HDTenEightyP/NetNews huggingface dataset:
From: sdr57@cas.org ()
Subject: Re: Laser weapons
Organization: Chemical Abstracts Service, Columbus, Ohio
Date: Thu, 3 Sep 1992 13:51:25 GMT

In article <rwallace.715515667@unix1.tcd.ie> rwallace@unix1.tcd.ie (russell wallace) writes:
>
>Not really; to raise the temperature of 1 litre of water (the main
>constituent of the human body) by 10 degrees K (hardly enough to kill
>someone), takes 42,000 joules of energy. The target is not going to
>stand still long enough to let you pump that amount of energy into him.
>And if laser weapons are in common use, he will probably be wearing
>Kevlar with ceramic inset plates, which will be *very* difficult to burn
>through (in fact, I would say that no laser we can built *at all*, never
>mind as a hand weapon, could burn a hole through ceramic and person in
>the fraction of a second of time available).
>
Lasers used as antipersonnel weapons would not need to burn through
someone to kill or disable. By vaporizing a relatively small amount
of material by rapidly heating a restricted region, you produce what
is in effect a localized explosion (solid-vapor transitions involve
large volume changes) which can be quite damaging - this is a problem
when attempting to use lasers for precise fabrication of
water-containing materials. Use of lasers in the military role to
blind airmen was the subject of complaints by the US to the former USSR
on several occasions.

>Good point: if the weapon produces a plasma flame, this is not going to
>be an effective weapon at significant range in atmosphere (or indeed at
>all). You really want it to generate a beam of light/infrared/X-rays or
>whatever. Can any engineer types out there comment on whether this is
>even theoretically possible?
>
>Hardly quick and easy; they still haven't managed to even prove that the
>X-ray laser is possible, never mind actually build a working prototype.
>And the visible light chemical laser doesn't put out enough power to be
>of any use.
>
Er... X-ray lasers have been made - I suggest you check out Phys.
Fluids B 4(7 part 2) beginning on page 2326 for a review of this work.

As for the comment on the power of "the" visible light chemical laser,
exactly which visible light chemical laser do you mean by "the"?
You might be surprised at the power densities which chemical lasers
can obtain.
>>--
>> 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" |
>--
>"To summarize the summary of the summary: people are a problem"
>Russell Wallace, Trinity College, Dublin
>rwallace@unix1.tcd.ie
******************************************************************************
Renegade academician. They're a dangerous breed when they go feral,
academics are...a chemist, too.
		    -(James P. Blaylock in "Lord Kelvin's Machine")

My organization hasn't agreed with any of my opinions so far, and
I doubt they'll start now.

Stanley "Ya nee speon" Roberts

Newsgroups: rec.arts.sf.science
From: stoodt@cis.umassd.edu (Michael Stoodt)
Subject: Re: Ringworlds
Organization: University of Massachusetts Dartmouth
Date: Sat, 29 Aug 1992 20:13:04 GMT

In <1992Aug29.061737.16642@nwnexus.WA.COM> elf@halcyon.com (Elf Sternberg) writes:

> ...  Niven's system works,
>but one thing that always bothered me: Niven had TWO systems for
>manipulating the relationship between the sun and the ring.  One was
>the attitude jets around the rim of the ringworld.  This was the ONLY
>system he had for his world that didn't destroy 20% of the ring.  These
>jets would collect solar energy and distribute it in an impulsive
>fashion, pushing the ring back to center.

>   The other method used the ring as a giant magnet to create a HUGE
>solar flare to knock the ring back into position.  This method always
>bothered me for several reasons, not the least of which was it would
>KILL 20% of the ring population.  If the 'knock' was powerful enough to
>push the ring back where the jets weren't, why did the jets have to
>power to stop the ring from sliding in the _other_ direction?  It also
>seemed to that the HUGE (approx 200,000km) electricity networks he had
>buried in the ring were more than adequate to generate _gentle_ EM
>fields that, fired in a computer-controlled sequence, like the attitude
>jets, would, with the magnetic field of the sun, be more than
>sufficient to keep the ring in place.  This method has less moving
>parts too!

(Attempting to minimize spoilers:)

Under the assumptions that the designers of the Ringworld made, the
attitude jets would work just fine off the solar wind, and one would
never need to use the flare system to super-charge them.  (The flare
system is a defense to destroy incoming rocks or spaceships (if they
weren't the designers' ships, they were by definition enemies).)  But
the designers never expected to have 90%+ of their attitude jets
ripped off by another culture for use as interstellar ramjets (the
designers never expected to not be around, and never expected there to
be sentients on the Ringworld who didn't intuitively understand the
need for the attitude jets), so that by the time of _Ringworld
Engineers_, the only option was to combine the two systems (more jets
applied earlier would have kept the situation under control), killing
a large fraction of the Ringworld's population to save the rest.
-- 
Michael A Stoodt  [MaS]                       stoodt@cis.umassd.edu
"Will the last person to leave the planet please turn off the sun?"
                                                     - Mike Resnick
From: max@west.darkside.com (Erik Max Francis)
Newsgroups: rec.arts.sf.science
Subject: Re: Niven's blunders (was:Superconductors + the 2nd law)
Date: 29 Aug 92 19:05:32 GMT
Organization: The Dark Side of the Moon +1 408 245 SPAM

wiml@milton.u.washington.edu (William Lewis) writes:

> >Rinworld stability (well, that's a classic; has anyone figured wether he
> >got it right the second time round?)
> 
>   What is there to get wrong? He had an active control system (the
> ramjets). Unless one could calculate that the ramjets wouldn't have enough
> thrust, or something, but I think ramjets are too theoretical
> to do that.

In _Ringworld,_ there was no mention of the Ringworld ramjets.  Ringworld 
is unstable in the plane of its orbit.  Thus after the slightest 
perturbation, there is no restoring force, and the Ringworld would 
eventually touch the shadow squares.

So in _The Ringworld Engineers,_ he had to cover his mistake, describe 
the attitude jet system, and then give an explanation of why it hadn't 
been seen . . .

As far as fulfilling those criteria, I thought he did a fairly good job.

> >Rotation in Neutron Star will kill Schaeffer (he owned up to that one
> >himself).
> 
>   I've only ever heard vague hints about this one, never anything actually
> explainingthe problem. What's the catch?

My understanding is that tides will kill him no matter what.  (He admits 
this in another book:  "Alas and dammit, Shaeffer can't survive."  After 
all, the ship comes within _one mile_ of the surface of the neutron star. 
That's going to be a hell of a gravity gradient between his head and his 
feet.

It is interesting how some astrogators in the future don't understand the 
simplest astrophysical problems . . . :-)  Of course, it's all for the 
sake of a story.

----------
Erik Max Francis   Omnia quia sunt, lumina sunt.  Coming soon:  UNIVERSE _ | _
USmail:  1070 Oakmont Dr. #1 San Jose CA 95117  ICBM:  37 20 N  121 53 W _>|<_
UUCP:  ..!apple!uuwest!max   Usenet:  max@west.darkside.com   464E4F5244   |
Newsgroups: rec.arts.sf.science
Subject: Re: Laser weapons
From: ecmtwhk@ccu1.aukuni.ac.nz (Thomas Koenig)
Date: Wed, 2 Sep 1992 11:26:09 GMT
Organization: University of Auckland, New Zealand.

markrose@spss.com (Mark Rosenfelder) writes:

>I'd like to throw some laser weapons into an sf story, but I find I don't
>know enough about lasers.  

>Naturally, we're not talking about those wimpy supermarket lasers here--
>we want some lasers that can fry people.

>Some questions:
>Are these things even practical as hand weapons?  

In principle, yes. You probably would like to make them give off their
energy in pulses, otherwise the hand movement of the weapon user and
the target's own movement would make things too unsure. You could make
them fire pulses rather frequently, however, like a machine gun.

>How much energy do they use?

Depending on the level of technology, it might be too much to carry
around. The energy required to do significant damage is quite high. If
you restrict yourself to chemical charges (battery or fuel), think of
what the same amount of fuel could do if it was ignited directly on your
hand.

>Do they make a noise when fired?
>Does the frequency matter?  I.e., would it make more sense to generate
>  ultraviolet or gamma rays rather than visible light?

Lasers with longer wavelengths will spread more. As a rough estimate,
you can say that the angle of spread (in radians) will be the aperture
divided by the wavelength. Absorbtion characteristics of the target and
the air will also play an important role. Visible light has the
disadvantage that people will be able to see where the shot comes from,
by observing the reflections on dust particles in the air.

X-ray lasers have rather nasty effects, because of ionization. They will
tend to kill people over months, from radiation sickness, rather than
immediately, unless you put in prodigous amounts of energy. That might
not be the best idea if someone is coming at you with a knife, for
example.
-- 
Thomas Koenig, ecmtwhk@ccu1.aukuni.ac.nz, ib09@rz.uni-karlsruhe.de
The joy of engineering is to find a straight line on a double logarithmic
diagram.
From: pepke@ds1.scri.fsu.edu (Eric Pepke)
Newsgroups: rec.arts.sf.science
Subject: Re: Donaldson's _Gap Cycle_: does this add up?
Date: 27 Aug 92 05:10:53 GMT
Reply-To: pepke@ds1.scri.fsu.edu (Eric Pepke)
Organization: Florida State University, but I don't speak for them

In article <1992Aug26.191013.9965@news2.cis.umn.edu> alberti@mudhoney.micro.umn.edu (Albatross) writes:
>My second question is simpler:  in several places in the novels ships
>accelerate to significant portions of c.  They do so with levels of
>acceleration which approach human tolerances for durations of between four and
>about ten hours.  I suppose based on these descriptions one might expect
>these accelerations to be between 3 and 8 G (?)

From my high school physics class, I seem to remember that relativistic 
momentum is p = gamma m0 v, where gamma is 1/(sqrt(1 - (v^2/c^2))), m0 is the 
rest mass, v is the velocity, and c is the speed of light.  The total delta v 
you need starting from relative rest is gamma v.  Using the MKS system, to get 
to v = 50% of c, you need a delta v of about 1.7e8 m/s.  G is about 10 m/s^2.  
Assume the thrust is 10G, that's 100 m/s^2.  To get this amount of delta v 
you would need to run the engines for 1.7e6 seconds, or about 20 days.

-EMP
From: fiddler@concertina.Eng.Sun.COM (steve hix)
Newsgroups: rec.arts.sf.science
Subject: Re: Niven's blunders (was:Superconductors + the 2nd law)
Date: 31 Aug 1992 20:32:37 GMT
Organization: Sun Microsystems, Mt. View, Ca.
NNTP-Posting-Host: concertina

In article <8-ty74#@rpi.edu> kasprj@rpi.edu writes:
[ re: the quick pass in Neutron Star ]
> Actually it's not the instant of tidal stress that will get him - that 
>comes and goes so quickly that he can ride out the moments of extreme 
>gravitational gradients if his center of mass is at the ship's center of
>mass when he reaches the closest point. I'd think that Niven would have
>done the homework on this one (though I'll admit I haven't checked it 
>myself). 
> 
> The problem is that, once the ship leaves the vicinity of the neutron
>star, it's got all that angular momentum impatred to it by the torque 
>of being swung around perpendicular to the neutron star's surface. There's
>no way to get rid of that angular momentum quickly, so Shaeffer still has
>the problem of being flung towards one end or the other of his ship (though,

He was passing the NS with a close hyperbolic orbit, right?

As he approaches periastron, keeping the long axis of the ship aligned with
the center of the ns increased the spin perpendicular to the long axis.

After periastron, maintaining that alignment would mean that his ship would
have been just as quickly decellerated to stay aligned.

How much spin would be left after leaving the system?  Surely not all (or
even most of the spin at periastron).



--
-----------------------------------------------------------------------
Of making many books there is no end...  |  What's wrong with chasing 
                       -- Eccl. 12:12    |  nebulae till 3 am?  |-(
-----------------------------------------------------------------------
From: f3w@mentor.cc.purdue.edu (Mark Gellis)
Newsgroups: rec.arts.sf.science
Subject: Re: Laser weapons
Date: 4 Sep 92 00:59:35 GMT
Organization: Purdue University Computing Center

I would argue that guns will not be replaced, although they will be
improved, and the average infantryman/hired killer may use other weapons
that do what gunpowder weapons do now.

Guns make knives "obsolete," after all, but look how many people still 
get killed with knives.

We will probably move to caseless ammunition in the future (lighter, so
more can be carried).  Better targeting systems for the weapon, perhaps
including things like a glove-and-lens smartgun--you wear part of your
targeting system like a contact lens (or have it implanted in your eye)
and its microprocessor/controller sends signals to a glove that gives
you tactile feedback until you're aiming precisely at what you're already
looking at.

Smart bullets would be nice, too.  Tiny, tiny TV cameras and processors
in the bullet and tiny fins on the bullet, too.  We already have a howitzer
shell like this called the Copperhead; now, it's a matter of making small
ones that are really cheap.
Newsgroups: rec.arts.sf.science
From: singley@helix.nih.gov (Erick D. Singley)
Subject: Re: Niven's blunders (was: Superconductors + the 2nd law)
Organization: (National Institutes of Health, Bethesda, MD)
Date: Tue, 1 Sep 1992 15:16:18 GMT

>Um... if I recall correctly (and it has been a couple of years since I've read
>all the Niven books...), wasn't the "radiation" from the core explosion in the
>form of nutrinos or something like that?  Nutrinos have a nasty habit of being
>able to pass through planets and rocks without slowing down, so underground
>cities would not help at all.

Well, that doesn't match up right. First, Radiation is "the process in which
particle or wave energy is emitted or transmitted through matter or space."
All well and good. Nutrinos do indeed have this 'nasty habit of being
able to pass through planets and rocks without slowing down' and are some
form of energy or matter. However, this is *precisely* the characteristic
that would make it not as much a danger.  Damage from radiation occurs from
COLLISIONS with matter (ie- your cells/cell componets [ie protiens/DNA], etc)
An alpha particle is a big (Atomic mass of 4) thing that has a relatively low
energy.  But their size makes it easier to collide with something. Therefore
easy to shield against, but more dangerous since all collisions would be at the 
surface (skin, eyes) and -concentrated-.  Beta particles have a lower mass
(1/2000 amu) but higher energy [p32 get get up to 1.710 MeV - this would be able
to penatrate skin a little].  

Then we get to higher energy stuff, with little to no mass (Gamma/Xray, photon)
One does indeed need lots of shielding (bu-coo inches of lead- or other dense
stuff) to stop this.  For a person- fewer collisions (go farther through body before a collision) but more energy to do damage.

So, for a particle with NO mass (we have yet to see any really good evidence
in those big underground tanks) there would need to be some amazingly dense
rainstorm of these things (ie really lotso neutrinos/ unit area) just to even
make it a danger. and even then assume sufficent energy can be put in these
particles.

Erick

Numbers from NIH "Radiation Safety for Authorized Users"
Xref: sparky rec.arts.sf.science:2813 rec.arts.sf.written:11744
From: smith@ctron.com (Larry Smith)
Newsgroups: rec.arts.sf.science,rec.arts.sf.written
Subject: Re: Something Nasty in the Human Genome
Date: 4 Sep 92 16:52:22 GMT
Reply-To: smith@ctron.com
Followup-To: rec.arts.sf.science
Organization: Cabletron Systems, Inc.

In article <FRANCIS.92Sep3093653@galois.dogwood.atl.ga.us>, francis@dogwood.atl.ga.us (John Stracke) writes:
>In article <1992Sep3.031844.21399@news.eng.convex.com> cash@convex.com (Peter Cash) writes:

>>Kind of intriguing...makes me think that information is encoded in the DNA
>>in ways other than the direct code we know about. Hmmm...how about a
>>fractal data compression algorithm? Maybe it's a picture of God?
>>Directions for the next step in evolution? The Cosmic Self-Destruct
>>Command? Guess I'm in one of those moods...

>No, no.  It says, "If you can read this, you're too close." :-)

If you're a deist, it could be a signature. :)

Mostly likely it is leftover DNA sequences from old genomes.  Bits of old
dinosaur DNA, and so forth.  Not complete, mind you, but those portions that
were not used when various other sequences mutated into new species.  It may
be that extinct species could be reconstructed from bits of that DNA taken
from many living descendents of the target species.  Bit of human - bit of
canary - just a taste of kangaroo and a hint of platypus and VIOLA!  Instant
allosaurus.

Someone also wrote a story about some survivors of an alien crash landing,
who encoded a message to their descendents in such DNA.  What the text of
such a message might be is anyone's guess.

Larry Smith (smith@ctron.com)  No, I don't speak for Cabletron.  Need you ask?
-
How about we all do something reasonable?  I bet that'll confuse 'em!
From: bjgaed@bb1t.monsanto.com
Newsgroups: rec.arts.sf.science
Subject: Re: Hydro energy storage systems
Date: 27 Aug 92 06:39:13 CST
Organization: Monsanto Company, St. Louis, MO

In article <pjh.714824425@nessi>, pjh@eng.cam.ac.uk (Philippa Hogben) writes:
> 
> The point, in this case, is not whether you can actually whether you
> can get back exactly the same amount of energy as you put in. The idea
> of pumped storage systems is to keep the "base load" power stations
> running at their optimum output during the slack period and to provide
> a supply for the peaks without the cost of building extra coal, gas or
> nuclear power stations.
> 
> Philippa

And more to the point, is this a good idea?  Obviously it's a good 
idea for the power companies.  They get to sell more electricity 
without more investment in capacity.  While this is clearly an 
economic advantage, I don't think it is advantageous from the 
standpoint of overall efficiency, conservation of resources, 
environmental impact, etc.

Now, I'm only guessing at these numbers, but if the thermal efficiency 
of the original generating system is 35%, and the in-out efficiency of 
the pumped storage system is 60%, as someone suggested, and we lose 
10% of the electricity each direction from transmission losses, we 
have an overall efficiency of .35 * .90 * .60 * .90 = 17% of the 
energy finally reaching the consumer.  

Now, unless we all decide to have mini-fast-breeder reactors in our 
basements to heat our homes in the future there will always be 
generation and distribution losses, but can't we come up with a better 
system than pumped-storage?  What's the most efficient 
electricity-storage system?  Water electrolysis/hydrogen & oxygen 
storage/fuel cells?  

Or should we junk the idea of large-scale energy storage entirely as 
just too inefficient?

My original point was that these projects are possibly the right idea 
but at the wrong time.  Conservation and efficiency are a better 
investment right now for an industrial society like the U.S., IMO.  It 
may not be the best investment for a utility company, but here again 
we make a mistake if we treat a utility company as a closed system.  
It is an open system with fuel and capital inputs from the larger 
society and waste outputs.  Our vision of the future seems to depend 
on just how much entropy the planet can absorb.

--Electric Monk            (Bruce Gaede); 
                            e-mail: bjgaed@ccmail.monsanto.com

"...and then time started seriously to pass."
--Douglas Adams, _Dirk Gently's Holistic Detective Agency_
Newsgroups: rec.arts.sf.science
From: pjh@eng.cam.ac.uk (Philippa Hogben)
Newsgroups: rec.arts.sf.science
Subject: Re: Hydro energy storage systems
Date: 26 Aug 92 10:20:25 GMT
Organization: cam.eng

alanb@sdl.mdcbbs.com (Alan Braggins) writes:

>>>>>> On 24 Aug 92 07:29:08 CST, bjgaed@bb1t.monsanto.com said:

>> In article <78243@ut-emx.uucp>, dillard@ccwf.cc.utexas.edu (Alex Dillard) writes:
>>> In article <hl71572@pro-smof.cts.com> wixer!cactus.org!wixer!pro-smof.cts.com!rfletcher@cactus.org (Robert Fletcher) writes:
>>> 
>>>    Under ideal conditions (no friction, perfect motors(no energy lost in 
>>> turning electricity into motion), no flow irregularaties(turbulence) in the
>>> water, etc.) it would be possible to lose no energy in this process. That is,
>>> you could get back out the energy put in to pump the water uphill.

>> Think about it.  If you *could* get out as much energy from the water 
>> coming back downhill you could use that energy to pump the water back 
>> uphill, right?  And, class, what do we call this perfect machine?
>> Right! A *Perpetual Motion Machine.*


The point, in this case, is not whether you can actually whether you
can get back exactly the same amount of energy as you put in. The idea
of pumped storage systems is to keep the "base load" power stations
running at their optimum output during the slack period and to provide
a supply for the peaks without the cost of building extra coal, gas or
nuclear power stations.

Philippa


--
Philippa Hogben   pjh@eng.cam.ac.uk  (Reverse if mailing from Janet)
Any mistakes are mine, all mnie.

I am not a .sig virus. I am a free bug. 
Newsgroups: rec.arts.sf.science
From: nickh@CS.CMU.EDU (Nick Haines)
Subject: Re: Laser weapons
Originator: nickh@VOILA.VENARI.CS.CMU.EDU
Organization: School of Computer Science, Carnegie Mellon University
Date: Thu, 3 Sep 1992 22:56:48 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?

Sure. Smarter guns. Aimed by AIs with fast servos, nanotech gray-goo
(or Blood-Music style `smart bugs') projectiles that don't just blast
a hole in the target but turn it into a refrigerator (/a
space-yacht/another gun) instead, micronukes (using, hmm, ideas from
cold fusion, read sci.physics.fusion for the latest genuinely
interesting results there).

For bigger weapons, how about _big_ orbiting lasers, or kinetic energy
weapons (Harsh Mistress), or nanotech (again), or wormholes.

Nick