Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_9/V16NO889.TXT

Text File | 1993-07-18 | 35KB | 816 lines

Space Digest                Sun, 18 Jul 93       Volume 16 : Issue 889

Today's Topics:
                       Ariane V.58 Mission Data
                          Clementine (ref?)
              GPS in space (was Re: DC-1 & BDB) (2 msgs)
                    ISECCo Update: Travels {Cont.}
                      message from Space Digest
                        Moon Cable/Beanstalk.
                        problem w/ZHR equation
                    Von Braun Team Work & DCX (Was
                     Where is ESA's ERIN server?
              Why are meteor showers seasonal? (2 msgs)

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: Sat, 17 Jul 93 12:40:16 GMT
From: Dean Adams <[e-mail]>
Subject: Ariane V.58 Mission Data
Newsgroups: sci.space

ARIANESPACE FLIGHT 58

The 58th Ariane launch is scheduled to place the INSAT 2B and HISPASAT 1B
satellites into a geostationary transfer orbit (GTO) using an Ariane 44L
launch vehicle equipped with 4 liquid strap-on boosters (PAL) and the Ariane
Dual Launch System (Mini-SPELDA).  It will be the 30rd launch of an Ariane 4
and the 13th in the Ariane 44L configuration.  It will be launched from the
Ariane launch complex ELA 2, in Kourou - French Guiana.

The launch vehicle performance requirement is 4,615 kg, of which
4141 kg are the combined satellite masses.  The total vehicle mass
at liftoff is 480,529 kg.

Required Orbit Characteristics:

  Perigee Altitude ..... 200 km
  Apogee Altitude ... 35,911 km at injection
  Inclination ............ 7 degrees

The Ariane 44L lift-off for Flight 58 is scheduled on Thursday July 22,
1993, as soon as possible within the following launch window:

     Kourou Time       GMT               Washington, DC
     19:47 - 20:52     22:47 - 23:52     18:47 - 19:52


Launch Vehicle:

Ariane 44L.  This is a three-stage liquid fueled launcher with liquid fueled
strap-on boosters.  The first stage (L220) is built by Aerospatiale, and is
powered by 4 liquid fueled Viking V engines.  The second stage (L33) is built
by MBB Erno, and is powered by a single Viking IV engine. Both the Viking IV
and V engines are manufactured by SEP.  The first and second stages use a
biliquid UH25/N2O4 fuel.  The third stage (H10) is built by Aerospatiale,
and is powered by a cryogenic H2/O2 fueled HM-7B engine built by SEP. The
four strap-on boosters are each powered by a Viking VI engine, also built
by SEP, which use the same biliquid fuel as the first and second stages.
The fully assembled launch vehicle stands 58 meters high on the pad, and
it is equipped with the Ariane payload fairing type 02.


Flight Profile:

 +02:31  Liquid strap-on booster jettison
 +03:37  First stage separation
 +04:26  Fairing jettison
 +05:43  Second stage separation
 +05:49  Third stage ignition
 +18:16  Third stage shutdown / GTO injection
 +20:53  HISPASAT 1B separation
 +23:54  SPELDA top separation
 +25:55  INSAT 2B separation
 +25:59  Third stage avoidance maneuver
 +29:20  End of Ariane mission 58


Payloads:

INSAT 2B is the second satellite of the second generation of the Insat
program for the Department of Space of the Indian Government.  It has been
built by ISRO to serve multipurpose domestic needs of the Indian nation.

  Total mass at lift-off .... 1,931 kg
  Mass at GEO insertion ..... 1,187 kg
  Dry mass ..................   911 kg
  On-board power ............ 1,140 W (end of life)
  Nominal lifetime .......... 9 years
  On-Orbit position ......... 83 degrees east

 Transmission capacity:
  C-band .... 18 transponders
  S-band .... 2 transponders of 50 W

 In-flight operations:
  Apogee motor firing 1 ..... about 26 hours after lift-off, at 3th apogee
  Apogee motor firing 2 ..... about 58 hours after lift-off, at 5th apogee
  Apogee motor firing 3 ..... about 78 hours after lift-off, at 6th apogee
  Solar array deployment .... about 31 hours after last apogee firing
  East antenna reflector deploy ... 14 hours later
  West antenna reflector deploy ... 10 hours later
  Solar sail deployment ............ 1 hour later


HISPASAT 1B is the second model of the first generation of
telecommunications spacecraft for HISPASAT.  It is built under
the main contractorship of MATRA MARCONI SPACE Toulouse, France.
The operational on-orbit location will be 7 degrees east.

  Total mass at lift-off .... 2,210 kg
  Mass at GEO insertion ..... 1,330 kg
  Dry mass .................. 1,052 kg
  On-board power ............ 4,700 W (end of life)
  Nominal lifetime .......... 10 years
  Span of solar panels ...... 22.3 m
  On-Orbit position ......... 30 degrees west

 Transmission capacity:
   2 channels (110W), Spain to American coverage
   2 channels for America to Spain coverage
   2 X-band transponders
   8 Ku-band transponders (55W)

 In-flight operations:
  East antenna deployment ... about 7 hours after lift-off
  Apogee motor firing 1 ..... about 37 hours after lift-off, at 4th apogee
  Apogee motor firing 2 ..... about 92 hours after lift-off, at 8th apogee
  Apogee motor firing 3 ..... about 157 hours after lift-off, at 11th apogee
  Solar array deployment .... about 183 hours after lift-off


Launch coverage:

All Ariane missions are broadcast live via satellite from Kourou.
Coverage begins at 30 minutes before launch, and continues until
all payloads have been deployed.

-{ Dean Adams }-

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

Date: Sat, 17 Jul 1993 18:07:01 GMT
From: Remi Cabanac <[e-mail]>
Subject: Clementine (ref?)
Newsgroups: sci.space,sci.astro

Hello netters,

I am currently following a summer session at ISU Huntsville Alabama, and
I am involved in a project to design a Lunar Farside Observatory. We
decided we needed a precursor orbiter and would like info on the Clementine
mission. Any help will be appreciated.

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

Date: Sat, 17 Jul 1993 18:28:41 GMT
From: fred j mccall 575-3539 <[e-mail]>
Subject: GPS in space (was Re: DC-1 & BDB)
Newsgroups: sci.space

In <226do3$[e-mail]> [e-mail] (Pat) writes:

>Comments like "WATW" (We Are The World) Orbit  does not sound like a
>positive assessment.  When there are numerous good reasons to push for
>51 degree,  65 Degree,  73 Degree or even 90 or 97 degree orbits.

Then people should be justifying those orbits based on their merits
and talking about their drawbacks (like requiring some enhanced
shielding, I gather) rather than trying to justify them as "the
Soviets coulc play if we launch to high-inclination orbit".  Having
been *briefly* exposed to reasons why a high-inclination orbit would
be better, practically all of the people trying to justify it seem to
spend most of their time dwelling on how it lets other nations 'play'
rather than on what we (the U.S.) gain from it.  So the advantages of
launching to high-inclination are there (as are the drawbacks).  Why
so little discussion of them from any of the proponents?

>The whole point of 51 Degree or higher orbit is to avoid single
>vehicle dependency.

>At 28.5 degrees,  only the shuttle could hit SSF with anything
>approaching useful payload and with existing hardware.

And only the Russians can if you launch it high-inclination.
Remember, there are several modules that the Shuttle can't boost to
higher inclination.  You'd need an Energiya launch for those.

>At 51 degrees, we open to launches out of both china and Baikonur.
>Possibly from pletsesk,  if you don't mind a big performance hit.

>at 65 degrees  you  open Pletsesk fully.  at 73 degrees you
>add in Japan.  Suddenly one has a whole diverse field of vehicles
>available to supplement SSF activities  that one does not have
>at low incliniation orbit.

See what I mean?  If there are advantages other than the use of
Russian and Chinese hardware and launch sites, why not discuss those
instead of several paragraphs on how a high-inclination orbit lets
those countries play?

>The rpimary onjective of SSF is to enrich a bunch of contractors.

You've been listening to Ken too much, Pat.  ;-)

>waiting for quarterly logistics flights from the shuttle  (especially with
>the risk of a shuttle accident and grounding being  high)  is not
>conducive to good station management.  Placing the station in an orbit
>where  other vehicles can support  either materials flow   or
>even logistics (In case of shuttle unavailability)  is
>in my mind good  business sense.

And back to the 'high-inclination is better because it lets the
Russians play' justification.  This is a lose insofar as a
justifcation for us assuming higher costs ($400 million, at least,
remember?) goes.

>>I would prefer to see a flyoff between a Soyuz and a U.S. designed ACRV. It is
>>possible certain hungry (George) aerospace (Retro) startups might want a crack
>>at a flyoff.

>Well,  NASA on their ACRV studies  thought it was too expensive.
>It seems a classic Make vs Buy decision on the ACRV.  WE could make it
>but it's cheaper to Buy.  Now if the Soviets do  Belly up on Us (
>the Unreliable Supplier Problem)  then we merely need enough
>inventory until we can gear up to Make.

But Make vs Buy isn't a good paradigm if there is any sort of
technology development involved in the alternatives.  You have to
count into the balance what sort of 'profit' we get from doing it
ourselves and what kind of potential 'loss' there is if we don't do it
ourselves (and hence lose ability in certain technology areas).  That
probably doesn't apply real strongly in this particular case, but I
think you simplified right over it by simply trying to ignore the
issue.

>Given that you claim a degree in economics,  i am surprised you aren't
>aware of these choices.

A cheap shot (and flame bait), and it also doesn't address the issue
of loss of capability on our part caused by taking a 'buy' decision
with regard to a piece of technology.

>I like george,  but as a taxpayer, i want best value for my money.
>If that means buying from the soviets,  why not?

You obviate the asnwer by pretending that it's not an issue.  'Why
not' is because it might (note -- I don't claim it will, just that it
needs to be considered) be in our better long-term interest to spend
more money up front and foster the development of the technology and
capability here at home so that we will have our own capability and
technology base going.

>COnsidering we put 1/3rd of our GNP  into relying on certain very unstable
>arab countries to sell us Oil,  I don't see what the problem is.

You have an alternative?

--
"Insisting on perfect safety is for people who don't have the balls to live
 in the real world."   -- Mary Shafer, NASA Ames Dryden
------------------------------------------------------------------------------
[e-mail] - I don't speak for others and they don't speak for me.

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

Date: 17 Jul 1993 15:42:03 -0400
From: Pat <[e-mail]>
Subject: GPS in space (was Re: DC-1 & BDB)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (fred j mccall 575-3539) writes:
>In <226do3$[e-mail]> [e-mail] (Pat) writes:
>
>>Comments like "WATW" (We Are The World) Orbit  does not sound like a
>>positive assessment.  When there are numerous good reasons to push for
>>51 degree,  65 Degree,  73 Degree or even 90 or 97 degree orbits.
>
>Then people should be justifying those orbits based on their merits
>and talking about their drawbacks (like requiring some enhanced
>shielding, I gather) rather than trying to justify them as "the
>Soviets coulc play if we launch to high-inclination orbit".  Having

Reasons for a High Inclination Orbit :

1)  Cheap Soviet flights available.

2)  Improved Earth Observation Missions.

3)  Improved Logistics Flow missions.

4)  Improved space science/engineering base.  (  hihg inclination,
is a far more rigorous environment then low inclination.

5)  Apparently ACRV return is simplified( This is what i was told,
    I can't see an intuitive reason why this is).



>
>But Make vs Buy isn't a good paradigm if there is any sort of
>technology development involved in the alternatives.  You have to
>count into the balance what sort of 'profit' we get from doing it
>ourselves and what kind of potential 'loss' there is if we don't do it
>

Make vs Buy is  properly cognizant of the benefits of
Technology developement.   Nevertheless,  Every company does
Make this  decision in it's business operations.

IBM  Buys  Micro-processors.  DEC buys 4M DRAMS.

Certainly there are intangible benefits from  spooling up to
do things,  but if that bleeds off developemnt  money from
more vital activities,  that is equally a problem.

Good Business people  make these analyses.


>>COnsidering we put 1/3rd of our GNP  into relying on certain very unstable
>>arab countries to sell us Oil,  I don't see what the problem is.
>
>You have an alternative?


More energy Conservation,  Higher energy taxes,  developemnt of
low energy consumption Infra-structure.   It's  bizarre, that it
is  cash wise cheaper for me  to drive  to Chicago  then to
take the train  ( The absolute lowest energy cost solution.

Why is it, cheaper for me to drive to work in DC (Home to the best
public transit system in AMerica)  then to take metro.


pat

--

God put me on this Earth to accomplish certain things.  Right now,
I am so far behind, I will never die.

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

Date: 17 Jul 1993 09:03:48 -0800
From: [e-mail]
Subject: ISECCo Update: Travels {Cont.}

     I  left  Rapid City (SD) almost 2 weeks ago.  It was a one day  drive  to
Minneapolis and the Browns (who I traveled with from Alaska) dropped me off at
Patricia  Wrede's.   Pat put me up for 2 days, while I was seeing  people  and
distributing information on ISECCo.
     Pat  also had a number of real useful ideas on gaining new  members.   We
are  striving to get our membership up to 1,000 members, which will provide  a
broad  enough  membership  base to fund construction.  Those of  you  who  are
interested in joining do send us a note!
     We  are  still looking for innovative ideas for finding members,  if  you
have  any  we'd like to hear about them.  Also we are  looking  for  magazines
which  cater  to  science-type  (including SF) people  in  which  we  can  put
classified ads.  If you know of any magazines like this please tell us!
     From  Minneapolis  I took a bus (this is a *very* low  budget  trip!)  to
Wichita  KS,  where I rented a car for 5 days.  From there I went to  a  small
town west of Hutchinson called Hudson where I visited Chandra Schaffer, who is
an  enthusiastic  ISECCo  volunteer.  While I was in the area I  went  to  the
Cosmosphere in Hutchinson, which is an excellent exhibit on space  technology.
Naturally I left some of our literature there.
     After  leaving Hudson I went south into Texas, and then back  up  through
Lawton,  Oklahoma City and then to Tulsa Oklahoma.  This leg of the  trip  was
primarily to pin up postcards on campus bulletin boards.  The postcards have a
blurb  on ISECCo on the back and anyone who wants more information can  simply
put their address on the front and drop it in the mail.  Any of you who  could
pin up some of these packets of postcards on bulletin boards please drop us  a
note so we can send you some!
     I  had relatives in Tulsa who put me up for a couple of nights.   When  I
left  Tulsa I drove back to Wichita, returned the rented car (which  was  very
handy,  though  an  expensive way to travel).  While waiting for  the  bus  in
Wichita I wrote about half this update.  I'll upload it the next time I  pause
long enough at a place with a phone!
     The  next  stop was Cleveland Ohio, where I presented a  seminar  on  our
biosphere project to a group of NASA Lewis people.  Since I am traveling light
I didn't have a lot of notes (etc) with me, but the seminar went quite well in
spite  of that.  I have been working on this project long enough so I know  it
by  heart!   When I left Cleveland I took the bus to Washington  DC,  where  I
shall be through the 19th of July meeting with people to discuss space, ISECCo
and our biosphere.
     For  those  of you who are 'joining us late' I am on a  trip  around  the
country, primarily visiting people who are doing research in closed ecological
life  support technology.  But I set aside a certain amount of time  to  visit
members  and  other  people  who  are  interested  in  space.   I  am  rapidly
approaching  the  half-way point on the trip, and have  accomplished  a  great
deal, not to mention meeting many interesting people.  To focus on my trip  to
the east coast and down to Florida (keeping in mind that these times are still
pretty flexible and will change as needed):
     7/17-7/19   visit people in the DC area (staying with Richard Kline)
     7/20  leave DC & arrive in New York area
     7/21-7/22 visit people in the NY area (staying with Richard Hope)
     7/23 leave NY; travel to Lexington Kentucky
     7/24-7/26 central Kentucky
     7/27 travel to Huntsville Alabama
     7/28 Huntsville area (staying with Peggy & Dale Hill)
     7/39 travel to Kennedy Space Center
     7/30-8/2 KSC (staying with Dennis Chamberlin)
     8/3  travel to Houston
Anyone  who  lives anywhere near this proposed travel path and would  like  to
meet  me please feel free to send me a note (include a phone number so  I  can
contact  you.)  I'd be happy to talk with you about our organization,  project
or just space in general.


ON  OTHER  MATTERS:
     For  those of you who are familiar with our setup you know  I  own/manage
rental properties.  These travels are possible because of the efforts of those
who  have stayed behind to take care of my properties, as well as run  ISECCo.
I  would  like  to thank Elisa Ballou and Scott Guse for  keeping  my  company
running smoothly, and stay on top of ISECCo activities like checking mail  and
weeding  the  garden.   Debi Wilkinson has put in  a  considerable  effort  in
arranging visits for me and many times acting as contact person and has been a
great help keeping this trip in order, as well as pay ISECCo bills  (including
those  I've generated on this trip).  Her efforts are very  much  appreciated!
We  have  an  excellent group, and our projects  move  forward  through  their
efforts.
     This is an ISECCo trip, and ISECCo is paying the majority of the expenses
(i.e.  everything that goes on the credit card).  This is not a drain  on  the
ISECCo  funds though because I donated $2,000 to ISECCo before leaving,  which
will more than pay for the expenses of this trip.  Indeed for the past year  I
have covered 100% of ISECCo's expenses--all the money donated by others in the
last  year has been set aside for construction.  So our construction  fund  is
growing!   I am not sure how much longer I will be able to continue this  (our
expenses are continually rising), but so far I have managed.

Would  you  like  more information?  Send me a note!   My  e_mail  address  is
[e-mail] and I answer every letter (some patience may be  needed
though,  since  I  am traveling and can only  log  in  occasionally.)   Please
include   a  postal  mailing  address  for  all   initial   correspondence--we
occasionally  have letters whose computer return address fails for one  reason
or another.

                                       --Ray :: President, ISECCo

      :::The International Space Exploration and Colonization Company:::
               :::P.O. Box 60885::Fairbanks::Alaska::99706:::
                        Researching  and  Developing
                    space oriented  technology  for  the
                           betterment of mankind.
     *    *    *    *    *    *    *    *    *    *    *    *    {end}

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

Date: 17 Jul 1993 15:52:39 -0400
From: Pat <[e-mail]>
Subject: message from Space Digest
Newsgroups: sci.space

In article <[e-mail]| [e-mail] writes:
|> Date: 11 Jul 1993 08:58:04 -0400
|>  Pat <[e-mail]>
|
|I don't know that  I really want to go into that very extensively,

Oh,  why not start a little heated discussion :-)

Here's  one guaranteed to get wingos  blood pressure going .

Did Werner Von Braun  have a habit of sieg heiling ?

:-)


|
|But, as far as I know, the REQUIRED margins were exactly the
|same for all stages.
|

Oh I was referring to something i saw in
the  literature.  The as - built margins in the S-II
were not as high as the other stages.


|was settled, everyone had his own "bogie" and no "shaving" was
|done, unless one exceeded the bogie. There were never any
|changes in the S-IC made because we weren't meeting weight.


What were the Safety Margins on the S-V?  I  heard somewhere

there was a conflict on should it be  140% of design load or
105% of design load.

|
|>Henry S. Hillbrath
|>Saturn V/S-1C Designer (with some assistance)
|
|> Really??????????
|
|You seem surprised, why? Didn't think there were any of us old
|codgers around any more? Didn't think we could find this
|newsgroup?

It is kind of rare to have  "We Were There " Folks  (Does anyone remember
the books)  on this news group.  It tends to be over-run by
under-grads.

>
>Surely, it couldn't be that you are doubting my word? I certainly hope  not.

No, just startled to see a real pro.  The numbers in this group
can be counted on ones fingers.  (I don't aspire to the title Pro).
>
>Notice, I only said that I was "Designer" not "The Designer."

Do you happen to know why there is no Saturn Stage marked S-III?

There was the S-I,  S-II  then S-IV.  kind of funny.

>
>I checked, none of the parts that I designed on the S-1C can be
>seen in the largest scale Revell model that I could find. But, I
>later calculated  that the cost savings that my design concepts
>produced were considerably more than my salary since I
>started in the business, 30 plus years ago. (Oh, well, I blew it
>all on the Shuttle.)


These certainly sound like a good story.


>
>NO ONE  believes an analysis...   |  EVERYONE believes a.test...
>   - except the guy who did it.   |     - except the guy who did it.
>
>                   T. M. ("Scotty") Davidson

Who'se he?

pat

--

God put me on this Earth to accomplish certain things.  Right now,
I am so far behind, I will never die.

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

Date: 17 Jul 93 11:52:37 GMT
From: Steve Linton <[e-mail]>
Subject: Moon Cable/Beanstalk.
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
|> In article <[e-mail]> [e-mail] writes:
|> >Local govermental problems along the equator, since the Beanstalk would
|> >need to be near the equator or on it.. The local government would ahve to
|> >be appeased.
|>
|> If you've got the sort of money you would need to build a beanstalk --
|> remember, this is a high-tech structure tens of thousands of kilometers
|> long, it *won't* be cheap -- you can just buy yourself a suitable local
|> government while you're at it. :-)  This will be a minor expense.
|> --

Actually, you will need to buy up, or at least buy off ALL the local governements
along the equator. In a worst-case catastrophe the cable will come down in pieces
the whole way round.

In one of his books (I forget the title) Charles Sheffield discribes an
alternative to Arthur C. Clarke's "Start in orbit and build up and down" strategy
for constructing an orbital tower. This is based on building the whole structure
in deep space and  spinning it up to 1 revolution/day. You then dig a LARGE hole
where you want the base to be and put a suitable rock in an elliptical orbit
tangent to the "orbit" you want the top of your tower to end up in.

You then fly the tower into place just as the rock passes over the hole and
QUICKLY fasten both ends.

This works beautifully provided nothing goes wrong, but some of the failure modes
are rather dramatic. In particular if you miss the rock at the top, but get
caught at the bottom the tower whiplashes round the equator (I think) and, if it
doesn't snap) the free end comes down VERY HARD INDEED.

I think I'd like to this idea tested on a few uninhabitted planets first.

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

Date: 17 Jul 1993 13:43:14 -0400
From: Earl W Phillips <[e-mail]>
Subject: problem w/ZHR equation
Newsgroups: sci.space,sci.astro

In trying to write a program around the recently
posted ZHR equation, I am having trouble with 1
of it's components. The equation for "C" in my
program doesn't give a result anywhere near the
example of 1.72, I get something like 4.6.

C=2.6 times exp(6.5-5.93)=1.72

Anybody got any idea what the problem is?

*****************************************************************
*                                    | ====@====      ///////// *
* [e-mail]|     ``________//         *
*                                    |       `------'           *
*                 -JR-               | Space;........the final  *
*                                    | frontier...............  *
*****************************************************************

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

Date: Sat, 17 Jul 93 04:48:00 BST
From: [e-mail]
Subject: Von Braun Team Work & DCX (Was

Paul Dietz <[e-mail]>

Writes:

> In article <21o1d9$[e-mail]>
> [e-mail] (George William Herbert) writes:

>> Pardon me, but didn't the J2 only get ike 365 Isp?  Isn't this a bit
low
>> for SSTO purposes?


> George, you really should get a copy of Sutton.   On page 196 (5th
ed.):

> Engine   Vac Isp    Dry Weight (lb)   Vac Thrust (lbf)    Vac
thrust/dry weight
> SSME      455           6335            470,000                 74.2
> J2        426           3454            230,000                 66.6

Actually, one might say that he SSME has an Isp 363.2 +/- 1.8
seconds, in fact, the "ICD - 13M15000 Space Shuttle Orbiter
Vehicle/Main Engine", sheet 4-4 says just that.  That is sea level. But,
then an SSTO has to start somewhere.

Even Sutton doesn't tell you everything (and you do have to be able
to read it, which is not always easy, as there is a lot "between the
lines.")

363.2 +/- 1.8 is not that far from 365. George should not have backed
down so easily.

Actually, that is the SSME, of course. I could look up the J-2 Isp, but I
won't. Arguably, the J-2 does not HAVE a sea level Isp, as it was not
qualified to operate at that condition. (Without "cheaters".)

Discussions of Isp are like those things on TV "Warning, do not try
this at home, the performers are trained professionals."

Isp is highly dependent on nozzle area ratio, the optimization of
which is best left to those trained professionals. The SSME is a
 particularly complex case, as it has a nozzle much too long for
best sea level  performance (as long as anyone dared make it
when it was designed)   yet it does not get as much vacuum
performance as it could if it did  not have to run at sea level
(or had an extendable cone.)

The J-2 loses to the SSME two ways, one, it has a gas generator (GG),
so there is a GG loss, and 2) it is much lower chamber pressure, so it
cannot tolerate as long a nozzle with back pressure, nor have as high
an area ratio in the same base area.

Opinions on SSTO's are like navels. There are those that say that
Thor's could have been SSTO's, they just didn't want to, and that
kerosene is all you want for fuel.

Having had some experience with engine/vehicle systems integration
for SSTO's myself, I feel that the SSME does not have sufficient
performance for "realistic" SSTO operation, and that engines, such as
the J-2, RL-10 etc. are totally out of the question ("bad jokes" one
might say.). We shall see, maybe, someday. It won't be this year, and
I wouldn't count on it being this century.

Henry S. Hillbrath

--------------------------------------------------------------------
NO ONE  believes an analysis...   |  EVERYONE believes a.test...
   - except the guy who did it.   |     - except the guy who did it.

                   T. M. ("Scotty") Davidson



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

Date: 17 Jul 1993 17:20:47 GMT
From: Troy Goodson <[e-mail]>
Subject: Where is ESA's ERIN server?
Newsgroups: sci.space,sci.astro

I was reading the latest Earth Observation Quarterly (published by ESA) and it
had a special section describing materials available from what I think was
called ERIN.  They gave the user name and password for guests to log on but
did not give the address of the server.  Does anyone know what that address
might be?

Troy.

-------------------------------------
Troy Goodson                        !
The Georgia Institute of Technology !
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uucp:     ...!{allegra,amd,hplabs,ut-ngp}!gatech!prism!gt5368a    !
Internet: [e-mail]                                !
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Date: Sat, 17 Jul 1993 12:03:40 GMT
From: Steve Linton <[e-mail]>
Subject: Why are meteor showers seasonal?
Newsgroups: sci.space



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

Date: Sat, 17 Jul 1993 12:05:58 GMT
From: Steve Linton <[e-mail]>
Subject: Why are meteor showers seasonal?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (David Fagan) writes:
|>     I'm sure the answer to this must be simple, but it's been nagging at me
|> for a long time. Why do particular metor showers recur at the same time of
|> year?
|>
|>     The simple answer is that there is a cloud of asteroids in the earth's
|> orbit which the earth passes thru at the same time each year. However,
|> don't I have to assume that the asteroids are in solar orbit as well? In
|> that case it seems unlikely that the earth would repeatedly encounter those
|> asteroids at the same point in its orbit. The only answer that leaves me is
|> that there is an asteroid belt (or many belts) which cross the earths
|> orbit. I've never heard anything to this effect, however.

In essence you have it right. There are `belts' of gas and dust that intersect
the Earth's orbit in various places. They are usuually in the orbits of comets,
either existing ones or `dead` ones that have lost all their gas by too many
close solar passages.

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From: "Bruce T. Harvey" <idsssd!bruce>
Subject: Re: Head NASA Select Guy (was Re: NASA SELECT  and scrambling.)
Message-Id: <[e-mail]>
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References: <[e-mail]>
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in article <[e-mail]>, [e-mail] (Theodore F. Vaida ][) says:
>
> [deleted for brevity]
>>Not so sure about his "trouble" conjecture;  just because you get
>>something for free doesn't mean you can't sell it to somebody!

[deleted for brevity]
> Ahh.. but considering the fact that you and I have already paid for it,
> and the cable company didn't (least not in tune with what they might
> make by selling it) it would be an attempt to sell you something you
> already own!  Personally I consider it theft of services (just like if
> I descrambled HBO and sold it to my neighbors, and it was theft of services to
> redistribute HBO when it was unscrabled, congress agreed to that by
> allowing scrambling on the supposedly FREE airwaves of the sattelites
> so...)

So if you had an antenna capable of receiving the signal, you could get it
for free.  And a Community Access TV center has an antenna that can grab the
signal (commercial free ... no income for the CATV center).  But since it's
commercial free, there is no income generated by this channel, as opposed to
the local commercials that are often inserted on channels like USA and TNT
(also 'free' kind of from our point of view) which bring revenue to the CATV
center (rebroadcaster).  Providing NASA Select would become a public service
and would be a DRAIN on local resources without additional funding.  It may
not be able to be 'officially' classified as a public service ... don't
know.

It might be better to pursue alternatives that can try to avoid this
argument, like getting one of the local schools to rebroadcast NASA Select
when it doesn't have other programming (Baltimore County, MD ... Dundalk
Community College does this admirably, even extending coverage during
Shuttle flights), or have this and perhaps other types of
government-sponsored broadcasts included in the realm that CSPAN covers, so
that's it's paid for by all and available to all.

You may be dead right in your arguments, but the reality of it is that if
the CATV folks have to do it for free, they won't, if they have a choice.

--
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
Bruce T. Harvey    (B-{>::      UUCP:    ... {uunet|mimsy}!wb3ffv!idsssd!bruce
Manager Appli. Devlopmt.::  INTERNET:     wb3ffv!idsssd!bruce%uunet.uu.net@...
INsight Distribution Sys::CompuServe:                               71033,1070
[phone] x315, x352:: SnailMail: 222 Schilling Cir.,Hunt Valley, MD 21031
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::

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End of Space Digest Volume 16 : Issue 889
------------------------------