Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_5/V16NO515.TXT

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Date: Mon,  3 May 93 05:04:15
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #515
To: Space Digest Readers
Precedence: bulk


Space Digest                Mon,  3 May 93       Volume 16 : Issue 515

Today's Topics:
                    Drag-free satellites (2 msgs)
                        HST Servicing Mission
             HST Servicing Mission Scheduled for 11 Days
                   moon image in weather sat image
                             Project Help
         U.S. Government and Science and Technolgy Investment

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

Date: 2 May 93 14:56:37 PST
From: [e-mail]
Subject: Drag-free satellites
Newsgroups: sci.space

On Sat, 1 May 1993 23:13:39 GMT, [e-mail] (Henry Spencer) said:

> No.  A "dragless" satellite does not magically have no drag; it burns fuel
> constantly to fight drag, maintaining the exact orbit it would have *if*
> there was no drag.

     Well, almost. It turns out that clever orbital mechanics can
engineer things so that resonant interactions with the higher order
harmonics of the Earth's gravitational field can pump energy into a
satellite, and keep it from experiencing drag effects for periods of
months to years.

     My favorite example of this is the Soviet/Russian heavy ELINT
satellites of the Cosmos 1603 class, which are in 14:1 resonance. In
particular, C1833 has undergone two periods of prolonged *gain* in
altitude, the current one having started in June 1991; the mean altitude
of the satellite is now as high as it has ever been since launch on 18
March 1987. (Looking at the elements for C1833 also shows the
limitations of NORAD's software -- but that's another story.)

    This probably has little relevance to space stations, since the 71
degree orbits of the C1603 satellites are at 850 km, which is
unacceptably far into the inner van Allen belt for manned platforms. But
it's kind of interesting from the point of view of the physics of the
situation.

    (Orbital elements for these satellites are available on request.)


Allen Thomson                  SAIC                       McLean, VA
----------------------------------------------------------------------
Is there an opinion here? If so, it's mine, not SAIC's

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

Date: 2 May 1993 22:29:07 GMT
From: Isaac Kuo <[e-mail]>
Subject: Drag-free satellites
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>On Sat, 1 May 1993 23:13:39 GMT, [e-mail] (Henry Spencer) said:
>
>> No.  A "dragless" satellite does not magically have no drag; it burns fuel
>> constantly to fight drag, maintaining the exact orbit it would have *if*
>> there was no drag.
>
>     Well, almost. It turns out that clever orbital mechanics can
>engineer things so that resonant interactions with the higher order
>harmonics of the Earth's gravitational field can pump energy into a
>satellite, and keep it from experiencing drag effects for periods of
>months to years.

A harmonic of the Earth's gravitational field?  What IS a harmonic of the
Earth's gravitational field?

>     My favorite example of this is the Soviet/Russian heavy ELINT
>satellites of the Cosmos 1603 class, which are in 14:1 resonance. In

14:1 resonance with WHAT?  It's not like there's any wavelength or frequency
to the Earth's gravitational field.  Now, there' might be some interesting
interactions with the Moon's tidal effect--is that what you're talking about?
>
>    This probably has little relevance to space stations, since the 71
>degree orbits of the C1603 satellites are at 850 km, which is
>unacceptably far into the inner van Allen belt for manned platforms. But
>it's kind of interesting from the point of view of the physics of the
>situation.

What are the physics of the situation?  The only way I can see gravitational
effects being useful in adding energy to an object orbiting Earth is some
sort of interaction with the moon.
--
*Isaac Kuo ([e-mail])    *       ___
*                    * _____/_o_\_____
*    Twinkle, twinkle, little .sig,    *(==(/_______\)==)
*    Keep it less than 5 lines big.    * \==\/     \/==/

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

Date: Sun, 2 May 1993 21:47:16 GMT
From: [e-mail]
Subject: HST Servicing Mission
Newsgroups: sci.space,sci.space.shuttle,sci.astro

In article <[e-mail]>, [e-mail]
(Richard A. Schumacher) writes:

> In <1rs0au$[e-mail]> [e-mail] (Pat) writes:
>
>>How different would the contamination threat of a small manuevering tug
>>be from that of the Shuttle and it's OMS engines??????
>
> The aperture door will be shut during reboost. Using the shuttle
> means that there will be someone nearby to pry the door open again
> if it should stick.
>

Well, no, during the original deployment mission the HST aperture door was
not opened until after the Shuttle had landed.

I presume that during a re-boost mission HST would be berthed in the orbiter
with the orbiter bay doors shut; but still there would be lots of contamination
worries.  I understand that the EVA suits are one of the hardest things to
keep clean.

But I still don't know where the idea is coming from that HST _NEEDS_ a
re-boost.  We have many problems but our orbit is the least of them.  There
is certainly no plan to change the orbit in the first servicing mission in
December.

Ben

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

Date: Sun, 2 May 1993 22:25:00 GMT
From: David Ward <[e-mail]>
Subject: HST Servicing Mission Scheduled for 11 Days
Newsgroups: sci.space,sci.space.shuttle,sci.astro

In article <[e-mail]>, [e-mail] (David M. Palmer) writes...
>
>You may want to put Hubble back in the payload bay for a reboost,
>and you don't want to clip off the panels each time.

The "artist renderings" that I've seen of the HST reboost still have
the arrays fully extended, with a cradle holding HST at a ~30 degree
angle to the Shuttle.  I think the rendering was conceived before the
array replacemnet was approved, so I'm not sure if the current reboost
will occur with the arrays deployed or not.  However, it doesn't
appear that an array retraction was necessary for reboost.
>
>For the Gamma-Ray Observatory, one of the design requirements was that
>there be no stored-energy mecahnisms (springs, explosive squibs, gas shocks,
>etc.) used for deployment.  This was partially so that everything could
>be reeled back in to put it back in the payload bay, and partially for
>safety considerations.  (I've heard that the wings on a cruise missile
>would cut you in half if you were standing in their swath when they opened.)
>

Thanks for the input on GRO's S/A design constraints.  That would
explain the similar design on UARS.

>Back when the shuttle would be going up every other day with a cost to
>orbit of $3.95 per pound :-), everybody designed things for easy servicing.
>

Heck, the MMS project used to design _missions_ with servicing in mind.
The XTE spacecraft was originally designed as an on-orbit replacement
for the instrument module on EUVE.  That way, you get two instruments
for the price of one spacecraft bus (the Explorer Platform).  A
second on-orbit replacement was also considered, with the FUSE telescope.

>--
>        David M. Palmer        [e-mail]
>                    [e-mail]

David W. @ GSFC

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

Date: 3 May 93 00:08:27 GMT
From: Melissa Sherrin <[e-mail]>
Subject: moon image in weather sat image
Newsgroups: sci.astro,sci.space,sci.geo.meteorology,sci.geo.geology

I'm afraid I was not able to find the GIFs... is the list
updated weekly, perhaps, or am I just missing something?

   _______
  (       )
 (_  (     )
   (      )
  (    )  )
 (  (     )
(__________)
 / / / / /
 Melissa Sherrin
 [e-mail]

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

Date: 2 May 1993 21:24:05 GMT
From: Stephen Amadei <[e-mail]>
Subject: Project Help
Newsgroups: sci.space

Hello,

I am new to this news group, but I need some info.  I am
currently doing a project for a class on the Internet.  I am
looking for good sources of information on space and astronomy,
more notably, our own solar system.  If anyone knows any good
sites where I can get information about this kinda stuff, please
e-mail me at [e-mail].  Thanx.

                                ----Steve

(my newsreader doesn't have a .sig yet, sorry.)
--
Please Address repondes to [e-mail]
                                     or
                           [e-mail]

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

Date: Sun, 2 May 1993 18:53:18 GMT
From: Herman Rubin <[e-mail]>
Subject: U.S. Government and Science and Technolgy Investment
Newsgroups: sci.space,talk.politics.space,sci.research,talk.politics.misc,talk.politics.libertarian,misc.education

In article <[e-mail]> [e-mail] writes:
>People who criticize "big Government" and its projects rarely seem to
>have a consistent view of the role of Government in science and
>technology.  Basically, the U.S. Government has gotten into the role of
>supporting research which private industry finds too expensive or too
>long-term.

>(Historically, this role for the U.S. Gov't was forced upon it because
>of socialism in other countries.  In order for U.S.  industries to
>compete with government-subsidized foreign competitors, the U.S. Gov't
>has taken on the role of subisizing big-ticket or long-lead R&D.)

This definitely had nothing to do with the entry of the government into
the support of science; some of it is relevant in technology.  There
was little involvement of federal funds, or except through support of
state universities, of state funds, for scientific research before WWII.
The US research position had been growing steadily, and the funding was
mainly from university and private foundation funds.  There were not that
many research universities, but they all provided their researchers with
low teaching loads, laboratories, assistants, and equipment, and funds for
travel to scientific meetings.  Not that much, but it was provided, and a
university wishing to get a scholar had to consider research funding as well
as salary.

During WWII, the military and the defense departments found that pure
scientists could do quite well with their problems, even though they
were not exactly in the areas of the scientists' expertise.  This is
probably because of the "research mind" approach, which is not to try
to find a solution, but to understand the problem and see if a solution
emerges.  This works in stages, and as research scientists were used to
discussion about their problems, the job got done.

The military realized the importance of maintaining scientists for the
future, and started funding pure research after WWII.  But Congress was
unwilling to have military funds diverted into this investment into the
future supply of scientists, and set up other organizations, such as
NSF, to do the job.  It also set up an elaborate procedure to supposedly
keep politics out.  Also, the government did a job on private foundations,
making it more difficult for them to act to support research.

The worst part of the federal involvement is that in those areas in which
the government supports research the university will not provide funding,
and in fact expects its scholars to bring in net government money.  Suppose,
as has been the case, I have a project which could use the assistance of
a graduate student for a few months.  What do you think happens if I ask
for one?  The answer I will get is, "Get the money from NSF."  Now the
money at the university level is a few thousand, but at the NSF level it
comes to about 20 thousand, and is likely to keep a faculty member from
getting supported.  So the government is, in effect, deciding which projects
get supported, and how much.

Also, the government decided that the "wealth" should be spread.  So instead
of having a moderate number of universities which were primarily research
institutions, the idea that more schools should get into the act came into
being.  And instead of evaluating scholars, they had to go to evaluating
reseach proposals.  As a researcher, I can tell you that any research proposal
has to be mainly wishful thinking, or as now happens, the investigator conceals
already done work to release it as the results of the research.  What I am
proposing today I may solve before the funding is granted, I may find
impossible, or I may find that it is too difficult.  In addition, tomorrow
I may get unexpected research results.  Possibly I may bet a bright idea

which solves yesterday's too difficult problem, or a whole new approach to
something I had not considered can develop.  This is the nature of the beast,
and except for really vague statements, if something can be predicted, it
is not major research, but development or routine activity not requiring
more than minimal attention of a good researcher.

I believe that at this time less quality research is being done than would
have happened if the government had never gotten into it, and the government
is trying to divert researchers from thinkers to plodders.
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: [phone]
[e-mail] (Internet, bitnet)
{purdue,pur-ee}!snap.stat!hrubin(UUCP)

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End of Space Digest Volume 16 : Issue 515
------------------------------