Message-ID: <QYKgwPy00UkZIkwE5M@andrew.cmu.edu>
Reply-To: space+@Andrew.CMU.EDU
From: space-request+@Andrew.CMU.EDU
To: space+@Andrew.CMU.EDU
Date: Sun, 30 Apr 89 05:17:16 -0400 (EDT)
Subject: SPACE Digest V9 #401

SPACE Digest                                      Volume 9 : Issue 401

Today's Topics:
		       Re: Shuttle Acceleration
		      Re: railguns and asteroids
      Censorship ( was Space Shuttle Attacked by 200-foot UFO!)
		Re: Stirling engines & fusion, rev. 2
		B E M (was Space Shuttle Attacked ...)
		Re: Proposed luner simulation facility
	     Re: US citizen - ET contact legal penalties
			  Re: Smart Pebbles
			  Re: Smart Pebbles
----------------------------------------------------------------------

Date: 26 Apr 89 21:00:53 GMT
From: hpfcdc!bayes@hplabs.hp.com  (Scott Bayes)
Subject: Re: Shuttle Acceleration

> 	Less time fighting gravity? I can't see what time has to do with it.
> If you disregard friction momentarily (read as non-conservative forces), 
> then you simply must supply an energy to the shuttle of (Potential + 
> Kenetic)=(mgh + .5mv**2); this has nothing to do with how fast the shuttle 
> accelerates.
> 
> -------------
> John Taylor -- SUNY at Buffalo
> Bitnet  : v131q5cg@ubvmsc
> Internet: v131q5cg@ubvmsc.cc.buffalo.edu

For this one, I like analysis at the boundary condition. The one of interest
here is: burn enough fuel/time to accelerate at 9.8 m/sec in free fall. This
is the power needed to exactly balance the Earth's gravitation. Do that till
your fuel is all burned up. How far have you gone? Nowhere, as you used all
the fuel hovering stock still above the launch pad. Double the power output;
you burn the fuel in half the time (assuming linear function), but accelerate
at 1G of the Earth's surface during that time, giving you a net velocity, and
a net distance travelled at burnout.

I believe the discussion only applies in a significant gravity well, but
haven't looked to see how it applies where external fields (gravity wells)
are close to 0 relative to available acceleration. It's probably true that
delta-vee is proportional to 

integral over t over d of (A-a(d))

where A is the (constant) thrust acceleration available to the ship, t is the
time over which A is applied, d is distance from the gravity source, and a(d) 
is the gravitational acceleration value, which varies in the gravity well.

Scott Bayes

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

Date: Thu, 27 Apr 89 19:51 CST
From: Shallow thoughts for shallow minds <SCOTT%GACVAX1.BITNET@VMA.CC.CMU.EDU>
Subject: Re: railguns and asteroids

article 1:
} ELIOT@cs.umass.EDU writes:
}
}>   Would it be reasonable to use Rail-Guns in mining an asteroid.
                ----- stuff deleted (how to get it to earth -----
}Hopefully the asteroid you're mining is still sufficiently massive by the time
}you're finished that you don't alter its orbit too much with all this momentum
}you're transferring... :-)
}
}I would think it would be very expensive to recover metals from a high-
}velocity impact crater on the Moon, when you could simply build another
}mass driver in lunar orbit to receive the incoming load, at the same time
}generating a fair amount of electrical power.  Of course, you'd have to have
}either *very* good aim or a very wide mouth on your driver.
}
}Peter Scott (pjs@grouch.jpl.nasa.gov)
}

article 2:

]In biar!trebor@cu-arpa.cs.cornell.edu  (Robert J Woodhead) writes:
]
]> In article <8904122007.AA10396@crash.cs.umass.edu> ELIOT@cs.umass.edu writes:
]> >    Would it be reasonable to use Rail-Guns in mining an asteroid.
]>
]> Given that for each reaction there is an equal and opposite reaction, it
]> would make more sense to use the Railgun as a thruster; by ejecting a few
]> percent of the mass of the asteroid at high velocity, one could move the
]> asteroid to the vicinity of earth, where it would be convenient to mine.
]The problem with moving asteroids around rather than returning mass to
]Earth via rail-gun pellets is that the amount of time it takes to
]move an asteroid makes it much less economic given interest costs
]of capital equipment.  This is a factor which none of the asteroid
]advocates have taken into account in their comparisons with lunar
]resources.
]
]Even though delta-v to many asteroids may be lower than access to
]lunar material, round-trip time for the equipment ends up dominating
]the cost optimization.
]
]Therefore, using a rail-gun, mass-driver or any other high-speed
]delivery mechanism for asteroidal material IS the best use of
]those technologies rather than moving the asteroids to Earth.
]
]In any case, if someone decided to begin moving an asteroid toward
]Earth so they could mine it, I think I would take it upon myself
]to preemptively assasinate them.

]Jim Bowery    Phone: 619/295-8868

Really, now, I see absolutely no problems with moving the astroid to earth
:-)

A really neat way to do it would be to basically set up an ore processing
plant on the astroid. Then, depleted ore could be thrown away (via a railgun,
even though I cant see how, or a catapult, or something) to give thrust
towards your objective (earth). With your cold fusion generator, you could
probably build up a pretty decent thrust. Heck, just to be safe youll want
to pulverize your waste into dust, and then you can use ion drives. You
wont get the astroid here very soon (probably on the order of a year or
so), but by the time its here, itll basically be a hunk of processed metal.
Since itll be so big, and moving relatively slow, it probably wouldn't be
as hard to aim for the mouth of your linear accelerator, either. Or just
ditch it on the moon. But why? cant you send it into an orbit around the
moon? maybe a sweep around the earth to slow it down? itd be easier to pick
it up from orbit than to try to catch it, and if you put it in a stable
orbit, itll still be there later, while if you dont have anything there
to catch it when you should, your out of luck, 'cause itll breeze on through
the earth-moon system (hopefully).

Also, if you just cannot wait for your processed metal to get here, you
could build ion drive on one end of the astroid, and a railgun on the other.
shoot processed ore home, and waste behind.

The biggest problem I can really see is keeping your load balanced. As you
mine the atroid, its center of mass probably will change, and you engines
and accelerators all have to be set up correctly, else your astroid will
start tumbling. Then youd have a problem picking it up.

scott hess

Scott@gacvax1.bitnet

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

Date: 27 Apr 89 20:51:44 GMT
From: genrad!dls@eddie.mit.edu  (Diana L. Syriac)
Subject: Censorship ( was Space Shuttle Attacked by 200-foot UFO!)

You would think that sci.space and sci.space.shuttle would be two
of the more liberal groups on the net, considering most of the
people who read it (or at least post to it) seem to be in the 
professional or technical fields.  'Twould seem this is not the
case, since some of them have blinders on as large as any of the
horses I've heard about in years past.  For those of you who don't
live in the "Land of Freedom", where men (and women) are allowed
to express their opinion on ANY subject, so long as it doesn't 
hurt anyone, please remember that a large portion of those who
read this don't condone their censorship.

UFOs are definitely pertinent to Space....last I heard, most of 
them are from OUTER SPACE.  Space shuttle news is also pertinent
to Space.  Whether these articles are simply a hoax or rumor or
whether they are factual is STILL undetermined.  Quite frankly
I enjoy this cheerful subject as a change of pace from some of
the critical articles which have been so prevalent of late.

Please continue to post these articles HERE where those of us
who are interested can follow the amusing tale.

I'm sure this will generate many more critical articles.  All I
can say is, I keep the "bit bucket" next to my desk.

From one of the silent majority

->	    Diana L. Syriac						    <-
->USmail:   GenRad Inc., Mail Stop 6, 300 Baker Ave, Concord, Mass.  01742  <-
->usenet:   {decvax,linus,mit-eddie,masscomp}!dls@genrad.com                <-
->tel:	    (508) 369-4400 x2459	I'D RATHER BE FLYING!!!		    <-

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

Date: 27 Apr 89 13:36:26 GMT
From: xanadu!michael@apple.com  (Michael McClary)
Subject: Re: Stirling engines & fusion, rev. 2

In article <1989Apr25.132913.1300@mntgfx.mentor.com>
mbutts@mntgfx.mentor.com (Mike Butts @ APD x1302) describes
stirling engines of the crankshaft kind.  There is another
that is interesting:

This sort has a fixed cylinder, a displacer piston mounted
to the power piston by a spring, a strong magnet mounted
on the power piston, and coils mounted on the cylinder.
The mass of the displacer piston and the spring tying
it to the power piston form a simple harmonic oscilator,
and at its resonant frequency the displacer lags the power
piston by 90 degrees.

Once you apply a temperature difference, initial small vibrations
at the resonant frequency become amplified by the engine, making
it self-starting.  The magnet and coil form an alternator, and
power is efficiently extracted as electricity.

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

Date: Thu, 27 Apr 89 18:35:10 CDT
From: pyron@lvvax1.csc.ti.com (c, it's not just a good idea, it's the law)
Subject: B E M (was Space Shuttle Attacked ...)

haven!vrdxhq!daitc!ida.org!roskos@purdue.edu  (Eric Roskos) reports:

>Well, I scoffed when I read the recent postings in rec.ham-radio about the
>UFO, but then I was standing in the check-out line at Giant (world's
>slowest cashiers) and saw the following headline on "Weekly World News":

     important stuff deleted, but you get the drift
>London's respected Daily Star newspaper, which has a circulation of 1.3
>million, broke the story that included sensational testimony from a
 
If you think that's sensational, check out page two (sexist comment)

>But he told The NEWS in a telephone interview that he has commissioned a
>sophisticated voice-print analysis to determine if it really is the
>shuttle telling mission control: "Houston, this is Discovery.  We still
>have the alien spacecraft under observation."

But maybe they had never seen a Blackbird from that angle.  :-)

>The Daily Star rocked Europe by additionally reporting that a *ham radio
>operator* claims to have heard a shuttle astronaut say: "Houston, we
>have a `fire'" -- which is widely believed to be a NASA [term] for a
>UFO. 

And "Houston, we have a 'UFO'" means they're using the extinguishers?


Those reports, while sensational, paled before yet another allegation
from Dr.  Marcel Ponte.  In Paris, the founder and president of the
watchdog group, UFO Truth, said he can prove that space aliens boarded
the shuttle and inspected its cargo....  He also claimed to have heard
an alleged conversation between the shuttle and mission control that
says:

"Houston, this is Discovery.  We have alien spacecraft.  200 feet.  Blue.
Cargo hold.  Controls useless.  A pair.  Bug eyed.  We are invaded."

The brief transmission was allegedly made when the Discovery was in the
20th hour of its five-day mission. 

[End of excerpt.]

>The article also includes an "artist's conception of chilling encounter
>in space," depicting an object resembling a plumber's helper with a disc
>brake rotor attached to the bottom of it, pointing a long, antenna-like
>object at the shuttle, which has its cargo door open and and astronaut
>precariously perched on the back, near the tail fin, as if he is about
>to fall backward with surprise.  He appears to be holding a suitcase. 
 
Someone appears to be reading too much Vonegut.

>Editors: I am 14 years old and have never been to America, but I can see
  and so on...
This last one frightens me.  When my sister's pen pal came to visit a few
years ago, he was surprised that no one was wearing a gun!  And he was
supposedly educated (product of UK, can anyone there tell me who has the
worse school system?).  From this kind of thinking, we (Mercans) are preceived
as some sort of wild yet facist country, where hundreds die in our very
capital (oops).  But I digress.
-- 
>Eric Roskos (roskos@CS.IDA.ORG or Roskos@DOCKMASTER.ARPA)

Thank you Eric, I've worked way late, still have too much to do, but this
article has done something for my day.

Dillon Pyron                         | When my opinions match my employer's
TI/DSEG Lewisville Computer Services | I will be self employed.
pyron@lvvax1.csc.ti.com              |
(214)462-5449                        | If you think you're better than your
                                     | congressperson, run against him/her

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

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

Date:       Fri, 28 Apr 89 08:43:30 BST
From: ZZASSGL@CMS.MANCHESTER-COMPUTING-CENTRE.AC.UK
Myname:     Geoff. Lane. (Phone UK-061 275 6051)
Subject:    Re: Proposed luner simulation facility


Would it not be cheaper just to go to the Moon?

Geoff.

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

Date: 27 Apr 89 17:47:29 GMT
From: sco!natei@uunet.uu.net  (Nathaniel Ingersoll)
Subject: Re: US citizen - ET contact legal penalties

In article <Added.0YJ8MDy00Ui3M_6083@andrew.cmu.edu> wmartin@ST-LOUIS-EMH2.ARMY.MIL (Will Martin -- AMXAL-RI) writes:
:Hi, all!

[ quote from NASA legal stuff about policing the earth ]
:
:(a) NASA policy, responsibility and authority to guard the Earth against
:any harmful contamination or adverse changes in its environment resulting
:from personnel, spacecraft and other property returning to the Earth
:         [Note -- my emphasis here ----->  ]  ^^^^^^^^^^^^^^^^^^^^^^
:after landing on or coming within the atmospheric envelope of a
:celestial body; and

I find this interesting - they're only concerned about things that are
"returning" to the Earth; therefore someone (something?) comes from somewhere
else and is not "returning", it's out of their legal scope!

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

Date: 28 Apr 89 19:11:08 GMT
From: rochester!yamauchi@cu-arpa.cs.cornell.edu  (Brian Yamauchi)
Subject: Re: Smart Pebbles

In article <3761@aplcomm.jhuapl.edu> jwm@aplvax.jhuapl.edu (Jim Meritt) writes:
>
>See the film footage of the test of the smart pebble?
>
>That looked _NEAT_!!!!!  That thing sitting there bursting its jets holding
>a hover was slick!!!  

Yeah, it looked really neat.  Just one question: What's the difference
between the smart pebble concept and placing smart interceptor
missiles in orbit?

Is this anything like the Thor idea (ala Footfall)?  (Use rockets for aiming,
but rely on gravity for acceleration.)

>(hear the crowd in the background?)

I think enthusiastic would be an understatement :-).
_______________________________________________________________________________

Brian Yamauchi				University of Rochester
yamauchi@cs.rochester.edu		Computer Science Department
_______________________________________________________________________________

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

Date: 28 Apr 89 21:16:02 GMT
From: greg@june.cs.washington.edu  (Greg Barnes)
Subject: Re: Smart Pebbles

In article <3761@aplcomm.jhuapl.edu> jwm@aplvax.jhuapl.edu (Jim Meritt) writes:
>See the film footage of the test of the smart pebble?

I thought they were known as 'brilliant' pebbles.

My question:  Do these things have something to do with the 'thousand
points of light' we've been promised?

Followups to talk.rumors.

					Greg Barnes
					greg@cs.washington.edu
------------------------------------------------
April 27:  In the first test of the $512 billion Star Wars on Drugs program, 
an orbiting laser-equipped satellite successfully vaporizes three city blocks
believed to contain a suspected drug pusher.
			--- Dave Barry's "1988 in Review"

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

End of SPACE Digest V9 #401
*******************