Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_0/V10_060.TXT

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Date: Thu, 21 Sep 89 03:49:53 -0400 (EDT)
Subject: SPACE Digest V10 #60

SPACE Digest                                      Volume 10 : Issue 60

Today's Topics:
             Re: NASA missions/time table
           Frequently asked SPACE questions
       Re: NASA Headline News for 09/06/89 (Forwarded)
         Re: Economies of Scale in Launchers
              Re: RTGs for use on earth
               Re: Pluto meets Neptune
              Re: Neptune fly-by
            Re: Linguistic Tidbits
              Re: RTGs for use on earth
----------------------------------------------------------------------

Date: 9 Sep 89 19:40:14 GMT
From: [e-mail]  (Terry Hancock)
Subject: Re: NASA missions/time table

In article <[e-mail]> [e-mail] (John Sparks) writes:
>
>Y'know, with everyone complaining about polluting Jupiter with microbes and
>with launching the Probe with so much plutonium aboard, I wonder if they will
>complain about Galileo using Earth/Moon for a Gravity assist? I can hear them
>now:
>
>"It's using up our gravity"
>"It'll slow us down. We could fall into the sun"
>"The moon will fall on us now"
>
>Conserve Our Gravity! Ban Galileo!
>
>--
>John Sparks   |  {rutgers|uunet}!ukma!corpane!sparks | D.I.S.K. 24hrs 1200bps

    Ah, no, probably the public isn't that silly (well, maybe, but I
doubt it would get further than the tabloids).  However, I think there is
something to think about in that Galileo will be travelling at great
velocity, coming less than 200 miles from the Earth's surface.  What if
the course were miscomputed (or more likely, what if course corrections
failed due to some hardware failure in the aging machine)?  Personally,
I'd hate to see Galileo become a meteor after several years of waiting
and hoping for it's Jupiter encounter.
    How would the RTGs handle an extreme high velocity reentry (or
atmosphere - crossing orbit, it might still leave the atmosphere of
course)?  Me -- I think a 200 mile course correction error is pretty
outrageous, but so are some of the other possibilities that have raised
protest.
    I mean, think about it, everyone's heard NASA JPL officials
complain about the risks Voyager took in coming just 3000 miles from
the Neptunian Cloudtops, and now we're talking 150 miles from Earth's
cloudtops.  Yes, *I* know that Gas Giants have more extended atmospheres
than Terrestrials, but does "Joe Public" ?  And of course, we *know*
Earth's atmosphere pretty well compared to Neptune, but ...
    Just think about how it would sound to someone with very little
technical background.


Just a paranoid little food for thought.:-)




***********************************
Terry Hancock
[e-mail]
***********************************

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

Date: Sun, 10 Sep 89 04:00:13 PDT
From: Eugene Miya <[e-mail]>
Subject: Frequently asked SPACE questions

This list does change.

This is a list of frequently asked questions on SPACE (which goes back
before 1980).  It is in development.  Good summaries will be accepted
in place of the answers given here.  The point of this is to circulate
existing information, and avoid rehashing old answers.  Better to
build on top than start again.  Nothing more depressing than rehashing
old topics for the 100th time.  References are provided because they
give more complete information than any short generalization.

Questions fall into three basic types:
1) Where do I find some information about space?
Try you local public library first.  You do know how to use a library, don't
you?  Can't tell these days.  The net is not a good place to ask for
general information.  Ask individuals if you must.  There are other sources,
use them, too.  The net is a place for open ended discussion.

2) I have an idea which would improve space flight?
Hope you aren't surprised but 9,999 out of 10,000 have usually been
thought of before.  Again, contact a direct individual source for
evaluation.  NASA fields thousands of these each day.

3) Miscellanous queries.  Sorry, have to take them case by case.

Initially, this message will be automatically posted once per month
and hopefully, we can cut it back to quarterly.  In time questions and
good answers will be added (and maybe removed, nah).

1) What happen to Saturn V plans? What about reviving the Saturn V
as a heavy-lift launcher?

Possible but very expensive -- tools, subcontractors, plans, facilities
are gone or converted for the shuttle, and would need rebuilding,
re-testing, or even total redesign.

2) Where can I learn about space computers: shuttle, programming,
core memories?

%J Communications of the ACM
%V 27
%N 9
%D September 1984
%K Special issue on space [shuttle] computers

Other various AIAA and IEEE publications.

Computers in Spaceflight: The NASA Experience
James E.  Tomayko
1988?

3) SETI computation articles?

%A D. K. Cullers
%A Ivan R. Linscott
%A Bernard M. Oliver
%T Signal Processing in SETI
%J Communications of the ACM
%V 28
%N 11
%D November 1984
%P 1151-1163
%K CR Categories and Subject Descriptors: D.4.1 [Operating Systems]:
Process Management - concurrency; I.5.4 [Pattern Recognition]:
Applications - signal processing; J.2 [Phsyical Sciences and Engineering]:
astronomy
General Terms: Design
Additional Key Words and Phrases: digital Fourier transforms,
finite impulse-response filters, interstellar communications,
Search for Extra-terrestrial Intelligence, signal detection,
spectrum analysis

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

Date: 10 Sep 89 15:45:05 GMT
From: cs.utexas.edu!csd4.csd.uwm.edu!srcsip!tcnet!orbit!pnet51![e-mail]  (S Schaper)
Subject: Re: NASA Headline News for 09/06/89 (Forwarded)

That is why the ET is rust coloured. The first launch was painted white, but
to increase payload capacity, that was discontinued.

UUCP: {amdahl!bungia, uunet!rosevax, chinet, killer}!orbit!pnet51!schaper
ARPA: crash!orbit!pnet51![e-mail]
INET: [e-mail]

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

Date: 11 Sep 89 14:44:29 GMT
From: deimos.cis.ksu.edu!cveg!hcx![e-mail]  (6079 Smith James)
Subject: Re: Economies of Scale in Launchers


In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
> Mmm...  mass flow rate is proportional to throat area.  For a given flow
> rate, assuming negligible back pressure, maximum thrust comes with the
> longest possible nozzle, for maximum expansion.

True, if "back pressure" here means "ambient pressure."  If ambient
pressure is not zero (i.e. you are in atmosphere), there is an optimal
nozzle expansion ratio, where ambient pressure equals the exit pressure
of the exhaust gases.  Most engines meant to fly between ground and
space have a compromise nozzle.

Supersonic flow causes a nasty problem with overexpanded nozzles:  due to
friction with the nozzle walls, there is a region near the wall where
ambient pressure can force its way into the nozzle.  This causes uneven
loading on the noxzzle.  Result: the nozzle is nastily clipped
off.  Very bad for fuel-cooled nozzles.  One must be careful with
overexpansion.

> In article <[e-mail]> [e-mail] (Bob Pendleton) writes:
> >Can anyone tell me if there is a relationship between mass flow rate
> >and optimal nozzle skirt length? A relationship that is independent of
> >back pressure.

Mass flow rate affects injector design, thus, more mass flow rate means
bigger nozzles.  But the shape and expansion ratio will be the same for
a given design spec, even if you increase mass flow/thrust.

As for the shape itself, that is determined by the Twin Gods of Materials
and Fluid Dynamics, and their ways are mysterious to mere engineers-in-
training.  We place our faith in De Laval, amen.  :-)  Try to find a
source by De Laval, who designed the conventional converging-diverging
nozzle.


|  James W. Smith, University of Arkansas  |  hcx![e-mail]   |
|----------------------------------------------------------------------------|
|    I'm so depressed.  If I didn't have so much to do, I'd be a nihilist.   |

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

Date: 11 Sep 89 23:27:01 GMT
From: vsi1!daver!lynx![e-mail]  (Neal Woodall)
Subject: Re: RTGs for use on earth

In article <[e-mail]> John Sahr writes:
>In article <[e-mail]> Neal Woodall writes:

>>......A radiation machine was stoler from a hospital, and wound up in a junk
>>yard. The owner and his nephew busted the machine open while stripping it for
>>scrap, and discovered this pretty glowing powder (uh oh!). Since they were
>>all ignorant of most science (about zero education), they actually had a
>>party where all of their friends came over an rubbed the glowing powder over
>>their bodies!

>It is a little unfair to blame these people for not knowing about highly
>radioactive materials.  It is, after all, rather outside their usual
>experience.  The only reason this didn't happen in the States
>is that the irradiator would probably have been correctly disposed of.


First of all, I am not "blaiming" anyone for a lack of knowledge....and I
certainly am not implying that because they lived in Brazil they were stupid.
They were ignorant of any knowledge of radioactive materials, a fact shown in
their careless handling of the material. Hell, I know many people in the US
that would probably do the same damn thing!

The statement of their lack of education and ignorance of radioactive materials
is just part of the story, and is not indicative of any prejudice on my part.

Now, if I were to see some glowing blue powder of an unknown origin, you can be
quite sure that I would run away very fast until the penominon had been shown
to be harmless!





Neal

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

Date: 12 Sep 89 16:00:08 GMT
From: rochester![e-mail]  (Cesar Quiroz)
Subject: Re: Pluto meets Neptune

In <[e-mail]>, [e-mail] (John Sparks) wrote:
| Something I've wondered:
|
| Does Pluto's orbit actually intersect Neptune's orbit? If so has
| any body ever done a computer simulation to see if and when they
| would ever collide?

In [A E Roy, `Orbital Motion', Adam Hilger, 1988], section 8.7, you
can find a nice survey of large-scale numerical integrations (=
simulations) of the solar system, up to almost the most recent work
done with the Digital Orrery.  Roy cites a simulation by Cohen and
Hubbard (he refers to _Astron. J._, 70 10, 1965) that showed an
interesting commensurability:

    3 LP - 2 LN - LPP ~ 180 degrees +/- 76 degrees

where LP is the mean longitude of Pluto, LN is the mean longitude of
Neptune, and LPP is the longitude of Pluto's perihelion, and ~ is to
be read "librates around a value of".  What all this means is that
when Pluto is at its perihelion (i.e., rather inside Neptune's
turf), Neptune is nowhere near.  Roy mentions that the 1965
simulation showed that closest approach occurred at aphelion (I
guess, Pluto's aphelion) and a distance of 18AU, quite safe if you
ask me.  There is more interesting stuff in the chapter, so you may
find it useful to head for your nearby university library.  (Are
there more recent simulations?  It would be interesting if, perhaps
by adding Uranus to the problem, the amplitude of the libration of
the commensurability would be reduced from its 80 or so degrees.)

--
                                      Cesar Augusto Quiroz Gonzalez
                                      Department of Computer Science
                                      University of Rochester
                                      Rochester,  NY 14627

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

Date: 12 Sep 89 15:58:24 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Neptune fly-by

In article <[e-mail]> [e-mail] (John E Van Deusen III) writes:
>>> ... Also, if there is a binary companion to the Sun or an
>>> undiscovered planet X, the perturbation of the probe's trajectory
>>> might have indicated it ...
>>
>> I'm told that the latest and most sophisticated analysis strongly
>> suggests that there is no such body...
>
>You may have convinced me, but this experiment is not one of my wild-
>eyed schemes -- it was thoroughly explained at one of the televised
>NASA briefings...

Yes, there is still interest in the idea, and this is one reason why both
Voyagers and both Pioneers are still being tracked.  My understanding is
that the tracking results for the past few years have already put some
substantial constraints on mass and location of the hypothetical Planet X,
because there are no unaccounted-for perturbations yet.  (This may sound
inconsequential compared to planetary observations covering centuries, but
the probes can be tracked *much* more accurately than the planets.)  This
is an excellent opportunity for gathering high-precision evidence, so it
won't be missed even if the answer is already strongly suspected.

In fact this is an opportunity that won't be repeated for a long time,
because all the future outer-planet missions that are within current
planning horizons are orbiters.  It may be a long time before we have
several probes simultaneously heading starward again.

>... I understand, however, that Voyager I, was sent out of the
>orbital plane in order to get a close VISUAL look at Titon.  I don't
>know if it would have been possible, but it seems that radio occultation
>data from Titon would have been more valuable...

In hindsight, yes.  At the time, nobody knew that Titan's atmosphere was
opaque and featureless.  And whatever one might think of the way things
worked out, Jupiter (plus Galilean moons) and Saturn (plus Titan) *were*
the primary Voyager mission objectives.
--
V7 /bin/mail source: 554 lines.|     Henry Spencer at U of Toronto Zoology
1989 X.400 specs: 2200+ pages. | uunet!attcan!utzoo!henry [e-mail]

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

Date: 12 Sep 89 17:13:43 GMT
From: phoenix!puppsr![e-mail]  (marty ryba)
Subject: Re: Linguistic Tidbits

[e-mail] (Steve Willner) writes:

>From article <[e-mail]>, by [e-mail] (Henry Melton):
>> I have wondered in the past: what are the generic terms?
>> [for apogee, perigee, etc.]
>The generic terms are apoapsis and periapsis.  The plural, in case you
>want to speak of both, is "apsides."  (Pronounced with three syllables:
>aps'-uh-deez.)

>By the way, the apsides of lunar orbit are the "aposelene" and
>"periselene;" the Greek prefixes should be used with the Greek root
>words helion, gee, and selene rather than the Latin roots sol, terra,
>or lune.  (Or something similar; my lack of proper classical education

Commonly used (correctly or incorrectly I won't judge) in the astronomical
community are periastron and (I guess) apoastron.  "Astron" is the generic
for star.

Marty Ryba (slave physics grad student)
They don't care if I exist, let alone what my opinions are!
[e-mail]
Asbestos gloves always on when reading mail

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

Date: 6 Sep 89 17:25:32 GMT
From: oliveb!pyramid!octopus!vsi1!daver!lynx![e-mail]  (Neal Woodall)
Subject: Re: RTGs for use on earth

In article <[e-mail]> (John Roberts) writes:

>Several years ago, a hospital radiation machine was stolen and ended up
>in a junk yard. The radioactive cobalt source was melted into a small batch of
>steel and made into fixtures for restaurant furniture. Fortunately, the problem
>was detected and the fixtures recovered.)

In Brazil there was a similar incident last year. A radiation machine was
stoler from a hospital, and wound up in a junk yard. The owner and his
nephew busted the machine open while stripping it for scrap, and discovered
this pretty glowing powder (uh oh!). Since they were all ignorant of most
science (about zero education), they actually had a party where all of their
friends came over an rubbed the glowing powder over their bodies! A few
days later they were all dead. Their bodies were badly burned and disfigured
by the radiation and induced decomposure of their flesh. Several city blocks
had to be evacuated and decontaminated. The bodies of the victims were buried
in lead crypts, which are still monitored weekly by the Brazilian government
for leakage and contamination. I think that the substance was an isotope of
cesium or strontium.

At least we in the USA have Cyalume (R) Lightsticks to play with when we
feel like playing with luminescent things!




Neal

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

End of SPACE Digest V10 #60
*******************