Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V15_0/V15NO079.TXT

Internet Message Format | 1993-07-13 | 34KB

Date: Fri,  7 Aug 92 05:00:07
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V15 #079
To: Space Digest Readers
Precedence: bulk


Space Digest                Fri,  7 Aug 92       Volume 15 : Issue 079

Today's Topics:
                         Calendar and Zodiac
              Energiya's role in Space Station assembly
                          Home made rockets
                More TSS information from NASA Select
                         NASA Tools (2 msgs)
                        Origin of Life article
                         Red-blooded ET's : )
                            Shuttle launch
                        Soyuz as ACRV (3 msgs)
     Soyuz as ACRV (Posting of previous discussion data) (2 msgs)
                       Star Trek (anti-)realism
                           Tether Questions
      Whats wrong with this CONDUCTOR (was: Tethered Satellites)

    Welcome to the Space Digest!!  Please send your messages to
    "[e-mail]", 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 [e-mail] (Internet).
----------------------------------------------------------------------

Date: 4 Aug 92 03:58:32 GMT
From: "Gregory N. Bond" <[e-mail]>
Subject: Calendar and Zodiac
Newsgroups: sci.space

>>>>> On 30 Jul 92 02:31:37 GMT, [e-mail] (John Roberts) said:

John> By the way, the Orthodox church still uses the Julian calendar
John> (in the US and Russia, anyway, and presumably elsewhere). I
John> believe the skew is currently 14 days, and should remain so
John> until AD 2100. Since the determination of the date of Easter is
John> partly a function of the phase of the moon, the lag between the
John> two observations of Easter is variable.

Easter is defined as (from memory) the first new moon after March
21st (equinox? Coincidence?  Wrong date?).  The orthodox easter uses
the Julian March 21st, the western church uses Gregorian.  So the
easters will either coincide or differ by 28 days, in some fixed but
not obvious pattern.

I think.

Greg.
--
Gregory Bond <[e-mail]> Burdett Buckeridge & Young Ltd Melbourne Australia
``USL has never sold long distance.  You're going after the wrong men in black
  hats.  (Or, in the case of Plan 9, black space suits)'' - Tom Limoncelli

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

Date: Wednesday, 5 Aug 1992 18:45:44 CET
From: "Hugh D.R. Evans" <[e-mail]>
Subject: Energiya's role in Space Station assembly
Newsgroups: sci.space

In article <[e-mail]>, [e-mail]
(Gerald Cecil) says:
>
>Re the radiation loads: if you get 4-13 rads/30 days INSIDE a Space Station
>module, how much worse is the cumulative exposure during the assembly phase,
>in suits?  Presumably you want to keep this well below 80 rads/30 days if
>the 50% mortality dose is 250-300 rads/30 days.
>--

Firstly, for the 28.5 degree orbit, the proton radiation dose is only
significant for about 10 % of the 13 orbit repeating trajectory (as the right
ascension precesses about the Earth, it take ~ 13 orbits to return to about
where it was initially). On most of these orbits, the SSF will miss the SAA, as
the highest latitude point of these orbits will be at the same longitude as the
SAA, and the lowest latitude point will be on the other side of the Earth.
I don't know what NASA's policy is regarding EVAs, but one of their require-
ments is probably that no EVAs will be performed on the orbits that traverse
the SAA.  So, there really isn't much of a problem with EVAs, except for the
time limitations imposed by the orbital characteristics.

I would, however be very interested to know the safety levels NASA imposes
on the shuttle crew for radiation levels.  As far as Mir goes, who knows
what the Russians considered a safe level?

Regards,
Hugh

ESTEC                   * Inet:   [e-mail]
P.O. Box 299            *     or  [e-mail]
2200 AG Noordwijk       * SPAN:   ESTCS1::HEVANS
The Netherlands         * BITNET: HEVANS@ESTEC

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

Date: 6 Aug 92 10:57:04 GMT
From: "Frederick A. Ringwald" <[e-mail]>
Subject: Home made rockets
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] writes:

> I have recently got into the field of making home-made rockets and have
> been experimenting with various types of cheap, readily availible fuels and
> cannisters.
[...]
> Launch sites have
> proved to be a bit of a problem as with the current state of political
> affairs here, we are a touch scared of being arrested.
>
> If anyone has any new/different ideas for fuels, chemical components,
> homemade flares, please let me know.


Please DO NOT DO THIS, for the sake of your safety and the safety of
everyone around you. This is a very good way to get KILLED or SEVERLEY
MUTILATED.

I know a former bass player and chemistry enthusiast who was making his
own solid rocket engines. He blew off all the fingers on his right
hand. I think he's wised up about homemade rockets/explosives
manufacture, often known as "basement bombing." He doesn't play bass
any more, either: can you guess why?

If you enjoy building and flying rockets, please see the newsgroup
rec.models.rockets. Their FAQ gives a good introduction to the hobby of
model rocketry, which if practiced carefully, is safe and a lot of fun.
Model rocketry isn't expensive: I paid for, built, and flew my first
models when I was 10. Model rockets aren't really toys, either: good
ones can fly over 1000m high, can glide or parachute down, and you can
have multistaged rockets or even flying scale models of famous
spacecraft, such as the Saturn V.

But DON'T make you own engines, and follow their safety rules. I also
know a father who, with his son, was making homemade rockets and not
bothering to test them for flightworthiness (also called aerodynamic
stability), and furthermore was igniting them in a non-standard and
patently unsafe manner (instead of using a safety-certified electrical
launcher, they were sticking lit punks into the rocket engines'
nozzles). One of the rockets shot up and burned his eye, damaging his
cornea severely. I hope he was eventually all right: he sure didn't
look it when I last saw him.

What you describe doing is amazingly dangerous. If you persist in it, I
hope you do get caught and arrested, as you are a public menace, if
you're still alive to read this post!

Fred Ringwald
Department of Physics & Astronomy
Dartmouth College
Hanover, NH 03755-3528 USA

P.S. Real rocketeers are usually meticulous about safety: because when
they aren't, things like the Challenger disaster happen.

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

Date: 6 Aug 92 05:47:44 GMT
From: John Roberts <[e-mail]>
Subject: More TSS information from NASA Select
Newsgroups: sci.space

Notes: STS-46 8/5/92 Mission Status Briefing (paraphrased)

Chuck Shaw   Dr. Nobie Stone   Billy Nunley
.............................................
Chuck Shaw - lead flight director

 - Fabulous success - everything worked except the actual mission [ :-) ]

 - It didn't work, but we learned a lot.

 - The dynamics of the deploy and rewind were very good - very controllable,
   and much more stable than expected. The material of the tether tended to
   damp out vibrations, which was hoped for but not counted on. Calculated
   minimum stable tether length was 300 meters - they only got to 256 meters,
   but it was still stable at that point.

 - On attempt this morning, the upper tether control mechanism (a motor with
   a clutch) at the top of the boom wouldn't work. It wouldn't move forward,
   and it wouldn't put tension on the reel. It also wouldn't pull the tether
   in, and it wouldn't disengage. Driving the reel motor put tension between
   the reel and the top of the boom, but wouldn't pull in the tether through
   the upper mechanism. The ingenious method that was finally used to unstick
   the upper mechanism was to retract the boom and take up the slack using the
   reel motor, then put the brake on the reel and re-extend the boom, thus
   using the deploy motors of the boom to pull on the tether between the reel
   and the upper mechanism. The tension rose to 40 [80?] newtons, then suddenly
   dropped to 6 N as the upper mechanism unjammed. Having gotten the tether
   loose, they started to retrieve the satellite. Retrieval went very well,
   and the satellite was very stable. While of course the full mission was
   not carried out, the dynamics people got a lot more experience than planned
   at the least stable and trickiest portions of the deploy and retrieval.

 - The thrusters on the satellite worked very well.

 - Control of libration worked exactly as expected. Vibrations were very
   small. The inline thrusters didn't have to be used until ~60 m.

 - (There was also mention of a vernier motor with a pinch roller above the
   upper controller mechanism, so that might be three motors involved.
   Or that may be the upper control motor mentioned elsewhere - I'm not sure.
   This morning, they also discussed the passive damping mechanism, which is
   a small ring on the upper boom through which the tether passes. The ring
   is attached to a surrounding frame by bungee cords, so motion of the
   tether that moves the ring from side to side eventually causes the energy
   of oscillation to be absorbed by the bungee cords.)

.............................................
Billy Nunley (TSS Project Manager):

 - Most of the hardware worked very well.

 - Post-flight analysis of the failed hardware is planned.

 - Science was significantly less than expected.

.............................................
Dr: Nobie Stone (TSS Mission Scientist):

 - The primary objectives of the mission science were missed completely.
   The voltages and currents produced were not large enough for most
   of the experiments.

 - The Italian satellite worked "perfectly". The new conductive paint
   was successful. It remained stable over time in vacuum, unlike the
   old paint.

 - One instrument was noisy, and one of the four electron guns failed due
   to a pressure surge from the orbiter.

 - The data collection and display systems worked. Scientific measurements
   show that gyrations induced during deploy damped out over the course
   of about 10 minutes.

 - Even at the shorter distance, the tether was able to generate about
   40 volts at about 15 milliamps. Voltage is directly proportional to
   tether length.

 - The tether offers a unique tool for space plasma physics and many other
   applications.

.............................................
Q&A:

 Q: Once you got it unstuck, why didn't you try to extend the tether further?
 A: Unlike the previous day, the new failure mode was not well understood.
    Though there was plenty of battery power[?], the "GN2" (gaseous nitrogen,
    used as a propellant on the satellite) was getting low. It is needed
    for the inline thrusters. There's a workaround to reduce or avoid the
    need for inline thrusters, called centrifugal operations. GN2 is also
    used for attitude control, but very little is needed for that - only
    3kg of the original N2 load was budgeted for that. However, they were
    running out of time, and they wanted to make sure the satellite was
    retrieved, so that was what they concentrated on.

 Q: What was the EVA contingency plan?
 A: If the jam couldn't be undone, two crew members would be sent out,
    one on the RMS, one on a sill, with the reel used for payload bay door
    contingencies, to pull the tether over to the reel, and reel it in by hand.
    Another option was to fly the Shuttle over to the satellite, and just
    gather in the loose tether. There was a period of 24 hours to decide
    the best way to do it. Since the tether was unjammed by control from
    inside, an EVA was not necessary.

 Q: What was the margin for the nitrogen and the batteries?
 A: 10-12 minutes GN2 margin, down from 42 minutes margin at the start of
    retrieval. If there hadn't been enough GN2, they would have started
    centrifugal operations to maintain tension on the tether. Battery
    margin was "almost half the mission" - plenty.

 Q: (What caused the jam?)
 A: When the boom trick pulled the tether free, the astronauts looked
    specifically for anything unusual about the tether, i.e. a kink. They
    didn't see anything.

 Q: Speculate on cause of jam. How might it have been prevented?
 A: (General description of possibilities mentioned above.) This was all
    tested and simulated many times on the ground, always with success.

 Q: Would it be wise for future missions to use stronger motors?
 A: Maybe. More analysis is needed. Stronger thrusters on the satellite
    are probably not needed.

 Q: How strong are the current motors?
 A: Vernier motor - ~30 newtons - just intended to overcome friction from
    the reel motor out. 12-17 newtons was predicted for normal operation -
    that's what they saw. During the reel jams, force rose to ~25 newtons.

 Q: How successful was the science part of the mission?
 A: None of the primary or secondary objectives of the mission were
    accomplished. (No high voltage.) Some of the objectives of opportunity
    were met - shuttle glow, interaction of electron beams with gas clouds
    and the orbiter, etc. The low-voltage performance was shown to be as
    expected, and the hardware for data collection worked.

 Q: With no more tethers at least for years, why not "go for it"?
 A: No indication that they could get far enough out for more meaningful
    science, and the risk was great, so they decided to retrieve the
    satellite and hope for another mission sometime.

 Q: How about a reflight?
 A: They'd sure like one. The science instruments apparently were chosen
    with the correct ranges of sensitivities, and they'd be happy to use
    the same instruments on a second flight.

 Q: Was it three separate problems, or could they have been related?
 A: That's yet to be determined - it's one of the things they've been
    looking for. Important to remember that zero-G and vacuum do strange
    things to heat flow, materials, etc. The satellite paint is an example
    of something that was anticipated and solved ahead of time.

.........................................................
Comments:
 - The TSS people seem to be really pinning their hopes on a future
   tether mission. They're now calling this "the first experimental
   flight of the tether". The question is whether the results of this
   mission will allow sufficient political support for further efforts.
   (It's undesirable when a failure on a first try discourages later
   attempts, but that's often the case.) The fact that almost everything
   appeared to work, and that the stability and vibration problems turned
   out to be much less severe than expected may help with this.

 - It sounds like they really need to work on tension control. Ideally,
   reel tension would be kept constant, even during deployment of the
   boom, so that buried loops would not be formed. That was *not* a feature
   of the current design, apparently. This may turn out to be one of the
   main things to watch out for on all deployed tether systems.

 - I thought the presentation was just a little more "slick" than it needed
   to be, though of course they have to put a good face on things to win
   support for future efforts, and they did accomplish a lot. The failure
   to meet the main science objectives is a significant failure, and
   intensive engineering investigation is warranted even aside from plans
   for further missions. I wouldn't say the presentation neglected to
   mention any of the shortcomings, but they laid it on a little thick
   when discussing the limited successes.

 - The use of the data from the science instruments to support the engineering
   analysis is a good idea. I guess that shows the value of the space flight
   and science teams talking to one another.

 - On the basis of the parts that look good, I hope they are able to continue
   the work with tethers.

John Roberts
[e-mail]

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

Date: Thu, 6 Aug 92 12:40:03 BST
From: [e-mail]
Subject: NASA Tools

> Actually, they have Gaffer's tape and not duct tape.  Gaffer's tape
is
> used in film production (hence its name) since it has the
desireable
> quality of not leaving any adhesive residue behing when you remove
it.
> It has the undesireable quality of costing a _lot_ more. (about $25
US
> in single rolls). My brother uses it by the yard when putting a
light on
> the wall on location shoots.  It is very nice stuff....
>


I used to do a lot of theater work and we used the names
interchangeably. We just bought it at the local hardware store
(incidentally would you believe that you CAN'T get it in DIY stores
here in Belfast!!!!) It also has a nice property that it tears
predictably. You can put up long runs of cable on the pipes and they
stay put until you pull out the safety ties, then you just give it a
yank and it pops the tape right down the line...

Maybe your brother just uses higher quality stuff. It does leave a
residue if it gets really baked onto the pipes. A lot of heat comes
out of a 1KW quartz...

But it does just about any job. Astronauts used it to construct the
"flyswatter" when they attempted to activate the Hughes satellite
that failed to fire? I think that was shortly before Challenger. So
it even works out in the big dark...

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

Date: Thursday, 6 Aug 1992 09:30:28 CET
From: "Hugh D.R. Evans" <[e-mail]>
Subject: NASA Tools
Newsgroups: sci.space

In article <[e-mail]>, [e-mail]
(John Roberts) says:
>
>-From: [e-mail] (Bruce Dunn)
>-Subject: NASA Tools
>-Date: 5 Aug 92 00:27:47 GMT
>-Organization: MIND LINK! - British Columbia, Canada
>
>-> John Roberts writes:
>-> Maybe they need to unpack the Ferrous Portable Leverage Application
>-> Mechanism (FPLM), the Passive Maximal Kinetic Transfer Device (PMKTD),
>-> and the Linear Metallic Abrasive System (LMAS), and try an EVA. :-)
>
>-Crowbar, hammer, and file?
>
>Very good! :-)  What I specifically had in mind was crowbar, sledgehammer,
>hacksaw. That LMAS acronym needs work - I agree it's ambiguous.
>
stuff deleted...

>and you've got all the basic tools to demolish, er, repair just about
>anything.
>For the ultimate in luxury, throw in an electric drill, grinder, tin snips,
>pop rivet tool. Plus assorted nuts, bolts, washers, and screws, of course.
>

Waddabout WD40?  No self respecting handyman would be without it!

On the serious side, anybody know how this miracle drug of mechanics works
in the space environment?

Hugh.

ESTEC                   * Inet:   [e-mail]
P.O. Box 299            *     or  [e-mail]
2200 AG Noordwijk       * SPAN:   ESTCS1::HEVANS
The Netherlands         * BITNET: HEVANS@ESTEC

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

Date: 6 Aug 92 11:05:51 GMT
From: "Frederick A. Ringwald" <[e-mail]>
Subject: Origin of Life article
Newsgroups: sci.space

In article <[e-mail]>
[e-mail] (Steve Troxel) writes:

> Why is it so difficult for people who call themselves
> scientists to explore the possibility that God created the
> earth and all the creatures on it?

When Pierre Simon de La Place published his treatise on Solar system
dynamics, Napoleon remarked that it did not mention God. La Place
replied "I did not require that hypothesis."

(There, that gets this discussion back to the topic of space, where it
belongs.)

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

Date: Thu, 6 Aug 92 12:25:49 BST
From: [e-mail]
Subject: Red-blooded ET's : )

> The Sun also has a magnetic field, as do many stars.  They have
> little iron (all of it vaporized).  The interaction of convection
> and magnetic fields on these bodies causes all sorts of interesting
> effects.
>


Stars not only have Fe, they are the producers of it. Although when
they start producing it in large quantities it is time to act like a
fly and leave the stellar system... Fe is the end product of
nucleo-synthesis... that is when supernova's happen in big stars. I'm
not sure of the exact range of stellar masses that proceed all the
way to Fe.

I'm sure if Paul thinks about it for a few moments he can write out
the equations for a late life O type star...

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

Date: 6 Aug 92 05:52:42 GMT
From: John Roberts <[e-mail]>
Subject: Shuttle launch
Newsgroups: sci.space

-From: [e-mail]
-Subject: Re: Shuttle launch
-Date: 31 Jul 92 22:53:00 GMT
-Organization: University of Houston

-...my experiment (Acceleration Measurement System) that I designed lifted off
-as a secondary payload (CONCAP III-01) on STS-46.  The purpose of this
-experiment is to measure the acceleration forces on the shuttle by the
-tether and its assocated end mass.  We expect the magnitude of these forces
-to be about 40 microgee.

-Our University also has another secondary payload (CONCAP II-01) which will
-expose many samples of superconducting materials to the Atomic Oxygen flow
-in order to ascertain if the unique oxidation states of the Atomic Oxygen
-are suitable for raising the temperature of the transition state to
-superconductivity for the ceramic typ superconducters that were first
-invented here at UAH a few years ago.

-Dennis Wingo, University of Alabama in Huntsville

I hope you will keep us posted on these experiments. :-)

John Roberts
[e-mail]

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

Date: Thu, 6 Aug 1992 05:09:00 GMT
From: [e-mail]
Subject: Soyuz as ACRV
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Henry Spencer) writes...
>In article <[e-mail]> [e-mail] writes:
>>By the way someone here stated that COMET could return 750 kg. That is not
>>true, COMET Weighs 750 kg. The return capsule payload is only 60 kg.
>
>As I said, I haven't seen specs for COMET itself, only for some of the
>proposals that went into COMET planning...
>
>But even ignoring that, note that I didn't say that *COMET* had a 750kg
>return capability.  I said that its *capsule* had such a capability.
>Unless COMET has changed radically since the early proposals, only a
>fraction of the mass that comes down in its capsule actually counts as
>payload.  But most of the extra is things that aren't needed for a
>dedicated payload-return capsule.

?

Henry the extras on the COMET are for the return capsule. The data system and
almost everthing else is in the orbiting portion that will not return. The
power system & Solar Cells etc.  I have a payload that is in the returnable
carrier so I do have a feel for this one.  The only extra stuff is wiring
for the power and data from the main module.

>
>The way you make things cheap and efficient is to design them to do one
>mission and do it well.  For example, transporting astronauts to/from
>orbit and supporting them for long stays while there are two different
>missions that should be done by different equipment; orbiter plus Spacelab
>is an insanely inefficient way to do this, if only because of all the mass
>that gets hauled up at great cost only to be brought down again a week
>or two later.  More to the current point, the vast majority of payload-
>return requirements -- real ones, not imaginary ones -- can be met with
>a simple, small, cheap expendable return capsule.

That is exactly what COMET is supposed to be Henry. It is funny how a lot of
the vaporware discussed on this net turns into expensive hardware once
development begins.

Dennis, University of Alabama in Huntsville.

PS I also have accelerometers on SpaceHab and maybe on Spacelab in the future.

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

Date: Thu, 6 Aug 1992 05:26:00 GMT
From: University Space Society <[e-mail]>
Subject: Soyuz as ACRV
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes...
>In article <[e-mail]> [e-mail] writes:
>
>>>Since Soyuz weighs a good deal less than Shuttle it should burn far less
>>>fuel. Polution should therefore be lower.
>
>>Oh. You left out resupply flights. Hm. You'd better go back to the drawing
>>board and add those up.
>
>OK. Since Soyuz and the resuply modules weigh less than the equivalent
>Shuttle flights, polution should be lower.
>
>Polution is furthur reduced since logistic modules are teathered down
>which means both fewer burns for logistics AND fewer burns for Freedom
>stationkeeping. This also saves additional $$ since less fuel is needed.
>
>How's that?
>
>   Allen
>--
Nothing except ignoring physics. The exaust velocity of the fuel is in the
thousands of meters per second which means that neither one will be a
pollution producer.

I happen to be a tether proponent and if we get over the disaster with TSS 1
we hope to use tethers on SSF no matter what scenario we use for resupply BUT
the large payloads that need returning will have to use Shuttle AND any
delicate experimental result must also use shuttle due to the much milder
G environment than is possible with any type of ballistic trajectory be it
a tether or retropropulsion.

Allen the dynamics for tethered return are not right to support station reboost
You have to have a mass that is a significant fraction of the Station's weight
before the reboost scenario becomes attractive. It turns out that the only mass
that satisfys this requirement is the SHUTTLE. This will lower the costs of
Shuttle ops since the momentum transferred to the station will be subtracted
from the Shuttle allowing for a greater payload to be carried up on the
Shuttle per flight.

Also I have not seen your derated values for your Atlas payloads to 270 nm. I
think your numbers are for a 105 nm transfer orbit. Subtract a VERY significant
amount for this.  Is that right Wales?

Allen please look a little closer at the numbers they do not lie. (except in the
hands of congressmen and the news media)

Dennis, University of Alabama in Huntsville

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

Date: Thu, 6 Aug 1992 11:56:35 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Soyuz as ACRV
Newsgroups: sci.space

In article <[e-mail]> [e-mail] writes:

>>>Oh. You left out resupply flights. Hm. You'd better go back to the drawing
>>>board and add those up.

>>OK. Since Soyuz and the resuply modules weigh less than the equivalent
>>Shuttle flights, polution should be lower.

>I'll hold my nose until someone can put up real numbers.

Let's see, we have two logistics flights but let's make it three just in
case. Each delivers 80,000 pounds of cargo and let's add another 80,000
for the carrier for a total of 160,000 per cargo flight. Add to that eight
Soyuz at 15,000 pounds each. This gives us:

1. Cargo (3 at 160,000 each):   480,000
2. Crew  (8 at 15,000 each):    120,000
       Total:                   600,000

So this approach will require us to maneuver 600,000 pounds near the
station every year.

A fully loaded Shuttle weighs in at 200,000 pounds and you need four
per year for resuply. This means the Shuttle will maneuver 800,000 pounds
near the station every year.

The Shuttle therefore must maneuver one third more mass and all else being
equal can expect to use 1/3 more fuel to do it.

You can take your fingers out of your nose now.

>However, if you claim brighter teeth and fresher breath next, I'm going to
>puke.

If that's the best reply you can give then this must be pretty convincing.

>>Polution is furthur reduced since logistic modules are teathered down
>>which means both fewer burns for logistics AND fewer burns for Freedom
>>stationkeeping. This also saves additional $$ since less fuel is needed.

>So did you add in the money for engineering and tether development? Nyet.

No I didn't. How much do you want to spend? Let's spend $4 billion on it
and put off the Lunar base for a year.

  Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "If they can put a man on the Moon, why can't they     |
|  [e-mail]     |  put a man on the Moon?"                               |
+----------------------260 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: Thu, 6 Aug 92 11:49:09 BST
From: [e-mail]
Subject: Soyuz as ACRV (Posting of previous discussion data)

> Next, watch for Allen to pull some more numbers out of his hat to
show
> that you could actually get a fully functional moonbase from
materials
> bought at K-mart and have change left over for a movie.....
>


In other words he's a REAL engineer?  Personally, I'd need to do the
shopping in at least a Busy Beaver DIY store in a major american
city... :-) :-)

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

Date: 6 Aug 92 08:08:48 GMT
From: [e-mail]
Subject: Soyuz as ACRV (Posting of previous discussion data)
Newsgroups: sci.space

In <[e-mail]> Mark Littlefield writes:
>Next, watch for Allen to pull some more numbers out of his hat to show
>that you could actually get a fully functional moonbase from materials
>bought at K-mart and have change left over for a movie.....

  Cute, however ob-numbers, you wouldn't happen to have any to
support your viewpoint would you ???
 -----------------------------------------------------------------
               ** Of course I don't speak for IBM **
Greg Nicholls ... [e-mail] or [e-mail]
                  voice/fax: [phone]

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

Date: 6 Aug 92 11:03:21 GMT
From: "Frederick A. Ringwald" <[e-mail]>
Subject: Star Trek (anti-)realism
Newsgroups: sci.space

Well, my two favorite Star Trek anti-realisms are both from the old
series:

1) The time when they flew back to the 20th century and picked up that
pilot (etc., etc.).  I distinctly remember that when flying inside the
Solar system (they were rounding the Sun, to go ahead in time or
whatever...), there were *stars streaming by them*!

2) No real navy would let a 35-year-old command a capital ship, no
matter how good he was (unless there had just been heavy losses in a
war, in which case exploration would not be a high priority).

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

Date: Wed, 5 Aug 1992 12:55:52 GMT
From: "Michael K. Heney" <[e-mail]>
Subject: Tether Questions
Newsgroups: sci.space

I have a question or two about tethers.  I've heard two primary uses for
thethers - one being an energy exchange with the ionosphere, which either
generates/uses electricity and raises/lowers the systems orbit, and the
other as a way to exchange momentum between masses on opposite ends of the
tether, boosting one and lowering the other.

First question - is the above correct?

On the electrical generation - I'm a bit confused as to which way the
tether is deployed.  On the current shuttle flight, the talk is that the
TSS is "lowered" on a 12.5 mile tether.  Is "lowered" the correct term?
I have trouble with the orbital mechanics if that's the case.  It would
seem to me that the TSS would have to be in the same orbit as the shuttle,
trailing it by the length of the tether.  Also, what mechanism is used to
actually get the tether to extend, as opposed to forming a bunch of
conductive spaghetti?

Similarly, on the momentum transfer idea (I've seen shuttle/SSF as the
pair of masses) - how would you "lower" the shuttle (since the tether isn't
rigid, you can't just push against it)?

Thanks for any comments/clarifications for us tether-impaired readers ...



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

Date: 6 Aug 1992 00:27:51 -0700
From: Steven Robiner <[e-mail]>
Subject: Whats wrong with this CONDUCTOR (was: Tethered Satellites)
Newsgroups: sci.physics,sci.space

In article <[e-mail]> you write:
>In article <[e-mail]>, [e-mail]
>(Steven Robiner) writes:
>|>
>|>Excuse me, but isn't something missing from this "Tethered Satellite"
>|>experiment?  The shuttle is at one end, and the satellite is at the
>|>other, right?  But that's an open circuit, so where's the load
>|>joining the ends of this 'generator.'?
>|>

 [... stuff deleted ]
>of electrons, it will shed them when its potential compared to the
>local plasma is higher than the work function for the shuttle surfaces.
>So now you have the "infused" electrons into the flux tube that contains
>the shuttle. Eventually normal plasma-plasma and plasma-neutral interactions
>will allow the electron to move back to its original flux tube. This however
>may take some time. So the circuit is really completed in the same sense
>that grounded circuits are completed, except here we don't have a good ground

But in space, the plasma is not a great conductor, and in fact, electrons
moving through a magnetic field should be repelled from traveling
in a direction opposite from the induced current in the tether, right.

I mean, just because the electrons aren't in a wire shouldn't mean that
they aren't affected.

So how will the current manage to travel back up to the satellite, without
going through the same resistance that generated those electrons in the
first place?

(btw, I guess the point is moot, since the tether is stuck at the moment,
but theoreticalyl, what would really happen? )





=steve=

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

End of Space Digest Volume 15 : Issue 079
------------------------------