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Date: Thu, 15 Feb 90 01:33:43 -0500 (EST)
Subject: SPACE Digest V11 #44

SPACE Digest                                      Volume 11 : Issue 44

Today's Topics:
        Re: measurement standards (aerospace)
      Re: Energy (was Re: Spacecraft drives and fuel efficiency)
               Re: inter stellar travel
               Re: inter stellar travel
             Re: LDEF experiments
      Re: Energy (was Re: Spacecraft drives and fuel efficiency)
KSC groves sustain heavy loss during December 1989 freeze (Forwarded)
----------------------------------------------------------------------

Date: 13 Feb 90 21:47:56 GMT
From: skipper![e-mail]  (Al Bowers)
Subject: Re: measurement standards (aerospace)

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

>>From: cs.utexas.edu!samsung!munnari.oz.au!cluster!metro!otc![e-mail]  (Greg Wilkins)
>>Subject: Re: metric vs. imperial units

>>You guys just keep making excuses!!!!   Yes an entire country can convert
>>from imperial to metric -> Eg Australia and we have the safest airline in
>>the world.  If any airline or spaceflight relies on the pilots ability to
>>do mental arithmetic in his native units, then it aint safe!!

Having lived in Australia for 3+ years and going to school there I
must agree that the U.S.'s reluctance to accept the SI system is not
doing us any good.  Technologically or comercially.  Si and/or metric
is not that painful, too much of the Not Invented Here syndrom in the
U.S.  Or perhaps the nonaknowledgement of the rest of the world?

>> - The rest of the world is using it

>Agreed.

>> - To some extent, when designing physical systems, recurring decimal
>>>places can be avoided, hence round off errors can be reduced.

>For shame! That's one of the few areas in which the "standard" system really
>shines, since it was a major design criterion. For instance, express 1/3
>of a foot in inches (4). Now try 1/3 of a meter in mm (333.33333333333...).

... lots deleted ...

>and 500 - only 14 factors. In either case, the most useful factors are
>probably those <= 20, still a ratio of 12 to 6.

This is not really a valid argument as an engineer would NEVER spec
something as 1/3 of a foot!

>> - To do any sort of calculation by computer, metric is by far better than
>>   imperial, thus reducing the possibility of program error.

>That depends on how you express the terms. If metric distances are given
>as "3 kilometers, 768 meters, 122 millimeters", and "standard" distances
>are given as "11256.3827165 feet", then the metric system will lose out.

... more deletions ...

>>I am told that America is the most inwardly looking nation on the planet,
>>and boy does it show!!!

I'm afraid I have to agree.  Both my in laws are in education and tour
Europe every summer.  I always hear from them about how the Europeans
don't do things the way they are supposed to be done.  This from
American educators!  In my family (mixed race) we were taught to
respect others and their customs and beliefs.  I grew up on three
continents (never learned a language other than English though) and I
wish that kind of perspective could be taught here at home.

>Please convince the Central American nations of this fact - it would be very
>helpful to our diplomatic relations! :-) Actually, I suppose this is partly
>correct and partly incorrect, and attitudes vary over time. Since "inwardly
>looking" has no clear definition, commenting on this is sort of like trying

... more deleted ...

I seriously doubt that 90% of the people on this net could tell you
the capitol of Australia and the state it resided in (FYI Canberra in
the Australian Capitol Territory, the state bit was to throw you off)
or what country Singapore is in, or find Lebanon on a map or ...  I
could go on and on but I'd only depress myself.  Now go to another
country, and ask their school children if they have heard of
Sacramento.  Or Seattle, or Minneapolis, or Dallas-Fort Worth.  We as
a nation are too self centered.

>>If you guys are serious about international
>>cooperation you have to pick a set of common units (for more cost and
>>saftey reasons), and when it comes to the choice metric wins hands down.

Absolutely!

>I think things are headed in that direction - it's just slower in some fields
>than in others. Also remember that the US is not the only country to stick to
>"peculiar" standards. Europe has been blocking an international standard on
>HDTV television broadcast format unless it's PAL-compatible (or SECAM?) while
>the US and Japan are willing to settle on an extension of NTSC.

So from this I gather NTSC is 'RIGHT' but PAL or SECAM is 'WRONG'!?!
Listen to yourself!  Our demand for compatibility is okay but yours
isn't!  Haven't you read a thing that Greg has written!?!

>>Anyway, to sum up, stop making excuses, start making changes, put a bit
>>of effort in , and maybe, just maybe you will be able to talk technical
>>with the rest of the world in twenty years or so!

The U.S. will have to do what was done in Australia, pass a law making
SI or metric the standard and make our current system illegal.  Phase
outs and partial change overs will not work.  Bite the bullet and do it!

>Or maybe we'll be able to use subterfuge to get you to talk technical with
>us. Haven't you folks in metric countries wondered why your integrated
>circuits have a pin spacing of 2.54mm? :-) :-) :-) :-)

The sad thing John is that you believe you're making a joke, but the
joke is on all Americans (read that U.S. citizens).  I've been there
and believe me we gotta get our heads out of the sand...

--
Albion H. Bowers  [e-mail]  ames!elxsi.dfrf.nasa.gov!bowers
         NASA Ames-Dryden Flight Research Facility, Edwards, CA
                  Aerodynamics: The ONLY way to fly!

                     Live to ski, ski to live...

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

Date: 14 Feb 90 03:38:56 GMT
From: zaphod.mps.ohio-state.edu!usc!cs.utexas.edu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Energy (was Re: Spacecraft drives and fuel efficiency)

In article <[e-mail]> [e-mail] (Christopher Neufeld) writes:
>
>   For 2H + 2H -> 3He + n, only one part in 1200 of the mass is converted
>to energy, so you'd need at least 3.6 billion tons of deuterium, which is
>as much deuterium as is contained in a cube of sea water 28.8 kilometres on
>edge, for each atmosphere of pressure.
>
   Sorry, make that about 60 km on edge. I forgot that water contains a bit
of oxygen too!


--
 Christopher Neufeld....Just a graduate student  |
 [e-mail]              | "Vulcan has no moon."
 [e-mail]                    | "I'm not surprised!"
 "Don't edit reality for the sake of simplicity" |

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

Date: 14 Feb 90 20:08:16 GMT
From: zaphod.mps.ohio-state.edu!uwm.edu!mailrus!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: inter stellar travel

In article <[e-mail]> [e-mail] (Patrick Brewer) writes:
>I know a few years back there was discusion about particles that might
>travel faster than the speed of light. How have results of that thinking
>turned out?

They are still a sort of vague theoretical possibility, but it takes some
serious contortions to get around all the theoretical problems, and there
is the major objection that nobody's ever seen one.  If they exist, either
they are exceedingly rare or they don't interact with normal matter much.

>To have useful interstellar travel by people we would need
>speeds in the range of light years per day or more.

Nonsense.  Transcontinental commerce was widespread when transcontinental
travel times were measured in months.  Scientific exploration and perhaps
colonization remain practical with travel times of 20 years or more.
(Indeed, if you postulate world-ships, colonization is practical with
travel times measured in generations.)  For commerce, light-years per year
would suffice, although light-years per month would be a whole lot better.

Also, don't forget the complicating effects of relativistic time dilation.

>    At the speed of light it would take a little over 4 years to reach
>the nearest star. What are the chances that it would have a planet that
>man could live on....

Uncertain.  One would prefer to know before starting the trip. :-)  Current
theory is that planets are normal around Sun-like stars.  The chances for
habitable planets are harder to figure.  There is no specific reason now
known for Earth to be a low-probability accident (the notion that the
habitable zone around a star is very narrow seems to have been largely
disproven), but it would be nice to have some more data points.

Of course, the space-colony enthusiasts would reply "who needs planets?".
--
"The N in NFS stands for Not, |     Henry Spencer at U of Toronto Zoology
or Need, or perhaps Nightmare"| uunet!attcan!utzoo!henry [e-mail]

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

Date: 14 Feb 90 02:28:55 GMT
From: pasteur!graft![e-mail]  (Scott Silvey)
Subject: Re: inter stellar travel

In article <[e-mail]>, [e-mail]
(Patrick Brewer) writes:

} What are the chances that it would have a planet that
} man could live on.

I'm sure that the chance of walking up to a planet and finding it
  ready and capable of supporting human life "as is" is vastly
  miniscule.  Ok, imagine that we manage to find a planet supporting
  life that is somewhat similar to what we know here on earth (which
  seems to me to be tremendously unlikely).

One thing I would consider is the compatibility of life forms from two
  ecosystems which developed independently.  Every life form on earth
  has had millions of years to adapt to its little niche in the
  ecosystem.  It is an unimaginable possibility for us to be able to
  drop in on a living ecosystem which has developed apart from earth
  to find that all we have to do to live there is to pitch a tent!

Think of what happens when you visit Mexico for a few days.  Many
  people are quickly overcome by local germs and parasites because
  their body has not had a chance to develop natural immunities to
  these things.  The converse problem has occurred in cases where
  explorers in history have introduced "common" diseases to
  civilizations in which the people have never developed the proper
  resistances.  The resultant plagues in these cases were devastating
  to the natives.

Other examples of this have occurred when foreigners have introduced
  non-native animals and plants into a country where these life forms
  have no natural enemies.  The result is often that the new form grows
  in an uncontrolled manner, voraciously consuming natural resources
  which native species need to live on.  The new species essentially
  extinguishes the native ones.

So now, imagine what happens when a human being, laden with all sorts
  of "harmless" living parasites unheedingly drops in on a new
  life-bearing planet.  Not only will he contaminate the native life
  system with new "unnatural" creatures, but he himself will presumably
  become immediately susceptible to myriads of native parasites
  himself.  (Of course, a parasite is only a "parasite" when it invades
  some living host and lives there).

Most likely (if all the above conjectures are true), we would have to
  virtually destroy the entire existing ecosystem (down to every
  microbiological creature and virus) and "terra-form" the planet before
  we could live there comfortably.  And if this were true, we might as
  well try to work with something like venus rather than bother with an
  already evolved living planet.

Who knows, maybe even exposure to strange, new, complex chemicals could
  prove exotically deadly to earth-based life (and vise-versa).

Now, I'm just thinking all of this up, since of course, nobody really
  knows these things.  But it seems to me that just this one problem of
  biological compatibility would prove exceedingly complicated to
  colonization efforts, assuming that someone even managed to find a
  planet bearing life on a scale of complexity similar to that of Earth.

What do other people think?  Can anyone out there who has a background
  in biological sciences provide some more light on these ideas?  Am I
  explaining my ideas clearly?

} (I find perfectly reasonable to assume that most
} stars have planets that make up a star system (? like "solar system").)

I don't know how reasonable this assumption is.  Especially closer in
  towards the center of the galaxy where the stars are older and
  consist of mainly hydrogen and helium.  I believe some astronomers
  have detected optical affects around some nearby stars which they
  think might be caused by planets, but other than this, all we really
  have to go on is our own solar system.  Who knows, maybe we are
  unusual.  When 99% of the universe is hydrogen and helium, why would
  it be common to find stars with large rocky balls orbiting them?

Scott ([e-mail])

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

Date: 14 Feb 90 19:57:23 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: Re: LDEF experiments

In article <[e-mail]> [e-mail] (Jon Albers) writes:
>With all the talk about LDEF, no that it is back, could someone post a list
>of the experiments it carried?  I know they are in the process of studying
>the LDEF right now, and I would be real interested to find out how all
>those '1 year' experiments lasted all this time..

Retrieve file 6.9.5 from the SPACE archive on ames.arc.nasa.gov.  This is a
fact sheet and list of experiments for the LDEF.  Refer to previous messages
on how to access the archive, or drop me a line if you missed those.


                            -Peter Yee
                            [e-mail]
                            ames!yee

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

Date: 14 Feb 90 00:17:22 GMT
From: zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Energy (was Re: Spacecraft drives and fuel efficiency)

In article <[e-mail]> [e-mail] (Paul Dietz) writes:
>
>Exercise for the day: if you wanted to blast the atmosphere off
>Venus in preparation for terraforming, how much antimatter would you
>need?  If you use fusion bombs, how much deuterium?
>
   OK, I'll try this. Let's define "blast the atmosphere off" as meaning
sending the atmosphere up at escape velocity, and we'll assume that the
internal energy of the gas cannot be harnessed to help the process. Then,
the energy required to do this is:
   2.82 x 10^26 Joules per atmosphere of surface pressure (I don't know
this value, but I believe it's more than ten atmosphere on Venus).
   This is three million tons mass-energy equivalent per atmosphere of
pressure, at 100% efficiency. So, you'd need at least 1.5 million tons of
anti-matter, and in practice probably at least ten times that amount, for
each atmosphere of surface pressure.
   For 2H + 2H -> 3He + n, only one part in 1200 of the mass is converted
to energy, so you'd need at least 3.6 billion tons of deuterium, which is
as much deuterium as is contained in a cube of sea water 28.8 kilometres on
edge, for each atmosphere of pressure.

   Of course, this could be a trick question. You might use some energy to
deflect an asteroid into the planet with the release of much more energy.
Then the energy required depends on how long you want to wait. Wait long
enough and the energy cost is zero, because the when the sun swells to
red-giant it will boil all the atmosphere off Venus :-)

>    Paul F. Dietz
>    [e-mail]


--
 Christopher Neufeld....Just a graduate student  |
 [e-mail]              | "Vulcan has no moon."
 [e-mail]                    | "I'm not surprised!"
 "Don't edit reality for the sake of simplicity" |

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

Date: 14 Feb 90 17:30:29 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: KSC groves sustain heavy loss during December 1989 freeze (Forwarded)

[And you thought we just did aeronautics and space work! -PEY]

          Bruce Buckingham                             Feb. 14, 1990

          KSC RELEASE NO. 26 - 90


          KSC GROVES SUSTAIN HEAVY LOSS DURING DECEMBER 1989 FREEZE


               The citrus fruit harvests at KSC sustained a major loss
          because of the extremely low temperatures experienced in December
          1989. Recent projections show the losses could be greater than 60
          percent for the current season.

               Early and mid-season varieties of oranges experienced as
          much as a 40 percent loss. Late-season varieties, such as
          valencias, may suffer a 50 to 60 percent loss since the fruit has
          not met maturity standards and couldn't be harvested immediately
          following the freeze.

               Grapefruits and tangerines could see losses as high as 90
          percent. This is due to the fact that the majority of processing
          plants were attempting to salvage as much of the orange crop as
          possible, and they were not processing grapefruits or tangerines.

               Minor damage was reported to the citrus trees themselves and
          the recent new growth of foliage is being taken as a good sign
          the trees will have an excellent chance for full recovery without
          much dieback. Early projections call for a following season crop
          to be fairly good.

               In 1989, 1530 acres on KSC produced approximately 500,000
          boxes of citrus yielding gross sales of about $2.2 million.

               Groves on KSC are operated under lease to local growers.
          Profits from the sales of citrus grown on KSC property is
          returned to the U.S. Treasury.

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

End of SPACE Digest V11 #44
*******************