Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V10_2/V10_236.TXT

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Subject: SPACE Digest V10 #236

SPACE Digest                                     Volume 10 : Issue 236

Today's Topics:
              RE: SPACE Digest V10 #233
                 Re: finally!
            Re: Vax to ride space shuttle.
           Re: Geostationary vs. Equatorial orbits
       Re: NASA Headline News for 10/26/89 (Forwarded)
              Re: Future Space Missions
              Re: Space Elevator
              fragility of life support
           Re: Geostationary vs. Equatorial orbits
              Re: Future Space Missions
              Re: COBE Press Kit (long)
           Re: Geostationary vs. Equatorial orbits
----------------------------------------------------------------------

Date:     Sat, 11 Nov 89 16:21:23 -0900
Sender: <[e-mail]>
Reply-To: <[e-mail]>
From: "This sentence has thre erors."  <[e-mail]>
Subject:  RE: SPACE Digest V10 #233

On the thread of "living in basements"  The moon is both more and less
hospitable than the place where I am living.  As I type, it is -51'F
outdoors with a WCF making it close to -70.  To get on my bicycle and
ride to work (a 90 minute ride) takes about 2 hours to dress and prepare.
(I ride a bicycle because it is a much mroe reliable form of transportation
for me in the winter...batteries don't die of exposure, the engine doesn't
icce up, the radiator doesn't freeze....)  Under that situation, the moon
and interior Alaska are about as pleasant as one another.  However, if
one of my life support systems dies (woodstove, insulation, etc...) there
is usually enough time for me to fix the problem without serious injury.
On the Moon, there is no guarentee.  There are two general reactions to
a fragile personal environment.  One is the "machismo" reaction espoused
by so many of my fellow alaskans, the other is simply quiet acceptance...
Yes, people can survive on the Moon, given the proper living quarters...
No, I don't think we're anywhere close to being able to do it yet...
Please remember, most of NASA's engineers live in beastly, uninhabitable
places like Florida or Texas or Washington D.C.  They don't have any
intuitive grasp of climactic extremes, or the need for insulation...just
like I personally, have no intuative feel for dealing with 100 degree weather
with high humidity.  It can be learned, however.

On to some more details of building L-City:  Vacuum makes a beautiful
thermal insulator.  It will be needed UNDER L-City...Such as a honeycomb
of unpressurized cells under the city "foundation".  One of the great
difficulties of living in Alaska is that the ground saps heat MUCH faster
than ambient air temperature.  I have no idea if any analagous problems
would exist on the Moon.  However, you do have the advantage of virtually
unlimited power on the moon for heating....and no wind chill factor.

Ramblings courtesy of Ken Burnside/FSKWB@ALASKA/[e-mail]

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

Date: 1 Nov 89 17:04:50 GMT
From: littlei!nosun![e-mail]  (David Schneider)
Subject: Re: finally!

In article <[e-mail]> [e-mail] (David Ross) writes:
> The whole point of this meaningless tirade is, in short, that even if Mr.
>Spencer is NOT the absolutely first person to tell _YOU_ about something,
>and even if he is not the first person to tell most people, there are still
>going to be a few of us who do appreciate hearing about it from SOMEBODY.
>

It also adds to the sense of completeness for those reading the progress
of the preparation, launch, and mission.  And some of us do lose track
of news on the conventional media (radio, TV).

                    Dave Schneider
                    Intel Scientific Computers

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

Date: Sat, 11 Nov 89 22:51:33 EST
From: "Keith F. Lynch" <[e-mail]>
Subject: Re: Vax to ride space shuttle.
To: "[e-mail]"@MINTAKA.lcs.mit.edu
Cc: [e-mail], [e-mail]

> It ... is cooled by convection.

How can that work in microgravity?  Warm air wouldn't rise.
                                ...Keith

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

Date: 11 Nov 89 17:55:48 GMT
From: bfmny0![e-mail]  (Tom Neff)
Subject: Re: Geostationary vs. Equatorial orbits

In article <[e-mail]> [e-mail] (Laurence Larry Sheldon) writes:
>OK, a question from the "F" row--I am not anything that starts with
>"astro-" but I thought geostationary orbits _were_ equatorial orbits!

Any truly geostationary orbit is equatorial.  Other orbits, with equal
23:56 periods but nonzero inclinations, will have figure-8 shaped
ground tracks centered at the equator and with a length that increases
with inclination.

Anyway, someone may have misread the discussion.  We were talking
about the cosmic background explorer (COBE) satellite which has a
SUN SYNCHRONOUS, *not* geostationary, orbit.  Sun synchronous is a
near-polar orbit tweaked just enough so that the orbital plane
precesses a degree/day to track the sun rather than the stars.
The ground track of a sun-syncronous orbit zips all over the place.
(However, it's always the same time of day underneath the satellite,
which is why s-s orbits are popular with photo spysats.)
--
"UNIX should be used          ::   Tom Neff <[e-mail]> or
 as an adjective." -- AT&T   ::    ...uunet!bfmny0!tneff (UUCP only)

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

Date: 11 Nov 89 23:09:05 GMT
From: jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: NASA Headline News for 10/26/89 (Forwarded)

In article <[e-mail]> [e-mail] (Nick Watkins) writes:
>Now my question. CRRES is to ride an Atlas 1. What is the difference
>between this and current Atlas Centaurs, and also what is an Atlas 2?

This is the latest silly marketingspeak from General Dynamics.  Fact
is, almost nobody ever uses just a plain Atlas any more -- the Centaur
is a standard fixture now.  "Atlas 1" is the new marketing name for
essentially an ordinary Atlas Centaur.  Atlas 2 is a slightly souped-up
version planned for the near future.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 12 Nov 89 00:17:20 GMT
From: gem.mps.ohio-state.edu!wuarchive!mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Future Space Missions

In article <[e-mail]> [e-mail] (lawrence.m.geary,ho,) writes:
>I have heard that Cassini will also use an Earth flyby to gain speed.
>I assume this means that these probes are using underpowered boosters
>and launching from the shuttle, as was the case with Galileo...
> WHY in heavens name is JPL sticking to this method for probes planned
> for far in the future?...
>... Why aren't there plans to use appropriate boosters?

Because there are none.  Although it is fashionable to malign the Shuttle
as a planetary launcher, the Shuttle/IUS combination is the heaviest
booster available (outside the Soviet Union).  Titan/Centaur is in second
place by a considerable margin.  Shuttle/Centaur would be better,
Shuttle-C/Centaur would be still better, and a stretched-tank Centaur
fuelled in orbit would be better yet... but the first was cancelled, the
second is just a gleam in the planners' eyes, and the last isn't even
being planned.

The only available-now launcher that could do a better job on Cassini
would be Energia.  The Soviets have no superstitious fear of cryogenic
upper stages, and they will happily quote a price to put 200 tons --
eight times the Shuttle payload, enough for a lot of Centaurs -- in low
orbit using an 8-strapon Energia.  If you're absolutely determined not
to use something that hasn't flown, they'll quote a price for 75 tons
or so using the off-the-shelf 4-strapon Energia.  NASA is not going to ask.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 11 Nov 89 18:00:29 GMT
From: mailrus!jarvis.csri.toronto.edu!me!radio.astro!helios.physics![e-mail]  (Christopher Neufeld)
Subject: Re: Space Elevator


   In _The Endless Frontier_ edited by Jerry Pournelle (Ace books, 1979)
there is an article by Hans Moravec called "Cable Cars in the Sky". He
discusses the currently available materials for making a geosynchronous
skyhook, allowing for taper of the skyhook so that each segment of cable is
just strong enough to hold the weight of the cable below plus payload. I
quote without permission: p. 307
   "Single crystal graphite whiskers with 50 times the strength to
    weight of steel have been grown in laboratories. Bulk material
    as strong would permit a synchronous cable with a taper of only
    10, and a mass ratio of 400. Half this strength is perfectly
    adequate for an Earth synchronous skyhook."

   Sorry I don't have a more recent reference which might tell whether we
can make these things in bulk now. A taper of 10 means that it is ten times
thicker at synchronous orbit than at the ground and the ballast. A mass
ration of 400 means that it can lift payloads weighing up to one four
hundredth of the total mass of the cable. The taper is exponential in the
weight to strength ratio. So, something with "half this strength" would
have a taper of 100. The mass ratio would also roughly square.

   Other references:
"Sky Stalk" by Charles Sheffield in _The Endless Frontier Vol II_
_The Inventions of Daedalus_  by David E. H. Jones p. 168
J. D. Isaacs, A. C. Vine, H. Bradner, G. E. Backus  _Science_ 151, 682
        (1966)
Lvov  _Science_ 158, 946  (1967)
J Pearson  Acte Astronautica 2, 785 (1975)
J Pearson  IAF Congress, Anaheim, Ca., Oct. 1976.  AIAA paper IAF 76-123
J Pearson  European Conference on Space Settlements and Space Industries
            London, England, Sept. 20, 1977
H. P. Moravec  23rd AIAA Meeting, The Industrialization of Space, San
            Francisco, Ca., Oct 18-20, 1977
      also Journal of the Astronautical Sciences 25, Oct-Dec 1977
J Pearson  AIAA/AAS Astrodynamics Conference, Palo Alto, Ca., August 7-9,
            1978, AIAA paper 78-1427
H. P. Moravec  _Skyhook!_, L5 News, August 1978

Most of these references reproduced from the bibliography in Moravec's
article.

   So, what say we start now?
--
 Christopher Neufeld....Just a graduate student  | "Out of my way,
 [e-mail]                    | I'm a scientist!"
 [e-mail]              |  - War of the Worlds
 "Don't edit reality for the sake of simplicity" |

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

Date: 12 Nov 89 04:05:18 GMT
From: jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: fragility of life support

In article <[e-mail]> <[e-mail]> writes:
>... Under that situation, the moon
>and interior Alaska are about as pleasant as one another.  However, if
>one of my life support systems dies (woodstove, insulation, etc...) there
>is usually enough time for me to fix the problem without serious injury.
>On the Moon, there is no guarentee...

The answer to this is obvious:  systems which can suddenly "fail hard"
must be fixed to either fail more slowly or fail soft.  (Just hoping
they won't fail is not acceptable for long-term habitation; they will.)
Actually, most life-support system failures for a lunar colony *are*
either slow or soft, just like on Earth.  The bad ones are catastrophic
loss of pressure (use multiple walls and compartmentalization), sudden
major loss of hard-to-replace fluids (gas or liquid) into vacuum (same
solutions), and sudden massive contamination of the rather small ecosystem
by toxic materials (compartmentalization, plus extra precautions in areas
handling toxic materials).  It should be possible to handle most everything
else with the same approach used on Earth, i.e. repair of broken systems
plus sufficient reserves to survive transient failures.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 11 Nov 89 22:02:11 GMT
From: cs.utexas.edu!ut-emx!walt.cc.utexas.edu![e-mail]  (Feulner ... Matthew Feulner)
Subject: Re: Geostationary vs. Equatorial orbits

This is just for completeness:

In article <[e-mail]> [e-mail] (Tom Neff) writes:
>In article <[e-mail]> [e-mail] (Laurence Larry Sheldon) writes:
>>OK, a question from the "F" row--I am not anything that starts with
>>"astro-" but I thought geostationary orbits _were_ equatorial orbits!
>
>Any truly geostationary orbit is equatorial.  Other orbits, with equal
>23:56 periods but nonzero inclinations, will have figure-8 shaped
>ground tracks centered at the equator and with a length that increases
>with inclination.

Right, There is a difference between geostationary and geosynchronous.
Geosynchronous orbits just have the proper period.  Geostationary
orbits are geosynchronous with zero inclination.

>Anyway, someone may have misread the discussion.  We were talking
>about the cosmic background explorer (COBE) satellite which has a
>SUN SYNCHRONOUS, *not* geostationary, orbit.  Sun synchronous is a

(not necessarily)

>near-polar orbit tweaked just enough so that the orbital plane

"tweaked" meaning being at a certain inclination and altitude orbit
so that the non-spherically-symmetric part of the gravitational
potential acts to give it the correct precession rate.  Mainly,
J2 (the flattening) & J3 (the pear shape) of the spherical harmonic
expansion.  The Earth itself is the source of the precession.

>precesses a degree/day to track the sun rather than the stars.
>The ground track of a sun-syncronous orbit zips all over the place.
>(However, it's always the same time of day underneath the satellite,
>which is why s-s orbits are popular with photo spysats.)

Matthew

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

Date: 8 Nov 89 14:16:09 GMT
From: att!cbnewsh![e-mail]  (lawrence.m.geary)
Subject: Re: Future Space Missions

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>                         Future Space Missions
>
>   o Cassini
>       Possible launch in 1996, orbiter would spend 4 years studying Saturn and
>       send an atmospheric probe into the moon Titan.
>
>   o Fire and Ice
>       Possible launch in 2001, will use a gravity assist flyby of Earth in
>       2003, and use a final gravity assist from Jupiter in 2005, where the
>       probe will split into its Fire and Ice components:  The Fire probe
>       will journey into the Sun, taking measurements of our star's upper
>       atmosphere until it is vaporized by the intense heat.  The Ice probe
>       will head out towards Pluto, reaching the tiny world for study by 2016.

I have heard that Cassini will also use an Earth flyby to gain speed.
I assume this means that these probes are using underpowered boosters
and launching from the shuttle, as was the case with Galileo. This was
done with Galileo because it was too late - or would cost too much, or
the probe was too heavy - to refit the probe for launch on an ELV with
a Centaur upper stage. But WHY in heavens name is JPL sticking to this
method for probes planned for far in the future? Galileo will take six?
years to reach Jupiter this way; it should have taken two. The other
probes will likewise take years longer to reach their destinations by
using this technique. Why aren't there plans to use appropriate boosters?

--Larry
--

     [e-mail]    Think globally ... Post locally    att!hoqax!lmg

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

Date: 11 Nov 89 23:37:42 GMT
From: jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: COBE Press Kit (long)

In article <[e-mail]> [e-mail] (Steve Willner) writes:
>The one thing I wonder about is that the press release mentioned
>eclipses; I don't see why there should be any in the IRAS-type orbit.
>Maybe COBE is using a slightly different orbit (i.e. not exactly 90
>degrees to Earth-Sun line) for some reason...

For a sun-synchronous orbit at a given altitude, ignoring one or two
details, the inclination with respect to Earth's equator is fixed.  A
sun-synch orbit at practical altitudes is a few degrees retrograde.
(If anyone is really interested, I can post the formula.)  The orbital
precession that makes the orbit sun-synchronous is caused by Earth's
equatorial bulge, so orientation to the Earth is crucial.

HOWEVER... that is with respect to the Earth's axis and equator, not with
respect to the Earth-Sun line... and Earth's 23+ degree axial tilt means
the two are *not* the same.  A sun-synchronous orbit does have eclipses,
especially in summer and winter when one of the Earth's poles is tilted
well away from the Sun and satellites passing near it are therefore in
shadow.  I *think* there would be times in spring and fall when the bird
would be in continuous sunlight -- I can't visualize it quite well enough
to be sure -- but this definitely doesn't happen year-round.
--
A bit of tolerance is worth a  |     Henry Spencer at U of Toronto Zoology
megabyte of flaming.           | uunet!attcan!utzoo!henry [e-mail]

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

Date: 10 Nov 89 19:05:49 GMT
From: portal!cup.portal.com![e-mail]  (Laurence Larry Sheldon)
Subject: Re: Geostationary vs. Equatorial orbits

OK, a question from the "F" row--I am not anything that starts with
"astro-" but I thought geostationary orbits _were_ equatorial orbits!

As I pondered-while-typing it dawned on me that I guess you could have
a geostationary orbit at any latitude, but somehow is seems like an
"orbit" directly over a pole would be undefined, so there must be some
limit to how high a (in terms of latitude) a geostationary orbit can be.

Is it possible to explain all that in terms that a survivor of
high-school geometry and trigonometry, and college algebra can handle?

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

End of SPACE Digest V10 #236
*******************