Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_7/V13_718.TXT

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Subject: SPACE Digest V13 #718

SPACE Digest                                     Volume 13 : Issue 718

Today's Topics:
          Re: IGY and the beginning of the Space Age
              Re: Fermi Paradox
               Re: Space heros?
          NASA Prediction Bulletins:  Space Shuttle
          Re: Democracy:  Easy Come, Easy Go
         Earth Gravity Assist and Aerobraking Safety
              Re: Fermi Paradox
    Re: talk.politics.space (was Re: sci.space.moderated)
             Re: Crary's Quick Debunkings

Administrivia:

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

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

Date: 9 Jun 91 00:53:08 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!caen!ox.com!hela![e-mail]  (Allen W. Sherzer)
Subject: Re: IGY and the beginning of the Space Age

In article <[e-mail]> [e-mail] writes:
>There was no space race and very little space research funding until the
>Soviets launched Sputnik for the IGY, shocking the U.S. into joining a
>space race.

Read your history Nick. The space race began a LONG time before Sputnik.

>That the astronauts and their groupies managed to gain
>power is a relic of Kennedy's Apollo ...

The decision to send people up happened long before Kennedy ever got
to the White House. Project Mercury began and even had flown before
Kennedy hit on the idea of Apollo.

>The Astronauts did not contribute positively towards NASA's funding; indeed
>NASA funding started to drop after 1966 when the astronaut flights started
>to swing into full gear.

Funding dropped because development was nearing completion. BTW, funding
needs to go up before it can go down. How did it get up if those nasty
astronauts where so unpopular?

>NASA's funding cut from 1968 until the mid-1970's when manned spaceflight
>was replaced by automated exploration.

Sorry. NASA fudning went up to pay for the Shuttle, not for unmanned
probes.

    Allen

--
+---------------------------------------------------------------------------+
|Allen W. Sherzer |   DETROIT: Where the weak are killed and eaten.         |
|   [e-mail]   |                                                         |
+---------------------------------------------------------------------------+

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

Date: 8 Jun 91 18:16:15 GMT
From: agate!headcrash.Berkeley.EDU![e-mail]  (George William Herbert)
Subject: Re: Fermi Paradox


    While proposing what amounts to a Star Trek transporter may sound
great for solving the Fermi paradox, it's questionable if it's feasable to
manufacture such a device or if it's possible to make something like you
described work.  This is essentially science fiction.
    I'm going to argue that something this comple falls under the
'suffeciently advanced technology == magic' rule and that debating it from
a scientific point of view is pointless.

-george william herbert
[e-mail]

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

Date: 8 Jun 91 07:06:07 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Re: Space heros?

In article <".7-Jun-91.11:13:48.EDT".*[e-mail]> [e-mail] writes:
>
>To obtain the
>public's support, and therefore, an easier time at obtaining public funding,
>at least a certain degree of the space exploration should be manned...

This is total BS.  The civilian space program was originally motivated
by the automated IGY satellites, the first being Sputnik which shocked
the U.S. into funding spaceflight.  The correlation between astronaut
flights and NASA funding is negative. NASA funding started to drop in
1966 after Gemini swung into full gear, and dropped most precipitously
during the Apollo flights which the American public increasingly opposed.
Polls have always showed roughly equal public support for "unmanned"
and "manned" endeavors, even when stated with that falsely dichotomous
terminology.  The myth that astronauts somehow motivate space funding is
the last refuge for those who can't find any other rationale for the
wasteful astronaut toys the NASA leadership (astronauts) are pushing.


--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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

Date: 8 Jun 91 13:21:19 GMT
From: udecc.engr.udayton.edu!blackbird.afit.af.mil![e-mail]  (TS Kelso)
Subject: NASA Prediction Bulletins:  Space Shuttle


The most current orbital elements from the NASA Prediction Bulletins are
carried on the Celestial BBS, [phone], and are updated several times
weekly.  Documentation and tracking software are also available on this
system.  As a service to the satellite user community, the most current
elements for the current shuttle mission are provided below.  The Celestial
BBS may be accessed 24 hours/day at 300, 1200, or 2400 baud using 8 data
bits, 1 stop bit, no parity.

STS 40
1 21399U 91 40  A 91158.22557870  .00106961  00000-0  25599-3 0    85
2 21399  39.0070 322.2320 0013304   4.9358 248.6192 15.95228336   263
--
Dr TS Kelso                           Assistant Professor of Space Operations
[e-mail]          Air Force Institute of Technology

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

Date: 8 Jun 91 17:42:11 GMT
From: prism![e-mail]  (Matthew DeLuca)
Subject: Re: Democracy:  Easy Come, Easy Go

In article <[e-mail]> [e-mail] (Mark Ricci - CATS) writes:
>In article <[e-mail]> (Matthew DeLuca) writes:
>>If you want to lobby, fine, but you have to do it
>>on your own money.  NASA has to use its own money...

>Gee Matt, whose money do you think NASA's is?

NASA's money is NASA's money.

I've been trying to make a fairly subtle point that people aren't picking
up on: NASA is not the government.  It is an organization created by the
government, and it is funded by the government, but it is *not* the government.
If they were, there wouldn't be all the bickering and fighting and backstabbing
we see come budget time...it would all be one big happy family.
--
Matthew DeLuca
Georgia Institute of Technology      "I'd hire the Dorsai, if I knew their
Office of Information Technology      P.O. box."  - Zebadiah Carter,
Internet: [e-mail]    _The Number of the Beast_

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

Date: 9 Jun 91 05:46:53 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Earth Gravity Assist and Aerobraking Safety

In article <[e-mail]> [e-mail] (David Lowe) writes:
>
>I have been enduring all the romance about imminent asteroid
>mining and waiting for someone to discuss safety.

I have posted perhaps a dozen times on this subject over the last
two years.  To summarize, there is no way we can tolerate bringing
a dinosaur-killer sized asteroid anywhere near Earth.  Reentry of
c. 100 ton Shuttles is safely performed and tolerated towards inhabited
areas, and natural fireballs and meteorites massing several tons
each hit the Earth harmlessly every year.  Somewhere between these two
extremes, we need to figure out the margins of safety and enforce them.

There are several techniques for using Earth to change the orbital
trajectory of objects:

* fast aerobraking (eg Shuttle, Apollo)
* slow aerobraking (eg Hiten)
* gravity assist (eg Galileo)

All three of these can play important roles in reducing the costs of
capturing space materials from comet fragments and asteroids into
various Earth orbits.  The delta-v savings are roughly up to an order
of magnitude for gravity flyby, and up to two orders of magnitude for
aerobraking.

For gravity assist, the following need to be considered:

* what is the margin of error due to fringe atmospheric density,
  gravity anomaly and trajectory measurement error
* how quickly and precisely can the on-board engines compensate for
  trajectory errors directly preceeding and during the flyby
* can the operation be timed so that a worst-case error will cause
  reentry over an uninhabited area (eg the ocean)
* are there any strongly toxic or nuclear materials on board
* what is the worst-case scenario wrt the mass, composition, and
  worst-case error trajectory of the payload

For slow aerobraking, we must also consider the above points, paying
close attention to the fringe atmospheric density, since that is what
we are using to change the trajectory.

For fast aerobraking, we need to pay very close attention to upper
atmospheric density at all levels.  The error margins are much less.
Unless the worst-case scenario is trivial or the spacecraft is well-controlled
aerodynamically, fast aerobraking is much more dangerous than slow
aerobraking or gravity flyby.

Given these data points, we must then determine whether the project
is ethically and politically tolerable, and whether it can be insured.

For the sake of discussion, I make the following initial proposed rules
of thumb:

gravity assist & slow aerobrake
    * <.0001% chance of trajectory error sufficiently large for reentry
    * if reentry, >98% chance it will occur over & towards
      uninhabited area
    * payload mass limits:
        solid metallic materials: 5,000 tons
        stony materials: 10,000 tons
        carbonaceous materials or loose regolith: 30,000 tons
        volatile materials: 50,000 tons


fast aerobrake:
    * aerobrake must contain control surfaces sufficient to
      give <.001% chance of reentry due to error
    * if reentry, >98% chance it will occur over & towards
      uninhabited area
    * no strongly toxic or nuclear materials on board
    * mass limits:
        solid metallic materials: 200 tons
        all other materials: 400 tons (note: ceramic heat shield will
        be significant % of mass for any payload)


Significant amounts of simulation, study of real-life artificial and
natural reentries, and benefit/risk analysis need to go into
determining the actual safety margins.


--
Nick Szabo                [e-mail]
"If you understand something the first time you see it, you probably
knew it already.  The more bewildered you are, the more successful
the mission was." -- Ed Stone, Voyager space explorer

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

Date: 9 Jun 91 06:15:46 GMT
From: ogicse!milton![e-mail]  (William Lewis)
Subject: Re: Fermi Paradox

In article <[e-mail]> [e-mail] (Tarl Neustaedter) writes:
>In article <[e-mail]>, [e-mail] (Dani Eder) writes:
>> [stuff about sending people to other stars via information and replicators]
>>
>> Conclusion: The Fermi Paradox is very much with us.
>
>Nope. Several problems with your scenario:
>   [several good points deleted]

   And 7, it might be against the hypothetical aliens' hypothetical religion
to get scanned (destructively, no doubt) and sent across the galaxy to
be reconstructed. It certainly gives *me* the creeps.

   Once you have the technology to easily fabricate arbitrary objects
(which you postulate) the only real limit to the population of the
solar system is the amount of matter in it. (As for energy, it's easier
just to scoop up some of the Sun's atmosphere or a gas giant and fuse
it than go to some distant star.) While this is a limit, it's a pretty
big limit, and a natural disaster can always convert some of the
poopulation back into raw material ...

--
 [e-mail]       Seattle, Washington
     (William Lewis)   |  47 41' 15" N   122 42' 58" W
 "Just remember, wherever you go ... you're stuck there."

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

Date: 10 Jun 91 05:54:16 GMT
From: [e-mail]  (Todd L. Masco)
Subject: Re: talk.politics.space (was Re: sci.space.moderated)

[e-mail] (Peter L. Thomas) writes:
> (has anyone thought that space-tech is ready to graduate to
> sci.space.tech? just a side-note)

I doubt it.  One, the traffic doesn't warrant it.  Two, Space-tech is
for people who are actually willing to do some calculations before
posting.  Marc, the moderator, seems to shy away from larger local
redistributions of the list (such as the andrew machines).  Making
such a newsgroup would with defeat the purpose, if unmoderated, or if
moderated would just mean rejecting a couple of orders of magnitude
more posts than would be accepted.  Hardly worth the effort on
anybody's part.
--
Todd Masco  | [e-mail] | "Free speech is the right to shout
CMU Physics | [e-mail]  |  'theatre' in a crowded fire."

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

Date: 8 Jun 91 07:35:11 GMT
From: mcsun!ukc!edcastle!hwcs![e-mail]  (Stewart Fleming)
Subject: Re: Crary's Quick Debunkings

In article <[e-mail]>, [e-mail] (Chris
Stanfield) writes:
>
>Anybody care to list other terran formations that resemble faces, etc.?
>I know
>they exist all over the planet...

Mount Rushmore.
Of course, you can debate whether this shows existence of intelligent life
or not.

>Chris Stanfield, Mitel Corporation: E-mail to:- uunet!mitel!testeng1!stanfiel

:-)

STF
--
[e-mail]                        ...ukc!cs.hw.ac.uk!sfleming
"Hope my metabolic functions cease before I feel the effects of time.
   I am communicating about my contemporary peer group."

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

End of SPACE Digest V13 #718
*******************