Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_4/V12_470.TXT

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Subject: SPACE Digest V12 #470

SPACE Digest                                     Volume 12 : Issue 470

Today's Topics:
        Re: Hubble Space Telescope (revisited)
           Re: disposal of N-waste into sun
       Re: You Can't Expect a Space Station to be Cheap
              Galileo Update - 10/16/90
             PLUTO AND PIONEER 10
              Magellan Update - 10/18/90
               Re: Magellan/Venus Info
       Re: Where is 0 longitude, was re: Venus/Magellan, poles
               Theories needed on life
              Voyager Update - 10/18/90

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
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----------------------------------------------------------------------

Date: 18 Oct 90 15:45:06 GMT
From: agate!bionet!uwm.edu!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Hubble Space Telescope (revisited)

In article <[e-mail]> [e-mail] writes:
>    * It can be argued and supported that for many years our
>      government has witheld information from the people,
>      concerning extra-terrestrial life.

A government that couldn't keep Iranscam secret for a few years has been
hiding the biggest news in history for decades?  When anyone in on the
secret would know that spilling it would get his name not only in the
news, but in the history books?  Give me a break.
--
"...the i860 is a wonderful source     | Henry Spencer at U of Toronto Zoology
of thesis topics."    --Preston Briggs |  [e-mail]   utzoo!henry

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

Date: 16 Oct 90 13:55:50 GMT
From: swrinde!cs.utexas.edu!sun-barr!newstop!texsun!convex![e-mail]  (Dave Dodson)
Subject: Re: disposal of N-waste into sun

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>In article <[e-mail]> [e-mail] (Dave Dodson) writes:
>>A launch into the sun requires sqrt (11^2 + 30^2) km/sec =~ 32 km/sec.
>>This is so the payload, after having climbed out of the Earth's gravity
>>well, is travelling away from the Earth at 30 km/sec.  If the velocity
>>vector is in the opposite direction from the Earth's velocity vector
>>around the sun, the payload would fall into the sun.
>
>   This is wrong. If something is fired away from the surface of the
>Earth at Earth escape velocity of ~11 km/s, it will wind up pacing the
>Earth in its orbit around the Sun at 30 km/s. This is regardless of the
>direction in which the object is fired away from the surface. You still
>need another 30 km/s to fall into the Sun. This makes a total of 41 km/s,
>not 32 km/s. I don't understand why you felt you needed the Pythagorean
>identity here. Recall from first-year physics classes that the "escape
>velocity" is in fact a scalar, and that neglecting atmospheric effects,
>any object fired in any trajectory which does not intersect the ground or
>a mountain or something, will leave if fired in excess of 11 km/s.

You have mistaken my statement of conservation of energy for an application
of the Pythagorean Theorem.  Let me explain...

What I am going to do is break the trajectory into two parts.  The first is
when the object is near the earth and essentially under its gravitational
influence.  The second part is when the object is far from the earth and
essentially under the sun's gravitational influence.  This is the so-called
"patched-conic" approximation to multibody orbital mechanics.  I'll use the
center of the earth as the origin of our coordinate system for the first part
and the sun for the second part.  The way I patch the parts together at the
boundary is "good enough" for a first approximation.

When you launch something from near the earth, some of the kinetic energy
is transformed into potential energy as the object moves away.  Conservation
of energy states that

        PE(R) + KE(R) = PE(infinity) + KE(infinity)

where R is the radius of the earthm, and by infinity, I mean "far enough from
the earth that its influence is small compared to the influence of the sun."
That is the boundary between parts 1 and 2 of the trajectory.

If PE(R) is chosen to be zero, then we can compute PE(infinity) = integral
from R to infinity of GmM/r^2 dr, where G = universal gravitation constant,
m = mass of object, M = mass of earth, and r = distance from center of earth.
Carrying out the integration gives PE(infinity) = GmM/R.  So we have

        .5mV^2 = GmM/R + .5mv^2
or
        V^2 = 2GM/R + v^2

where V = speed at the surface and v = speed at infinity.  If you set v=0 you
get V = Vesc = sqrt(2GM/R), where Vesc = the escape speed from the surface.
Hence,
        V^2 = Vesc^2 + v^2
This is the formula I was using in my earlier note.  It looks like the
Pythagorean Theorem, but it really is a statement of conservation of energy.

To continue, we want to provide sufficient energy to the object, such that
when it essentially has left the influence of the earth and is influenced
mostly by the sun it will have a speed either of 30 km/sec backwards or 12
km/sec forwards, relative to the earth.

In the former case,
        V^2 = 11^2 + 30^2 = 1021, so V ~= 31.95 km/sec

In the latter case
        V^2 = 11^2 + 12^2 = 265, so V ~= 16.28 km/sec

(I made an error in the latter calculation before.  I computed the number
whose value = 12 km/sec as 30/sqrt(2) instead of 30(sqrt(2)-1).  The
incorrect calculation gave a value close to 21 for what should have been 12.
This gave 23.9 km/sec instead of 16.28 km/sec.)

Thus, to launch into the sun, you must provide an object at the surface of
the earth with a speed of 32 km/sec in the direction such that when it is
a long way from the earth but before the sun makes too much difference, it is
moving away from the earth in the opposite direction of the earth's motion
around the sun.  To launch into interstellar space, you provide 16.3 km/sec
of speed in the such that when it is a long way from the earth but before the
sun makes too much difference it is moving away from the earth in the same
direction the earth is moving around the sun.

I hope this helps you understand my posting.

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

Dave Dodson                                     [e-mail]
Convex Computer Corporation      Richardson, Texas      [phone]

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

Date: 14 Oct 90 23:52:19 GMT
From: eagle![e-mail]  (Jeff Hojnicki)
Subject: Re: You Can't Expect a Space Station to be Cheap

In article <[e-mail]> [e-mail] (Edward V. Wright) writes:
>Let's not mention that the last time NASA built a space station, with
>Skylab, it took less than four years and about $1 billion to do it. Or
>that we could build the equivalent using just one Space Shuttle external
>tank today.  Or that Lawrence Livermore National Labs has devised far
>less costly space stations based on inflatible structures.  Or that NASA
>itself designed 50-man space stations, less than 20 years ago, that could
>be built for less than the cost of the 8-man station proposed today....

There has been a lot of bandwidth lately devoted to the idea of using the
shuttle ETs as habitable structure for a space station.  The LLNL
inflatible modules have also gotten a lot of press.  However, each of
these concepts only accounts for 1 part of a station, the habitable
structure.  Very little discussion has been voiced about the other
important systems needed for a space station.

So, my question is this.  What does the LLNL scenario say about the
following systems:

   - Power system
   - Thermal Control System
   - Communications
   - Propulsion & attitude control
   - Data management
   - etc.

And while we are on the subject, what kind of systems would be used
for the ET station?

Hopefully, this will bring some interesting discussion.

--
 Jeff Hojnicki   |    [e-mail]         |   // //        // //
 NASA/LeRC       |    [e-mail]     |  =====FREEDOM======
 (216)-433-5393  | - - - - - - - - - - - - - - - - - -| // //  () () // //
 "My opinions are my own, don't blame NASA for them!" |

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

Date: 16 Oct 90 18:55:40 GMT
From: swrinde!zaphod.mps.ohio-state.edu!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 10/16/90


                           Galileo Mission Status
                             October 16, 1990

     The Galileo spacecraft's performance continues to be excellent.  Today,
via the spacecraft 's stored sequence, the telemetry data rate was
automatically increased from 40 bps to 1200 bps.  This was the first
opportunity based on link predictions to operate at 1200 bps since post-Venus
flyby. However, ground data lock-up was unsuccessful due to use of the
34-meter station in Australia.  Station coverage was recently altered to
provide 70-meter coverage for Ulysses.  However, several minutes later, as
planned, the spacecraft was configured back to 40 bps with successful data
lockup.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 18 Oct 90 02:33:37 GMT
From: sdd.hp.com!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!dsinc!netnews.upenn.edu!vax1.cc.lehigh.edu!lehigh.bitnet![e-mail]
Subject: PLUTO AND PIONEER 10

To elaborate, Pioneer 10 or 11 (or the Voyagers), didn't go on to Pluto
because they took trajetories which concentrated their studies on the
satilities of Saturn (for Pioneer 10 and 11 and Voyager 1) and of
Neptune for Voyager 2.  Therefore they couldn't get into the correct
trajetory to whiplash the probe into an intersecting orbit with Pluto.
I was disappointed myself since I believe Pluto should have been
elected instead of the small moons of these planets.  Also Pluto didn't
become interesting till about 1985 which ruled out all but Voyager 2.

Anyhow, according to the newsletter published by "The Planetary
Society" there is a plan to attach a small phobe on a bigger probe
which is heading for Jupiter or Saturn (I forget which one).  This
smaller probe would whiplash around the planet to Pluto ending up there
sometime around 2015 or so.

Chip Kerchner

P.S. Is anyone out there from Univ of Arizona?  If so, could you send
me some electronic info on the PhD program in Computer Science and a
bit about courses dealing with Astronomy.  Mail to: [e-mail].

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

Date: 18 Oct 90 23:00:11 GMT
From: agate!bionet!uwm.edu!caen!sdd.hp.com!elroy.jpl.nasa.gov!forsight!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 10/18/90


                        MAGELLAN STATUS REPORT
                           October 18, 1990

     The Magellan spacecraft has completed its 243rd orbit.  The 7 star
calibrations and 2 desaturations of the past 24 hours were successful with
nominal attitude updates.

     All spacecraft systems are performing as expected while controllers
continue to analyze the relationship between the gyro miscompares and the
solar array drive position errors.  It is possible that the spacecraft has
developed a slight "shimmy," but the performance of the AACS (Attitude and
Articulation Control Subsystem) for pointing the radar antenna and keeping
the solar panels oriented to the sun is nominal.

     Final testing of the Superior Conjunction control sequences produced
some changes and the command upload is expected later today.

     The radar system continues to operate normally, but there is still some
degradation which may be due to the approach to Superior Conjunction.
Several tests are planned and some temporary modifications to data processing
methods are being considered to alleviate the adverse effects of the degraded
data quality.

     The primary SAR (Synthetic Aperture Radar) processor is out of operation
because of the failure yesterday of the input/output computer.  Initial
diagnosis and repair was started yesterday, and completion is expected late
today.

     The Image Data Processing System is processing 13 mosaics to be used for
scientific analysis and assess the radar system performance.  Test altimeter
swaths for orbits 604 and 605 were successfully processed.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 19 Oct 90 00:23:09 GMT
From: munnari.oz.au!metro![e-mail]  (Tim Bedding)
Subject: Re: Magellan/Venus Info

From article <[e-mail]>, by [e-mail] (Ron Baalke):
>
> ... since Uranus and Pluto are both rotating on their sides at about
> 90 degrees ...

Do you have a reference for that statement on Pluto?
How did they find out?  Surely not by radar.

Tim Bedding
Dept of Astrophysics
Uni of Sydney

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

Date: 18 Oct 90 21:07:11 GMT
From: agate!linus!philabs!briar![e-mail]  (Robert Casey)
Subject: Re: Where is 0 longitude, was re: Venus/Magellan, poles

In article <901017.113902.EDT.JEFF@UTCVM> [e-mail] (Jeffrey R Kell) writes:
>One of the (more) unbelievable parts of "Close Encounters" (and others)
>was the use of our latitude/longitude co-ordinate system.  While latitude
>can be inferred (or at least argued over as of late) what basis (if any)
>is there for longitude?

I suppose that you could, in your Sci-fi story, have the ETs watch our TV
broadcasts, and have them see us show a map of the earth with the Greenwich
longitude drawned on it.  Like in a show on geography.  But we're reaching for
it here  :-)
-----------------------------------------------------------------------------
  __/\/\__
     o o     My job is so secret, even I don't know what I'm doing!
      -

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

Date: 19 Oct 90 02:37:53 GMT
From: eagle.wesleyan.edu![e-mail]
Subject: Theories needed on life

Could someone theorize on what humanoid life would be like on a planet 3 or 4
times the size of the Earth.  I'm looking for theories on body structure,
societies, technology, psychology, etc.  Thanks, I appreciate any speculation.

                    dml

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

Date: 19 Oct 90 03:00:06 GMT
From: wuarchive!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Voyager Update - 10/18/90


                         Voyager Status Report
                            October 18, 1990

                              Voyager 1

     The Voyager 1 spacecraft collected routine UVS (Ultraviolet Spectrometer)
data on sources HD30614, HD217675 and HD27778.  On October 8, one frame of
high-rate PWS (Plasma Wave) was recorded. A TLC (Tracking Loop Capacity)
was uplinked over the 70 meter antenna in Spain and completed over the 34 meter
antenna in Australia.


                              Voyager 2

     The Voyager 2 spacecraft collected routine UVS data on sources
PKS2155-304 and EG165.  On October 9, one frame of high-rate PWS was recorded.
Outages of 40 minutes and 1 hour 54 mintues occurred at the 34 meter antenna
at Australia due to heavy rains on October 7 and 8.


                 CONSUMABLE STATUS AS OF 10/18/90

      P R O P E L L A N T    S T A T U S        P O W E R
            Consumption
            One Week   Propellant Remaining   Output   Margin
Spacecraft     (Gm)           (Kg)            Watts    Watts
 Voyager 1       5          36.3 + 2.0         367      55
 Voyager 2       6          39.4 + 2.0         370      61

      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

End of SPACE Digest V12 #470
*******************