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------------------------------
Date: Fri, 15 Jan 1993 13:13:20 GMT
From: Brad Kepley <kepley@photon.phys.unca.edu>
Subject: Elementary Ballistics
Newsgroups: sci.space,sci.physics,alt.pagan
>boylan@sltg04.ljo.dec.com (Steve Boylan) writes:
>
>>
>> Gee, this sounds like it ought to be a simple question . . .
>>
>> What speed (using the term to refer to the magnitude of the
>> velocity vector) must be imparted to a body at the surface of
>> the Earth to achieve low Earth orbit? I've seen estimates
>> bandied about that ranged from 2.2 km/sec. to 8 km/sec.
>> Naturally, I can't recall enough of basic mechanics to
>> figure it out for myself, and I can't find my mechanics
>> text . . .
>>
8 km/s (27000 km/h) is what is needed to *maintain circular
orbit.
>>
>> If I remember my ballistics correctly, in the absence of an
>> atmosphere, something launched by acceleration on the surface
>> can achieve an elliptical orbit . . . that is tangent to the
>> surface, which is probably not good on a body like the Moon
>> and decidedly a problem with an atmosphere around. What kind
>> of change in velocity is needed to round out the orbit so
>> it would stay outside the Earth's atmosphere?
Actually, it takes *more* velocity for an eliptical orbit ( about 30000 km/h).
>>
>> For that matter, how much extra work do you need to do to
>> get a payload out of the Earth's atmosphere?
The work will depend on the payload and = delta KE or 1/2 mv^2 , I think.
Escape velocity is about 40000 km/h.
------------------------------
Date: Fri, 15 Jan 1993 14:24:49 GMT
From: John F Blanton <blanton@mksol.dseg.ti.com>
Subject: Elementary Ballistics
Newsgroups: sci.space,sci.physics,alt.pagan
The problem of launching bodies into orbit from a planet's
surface is one I have worked out for several scenarios. It's
an interesting situation, relatively easy to solve and often
with surprising results.
However, I can't submit a lengthy post on this right now. If
no one posts a valid response by the end of today I will try
to recall some of my previous results.
John Blanton
blanton@lobby.ti.com
------------------------------
Date: 15 Jan 93 13:42:46 GMT
From: Ken Sheppardson <kcs@freedom.larc.nasa.gov>
Subject: Freedom's orbit
Newsgroups: sci.space
In the studies we're doing looking at post-PMC station logistics
requirements, we're using the baseline station reboost strategy of
"180 to 150". That is, an orbit in which the minimum altitude is
defined as the altitude from which it would take 180 days to decay to
150 nautical miles. This altitude varies over the 11 year solar cycle
and on whether you plan for a nominal or a "2 sigma bad" solar cycle.
The altitude tends to vary from 210-230 or so depending on where
you are in the reboost and solar cycles. As an approximation, folks
around here doing launch vehicle manifesting are using 220 nmi. 28.5
degrees is the baseline orbit, although there's a small radical fringe
contingent of folks who continue to advocate/consider a higher
inclination to allow for the use of Russian facilities and vehicles.
Go figure.
---
Ken Sheppardson
kcs@freedom.larc.nasa.gov
------------------------------
Date: Fri, 15 Jan 1993 15:46:15 -0500 (EST)
From: JTRIMBLE@nhqvax.hq.nasa.gov
Subject: Freedom's orbit
Regarding the requests from Fifield and Ardalan: I checked with some of the Space Station engineers here in Reston, and the orbit for station is 220 nmi. The inclination is, as Ardalan stated, 28.5 degrees.
Jeanne Trimble
Space Station Library
JTRIMBLE@NHQVAX.HQ.NASA.GOV
------------------------------
Date: 15 Jan 93 12:05:28 GMT
From: Nick Szabo <szabo@techbook.com>
Subject: future space travel
Newsgroups: sci.space,alt.sci.planetary
roberts@cmr.ncsl.nist.gov (John Roberts) writes:
>...the dry valleys of
>Antarctica. Conditions there are very reminiscent of Mars - bitter cold
>much of the time, bare rock, high winds, and dryer than the Sahara Desert.
>(There's even fairly intense UV, by Earth standards.)
>Yet life is there - algae living under rocks, sheltered from the most
>extreme cold, and getting light needed for photosynthesis from sunlight
>shining *through* the rocks. Other algae are found *inside* rocks, located
>between the component crystals of the rock.
There are some _big_ differences. The most important is probably
pressure. When water gets above freezing in Antartica from the
sunlight, it melts into liquid. On Mars, it sublimates into vapor:
there is no liquid state at that pressure. It's been over a
billion years since any signficant part of Mars got above the triple
point of water.
Some other differences: the water content of Mars surface rock
is, in most places, orders of magnitude lower than that in Antartic
ice. The most basic living processes discriminate against C13,
increasing the C12/C13 ratio; Mars' carbon has been untouched
by such processes.
The ratio of hope for life on Mars, to the actual probability
of same, is nearly infinite. Boy do I wish there was a futures
market on this! :-)
--
Nick Szabo szabo@techboook.com
------------------------------
Date: 15 Jan 93 14:34:19 GMT
From: Thomas Clarke <clarke@acme.ucf.edu>
Subject: Handling Antimatter
Newsgroups: sci.space
With all the discussion of antimatter, its time to bring
up my pet scheme for handling the stuff.
Imagine a molecular cage, say a buckminsterfullerene. The cage has a
net positive charge (missing an electron). A negative antiproton
could then be trapped in the center of the cage where it would
only "contact" and be repelled by the orbital electrons. Since
electrons and antiprotons don't annihilate, this arrangement should
be stable as long as the cage is intact. Various molecular
groups added to the outside of the cage could give this material
useful properties such as solubility.
To make a wonderful rocket fuel, disolve some of the caged antiprotons
into a suitable working fluid such as water. When injected into a
running rocket engine, the heat will disrupt the cage, releasing the
anitproton which will annihilate releasing energy and running the rocket
engine. It might be a little tricky to get the engine started, but
it shouldn't be impossible. The charged fuel is also a potential
(nuclear?) explosive, so one would have to take usual precautions.
The caged antiprotons would also have military applications - what
doesn't? A few milligrams of passivated antiprotions inserted into
the tip of a rifle bullet would let the average infantryman totally
destroy a main battle tank!
--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
A report carried in `The Guardian' (Thursday January 14) detailed an upcoming Russian space event.
Apparently a recent Progress cargo ship (1992-71A?) currently docked (or station keeping) with Mir is due (maybe next month) to unfurl a 65 foot 'space mirror' constructed from aluminium coated plastic film, in an experiment known as `Znamya' (Banner).
Apparently this is an attempt to extend the daylight hours of the Siberian regions by reflecting sunlight to the required areas.
It occurs to me (obviously?) that this may make an interesting object for observation. Does anyone have more details? Times and dates would be useful as a basis for formulating some observation predictions.
