Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v11_5/v11_557.txt

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Subject: SPACE Digest V11 #557

SPACE Digest                                     Volume 11 : Issue 557

Today's Topics:
         Re: Aim For The Moon - model rocket contest
              Re: HST crazy idea
               Re: 10 psi overpressure
         Digital Elevation Model of the Moon
         Re: Aim For The Moon - model rocket contest
              Re: HST crazy idea
            Re: Voyager Update - 06/13/90
           Re: Comet Levy tail velocity postscript
            Re: Voyager Update - 06/13/90
                   REQUEST
            BiosphereII (Was RE:Egomania)
                Re: SpaceList
               Re: 10 psi overpressure

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: 21 Jun 90 15:24:45 GMT
From: swrinde!cs.utexas.edu!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Aim For The Moon - model rocket contest

In article <[e-mail]> [e-mail] (Karri Tapani Palovuori) writes:
>The escape velocity is not the velocity needed to escape!
>
>A rocket that would climb 1 m/s would eventually reach the moon (yes, it
>would take some time). Isn't this quite natural?
>
>The escape velocity is the _theoretical_ (starting) velocity that would be
>needed for a bullet to escape the gravity field generated by earth...

However, for rockets with relatively brief burn times, escape velocity is
still a useful approximation to the truth.  The most efficient way to get
off Earth, were it not for the atmosphere, *would* be to accelerate to
escape velocity immediately.  Climbing under power wastes fuel fighting
gravity.  Given the atmosphere, alas, in practice it's necessary to climb
to quite high altitudes before getting into serious acceleration.  The
shuttle, for example, does almost all of its accelerating horizontally
at very high altitude -- to a sloppy first approximation, the basic job
of the SRBs is to get the rest of the shuttle up out of the atmosphere.
(In practice, one optimizes the trajectory for maximum results, and the
SRBs do end up contributing *some* horizontal velocity, but it's not
their primary job.)
--
As a user I'll take speed over|     Henry Spencer at U of Toronto Zoology
features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry [e-mail]

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

Date: 22 Jun 90 12:14:17 GMT
From: usc!samsung!xylogics!merk!alliant!linus!helios![e-mail]  (Cookson)
Subject: Re: HST crazy idea

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]>, [e-mail] (I) wrote:
>>
>> [Fun with orbital mechanics]
>>
>
>It would have to be relaunched to get it there and then you would have to
>work out some way to adjust the longitude so that it would remain
>in this orientation as the earth went around the sun.  I would have to
>brush up on my orbital mechanics to see if this is possible.
>

Oh, I agree it would be a BIG pain in the ass to shift the orbit.  I'm sort
of thinking along thoeretical lines.  Could it be done??

Dean (I don't want to look for my classical mechannics book) Cookson


% Dean Cookson                  $ Anyone can be taught to sculpt    %
% [e-mail]                $ Michaelangleo would have had to %
% {devax,et al..}!linus!mbunix!helios!cookson $ have been taught how not to.  %
% Disclaimer: My opinions are my own, and       $ The same is true of great   %
%       are of questionable sanity                $ programmers               %

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

Date: 22 Jun 90 15:02:39 GMT
From: mojo![e-mail]  (Doug Mohney)
Subject: Re: 10 psi overpressure

In article <[e-mail]>, [e-mail] (Mary Shafer) writes:

>Well, yes and no.  The Shuttle itself has no range safety package;
>deliberate destruction isn't possible.  The SRBs have range safety
>packages, however, and these were activated.

>NASA doesn't put range safety packages on manned vehicles nor on every
>unmanned vehicle.  But I'll concede that putting one on the SRB, which
>is on the Shuttle, looks a lot like putting one on a manned vehicle.

I thought that for some of the Polar launches, they had to put in charges
in the shuttle proper because it would be overflying populated areas.

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

Date: 22 Jun 90 16:36:54 GMT
From: swrinde!zaphod.mps.ohio-state.edu!brutus.cs.uiuc.edu!ux1.cso.uiuc.edu![e-mail]  (Jonathon Sivier )
Subject: Digital Elevation Model of the Moon


   Are there any digital elevation model databases of the moon, similar to the
USGS and DMA data of portions of the earth?  I don't know what kind of
resolution or accuracy you could get but it seems that earth based radar and/or
laser mapping of the equatorial regions of the moon would be fairly easy.

   If anyone knows anything about this sort of thing let me know.  Thanks.

Jonathan

--

Jonathan Sivier
[e-mail]

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

Date: 22 Jun 90 19:58:37 GMT
From: sco![e-mail]  (John DuBois)
Subject: Re: Aim For The Moon - model rocket contest

In article <[e-mail]> [e-mail] (Vincent Cate) writes:
+PS  Has anyone calculated what a space shuttle solid rocket booster is on
+    the "model" rocket scale?  Seems like it will be something like 100 "Z"s
+    but I don't have the data for the SRBs.

     I worked it out once; as I recall they're close to ZZ's.

    John DuBois

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

Date: 21 Jun 90 16:24:22 GMT
From: uoft02.utoledo.edu![e-mail]
Subject: Re: HST crazy idea

In article <[e-mail]>, [e-mail] (Bob Joslin) writes:
> With all the concerns about the HST terminator wobble problems...
>
> Here's a crazy idea that you netters could bat around.
>
> How about sending up a huge shield that could be placed in orbit between
> the telescope and the Sun?  Of course, since this would block sun light to
> the solar panels, I guess some kind of cable would need to run to some
> detached solar panels.  This should work if the wobble problem is due to
> the solar radiation or solar wind, no?  Would the telescope get too cold?
>

They think they can fix the terminator wobble by using the on board
gyros - a much simpler answer.  The other wobble has not been isolated yet.
Dynamically much more feasible.

> Just an idea.
>

Everything starts with an idea...

Robert Dempsey
Ritter Observatory

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

Date: 22 Jun 90 15:04:50 GMT
From: usc!cs.utexas.edu!titan![e-mail]  (Donald Heskett)
Subject: Re: Voyager Update - 06/13/90

I'm just guessing, but I think that the 'margin watts' mentioned in
the Voyager status reports probably represents available power in
excess of the absolute mimimum needed to run the spacecraft. That is,

    margin watts = (present power level) - (absolute minimum)

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

Date: 22 Jun 90 14:20:35 GMT
From: hsi!mlfarm![e-mail]  (Ronald Florence)
Subject: Re: Comet Levy tail velocity postscript

[e-mail] (Tim Roberts) writes:

 > The following is a uuencoded and compressed postscript file of
 > the tail velocity of Comet Levy towards the earth, where 1 = the
 > tail velocity entirely away from earth. This may prove useful for
 > those interested in spectral shifts of ionic emissions.

 [followed by 178K of uuencoded compressed postscript]

Those of us who pay long distance charges for every byte of news, and
especially those who do not own Postscript printers, would appreciate
if you would announce the availability of material like this, and then
make it available for FTP, anonymous uucp, or mail distribution rather
than posting it to every machine on Usenet.

I'm sure the material is interesting.  I only question the posting of
a 178K file which many readers cannot view or print.
--

Ronald Florence            {yale,uunet}!hsi!mlfarm!ron

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

Date: 20 Jun 90 09:23:05 GMT
From: mcsun!ukc!inmos![e-mail]  (Conor O'Neill)
Subject: Re: Voyager Update - 06/13/90

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

   [lots deleted]

>                     Consumption
>             One Week    Propellant Remaining     Output     Margin
>  Spacecraft  (Gm)                (Kg)            Watts      Watts
>
>   Voyager 1    7             36.4 + 2.0          370         59
>   Voyager 2    6             39.5 + 2.0          374         66
>

Firstly, does 36.4 + 2.0 mean 36.4 "plus-or-minus" 2.0, or does this
indicate a "reserve" tank of 2.0 Kg.

Similarly, does "Margin Watts" mean the error in the estimate,
or the minimum power needed to run the spacecraft?




---
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".

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

Date: 22 Jun 90 09:02 EST
From: [e-mail]
Subject: REQUEST

   I have a request to make:

   I've recently taken an interest in satellite observing, and although
   updated orbital data for the major satellites is published regularly,
   I don't have any software that uses this data to plot times and positions.
   I have heard that there is lots of this software around, and would be
   very grateful if someone could send me some source code. I have access to
   VAX and SUN mainframes/workstations as well as IBM PC's.
     Thanks in advance.


    Andrew Johnson          |  [e-mail]
    GE Aerospace            |  REAL men use delete/noconfirm

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

Date: 22 Jun 90 12:23:40 GMT
From: usc!samsung!xylogics!merk!alliant!linus!mwunix.mitre.org![e-mail]  (Stephen Okay)
Subject: BiosphereII (Was RE:Egomania)

>From linus!think!yale!ox.com!kitenet!russ Fri Jun 22 08:13:09 EDT 1990
>
>In article <[e-mail]> [e-mail] ("Thomas Fletcher ", Hellraiser) writes:
[Lots of Luddite panicking]
>
>it's what we know that ain't so."  A reality check is a sure-fire
>way to uncover those things.  Testing terraforming and closed
>ecology systems is the only way to be sure.
Hmm...isn't this what Biosphere II is for??---testing out and manipulating
a closed environmental system?.
How are they coming on that anyways??---last I heard, they had finished construction and most of the equipment had started to arrive. --'Course that was about
a year ago. Anybody out there have the latest on B2s progress??

>  I am paid to write all of RSI's opinions.  Want me to write some for you?
Nahh...I get into enough trouble with my own :)


-----------------------
Stephen Okay       Technical Aide, The MITRE Corporation
[e-mail]

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

Date: 22 Jun 90 21:13:42 GMT
From: usc!jarthur!nntp-server.caltech.edu!deimos.caltech.edu![e-mail]  (Irwin Horowitz)
Subject: Re: SpaceList

In article <[e-mail]>, [e-mail] (Steve Hix) writes...
>
>Leaving the second (and day...) tied to an arbitrary natural phenomena.
>Or maybe ending up with "days" drifting with respect to local planetary
>"sunrise"/"sunset"/"midnight"?
>
>Tidy one thing up...ruffle various related items.
>
I agree as a scientist that redefining the second so that there are 10**5 each
day would make certain calculations easier, but the general public would never
go along with such an idea (too confusing!).  I would also like to see certain
dates on the calendar being redefined, especially New Year's, which is not
only entirely arbitrary, but the "Moment" is celebrated at 24 different times
around the world (actually more, as certain time zones are 1/2 hour off from
others).

I feel that a more logical "New Year" would either be the winter solstice (on
December 21st) or when the Earth passes through perihelion (around January 4th).
These could be celebrated by the entire world at the same time, and do have
some astronomical relevance.  However, I also realize that to screw around with
the calendar that much would totally mess up everyone (when would your birthday
be, for instance?).  Would it be that one of the above days (or perhaps another
with similar relevance) would be defined as the beginning of the year, and
Jan 1st would just be another day on the calendar?  When would the year number
be updated?  Or would Jan 1st be redefined to be one of those days and the
rest of the calendar be appropriately changed?  Therefore, even though this
would be a more logical time to start a "New Year," the complications of
changing the calendar this much would throw modern day society into a confused
mass which might never recover! :-) :-)
-------------------------------------------------------------------------------
Irwin Horowitz                        |"Suppose they went nowhere?"-McCoy
Astronomy Department                  |"Then this will be your big chance
California Institute of Technology    | to get away from it all!"-Kirk
[e-mail]               |       from STII:TWOK
[e-mail]                 |
-------------------------------------------------------------------------------

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

Date: 23 Jun 90 03:41:19 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 thought that for some of the Polar launches, they had to put in charges
>in the shuttle proper because it would be overflying populated areas.

Nope.  For one thing, there has never been a polar shuttle launch, and
never will be unless the USAF does a remarkable about-face.  For another,
polar launches would be south from Vandenberg, and there are few areas
of the planet that are as empty as the southeastern Pacific.  Finally,
NASA point-blank refuses to put destruct charges aboard the orbiter.
--
As a user I'll take speed over|     Henry Spencer at U of Toronto Zoology
features any day. -A.Tanenbaum| uunet!attcan!utzoo!henry [e-mail]

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

End of SPACE Digest V11 #557
*******************