Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_0/V13_037.TXT

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Subject: SPACE Digest V13 #037

SPACE Digest                                      Volume 13 : Issue 37

Today's Topics:
              Re: US buys Soviet reactor
               Re: Interstellar Travel
             C code for planet locations?
             Re: Salyut 7 burn-up
        Re: LOX/LH2 in the Shuttle Payload Bay
           Condensed Canopus December 1990

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

Date: 10 Jan 91 21:26:50 GMT
From: idacrd![e-mail]  (Robert McGwier)
Subject: Re: US buys Soviet reactor

From article <[e-mail]>, by [e-mail] (Bill Trost,Box 607,ext 640,):
>
> I'm not certain about satellite uses, but nuclear power sources are
> used for long-distance probes (such as _Ulysses_), mostly because
> there ain't that much sun way out, and possibly for reliability
> reasons --- solar cells have to be exposed in order to function and
>
> Bill Trost



Hi Bill:

There is one helluva big difference between an RTG and a full fledged
nuclear reactor.  An RTG has a relatively small amout of (say) PLutonium
encased in special pellet coatings put together is such a way that
they generate heat which makes electricity from thermocouples.  A nuclear
reactor is one where you have quite a bit of nuclear material, not well
protected pieces, in close proximity to each other, just right at critical
mass, spewing out high speed neutrons, and other ugly stuff in order to
produce copious amounts of heat to drive a large electric generator.
This is needed to power really big radarsats, etc.  It wasn't clear
from your posting whether or not this was clear and there does seem to
be some confusion on the net as to the distinction between the two.
There is clearly a lack of seperation of the identity of the two different
things to the general public.

Bob
.

--
____________________________________________________________________________
    My opinions are my own no matter    |    Robert W. McGwier, N4HY
    who I work for! ;-)            |    CCR, AMSAT, etc.
----------------------------------------------------------------------------

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

Date: 9 Jan 91 22:49:18 GMT
From: wang![e-mail]  (Tom Fitzgerald)
Subject: Re: Interstellar Travel

[e-mail] (Henry Spencer) writes:
> (For starflight in particular, it is a mistake to try to
> hurry too much, because probes launched later are quite likely to get
> there sooner due to improved technology.)

I would think that the improved technology would result from all the things
you learned building and launching the earlier probes, meaning that if you
don't launch probe1, then probe2 won't arrive any earlier than probe1 would
have.  It's worth hurrying a little, anyway.

---
Tom Fitzgerald   Wang Labs        [e-mail]
1-508-967-5278   Lowell MA, USA   ...!uunet!wang!fitz

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

Date: 9 Jan 91 21:09:34 GMT
From: vicorp![e-mail]  (Ron Peterson)
Subject: C code for planet locations?

I am interested in generating a graphic display of the planets and moons of
the solar system where the correct position can be plotted for any date
and time in the past, present or future.  I know there is no precise
solution to the n-body problem but is there an approximation that has
been derived?  Or are there tables calculated by NASA?  Would someone please
email me some source code (preferably C but anything will do) or direct
me to a reference?  Thanks!
[e-mail]  or uunet!vicorp!ron

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

Date: 10 Jan 91 00:43:00 GMT
From: research![e-mail]  (A.C.Beresford)
Subject: Re: Salyut 7 burn-up

Since it is already in atmosphere the question has no meaning
It is however an observed fact that re-entring satellites
have been observed at heights of 109Km in the self-luminous
phase. You can model the process approximately both
numerically and analytically ( DG King-Hele Satellite
orbits in an atmosphere) which gives a figure something
like 1 day left by time orbit height = 160Km

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

Date: 10 Jan 91 16:29:54 GMT
From: eagle![e-mail]  (Dave McKissock)
Subject: Re: LOX/LH2 in the Shuttle Payload Bay

>In article <[e-mail]> [e-mail] (Wales Larrison) writes:
>>... what to do if there was a shuttle contingency requiring them to
>>rapidly dump the cryo propellants overboard. ...

and Mr. Spencer answered in article <[e-mail]> ...
>This perfectly begs the question, of course:  why do contingencies require
>dumping cryo fuels from Centaur when no other fuel system carried in the
>payload bay -- including, as far as I know, the cryogenic extended-duration-
>mission pallet -- has ever had provisions for dumping?  If you assume an
>absence of leaks, the balloon tanks are very strong and rigid and present
>no structural-failure hazards as far as I know.  If you assume leaks, you
>are in trouble even with hypergolics, all the more so because the usual
>hypergolics are both corrosive and poisonous.

>So far I'm sticking to my guns:  the exclusion of Centaur from the payload
>bay was the result of superstitious fear in the absence of strong political
>support, not of a rational engineering decision.

Shuttle Centaur would have had approximately 40,000 pounds of fuel on-board.
This load, in addition to the weight of the Centaur structure,
mounting support structure, and the payload, would have exceeded the
return-to-launch-site abort weight restrictrictions of the Shuttle (for
one example).

Hence, the requirement to dump the fuel on the Centaur prior to a
RTLS abort.
--
-----------------------------------------------------------------------
Dave McKissock              [e-mail]
NASA Lewis Research Center, Cleveland Ohio.
Opinions expressed herein probably bear absolutely no resemblance to
the official NASA position.

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

ReSent-Message-ID: <[e-mail]>
Resent-Date:  Wed, 09 Jan 91 09:16:03 EST
Resent-From: Harold Pritchett <[e-mail]>
Resent-To: Space discussion group <[e-mail]>
Date: Wed, 9 Jan 91 13:13 N
From: "Rob A. Vingerhoeds / Ghent State University" <[e-mail]>
Subject: Condensed Canopus December 1990

Here is the condensed CANOPUS for December 1990. There are five articles
condensed or in full and five articles by title only. Some articles are
taken from What's New (Robert L. Park <[e-mail]>, The American
Physical Society). CANOPUS is copyright American Institute of Aeronautics
and Astronautics, but distribution is encouraged. See full copyright
information at end.

-----------CONTENTS --  5 ARTICLES CONDENSED OR IN FULL-----------------

ROE LEAVES THE HOUSE SCIENCE, SPACE AND TECHNOLOGY COMMITTEE!
Whatsnew - can901201.txt - 12/10/90

When Robert Roe (D-NJ) left the Public Works Committee four years ago to
become Chairman of SS&T he made a little speech to a group of science
policy types: "I have," he proclaimed, "gone from the sewers to the stars."
But Wednesday, Roe leaped at the opportunity to go back to the sewers after
the Democrats ousted the infirm and unpopular Public Works Chairman, Glenn
Anderson (D-CA). The influence of SS&T declined under Roe as a result the
Deficit Reduction Act. By authorizing everything, SS&T ceded the real
decision making to Appropriations.

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

GEORGE BROWN JR (D-CA) WILL SUCCEED ROE AS CHAIRMAN OF SS&T.
Whatsnew - can901201.txt - 12/10/90

One of the few members of Congress with a technical background, Brown
fended off a strong challenge from Marilyn Lloyd (D-TN). Brown must now
decide whether he also wants to head the Space Science Subcommittee. There
are several other vacancies on SS&T to be filled, including Chairman of the
Subcommittee on Science, Research and Technology.

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

AUGUSTINE PANEL IS EXPECTED TO RELEASE WIMPY REPORT ON MONDAY.
Whatsnew - can901201.txt - 12/10/90

The Advisory Committee on the Future of the US Space Program has been
described as "the last best hope" for the space program. Its report,
however, which is due out on Monday, will hardly be a bold call for change.
According to the Wall Street Journal, the report will call for development
of a costly new launch vehicle and decreased reliance on the shuttle, plus
a few modest changes in NASA organization.

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

AUGUSTINE COMMITTEE SAYS NASA SHOULD PUT SPACE SCIENCE FIRST!
Whatsnew - can901202.txt - 12/20/90

The Advisory Committee on the Future of the US Space Program confounded
the skeptics by releasing a report that would transform NASA. The panel
ranked space science above space stations, aerospace planes, manned
missions to Mars, and all the other engineering spectaculars on which NASA
has focused. The panel also called for drastic rethinking of the space
station: "We do not believe that Space Station Freedom, as we now know it,
can be justified solely on the basis of the (non-biological) science it
can perform, much of which can be conducted on earth, or by robotic
spacecraft at lower cost." Dependence on the shuttle should be reduced by
developing a new unmanned heavy-lift launch vehicle. But how could the
panel finesse the delicate subject of a manned expedition to Mars--which
President Bush personally established as a goal? The panel wisely proposed
a "go-as-you-pay" plan, under which the schedule for the mission to Mars
would be determined by the availability of funds.

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

ULYSSES NUTATION MAY CAUSE DATA PROBLEM
can901203.txt - 12/21/90
Dec. 18, 1990

The Ulysses solar polar mission is facing a loss of data from an unexplained
wobble that engineers are having trouble isolating.

The wobble in the spacecraft's rotation that has been present since Nov. 4
has steadily decreased from about 6 degrees side-to-side to a current value
of about 3 degrees side-to-side during the last week of November as a
greater percentage of the spacecraft's axial boom moves into the shade and
as the spacecraft's distance from the Sun increases. Project officials
believe that solar heating of the axial boom exacerbates the wobble. They
do not anticipate any immediate actions to attempt to reduce the wobble,
but rather plan on watching its behavior over the next weeks as the axial
boom moves into more complete shade. The 7.5-meter (24.3-foot) boom is used
as an antenna for the mission's Unified Radio and Plasma-Wave experiment.

However, in response to media queries, program officials conceded that 10
percent or more of the mission data could be lost if the wobble causes problems
in pointing Ulysses at Earth tracking stations during the solar pole flyovers.

Some minor ground problems have occurred as well. A mechanical failure at the
Canberra station cost five hours of playback data. It has also been noted that
when data are being acquired from the Madrid station, the frequency of data
dropouts between the station and JPL is higher than from other stations.

-----------------5 ARTICLES BY TITLE ONLY-------------------------------

HAPPER IS EXPECTED TO BE THE NEW DIRECTOR OF ENERGY RESEARCH!
Whatsnew - can901201.txt - 12/10/90

ERRATUM: WE HAD THE WRONG NORTH CAROLINA CONGRESSMAN MOVING
Whatsnew - can901202.txt - 12/20/90

DID ANYBODY BRIEF THE AUGUSTINE PANEL ON THE BUDGET AGREEMENT?
Whatsnew - can901202.txt - 12/20/90

DOES ASTRONOMY STIMULATE REPRODUCTION OF MT. GRAHAM SQUIRRELS?
Whatsnew - can901202.txt - 12/20/90

IS THE NSF BEING EVICTED FROM THE DOWNTOWN WASHINGTON LOCATION
Whatsnew - can901202.txt - 12/20/90

------------------END OF CONDENSED CANOPUS---------------------------

This posting represents my own condensation of CANOPUS. For clarity, I have
not shown ellipses (...), even when the condensation is drastic. New or
significantly rephrased material is in {braces} and is signed {--RV} when
it represents an expression of my own opinion. The unabridged CANOPUS is
available via e-mail from me at any of the addresses below.

Copyright information:
------------------------------------------------------------------------
CANOPUS is published by the American Institute of Aeronautics and
Astronautics. Send correspondence about its contents to the executive
editor, William W. L. Taylor ([e-mail]). Send
correspondence about business matters to Mr. John Newbauer, AIAA, 1633
Broadway, NY, NY 10019. Although AIAA has copyrighted CANOPUS and
registered its name, you are encouraged to distribute CANOPUS widely,
either electronically or as printout copies. If you do, however, please
send a brief message to Taylor estimating how many others receive copies.
CANOPUS is partially supported by the National Space Science Data Center.
------------------------------------------------------------------------

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

End of SPACE Digest V13 #037
*******************