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Date: Sat, 27 Mar 93 05:52:02
From: Space Digest maintainer <digests@isu.isunet.edu>
Reply-To: Space-request@isu.isunet.edu
Subject: Space Digest V16 #377
To: Space Digest Readers
Precedence: bulk
Space Digest Sat, 27 Mar 93 Volume 16 : Issue 377
Today's Topics:
25 kg. to Venus, how much would it cost? (2 msgs)
<None>
Alumnium was available in Elizabethan times?
Flight time comparison: Voyager vs. Gallileo
Gravity waves, was: Predicting gravity wave quantization & Cosmic Noise
Idle Question
Magellan Update - 03/22/93
Space Calendar - 03/27/93
Space Posters, and where to get them? (2 msgs)
Uplink/downlink rates (2 msgs)
Why use AC at 20kHz for SSF Power?
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: Sat, 27 Mar 1993 04:51:18 GMT
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: 25 kg. to Venus, how much would it cost?
Newsgroups: sci.space
In article <1993Mar26.170552.21750@ucsu.Colorado.EDU> fcrary@ucsu.Colorado.EDU (Frank Crary) writes:
>... So, adding it all up, a 25 kg
>package to Venus would require about 600 kg IMLEO. The cheap
>way to launch that would be either Pegasus or a Scout. With a
>Scout, you would be well under the vehicle's capacity: You'd be
>more efficient if you sent a larger (~50kg) package, or sent two...
Uh, Frank, what Scout specs are you reading? No Scout has ever been
able to carry 600kg into orbit; the Scout performance charts stop
at 270kg. Pegasus carries *more* payload than Scout, not less; you
can get about 350kg into a very low orbit with a block-1 Pegasus.
(My somewhat-old Pegasus manual predicts 8-20% improvement for
block 2 Pegasus and a further modest improvement for a stretched model,
which I think is the XL they recently committed to building.)
--
All work is one man's work. | Henry Spencer @ U of Toronto Zoology
- Kipling | henry@zoo.toronto.edu utzoo!henry
------------------------------
Date: Sat, 27 Mar 1993 05:03:22 GMT
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: 25 kg. to Venus, how much would it cost?
Newsgroups: sci.space
In article <1993Mar26.171913.19764@aio.jsc.nasa.gov> mancus@sweetpea.jsc.nasa.gov (Keith Mancus) writes:
> Sounds to me like there is a LOT of room for cost improvement on the
>low-mass end, unless the $20M figure is really a loss to the Russians
>and they just don't know it (quite possible)...
It's very hard to say what a "fair price" for a Russian launcher is
(all the more so because Arianespace and the Russian Space Agency
would have different definitions of "fair"!). I have heard it claimed,
at Making Orbit '93 as I recall, that Russian prices would probably
undercut Western ones by at least a factor of 3 even with honest
accounting and Western salaries -- they just need so much less manpower
to build and launch the things, and they have so much larger production
runs for the hardware.
> It seems to me that a cost of < $1M per launch would have a great effect
>on the viability of this type of mission. Granted, there are some benefits
>to scale here, but I don't believe that decreases cost by a factor of 10.
You could be surprised. So much of this business -- in the West -- builds
hardware at very low rates that are very uneconomical. If (admittedly dim)
memory serves, Rockwell offered to build NASA a dozen shuttle orbiters for
the same price as four, if NASA would make a firm commitment that would
allow some investment in streamlined production setups. When there was
talk, some years ago, of a government market guarantee at $500/lb to
low orbit, several of the more innovative companies were pretty sure
that they could make a *bundle* at that rate... which is 5-10 times
lower than current prices. Even the traditional launcher manufacturers
will admit that they could cut costs by a factor of 2-3 if volume
picked up enough to permit volume orders of subassemblies.
The problem is that those low costs aren't going to appear unless someone
first commits to buying a whole bunch of them.
--
All work is one man's work. | Henry Spencer @ U of Toronto Zoology
- Kipling | henry@zoo.toronto.edu utzoo!henry
------------------------------
Date: 26 Mar 93 22:43:21 -0600
From: Bill Higgins-- Beam Jockey <higgins@fnalf.fnal.gov>
Subject: <None>
Newsgroups: sci.space
In article <1993Mar26.223438.19777@news.arc.nasa.gov>, yee@atlas.arc.nasa.gov (Peter Yee) writes:
> EXPLORATION EFFORT SHIFTED TO OFFICE OF SPACE SCIENCE
>
> NASA Administrator Daniel S. Goldin today announced that the activities
> of the Office of Exploration will be absorbed by the Office of Space Science,
> effective immediately.
Well, so much for THAT little empire. It was fun while it lasted.
Bill Higgins | "I shop at the Bob and Ray
Fermi National Accelerator Laboratory | Giant Overstocked Surplus
Bitnet: HIGGINS@FNAL.BITNET | Warehouse in one convenient
Internet: HIGGINS@FNAL.FNAL.GOV | location and save money besides
SPAN/Hepnet: 43011::HIGGINS | being open every evening until 9."
------------------------------
Date: 26 Mar 93 19:17:42 GMT
From: Paul Campbell <taniwha!paul>
Subject: Alumnium was available in Elizabethan times?
Newsgroups: sci.space,sci.materials
In article <1993Mar21.184053.27365@sfu.ca> Leigh Palmer <palmer@sfu.ca> writes:
>According to my Rubber Bible, 63rd ed., Aluminum was first isolated in
>1827 by Wohler. "Aluminium" is available in Elizabethan (II) times, and
>perhaps "alumnium", whatever that is, was available in "elizabethan"
>times, but aluminum was not available in Elizabethan times any more than
>Macintoshes were.
Ahem .... "Aluminum" is the name used by people in the US, "Aluminium" is
the proper chemical name and the name used (and pronounced) by everyone
else in the world. Aluminum is just one of those quaint things about the US
(like inches and writing the date backwards).
Paul
--
Paul Campbell UUCP: ..!mtxinu!taniwha!paul AppleLink: CAMPBELL.P
"Finally after much thought he tied a dollar bill to the top of the tree, it
seemed to fit - after all it was the premier capitalist holiday, besides after
the 'fall' of communism a star didn't seem appropriate anymore ..."
------------------------------
Date: Sat, 27 Mar 93 00:44:49 GMT
From: "Lowell O Specht Jr." <specht@dixie.com>
Subject: Flight time comparison: Voyager vs. Gallileo
Newsgroups: sci.space
vento@mars.lerc.nasa.gov (Dan Vento) writes:
>In article <1993Mar18.000618.1023@ke4zv.uucp>, gary@ke4zv.uucp (Gary
>Coffman) wrote:
>>
>> In article <1o822uINNf90@elroy.jpl.nasa.gov> tjt@scn1.Jpl.Nasa.Gov writes:
>> >the moment, I don't think the U.S. has anything that will launch anything of
>> >Voyager size from earth.
>>
>> Voyagers went up on Titan-Centaurs.
>>
>The current Titan IV-Centaur could probably handle a Voyager type (1800
>Lbs) spacecraft. It really depnds upon where you want to go and on how fast
>you want to get there.
It is a fact that the Titan IV-Centaur is designed to loft a 10,000 lb payload
to low earth orbit. However, to date, a Titan IV-Centaur has yet to be
launched. The space shuttle could also launch a Voyager-type payload depending
on the upperstage used, currently Centaur's are not approved for use with the
shuttle.
--
Regards,
Lowell
******************************************************************************
* Lowell Specht * *
* Marietta, GA USA * *
* home: specht@dixie.com * Go Big Orange! *
* work: g584741@loads1.lasc.lockheed.com * *
******************************************************************************
* My comments are my own and not my employer's. *
******************************************************************************
------------------------------
Date: Sat, 27 Mar 1993 04:45:58 GMT
From: Tom Van Flandern <metares@well.sf.ca.us>
Subject: Gravity waves, was: Predicting gravity wave quantization & Cosmic Noise
Newsgroups: sci.space,sci.astro,sci.physics,alt.sci.planetary
nickh@CS.CMU.EDU (Nick Haines) writes:
> curvature is actually a property of the surface itself. Let's go back to
> the balloon example. Imagine you're an ant on the balloon. How can you
> tell that you're on a curved surface and not a flat one? Simple: you
> measure the area or circumference of a circle. ... if the ratio of the
> circumference to the diameter is pi, the surface is flat. If these are
> less than pi, the surface is positively curved (like a sphere) ...
These are properties of a surface that is curved in another spacial
dimension outside itself. The original question was about whether that
additional dimension is required or not. By requiring another dimension
itself, your example seems to imply that it is also required for the
universe.
> Now suppose your ant civilisation lives on the surface of a cone (not
> near the vertex). You do this experiment. You find these numbers are
> always equal to pi, and you conclude you're living on a flat surface.
Curvature can only exist relative to something non-curved. In your
first example, both balloon dimensions are curved, so there must exist a
third spacial dimension for them to be curved in. In the cone/cylinder
example, only one of the two surface dimensions is curved, so measuring
circumference:diameter ratios is not a test for curvature in a third
dimension.
> The curvature in which we're interested is thus a property of the surface
> (or space) itself, and does not require the concept of an `embedding
> space.' Since we can never observe such a space, why suggest it exists?
Your own examples suggest just the opposite. Since all three spacial
dimensions are supposedly curved, we should be able to detect this by
measuring circumference:diameter or area:diameter or volume:diameter
ratios. If they all came out as expected for flat space over any scale,
however large, that would prove that space was flat. If those measurements
indicated curvature, that would prove the existence of another spacial
dimension.
> Should this go in the FAQ?
Your descriptions still don't answer the original question about
another spacial dimension, at least for me. Essential point: What does it
mean to be "curved" unless there is some standard for "straight"? -|Tom|-
--
Tom Van Flandern / Washington, DC / metares@well.sf.ca.us
Meta Research was founded to foster research into ideas not otherwise
supported because they conflict with mainstream theories in Astronomy.
------------------------------
Date: 26 Mar 1993 21:26:56 -0500
From: Pat <prb@access.digex.com>
Subject: Idle Question
Newsgroups: sci.space
How much weight would an SS-20 or a Pershing 2 lob to 120Nm from
san Marco or Cape York? And could these rockets hit those
altitudes without significant engineering work.
pat
------------------------------
Date: 26 Mar 1993 20:43:13 -0500
From: Pat <prb@access.digex.com>
Subject: Magellan Update - 03/22/93
Newsgroups: sci.space,sci.astro,alt.sci.planetary
In article <1ovckaINN2kl@rave.larc.nasa.gov> S.D.Derry@LaRC.NASA.Gov writes:
>Eric H Seale (seale@possum.den.mmc.com) wrote:
>: say, 60 deg C). One option that I heard being talked about is called (I
>: think) bistatic radar -- Magellan transmits the radar which bounces off
>: the surface and is then received at Arecibo. Even with a low circular
>: orbit, I'm not sure that this buys you much, tho' ...
>
Wow. What kind of power levels are we talking about? The gain
off arecibo must be enormous, but then this will only work on certain
geometric areas. The target and arecibo need to be a equal-angle
trieangle . I doubt one could see very much. THe earth's rotation
would take arecibo off point pretty fast, and given arecibo is
mostly a passive reflector, i doubt it can slew electronically
it's pointing angle much.
Now the VLA, might be able to track over much of the horizon,
but the gain off VLA is lower then arecibo, i imagine.
>Another alternative would be to map small selected areas of high interest
>and play the data back at the current 1200bps rate. By the time that TEX
Is that the engineering data downlink? What's the link speed of the
Transmitters? And could some sort of data compression scheme be run,
just like on Galileo? The SAR returns are essentially large analog
signals, maybe if you applied ADPCM or something else, you could
squeeze out a lot more. Magellan has the computing horsepower right?
>and cycle 5 gravity mapping is complete, the target areas could be selected.
>If they were small enough, and spaced far enough apart, then the data could
>be stored onboard during mapping orbits (only mapping over a small latitude
>range), and played back at slow rate after the target area has been covered.
>Alternatively, portions of the data could be played back between mapping
>passes, but this would make operations a bit more complex.
>
>--
>Steve Derry
><s.d.derry@larc.nasa.gov>
Your right, the target areas of interest are getting smaller.
From my understnading, Maxwell Montes has some black outs right across
the kisser. A goof, by JPL. Shit Happens. The tape recorder
was making a swap over, at just that point in orbit.
Also, certain parts of the poles have not been mapped, plus the few
cycles at solar conjunction. Plus a few areas could really use
some stereo mapping.
My take on it was 1% of the planet still needs mapping, do-able i think
even at 1200 baud, and 65% of the planet still needs stereo mapping.
Implausible, even if the can use coding to get up to 10KBS, but
do-able for the more interesting areas, like the supposed slide zones
and for doing some stereo mapping of the rift zones.
So does anyone from JPL care to comment?
pat
------------------------------
Date: 27 Mar 1993 07:02 UT
From: Ron Baalke <baalke@kelvin.jpl.nasa.gov>
Subject: Space Calendar - 03/27/93
Newsgroups: sci.space,sci.astro,sci.space.shuttle,alt.sci.planetary
The Space Calendar is updated monthly and the latest copy is available
at ames.arc.nasa.gov in the /pub/SPACE/FAQ. Please send any updates or
corrections to Ron Baalke (baalke@kelvin.jpl.nasa.gov). Note that launch
dates are subject to change.
The following people made contributions to this month's calendar:
o Jeff Bloch - Updated ALEXIS launch date (04/22/93).
o Allen Sherzer - Updated DC-X test flight date (June 1993).
o Steven Pietrobon - Updated Ariane launches date for April, June &
July.
=========================
SPACE CALENDAR
March 27, 1993
=========================
* indicates change from last month's calendar
March 1993
* Mar 27 - GPS/SEDS-1 Delta II Launch
Mar 31 - Commercial Experiment Trasporter (Comet) Conestoga Launch
April 1993
* Apr ?? - STS-55, Columbia, Spacelab Germany (SL-D2)
* Apr ?? - Astra 1C Ariane Launch
Apr 06 - 20th Anniversary, Pioneer 11 Launch (Jupiter & Saturn Flyby Mission)
* Apr 07 - STS-56, Discovery, Atmospheric Lab for Applications and Science
(ATLAS-2)
Apr 19 - Venus/Moon Occultation, Visible from North America
Apr 22 - Lyrid Meteor Shower (Maximum: 03:00 UT, Solar Longitude 32.1 degrees)
* Apr 22 - ALEXIS Pegasus Launch
* Apr 26 - First Test Firings of the DC-X
Apr 28 - STS-57, Endeavour, European Retrievable Carrier (EURECA-1R)
May 1993
May ?? - Advanced Photovoltaic Electronics Experiment (APEX) Pegasus Launch
May ?? - Radcal Scout Launch
May ?? - GPS/PMQ Delta II Launch
May 04 - Galileo Enters Asteroid Belt Again
May 04 - Eta Aquarid Meteor Shower (Maximum: 21:00 UT, Solar Lon: 44.5 deg)
May 20 - 15th Anniversary, Pioneer Venus Orbiter Launch
May 21 - Partial Solar Eclipse, Visible from North America & Northern Europe
May 25 - Magellan, Aerobraking Begins?
June 1993
Jun ?? - Temisat Meteor 2 Launch
Jun ?? - UHF-2 Atlas Launch
Jun ?? - NOAA-I Atlas Launch
* Jun ?? - First Test Flight of the DC-X (Unmanned)
* Jun ?? - Hispasat 1B & Insat 2B Ariane Launch
Jun 04 - Lunar Eclipse, Visible from North America
Jun 14 - Sakigake, 2nd Earth Flyby (Japan)
Jun 22 - 15th Anniversary of Charon Discovery (Pluto's Moon) by Christy
Jun 30 - STS-51, Discovery, Advanced Communications Technology Satellite
July 1993
Jul ?? - MSTI-II Scout Launch
* Jul ?? - Galaxy 4 Ariane Launch
Jul 01 - Soyuz Launch (Soviet)
Jul 08 - Soyuz Launch (Soviet)
Jul 14 - Soyuz TM-16 Landing (Soviet)
Jul 21 - Soyuz TM-17 Landing (Soviet)
Jul 28 - S. Delta Aquarid Meteor Shower (Maximum: 19:00 UT,
Solar Longitude 125.8 degrees)
Jul 29 - NASA's 35th Birthday
August 1993
Aug ?? - ETS-VI (Engineering Test Satellite) H2 Launch (Japan)
Aug ?? - GEOS-J Launch
Aug ?? - Landsat 6 Launch
Aug ?? - ORBCOM FDM Pegasus Launch
Aug 09 - Mars Observer, 4th Trajectory Correction Maneuver (TCM-4)
Aug 12 - N. Delta Aquarids Meteor Shower (Maximum: 07:00 UT,
Solar Longitude 139.7 degrees)
Aug 12 - Perseid Meteor Shower (Maximum: 15:00 UT,
Solar Longitude 140.1 degrees)
Aug 24 - Mars Observer, Mars Orbit Insertion (MOI)
Aug 25 - STS-58, Columbia, Spacelab Life Sciences (SLS-2)
Aug 28 - Galileo, Asteroid Ida Flyby
September 1993
Sep ?? - SPOT-3 Ariane Launch
Sep ?? - Tubsat Launch
Sep ?? - Seastar Pegasus Launch
October 1993
Oct ?? - Intelsat 7 F1 Ariane Launch
Oct ?? - SLV-1 Pegasus Launch
Oct ?? - Telstar 4 Atlas Launch
Oct 01 - SeaWIFS Launch
Oct 22 - Orionid Meteor Shower (Maximum: 00:00 UT,
Solar Longitude 208.7 degrees)
November 1993
Nov ?? - Solidaridad/MOP-3 Ariane Launch
Nov 03 - 20th Anniversary, Mariner 10 Launch (Mercury & Venus Flyby Mission)
Nov 03 - S. Taurid Meteor Shower
Nov 04 - Galileo Exits Asteroid Belt
Nov 06 - Mercury Transits Across the Sun, Visible from Asia, Australia, and
the South Pacific
Nov 10 - STS-60, Discovery, SPACEHAB-2
Nov 13 - Partial Solar Eclipse, Visible from Southern Hemisphere
Nov 15 - Wilhelm Herschel's 255th Birthday
Nov 17 - Leonids Meteor Shower (Maximum: 13:00 UT,
Solar Longitude 235.3 degrees)
* Nov 20 - Mars Observer, Mapping Begins
Nov 28-29 - Total Lunar Eclipse, Visible from North America & South America
December 1993
Dec ?? - GOES-I Atlas Launch
Dec ?? - NATO 4B Delta Launch
Dec ?? - TOMS Pegasus Launch
Dec ?? - DirectTv 1 & Thiacom 1 Ariane Launch
Dec ?? - ISTP Wind Delta-2 Launch
Dec ?? - STEP-2 Pegasus Launch
Dec 02 - STS-61, Endeavour, Hubble Space Telescope Repair
Dec 04 - SPEKTR-R Launch (Soviet)
Dec 05 - 20 Anniversary, Pioneer 10 Launch (Jupiter Flyby Mission)
Dec 08 - Mars Observer, Mars Equinox
Dec 14 - Geminids Meteor Shower (Maximum: 00:00 UT,
Solar Longitude 262.1 degrees)
Dec 20 - Mars Observer, Solar Conjunction Begins
Dec 23 - Ursids Meteor Shower (Maximum: 01:00 UT,
Solar Longitude 271.3 degrees)
January 1994
* Jan 03 - Mars Observer, End of Solar Conjunction
Jan 24 - Clementine Titan IIG Launch (Lunar Orbiter, Asteroid Flyby Mission)
February 1994
Feb ?? - SFU Launch
Feb ?? - GMS-5 Launch
Feb 05 - 20th Anniversary, Mariner 10 Venus Flyby
Feb 08 - STS-62, Columbia, U.S. Microgravity Payload (USMP-2)
Feb 15 - Galileo's 430th Birthday
Feb 21 - Clementine, Lunar Orbit Insertion
Feb 25 - 25th Anniversary, Mariner 6 Launch (Mars Flyby Mission)
March 1994
* Mar ?? - TC-2C Launch
* Mar 05 - 15th Anniversary, Voyager 1 Jupiter flyby
* Mar 14 - Albert Einstein's 115th Birthday
* Mar 27 - 25th Anniversary, Mariner 7 Launch (Mars Flyby Mission)
* Mar 29 - 20th Anniversary, Mariner 10, 1st Mercury Flyby
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov
| | | | __ \ /| | | | 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, 27 Mar 93 04:12:49 GMT
From: Ross Borden <rborden@ugly.UVic.CA>
Subject: Space Posters, and where to get them?
Newsgroups: sci.space
In article <1993Mar25.102746.1@aurora.alaska.edu> nsmca@aurora.alaska.edu writes:
>Wiers question, where is a good place to get Space Posters??? I know that many
>people seem to like posters of movie stars and such, beer (sexy girls okay),
>and other such things, I was wondering if someone has any Space Posters and
>where to get them?
>
Try Nova Graphics in Tuscon, AZ. They have some nice prints of spacescapes
by artists like Kim Poor and Alan Bean. They're good quality, but a bit
pricey ($30-$80) because they're all limited editions. Sorry, can't give
you the address, my catalog is at home.
-------------------------------------------------------------------------------
| I shot a man just to watch him die; | Ross Borden |
| I'm going to Disneyland! | rborden@ra.uvic.ca |
-------------------------------------------------------------------------------
------------------------------
Date: 27 Mar 93 01:58:42
From: Jeff Moersch <moersch@theory.TC.Cornell.EDU>
Subject: Space Posters, and where to get them?
Newsgroups: sci.space
In article <1993Mar25.102746.1@aurora.alaska.edu> nsmca@aurora.alaska.edu writes:
> Wiers question, where is a good place to get Space Posters??? I know that many
> people seem to like posters of movie stars and such, beer (sexy girls okay),
> and other such things, I was wondering if someone has any Space Posters and
> where to get them?
>
> ==
> Michael Adams, nsmca@acad3.alaska.edu -- I'm not high, just jacked
If you're interested in really high-quality photographic prints of
space-related things (especially planetary posters), I can recommend
an outfit called "Planetary Arts and Sciences". The owner of this
business is a planetary scientist here at Cornell (and also a friend
of mine) who does this work on the side. He has gone back to the
original digital image data from JPL probes and reprocessed everything
to get color images which look *a lot* better than the usual stuff
available through NASA. The lithographs available from NASA are
usually press release versions that were slapped together in a hurry
for post-flyby news conferences (I know - I've done a few of them!),
whereas these images took several weeks to process/enhance and print.
The company has a toll free number: 1-800-272-1154, and they have a
little glossy catalog that shows what stock they have available.
There may be a small charge for the catalog - I don't remember. They
also have done special request projects (like large, wall-sized
prints) in the before, so if you have an interest in that, you should
ask.
Jeff Moersch
Astronomy and Space Sciences
Cornell University
P.S. Sure this is a plug, but it answers the question... Besides, it
isn't my business!
------------------------------
Date: Sat, 27 Mar 1993 04:42:12 GMT
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Uplink/downlink rates
Newsgroups: sci.space
In article <1993Mar24.164640.2385@head-cfa.harvard.edu> willner@head-cfa.harvard.edu (Steve Willner) writes:
>... The DSN receivers are the best that can be built...
Actually, not so. (I said the same thing a year or two ago, and the radio
astronomy people corrected me!) The DSN receivers are very good, but they
are no longer the absolute best. The latest radio-astronomy ones are better,
although I expect DSN will be upgraded at some point (perhaps soon, given
the Galileo situation).
--
All work is one man's work. | Henry Spencer @ U of Toronto Zoology
- Kipling | henry@zoo.toronto.edu utzoo!henry
------------------------------
Date: 27 Mar 1993 07:00 UT
From: Ron Baalke <baalke@kelvin.jpl.nasa.gov>
Subject: Uplink/downlink rates
Newsgroups: sci.space
In article <C4J6EF.227@zoo.toronto.edu>, henry@zoo.toronto.edu (Henry Spencer) writes...
>although I expect DSN will be upgraded at some point (perhaps soon, given
>the Galileo situation).
The DSN upgrade is in progress and has been proceeding along for
3 or 4 years now.
___ _____ ___
/_ /| /____/ \ /_ /| Ron Baalke | baalke@kelvin.jpl.nasa.gov
| | | | __ \ /| | | | 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: 26 Mar 1993 21:22:20 -0500
From: Pat <prb@access.digex.com>
Subject: Why use AC at 20kHz for SSF Power?
Newsgroups: sci.space
In article <1993Mar24.175055.27927@mksol.dseg.ti.com> mccall@mksol.dseg.ti.com (fred j mccall 575-3539) writes:
>In <1odi0sINNcn4@access.digex.com> prb@access.digex.com (Pat) writes:
>>rather then Fred McCall venting his spleen, a much higher level
|what you most deserve. Go ahead, Pat. Try posting like an adult for
|a while without all the ad hominem attacks on people and insulting
|
Well, Gee Fred. At that point, I had waited something around
2 weeks for someone from a NASA or SSF contractor site to
pick up a defense. McKissock had popped up, thrown a few
vague terms around and then dissappeared. I had wanted
to see something a little more solid, and he seemed
to be hiding from the debate. You may want to defend
your Namesake station, but I wasn't interested in your
speculation. I wanted to hear something from someone
who actually works there. Your insinuations that i was
making up allegations, didn't help the level of
discourse.
|
|No, the paperwork was *not* good because the requirements were bad.
|
Of course, people were so busy working on the paperwork,
no-one ever bothered to see if the requirements were any good.
Were asses kicked for this? were people taken to task for missing
something as simple as a requiremnt for a testbed?
No, Probably not, but if these two centers can't co-ordinate
enough to make a simple test bed and test article conform,
what makes you Fred McCall, think that they will get it together
for one of the largest integration efforts in engineering
history?
|>Ah, the but the paperwork was good, the requirements document
|>had been flowed down into each sub-contract and a full tracability
|>matrix had been done. How could it not work.
|
|Bad requirements. Do you know *anything* about engineering, Pat?
|
Usually the lead requirement is that the system work. Do you know
anything about making Products?
|>How did skylab cope with the DC problems? Skylab was
|>fairly big, it had several arrays, and various power demands.
|>Anyone have the historical background?
|
|Skylab was small and underpowered compared to what SSF was supposed to
|be.
|
Skylab also Flew. Which SSF, looks unlikely to do at any time
this century, unless serious changes occur. The Tiger Team
review, now has it Down to Space Station F.
|>Also, despite what GD may say about DC power complexity, Somehow
|>it does seem to power a large fraction of our industrial equipment,
|>every vehicle in america, and numerous LARGE transportation
|>systems. I would guess that the complexity of the power
|>system of METRO is at least as large as that of SSF.
|
|Gee, and here all this time I thought my vehicle was powered by an
|internal combustion engine, except for a very small electrical system.
|What kind of car are *you* driving, Pat?
|
Last time I checked, all my cars sub-systems used 12VDC.
Let me know when your car starts running on 20KHz.
|>|The AC Alternative
|
|Well gee, Pat, you must live in a real chicken-and-egg dilemma for
|your entire life. It ain't gonna show up in the catalogs until it's
|being used, and you don't want to use it until it shows up in the
|catalogs. Back to the caves, boys!
|
No, But the school of engineering I come from says, that if
you can order it froma catalog, Faster, Cheaper and better
then you can make it custom, you are a FOOL to try to make it custom.
You seem to put the most negative connotations on to the
legitimate engineering criticism I raise. I may prefer, proven
somewhat crude mechanics, but I'll bet you my philosophy will
get more hardware up, then your Gold Plated, Boondogle Charging
let's waste money, the more the merrier philosophy ever would.
|>Actually, i would imagine that 20Khz transformers would not
|>be terribly efficient, the Reactance of these is proportional
|>to frequency. I'd imagine the impedance losses, may make High Frequency
|>Transformers actually imprcatical. DSoes anyone have the idea
|>of the Inductance of a 50 KW transformer coil? assume 208/480 volts,
|>three phase.
|
|Somehow I suspect that the people doing the studies probably looked at
|this issue, and I suspect they used a better tool than "Pat's
|imagination".
|
Then Maybe Dave McKissock, wouldn't mind posting some of these analyses.
I mean, I imagine they were done?
|
|>|
|>|AC System Frequency
|>|
|>|Since it is now clear that AC has many advantages and is the
|
|>I don't know why anyone is worrying about delivery costs,
|>after all, the shuttle flies up with dead head space, and
|>that's free. I mean if they have to haul up the module,
|>why worry about some extra weight, i mean it's marginal
|>cost is only a little hydrogen. :-)
|
|If this were convincing logic, we'd be hauling whatever we pleased to
|orbit, since it would always fit in the "deadhead space". The point,
|Pat, is that if you don't have to lift X pounds of one thing you can
|lift X pounds of something else if you want to.
|
Fred, you must have a poor memory, or a short attention span.
In another thread flame, Dennis wingo was arguing that spare
mass wasted on a fueling flight was ir-relevant because
it could be billed at the marginal cost for extra lift.
He was roundly flamed for that suggestion. I was merely using it
to sarcastically justify a heavier electrical system weight.
|
|>|there isn't a strong size and weight driver, pushing us above
|>|that frequency region. If we're conserned about a manned
|>|vehicle, we should probably move to at least 20 khz to get the
|>|power line noise above the audio region. (That 400 Hz whine
|>|in my airliner stereo head-set is really annoying if I have to
|>|listen for very long).
|>|
|>I've worked in lots of industrial plants with louder things then
|>some power noise. Seriouly, i can't believe this would ever be
|>a major criteria.
|
|Yes, but one would like not to have all that loud racket and vibration
|on a space station. Background noise *better* be a serious criteria,
|since people are going to be stuck in that environment for months at a
|time.
|
They are astronauts. They can take it. It's no worse then the
constant low-level whine emitted by the Net:-)
|>|But how high can we comfortably go? The answer comes from the
|>|DC power processing folks. When we design DC to DC converters
|>|in this power range, readily-available component technologies
|>|for semiconductor switching devices, transformers, capacitors,
|>|etc. limit us to a maximum frequency of about 50kHz. So if we
|>|stay comfortably below that, and continue with our initial
|>|thought to chose something close to 20 kHz, we can expect
|>|to find a good selection of qualified power components and
|>|materials, and a good body of design data, with which to
|>|implement hardware designs.
|>|
|
|>Gee, I look in a lot of electrical industry magazines, and I see
|>a lot of articles on problems caused by DC power processing.
|>A large number of PC's plugged into one room, generate enough
|>non-linear current and harmonic noise to be destroying conductors,
|>transformers and switch gear.
|
|Gee, your point?
|
The article cites the number of qualified components available to do
20KHz power work, and my literature, mostly complains about
problems related to high frequency.
|>Plus, i have to wonder what kind of body of design data exists at
|>50 KW.
|
|>So how does efficiency wise a DC-DC converter stack up against
|>a motor/generator pair. For large power generation i'd imagine
|>it would be a lot more reliable, and able to handle transients a lot
|>better.
|
|One would like to reduce high-inertia rotating equipment to a minimum
|on a space station, Pat. Otherwise, you spend a lot of fuel
|cancelling out spins imparted to the station by rotating equipment.
Given the presence of the alpha-gimbels, the motor generator will
quite nicely complement the torque needed by the main axis of the
station. If anything, it would help reduce the load on the
G&N System, providing a constant spin to these elements.
|And solid state is always more reliable than anything involving moving
|parts, as well as easier to repair/replace. The equipment I used to
Not neccesarily. Depends on the quality of the Electronics,
and the mechanicals.
|work on in the Navy took the 440 3-phase from ship's supply, used a
|motor generator set to get DC (what we called 'quasi-DC', actually),
|then used a solid state inverter set to convert it to high-current DC.
|This was then reconverted to AC elsewhere in the system as needed.
>Would you consider 1/4 Megawatt as 'high power'?
>
Reasonably.
>
>>Does that mean we are looking at 50,000 dollars/watt
>>costs deployed?
>
Did your Naval system, cost $50,000/Watt?
[ Citation List deleted]
>
>
>>Interesting, most of these papers are either NASA reports, or
>>IECEC papers. Kinda a small community.
>
>Well, that sure invalidates everything, doesn't it, Pat?
No, But it sure doesn't show the technology being used by
a large community. Means you have to be your global test bed.
Installed Base, is oftentimes a significant engineering criteria.
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End of Space Digest Volume 16 : Issue 377
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