and
mission profiles and will greatly enhance multidisciplinary
research in global climate change and astrophysics.

     NASA will begin to use the DELTA system for research soon
after it becomes available at Caltech.  In addition, NASA
researchers working on HPCI also will evaluate how much of an
increase in computational performance DELTA offers over the
agency's present systems.

     Lee B. Holcomb, Director of the Information Sciences and
Human Factors Division in NASA's Office of Aeronautics,
Exploration and Technology (OAET), is the agency's representative
on the Concurrent Supercomputing Consortium's Policy Board.  The
board is headed by Caltech astronomer Thomas A. Prince.  Paul
Messina, also of Caltech, is Executive Director of the
Consortium.

     Other members of the consortium are Argonne National
Laboratory, Argonne, Ill.; California Institute of Technology;
NASA's Jet Propulsion Laboratory, Pasadena, Calif.; Center for
Research in Parallel Computation (lead center, Rice University,
Houston); Defense Advanced Research Projects Agency, Arlington,
Va.; Intel Corporation's Supercomputer Systems Division,
Beaverton, Ore.; National Science Foundation, Washington, D.C.;
Pacific Northwest Laboratory, Richland, Wash.; Lawrence Livermore
National Laboratory, Berkeley, Calif.; Los Alamos National
Laboratory, Los Alamos, N. Mex.; Oak Ridge National Laboratory,
Oak Ridge, Tenn.; Purdue University, West Lafayette, Ind. and
Sandia National Laboratories, Albuquerque, N. Mex.

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

Date: Fri, 23 Nov 90 17:19:13 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Light bulbs, thorium, space applications


>From: solo!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!julius.cs.uiuc.edu!ux1.cso.uiuc.edu!aries![e-mail]  (Doug McDonald)
>Subject: Re: The great light bulb debate

>In article <[e-mail]> [e-mail] (John Roberts) writes:
>>The mantles for gas lanterns are made with radioactive thorium oxide
>>(presumably because of its mechanical properties at high temperatures).
>>A reference book I have also states that it is included in trace quantities
>>in the tungsten filaments of light bulbs (!).

>Very very doubtful in light bulbs. It IS used in the filaments of
>certain vacuum tubes: the thorium migrates to the surface and coats the
>tungsten, producing a material with a lower work function, and hence
>it emits electrons at lower temperatures. The treatment of the material
>to get this to work is somewhat of a black art - I spent quite
>a bit of my graduate career playing with various potions and
>incantations over this stuff. Once you get it right, though, it works very
>well.

>Doug McDonald

Since it looks as though thorium is potentially useful for space applications,
I thought it would be worthwhile to post a few lines from the CRC Handbook of
Chemistry and Physics (1990-91 edition, pp 4-33 to 4-44):

"Thorium is now thought to be about three times as abundant as uranium and
about as abundant as lead or molybdenum. The metal is a source of nuclear
power. There is probably more energy available for use from thorium in the
minerals of the earth's crust than from both uranium and fossil fuels
[combined].
...Thorium oxide has a melting point of 3300C, which is the highest of all
oxides. Only a few elements, such as tungsten, and a few compounds, such as
tantalum carbide, have higher melting points.
...The principal use of thorium has been in the preparation of the Welsbach
mantle, used for portable gas lights. These mantles, consisting of thorium
oxide with about 1% cerium oxide and other ingredients, glow with a dazzling
light when heated in a gas flame. Thorium is an important alloying element in
magnesium, imparting high strength and creep resistance at elevated
temperatures. Because thorium has a low work-function and high electron
emission, it is used to coat tungsten wire used in electronic equipment.
The oxide is also used to control the grain size of tungsten used for electric
------------------------------------------------------------------------------
lamps; it is also used for high-temperature laboratory crucibles.
-----
[Also used to make glass with high index of refraction for lenses, etc.]
...(232)Th occurs naturally and has a half-life of 1.4E10 years. It is an
alpha emitter. (232)Th goes through six alpha and four beta decay steps
before becoming the stable isotope (208)Pb. (232)Th is sufficiently radioactive
to expose a photographic plate in a few hours. Thorium disintegrates with the
production of thoron (radon(220)), which is an alpha emitter and presents a
radiation hazard. Good ventilation of areas where thorium is stored or
handled is therefore essential."

Moral: on long camping trips, don't store your spare mantles along with your
camera film. :-)

Incidentally, upon further research, incandescent bulbs were filled with
nitrogen rather than vacuum starting in 1913, and later various mixes of
nitrogen and argon were employed. (Encyclopaedia Britannica, 1990)
       John Roberts
       [e-mail]

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

Date: 22 Nov 90 14:51:00 GMT
From: rex!samsung!usc!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!news.funet.fi!hydra!hylka![e-mail]
Subject: Re: NASA Prediction Bulletin Distribution



   It would be very nice, if the NASA Prediction Bulletins
   will be available from some anonymous-ftp site.  I have
   just asked  in  newsgroup sci.astro, if the predictions
   already are in some file archive, but I haven't got any
   positive answer yet.



        Veikko Makela
        --------------------------------------
        [e-mail]
        [e-mail]
        --------------------------------------

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

Date: 23 Nov 90 17:19:25 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Commercial Shuttle Proposals

In article <[e-mail]> [e-mail] (Wales Larrison) writes:
>HS>Well, the obvious reason [why this can't be done] is "because
>HS>NASA will never give it up"...
>    Which is the same thing that was said about the Delta and Atlas
>programs.  (And was said about Intelsat).  It just takes a top-level
>(Presidential level) policy decision, and support in Congress...

I think NASA would fight much harder over the shuttle than they did over
the expendables.  Commercializing the expendables was done after NASA had
largely lost interest in them.  (And NASA still thinks that a NASA payload
on an Atlas is a government launch, not a commercial one.)  The shuttle
is NASA's current flagship; they'll seriously fight to keep it.  Given the
reputation they've acquired in recent years, they may not succeed... but
it's going to require real determination from the White House and Congress
to make it happen.  If the management doesn't seem determined to split it
off completely, NASA will propose a "compromise" in which more of the detail
work is farmed out to contractors but NASA stays in control.
--
"I'm not sure it's possible            | Henry Spencer at U of Toronto Zoology
to explain how X works."               |  [e-mail]   utzoo!henry

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

Date: 22 Nov 90 15:00:42 GMT
From: agate!shelby!msi.umn.edu!cs.umn.edu!uc!nachos.SSESCO.com![e-mail]  (Chris Elmquist)
Subject: Re: NASA Prediction Bulletin Distribution

In article <[e-mail]> [e-mail] writes:
>
>
>   It would be very nice, if the NASA Prediction Bulletins
>   will be available from some anonymous-ftp site.  I have
>   just asked  in  newsgroup sci.astro, if the predictions
>   already are in some file archive, but I haven't got any
>   positive answer yet.
>

I am working on this issue with Dr. Kelso and we've just about
got it in place.  Stand by for further details...



--
Chris Elmquist, N0JCF
Internet: [e-mail]
   AMPRN: [e-mail]
 BellNet: [phone]
--
Chris Elmquist, N0JCF
Internet: [e-mail]
   AMPRN: [e-mail]
 BellNet: [phone]

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

Date: 24 Nov 90 04:45:57 GMT
From: mcgill-vision!thunder.mcrcim.mcgill.edu!clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Photon engine

In article <[e-mail]> [e-mail] (Henry Troup) writes:
>|>only thing left behind with an expanding cloud of plasma. A 100 tonne
>|>ship accelerating at 1 g requires a 3x10**11 watt powerplant. How
>|>does that compare to the human species total power output these days?
>
>Well, it must be less than the power output of a shuttle at launch, right?

Shuttle power output at launch is 15-20 gigawatts, I believe.

However, the inequality you propose doesn't work.  There is no unique
answer to the question of power output for a given mass at a given
acceleration.  It depends on the exhaust velocity.

A 100T ship at 1G (call it 10 m/s^2) requires a thrust of 1MN.  Thrust
is mass flow times exhaust velocity, by conservation of momentum.  At
an exhaust velocity of 3e8 m/s, naively (ignoring relativistic issues),
we need 3.3e-3 kg/s of mass flow.  Kinetic energy over time of that flow,
with respect to the rocket, naively, is 0.5*mass_flow*ve^2, or about
15e13 W.  Call it 150 terawatts.  I'd have to hit the books to sort out
the non-naive version of this, but it probably won't differ by more than
a small integer, and it might even be the same.

I don't have numbers handy for the whole species or total power, but the
electrical power generating capacity of the US is circa 1 terawatt, I think.

Handling 150TW would be, um, a challenge.  For example, assume an efficiency
of 50%.  (That's awfully good for lasers, which are inherently pretty lossy
devices.)  That means our total power output actually has to be 300TW, and
the missing 150TW comes out as heat.  We have to get rid of that heat...
somehow.  The only long-term answer is radiators, but they're big and heavy.
Ignoring practicalities, let us use evaporative cooling instead.  We'll be
generous and say our lasers can run at 2500K (2227C; if you want it in
Fahrenheit, Rankine, or Reaumur, convert it yourself :-)).  Assume our
evaporative material is water, which has a high heat capacity, call
its heat capacity a straight 4.2kJ/kgK, ignoring heats of melting and
boiling, and assume we start with ice at roughly absolute zero.  Then
we are using a mere 15 kilotons of water per second to cool our 100T
spacecraft.  That won't work. :-)

Another non-trivial consideration for photon rockets is how you power them.
They are fiercely difficult to build.  If you are burning up far more mass
powering them than you are exhausting through them, better you should build
a system with the same net mass flow and a lower exhaust velocity, by using
all the mass as exhaust.  Using fission or fusion to power a photon rocket
is ridiculous, in particular.  Fusion burns hydrogen to helium (ignoring
lots of fine points), releasing quite a small fraction of the total mass
as energy.  Even with no losses, most of your fuel mass is going to run
your fusion reactor, after which you are dumping the helium overboard at
roughly zero velocity (compared to the exhaust velocity, any velocity you
can get for that helium is zero).  Building a fusion rocket would give
similar performance with many fewer problems.  Photon rockets make sense
only if you can power them with total matter annihilation; even matter-
antimatter reactions are better used as rockets than as a power source.
(All the more so because we are not very far from being able to build
antimatter rockets, while handling terawatts for a photon rocket is
well beyond us.)
--
"I'm not sure it's possible            | Henry Spencer at U of Toronto Zoology
to explain how X works."               |  [e-mail]   utzoo!henry

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

Date: 22 Nov 90 15:00:42 GMT
From: agate!shelby!msi.umn.edu!cs.umn.edu!uc!nachos.SSESCO.com![e-mail]  (Chris Elmquist)
Subject: Re: NASA Prediction Bulletin Distribution

In article <[e-mail]> [e-mail] writes:
>
>
>   It would be very nice, if the NASA Prediction Bulletins
>   will be available from some anonymous-ftp site.  I have
>   just asked  in  newsgroup sci.astro, if the predictions
>   already are in some file archive, but I haven't got any
>   positive answer yet.
>

I am working on this issue with Dr. Kelso and we've just about
got it in place.  Stand by for further details...



--
Chris Elmquist, N0JCF
Internet: [e-mail]
   AMPRN: [e-mail]
 BellNet: [phone]
--
Chris Elmquist, N0JCF
Internet: [e-mail]
   AMPRN: [e-mail]
 BellNet: [phone]

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

End of SPACE Digest V12 #593
*******************