home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
Space & Astronomy
/
Space and Astronomy (October 1993).iso
/
pc
/
text
/
spacedig
/
v16_1
/
v16no110.txt
< prev
next >
Wrap
Internet Message Format
|
1993-07-13
|
10KB
Date: Tue, 2 Feb 93 05:19:34
From: Space Digest maintainer <digests@isu.isunet.edu>
Reply-To: Space-request@isu.isunet.edu
Subject: Space Digest V16 #110
To: Space Digest Readers
Precedence: bulk
Space Digest Tue, 2 Feb 93 Volume 16 : Issue 110
Today's Topics:
Beanstalk?
Help on catching this
Posting Anonymously
Well..
Welcome to the Space Digest!! Please send your messages to
"space@isu.isunet.edu", 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 space-REQUEST@isu.isunet.edu (Internet).
----------------------------------------------------------------------
Date: 2 Feb 93 00:08:58 GMT
From: kjenks@gothamcity.jsc.nasa.gov
Subject: Beanstalk?
Newsgroups: sci.space
nsmca@acad3.alaska.edu wrote:
: Does anyone know anythng about how to build a beanstalk?
Magic beans aside, both Charles Scheffield and Arthur C. Clarke wrote
excellent hard SF novels about how to build an Earth-to-geosynchronous-
orbit "beanstalk" -- at the same time!
The books were published almost simultaneously, and although
Sheffield's book, Web Between Worlds (which came out JUST after
Clarke's Fountains of Paradise) was obviously not plagerized, they had
some uncanny similarities. Both were about the project of building the
device, both had similar "magic" (by Clarke's definition) structural
materials, and both had Merlin-like protagonists.
Sheffield had a hair-raising method of anchoring the structure, which
was built in orbit then had one end lowered to the Earth. Clarke had
to "move" the island of Sri Lanka to the equator to make his story work
with the physics of the situation. But both novels were fascinating in
the details they gave about the construction of "beanstalks."
Sheffield's book has a preface by Clarke.
I highly recommend that you read them and the technical references
given at the end. I'll post some more when I get home to my library.
However, these are works of fiction. There is no way to build a
"beanstalk" with current technology. We discussed this to death last
year, so I won't "launch" into it again.
-- Ken Jenks, NASA/JSC/GM2, Space Shuttle Program Office
kjenks@gothamcity.jsc.nasa.gov (713) 483-4368
"NASA turns dreams into realities and makes science fiction
into fact" -- Daniel S. Goldin, NASA Administrator
------------------------------
Date: Tue, 2 Feb 1993 07:21:52 GMT
From: kjenks@gothamcity.jsc.nasa.gov
Subject: Help on catching this
Newsgroups: sci.space,sci.physics
Rajesh Batra (rbatra@uceng.uc.edu) wrote:
: Scenerio: You're on the moon, a 1700 m/s container (containing ice) which
: weighs approximately 120 kg is hurled at you. How do you catch it such
: that you can salvage the ice? You have free reign over the container-
: hence the size/material.
Start with a smooth container (or no container at all -- ice itself is
fine). Aim it at a large, long funnel. The funnel narrows down into a
chute with gas injectors in it. Inject a little gas ahead of the block
of ice and let friction do its job and let the pressure build up in the
chute, slowing the block. Slide baffles into the tube as the ice
passes to recapture & recycle most of the gas.
_______
\______
\______________
--- O ---> ______________ chute ->
^ ice, incoming ______/
_______/
In the chute:
__________________________________________________________________
___________________|_O_________________________ __________________
| |
^ gas injector | ^ gas injector
^ baffle (in) ^ baffle (not in yet)
If the angle of the funnel is slight enough, the block of ice won't
fragment too much as it bounces in toward the chute. If you miss the
funnel, don't worry about that one -- it won't do much harm, if you
arrange its orbit right.
The funnel will get dinged up rapidly as you bounce blocks of ice off
of it. You might need to resurface it frequently (try more ice). To
avoid wear on the funnel, make the blocks of ice spherical. That way,
you won't care if they tumble and "hit wrong." Your chute may get
scraped up from ice which shatters in the funnel.
If your funnel is too difficult to hit with a purely balistic ice ball,
you could either add a guidance package to each ball (expensive), or
you could add "terminal guidance." There would be a position sensing
mechanism (possibly a couple of strings of photo sensors and a bright
light, maybe the Sun) and either a fluid impact (squirt gun) or
projectile impact device on the incoming path to the funnel. The
sensors figure out where the ice ball is, a computer figures out where
it should be, and the impact devices give it a nudge. If the ice ball
is unsalvagable, either nudge it high (so it misses the funnel
completely) or nudge it into an impact area (dump it, but keep most of
the mass on the moon). But this is expensive and complicated. You're
probably better off spending your money on better precision launch
equipment than better capture equipment. If you hit dead on every
time, you don't need to worry about all this.
You'll get a little bit of help from the moon's atmosphere, which is
small but will get larger in the area of operation of your catcher as
the ice sublimes into vapor.
Your chute will get warm -- even hot -- as the gas compresses and you
turn the massive kinetic energy of the ice ball into temperature and
pressure. Oh, and don't forget that pressure building up. If you
don't stop it, the ice ball will compress a column of gas in the chute,
come to a stop, then go spitting out the funnel again as the gas
expands. But don't let this be a disadvantage. If you arrange it
right, you'll have a terrific steam generation plant which can be used
to drive turbines and generate electricity. And the source of
energy is the kinetic energy of the incoming ice balls.
If you arrange the pressures and temperatures right, and prevent
escaping vapor with the baffles, you could have a trough of water at
the bottom of the chute. If you wait long enough between ice balls,
that water could be as smooth as glass, and you could skim the ice ball
off the water until friction slows it down and it melts into the
puddle. But waiting for the water to get smooth decreases your
plant capacity.
Or maybe you don't care about smooth water. As a block of ice comes
screaming in the funnel, the chute opens into a large, STRONG reservoir
of liquid water. SPLASH! Blub! Waves everywhere. Friction with the
water and the turbulence you've caused will slow that puppy down fast.
You've just turned all of that kinetic energy into thermal energy in
the water. More steam turbines. This option assumes you already have
a large body of water on-site on the moon -- certainly not a valid
assumption at the start of operations, but 120 kg blocks add up fast.
Maybe your second funnel ends in a splash.
You probably don't care if your ball of ice is intact at the end of
this process, as long as you capture most of its mass. So you might
want to fragment it (by inelastic collision[s]) as it comes in, and
catch the fragments in a big funnel. Since some of the balls will
probably fragment anyway, you might be in this state by accident rather
than design. Do a lot of testing.
Now the hard part: how do you hurl a 120 kg ice ball at 1700 m/s with
millisecond timing and microradian accuracy? 'Cuz that's what you'd
need in the launch equipment to make this crazy scheme work. But that
may not be part of your assignment. If this is homework, give credit
where it's due.
-- Ken Jenks, NASA/JSC/GM2, Space Shuttle Program Office
kjenks@gothamcity.jsc.nasa.gov (713) 483-4368
"Good ideas are common -- what's uncommon are people who'll
work hard enough to bring them about." -- Ashleigh Brilliant
------------------------------
Date: Tue, 2 Feb 1993 08:03:30 GMT
From: Dave Michelson <davem@ee.ubc.ca>
Subject: Posting Anonymously
Newsgroups: sci.space,sci.space.shuttle
In article <1993Feb01.234340.153062@zeus.calpoly.edu> cshuy@zeus.calpoly.edu
(No One Knows) writes:
>where was I? [etc]
To: "No One Knows" and other guilty parties
If you're not sure how to set your name, PLEASE consult your system
administrator. Posting anonymously or using only a "cute" pseudonym
to identify yourself *really* detracts from your post...
---
Dave Michelson University of British Columbia
davem@ee.ubc.ca Antenna Laboratory
------------------------------
Date: Tue, 2 Feb 1993 07:37:22 GMT
From: kjenks@gothamcity.jsc.nasa.gov
Subject: Well..
Newsgroups: sci.space,sci.misc,rec.arts.startrek.tech
Otto Maddox (bbs.maddox@gilligan.tsoft.net) wrote:
: How long would it take a ship traveling at Warp 1 to get to a
: planet that is 60 light years away?
With time dilation effects, no time at all. Subjectively speaking, of
course. Unless you include the time required to develop the engines,
build the ship and (the longest time of all) get the budget through
Congress. Then, 60 years is way too short.
-- Ken Jenks, NASA/JSC/GM2, Space Shuttle Program Office
kjenks@gothamcity.jsc.nasa.gov (713) 483-4368
"NASA turns dreams into realities and makes science fiction
into fact" -- Daniel S. Goldin, NASA Administrator
------------------------------
Newsgroups: sci.misc,rec.arts.startrek.tech,sci.space
Message-Id: <UfPV7VW00WB4BAbBcy@andrew.cmu.edu>
Date: Tue, 2 Feb 1993 01:17:05 -0500
From: "Jared M. Oberhaus" <oberhaus+@CMU.EDU>
Subject: Re: Well..
In-Reply-To: <uLgByB2w165w@gilligan.tsoft.net>
References: <uLgByB2w165w@gilligan.tsoft.net>
Sender: news@CRABAPPLE.SRV.CS.CMU.EDU
Source-Info: Sender is really isu@VACATION.VENARI.CS.CMU.EDU
60 years.
------------------------------
End of Space Digest Volume 16 : Issue 110
------------------------------