Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V11_1/V11_139.TXT

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Subject: SPACE Digest V11 #139

SPACE Digest                                     Volume 11 : Issue 139

Today's Topics:
             space news from Feb 5 AW&ST
           Re: Artificial Gravity rephrased
         Solar System Questions from a Novice
            Re: Artificial Gravity
          Re: Spacecraft drives and fuel efficiency
                Saturn's Rings
             Keplarian Elements Wanted !
----------------------------------------------------------------------

Date: 12 Mar 90 05:11:02 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: space news from Feb 5 AW&ST

Arianespace starts testing on an "external inflatable mattress" to shield
the base of Ariane 4's payload fairing against engine noise somewhat.

Substantial Moon/Mars funding request in NASA's new budget request may
help Congress take the project seriously; the lack of any funding for
it to date has not helped its credibility.

FY91 budget request from NASA is $15.1G, a 23% increase.  First major
funding in 25 years for an unmanned lunar mission, to wit the Lunar
Observer remote-sensing orbiter.  Predictable big lumps of money to get
space station hardware started, various Mission-To-Earth projects underway,
and Moon/Mars technology work rolling.  Long-lead funding for an unmanned
life-sciences series of Earth-orbit missions, carrying animals etc. for
studies into effects of free fall.  [This may be partly in response to
unhappiness over the decision that there will be no animal facilities on
the space station.]  Major expansion for commercial-space-related work.
$229M for buying commercial launch services.  Funding for long-duration-
orbiter hardware.  And $119M for NASP.

New shuttle manifest, the result of the Hubble launch delay and the need
to protect the launch window for Ulysses this fall.  Gamma-Ray Observatory
slips from June to November.  Infrared Backscatter Signature Survey (USAF
and SDI) slips from November this year to Jan 1992.  The Astro-1 mission
(UV telescope package attached to the shuttle) remains set for May, but
the Astro-2 and Astro-3 missions in 1992 and 1993 have been shelved.

NASA offers to move ESA and JSA modules up in the station assembly
schedule, although available power will be very limited early on.
ESA is cautiously in favor; US users will see their hardware delayed
and are expected to be opposed.  This offer came a few days before
representatives of ESA, JSA, and ESA's major national agencies testified
before a House committee.  It seems to have mollified them only slightly;
they were openly pissed off about not being consulted over last fall's
schedule and design revisions.  "Partners do not make decisions unilaterally
that will damage the investment of the other partners... Neither do they
simply shift their own difficulties onto their partners' shoulders..."
"ESA still does not know the full extent of NASA's new proposals."
"...could raise great difficulties in continuing to secure political
and financial support."  Canada was not represented at the hearings
because Canadian law bans government officials from activities that might
be construed as lobbying foreign legislators.

Picture of LDEF in Columbia's cargo bay after arrival at KSC.

General Samuel C. Phillips, head of Project Apollo from 1964 through
Apollo 11, dies Jan 31.

Short slip in Atlantis's secret launch as suspect fuel pump is replaced.

First images from Spot 2; it seems to be working.

Arianespace sets commercial prices for use of the ASAP auxiliary-payload
platform on Ariane.  (ASAP carried the amateur-radio satellites on the
Spot 2 launch.)  $600k for the whole thing, which can carry up to six
small satellites.  Launch opportunities will be relatively few, since
ASAP will not fit in a two-primary-payload configuration, and most Ariane
launches carry two comsats.  Arianespace is also looking into heavier
secondary payloads.
--
MSDOS, abbrev:  Maybe SomeDay |     Henry Spencer at U of Toronto Zoology
an Operating System.          | uunet!attcan!utzoo!henry [e-mail]

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

Date: 12 Mar 90 04:30:02 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!helios.physics.utoronto.ca!physics.utoronto.ca![e-mail]  (Christopher Neufeld)
Subject: Re: Artificial Gravity rephrased

In article <[e-mail]> [e-mail] (Zaphod Beeblebrox) writes:
>Before I get majorly flamed here I would like to rephrase my question
>about artificial gravity on a ship. . .sure a spinning 'donut' at part
>of the ship and the astronauts can jog around or whateven on the inside
>circumference experiencing a normal force from the floor. . . and a person
>who falls out of an airplane feels 'weightless' (no air resistance) because
>there is no normal force exerted on him by the floor, the earth, etc.
>but concerning circular motion to induce artificial gravity. . is this same
>exact effect as gravity?
>
   Almost exactly the same. There are two important differences.
- Tidal effects are different in the two systems. The centrifugal "force"
goes linearly with distance from the centre of the cylinder, while the
gravitational force goes as the inverse square of the distance from the
centre of mass, assuming higher order multipole effects to be unimportant.
Your head would weigh less than your feet in a cylinder with a small
radius. You'd probably get very, very sick if your head projected into or
beyond the axis of rotation.
- The coriolis "force" is inextricably linked to the rotating cylinder,
while it can be completely absent on a planetary body. The coriolis
pseudo-force results in apparent deflections in the paths of bodies falling
through the field.
   The first effect would be noticeable to human senses for cylinders of
radius less than about ten metres. The second effect may or may not annoy
your balance centres (anybody know of any studies done into this?).

>Sure the floor is pushing the guy up and he
>feels 'heavy' but there is no force say on his arm pulling it down. . .???
>Sure his arm is attached to his body and his feet are being pushed 'up' and his
>arm comes along for the ride but is this the same exact effect as gravity
>pulling equally over his whole mass??
>
   Yes it is. The arm has to turn in a circle as well, so if it weren't
attached to the body it would fall toward the floor of the cylinder. It
would actually fall in a spiral, hitting the ground to anti-spinward of
where you expect it to hit. Ugh, enough of these falling body parts
analogies.

>. . .maybe a better question is what scale would this
>have to be attempted say on a trip to Mars. . and how much energy would be
>needed to make up for friction on the bearings etc.
>
   As much energy would be needed as is dissipated in the bearings. What
this is obviously depends on many things, such as the composition of the
bearings, the size of the carousel, the angular velocity of the carousel,
the uniformity of the mass distribution around the carousel, and the rate
at which masses (such as people) shift around the carousel.

>and would the angular
>momentum of such a spinning section make turning the ship more difficult
>during the flight etc.. . .hey I only saw the movie. .
>
   Well, this isn't Star Wars. The ship would know weeks ahead of time when
it had to turn, and because the ship would probably spend the time before
then in free-flight, you have weeks to turn the ship around. If you are
planning several course changes in quick succession at the rendezvous point
you'd almost certainly spin down the carousel. Quick turnings with the
carousel rotating would place torque stresses on the bearings and would
require heavier construction of the ship than would be required by the
other mission criteria.
   Turning the ship is anything but intuitive. If the ship has the carousel
spinning counter-clockwise around its long axis, and you want to turn the
long axis to the right in some set of coordinates, you have to fire the
thrusters which push down on the ship from above. In other words, the
thrusters which point your ship down when the carousel is stationary point
your ship to the right when the carousel is spinning.

>Mark. . MXP122 at psuvm.psu.edu


--
 Christopher Neufeld....Just a graduate student  | "I always think there's
 [e-mail]              | a band."
 [e-mail]          Ad astra! |   Prof. Harold Hill
 "Don't edit reality for the sake of simplicity" |   (The Music Man)

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

Date: 9 Mar 90 23:28:07 GMT
From: ladcgw!hacgate![e-mail]  (Lori + 8/9)
Subject: Solar System Questions from a Novice

Forgive the novice questions....I've never posted to sci.space before,
so I'm not sure if they will be inappropriate or not.

I just bought an old poster of our solar system from a swap meet last
weekend, and some of the facts on it are really intriguing.

Can someone answer a few questions about Mercury?  Its temperature is
hundreds of degrees F on the sunny side, and (fewer) hundreds of degrees F
below zero on the dark side.  The poster also says that it 88 days to
rotate.  What would Mercury's climate be like if it rotated as fast
as the earth?  How fast would it have to rotate to produce a moderate
or life-supporting climate, at least at certain latitudes (longitudes?)?

Also, the earth's atmosphere is very different from all the other
planets.  (In fact, they all seem unique.)  Could someone explain why?

Are there dual-sun solar systems?  This poster didn't seem to
think so (but hey, it's pretty old).  If there are, how do the suns
revolve around each other?  Would the bigger sun tend to draw the
smaller one toward it?

Here's a pretty dum question, I'm sure....Does our sun rotate?  Which way?
Does the whole solar system rotate with it?


...lori

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

Date: 12 Mar 90 03:40:23 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!qucdn![e-mail]  (Arnold G. Gill)
Subject: Re: Artificial Gravity

In article <[e-mail]>, [e-mail] (Zaphod
Beeblebrox) says:
>
>How realistic is the idea that if a spaceship had a section revolving that
>the astronauts could just hang around in there and experience 'gravity'
>i.e. like in the movie 2001. . .wouldn't the spinning section have to keep
>accelerating to have the this effect???
     It does keep on accelerating, but that is actually not the important
facet of this question.  I beleive you are asking whether the spinning section
must have a motor attached to keep it spinning.  In general, the answer is
yes, but only enough to overcome the friction of the bearings and supports
that hold it in place.  Think of the rotating cylinder in terms of energy
rather than forces.  A spinning cylinder can only lose energy through some
type of frictional forces, whether they be direct contact (like ball bearings)
or at a distant (like magnetic braking, etc).  If the cylinder cannot lose
energy, it will not slow down!
-------
 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
|  Arnold Gill                        |                                     |
|  Queen's University at Kingston     |     If I hadn't wanted it heard,    |
|  BITNET   : gilla@qucdn             |       I wouldn't have said it.      |
|  X-400    : [e-mail]  |                                     |
|  INTERNET : [e-mail]  |                                     |
 -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

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

Date: 11 Mar 90 16:39:05 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!watserv1!watdragon!watyew![e-mail]  (Brian or James)
Subject: Re: Spacecraft drives and fuel efficiency


 I think perhaps Mr. Ryan is incorrect in his statements about energy contents
of high exhaust velocity boosters. It's true that mass ratios go down as
Ve increases, but the energy tied up in getting the reaction mass to Ve goes
up exponentially (E~V*e2). A pure 'photon-drive' style booster would be one
hell of good light show before your eyes ran down your face, and would be a good way to drive a mohole at the same time (My texts are inaccessable right now.
Could someone post the power output of a hundred ton launch vehicle boosting
at 4ish gs propelled by a pure annihilation booster?). Not that anyone advocatedusing these extreme approach, of course.
  Whem I said that the detonation of an annhilation  energised booster  would
be survivable at short ranges, I meant on the order of 1000 meters or so, and
I assumed a launch mass of only a few hundred tonnes using a couple of mg of
antimatter. Mr. Maroney advocates only producing this stuff in space (Lunar
Farside, anyone?). The problem with that is the current lack of well developed
power generating systems in space (OK, there's one *big* fusion generator, but
it's currently hard to get a direct feed cheaply). If you put the am source
on Earth, you can use the powergeneration systems in place now. If prudence
dictates a remote location like Farside, then I suspect that antimatter is
unlikely to contribute anything useful for a long time.
                                                          JDN

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

Date: 11 Mar 90 15:52:15 GMT
From: eru!luth!sunic!mcsun!ukc!harrier.ukc.ac.uk![e-mail]  (Stephen Thomas)
Subject: Saturn's Rings

Hello. I have a couple of queries about Saturn's ring system that I hope
some of the readers out there will be able to assist me with. I apologise
if they are questions that have been asked before - I have not been
reading this group for very long.

The first query is this: What is the composition of the rings? I have
read that they are composed of ice and rock, but I would like to
know a little more about the makeup of the rings.

The second query: Last I heard, the ring system was maintained by a
shepherd (sp?) moons arrangement. How delicate is this system? In other
words, if some of the moons were removed (somehow), what would happen
to the rings? Would it settle into a new ring system, or would it
tend to disintegrate? If it did disintegrate, how long would this
process take? I realise that the answers to these questions depend
on how many and which moons were removed, but I would be interested
in knowing what others might think.

I ask out of curiosity, one of those thoughts which strike you when
you are trying to think about something else, and then won't let go. :-)

Stephen

--
  Never give   |  Stephen Thomas
  fate an      |  JANET: [e-mail]
  even chance  |  Telephone: [phone] ext 3824
               |  Snail: Computing Lab, University of Kent at Canterbury, UK.

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

Date: 12 Mar 90 06:09:32 GMT
From: milton![e-mail]  (Eric Swansen)
Subject: Keplarian Elements Wanted !

Is there anyone (or anyplace) that can provide we with recent Keplarian
Elements for satellites ?

I've recently found this neat program that tracks satellites, but I need
to add in the data for the "birds" that I'd like to monitor...
In particular Salyut 7, MIR, Space Shuttle (updated 2x daily+/-) and
perhaps other birds more visible from Earth....
Ideally I'd like to TELNET or FTP to a site, but that is probably asking too
much......
Any Suggestions ?
-------------------------
Eric C. Swansen
University of Washington
DC-13
Seattle
[e-mail]
------

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End of SPACE Digest V11 #139
*******************