Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_5/v11_580.txt

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Subject: SPACE Digest V11 #580

SPACE Digest                                     Volume 11 : Issue 580

Today's Topics:
              Re: Full Funding for NASA
           Re: Anyone Know What MOL Is/Was?
         Re: Is there a backup HST mirror ???
           Re: The Scout, Pershing II's and ICBM's
          Re: ESA-brief summary of activity
                 Re: Pegasus
             What Spherical Aberration is
               Re: 10 psi overpressure
         Re: Is there a backup HST mirror ???
             ESA Bulletin no. 62
               F-117 at Oshkosh
               Current status of HOTOL?
                  US on Mars

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

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

Date: Wed, 27 Jun 90 00:31:28 EDT
From: [e-mail] (Keith F. Lynch)
To: eagle![e-mail]
Subject: Re: Full Funding for NASA
Cc: [e-mail], [e-mail]

> I've heard several stories that state that private industry _wants_
> NASA to do the basic research and initial testing, then turn the
> technology over to them for commercial development.

Of course!  Who wouldn't like to have their R&D done for them, at
taxpayer expense?

Let them do their own R&D.  I'll decide for myself where and how to
invest or spend my money, thank you.
                                ...Keith

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

Date: 27 Jun 90 14:21:33 GMT
From: usc!cs.utexas.edu!titan![e-mail]  (Donald Heskett)
Subject: Re: Anyone Know What MOL Is/Was?

It was to have been a small military space station, originally
intended to be serviced by the DynaSoar spaceplane.  Launcher was, I
think, the Titan-II.  Later, in the waning days of the project, as it
was fighting for its life, the transfer craft was changed to a variant
of the Gemini capsule.

The project died because it could not prove it would perform a mission
whose value was commensurate with its cost.  If I remember correctly,
Robert Macnamara (spelling?), Mr. Cost-Effectiveness, was the executioner.

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

Date: 27 Jun 90 17:36:56 GMT
From: zephyr.ens.tek.com!tektronix!percy!3cpu![e-mail]  (Bryce Nordgren)
Subject: Re: Is there a backup HST mirror ???



In article <[e-mail]> [e-mail] (Mark Robert Thorson) writes:
>Now that the HST is safely in orbit, what happens to the backup mirror
>(assuming there was one)?  Will it be auctioned as scrap?

Providing that one does actually exist, it may be sent up to fix the
"spherical aberration" mentioned in another article. ;)

   ---Brycen

PS - I'm a new user and have never posted to this net before.  I tried to
find and view the "nettiquette" document, but the system said we didn't have
the newsgroup that it was in.  Could someone please mail it to me?  I've
really enjoyed the discussion in here, and would like to participate, but
don't want to step on any toes.  Your help is much appreciated.

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

Date: 28 Jun 90 16:12:47 GMT
From: clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: The Scout, Pershing II's and ICBM's

In article <[e-mail]> [e-mail] (Doug Mohney) writes:
>... You would have to buy them as surplus(?). One or two
>of the Titan(s) retired in the early '80s might have been refuburished to
>launch a payload, but I'm not real sure about this.

They are all in storage, and contracts are out to refurbish an initial batch
as launchers.  I don't think they've launched the first one yet.

Doug is correct that you would have to buy them.  They belong to the USAF.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 27 Jun 90 15:32:53 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: ESA-brief summary of activity

In article <[e-mail]> [e-mail] (Donald M. Craig) writes:
>writes: "Beginning on
>19 February, a series of telecommands was transmitted to Giotto via the Madrid
>tracking station, using a 70m antenna and a 100000 W transmitter, many thousand
>times the power of a TV broadcasting station."
>Reaching for my trusty Television and Cable Factbook...
>That's 3 million watts, 5 million watts, and 4 million watts.  Perhaps the
>100000 W number was a typo?

Almost certainly they are talking about *effective* power, i.e. what the
TV station would have to radiate to put the same signal into the receiver
at the same distance.  The tight beam from that 70m dish is equivalent to
a very large increase in output power.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 27 Jun 90 15:30:41 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Pegasus

In article <[e-mail]> [e-mail] (john reece) writes:
>How about using a C-5, or C-17, and building a bigger rocket with a larger
>payload?  Either one can carry twice the payload of a B-52...

Not externally they can't.  You can launch very big rockets from a heavy
transport -- a Minuteman was experimentally launched from a C-5, by pushing
it out the rear, deploying a parachute to stabilize it, and firing the
first stage a few seconds later -- but not ones with *wings*, because they
won't fit.  Pegasus is not a particularly small object except by launcher
standards; I'm not sure its wingspan is small enough to go in a C-5, and
I am fairly sure that nothing much larger would fit.

Also, there are no civil C-5s or C-17s, and OSC/H is a civilian firm, not
another appendage of the military-industrial complex.  Pegasus can be
dropped from a Tristar or 747, and in fact OSC/H plans to acquire or
lease such an aircraft before too long.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 28 Jun 90 02:52:00 GMT
From: uvaarpa!murdoch![e-mail]  (Greg S. Hennessy)
Subject: What Spherical Aberration is


Once more with feeling.

Since HST is apparently suffering from Spherical aberration, and
seeing how lousy the news reports were tonight, I thought I would give
the readers a brief summary of what spherical aberration is.

An "aberration" is a manner in which an image is degraded. There are
five principal aberrations: coma, spherical aberration, astigmatism,
chromatic aberration, and field curvature. It is impossible to get rid
of all of these at the same time, but you try to get them to
acceptable limits. To explain spherical aberration, I will make use of
the principle of reprocitity, which means that instead of light coming
into the telescope, I will use light going out of a telescope.

If you have a point source of light, and want to have a curved surface
to change the radially expanding rays into plane parallel rays, it is
easy to calculate that the proper shape for the mirror is a parabola.
However, if the mirror is a spherical mirror, the rays are not
parallel after being reflected. This means that parallel rays coming
into the mirror (as from a distant star) are not reflected into a
point, but into a fuzzy area. Parabolas do not suffer spherical
aberration. Spherical mirrors do. (Actually all non spherical mirrors
suffer from spherical aberration. Don't ask why it is named such.)

There are many different designs of telescopes. One of the most common
is the Cassegrain, which has a paraboloidal primary, and a hyperbolic
secondary (the shapes are generally conic sections). If you look at a
picture of HST you may think that its optics are Cassegrain, but the
optics are actually a Ritchey-Chretien design. The advantage of the
Ritchey-Chretien is that the field of view is much larger than a
Cassegrain, which is important for HST since it has to have several
instruments collecting light at the same time. The Ritchey-Chretien
has a more relaxed primary than a parabola (i.e. closer to a sphere)
by a few wavelengths. This introduces spherical aberration, but cuts
down on coma by quite a bit. The secondary mirror is modified such
that it will eliminate the spherical aberration from the primary. A RC
telescope does suffer from astigmatism and field curvature. For earth
based instruments, these effects are much reduced if you are on axis,
and for mechanical reasons most instruments are mounted on axis. The
HST has the WF/PC on axis, while all the other instruments are off
axis. Each of these instruments are designed to compensate for
astigmatism and field curvature.

So far I have been factual. I will now begin speculation.

It seems that the secondary mirror of HST was not designed in the
proper shape. Simply moving it around (as they can do) will not solve
the problem. Replacing the primary mirror will not fix the problem,
since it is not the cause. Replacing the secondary should fix it,
except this is impossible. The instruments were designed to be
replaced, but the secondary was not, and they won't bring HST back to
earth. The people who built the mirrors and assembled it apparently
made the mirrors to the specs they were given, but it appears the
specs were incorrect. New instruments CAN be designed to correct for
the spherical aberration, but it will be a few years before this can
happen. The instruments were planned to be replaced anyway in a few
years, this gives us more reason to. It is presently unclear how much
science will be lost, although I heard a quote that the Wide Field
camera is useless for scientific work.

I hope this helps.


--
-Greg Hennessy, University of Virginia
 USPS Mail:     Astronomy Department, Charlottesville, VA 22903-2475 USA
 Internet:      [e-mail]
 UUCP:        ...!uunet!virginia!gsh7w

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

Date: 28 Jun 90 16:09:46 GMT
From: clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: 10 psi overpressure

In article <[e-mail]> [e-mail] (Doug Mohney) writes:
>>>I seem to recall that the charges went in by the SSMEs ...
>>References, please? ...
>This was a post-Rogers, post-Challenger launch. Other than that, I'll have
>to dig through AvWeek to find the reference.

I've been reading AW&ST cover to cover since well before Challenger, and
summarizing it to the net since Challenger, and I recall nothing like that.
I also class this as a very unlikely change for several reasons (not least
of which is that destroying the ET makes a destruct charge on the SSMEs
totally redundant, since they can't do anything without fuel).  I'm afraid
I'm not going to believe it without at least an exact reference.
--
"Either NFS must be scrapped or NFS    | Henry Spencer at U of Toronto Zoology
must be changed."      -John Osterhout |  [e-mail]   utzoo!henry

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

Date: 28 Jun 90 17:53:11 GMT
From: mephisto!prism![e-mail]  (Glenn R. Stone)
Subject: Re: Is there a backup HST mirror ???

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>There is talk of a mission in 1991 -- one had been pencilled in as a
>contingency in case something went badly wrong [....] If
>a replacement WFPC with aberration compensation can be built in haste,
>that might perhaps be done.

I saw a blurb on CNN Headline News this morning that that was the current
plan, i.e.  attempt to finish the WFPC in time for the 1991 launch.
Pity the poor people who have to try to schedule shuttle missions
nowadays; what with the Columbia problem and now this, their scheduling
boards doubtless look like a cross between scrambled eggs and spaghetti.
<sigh> life goes on.

-- Glenn R. Stone
[e-mail]
"Go, baby, go!" -- Walter Cronkite, July, 1969

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

Date: Wed, 27 Jun 90 10:39:15 SET
From: [e-mail]
Comment: CROSSNET mail via MAILER@CMUCCVMA
Comment: File BULL62 TEXT A
Subject: ESA Bulletin no. 62

Subject: ESA Bulletin no. 62 (May 1990)

Here is an overview of the contents of ESA bulletin no. 62.

Articles:
ERS-1: A Contribution to Global Environmental Monitoring in the 1990's
  Description of the ERS-1 mission, the experiments on-board,
  the spacecraft operations and the envisaged results
Focus Earth: Two Landsat images of Greenland and Brittany
La promotion de l'utilisation de Columbus/Foerderung der Columbus-
Nutzung
  French/German article about promotion and marketing concepts for the
  European space station part and the free-flying laboratory
External Servicing of Spacecraft - The Hermes Capability
  Description of external servicing concepts, featuring descriptions
  of the Hermes robotic arm ("HERA") and the design of the EVA suits
  for the European astronauts (500 hPa pressure suits to reduce
  prebreathing times, combination of hard torso and soft limbs)
ESA's Advanced Relay and Technology Mission
  The Artemis spacecraft (planned launch date 1994), featuring
  advanced communication concepts (optical communications between
  geostationary satellites and from Artemis to the low-orbit
  French SPOT-4 satellite, a large inflatable antenna with
  adjustable spot beams, an ion-propulsion system for stationkeeping.
Supernova Remnants and the Exosat Satellite
  Featuring Exosat X-ray observations of Supernovas.
  My favourite quotation: "Unless you happen to be in the immediate
  vicinity, supernovae are a good thing"
The Exosat Database System
  Description of the post-operational activities around the Exosat
  database
The Consultative Committee for Space Data Systems
  Setting up international standards
Mechanical Coolers: An Option for Space Cryogenic Cooling Applications
  Development of cooling systems based on Stirling cycle
  and Joule-Thompson cycle machines
EFSY - The Backbone of ESA's Financial-Control System
  Managing ESA's finances
In Brief
  ESA-USSR Cooperative Agreement
  J-M Luton (former CNES director) appointed new ESA Director General
  Hipparcos survives Solar eclipse
  Giotto reactivated
  Hubble Space Telescope launched
  Dan Quayle visits ESA Headquarters
  Ariane V36 Board of Inquiry
  Establishment of European Astronaut Centre in Cologne (Germany)
  Meteosat-4 tests completed (after noise problems in M-4 detector)

Other News:
  Hermes Development: Mach 3 Ejection seats selected
   Hermes airframe material now aluminium instead of carbon composites
   New orbit injection scheme does not longer require an Hermes
   propulsion module
  Ariane 5: 1st test firing of P230 solid booster with 15 tonnes
   of propellant
   1st Vulcain engine (Ariane 5 main engine) 80% integrated

The ESA Bulletin can be ordered from
  ESA Publications Division
  ESTEC
  Postbus 299
  200 AG Noordwijk
  The Netherlands

Regards, Lutz Massonne

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

Date:         Wed, 27 Jun 90 12:47:34 EST
From: [e-mail]
Subject:      F-117 at Oshkosh


         Just a BTW the F-117 is scheduled to do a fly-by
     at the EAA convention in Oshkosh between 27 July and
     2 August. EAA is trying to talk USAF into a several day
     display.    Source - Sport Aviation, June 1990, page 5.

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

Date: 27 Jun 90 21:32:58 GMT
From: swrinde!zaphod.mps.ohio-state.edu!uwm.edu!ogicse!milton!unicorn![e-mail]  (Worth Henry A)
Subject: Current status of HOTOL?


    Does anyone know what the current status is of the HOTOL launcher? The
last I heard, nearly two years ago, an attempt was being made to form a
private consortium (led, if memory serves, by a real estate holding firm?),
as the British government had cut all support.

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

Date: 28 Jun 90 20:28:58 GMT
From: fed![e-mail]  (Rich Rauscher)
Subject: US on Mars

Does there exist any U.S. Plans for a manned trip to Mars?
I remember hearing Quayle say something about it, and I haven't been
keeping up with this newsgroup.

Thanks, Rich Rauscher
   ____   _    ____    Rich Rauscher, Unix Systems Programmer
  | __ | | |  | __ |   Federal Reserve Board of Governors, Washington, D.C.
  |   |  | |  |   |    [e-mail]
  | | \\ | |_ | | \\   [e-mail]

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

End of SPACE Digest V11 #580
*******************