Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V15_2/V15NO245.ZIP/V15NO245

Internet Message Format | 1993-07-13 | 35KB

Date: Fri, 25 Sep 92 05:00:05
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #245
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri, 25 Sep 92       Volume 15 : Issue 245

Today's Topics:
        21 cm rights and Libertarians Against Light Pollution
                  Clinton and Space Funding (2 msgs)
 Government and space exploration  Was: Re: Clinton and Space Funding
         How to teach about free fall? (was Re: zero gravity)
                         Ion drive pollution
                        ISAS/NASDA space race
                        Larsonian Festivities
                        Magellan Atlas Program
                          NASA Town Meetings
           NEAR asteroid mission (but wait! There's more!)
                             New Planet?
           PLANETLIKE OBJECT SPOTTED BEYOND PLUTO (2 msgs)
              Underreproduction  Was: Re: overpopulation
                              Waverider
                             zero gravity

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

Date: Thu, 24 Sep 92 10:04:59 -0500
From: [e-mail] (Phil G. Fraering)
Subject: 21 cm rights and Libertarians Against Light Pollution

[e-mail] (Josh 'K' Hopkins) writes:

\Something wierder occured to me after I posted this.  Do Libertarians restrict
/this right to radio waves or does it apply to other frequencies as well?  For
\example, can I sue my neighbor for having his outdoor lights on if I want to
/sleep?  Or more interestingly, could major obervatories sue the inhabitants
\of nearby cities because of light pollution?

I'm beginning to like the idea.

Anyone ever stop and think of the effect that light pollution has
on the space program, that major areas of the country are literally
drowning out the stars?

\Josh Hopkins                 Of course I'm a solipsist - Isn't everybody?
/[e-mail]

Why, I'm not. In fact, I'm pretty sure noone's a solipsist.

--
Phil Fraering [e-mail] where the x is a number from 1-5.
Phone: [phone] SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560
"NOAH!"
"Yes Lord?"                          - Bill Cosby
"HOW LONG CAN YOU TREAD WATER?"

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

Date: Thu, 24 Sep 92 14:03:06 BST
From: [e-mail]
Subject: Clinton and Space Funding

> technological edge?  Please don't spout off about cutting defense
spending
> until there are valid places for the money to go.  This idea of
cutting
> first and then trying to figure out what to do with the money later
does
> nothing for the country except increase unemployment and sacrifice
our
> technological edge.
>


Ah... Might I propose that the best possible place to put it is in
the wallet of the person who earned it in the first place?

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

Date: 24 Sep 92 15:03:10 GMT
From: Jim Mann <[e-mail]>
Subject: Clinton and Space Funding
Newsgroups: sci.space

In article <[e-mail]>
rn11195@sage (Robert Nehls) writes:
> Contrary to popular belief, the majority of R and D money for the
armed
> forced goes into communications, advanced IC technologies, computer
> technology, and various other non-lethal activities.  Sure some
money does
> go into weapons research, but they are they ARMED FORCES aren't
they.  Now
> don't get me wrong, I have no problem with reducing defense R and D
spending
> as long as the money goes into other R and D activities and people
don't
> lose their jobs.  Like it or not, the two main technology drivers
for the
> last 5 decades have been first the military and then the space
program.

I'm not sure that's true anymore (or whether it's been true for
a while now).  Parts of the computer industry are driven by the
DoD, true. However, the real computer revolution has been
driven by the business community demanding more computing power
for less money.

> Billions of dollars have been cut from the defense budget.  Where
has this
> money gone?  No one talks about that.  The deficit hasn't been cut,
new jobs
> haven't been created, and the country on the whole is worse off due
to the
> unemployment increase.  Do you really think that it is a
coincidence that
> the military and space budget cuts coincide with the Japenese
gaining a
> technological edge?

Huh?  Seems to me the Japenese gained their technological edge
in many fields because we were spending so much money via
big governemnt (often defense-related) programs.  Perhaps
if RCA, GM, Motorolla, Intel, etc. didn't have to pay so much
in taxes to support gigantic governemnt defense contracts (and
to pay for defending countries that aren't doing near as much
to defend themselves) we'd regain our edge.

Please don't spout off about cutting defense spending
> until there are valid places for the money to go.  This idea of
cutting
> first and then trying to figure out what to do with the money later
does
> nothing for the country except increase unemployment and sacrifice
our
> technological edge.
> --

How about the money going to a) pay of the deficit and b) after
that (if we ever do get it paid off) allowing the folks who
actually make the money to keep a bigger chunck of it.

--
Jim Mann
Stratus Computer   [e-mail]

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

Date: 24 Sep 92 13:26:38 GMT
From: Herman Rubin <[e-mail]>
Subject: Government and space exploration  Was: Re: Clinton and Space Funding
Newsgroups: sci.space,sci.astro,talk.politics.space,alt.politics.bush,alt.politics.clinton

In article <[e-mail]> [e-mail] (Rob Healey) writes:
>In article <[e-mail]>, [e-mail] (Mark 'Henry' Komarinski) writes:
<|> [Benefits of military spending, etc...]

<|> >Military R&D provides jobs (Damn good paying jobs) not only for
<|> >those who do the work, but also for a great deal more who make
<|> >the supplies for the work.

<|> So what about the benefits from just plain space exploration?  Imagine the
<|> spinoffs once we get a space platform working, or get a colony on the moon?
<|> Or for that matter, make it to the moon again.  The benfits of this
<|> could be huge.  At the same time, people are getting employed and less
<|> money is going to trying to kill someone else.

>    What I want to know is why everybody WANTS government involved
>    with ANY of the space exploration? Government is what generally
>    messes up perfectly good ideas. Doesn't matter whether it's
>    a Republican or a Democrat in office, space utilization suffers
>    because its at the spending whim of a government. B^(.

>    Government is OK at doing initial exploration, i.e. Christipher
>    Columbus, but things don't get rolling till private enterprise get's
>    involved, i.e. the colonies were usually paid for by investors who
>    expected the colonies to pay for themselves.

>    What we REALLY need to do is convince investors that starting
>    a colony on the moon in our time is as good of an idea as
>    starting a colony in the new world was back in the 17th
>    century.

>    I think we'll be FAR better off if government gets out of the
>    space business and private/commercial interests take over. To
>    this end maybe it would be a good thing for Clinton/Gore to
>    get elected because then we'd have to de-tox from government
>    control and funding of space related projects. This is assuming
>    they won't fund space activitys.

The problem is that the government is involved in far more ways than
funding.  Also, private exploration societies have existed at many times;
many explorers in the 18th and 19th centuries especially were funded by
extragovernmental sources not directly interested in profit.

There are lots of restrictions on what can and cannot be done.  From
environmental impact of launches to liability for failures, the government
is so involved that it is hard for the private sector to do anything
really different.  If, for example, the space advocates were able to
raise money to put up a space platform, the government could easily
veto it.  Other more radical proposals, like rapidly moving belts, are
almost certain to be vetoed.
--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: [phone]
[e-mail] (Internet, bitnet)
{purdue,pur-ee}!pop.stat!hrubin(UUCP)

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

Date: 24 Sep 92 11:26:48 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: How to teach about free fall? (was Re: zero gravity)
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Dave Tholen) writes:
> Here I am teaching an Introductory Astronomy class, we're
> talking about Newton's Law of Universal Gravitation at the same time that
> the Space Shuttle is flying, and I'm trying to convince them that the
> gravitational force in the Shuttle is only slightly less while in orbit
> than here on the surface of the Earth, but not zero.  And NASA keeps talking
> about the zero gravity experiments.  Would it be less high-tech sounding if
> NASA referred to them as "free fall" experiments?  Small price to pay, in my
> opinion, to avoid confusing college students, especially those for which
> science is a difficult subject to begin with.

Maybe we can start a discussion:  How do you teach students why they
see people floating around inside Mir and the Shuttle?  I'll benefit
from any good ideas the Net contributes-- I may be teaching some space
courses myself in the next few months.

During the first and second stage         Bill Higgins
flights of the vehicle, if a serious      Fermilab
irretrievable fault should occur and      [e-mail]
the deviation of the flight attitude of   [e-mail]
the vehicle exceeds a predetermined       SPAN/Hepnet: 43011::HIGGINS
value, the attitude self-destruction
system will make the vehicle
self-destroyed.
     --Long March 3 User's Manual
     Ministry of Astronautics, People's Republic of China (1985)

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

Date: 24 Sep 92 12:42:00 GMT
From: Greg Macrae <[e-mail]>
Subject: Ion drive pollution
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] ("Phil G. Fraering") writes...
>\Is there a chance that the ion drive might pollute the environment that some
>/scientific instrument on the probe is trying to measure?  Like an instrument
>
>I think the ion contamination (they tend to become neutral fairly
>quickly, and in fact the exhaust needs to be neutralized quickly
>or the ion drive stops working) is secondary to how having
>the electric and magnetic fields around the spacecraft disturbed
>is going to affect fields-and-particles experiments..
>
We can bound the problem very easily.  Ion thruster fuel flow rates are
typically in the 10's of standard cubic centimeters per minute (sccm).
Fuels are projected to be heavy noble gasses like xenon, krypton or argon.
Those gasses make up a very small (read nearly immeasurable) portion of the
distant atmosphere of planets.  It is very possible that the signal from
the ionized fuel would mask natural emmision from those gasses.  The
'pollution' should not affect other signals.  The flow rates we are talking
about are 2+ orders of magnitude lower than flow rates from chemical systems.

What we know about the thruster plume:  It is space charge neutral.  This means
that there are as many free electrons in the plume as there are charges on the
ions.  Very few of the ions are actually neutralized in the near space of the
thruster.  The beam remains very collimated.  Something on the order of 95%
of the beam is within a 15 degree half angle cone.  (numbers are approximate
and vary with the specific design.)

More typically the pollution concern is with contamination of spacecraft
surfaces and interactions of the plasma with communications signals.  The
surface contamination issues are simpler with ion than chemical.  The
plasma interactions have been successfully modeled and verified experi-
mentally.  References on the latter include papers by D. Manzella or L.
Zana-Carney.


Greg
--------------------------------------------------------------------
     MacRae                  |       Too curious flower
                             |   Watching us pass, met death...
  [e-mail]  |       Our hungry donkey.
                             |                      -Basho
--------------------------------------------------------------------

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

Date: Thu, 24 Sep 92 10:01:43 -0500
From: [e-mail] (Phil G. Fraering)
Subject: ISAS/NASDA space race

\I think there is *already* a space race going: I believe that ISAS,
/the Japanese space agency for science, and NASDA, the Japanese space
\agency for engineering, are competing to land on the Moon.  Remember,
/you heard it here first.

Given that NASDA has about 10 times the funding ISAS has, anyone out
there want to get together a fund to help out ISAS and make it a
more even match?

Besides, at the rate NASDA is going with the H-2, if the job is
mainly left to them thanks to politics/funding/etc., Japan might
not reach the moon until some increadibly late date (like when
we return)...

\     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
/   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
\ /       \                          (_) (_)                    / | \
/ |       |     Bill Higgins   Fermi National Accelerator Laboratory
\ \       /     Bitnet:     [e-mail]
/   -   -       Internet:  [e-mail]
\     ~         SPAN/Hepnet:      43011::HIGGINS

On the other hand, we could threaten to turn Fermilab loose on them
if they don't treat ISAS better...

--
Phil Fraering [e-mail] where the x is a number from 1-5.
Phone: [phone] SnailMail: 2408 Blue Haven Dr., New Iberia, La. 70560
"NOAH!"
"Yes Lord?"                          - Bill Cosby
"HOW LONG CAN YOU TREAD WATER?"

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

Date: Thu, 24 Sep 92 11:01:16 PDT
From: [e-mail] (Dan Kelo)
Subject: Larsonian Festivities

>Robert E. McElwaine ([e-mail])
>expounds on the virtues of Larsonian cosmologies.....

O.K. Robert, you've piqued my interest, and I will probably read
Larson's book.  However, if I may beg you to PLEASE avoid another
million+ line post to repeat the information which we have all
seen already.

Thanks,

Dan

_______________________________
Dan Kelo - [e-mail]
"I'm not a number, I am a free man!" - The Prisoner
_______________________________

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

Date: 24 Sep 92 23:00:06 GMT
From: Ron Baalke <[e-mail]>
Subject: Magellan Atlas Program
Newsgroups: sci.space,sci.astro,alt.sci.planetary,sci.geo.geology

                             ==========================
                               MAGELLAN ATLAS PROGRAM
                                 September 24, 1992
                             ==========================

     An updated version of the Magellan Atlas program has been released by the
Magellan project.  This program was designed to be used with the Magellan
CDROMs.  This program will do the following:

         o find the latitude/longitude of named features on Venus
         o given a latitude/longitude, find the mosaics which lie atop
       that point and the Magellan CDROMs on which they are found.
         o the atlas now includes CDROMs up through 69
         o the named feature descriptions includes a short description
       of the meaning (origin) of the name, and adds the diameter and
           crater type information listing in Schaber's "JGR - Planets"
           article of August 25, 1992.  Diameters for some coronae are also
           listed.
         o find all the named features (numbering 824) which lie in (or on) a
           specific mosaic has been added, in order to help those who wish to
           work with a specific CD-ROM or mosaic.  (This should be helpful
           to teachers, who may have only a limited set of CD-ROMs.)

     There is both an IBM PC and Macintosh version of the Magellan Atlas
program.  The programs are available using anonymous ftp at:

        ftp:      ames.arc.nasa.gov (128.102.18.3)
        user:     anonymous
        cd:       pub/SPACE/SOFTWARE
        files:    magellan.zip (IBM PC version -> PKZIP)
                  magellan.sit (Macintosh version -> STUFFIT, MacBinary format)
                  magellan-sit.hqx (Macintosh version -> BINEX -> STUFFIT)

     Also, the database files used by the Magellan Atlas program are available.
A description of each field is included at the beginning of each file.
The underlying databases include the center latitude/longitude given in
Schaber's article also, but they are not displayed by the atlas program to
avoid confusion.  The database files are available at:

        ftp:      ames.arc.nasa.gov (128.102.18.3)
        user:     anonymous
        cd:       pub/SPACE/MAGELLAN
        files:    names.txt (ASCII)
                  midr.txt  (ASCII)
                  mgn-dbf.zip (2 DBase files -> PKZIP)
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Quiet people aren't the
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | only ones who don't say
|_____|/  |_|/       |_____|/                     | much.

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

Date: Thu, 24 Sep 1992 13:20:09 -0400 (EDT)
From: [e-mail] (Tricia Porth [phone])
Subject: NASA Town Meetings

The tentative dates for the NASA Town Meetings with
Administrator Goldin are as follows:

        Nov  9          Raleigh-Durham
        Nov 17          Hartford
        Nov 20          Indianapolis
        Nov 30          Tampa
        Dec  3          Los Angeles
        Dec 15          Seattle

I will post changes as I hear of them.

Tricia Porth
[e-mail]
202-358-0171


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

Date: 24 Sep 92 14:12:12 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: NEAR asteroid mission (but wait! There's more!)
Newsgroups: sci.space,sci.astro

Let's talk about the New, Improved NASA, with Secret Ingredient FCB!

Robert Farquhar, the wizard of ICE/ISEE-3 and the guy who suggested
Giotto's visit to a second comet, has left NASA Goddard and joined the
Applied Physics Laboratory at Johns Hopkins University.  APL has a
long track record of building modestly-sized spacecraft, especially
for the U.S. Navy.  Farquhar gave a talk at the World Space Congress
in one of the COSPAR sessions on a new project:  the Near Earth
Asteroid Rendezvous (NEAR).  It's part of something called the
"Discovery" series of lower-cost spacecraft NASA wants to do; I think
the figure $150 million was mentioned.

I came into the talk late, but apparently caught most of it.

Prime target is a 1998 launch to 4660 Nereus, an asteroid with an
orbit similar to Earth's, requiring a delta-V of 1.165 km/sec.  Launch
7 January 1998, arrive 16 January 2000. Spacecraft would go into an
orbit around the asteroid, distant at first, then sneaking in to lower
and lower orbits as Nereus's gravity field is better understood.  NEAR
would orbit in a plane perpendicular to the spacecraft-Earth line, so
its antenna always points at Earth, and rotate once per orbit, so  its
instruments always point toward the asteroid.

The Announcement of Opportunity is due about a year from now, but the
strawman payload includes visible imager, gamma-ray spectrometer,
imaging spectrograph (I presume seeing deep into the infrared),
magnetometer, and laser altimeter.  This last instrument is needed for
navigation, not just science, to get a good close orbit, and would
have a 20 km range.   The gamma-ray spectrometer would provide
information on the surface composition, but it needs a long
integration time (nominially one year for decent signal-to-noise), and
a fairly close orbit helps its spatial resolution.

How does the spacecraft look?  Imagine a square cardboard box, 1.5 m
on a side (I moved to a condo last weekend, I've been looking at a lot
of these), a little shallower than a cube.  Open the four top flaps.
These are the solar panels in a cross-shaped array.  Put a dish in the
center of the box.

The fixed 1.5 m X-band dish allows (at 1 AU from Earth) 20.8 kbits/sec
using DSN's 34-meter ground stations, 83.8 kb/sec with the 70-m
dishes.  Solid-state data recorder would  hold 5E5 bits. (Now that I
look at my notes, that seems a bit small! Maybe I transcribed it
incorrectly.  Think that 5 coulda been an 8?)

They're trying to design for a Delta launch using the 8-foot fairing.
Dry mass would be 400 kg, experiments taking up 60 kg of that, and
there would be 300 kg of propellants.  A bipropellant propulsion
system has a big 450-N (100-pound) thruster and twelve 22-N thrusters.

Solar panels would provide 300 watts of electricity at 2 AU.  They are
fixed, but the Earth is within 30 degrees of the Sun during the
mission, so there is plenty of sunlight available in Earth-pointing
mode.

Now for the fun part.  You say you want to visit more than one
asteroid? There's one on the way, 2019 Van Albada, and for an extra 16
m/sec of delta-V NEAR can see it.  1.7 AU perihelion, 2.61 AU
aphelion, inclined 4.0 degrees, 17 km diameter.  Zip by in July of
1998, take a few pictures.  Then head for Nereus.

What's that?  You say you've been orbiting Nereus for nine months, and
you're tired of looking at it?  For an extra delta-V of just 69 m/sec,
we can leave orbit on 12 September 2000 and fly past the Earth in
February 2002.  Pick up a little speed, come back next year to the
Earth, pick up a little more speed, and on 16 November 2003 you'll be
sailing past Comet Encke!

Or! Do three swingbys of Earth, an Encke flyby, then return for two
Earth swingbys, and you can go on to the asteroid Eros on 18 August
2005.

Instead of Eros, you could go to comet Tempel-1 or another I wrote
down as S.W.3.  Or, if you prefer, you could do a flyby of the
mysterious major asteroid Vesta with three Earth swingbys!  This would
give you a "small-body grand tour" for a total delta-V cost of 158
meters per second beyond the Nereus-orbit budget.

If you miss Nereus, or you want to buy extra copies of the NEAR
spacecraft, there are launch opportunities to 3361 Orpheus in March
1998 and another to Nereus in January 2000.  Obviously Farquhar
prefers the January 1998 window, and taking plenty of propellant along
(like maybe 375 kg instead of 300 kg).

In article <[e-mail]>,
[e-mail] (Dennis "I've Got The World On
A String" Wingo) writes:
> I saw an awesome presentation at the WSC about a
> faster cheaper better asteriod mission that boggles the mind [...]
> I wonder if Bill bought the paper on that one.

I sure would have! Alas, unlike IAF sessions, COSPAR does not have
papers (!).  I am trying to get some pictures of the spacecraft, as I
think asteroid missions would be a good topic for my next pop-science
slideshow.  The Morrison report on the asteroid-collision threat is
now out, and I grabbed a copy of that at WSC.

> It was from JPL

No, APL...

> and was a laugh a minute as this guy
> tossed out several variations of the mission that would take the
> probe to several asteroids and comets.  He spoke in the manner of a
> vacuum cleaner salesman and although he was funnin, it was a joy to
> hear.

Dennis caught the spirit of it pretty well.  And Farquhar's track
record suggests he may be able to deliver on these outlandish
promises, if the hardware holds up.

"Do you know the asteroids, Mr.Kemp?...    Bill Higgins
Hundreds of thousands of them.  All
wandering around the Sun in strange        Fermilab
orbits.  Some never named, never
charted.  The orphans of the Solar         [e-mail]
System, Mr. Kemp."
                                           [e-mail]
"And you want to become a father."
  --*Moon Zero Two*                        SPAN/Hepnet: 43011::HIGGINS

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

Date: 15 Sep 92 19:21:46 GMT
From: [e-mail]
Subject: New Planet?
Newsgroups: sci.astro,sci.space

The following bulletin was posted last night on CompuServe's ASTROFORUM:



#: 110734 S14/News/Current Events
    14-Sep-92  18:07:11
Sb: #Object beyond Pluto
Fm: SKY  TELESCOPE 70007,2762
To: All

There is some REALLY BIG NEWS just now breaking in the astronomical world.  The
IAU Central Bureau for Astronomical Telegrams has just issued IAU Circular 5611
to report the discovery of a faint object that seems to be outside the orbit of
Pluto!  Brian Marsden has given it the preliminary designation of an asteroid:
1992 QB1. But its true nature will be the subject of intense observations in
the next few months.

Dan Green of the CBAT says they really don't want people to start calling this
thing "Planet X" or the 10th planet or anything like that.  It's just too soon
to say.  For example, he says it could turn out to be a huge comet coming in.
It is now so far away that if it is a comet on a very elongated orbit it may
take 30 years to reach perihelion.  Then it could well become the Comet of the
(21st) Century!!

The discovery was made by David Jewitt and Jane Luu using the University of
Hawaii's 2.2-meter telescope on Mauna Kea.  The first images were secured
August 30, but just as with the discovery of Pluto in 1930 the discovery was
kept "under wraps" for awhile to allow a better assessment.  The object appears
stellar and has a visual magnitude of 23.5

Jewitt and Luu note that the object is fairly red, suggesting a surface rich in
organics.  The current position is, for 0h UT on September 15, 1992:  0h 00.09
+0d 01'.7 (2000.0).  The only orbit solution Marsden has published so far is a
circular one, which puts the object at 41.2 a.u. from the Sun.  It is moving
retrograde at only 3" per hour.

Stay tuned!
                -- Roger Sinnott

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

Date: 24 Sep 92 07:28:37 GMT
From: Hartmut Frommert <[e-mail]>
Subject: PLANETLIKE OBJECT SPOTTED BEYOND PLUTO
Newsgroups: sci.astro,sci.space,alt.sci.planetary

[e-mail] (Stan Ryckman) writes:

>Well, bad news.  The new object (1992 QB1), planet or not, is just
>about in the opposite direction from Pluto at present.  Unfortunately,
[..]

>I don't know in what direction Chiron lies at present.

Can someone post the orbital data for the 3 objects (1992QB1, Pluto, and
Chiron), please ?
--

 Hartmut Frommert                 <[e-mail]>
 Dept of Physics, Univ of Constance, P.O.Box 55 60, D-W-7750 Konstanz, Germany
                                           -- Eat whale killers, not whales --

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

Date: Thu, 24 Sep 1992 09:18:28 GMT
From: Dave Tholen <[e-mail]>
Subject: PLANETLIKE OBJECT SPOTTED BEYOND PLUTO
Newsgroups: sci.space

In article <[e-mail]>  [e-mail] writes:

> Two planetlike objects, 1992 AD and 1992 QB1, spotted this year between
> 9 AU and 59 AU... Had there been something like that before ? If not, was
> it because:
> 1) 1992 is a lucky year (normal statistical fluctuation) ?
> 2) people did not really try (in particular, there was no systematical
>    search within the Kuiper belt) ?
> 3) technique was not good enough ?
> 4) there was no "well thought out and planned experiment" ?
> 5) these objects were given another name (comets) ?

Primarily due to the availability of large format CCDs.  We're covering
more sky area to fainter limiting magnitudes than ever before.

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

Date: 24 Sep 92 14:10:05 GMT
From: Herman Rubin <[e-mail]>
Subject: Underreproduction  Was: Re: overpopulation
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Edward V. Wright) writes:
>In <[e-mail]> [e-mail] (Nick Szabo) writes:


>>For those of us interested in the prospect of civilization's expansion
>>into space, this is an especially serious problem.  The concept of
>>expanding space colonies, or a growing population on a terraformed Mars,
>>is in jeopardy if, as demographics indicate, a technologically
>>sophisticated population with perfect birth control would have
>>birth rate of less than 1.0 per couple per lifetime, or a population
>>decline of 50%/generation.

>At least three things could change this.  The people who wanted
>to move to the colony might tend to be people who wanted to have
>larger families.  The colony developers might offer special
>incentives to attract people who wanted larger families or
>encourage people to have larger families than they otherwise
>would.  Or a major breakthrough might occur in life-extension
>research, increasing the number of child-bearing years in a
>couple's lifetime.

There are also other possibilities, some of which have occurred in
science-fiction stories.  These involve in vitro fertilization, with
storage of eggs and sperm, or even of embryos, etc.  There might even
be professional host mothers.  Also, population density affects normal
reproductive rates.



--
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907-1399
Phone: [phone]
[e-mail] (Internet, bitnet)
{purdue,pur-ee}!pop.stat!hrubin(UUCP)

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

Date: Thu, 24 Sep 92 14:26:16 BST
From: [e-mail]
Subject: Waverider

I attended an interesting lecture last night by Duncan Lunan (Bill:
do you remember the guy in the kilt selling Halley's Whiskey at the
PghL5 bid party at DC85?) of ASTRA, a Scottish space group. It was
his first visit to Belfast.

His group, ASTRA, has been working on the Waverider idea for decades.
The idea is that a concave lower aerodynamic surface traps the
shockwave and lets the craft ride on it. They've done supersonic wind
tunnel tests, small rockets to release models, theoretical work on
meager computer resources...

He suggests the waverider as a great way for entering the martian
atmosphere and flying about dropping of probes. Unmanned though. On
Mars the touchdown speed would be 400 km/sec. He suggested he would
not wish to be the first to touch down on a non-runway at that
speed...

He also showed ideas for a solar probe that used "aerogravity assist"
to get in close to the sun. A waverider enters an atmosphere (not TOO
deeply!) and uses it to make a driection vector change much larger
than gravity alone could do.

This requires a rather interesting maneuver. Since it is flying at
higher than escape velocity, it enters UPSIDE DOWN and use
aerodynamics to push it towards the planet. It then has to rotate the
lift vector for escape.

Sound a bit hairy to me...

The middle of the lecture was punctuated by a non-sonic boom as the
police forensics lab, a couple km distant, got blown up. No, it
wasn't done by amateur rocket enthusiasts... Needless to say, the
after lecture pub jokes were about hypersonic forensic labs and panel
truck parts...

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

Date: 24 Sep 92 11:24:53 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: zero gravity
Newsgroups: sci.astro,sci.space

In article <[e-mail]>, [e-mail] (Dave Tholen) writes:
> I wonder what it would take to convince NASA to quit using the terminology
> "zero gravity" when referring to some of the experiments done aboard the
> Space Shuttle?  Here I am teaching an Introductory Astronomy class, we're
> talking about Newton's Law of Universal Gravitation at the same time that
> the Space Shuttle is flying, and I'm trying to convince them that the
> gravitational force in the Shuttle is only slightly less while in orbit
> than here on the surface of the Earth, but not zero.

Dave's remarks made me wonder: what does NASA call it these days?

Technical people at NASA seem to refer to it as "microgravity;" I
haven't paid much attention to what PR people write... so I went
hunting.

I examined the text of the NASA press kits for the Shuttle missions
STS-N where N is one of {45,46,47,50,52}.  I searched for strings
characteristic of "microgravitational terminology" (for want of a
better phrase).  My results:

"micrograv"     141 times
weightles       22 times
"zero gravity"  once
"low grav"      11 times
"free fal"      never

STS-47, which flew the Japanese Spacelab, had an experiment called
"Space Research on Perceptual Motor Functions Under the Zero Gravity
Condition," and four experiments with the phrase "Low Gravity" in
their titles.  Perhaps fashions in Japanese scientific English differ
from those of American scientists?

A few months ago, I made a remark on sci.space in message
<[e-mail]>:

>situations involve zero-g (all right, "microgravity," I'm a child of
>the Fifties)...

and Henry Spencer replied:

>Come, come, Bill.  A true child of the Fifties calls it "free fall"
>as Heinlein did.

So "free fall" is completely obsolete, but at least it does give the
impression that the force of gravity is still operating.  "Zero-G" has
been abandoned as misleading, except possibly by the Japanese.
"Microgravity" suggests that there may be tiny forces operating from
tides and the motion of equipment.  "Weightlessness" is apparently
de-emphasized but still occasionally in use.  "Low gravity" is a
rarely employed synonym for "microgravity."

I don't know how to answer Dave's problem.  What name should you apply
to "free fall" to avoid confusing students?  The best, rather lame,
answer I have to offer is to do a solid job of teaching them where
the appearance of "weightlessness" comes from.  If they understand
what's really going on, they won't be confused no matter what you call
it!

However, this is a difficult thing to do-- it's a tougher concept to
get across than, say, why stars come in different colors.  I think
I'll start a second message thread about this.  Stay tuned.

     O~~*           /_) ' / /   /_/ '  ,   ,  ' ,_  _           \|/
   - ~ -~~~~~~~~~~~/_) / / /   / / / (_) (_) / / / _\~~~~~~~~~~~zap!
 /       \                          (_) (_)                    / | \
 |       |     Bill Higgins   Fermi National Accelerator Laboratory
 \       /     Bitnet:     [e-mail]
   -   -       Internet:  [e-mail]
     ~         SPAN/Hepnet:      43011::HIGGINS

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End of Space Digest Volume 15 : Issue 245
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