Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V16_3/V16NO346.ZIP/V16NO346

Internet Message Format | 1993-07-13 | 32KB

Date: Sun, 21 Mar 93 05:00:14
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #346
To: Space Digest Readers
Precedence: bulk


Space Digest                Sun, 21 Mar 93       Volume 16 : Issue 346

Today's Topics:
                      Aurora spotted ? (2 msgs)
                         CD for Pluto Mission
   Clueless Szaboisms (Was Re: plans, and absence thereof) (2 msgs)
                      How to cool Venus (2 msgs)
               Just a little tap (was Re: Galileo HGA)
                 Magellan Update - 03/19/93 (2 msgs)
         Predicting gravity wave quantization & Cosmic Noise
                     SR-71 Maiden Science Flight
                 SSTO: A Spaceship for the rest of us
                              tether II
    Water Simulations (Was Re: Response to various attacks on SSF)
             Why use AC at 20kHz for SSF Power? (2 msgs)
                        will dust cool Venus?

    Welcome to the Space Digest!!  Please send your messages to
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----------------------------------------------------------------------

Date: Sat, 20 Mar 93 14:21:41 GMT
From: Dean Adams <[e-mail]>
Subject: Aurora spotted ?
Newsgroups: sci.space

[e-mail] (Lawrence Curcio) writes:
 >A Mach 8 spy plane is certainly not ordinary either.

No, but a Mach 6 version might be "ordinary" to those
cleared into a certain Special Access Program...  :->

 >UFO reports are - that was my original point.
Dime a dozen...

 >It strikes me that the evidence/arguments for the AURORA are
 >no stronger than those for UFO's,

Ha!  Not by a *longshot*, unless the "UFOs" you are talking about are the
product of Lockheed's Skunk Works.  You can talk about "alien invasions"
until you are blue in the face, and the "evidence/arguments" will never
add up to what you can find connected to a certain facilities in Burbank
and Palmdale...

 >yet UFO's are (rightly or wrongly) dismissed out of hand,
Sometimes...

 >and the AURORA is (rightly or wrongly) embraced - by the same
 >group of individuals.

It is "embraced" by many people who follow these types of programs.
"UFO's" don't need to have anything whatsoever to do with it.

 >In fact, now we have a rule that says:
 >1) If a sighting can be a UFO sighting or an AURORA sighting,
 >it's an AURORA sighting;

Just WHAT "aurora sightings" are you referring to?  There are only
a couple of documented examples of such incidents in the first place.

 >2) If the sighting cannot possibly be an AURORA sighting, dismiss it.

What are you talking about?   Unlike the ufo world, there are
NO such wholesale barrages of "aurora sightings" around.

 >Don't mistake me for a UFO advocate; I am merely impressed by the
 >social dimension of what passes for common sense.

Hmmm...  I am more impressed (depressed) by social dimensions
that often seem to seriously LACK common sense...

 >IMHO, we should be consistently skeptical of *ALL* sightings
 >noises and rumors,
Makes sense.

 >but allow room in our philosophies for extraordinary
 >things - even Mach 8 spy planes.

BUT, a Mach 6 spy plane is VASTLY less extraordinary than "alien invaders".
This is a good example for using common sense.  That same common sense,
combined with logic and various evidence, says there very likely *IS* a
high-mach SR-71 follow-on vehicle operating.  And NONE of that is anthing
even remotely connected with "UFOs".

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

Date: Sat, 20 Mar 1993 12:43:55 -0500
From: Lawrence Curcio <[e-mail]>
Subject: Aurora spotted ?
Newsgroups: sci.space

In reply to Dean Adams: The UFO folks are certain that the "Information"
they have is reliable as well. Reliability is a value judgement that is,
in part, socially based. I wish to thank Mr. Adams for his demonstration
of my point, and as a token of my appreciation, I also vouchsafe him the
last word in the exchange.

-Larry C.

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

Date: 20 Mar 93 15:29:06 GMT
From: FRANK NEY <tnc!m0102>
Subject: CD for Pluto Mission
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Arthur Chandler) writes:
>
>  Someone refresh my memory: what was in the last "message in a bottle"
>spaceship (I seem to recall a diagram of the solar system, drawings of a
>man and a woman, etc.), and what form (paper, record, videotape, etc.)
>did it take?


What you describe was the plaque on the Pioneer probes.  It was (I
believe) etched on gold.

The Voyayer probes contained a record and stylus, plus instructions on
the cover on how to extract information from it.  If you can find a
record or book called 'Sounds of Earth,' this is the content of that
record.

What I was contemplating was a CD-ROM using most of the scientific
information from 'Sounds of Earth' as a starting point.
--
The Next Challenge - Public Access Unix in Northern Va. - Washington D.C.
703-803-0391 To log in for trial and account info.

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

Date: 20 Mar 1993 09:51:55 -0500
From: Pat <[e-mail]>
Subject: Clueless Szaboisms (Was Re: plans, and absence thereof)
Newsgroups: sci.space,talk.politics.space

Dennis,

    You work on staff for the University of Alabama Huntsville
these days right?   So forst Dennis gets to deal with typical low
university pay.  That army of Undergrads at minimum wage depresses
everyone elses wages.   Second any contracts they get at UAH,  first come
through a NASA center, with it's overhead 30%  according to allen,
and then the university takes it's Overhead charge 50-60 %  if my figures
are anywhere near current.     leaving dennis to wrok on a prject with
1/3 the allocated funds.

It's these kinds of overheads that are destroying projects.

pat

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

Date: 20 Mar 1993 12:00 CST
From: [e-mail]
Subject: Clueless Szaboisms (Was Re: plans, and absence thereof)
Newsgroups: sci.space,talk.politics.space

In article <[e-mail]>, [e-mail] (Pat) writes...
>
>Dennis,
>
>    You work on staff for the University of Alabama Huntsville
>these days right?   So forst Dennis gets to deal with typical low
>university pay.  That army of Undergrads at minimum wage depresses
>everyone elses wages.   Second any contracts they get at UAH,  first come
>through a NASA center, with it's overhead 30%  according to allen,
>and then the university takes it's Overhead charge 50-60 %  if my figures
>are anywhere near current.     leaving dennis to wrok on a prject with
>1/3 the allocated funds.
>
>It's these kinds of overheads that are destroying projects.

First of all I have two different lives here. First I work on "official"
UAH contract efforts such as SpaceHab, Spacelab, CONSORT, COMET etc...
(by the way I have a payload on each of these misions in the next year or
so) then there is my SEDSAT 1 work.

On the NASA contract side we have won contracts because we are consistently
cheaper than anyone else and we get the job done.  The reason that my
contract pay is low is that I have a 2 year degree in a University
town environment. A 2 year degree and a cup of coffee are both worth 50 cents
here.

My SEDSAT 1 work is at this time funded 40% and as of next month be 100%. This
is money that I personally go out and raise. The University takes no overhead
from this money as their contribution to our project.  The standard university
overhead on fully burdened efforts is 36.6%. This is marginally less than
the typical mark up of 40% in the commercial retail world. This margin is
what typically is profit in the real world.  However If I do contracts and
they are fully burdened we still get 4% of the money back in what is called
incentive funds. This is for new projects or any darn thing we want to spend
the money on.

There are very few undergrads working in research at a meaningful level
around UAH besides me and a couple of others. The technical disciplines that
are used simply preclude this type of labor. In general university salarys
are lower than the private sector but there are other compensations for that.

As for the clueless post that someone else made. I do this because this is
where our future is. I cannot help that the Szabos and others out there
are looney toons and scream at the top of their lungs about their pet projects.
Mony is easy to make in this world and I have made it and spent it. There is
more to this life than money and there is more to life than screaming at
the top of one's computer lungs over sci.space.

The human race is at a threshold and a choosing point. We can either turn
inward as the Jane Fonda's and Ted Turner's and their ilk want us to do and
turn our lives over to "those who know better" or we can turn outward and
take our future into our own hands as our ancestors have for thousands
of years. This network and the people who post here are for the most part
intelligent and have strong convictions: However there is a fatal flaw that
I see here and that is you never consider the other interests groups
views. We rant and rave here over the whys' wherefore's and whatnot's and
never consider that out there in the big world very few care what is going on
here because it is not seen as being relevant to the larger problems of
the decline of the nation, race relations, crime and the general crazyness of
this late 20th century world. It is not that space is not relevant, it is
just that not one poster that I have seen on this net addresses their
issues within the context of the larger world.

This is why I started this thread about "plans and lack therof". This is
what Von Braun, Tsivosky, Goddard, Ley and the rest had. They had a plan,
they had a vision of what the future could be that was positive, technical
but human. Space station is about humans in space. Very few people in this
world give a hoot about many of the plans that are put forth on sci.space
for the utilization of this or the blast off of that, BUT I submit to you
readers that the manned space program has changed more lives for the better
than any self help program or psychciatrist (sp) in the world. I have seen
and met and work with students that from the age of 3 years old have dedicated
their lives to working in space. There is something to this if it can
bring forth this level of dedication, motivation, and effort that lasts from
babyhood to adulthood. This is why Space Station Freedom is ultimately
important. It is a symbol of what can be done, it is a beacon to light
the way for the children like myself and many many others who chose this
path from our earliest thoughts.

It is a faith that we will do good up there. What is that faith based upon?
Besides the technical promise that is held out, there is the fact that in
every new frontier that mankind has ever embarked upon, the sum total has
been the improvment of life for all mankind.

Take a look around, get off the terminal for a day or two and read the
papers. What other endevaour in this world holds out for a postive
future where individual freedom remains? Where you can do your best and
make a large contribution?

There are 100 billion stars in this galaxy. We are so arrogant to think that
all of the answers are here on the earth. From the earliest days of mankind
we have learned by looking upward not backward.

This is why I post about a plan an a lack thereof. With one exception by
a poster that is not a regular, all I have heard is the regurgitation of
peoples pet plans with no consideration on how these plans fit in with the
larger realm of mankind. Give Allen credit, at least his plan does add to
what is a larger plan. Even Nicks plan has a place in the overall pie. BUT
neither of you consider what you are doing leads to within the context
of HOW this will benefit all mankind.

Leaders of an earlier age did this. Edison wanted light to banish the night
and free mankind from being a slave to the night. Tesla's dream was to
power the machines that would free mankind from drugery and manual labor.
Mr. Boeing and Lindberg and all the avaition pioneers saw clearly how the
aeroplane would revolutionize travel and trade for the world (and make a buck
too!) Von Braun and the others of his ilk were the same. The central problem
of this day and this age and this net is that no one is putting forth the
dream and then going forth and working on it. If Allen would stop twisting
things so much he would be worthy of great admiration. I have changed my
mind regarding SSTO during our debates.

Come on out there, think about these things and post something. What about
me? Well..... just wait and see.

Dennis, University of Alabama in Huntsville

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

Date: 20 Mar 93 12:05:53 GMT
From: Del Cotter <[e-mail]>
Subject: How to cool Venus
Newsgroups: sci.space

Some references:

Martyn J Fogg
'The Terraforming of Venus' J. Brit. Interplanetary Soc. _40_ 551-564

Stephen L Gillet
'Second Planet - Second Earth' Analog _104(12)_ 64-78 (1984)
'The Postdiluvian World'       Analog _105(11)_ 40-58 (1985)

(Translated from Fogg's referencese, I *think* these are the Dec 84 and
Nov 85 issues; ICBW)

Fogg's paper is still, IMO, a classic for those interested in doing
something with our useless sister planet.  It wouldn't be easy, mind.
Here's how Fogg sees it:

Year
    0    Project begins; algae injected into Venus atmosphere

    Importation of 1e17 kg of H2O from Iapetus (for algae)

    Mining of H2 in Uranus atmosphere begins (to fix the
    excess O2 produced by photosynthesis and make oceans)

     Asteroid Psyche moved into Venus orbit
      Construction of Dyson motor begins

  500    Dyson motor in operation

13200    Venus spun up to 24 hour day by Dyson motor
    Dyson motor dismantled

15200    Algae have reduced all 4.6e20 kg of Venus' CO2
    H2 importation ceases at 4.2e19 kg

    Sunshade constructed at Sun-Venus L1 point
    Rainout begins

16200    Venus cooled to 300K; 75% of Sunshade dismantled
    Terraforming begins in earnest

16500    Venus terraformed; total energy expenditure 1e30 J

--
 ',' ' ',','  |                                                  |  ',' ' ',','
   ', ,','    |       Del Cotter       [e-mail]      |    ', ,','
     ','      |                                                  |      ','

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

Date: Sat, 20 Mar 1993 17:18:50 GMT
From: Gary Coffman <ke4zv!gary>
Subject: How to cool Venus
Newsgroups: sci.space

In article <[e-mail]> Callec Dradja <[e-mail]> writes:
>In article <[e-mail]>, TMakinen says:
>>
>>This removing of carbon from primordial atmosphere as a byproduct of the
>>chemical processes driven by living organisms is a minor cause to present-
>>day lack of carbon dioxide in our atmosphere. The main deposit of carbon
>>dioxide in our planet lies in the carbonate rocks which contain some
>>100,000 times more CO2 than the atmosphere. CO2 is recycled through
>>plate tectonics and volcanism.
>
>What you say about the carbonate rocks makes sense but what I do not
>understand is why the Earth has carbonate rocks and Venus does not.
>Are carbonate rocks created by some sort of geological process? Both
>Earth and Venus seem to be geologically active so why the lack of
>carbonate rocks on venus?

Likely it's because the surface temperature is so high that the CO2
is baked out of the rocks before they can be buried by tectonic
action.

[delete]
>I would also like to address the solution that one person offered
>of using nuclear devices to blast the atmosphere out into space. This
>idea sort of frightens me because such large forces seem sort of
>difficult to control. I would be afraid that too much of the atmosphere
>might be blown away. In addition, maybe my thinking is wrong but it seems
>to me that in the future, if we really start using the resources of
>our solarsystem, there may one day be a shortage of oxygen. It makes
>more sense to keep it there in one relatively accessible place than to
>blast it out into space where it will disperse and be much harder to
>recover.

Rather than too much of the atmosphere being blown away, I suspect
the reverse would be the problem. It would take some *really* big
nuclear bombs to blow off 90% of the atmosphere. Certainly bigger
than anything we have a clue about building. Maybe some sort of
anti-matter bomb would work.

It seems to me that the atmosphere problem of Venus is a tougher
nut to crack than terraforming about any other minor body in the
solar system. Even giving the Moon a breathable, albeit temporary
in geologic terms, atmosphere looks like an easier job.

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     |

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

Date: 20 Mar 1993 10:02:33 -0500
From: Pat <[e-mail]>
Subject: Just a little tap (was Re: Galileo HGA)
Newsgroups: sci.space

 Oh, the galileo engineering team deserves the Edison Prize for
their work in coping with a basically disasterous event.
The DSN improvements and the new coding schemes are terrific,
but I think 30% is a number placed on for PR purposes, not
in any way a real number.   The imaging people get hosed,
the Fields people do okay,  the Probe people do good.

pat

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

Date: 20 Mar 1993 09:55:08 -0500
From: Pat <[e-mail]>
Subject: Magellan Update - 03/19/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>the remaining moves will be complete by March 31st.  Significant amounts
>of excess paper have been eliminated, and unneeded equipment has been
>surplused.

What do the above two clauses really mean?   What's unneeded equipment,
and what's excess paper?  was the team drowning in management paperwork
before?  or were you just more warehouse space.

pat

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

Date: 20 Mar 1993 21:01 UT
From: Ron Baalke <[e-mail]>
Subject: Magellan Update - 03/19/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary

In article <[e-mail]>, [e-mail] (Pat) writes...
>In article <[e-mail]> [e-mail] (Ron Baalke) writes:
>>the remaining moves will be complete by March 31st.  Significant amounts
>>of excess paper have been eliminated, and unneeded equipment has been
>>surplused.
>
>What do the above two clauses really mean?   What's unneeded equipment,
>and what's excess paper?  was the team drowning in management paperwork
>before?  or were you just more warehouse space.

It just means that the Magellan team has been cut back.  The
equipment left behind by the previous team members (mainly computers)
is being surplused.
     ___    _____     ___
    /_ /|  /____/ \  /_ /|     Ron Baalke         | [e-mail]
    | | | |  __ \ /| | | |     Jet Propulsion Lab |
 ___| | | | |__) |/  | | |__   M/S 525-3684 Telos | Don't ever take a fence
/___| | | |  ___/    | |/__ /| Pasadena, CA 91109 | down until you know the
|_____|/  |_|/       |_____|/                     | reason it was put up.

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

Date: Sat, 20 Mar 1993 17:31:42 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Predicting gravity wave quantization & Cosmic Noise
Newsgroups: sci.space,sci.astro,sci.physics,alt.sci.planetary

In article <[e-mail]> [e-mail] (Cameron Randale Bass) writes:
>
>     This points to another question that I had if my first two
>     were answered.  I'll pose it anyway.  Let's say a gravitational
>     wave comes through and whacks a spacecraft (ripples in space, and
>     all that).  For simplicity, we'll think of wavefront normal to the
>     line connecting the spacecraft and the earth.   Presumably the radio
>     connection then sees a doppler shift due to the 'oscillation'.
>     Why does the oscillation not identically nullify the doppler shift
>     all the way back to the receiver owing to the effect of the wave
>     on the radio signal?  Is that the case, and is that why they're
>     using three craft?

Let's look at it another way. The gravity wave deforms the fabric of
spacetime. This lengthens the path from Earth to the spacecraft as
the wave passes into the beam. This "stretching" of space lengthens
the radio waves, IE lowers their frequency. This will happen to both
the wave going to the spacecraft, and the wave returning from the
spacecraft for a double downward frequency shift.

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     |

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

Date: Sat, 20 Mar 1993 19:15:30 GMT
From: "Richard A. Schumacher" <[e-mail]>
Subject: SR-71 Maiden Science Flight
Newsgroups: sci.space

>>     The SR-71 can take measurements across a wider area at that
>>     height, it can also take measurments in day, night and terminator
>>     between day/night all in 1 flight, i.e. within a short period of
>>     time. This wide sample space may provide useful information beyond
>>     what a balloon's sample space would be.

>But what if you used TWO balloons, or maybe three.  That would solve the
>sample space problem at much lower cost.

Or would it? Then you'd need two widely separated ground support crews,
or three, and would face a greater chance of not getting some of your
(possibly expensive) equipment back. Evidently the researchers who have
signed on to SR-71 think they're getting a deal. They could just as well
have chosen balloons if they'd wanted them.

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

Date: Sat, 20 Mar 1993 17:06:16 GMT
From: Gary Coffman <ke4zv!gary>
Subject: SSTO: A Spaceship for the rest of us
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>>Henry says that DC-Y will mass 800,000 pounds, and that 700,000
>>pounds of that will be fuel. He further says that LOX is $5 a
>>pound and represents the bulk of the weight. So ignoring the
>>hydrogen's extra handling costs, fuel for a DC-Y flight costs
>>$3.5 million dollars...
>
>Gary, how do you ever run a successful business if you can't read any
>better than this? :-)

I don't work from memory when the numbers are *my* dollars. :-)

>First, and relatively minor, I never quoted any figure for DC-Y's mass.
>If you re-read my writeup, you'll find that it uses that number purely
>as an arbitrary example, when discussing the implications of mass ratios.

Ok, but if the 20,000 pound payload objective is to be met, you make a
good case that the mass is going to have to be in that neighborhood.

>Second, and more serious, I quoted LOX at five **CENTS** a pound, not
>five dollars a pound.

Yeah, this is where memory failure entered, I remembered "a few dollars
a pound" and "oxygen....5....", but you were discussing different things.

So we're down to $35,000 dollars for fuel. That sounds too cheap. Certainly
I can't buy welding gas for $0.05 a pound, it's around $0.55 a pound for
compressed gas, I'd assume LOX would be higher and LH higher still, and the
bulk discount shouldn't be *that* big. Where'd you get that number?

Gary
--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     |

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

Date: Sat, 20 Mar 1993 17:28:26 GMT
From: Douglas R Fils <[e-mail]>
Subject: tether II
Newsgroups: sci.space

sci.space,
    I found the following file concerning a tether experiment
to take place soon (if it hasn't already been done).  Can someone
provide more information or perhaps even results?

Thanks all
Doug




------------included text-----------------
NASA to Launch Satellite Into Space on 12 1/2-Mile Tether

NASA to Launch Satellite Into Space on 12 1/2-Mile Tether
  Cape Canaveral, Fla. -- NASA and the U.S. Air Force plan to cast a
satellite into space on a 12 1/2-mile cord Thursday night less than a year
after failing with the experiment.
  This time the project, dubbed Tether Two, is simpler and 38 times cheaper,
the agencies said.
  The Air Force will launch an unmanned Delta rocket with a military
navigation satellite and NASA's tag-along tether experiment. This 12 1/2-mile
tether -- just three-hundredths of an inch thick -- is wound around a spool.
One end of the polyethylene fiber cord is tied to a 57-pound aluminum box.
  Everything is mounted on the rocket's second stage, which will be left in
an elliptical orbit 115 miles by 448 miles high after boosting the Air
Force's navigation satellite, according to the Associated Press.
  The plan is to pop the spring-loaded box off the spent booster an hour
after the 10:55 p.m. launch. As it shoots away, the box should cause the
tether to unwind.
  Instruments on board will record the speed and tension of the tether and
send the data to Earth.
  When the tether is almost fully extended -- if it gets that far -- a brake
will slow the unreeling. The cord and box will swing like a pendulum below
the booster, and a guillotine-type mechanism will cut the tether. The rope
and box will burn up as they enter the atmosphere three hours into the
flight.
  All for $10 million.
  Compare that with the $379 million tether contraption that flew on the
Space Shuttle Atlantis last summer and required seven astronauts for
operation and, as it turned out, for help. The ball on the end of the
electricity-generating cord never got more than 840 feet from the shuttle
because of a protruding bolt that caused the line to jam.
  NASA has yet to schedule another shuttle mission with the first experiment,
Italy's Tethered Satellite. It is being shipped back to Italy next week.
  "A number of people felt mine should have gone first," Joe Carroll, an
entrepreneur from Chula Vista, Calif. who designed the tether deployer flying
on the Delta, told AP. He proposed the experiment in 1983.
  "Obviously if we succeed, tethers are more real," Carroll said. "If two
entirely different tether systems both have problems, then it sheds a
negative pall over the whole range of proposed applications."
  Potential applications for tethers include using them to drop experiment-
laden capsules from space stations to Earth, generate space station
electricity, create artificial gravity, fly atmospheric instruments at
altitudes too high for scientific balloons yet too low for free-flying
satellites, and change spacecraft orbits.
  Unlike the tethered satellite, this tether system has no moving reel
mechanisms or bolts and therefore nothing to jam. There's also no generating
electricity, no human interaction, no bringing the tether and box back
intact, and no leaving the cord up there to get tangled around a spacecraft.

--

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

Date: 20 Mar 1993 09:57:27 -0500
From: Pat <[e-mail]>
Subject: Water Simulations (Was Re: Response to various attacks on SSF)
Newsgroups: sci.space

Ron,
    the instruments are in easily serviceable units,  but
some of the repairs I don't think were planned, such as the the
Gyro changeouts and the Solar array replacement.   The
work may go smoothly, the work on DSCS? or was it a DSP
went much better then hoped.

pat

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

Date: Sat, 20 Mar 1993 14:24:06 GMT
From: Michael Moroney <[e-mail]>
Subject: Why use AC at 20kHz for SSF Power?
Newsgroups: sci.space

For whatever it's worth:

The vast majority of electronics gear run off voltages other than 120V.  So
they convert the voltage to the level used, often 12 or 5V.  In the olden
days this was done with a big power transformer, which would get quite upset
at 20kHz.  However, most modern gear doesn't use them anymore, they convert
the incoming power to a high frequency (often 20kHz), run it through a small
"power transformer" that's often a toroid, then rectify to DC as usual.
This has the advantage of lighter weight and better filtering with smaller
components, often with 120V/240V capability thrown in for sales anywhere.

How is this done?  Well the first thing done to the power when received is
to rectify it to DC.  It is chopped with an oscillator.

What does this mean?  For much stuff it doesn't matter what the frequency is,
it can run off DC if needed.  And much of the stuff is generating the
20kHz frequency anyway, so you'll have to deal with the noise problem from
them.

I suppose there could be a minor advantage.  One could eliminate the first
rectifier/filter/chopper on the 120V side of the toroid xformer and feed the
120V 20kHz directly to the toroid, and save a few parts count, if the
device was to be used *only* on 20kHz power.

-Mike

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

Date: Sat, 20 Mar 1993 19:29:34 GMT
From: "Richard A. Schumacher" <[e-mail]>
Subject: Why use AC at 20kHz for SSF Power?
Newsgroups: sci.space

In <[e-mail]> [e-mail] (Michael Moroney) writes:

>What does this mean?  For much stuff it doesn't matter what the frequency is,
>it can run off DC if needed.  And much of the stuff is generating the
>20kHz frequency anyway, so you'll have to deal with the noise problem from
>them.

With the gigantic complication that, instead of being relatively
easily confined inside the small metal box of the convertor, you'd
then have high voltage AC running all over the station. Can you say
"antennas"? Can you say "EMI/RFI"? THE first rule of noise suppression
is, Do It At The Source.


Indeed, hindsight is golden, but Holy Fudd: with all the fun NASA
has had with technology development as an innate part of system
development (i.e., shuttle), this really should have been a no-brainer.

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

Date: Sat, 20 Mar 1993 17:21:52 GMT
From: Gary Coffman <ke4zv!gary>
Subject: will dust cool Venus?
Newsgroups: sci.space

In article <[e-mail]> Callec Dradja <[e-mail]> writes:
>In my original article, I talked about several ideas regarding
>the terraforming of Venus. I saw some responses to the problem
>of the dense Venusian atmosphere but no one responded to my proposal
>of using dust to cool Venus. Will this proposal of putting dust
>in orbit around Venus in order to cool the planet work? I am afraid
>that over time, the dust will heat up and begin radiating infrared
>light which may slightly help warm Venus. I don't think, however,
>that this effect would be significant. Should I assume that because
>no one responded to the dust proposal, that everyone thinks that
>it will work?

I *suspect* without doing any math that the dust would be quickly
swept away by light pressure and the solar wind.

Gary

--
Gary Coffman KE4ZV          |    You make it,     | gatech!wa4mei!ke4zv!gary
Destructive Testing Systems |    we break it.     | uunet!rsiatl!ke4zv!gary
534 Shannon Way             |    Guaranteed!      | emory!kd4nc!ke4zv!gary
Lawrenceville, GA 30244     |                     |

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End of Space Digest Volume 16 : Issue 346
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