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Subject: SPACE Digest V11 #263

SPACE Digest                                     Volume 11 : Issue 263

Today's Topics:
              Galileo Update - 04/13/90
               Re: Interstellar travel
            Re: Silo Launches etc.
          Re: Pegasus launch from Valkyrie  (or ...
        Re: releasing data / digitized images
        Re: releasing data / digitized images
            Re: Silo Launches etc.
----------------------------------------------------------------------

Date: 15 Apr 90 08:36:03 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 04/13/90


                              GALILEO
                       MISSION STATUS REPORT
                          April 13, 1990

     As of noon Friday, April 13, 1990, the Galileo spacecraft is 85,179,540
miles from the Earth, 14,722,470 miles from Venus and traveling at a
heliocentric velocity of 76,850 miles per hour.  Round trip light time is 15
minutes, 10 seconds.  The spacecraft is in cruise mode-dual spin with a spin
rate of 3.15 rpm.  The spacecraft attitude sun point angle is 0.7 degrees.
Telemetry rate is at 40 bits/second through the Low Gain Antenna (LGA-1).

     The sequence memory load for the first portion of the Trajectory Course
Maneuver (TCM-4A) was transmitted and received without incident on April 8.
A SITURN to lead the sun was successfully performed on April 8 in preparation
for the TCM-4A maneuver execution on April 9.  The SITURN magnitude was
selected to provide a near sun-pointed attitude at the start of the maneuver.
Another SITURN to lead the sun was successfully performed on April 13 after
completion of all manuever activities. The first portion of TCM-4A was
successfully completed on April 9. Preliminary assessments indicate that
spacecraft performance, in general, was well within predicted limits.  For
the first three burn segments, the total system performance was excellent.
During the last three burn segments, some increases in pointing error were
observed reaching about 11.5 mrad at the end of the final burn (well within
predictions).  This pointing error was subsequently reduced to about 1 mrad
via a sequence planned pointing correction.  It was further observed during
this same period that the DC bus imbalance measurement increased about 1.5
volts (12 DN) to near 19 volts.  When firing was completed, the DC bus
imbalance measurement returned close to its initial pre-burn value; no
significant change was noticed on the AC imbalance measurement.

     The RPM L-thruster temperature profiles observed during the first burn
segment were lower than predicted and reached a peak of about 158 degree C
and 135 degree C for the L1B and L2B, respectively (predicted level up to
170 degree C).  Very early into the second burn segment, the L2B temperature
measurement went to a saturated reading of 255 DN.  The measurement appeared
instantaneously to go from the expected 115 DN to 255 DN. This profile
characteristic is similar to that seen during TCM-1 when the Z1A temperature
instantaneously went to 255 DN indicating a likely transducer failure. It is
important to remember that the thruster temperature transducers were added late
in the program to provide additional thruster thermal visibility and were
installed using an unqualified attachment method and their installation was
accepted by the project on a "best-effort" basis.

     The sequence memory load for the second, third and fourth portion of
TCM-4A were transmitted and received without incident on April 9, 11, and 12,
respectively.

     The second maneuver portion of the TCM-4A was successfully completed on
April 10. Prior to the start of burns in this portion, a SITURN was performed
as planned to bring the spacecraft to a near sun-pointed attitude. Spacecraft
performance was again within predicted levels, however, some performance
differences were observed from the first maneuver portion on April 9.
Significant differences included a larger cumulative pointing error (almost
18 mrad vs 11 mrad after the last burn segment) but still within the predicted
range. In addition RPM tank pressures were about 0.2 bar lower than predicted.
The pointing error was subsequently corrected to near one-half mrad with a
planned sequence pointing correction.  The DC imbalance measurement during the
second portion again exhibited a profile similar to that observed during the
first portion and again very little change was reported in the AC imbalance
reading.

     The third portion of TCM-4A was successfully performed on April 11.
Similar to the second portion, a SITURN was performed prior to the burn.
Pointing errors continued to exhibit some unexplained growth during this
portion. The cumulative error after the first three burn segments was about
18.2 mrad.  A planned correction was performed reducing the error to about
1 mrad prior to the start of the next three burn segments.  The next three burn
segments caused a cumulative pointing error of about 22 mrad.  The planned
pointing correction near the end of the sequence reduced the error to near 3
mrad.  During this third portion, the RPM tank pressures were observed to be
about 0.4 bar lower than predictions but well within acceptable performance
limits. The L1B thruster temperature profile was nearly identical to that
observed in maneuver portions one and two and well within predicted levels.
The DC and AC bus imbalance measurements during this portion changed only 1 DN
significantly different from the 12 DN range observed in maneuver portions one
and two.

     The fourth and last portion of TCM-4A was successfully performed on April
12.  Similar to portions two and three a SITURN was performed prior to the
start of the burn activity.  The cumulative pointing error at the end of first
three burn segments was 20.2 mrad which was corrected to approximately 2 mrad
via the sequence planned pointing correction prior to the start of the fourth
burn segment.  At the end of the sixth portion the pointing error was 23.2
mrad.  This error was corrected down to about 4 mrad via the planned sequence
pointing correction.

     RPM tank pressures gradually dropped from 17.6 to 17.0 bar during burn
segments, a little lower than predicted levels.  Once again the L1B thruster
temperature was stable near 158 degree C similar to all other burn segments.
The DC and AC imbalance measurements remained very stable throughout this
maneuver portion varying about one DN.

     Preliminary Navigation Analysis has indicated that the TCM-4A imparted
very near the required delta velocity (24.8 m/sec) with a slight total under
burn of about 0.48 m/sec (1.7 sigma). Despite pointing error changes, RPM
tank pressures being a little lower than predicted in some segments, and the
apparent loss of the L2B temperature transducer, the spacecraft system
performance was good throughout the four-day, 24-segment burn manuever. This
is the first time that the L-thrusters have been used exclusively for a large
delta velocity burn.  The number of L-thruster pulses in the TCM-4A was more
than 10 times the number used to date for the entire mission.  It is very
possible that the performance changes observed could be attributed to
prediction modeling fidelity of this "new" operating condition.

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

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

Date: 13 Apr 90 17:27:18 GMT
From: elroy.jpl.nasa.gov!aristotle![e-mail]  (Peter Scott)
Subject: Re: Interstellar travel

In article <[e-mail]>, [e-mail] (Nick
Kline) writes:
> So what is the Fermi Paradox?  Is this the equation where you try
> to estimate various factors which relate to the chances of intelligent life,
> like say % of suns with planets, % with life, % with intelligent life,
> % with life that doesn't destroy itself, similar in scope to the equation in
> Cosmos, by Carl Sagan?

Nope, that's the Drake equation.  The Fermi paradox basically says,
"Where is everybody???"  The Drake equation suggests that the galaxy should
be teeming with life, given the number of stars we have.  *Our* presence
as a technological society can readily be detected within a 50ly radius;
yet we have found no signs, similar or other, that life exists elsewhere in
the universe.  Speculation as to why this is the case runs rampant and I
refer you to some excellent pop science discussions of same in _Analog_.

This is news.  This is your       |    Peter Scott, NASA/JPL/Caltech
brain on news.  Any questions?    |    ([e-mail])

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

Date: 13 Apr 90 17:29:16 GMT
From: [e-mail]  (Dean F. Kling)
Subject: Re: Silo Launches etc.

>What about the operational silos at the bases? I remember hearing that a
>Titan II had exploded in a test launch from an operational silo thus putting
>an end to them, is this my faulty memory ? Also there was a report a
>while back of an accidental Titan II launch. Is this an urban legend or
>is there some truth to it?

  Several years ago there was an accidental explosion in an operational Titan
silo (I think in Arkansas) which resulted in the warhead being "launched"
into a nearby potato field.  As I recall the root cause of the accident was
a very large socket (and maybe wrench) being dropped inside the silo, falling
dozens of feet, rebounding off a structural member and puncturing the fuel
tank.  Some time later, the spilled fuel/fumes exploded, destroying the silo.

  There was a follow up sometime later on "60 Minutes" which focused on an
enlisted airman who, after preforming heroics to combat the accident, was
punished by the AF for violating nuclear weapons access rules ( e.g. Two
Man Rule for access to a weapon).

  I don't believe any of this involved an attempt to do a test lanunch for the
same reasons as Minuteman, the first stage has to come down somewhere unpleasant
for launch azimuths with acceptable impact points.

                Dean
                [e-mail]

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

Date: 14 Apr 90 06:32:49 GMT
From: skipper![e-mail]  (Mary Shafer (OFV))
Subject: Re: Pegasus launch from Valkyrie  (or ...

In article <[e-mail]> [e-mail] (john.a.welsh) writes:

>We have seen here that if you want to launch more with a Pegasus,
>you need more speed in the booster plane.  There is only 1 B70
>left, and I don't think the Airforce Museum in Dayton will let
>anybody use it (who would certify it air worthy, too?).

Somehow, I don't think that flying a stainless steel airplane
that's sat outside at Wright-Patterson, in the rain and snow,
for over a decade is a real good idea.  I saw the rust weeping
from it.

>So how
>about the next fastest bomber, the B58?  Were they all broken
>up or are there other museum pieces around (other then Dayton's)?

When last I looked, there was a B-58 sitting on the lakebed just
off Mercury Drive here at Edwards, destined for the museum.  Of
course it's sat outside at Edwards, in the rain and snow, for over
a decade, but we have a lot less rain and snow and it's not stainless
steel, so it's probably a better idea.

>A B58 held the coast to coast record that the SR71 broke (LA - NY
>in about 2 hours) and they were in regular airforce service, so
>they were not experimental oddities.  They had external pods so
>they could carry more than their bomb bays could hold, though I
>am not sure if they could go supersonic with the pods (I think
>they could).  If we are discussing B70s here, why couldn't we have
>a B58 launch Pegasus?

The only drawback I see at first glance is that the B-58 is too close
to the ground.  The gear wouldn't touch if there was a Pegasus under
the wing.

But this is also true of the F-111 and someone proposed a mag-lev cart
for takeoff.  I believe that a largish fighter has taken off using a
ground-effect cart, rather than gear (although I can't confirm this
'til Monday, when I get to work and references).

Or you could put gear on Pegasus.

Or use fall-away gear like the outriggers on the U-2.

Actually, I thought that a large, high-wing plane like the C-5 or
C-141 would be the easiest to modify, but they're so _slow_.

--
Mary Shafer  [e-mail]  ames!skipper.dfrf.nasa.gov!shafer
         NASA Ames Dryden Flight Research Facility, Edwards, CA
                   Of course I don't speak for NASA

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

Date: 16 Apr 90 01:45:33 GMT
From: att!cbnewsh![e-mail]  (lawrence.m.geary)
Subject: Re: releasing data / digitized images

In article <[e-mail]> [e-mail] (Mary Shafer (OFV)) writes:
>
>I've got to ask; my curiosity has gotten the best of me/
>
>Why do readers of this group want images and data from HST?  Research?
>Pretty pictures?  A new display on an idling Mac or Sun?  (There's a
>moon picture that very popular here for this last use.)

I don't want digital data. I have no use for it. However, the *impression*
I have is that, while Voyager images were broadcast live over NASA Select
and were immediately available to everyone, HST images (digital or any
other form) will be hoarded for a year or more by investigators; that
maybe sometime down the road we'll get a postage stamp sized image in
Sky&Telescope or an occasional article in the newspaper, but that otherwise
the torrent of new discoveries will be unavailable outside of esoteric
academic journals.

I don't know about you, but the information released to the press by NASA
last summer during the Voyager encounter with Neptune made me feel like a
participant in the discovery process. It felt great! If NASA broadcast a
15 minute daily summary of HST news and images, and if it was available to
us in some way, I'd be really happy. But we all know the news media will
be tired of HST in a week or two, and if there isn't some other way of
getting the images we'll be cut off and locked out of the process.

Probably we should think of HST as just another big telescope; after all,
nobody is demanding an archive of images from the Hale telescope on Palomar,
are they? But because it's a NASA spacecraft, some of us are looking forward
to a 15 year long "encounter". Maybe we shouldn't.

--Larry
--

     --Larry: [e-mail]

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

Date: 13 Apr 90 21:29:53 GMT
From: skipper![e-mail]  (Mary Shafer (OFV))
Subject: Re: releasing data / digitized images


I've got to ask; my curiosity has gotten the best of me/

Why do readers of this group want images and data from HST?  Research?
Pretty pictures?  A new display on an idling Mac or Sun?  (There's a
moon picture that very popular here for this last use.)

I haven't seen any reason except easy pretty pictures, but surely you
have other good reasons to want them.  (There's nothing wrong with just
_wanting_ them, BTW, or with wanting pretty pictures.)

I'm sure that everyone on this group knows that you can borrow large
negatives/transparencies of virtually all of the pretty pictures from
Apollo, etc, from the NASA Archive.  I had some beautiful prints made
of the Moonrise and Whole Earth.  The borrowing is free, but you have
to have the prints made.  I also suspect that it may be a while before
HST photos are available.


--
Mary Shafer  [e-mail]  ames!skipper.dfrf.nasa.gov!shafer
         NASA Ames Dryden Flight Research Facility, Edwards, CA
                   Of course I don't speak for NASA

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

Date: 13 Apr 90 01:09:53 GMT
From: vsi1!hsv3![e-mail]  (Mike Van Pelt)
Subject: Re: Silo Launches etc.

In article <[e-mail]> [e-mail] (Nick Watkins) writes:
>What about the operational silos at the bases? I remember hearing that a
>Titan II had exploded in a test launch from an operational silo thus putting
>an end to them, is this my faulty memory ? Also there was a report a
>while back of an accidental Titan II launch. Is this an urban legend or
>is there some truth to it?

I don't know about the test launch, but some time back, a worker at a
Titan silo in Arkansas dropped a tool, and it punctured the missile's
fuel tank.  Very large explosion as lots of UDMH and nitrogen tetroxide
combine hypergolically... The warhead was found later, some distance
away.

The Titans were decommissioned soon after that, but I don't think this
was the reason; I think the decommissioning was already scheduled.
--
Mike Van Pelt                     Windows + Icons + Mouse
Headland Technology/Video 7       + Pointer == WIMP.
...ames!vsi1!v7fs1!mvp

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

End of SPACE Digest V11 #263
*******************