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Subject: SPACE Digest V11 #181

SPACE Digest                                     Volume 11 : Issue 181

Today's Topics:
       Re: Shuttle escape systems, was Challenger's Last Words
           Re: Solar System Questions from a Novice
              Re: Strange Flash of Light
              Galileo Update - 03/23/90
        Re: What was Challenger really up to?
                 Railgun ...
             Re: Intelsat / Titan failure
              Voyager Update - 03/23/90
       Re: Shuttle escape systems, was Challenger's Last Words
               RE: SPACE Digest V11 #93
           Re: Solar System Questions from a Novice
----------------------------------------------------------------------

Date: 23 Mar 90 05:19:27 GMT
From: crash!orbit!pnet51![e-mail]  (S Schaper)
Subject: Re: Shuttle escape systems, was Challenger's Last Words

I think I remember reading that the shuttle floats like it flies - like a
brick. If they did ditch, they would have to get out _fast_.

 The SRB's did _not_ steer straight in the Challenger accident, if the exhaust
plumes on that memorable picture mean what they seem to mean.

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

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

Date: 23 Mar 90 16:58:18 GMT
From: cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Solar System Questions from a Novice

In article <[e-mail]> [e-mail] (William Lewis) writes:
>  I can think of at least one stable orbit around binary stars of
>approximately equal mass and large separation ...  The two
>stars are separated by about 1 AU, and the planet orbits in the point
>which could be called the L4 or L5 point, equidistant from the suns.

Sorry, this is *not* stable.  The L4 and L5 points are stable only if
the two major bodies have very *unequal* masses.  I don't remember the
number for sure, but I have a vague recollection that the big one has
to be something like 30 times the mass of the small one.

Please don't ask for the intuitive explanation; as far as I know, there
isn't one.  You just have to grit your teeth and do the math.
--
US space station:  8 years    |     Henry Spencer at U of Toronto Zoology
and still no hardware built.  | uunet!attcan!utzoo!henry [e-mail]

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

Date: Fri, 23 Mar 90 15:39:53 CST
From: [e-mail] (Barbarisi)
Subject: Re: Strange Flash of Light


Several posters have discussed a large, lightning-like, flash of light
which occured over large parts of Missouri.  It was described as occuring
on a clear winter night.  Further it was omnidirectional; it had no apparent
point of origin and observers recorded the same intensity of light reqardless
of the direction in which they viewed the event.  This sounds like one of
four phenomena:

1)  Clear air lightning - which I have observed on many a winter night in
Minnesota.  Clear air lightning is a diffuse, large scale discharge of
static electricity, not associated with a storm system.  When I've seen it,
it was a flash that enveloped the whole sky and there was no discernable
thunder.

2)  St. Elmo's Fire - which may be related to clear air lightning.  St. Elmo's
is a form of static discharge which emits bright light and, when observed
closely, a "crackling" sound.  For lack of knowledge, I won't say more
about it.  Perhaps someone out there can comment on the likelihood of this
event being a discharge of St.Elmo's Fire.

3)  A distant massive thunderstorm - I recall there were some truly nasty
tornadic thunderstorms South of Missouri on the night of the flash.  Flashes
from such storms may be visible hundreds of miles away - the light propagates
by reflection off high altitude ice crystal clouds.  The result at a distance
is a diffuse flash of light that encompasses the entire sky.

4)  Laser beams bouncing off Elvis' sequined jacket.


                      Marco Barbarisi
                      Naval Coastal Systems Center
                      Panama City, Florida
                      [e-mail]

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

Date: 24 Mar 90 00:09:16 GMT
From: snorkelwacker!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 03/23/90


                              GALILEO
                        MISSION STATUS REPORT
                          MARCH 23, 1990

     As of noon Friday (PST), March 23, 1990, the Galileo spacecraft is
70,023,320 miles from the Earth, 11,852,790 miles from Venus and is traveling
at a heliocentric velocity of 85,320 miles per hour.  Round trip light time
is 12 minutes, 26 seconds. The spacecraft's spin configuration continues at
3.15 rpm with a spacecraft attitude sun point angle of 0.5 degrees.

     Three SITURNS to lead the sun were successfully performed on March 19,
21, and 23.  Spacecraft performance for these activities was as expected and
without incident. A NO-OP command was sent on March 19 to reset the Command
Loss Timer to 288 hours consistent with the plan for this mission phase.

     The Venus-Earth (VE-2) sequence memory load was sent on March 22; the
load was successfully transmitted and received by the spacecraft without
incident.  The VE-2 sequence controls spacecraft activities from March 26 to
April 23.  This sequence includes 12 SITURNS, 1 Retro-Propulsion Module (RPM)
flushing activity, several cruise science Memory Readouts (MROs) for the
Magnetometer (MAG), Extreme Ultraviolet Subsystem (EUV), Dust Detector
Subsystem (DDS) and Energetic Particles Dectector (EPD), and a telemetry
data rate switch back to 40 bps from 10 bps.  During early April, from
April 9 thru April 12, time windows have been established for the planned
Trajectory Course Manuever (TCM-4A).

     The -x RTG (T4) temperature measurement which began acting erratically
on March 8 went to full saturation on March 21 indicating an open circuit
somewhere between the transducer and the Command and Data Subsystem (CDS);
other CDS measurements routed to this CDS tree switch are all reading as
expected.  The loss of these measurements does not pose a threat to the RTG
or the spacecraft since power performance parameters (V, I) are measured
separately by the power subsystem electronics.

     The AC/DC bus voltage imbalance measurements have varied only slightly.
The DC measurement has fluctuated between 21.31 and 21.62 volts; the AC
measurement has fluctuated between 48.56 and 48.75 volts.  All other
power-related measurements (bus voltages, bus currents and shunt current)
and other subsystem measurements have all been as expected.

     Deep Space Network (DSN) support for Galileo continues at 10 bps without
problems, although the B-string telemetry at the stations experience
difficulty in maintaining lock due to the currently unfavorable ratio of bit
rate to subcarrier frequency transmitted by the spacecraft.  The problem is
recognized and is considered acceptable at present.  Characterization of the
problem by DSN Operations is in progress.

     The impact of the DSN plan for elevation bearing maintenance on Galileo,
particularly the Trajectory Correction Maneuver for Earth Encounter #1 (TCM-4)
is being evaluated by the DSN and Galileo.  It appears that some impact may
be inevitable, but the outcome of the first Goldstone inspection is awaited
before any final maintenance decisions can be made.

     A Mission Readiness Test (MRT) with the 34 meter antenna in Australia
was completed successfully, and the Galileo project participated in a
Multi-Mission Verification Test to establish compatibility of the new DSN
Telemetry Processor Assembly (TPA).  The new TPA software is scheduled to
begin operational support on April 29.

     The Galileo project released about 4.5 hours of its scheduled tracking
coverage on March 22 allowing the International Cometary Explorer spacecraft
(ICE) to collect valuable solar flare data from the recent event on
March 21.  The tracking coverage was released only after successful uplink
transmission and total verification of the VE-2 load on the Galileo
spacecraft was completed.


 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 23 Mar 90 05:19:15 GMT
From: crash!orbit!pnet51![e-mail]  (S Schaper)
Subject: Re: What was Challenger really up to?

I think that that is about as likely as my initial theory, that I didn't take
at all seriously at the time, that Khaddafy had a laser on a fishing trawler
off shore (remember the geopolitics at that time?)
  What was Christa McAuliffe doing on board if it was a weapons-capable laser
mission?

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

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

Date: 23 Mar 90 10:45:22 GMT
From: ogicse!blake![e-mail]  (William Lewis)
Subject: Railgun ...


  I thought I'd repost this from sci.electronics in case anyone was
interested ...

From: [e-mail] (Paul A. Houle)
Newsgroups: sci.electronics
Subject: Re: Rail Guns
Message-ID: <[e-mail]>
Reply-To: [e-mail] (Paul A. Houle)
Lines: 23
Posted: Thu Mar 22 20:32:26 1990


      Actually,  the fastest railgun in the world is powered
by a huge bank of ordinary car batteries;  According to an article
in Av Week about six months ago or so,  a company in California has
an electromagnetic gun,  either a railgun or coilgun,  that has a
high enough terminal velocity to put something into orbit.
Actually doing it is a problem,  because you'd need something that
weighs about a gram that can perform an orbital insertion maneuver -
never mind air resistance.

       Another story in last week's Av Leak was about a coil gun
proposed to be based in Hawaii;  the goal is to toss kilogram
quantities of matter into polar orbit.  Of course,  the only
reason to launch something into a polar orbit is for surveillance
applications...  Looks like Cheney and the .mil bunch aren't ready
to pay off a peace dividend.  It seems to me that we could use
something that could throw sand,  ice,  and metals into LEO or
G-sync at $10 /lb.  In fact,  that's a hell of a way to build a
space station.  Outer layer is a kevlar baloon,  and the inner
layer is Kevlar and something kinda like Saran wrap;  blow in
a foot of sand,  and you've got a cheap and simple space
station / long-rasnge spacecraft with excellent radiation and
meteorite resistance...

-----------------------end of repost------------------------------

--
JESUS SAVES   |  [e-mail]       Seattle, Washington
but Clones 'R' Us makes backups!  |  47 41' 15" N   122 42' 58" W

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

Date: 23 Mar 90 13:54:18 GMT
From: mailrus!sharkey!itivax!vax3![e-mail]  (Allen W. Sherzer)
Subject: Re: Intelsat / Titan failure

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>There is also the
>question of whether you want to bring it back down or tack a fresh upper
>stage onto it and send it on its way.  I very strongly suspect the latter.

Wouldn't tacking on a fresh upper stage using the shuttle cost more than the
Intelsat and launch are worth? I assume that would take a dedicated shuttle
flight. That plus the cost of the stage plus the cost of training seems like
it would cost a lot more than an new Intelsat and launch.

  Allen
-----------------------------------------------------------------------------
| Allen W. Sherzer |Archie: These guys are terrorists. Know what that means?|
|   [e-mail]    |Lorenzo: No prisoners!                                  |
|                  |Recce: You say that like there was some other way.      |

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

Date: 23 Mar 90 17:26:41 GMT
From: elroy.jpl.nasa.gov!forsight!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Voyager Update - 03/23/90



                              Voyager
                       Mission Status Report
                          March 23, 1990

                              Voyager 1

     Voyager 1 continues to collect routine cruise science data. High-rate
Ultraviolet Spectrometer Subsystem (UVS) observations were conducted on HD
206165 (March 2) and  Markarian 509 (March 6 & March 13). One frame of
high-rate Plasma Wave Subsystem (PWS) data was recorded on March 5 and
March 12.

     An AGC/Command threshold test was executed on March 7. This is the first
time that this particular test was performed on Voyager 1. A number of
verification alarms were experienced during the uplink of the AGC/Command
Threshold test, but the alarms did not appear to have any adverse impact on
the test, and the test was completed successfully.

     The processing and analysis of Planetary Radio Astronomy Subsystem (PRA)
Experiment Data Record (EDR) data continues daily, for the purpose of
observing and logging radio events of interest to the PRA team.

     On March 13, a Magnetometer (MAG) sequence was executed by the spacecraft.
No problems were encountered and the spacecraft performance was nominal. The
instruments responded satisfactorily.

     Images from the "family portrait" have been transmitted back to Earth.
Uranus and Neptune images were successfully sent back on March 16, and Saturn
images on March 20. The remainder of the images are scheduled for transmission
from the spacecraft's tape recorders for tonight (Mars) and for March 27
(Jupiter, Earth and Venus).

     Spacecraft performance for all the sequenced activity has been nominal.


                              Voyager 2

     Voyager 2 continues to collect routine cruise science data.  One frame
of high-rate PWS data was recorded on March 5 and March 12. The AB gyro pair
was turned on on March 5. Thermal events (AB gyros on) induced a command
moratorium  that resulted in approximately two days of this period being
unavailable for acquisition of ranging or coherent Doppler data.

     High-rate UVS observations were conducted on HD 212571 (March 5) and
NGC 7027 (March 7, 12, 13 and 14). Most of this data was lost due to the
limited Deep Space Network (DSN) coverage. An Attitude and Articulation
Control Subsystem (AACS) test and Computer Command Subsystem (CCS) timing
offset determination were performed on March 7.

     A Cruise Maneuver (CSRMVR) was performed on March 14 and a PLSCAL on
March 15. Commands to update the AACS yaw and roll axes were also transmitted
in preparation for the mini-CRSMVR executed on March 14. The update was
verified by an AACS Memory Read Out.

     Spacecraft performance for all the sequenced activity has been nominal.


 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 23 Mar 90 16:51:22 GMT
From: zaphod.mps.ohio-state.edu!samsung!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Shuttle escape systems, was Challenger's Last Words

In article <[e-mail]> [e-mail] (S Schaper) writes:
>I think I remember reading that the shuttle floats like it flies - like a
>brick. If they did ditch, they would have to get out _fast_.

More to the point, the shuttle ditches like it somersaults:  in pieces.
It's too fragile to survive a ditching or belly landing.  The STS-1
flight plan (which I have a copy of) has a number of contingency branches,
involving things like multiple engine failures and the like, which involve
coming down in water... every one of them ends with "EJECT".

(If this confuses anyone, note that Columbia had ejection seats for the
first four flights.)
--
US space station:  8 years    |     Henry Spencer at U of Toronto Zoology
and still no hardware built.  | uunet!attcan!utzoo!henry [e-mail]

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

Date:     Fri, 23 Mar 90  16:16 GMT
From: "P D JONES, CRU" <[e-mail]>
Subject:  RE: SPACE Digest V11 #93

Please do not send any more messages to this account.
Its previous owner, Mike Salmon, no longer works here.
Thank you.

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

Date: 23 Mar 90 10:16:19 GMT
From: ogicse!blake![e-mail]  (William Lewis)
Subject: Re: Solar System Questions from a Novice

In article <[e-mail]> [e-mail] (John F Nixon) writes:
>[e-mail] (Christopher Neufeld) writes:
>>3) A given planet revolves around one star then the other in a figure eight
>>pattern, while the suns revolve around each other. I believe this situation
>>is unstable.
>
>No, there are stable orbits around binary stars!  I wish I could remember the
>reference, if you are interested I'll try and find it.  Since a lot of stars
>are members of binary systems, this can really increase the number of planetary
>systems which might exist 8-).

  I can think of at least one stable orbit around binary stars of
approximately equal mass and large separation ... I suppose it could
be viewed as a degenerate case of either case 1 or 2, above. The two
stars are separated by about 1 AU, and the planet orbits in the point
which could be called the L4 or L5 point, equidistant from the suns.
More general is the configuration I *think* is called a "Kemplerer
rosette", in which all the stars/planets/what-have-you rotate at equal
distances from a common center of mass, spaced equally around the edge
of a circle ... symmetry shows that it's at least sort of stable, although
I don't know how stable it would be against perturbations.
  Other situations spring to mind, but again they're (a) sort of
unlikely, as they're not planar; and (b) I have no idea at all how
they would respond to perturbations ... such as, two stars, rotating
about a fixed point, while the planet "bobs" up and down perpendicular
to the plane of rotation, passing through the center of mass on each
orbit. It might be possible to cancel out perturbations with some sort
or resonance between the orbits of the stars and the planet, but it's
probably not worth the trouble. I think the planet's orbit would
tend to widen out into an ellipse ... if things matched up, the
planet could miss the stars on every orbit, but again I don't
know about perturbations (or even of any situation which could
give rise to such a bizarre configuration...)
  Don't quote me on any of this, as the last contact I had with
taught orbital mechanics was an introductory physics course some
time ago ...


--
JESUS SAVES   |  [e-mail]       Seattle, Washington
but Clones 'R' Us makes backups!  |  47 41' 15" N   122 42' 58" W

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

End of SPACE Digest V11 #181
*******************