HDTenEightyP/NetNews huggingface dataset:
From: m1phm02@fed.frb.gov (Patrick H. McAllister)
Newsgroups: rec.arts.sf.science
Subject: Re: Laser weapons
Date: 3 Sep 92 02:43:33 GMT
Reply-To: m1phm02@fed.frb.gov (Patrick H. McAllister)
Organization: Federal Reserve Board, Wash, DC

The basic difficulty with use of lasers as weapons has to do with the power requirements. A weapon generally needs to deliver a lot of power for a very short period of time. Lasers can certainly be made to do this -- but how do you get the power INTO the laser that fast? Back in my youth, I visited a laser fusion experiment at Lawrence Livermore Labs. The actual lasers were reasonably compact, and delivered an enormous amount of power in a short burst. The capacitor banks that powered them filled a large b


uilding, however. The lasers themselves would have been fine for weapons -- but what to do about the power supply?

We currently know how to build lasers pumped by several types of primary fuel:
(1) electricity (eg. flash lamps for ruby lasers, RF fields for gas lasers)
    Here the problem is to generate a sufficiently powerful pulse of
    electricity for a short period of time (your hand-held laser is not much
    use if it has to be plugged into a couple of tons of capacitor in order to
    work); there are possible solutions for vehicle-mounted weapons (it might
    might be possible to put the capacitors in a tank), but I don't see much 
    hope for hand-held weapons (even Mr. Fusion is unlikely to be able to 
    deliver the power pulses needed).
(2) chemical (eg. hydrogen flourine)
    The problem with these guys is the inefficiency -- a gun is really a pretty
    efficient way to transfer chemical energy from point A to point B in a short
    period of time. To the best of my knowledge, the efficiency of chemical
    lasers is much lower. There might be some reason to use the laser approach
    under circumstances in which the propagation time is important, eg. over
    long ranges in space, where the target might have time to dodge a
    projectile.
(3) nuclear (the Star Wars nuclear-pumped X-ray lasers)
    There may be some situations in which blowing up a nuclear bomb in order to
    be able to fire a one-use-only weapon is a decent trade-off, but they are
    going to be few and far between.
The basic problem is inventing a power supply that can produce a very large pulse of power for a short period of time. Lasers will only be useful as weapons for someone who has such a power supply but lacks any more efficient way to apply the energy toward destroying the target. Example: imagine Mr. Fusion, a back-pack-sized fusion power supply that can produce large pulses of power. Presumably, the technology could be used to produce a small fusion bomb, which would be much more energy-efficient. A bomb m


ay not be appropriate for the military mission, however -- that's why we have sniper rifles as well as mortars today. In this case, a laser may be the way to go. There are going to have to be some pretty amazing technological developments in power engineering, however, before a laser weapon becomes more practical than a projectile weapon of the the same size.

Pat
Newsgroups: rec.arts.sf.science
From: ins450m@aurora.cc.monash.edu.au (T.F. Eccles)
Subject: Re: Ringworlds
Organization: Monash University, Melb., Australia.
Date: Mon, 31 Aug 1992 07:50:50 GMT

gletty@ux1.cso.uiuc.edu (Bruce Gletty) writes:

>holland@geop.ubc.ca (Stephen Holland) writes:

>>In article 3270@nwnexus.WA.COM, elf@halcyon.com (Elf Sternberg) writes:
>>>In article <15250@suns6.crosfield.co.uk>
>>>     jc@crosfield.co.uk (jerry cullingford) writes:
>>>

>Both Ringworlds and Dyson Spheres still suffer from the instability problem. The
>star has no force acting on it to keep it in the center of the system. I'm not
>sure if there exists a solution for either, Niven kludged one up in Ringworld Engineers, 
>but it seemed a little hokey. Its probably easier for a ring than a sphere.

um..... wouldn't almost equal light pressure keep the Dyson Sphere stable...
Its just a thought....

Eccles

"Humans have mastered a power akin to that which drives the sun,
that of nuclear fission.... and they use it to boil water."
From: f3w@mentor.cc.purdue.edu (Mark Gellis)
Newsgroups: rec.arts.sf.science
Subject: Re: Laser weapons
Date: 2 Sep 92 13:57:23 GMT
Organization: Purdue University Computing Center


The information I have is from a friend who has done research on lasers
for his engineering degree.  While one can never know what might happen
if there are radical breakthroughs, he thinks lasers might remain fairly
large and inefficient because of certain physical requirements (which
were somewhat technical and I admit I did not understand all of them).

In a vacuum (i.e., spacecraft weapons), lasers can be smaller because a 
lot of many lasers is vacuum-producing equipment (some lasers need a vacuum
to function).  We were talking about 10 kg./kilowatt output for a hydrogen-
flourine laser.

Chemical lasers are not very efficient.  If we can get free electron lasers
to work that are not very large, Dean Ing and L. Myrabo suggest we could get
up to 40% efficiency.  (See THE FUTURE OF FLIGHT, good book.)

The long and the short of it is that if you want lasers that will take out
people, you could build a really big sniper rifle (like the size of a .50-
calibre machinegun, or bigger, not counting the power supply) that would
work in vacuum and blow a nice hole in a person (10-kilowatt output--really,
10-kilojoules/sec.--will kill someone).  In an atmosphere, increase the size
of the weapon by an order of magnitude, probably.  

Most likely, lasers will be used as "field artillery," big, multi-ton weapons
mounted on spacecraft or space habitats and used mostly to destroy missiles 
or other spacecraft.  That seems the most efficient way to do use them.  By
the way, I believe a free electron laser can be "tuned" to different frequen-
cies, making it much harder for a target to use reflective "armor" to protect
itself.  After all, what reflects one wavelength might have a lot of trouble
with another wavelength.

Hopes this helps and/or stimulates further discussion.

Mark
Newsgroups: rec.arts.sf.science
From: neufeld@helios.physics.utoronto.ca (Christopher Neufeld)
Subject: Re: Laser weapons
Organization: University of Toronto Physics/Astronomy/CITA
Date: Thu, 3 Sep 1992 20:19:23 GMT

In article <1992Sep3.184558.4898@spss.com> markrose@spss.com (Mark Rosenfelder) writes:
>
>Guns with bullets seem to be pretty energy-efficient, but they're not
>very futuristic, are they?  Can anyone think of anything that's likely
>to replace them?

   I imagine that will depend on the application. An electromagnetic
launcher weapon could have certain advantages, such as robust ammunition
(don't have to worry about dropping a copper nail or getting one hot). It
also would not pollute the vicinity of the wielder in poorly ventilated
spaces, which could be important. Muzzle flash would be eliminated,
though there are flash suppressors for current guns, so this isn't
necessarily a big change. Note that it's unlikely the gun would be
silent, since I'm told the noise of a gunshot comes primarily from the
supersonic flight of the projectile. It might be possible to design a
projectile shape which minimizes the shockwave, and which could be more
easily fired by an electromagnetic launcher than by a chemical charge in
its tail (which sort of restricts the trailing edge geometry).
   Another possibly useful enhancement in the abilities of hand weapons
would be to make the ammunition less specialized. A gun which could fire
anything of roughly the right size and shape, from a rock to a peach pit
to a tranquilizer dart would certainly make a more versatile weapon than
the ones available now. This isn't my own idea, you see it in Brian
Daley's "Adventures of Alacrity Fitzhugh" books.

   It is going to come down to applications in the end. An assassin's
weapon will be designed to meet certain criteria which are likely to be
very different from those of a soldier or of a police officer. It is
probably best to think first of what use the weapon will be put to, what
current technology provides to fill that niche, and what limitations that
current technology has which might be overcome by some technical advance.
Let your weapon "evolve" rather than just exist, and it will seem more
consistent to the reader.

-- 
 Christopher Neufeld....Just a graduate student  | Confidence is the feeling
 neufeld@helios.physics.utoronto.ca    Ad astra  | you have before you
 utzoo.utoronto.ca!generic!cneufeld              | understand the situation.
 "Don't edit reality for the sake of simplicity" |
From: swf@teradata.com (Stanley Friesen)
Newsgroups: rec.arts.sf.science
Subject: Re: dragons were dinosaurs?
Date: 26 Aug 92 17:53:27 GMT
Reply-To: swf@tdat.teradata.com (Stanley Friesen)
Organization: NCR Teradata Database Business Unit

In article <1992Aug20.164929.631@pbhya.PacBell.COM> whheydt@PacBell.COM (Wilson Heydt) writes:
|
|A 'few hundred million years' certainly is a long time--but not an
|appropriate figure for dealing with dinosaurs--who were around from
|about 210 million years ago until (if Walter Alvarez is correct) 64.98
|million, plus or minus 50,000, years ago.

Are you sure of those accuracy figures?  +/-50,000 seems awefully precise
for a 65 MY date.  I would think that +/-500,000 would be more likely.
[isotopic dating is good, but not *that* good].
-- 
sarima@teradata.com			(formerly tdatirv!sarima)
  or
Stanley.Friesen@ElSegundoCA.ncr.com
Newsgroups: rec.arts.sf.science
From: gletty@ux1.cso.uiuc.edu (Bruce Gletty)
Subject: Re: Ringworlds
Organization: University of Illinois at Urbana
Date: Fri, 28 Aug 1992 19:13:29 GMT

holland@geop.ubc.ca (Stephen Holland) writes:

>In article 3270@nwnexus.WA.COM, elf@halcyon.com (Elf Sternberg) writes:
>>In article <15250@suns6.crosfield.co.uk>
>>     jc@crosfield.co.uk (jerry cullingford) writes:
>>
>>>Benefits [of a ringworld]? _Lots_ of living space, and cheaper than a
>>>dyson sphere.
>>
>>   Actually, I always thought that the major benefit of a Ringworld
>>when compared to a Dyson Sphere Classic (see Dyson's original works to
>>see what a true Dyson Sphere is) is that a Dyson Sphere requires a sort
>>of technology that we presently find incomprehensible (i.e. artificial
>>gravity) to make the interior surface livable.
>>
>>            Elf !!!
>There is a way to make a Dyson Sphere work with-out artificial gravity.  Just 
>spin the sphere.  That way you get Earth-normal (or whatever) gravity near the
>sphere's equator and a steadily decreasing gravity field as you move further away
>from the equator.  At the poles you have no gravity, which migh be useful for the
>ball-bearing industry.

Both Ringworlds and Dyson Spheres still suffer from the instability problem. The
star has no force acting on it to keep it in the center of the system. I'm not
sure if there exists a solution for either, Niven kludged one up in Ringworld Engineers, 
but it seemed a little hokey. Its probably easier for a ring than a sphere.
Newsgroups: rec.arts.sf.science
From: hillyard@msc.cornell.edu
Subject: Re: Niven's teleportation & 2nd law of thermodynamics (was: Superconductors + the 2
Originator: hillyard@tiger.msc.cornell.edu
Reply-To: hillyard@msc.cornell.edu
Organization: Cornell-Materials-Science-Center
Date: Wed, 2 Sep 1992 20:47:31 GMT

From article <1992Sep2.114236.428@cine88.cineca.it>, by campo@sunthpi3.difi.unipi.it (Massimo Campostrini):
[...]
>    Any comment on this? Maybe the 2nd law of thermodynamics is
> supposed to be "less fundamental" or "less established" than the
> 1st by non-physicists?

It is less fundemental in the sense that it is a statistical law.  Entropy
can go down in a system--its just unlikely.

SEH
Newsgroups: rec.arts.sf.science
From: elf@halcyon.com (Elf Sternberg)
Subject: Re: Ringworlds
Originator: elf@halcyon.com
Reply-To: elf@halcyon.com (Elf Sternberg)
Organization: Pendor, UnLtd.
Date: Sat, 29 Aug 1992 06:18:20 GMT

In article <mwalker-280892145110@mwalker1.npd.provo.novell.com.>
     mwalker@novell.com (Mel Walker) writes:

>In article <1992Aug28.114139.3270@nwnexus.WA.COM>,
> elf@halcyon.com (Elf Sternberg) wrote:

>>    We don't even need Einstein to tell us why people can live on the
>> surface of a ringworld; Newton will do just fine.  Artificial Gravity
>> probably requires some kind of dependant power source and volatile
>> or dangerous hardware to continue operating.  Ringworlds (or, notably,
>> the Alderson Film Can design) require only brute force of the sort any
>> high school kid can understand.

>If we presently find "incomprehensible" the idea of artificial gravity, how
>can we say what it "probably" requires? Juuuuuuust asking.

   A good question; certainly the more advanced a science becomes, the
more inscrutable the hardware becomes to handle it.  I would argue that
I would trust a lever more than a laser to continue working.  Since
nobody has yet "accidently" stumbled upon the technique of generating
an accelerative field, we can assume it takes technology we're not yet
familiar with.

   "Dangerous" in the sense that, if an artifical gravity field fails
on an artificial world such as a Dyson Sphere, there's nothing to hold
the atmosphere down and everything near that particular emitter gets
blown into space.

   I could just as easily say that it requires "magic" to make an
artificial gravity field.  To a man of the 5th century, an internal
combustion engine certainly would have been magic!  But to you and I,
it is nothing more than a self-destructive peice of hardware based on
well-known and -understood principles.

         Elf !!!
-- 
Elf Sternberg    __   |     I have looked into the abyss, and the abyss
elf@halcyon.com  \/   | has looked into me.  Neither liked what we saw.
elf@polari.online.com |                              - Brother Theodore
Newsgroups: rec.arts.sf.science
From: jdnicoll@watyew.uwaterloo.ca (James Davis Nicoll)
Subject: Re: Niven's blunders (was:Superconductors + the 2nd law)
Organization: University of Waterloo
Date: Sun, 30 Aug 1992 16:59:23 GMT

In article <8_ty6z#@rpi.edu> kasprj@rpi.edu writes:
	(In response to someone whosename  I accidentally deleted)

>|> As a further backup, scatter statis caches around Known Space which 
>|> have very durable timing devices to turn them off after the radiation 
>|> has past. Let these contain a colony kit & terestrial "Gene Bank" 
>|> of the earth's bisphere (these can be living animals & plants). 
>|> To make shure that they do emerge, put some of the "arks" in prominent 
>|> orbits around interesting celestial objects. The first aliens to evolve 
>|> after the readiation will open them (only 2 or 3 billion years to wait.)
> 
> Heh, well, it almost worked for the Slavers and tnuctipun. Two or three 
>billion years of evolution would make the galaxy a strange place for our
>awakening humans. (-: While you're using the stasis field option, why not
>put entire cities under stasis fields? The kzinti did it on Warhead (Canyon),
>so we know the tech already exists. This may be cheaper than the GP hull 
>method. 

	Why stop with cities? The vicinity of a supernova is filled with
plasma, which should provide the conducting surface a stasis field needs.
Just  enclose the core in a Very Big  stasis field.

							James Nicoll
Newsgroups: rec.arts.sf.science
From: whheydt@pbhya.PacBell.COM (Wilson Heydt)
Subject: Re: Niven's blunders (was: Superconductors + the 2nd law)
Reply-To: whheydt@PacBell.COM (Wilson Heydt)
Organization: Pacific * Bell, San Ramon, CA
Date: Tue, 1 Sep 1992 17:45:34 GMT

In article <78796@ut-emx.uucp> slug@ccwf.cc.utexas.edu (Glen Anthony Graham) writes:
>Also, the GP hull was not impervious to whatever radiation the galactic 
>explosion was hurling at Known Space, but the Ringworld just happened to be
>completely impervious to this radiation.
> 
>As for leakage, with the core being some 20,000 lightyears away, that makes for
>an awfully small (apparant) source of radiation, so if the ring is aligned   
>along the radiation path, the opposite side would not really receive any 
>radiation.  

All the relevant figures are given in _Ringworld_ and _At the Core_.
The explosion cneters about 30,000 ly away from Known Space.  The
explosion 'fireball' is about 5,000 ly in diameter--therefore (without
actually using trig), the explosion subtends an angle of about 1/6
radian--about 10 degrees.  The ring is 1 million miles wide and 200
million miles in diameter, therefore the ring (as viewed across it's
diameter) subtends an angle of about 1/200 radian--or about 1/3
degree.

So:  A 20 minute ribbon across a 10 degree radiation source.

(For reference, both the Sun and the Moon, from the Earth's surface
are about 30 minutes of arc.)

	--Hal
-- 
Hal Heydt                    |    "Boycott Time-Warner"
Analyst, Pacific*Bell        |         --J. Danforth Quayle
510-823-5447                 |    "... kill all the lawyers."
whheydt@pbhya.PacBell.COM    |         --William Shakespeare
From: hughes@dogwood.botany.uga.edu (Wayne Hughes)
Newsgroups: rec.arts.sf.science
Subject: Re: Niven's blunders (was:Superconductors + the 2nd law)
Date: 1 Sep 92 22:58:28 GMT
Organization: Botany Department - U of Georgia, Athens

In article <Btx321.D95@helios.physics.utoronto.ca> neufeld@helios.physics.utoronto.ca (Christopher Neufeld) gives us more information about neutrinos: 
  
  Thanks, but I still have a couple of questions:

  [parts deleted]
>- One person in three on the Earth experienced a neutrino interaction
>event within their body due to the supernova.
>
>- A person shielded from all other supernova effects, at a distance from
>the explosion equal to the distance from our Sun to Jupiter, would be
>killed by the neutrino flux.
>
    Alright, so they derived a hypothetical flux in the latter hypothetical
    example from the measured (calculated from theory?) flux near the
    supernova.  How was the determination made that one person in three
    experienced an event?

    Here was my reasoning:


  I recall a physics canard:  a neutrino would have to pass through
  about 40 light-years of lead before it would have a 50% chance
  of interacting with a particle.  I guess this was a way of depicting
  the reality of a "ghost" particle. 

  Put another way, how many neutrinos (what would the flux have to be)
  would be required to pass through a human body before sufficient
  ionization or nuclear damage would occur to be fatal?  Is it reasonable
  to suppose that the dissipated wavefront from a core explosion
  3330,000 ly distant would be concentrated enough in neutrinos to
  effect that kind of damage?


>   No, that's not how it's likely to kill you. The neutrino can mediate
>some up <-> down quark interactions, or produce neutral current
>interactions, and both those will tend to result in highly energetic
>electrons whipping around in your body. This is a form of ionizing
>radiation, and gets you by the usual mechanisms. Induced radioactivity in
>the nuclei won't be as important. I don't know off-hand the relative
>cross-sections of the two mechanisms.

   This is where you get beyond my firm grasp of neutrino interactions.
   If the mechanism you describe does lead to ionizing radiation, and
   the flux is high enough to cause millions (billions?) of events,
   then I guess neutrinos from a core explosion would be damaging.


   Wayne
Newsgroups: rec.arts.sf.science
From: bcr@cernapo (Bill Riemers)
Subject: Re: Ringworlds
Organization: CERN, European Research Center for High Energy Physics
	<BtpK2v.Aus@ux1.cso.uiuc.edu> <BCR.92Aug28224728@hpl3sn02.cern.ch>
Date: Fri, 28 Aug 1992 22:01:43 GMT


In article <BtpK2v.Aus@ux1.cso.uiuc.edu> gletty@ux1.cso.uiuc.edu (Bruce Gletty) writes:

>
>  Both Ringworlds and Dyson Spheres still suffer from the instability problem. The
>  star has no force acting on it to keep it in the center of the system. I'm not
>  sure if there exists a solution for either, Niven kludged one up in Ringworld Engineers, 
>  but it seemed a little hokey. Its probably easier for a ring than a sphere.

This may be a stupid idea, but why not just take advantage of the solar wind?
As a side moves closer to the sun, that side covers a larger solid angle and
has an increased force pushing it back out.

                                             Bill
Newsgroups: rec.arts.sf.science,rec.arts.sf.written
From: abl@cybill.inesc.pt (Antonio Leal)
Subject: Re: Something Nasty in the Human Genome
Organization: INESC - Inst. Eng. Sistemas e Computadores, LISBOA. PORTUGAL.
Date: Wed, 2 Sep 1992 14:19:29 GMT

[Cross-posted to sf.written, for lit. search / book comments]

kelso_j@cs.uwa.oz.au (J Kyle Kelso) writes:
> [SF story idea]
>  I'd especially like to hear where else it occurs in SF literature.
>
>       The idea is this: all life forms in the galaxy have their genetic code
> "infected" by a kind of genetic parasite.  It's life cycle goes like:

David Zindell wrote a book called Neverness (publ. 1988), where the
"junk DNA" (i.e. apparently useless code) is a main point of the plot.
I think your approach is completely different from his.

I recommend Zindell's book, by the way.  It's one of the best SF books
of the last decade - superior to Simmons' Hyperion and Wolverton's On
My Way to Paradise. In these, the literary pretensions and logical
inconsistencies produce an annoying result.  Zindell manages to be
literate, and even poetic, without slipping into preciousness - and
the "technical" plot is interesting, albeit not flawless.

(By the way, has Zindell published anything else ?  All I've seen were
a story in Terry Carr's Universe 15 (1985) and Neverness in 1988.)

--
Antonio B. Leal		| IST / INESC
+351.1.310 0300		| R. Alves Redol 9, 1000 Lisboa
abl@inesc.pt		| Portugal
From: bcr@cernapo.cern.ch (Bill Riemers)
Newsgroups: rec.arts.sf.science
Subject: Re: Niven's blunders (was:Superconductors + the 2nd law)
Date: 1 Sep 92 20:45:50 GMT
	<1992Aug31.235032.5416@rigel.econ.uga.edu>
	<la7dp6INN787@appserv.Eng.Sun.COM>
Organization: CERN, European Research Center for High Energy Physics

In article <la7dp6INN787@appserv.Eng.Sun.COM> fiddler@concertina.Eng.Sun.COM (steve hix) writes:

>  If the flux is high enough, they are.
>
>  Apparently, if you're in a solar system whose star goes supernova (bad luck!),
>  the neutrino flux will cook you before any other evidence of the explosion
>  has time to get to you.
>
>  Sort of an extreme case, but...

I need to see some detailed calculations to swollow that one.  My god you have
to have a large enough flux to produce fission in a large fraction of your
ship and body mass...  Any sort of resonable distance from the star and the
inverse square law will save you.  Even in the heart of the star only a small
percentage of the total mass undergoes interactions.  (And this is very hot,
dense, and unstable matter.)  This hardly sounds like the description of
any sort of ship I want to be in.

                                  Bill
From: baylor@force.ssd.lmsc.lockheed.com
Newsgroups: rec.arts.sf.science
Subject: Re: Ringworlds
Date: 28 Aug 92 22:00:54 GMT
Reply-To: baylor@force.ssd.lmsc.lockheed.com
Organization: LMSC, Sunnyvale, California

In article <1992Aug28.181923.27698@unixg.ubc.ca>, holland@geop.ubc.ca (Stephen Holland) writes:
>>            Elf !!!
>There is a way to make a Dyson Sphere work with-out artificial gravity.  Just 
>spin the sphere.  That way you get Earth-normal (or whatever) gravity near the
>sphere's equator and a steadily decreasing gravity field as you move further away
>from the equator.  At the poles you have no gravity, which migh be useful for the
>ball-bearing industry.
>
When you spin a dyson sphere, it may as well be a ringworld. The gravity
and air will collect at the equator anyhow, and there's no way you'd
have enough air to fill a significant fraction of a 1AU diameter sphere.
Besides, given the vector of the centripetal acceleration, you'd have
very steep hills at a very short distance off the equator.

The only reason I can think of to close the ends, is for defense
(against space invaders, or maybe asteroids)
Newsgroups: rec.arts.sf.science