Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_1/V11_105.TXT

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Date: Sat,  3 Mar 90 02:12:58 -0500 (EST)
Subject: SPACE Digest V11 #105

SPACE Digest                                     Volume 11 : Issue 105

Today's Topics:
     Thiokol wasn't punished (was Re: Fun Space Fact #1)
            Re: Pegasus Update - 03/01/90
              Galileo Update - 02/28/90
            Re: Pegasus Update - 03/01/90
              Re: Challenger Last Words
              Re: Dissassembling the Sun
              Voyager Update - 03/02/90
           Re:  LDEF - Protection from atmosphere?
             Re: Ariane V36: Mission lost
               Re: SPACE Digest V11 #80
----------------------------------------------------------------------

Date: Wed, 28 Feb 90 17:08:01 CST
From: [e-mail] (Lou Adornato)
Subject: Thiokol wasn't punished (was Re: Fun Space Fact #1)

attcan!utgpu!utzoo![e-mail]  (Henry Spencer) writes:

>Very true, alas.  Likewise a system that rewards people for their complicity
>in the disaster.  What, you thought Morton Thiokol was *penalized* for what
>they did?  Ho ho, not so.  They got umpty-million dollars to fix the SRB
>problems, and the notion of an alternate source for SRBs was shelved for
>years.  Isn't that a *wonderful* example for the next time some engineer
>tries to convince his management that they should do the right thing?

I can understand this, even if it seems at first to be counter-intuitive.

Thiokol had more experience than anyone else with the SRB's, and it just
wouldn't make sense to add some other company's learning curve time to the
inevitable program suspension.  As for shelving the secon source SRB supplier,
this was probably necessary to convince Thiokol that it would have to live with
the new design (I've seen the difference between a design done by the same
company that expected to do the fabrication, and one done by an outside agency).
Also, the cost of bringing a second source on line is pretty high, and NASA
had to buy a whole new orbiter.  There's also the matter of whether Thiokol
could have remained solvent through the redesign effort if NASA hadn't made a
commitment (Thiokol stock was probably pretty low at the time).

There's also the fact that Thiokol wasn't really responsible for the accident,
except maybe in that the field joint wouldn't have had to exist if Thiokol was
based in central Florida (the SRB's are jointed so that they can be shipped
by rail).  The accounts that I've read (nope, didn't get a copy of the Rogers
report - anyone know where I can get one?) say that everyone involved knew that
there was a problem with the design of the joint.  There was a _lot_ of evidence
that the primary seal was useless (it died in something like 80% of the time,
leaving the backup seal as the only protection).  It doesn't take a whole lot
of statistical reliability to know that if you're counting on your backup
system most of the time, you have _NO_ true backup capability.

The bottom line is that the NASA managers in Huntsville let the launch become
the primary objective, and forgot thier real job was a safe launch; they should
never have put the Thiokol engineers in the position of having to prove that
the mission was unsafe.  Personally, I don't feel that this is so much an
indictment of NASA as a statement on the behavior of organizations under
pressure.

As to the castigation of Boisjoly, I think it sucks.  The man blew
the whistle before _and_ after the fact.  Saying that he deserves to be
pillloried because he let himself be browbeaten by NASA and his employer is
nonsense.

I also think that it sucks that some people (technophobes) act like NASA
reliability figures are never to be trusted again, and point to NASA's own
"consrevatization" of previously stated figures as proof of this theory.  I was
a kid in a NASA/Contractor neighbohood at the time of the Apollo 1 fire, and it
felt like everyone I knew had lost 3 family members.  You can bet the house that
any NASA manager or engineer would pass a brick before he/she would let another
questionable launch happen.

Lou Adornato    |  Statements herein do not represent the opinions or attitudes
Cray Research   |  of Cray Research, Inc. or its subsidiaries.
[e-mail]    |       (...yet)

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

Date: 2 Mar 90 03:20:11 GMT
From: rochester![e-mail]  (Brian Yamauchi)
Subject: Re: Pegasus Update - 03/01/90

In article <[e-mail]> [e-mail] (Ron
Baalke) writes:

[quoting a NASA press release, I believe]

>     Launch of the Pegasus satellite (Pegsat) has been
>rescheduled for April 4, according to Project Manager Bob Pincus.

>Pegsat will be launched from a NASA B-52 over the Pacific Ocean
>about 50 miles west of Vandenberg Air Force Base, CA.

Is this Pegsat the same as the OSC/Hercules Pegasus launcher?  And if
so, does it make sense to call it a satellite?

_______________________________________________________________________________

Brian Yamauchi                University of Rochester
[e-mail]        Computer Science Department
_______________________________________________________________________________

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

Date: 1 Mar 90 23:48:55 GMT
From: elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 02/28/90



                     GALILEO MISSION STATUS
                        February 28,1990

     The Galileo spacecraft is 48.4 million miles from Earth
today; this distance is still increasing, and will for the next
three months, even though the trajectory leads toward an encounter
with Earth in December.  Round-trip light time is 8 minutes 41
seconds.  The spacecraft passed through perihelion (closest to
the Sun) February 25. Galileo has now gone 226 million of the 2.4
billion miles along its looping 6-year path to Jupiter.

     Health of the spacecraft remains excellent; it is in dual
spin, performing some cruise science data collection and
engineering maintenance functions such as sun-pointing
maneuvers.  The telemetry rate is 40 bits per second; about
March 6 this will go to 10 bits per second consistent with
communications link capability.  Galileo's activities are
controlled by an onboard-stored program or flight sequence
activated February 19 and due to run through March 26.

     Galileo is now committed to encountering the Gaspra
asteroid. The propellant margin estimate is at a negative 17.6
pounds with a 90% confidence. Galileo's thrusters are about 2%
more efficient than expected. The decision to proceed to the Ida
asteroid won't be made until after the Gaspra encounter.

     Galileo's two ultraviolet spectrometers have shown that hydrogen
atoms at Earth's distance from the sun last about 1 million seconds
(almost 12 days) before ionizing. Also, Galileo is already reporting
on the ultraviolet spectra of the star Kappa Velorum and on impacts
by space dust. The largest piece yet detected weighed about one
hundred-millionth of a gram and measured about 26 microns across.

     The next sequence, to run through April 23, is being
processed and reviewed by the flight team.  Like the current one,
the next sequence will include spacecraft maintenance activities
and some cruise science observations; it also includes the first
portion of the trajectory correction maneuver to help shape the
flight path for December's Earth gravity-assist flyby, next step in
propelling Galileo to Jupiter.


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

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

Date: 2 Mar 90 16:47:03 GMT
From: mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Pegasus Update - 03/01/90

In article <[e-mail]> [e-mail] (Brian Yamauchi) writes:
>Is this Pegsat the same as the OSC/Hercules Pegasus launcher?  And if
>so, does it make sense to call it a satellite?

Pegsat is the *payload* for the first Pegasus launch.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 28 Feb 90 16:58:42 GMT
From: snorkelwacker!usc!cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Challenger Last Words

In article <[e-mail]> [e-mail] (Steve Robiner) writes:
>Does anyone out there know if the last minutes of the Challenger
>flight recorder were ever released...

Yes.  It's not interesting.  Apart from some bits of irrelevant chatter
early on, the only thing that's on the recorder tape that didn't get out
on the radio was Smith (probably) saying "uh-oh" just as the accident
started.  Shuttle orbiters do not carry armored flight recorders; this
was just an ordinary tape recorder in the cabin, and it stopped when the
orbiter broke up and power was lost.

The only decisive evidence that the crew survived the breakup -- apart
from the fact that it wasn't violent enough to kill them -- is that some
of the emergency air packs in the cabin had been activated, which is a
manual operation, and is unlikely to be duplicated by flying debris.
(Unfortunately, the packs were meant for ground emergencies, and contained
air rather than oxygen, so they weren't much help at 80,000ft.)
--
"The N in NFS stands for Not, |     Henry Spencer at U of Toronto Zoology
or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry [e-mail]

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

Date: 1 Mar 90 23:07:59 GMT
From: frooz![e-mail]  (Steve Willner, OIR)
Subject: Re: Dissassembling the Sun

From article <[e-mail]>, by
[e-mail] (Paul Dietz):
[Future advanced civilizations may]
>> disassemble the outer planets and then the sun (the latter is
>> the hardest; you need on the order of 10^7 years if you fully utilize
>> the sun's power output; presumably more power could be produced to
>> speed things up).

In article <[e-mail]>, I replied:
> Longer than that, I suspect.  If the Sun were of uniform density, its
> potential energy would be just 1.2 G M^2/R (if I've done the integral
> right).

Nope, I goofed.  Paul correctly points out that the numerical factor in
front should be 0.6 (for the uniform density case).

What happens for the real Sun, which is denser at the center?  Clearly
the factor out front should be larger, but how much?  Paul writes:

>> I deliberately ignored the nonuniform density of the sun.
>> However, the radius goes as density ^ {-1/3}, so even if the
>> sun were a sphere with a uniform density equal to the density at the
>> center (150 grams/cc vs. the mean density of 1.41 grams/cc) the
>> binding energy would be only 4.7 times larger.

i.e., the factor out front cannot be larger than 2.8.

After some browsing around, it seems that for the simplest stellar
models (ideal gas law, uniform chemical composition, hydrostatic
equilibrium), the factor in front would be 1.5.  The factor for the
Sun will be slightly larger, since helium is concentrated toward the
center.  An old reference (that just happens to be handy) gives 2.0,
but also gives a central density of 100, not 150.  Thus it's in fact
not a bad approximation (for computing the potential energy) to say
that the bulk of the mass of the Sun is at a uniform density equal to
the central value.  (Stellar structure pundits are invited to provide
better answers but should probably omit sci.space.)

Another correction that neither one of us considered is the internal
thermal energy of the Sun.  The energy needed to dissipate the Sun to
infinity is the gravitational binding energy _minus_ the thermal
energy.  But according to the virial theorem, the thermal energy is
exactly half the gravitational binding energy.

> The time for the Sun to radiate that amount of energy at its
> current luminosity would be 4E7 years  [or larger]

After the above corrections, it's something like 3E7 years.  Less if
you can get the nuclear energy out faster, (e.g. supernova) longer if
your process efficiency is less than one (don't want to generate lots
of neutrinos, unless you can afford to waste energy).

Incidentally, this same calculation shows that the Solar energy source
cannot be gravitational if you think that the Sun has been shining
(at nearly its current luminosity) longer than 3E7 years.

References:
Allen 1963, _Astrophysical Quantities_, p. 161ff.
Cox and Giuli 1968, _Principles of Stellar Structure, vol. 2_, p. 703ff.
-------------------------------------------------------------------------
Steve Willner            Phone [phone]         Bitnet:   willner@cfa
60 Garden St.            FTS:      830-7123           UUCP:   willner@cfa
Cambridge, MA 02138 USA                 Internet: [e-mail]

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

Date: 3 Mar 90 03:24:38 GMT
From: zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!jarthur!elroy.jpl.nasa.gov!forsight!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Voyager Update - 03/02/90


                     Voyager Mission Status Report
                           March 2, 1990

                              Voyager 1

     Voyager 1 continues to collect routine cruise science data. On February
17, the Magnetometer measured an increase in the magnetic field by a factor
of 2 or more.  The Plasma, CRS, and LECP instruments are not recording any
corresponding change.

     On February 19, an ultraviolet spectrum (UVS) observation was executed
from the source SV Centauri (aka HD 102552). Only the first one and one-half
hours of the five hour data mode period was received due to the lack of Deep
Space Network (DSN) 70-meter support.

     On February 21, the  Attitude and Articulation Control Subsystem (AACS) A
and B gyros were reinitialized.

     Photopolarimter Radiometer (PRA) data is processed and analyzed
data daily for the purpose of observing and logging radio events
of interest to the PRA team.

                              Voyager 2

     AACS Scan Platform Slews on February 19 and February 22 were executed
without downlink visibility due to lack of DSN support.

     A UVS observation was executed on February 21. UVS low-rate data were
taken on sources Feige 7 and EG165, a white dwarf. High-rate data were taken
on EG165 on February 21. Only three and one-half hours of the twelve hour
data mode was observed due to lack of sufficient DSN support.

     Spacecraft performance for all the sequenced activity during this
report period has been nominal.

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

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

Date:     Fri, 2 Mar 90 12:26:19 CST
From: Will Martin <[e-mail]>
To: [e-mail]
Cc: [e-mail]
Subject:  Re:  LDEF - Protection from atmosphere?

>Why should the atmosphere affect the radiation and erosion damage?

Well, I was thinking that the panels and pieces would be in a sort of "raw"
state when retrieved, with the surfaces modified by the years of exposure.  As
soon as oxygen got to those sufaces, they would begin to oxidize.  The
material on the surface would not be the same as it was in space.  Also,
atmospheric pollutants could attack them, destroying or at least modifying the
state they were in after years of exposure to vacuum (at least what level of
vacuum is in LEO) and various space-borne stuff like free ions.

I wouldn't be surprised if various materials migrated because of the vacuum,
or if alloys tended to separate.  There might be a sort of few-atoms-thick
layer of unusual material or pure elements on the surface.  Exposure to air
might destroy that thin layer or modify it into unrecognizability.

I'm not saying all the information would be lost, but some must be.  It is
like retrieving sunken artifacts -- when exposed to air they crumble.  Or the
difference between a slightly-weathered rock face and a freshly-cleaved-off
chunk of mineral sample.  There always is *some* effect of the air.

Will

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

Date: 1 Mar 90 16:59:41 GMT
From: van-bc!ubc-cs!kiwi!dssmv2![e-mail]  (Roger Fischer)
Subject: Re: Ariane V36: Mission lost

In article <[e-mail]> [e-mail] (Neil Dixon) writes:
>...
>At H0+101 s, the high dynamic pressure attained created excessive
>stresses on the structure and triggered the explosion of the launcher
>at an altitude of about 9 km and 12.5 km away from the launch pad.
>...

Do I understand this right? The Ariane did not explode, it disintegrated due
to high dynamic pressure!?!

Roger
----------------------------------------------------------------------------
Roger W. Fischer         [e-mail]         [e-mail]
..seismo!ubc-cs!mprgate!fischer     ...ihnp4!alberta!ubc-cs!mprgate!fischer

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

Date: 1 Mar 90 16:33:45 GMT
From: mcsun!ukc!inmos![e-mail]  (Conor O'Neill)
Subject: Re: SPACE Digest V11 #80

In article <[e-mail]> [e-mail] (Platypi go 'Quack!') writes:
>Does anyone know the coordenats for the center of the Galaxy?
>Including right acclination.
>Tahnks
>[e-mail]


Surely they are (0, 0, 0)


Conor O'Neill, Software Group, INMOS Ltd., UK.
UK: [e-mail]        US: [e-mail]
"It's state-of-the-art" "But it doesn't work!" "That is the state-of-the-art".

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

End of SPACE Digest V11 #105
*******************