Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V16_0/V16NO028.ZIP/V16NO028

Internet Message Format | 1993-07-13 | 30KB

Date: Sat,  9 Jan 93 05:12:28
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #028
To: Space Digest Readers
Precedence: bulk


Space Digest                Sat,  9 Jan 93       Volume 16 : Issue 028

Today's Topics:
                       *** BUSSARD RAMSCOOP ***
                Anti-atoms (was Re: Making Antimatter)
                        averting doom (2 msgs)
        HST Discovers Double Nucleus in Core of Active Galaxy
                     Iridium plans use of Proton
                            Justification
             Justification for the Space Program (3 msgs)
       Let's be more specific (was: Stupid Shut Cost arguement
          Making Antimatter (was: *** BUSSARD RAMSCOOP ***)
                            Marketing SSTO
                   Mars Observer Update - 01/08/93
                       Perseid storms 1993/1862
                         Question about SETI
                  RTG's on the Lunar Module (2 msgs)
          Subjective Safety Measure(Re: man-rating) (2 msgs)

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", and (un)subscription requests of the form
    "Subscribe Space <your name>" to one of these addresses: listserv@uga
    (BITNET), rice::boyle (SPAN/NSInet), utadnx::utspan::rice::boyle
    (THENET), or [e-mail] (Internet).
----------------------------------------------------------------------

Date: 8 Jan 93 22:01:44 GMT
From: Henry Spencer <[e-mail]>
Subject: *** BUSSARD RAMSCOOP ***
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Richard Schroeppel) writes:
>Since fusing protons is so hard, why not use deuterons? ...
>Perhaps the ramscoop collector could selectively enrich d,
>by selecting for atoms having a magnetic moment.

Deuterium fusion is certainly a whole lot more practical than proton
fusion.  Unfortunately, there *probably* isn't enough deuterium in the
local interstellar medium to make this work well.
--
"God willing... we shall return."       | Henry Spencer @ U of Toronto Zoology
       -Gene Cernan, the Moon, Dec 1972 |  [e-mail]  utzoo!henry

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

Date: 8 Jan 93 13:27:20 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: Anti-atoms (was Re: Making Antimatter)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (nathan wallace) writes:
> There is yet another interesting book out there, called "Mirror Matter"
> by Dr. Robert L. Forward, another far-thinker in this area. He has
> worked with DOD and other interested parties on antimatter

Quite true.

> as a
> *practical* energy source right now.
   ^^^^^^^^^                ^^^^^ ^^^
This is hard to believe.           So is this.

Originally we were discussing the design of high-performance
interstellar propulsion systems, on a multi-century timescale where
antimatter may be competitive with other methods.  The short-term
prospects for it are pretty dismal.

> More interestingly to me, he mentioned that DOD is in the process
> of building an accelerator solely for the purpose of generating
> AM for use in space projects, both as fuel and for research purposes.

Vaporware-- unless it's secret, which I very much doubt.

> Presumably the "cold" AP mentioned in the recent Sci Am article would
> be part of such a system.

The U. of Washington ion traps are suitable for keeping only small
numbers of antiprotons, or other charged particles, so far as I know.


> Reality Check:
> We have never actually made antimatter. We have made anti-particles,
> but as yet they have never been cold enough to try to get them to
> link up into matter. Supposedly this experiment is intended in the
> relatively near future; perhaps Bill Higgins could comment on this.

Well, I would apply the word "antimatter" to any antiparticle, but I
understand what you mean:  matter made of neutral anti-atoms has not
been fabricated.  H. Poth and collaborators have done work on
antiprotonic atoms, where a negative antiproton orbits a positive
nucleus for a short time (it's a nice probe of nuclear physics).  They
would like to make antihydrogen (positron plus antiproton), but as far
as I know they haven't managed it yet.  My reference is a 1988
workshop proceedings, so I may be out of date.  If somebody is
planning to do this, it's certainly at CERN's Low Energy Antiproton
Ring, where the action is in this field.  Fermilab has no facilities
for work with "cold" antiprotons.

Bill Higgins, Beam Jockey         | "I'm gonna keep on writing songs
Fermilab                          | until I write the song
Bitnet:      [e-mail]  | that makes the guys in Detroit
Internet:  [e-mail]  | who draw the cars
SPAN/Hepnet:      43011::HIGGINS  | put tailfins on 'em again."
                                            --John Prine

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

Date: 8 Jan 93 20:28:14 GMT
From: Benjamin Weiner <[e-mail]>
Subject: averting doom
Newsgroups: sci.astro,sci.space,sci.physics

[e-mail] (Blair P. Houghton) writes:

>>>         WASHINGTON (UPI) -- Life on Earth as we know it will

>>>     come to an end in 1,500 million years ...

>Do you seriously believe that a species capable of creating
>and enjoying The Love Boat is capable also of learning
>galactic engineering?

A better question in my opinion is whether a species capable of
creating and enjoying The Love Boat *should* be saved from doom.

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

Date: 8 Jan 1993 20:38:11 GMT
From: "Blair P. Houghton" <[e-mail]>
Subject: averting doom
Newsgroups: sci.astro,sci.space,sci.physics

In article <[e-mail]> [e-mail] (William VanHorne) writes:
>In article <[e-mail]> [e-mail] (Blair P. Houghton) writes:
>>Do you seriously believe that a species capable of creating
>>and enjoying The Love Boat is capable also of learning
>>galactic engineering?
>
>Son, if there's a buck to made doing it, It Will Be Done.
>Amen.

Exactly the reason we'll all die as cinders wearing Ronco's
Amazing New All-Polyester/Mylar Anti-Sol Suits with
Magnesium Chloride Eyeholes and Plastic Fan.

                --Blair
                  "Hey, Doc, I picked up this
                   rash on my thighs from the
                   guest-host in the last episode;
                   you wanna take a look at it?"

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

Date: Sat, 9 Jan 1993 01:16:51 GMT
From: "Loren I. Petrich" <[e-mail]>
Subject: HST Discovers Double Nucleus in Core of Active Galaxy
Newsgroups: sci.space,sci.astro

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>     "The galaxy's active core presumably harbors a black
>hole which has been re-fueled by the galactic collision,"
>said Dr. Jack MacKenty, Assistant Scientist at the Space
>Telescope Science Institute in Baltimore.

    I presume that what happens to a black hole in a galactic
center is that it eats up all the stars on nearly radial orbits and
tends to deprive itself of stars to consume, with new stars for it
only arriving by their orbit parameters diffusing slowly to suitable
parameters.

    An incoming galaxy would not suffer this depletion of suitable
stars, and would presumably have some stars going head-on into the
hole, with many more to come.

    Did I get it right?
--
/Loren Petrich, the Master Blaster
/[e-mail]

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

Date: Fri, 8 Jan 1993 17:44:00 GMT
From: Dennis Newkirk <[e-mail]>
Subject: Iridium plans use of Proton
Newsgroups: sci.space

This weeks Space News has 3 stories related to Iridium.
The first says Iridium spokesman John Windolph confirmed
the Russian Proton booster has been selected as one of
several launch suppliers.  The article also claims 3
Protons are planned to launch 21 Iridium satellites.

In a related story, Lockheed (prime contractor for
Iridium satellites) has entered a partnership with the
Krunichev plant near Moscow to market the Proton booster.
Lockheed has agreed to pay $5 million over the next few
years to support the Krunichev plant and in return gets
exclusive marketing rights for all but Russian government
use of the Proton.

Any export of a US satellite like Iridium must still
get export permits to permit launch on the Proton. The
State Department approved the partnership late last month
and this decision is producing criticism now from
some US government officials, says Space News.

Last month the Russian Prime Minister announced the
deal and said something about funding Krunichev to
establish new Proton launch facilities at Plesetsk,
a move that would be good for NPO Energia which has mentioned
the desire to launch Mir 2 from Russian territory.

There are a lot more details in the articles so check
them out if your interested, I don't know anything about
Iridium.

Dennis Newkirk ([e-mail])
Motorola, Land Mobile Products Sector
Schaumburg, IL

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

Date: Sat, 9 Jan 1993 00:23:50 GMT
From: "Mr. X" <[e-mail]>
Subject: Justification
Newsgroups: sci.space,misc.education

In article <[e-mail]> [e-mail] (John Roberts) writes:

>Has anyone had personal experience with magnet schools? I'm curious about
>whether they provide any benefit.


    I taught in a magnet school (MCSM) in NYC.  Compared to what many
    kids in the city have in the way of a school environment, magnet
    schools are idyllic.  At least the kids learn something.  What's
    more, it is easier to maintain discipline because you can always
    threaten the misbehaved with expulsion.  Most kids will take this
    seriously because they WANT to be there.  Once you get a kid into
    a decent place to learn, most don't want to go back to a hell hole.

    MCSM had passable education... maybe even pretty good, by normal
    standards, so I'd have to say that in the inner city environment,
    magnet schools are definitely of benefit for those students that
    are able to attend.

    -Andy V.

PS MCSM == Manhattan Center for Science and Mathematics.

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

Date: Fri, 8 Jan 1993 21:55:14 GMT
From: "Michael C. Matthews" <[e-mail]>
Subject: Justification for the Space Program
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]> [e-mail] (Paul Dietz) writes:
>In article <[e-mail]> [e-mail] (James L. Felder) writes:
>
>>> is very hard to replace with some substitute.  Fossil fuels are
>>> an example -- there is no reason why we should not be able
>>> to survive indefinitely without them, if some other source of
>>> energy is available.
>
>> And no matter what we will have to learn to do without them.  And will
>> probably be cursed by future generations for burning such a useful
>> commodity simply to heat our homes.
>
>Just like we curse the shortage of whale oil?  Hardly -- they will
>view fossil fuel use as a curious historical anomaly, and pity
>us for being (so) relatively poor and ignorant that we could not
>use cleaner alternatives.

No, more like we curse the shortage of whales.  :-)

There are many useful things to do with petroleum products other
than produce energy -- they are useful as lubricants and are needed
for the production of plastics and other petrochemicals.

>...
>Powersats as usually described can't hack it as the primary energy
>source for earth, since there's not enough room in GEO.  They'd have

What does this mean?  Are you implying that powersats would be as restricted
as comsats in "orbital slot" width?  Why?

>to be farther away.  That drives up cost.  I am also not convinced the

There are reasons to think that a lunar surface-based solar power
infrastructure could be considerably cheaper than GEO powersats, due to
the lack of a requirement to develop a very large-scale lunar surface-
to-GEO transportation infrastructure for delivery of lunar raw materials
for powersat manufacture.


--
Mike Matthews, ex-Tether Dude +------------->   [e-mail]
"Had the Shuttle on a String"  \_ Now accepting NeXTMail via KlugeNet(TM)!
Lockheed-ESC                  |
Houston, TX                   |          *** WILL HACK FOR FOOD ***

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

Date: Fri, 8 Jan 1993 23:21:33 GMT
From: Paul Dietz <[e-mail]>
Subject: Justification for the Space Program
Newsgroups: sci.space,talk.politics.space

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

> There are many useful things to do with petroleum products other
> than produce energy -- they are useful as lubricants and are needed
> for the production of plastics and other petrochemicals.

They aren't *needed* for plastics, although they are currently the
cheapest feedstock.  We could make plastics out of any carbon source,
given energy and cleverness (we already know how to, just not
competitively).  I suspect our descendants will have sufficiently
better catalysts and cheap enough energy that petroleum would not be
of interest.

>>Powersats as usually described can't hack it as the primary energy
>>source for earth, since there's not enough room in GEO.  They'd have

> What does this mean?  Are you implying that powersats would be as restricted
> as comsats in "orbital slot" width?  Why?

I believe the problem was with shading during the equinoxes.  One
solution would be to make the individual powersats larger, with
multiple transmitters.  I don't know how big you can make them before
tides get too strong.


> There are reasons to think that a lunar surface-based solar power
> infrastructure could be considerably cheaper than GEO powersats, due to
> the lack of a requirement to develop a very large-scale lunar surface-
> to-GEO transportation infrastructure for delivery of lunar raw materials
> for powersat manufacture.

I was wondering if someone would mention this.  This idea loses the
advantages of GEO powersats: ability to supply any site on earth
continuously, and the ability to keep the receiver in direct sunlight
at all times.  The first problem can be gotten around with orbital
reflectors, but that brings back the orbital debris problem (and makes
the transmission paths even longer).

Perhaps a better solution would be to use laser transmission from very
large orbits, perhaps using radiation pressure to keep the stations in
positions from which any debris is rapidly removed.  But laser
transmission has its own problems.

    Paul F. Dietz
    [e-mail]

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

Date: Fri, 8 Jan 1993 20:13:51 GMT
From: Mike Kirby <[e-mail]>
Subject: Justification for the Space Program
Newsgroups: sci.space

In article [e-mail], [e-mail] (Paul Dietz) writes:
>In article <[e-mail]> [e-mail] (James L. Felder) writes:
>
>
>
>
>> No, to unreliable.  Terrestrial solar energy has a problem because of
>> intermittent illumination.  Either a large storage capacity must be
>> included in the system, or another source must come on-line at night and
>> during periods of cloud cover.  The large required land area makes solar
>> problematic for large portion of the world.  Plus places like Cleveland
>> goes days or weeks with hardly a glimpse of the sun.
>
>Surely, means to move energy in both time and space would be needed.
>There are serious economic limits on this today, but there is no
>reason to think these limits cannot be extended.
>
>As for land area: current world energy use is only 1/10,000 of the
>sunlight hitting earth's surface.  Restricting ourselves to
>continents, and assuming a 20% efficieny, we end up using a couple of
>percent of the land area of the planet.
>
>

Of course, what is the ecological effect of covering 1% of the earth's
land mass?  Unless it is a distributed grid (i.e. everyong has their
own solar panel on their roof) I would assume that solar collection would
be located centrally.  This would require large tracks of land and would
effectively kill anything on the land.  Bright sunny areas like deserts would
be ideal for such facilities, of course these deserst also support ecologies that
depend very heavily on the sun.

Nuclear is a much better solution as long as the political ramifications are
handled effectively. I am not encouraged though.

>
>    Paul F. Dietz
>    [e-mail]

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

Date: Fri, 8 Jan 1993 22:30:21 GMT
From: "Edward V. Wright" <[e-mail]>
Subject: Let's be more specific (was: Stupid Shut Cost arguement
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Brian Stuart Thorn) writes:

>  Are you saying that they had not even started production of
>  Pegasus No.2 in April, 1990? Maybe this is true, but it seems
>  a very strange way for OSC to be operating.

They might have had a second, or even a third Pegasus under
construction when the first one flew.  But a typical aircraft
might fly 400 times before it's declared operational.  How
long would it take to build and launch 400 expendable rockets,
even if you could afford to?

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

Date: 8 Jan 93 22:01:41 GMT
From: Dave Michelson <[e-mail]>
Subject: Making Antimatter (was: *** BUSSARD RAMSCOOP ***)
Newsgroups: sci.space

Several postings ago, I referred to an article in a recent issue of
Scientific American that might be of interest.  The complete citation is:

Gerald Gabrielse, ``Extremely Cold Antriprotons,'' Scientific American,
vol. 267, no. 6, pp. 78-80, 85-89, Dec. 1992.

`Cooling and trapping of these particles at energies one ten-billionth of
 what was feasible six years ago should make possible production of the
 first antimatter atoms.'

Granted, the article doesn't deal with mass production of antimatter
but it *is* both recent and topical.  An ion trap of the type described
in the article may be suitable for "bulk storage and transport" of anti
protons in the future...  Certainly it would be more convenient than
a storage ring :)

--
Dave Michelson
[e-mail]

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

Date: Fri, 8 Jan 1993 19:18:36 GMT
From: Edmund Hack <arabia!hack>
Subject: Marketing SSTO
Newsgroups: sci.space

>Airplanes made it possible
>to build Las Vegas in the dessert.

Cake, pie, icream or pudding? :-)

>You have to allow for things like Las Vegas in space.

It is anticipated that a combination Poconos Honeymoon Resorts/Mustang
Ranch will be the major allure of a 0g tourist facility.

> And if you're
>trying to build public support, you need to talk about flashy
>things like Las Vegas, rather than mundane stuff like air mail.

"Come on 6, baby needs a pair of Heavy Boots!"

--
Edmund Hack - Lockheed Engineering & Sciences Co. - Houston, TX
[e-mail] - I speak only for myself, unless blah, blah..
"You know, I think we're all Bozos on this bus."
"Detail Dress Circuits" "Belt: Above A, Below B" "Close B ClothesMode"

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

Date: Sat, 9 Jan 1993 00:53:00 GMT
From: Ron Baalke <[e-mail]>
Subject: Mars Observer Update - 01/08/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary

Forwarded from the Mars Observer Project

                        MARS OBSERVER STATUS REPORT
                             January 8, 1993
                               1:30 PM PST

The spacecraft is in Array Normal Spin and continues to perform as
expected. Teams are continuing to study the Attitude Control Subsystem
miscompared star problem.

Downlink is via the HGA (High Gain Antenna) at 2 kilobits per second.
Uplink is at 125 bps using the LGA (Low Gain Antenna). HGA calibration
activities were completed last evening.  Those calibrations indicate
HGA performance to be nominal.

With completion of C5 B as scheduled at 7:00 PM last evening, no flight
sequences are currently active.  This is to provide a ten day window to
allow upload of a new Flight Software build.

Teams are preparing Flight Software Build 7.1.1 for uplink on January 13
though 15.  Build 7.1.1 contains changes to AACS (Attitude and Articulation
Control Subsystem) Fault Protection logic determined to be necessary by
the Spacecraft Team.  These changes are not related to the Celestial
Sensor Assembly miscompared star situation.

The next Flight Sequence, C6 B (necessary C6 A activities were moved
into C5 B) is scheduled to go active on January 18.

Ka Band Link Experiment (KaBLE) activities have begun and are scheduled
to take place daily through January 12.  There are additional KaBLE
opportunities projected for January 16 and 17.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Choose a job you love, and
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | you'll never have to work
|_____|/  |_|/       |_____|/                     | a day in your life.

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

Date: Sat, 9 Jan 1993 02:15:54 GMT
From: [e-mail]
Subject: Perseid storms 1993/1862
Newsgroups: sci.astro,sci.space

Thank you to Paul Schlyter, Stockholm, Sweden who emailed much interesting
information including:

(all UT)
perhelion 1862 Aug. 23.41,
full moons:
1860 Aug  1.73  (partial lunar eclipse, 44% of Moon in umbra)
1860 Aug 31.37  (no eclipse)
1861 Aug 20.49  (no eclipse)
1862 Aug  9.91  (no eclipse)
1863 Aug 28.87  (no eclipse)
1864 Aug 17.57  (no eclipse)


We are still looking for the precise dates of maxima from 1860-1864 incl. Can
anyone help? Or can only Brian Marsden satisfy such exacting requests!?

T.Ryan and D.Moore, Astronomy Ireland, P.O.Box 2888, Dublin 1, Ireland.
[e-mail]

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

Date: 8 Jan 93 19:32:13 GMT
From: Francois Yergeau <[e-mail]>
Subject: Question about SETI
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>In answer to Francois Yergeau (8 Jan 93 04:10:48 GMT):
>>
>> [ false affirmations in a New Scientist article by N.Henbest, and
>>   my rebuttal deleted ]
>
>Rather obvious. I think (at least, I hope) that Nigel Henbest was making
>some kind of journalistic approximation. Most New Scientist's readers
>are not professional scientists, just amateurs.

Right.  And possibly some of the sci.space readership is not well
versed in optics, and thus not in a position to judge the veracity of
Henbest's prose.  I thought it was worth the trouble to debunk his
extravagant claims about laser communications.  And you would be very
generous to qualify his assertion that a laser does not spread out as a
"journalistic approximation", when it is patently false.  The
journalist's role is to inform the reader, not mislead him.

>It seems that you have about the same credentials as Stuart Kingsley:
>
>< [ Kinsgley CV deleted ]
>
>It seems also that you disagree with him (see EJASA, January 1993).

I didn't read much of Mr Kingsley's paper, because I don't have much
interest in SETI.  My disagreement, however, is not so much with the
idea of optical SETI as with the case Henbest made for it, using either
false or misleading statements, or, if you prefer, too much
journalistic approximation.  Optical SETI may be a good idea, but
defending it with bogus arguments implies either ignorance or
dishonesty.

--
Francois Yergeau ([e-mail]) |  De gustibus et coloribus
Centre d'Optique, Photonique et Laser    |  non disputandum
Departement de Physique                  |          -proverbe scolastique
Universite Laval, Ste-Foy, QC, Canada    |

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

Date: Fri, 8 Jan 1993 19:26:34 GMT
From: Edmund Hack <arabia!hack>
Subject: RTG's on the Lunar Module
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>> The radiation hazard from plutonium 238 is insignificant; it's pretty much
>> a pure alpha emitter, and human skin stops alpha particles completely.  (A
>> sheet of paper will do likewise.)  You don't want to eat the stuff, but so
>> long as it stays put, no sweat.
>
>Somewhere in the recesses of my mind lies a memory of a scientist
>who offered to eat some plutonium if the journalist covering the
>event would eat the same amount of caffeine.  No takers, obviously,
>but does this mean that it would be safe to eat plutonium?  If it's
>inert it should be passed in due course with only the mucus coating
>the alimentary canal getting irradiated.
>
Edward Teller offered to eat a spoonful of Plutonium Oxide if the
reporter would eat a spoonful of _cyanide_.  Pu oxide is inert and would
be passed through the digestive system in a few days.  However, metallic
Pu _is_ very toxic, is absorbable into the bloodstream and would proceed
to kill you through several mechanisms at once.

Snorting the Pu Oxide would not be a good thing, as the lungs are
susceptable to developing cancer via alpha irradiation.  Pu (in any
form) is not the "most toxic substance on earth" as pure Botulism toxin
in more dangerous if ingested, as are a number of neurotoxins if
administered into the body.

--
Edmund Hack - Lockheed Engineering & Sciences Co. - Houston, TX
[e-mail] - I speak only for myself, unless blah, blah..
"You know, I think we're all Bozos on this bus."
"Detail Dress Circuits" "Belt: Above A, Below B" "Close B ClothesMode"

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

Date: Fri, 8 Jan 1993 19:30:13 GMT
From: Ed McCreary <[e-mail]>
Subject: RTG's on the Lunar Module
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:
>In article <[e-mail]>, [e-mail] (Henry Spencer) writes:
>> The radiation hazard from plutonium 238 is insignificant; it's pretty much
>> a pure alpha emitter, and human skin stops alpha particles completely.  (A
>> sheet of paper will do likewise.)  You don't want to eat the stuff, but so
>> long as it stays put, no sweat.
>
>Somewhere in the recesses of my mind lies a memory of a scientist
>who offered to eat some plutonium if the journalist covering the
>event would eat the same amount of caffeine.  No takers, obviously,
>but does this mean that it would be safe to eat plutonium?  If it's
>inert it should be passed in due course with only the mucus coating
>the alimentary canal getting irradiated.
>

Edward Teller.  The problem with Pu-238 is long term exposure.  You
don't want to breathe in particulate plutonium and let it sit in your
lungs.  I think it was Feyman who describes holding a sphere of
plutonium in his hands and how warm it was due to alpha emissions.


--
Ed McCreary                                               ,__o
[e-mail]                       _-\_<,
"If it were not for laughter, there would be no Tao."  (*)/'(*)

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

Date: Fri, 8 Jan 1993 19:21:16 GMT
From: [e-mail]
Subject: Subjective Safety Measure(Re: man-rating)
Newsgroups: sci.space,sci.aeronautics

It would seem to me that whether probability of exit or deaths per passenger
mile is a more valid measure would depend on why you want the info.

For example, the airplane vs car comparison probably makes more sense in terms
of miles, because I interpret the question to be "If I want to travel from
Boston to Chicago, is it safer to use a car or a plane."  Chances are
that you will exit the car more times between Boston and Chicago than you will
by plane.

On the other hand, if you are comparing it with the shuttle, the "per mile" is
specious.  The fact that you went 2 million miles to get from LC39 to the
runway across the island, or the fact that the runway is 2 miles from the pad
is irrelavent.  So in this, I think I would compare entry/exit.

The other interesting part of this is that most airplane fatalities
(and so far all shuttle fatalities) occur close to entry/exit.  In other words
the length of the trip is unlikely to be significant to the probability of
fatality.  I doubt this is strictly true in cars.  While I have heard that most
accidents happen within 10 miles of home, I suspect that is because most of
person-miles spent in cars are within 10 miles of home.

Anyway...(why did I get into this discussion!!!!???)

Burns

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

Date: 8 Jan 93 17:23:14 GMT
From: Thomas Hagadorn <[e-mail]>
Subject: Subjective Safety Measure(Re: man-rating)
Newsgroups: sci.space,sci.aeronautics

In article <[e-mail]> [e-mail] (Ken Arromdee) writes:
|In article <[e-mail]> [e-mail] (Thomas Clarke) writes:
|>The rating of transportation system safety by fatalities per
|>passenger mile always struck me as bogus.  Subjectively, what
|>matters is the probability of exit.  That is if I climb in and
|
|In that case, the probability of exit can be made as low as you want, for an
|automobile, by stopping along the way.  (The risk of dying on the trip stays

  Actually, I believe replacing passenger-miles with passenger-hours is
a more appropriate metric, however, I think the airline industry still
beats the automotive here as well (someone with source to the numbers
might like to check).

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

End of Space Digest Volume 16 : Issue 028
------------------------------