Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v16_2/v16no244.txt

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

Date: Mon,  1 Mar 93 05:47:59
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #244
To: Space Digest Readers
Precedence: bulk


Space Digest                Mon,  1 Mar 93       Volume 16 : Issue 244

Today's Topics:
                        Apollo Moon Missions ?
                         Battery help needed!
                  Beamed power transmission on Mars?
                      Easy Replumbing for Fred?
                        Getting people into S
                    Hopkins Leaks (was Re: Blimps)
                     HST daily reports available
                       Nobody cares about Fred?
             Optical interferometry and coherence length
                       payload return from Fred
                     SOLAR gravity assist?  NOPE.
                    Spaceflight for under $1,000?
       SSF Resupply (Was Re: Nobody cares about Fred?) (2 msgs)
        SSTO vs. Shuttle promises (was Re: Refueling in orbit)
                        Stupid Centaur Tricks
                          The Future of Fred

    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: 26 Feb 93 16:19:30 GMT
From: [e-mail]
Subject: Apollo Moon Missions ?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Tim Thompson)
writes:

>    I am ignorant, I admit it. My memory has failed. Can someone refresh my
> tired brain cells, and tell me (us) which Apollo mission to the Moon was the
> last one? There couldn't have been too many.
>
>    Mille Mercis

It was Apollo 17.  I'm a bit fuzzy myself on the details, but I think that was
launched in December of 1972.  The crew was Eugene Cernan, Harrison Scmidt and
(I'm REALLY guessing this last one) Jack Lousma.

aaron christopher

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

Date: 26 Feb 1993 16:29 EST
From: Pat Loyselle <[e-mail]>
Subject: Battery help needed!
Newsgroups: sci.space,sci.electronics,sci.aeronautics,sci.chem,sci.engr

In article <[e-mail]>, [e-mail] (anthony.r.rizzo) writes...
>
>>
>You might consider using a fuel cell.  NASA already uses a bunch
>of them on the shuttle.  So safety should be less of a problem.

>A fuel cell also might have the appropriate energy density.
>All you'd have to do is provide the fuel cell with the appropriate
>supplies of O2 and H2, in the correct ratio of coarse.  The output
>will be H2O + e.
>
>Tony Rizzo

Fuel cells are great but the problem is, if this experiment is
a get-a-way special there might be volume constraints and with the tankage
for the H2 and O2 you might exceed the volume allowed.  You'd have to do a
trade-off analysis based on the requirements to see if you'd come out
ahead by using fuel cells instead of batteries
                       Pat
----------
Patricia Loyselle                             [e-mail]
NASA Lewis Research Center                    [phone]
Cleveland, Ohio 44135

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

Date: Fri, 26 Feb 1993 19:47:29 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Beamed power transmission on Mars?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Henry A Worth) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman) writes:
>> In article <[e-mail]> [e-mail] (Henry A Worth) writes:
>> >
>> >   It's really a shame certain parties rejected beamed power on Earth as
>> >unsafe without any real study or basis in fact, simply on the basis of
>> >technophobia, while at the same time turning a blind eye toward the very
>> >significant, and quite possibly greater, negative impacts of existing
>> >power sources (better the devil you know then the angel you don't?).
>>
>> Hidden, or not so hidden, technophobia is the reason certain back to
>> the dark ages tree huggers hate SPS systems. But there are reasons
>> for technophiles to disparage the systems as well. Their net efficiency
>> is low, their dependence on untried complex space technologies is high,
>> and their projected costs are astronomical. Doing things because they
>> are neat technical exercises just isn't good enough when the object is
>> as important as bulk power supply for a nation.
>>
>> Gary
>>
>
>   An SPS does not need high efficiency to be effective, just as long as
>the losses don't heat the atomoshere more than the systems they replace.

That's only part of the equation, the ground side. The primary reason
efficiency is important is the way it impacts on orbit costs. The lower
the system efficiency, the larger the spaceborne component has to be.
All that mass, and much of it is complex semiconductor mass, that has
to be placed in orbit, assembled, and operated is what drives SPS costs.
The ground side costs are fairly insignificant. At current system
efficiencies, to get 1000 MWe to the transmission grid on the ground we
need a SPS that's a square 113 km on a side. And that's just to replace
one medium sized terrestrial power plant.

>I'm not saying that SPS is the ultimate answer to Earth's energy problem.
>just that it was unfortunate it, and other alternatives, have been rejected
>with as little study as they have. It's not like we have to build one today
>(that's the root of the problem, our society never plans, it just reacts to
>crisis), some low level on-going research may have addressed some of the
>problems and have more fully quantified the risks and benefits, so that
>a rational, informed decision could have been made. It's not like existing
>systems are without significant negative impacts (can you name a power
>system that dumps significant amounts of radioactive isoptopes into the
>atmosphere in the course of normal operations, resulting in a number of
>lung cancers deaths in the general population every year, and BTW its not
>nuclear), many of the costs related with existing systems are not directly
>reflected at the gas pump or in your monthly power bill, many will end
>up being paid by our children and their children.

Yes I know that coal fired plants are damaging. Their routine radioactive
release is much higher than that of nuclear plants, plus all the other
chemical pollution they produce, and the CO2 they produce. However, there
are terrestrial alternatives to fossil fueled plants whose economics are
much closer to reality than SPS. Nuclear and hydro are already significant
players. IMHO the most promising undeveloped power source is deep dry
geothermal power. Anywhere you dig deep enough there is heat energy waiting
to be tapped. Plus there is ocean thermal, and to a lesser extent direct
solar and wind. The latter two are still looking for adequate storage
methods to make them suitable for baseload needs.

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: Fri, 26 Feb 1993 20:30:14 GMT
From: Gary Coffman <ke4zv!gary>
Subject: Easy Replumbing for Fred?
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Thomas Clarke) writes:
>In article <[e-mail]> [e-mail] (Gary Coffman)
>writes:
>> ... Shuttle offloads it's
>> excess water and Freedom electrolyzes it with solar cell excess power
>> and stores it for stationkeeping burns. *That* was clever, but had too
>> high an upfront cost for Congress to swallow. The thruster development
>> had to be funded, on orbit electrolyzers had to be developed, and water
>> transfer systems designed. Nothing earthshaking, but impossible without
>                                                       ^^^^^^^^^^
>> the upfront funding assured.
>
>In article <[e-mail]> [e-mail] (Gary Coffman)
>writes:
>> ... it would be a simple matter to *add* valving
>> and fittings to a replacement pack to allow on orbit fueling at
>> any time. We aren't locked in to module replacement for the entire
>  ^^^^^^^^
>> 30 year life of the station. If the Shuttle replacement can't
>> convienently recycle thrusters, we can easily modify them not to
>> require recycling.
>
>Me thinks I detect a contradiction.  One type of plumbing modification
>seems to require a large up-front investment, another is done easily
>at any time.

The former requires developing H2/O2 thrusters, on orbit electrolyzers,
and water transfer systems. None of that has been done. The latter only
requires a couple of couplings, some valving, and a pump or pressure driven
transfer system built into the refueling tankage. All of this, aside from
the actual connections to the thruster module, has already been flown on
flight 41-G.

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: 26 Feb 93 09:55:00 GMT
From: Roland Dobbins <[e-mail]>
Subject: Getting people into S
Newsgroups: sci.space

JL>Could that be the vehicle commonly called the flying Bumble Bee, wh
JL>clai to fame in the ordinary world is the vehicle that opened the s
JL>and each episode of the six million dollar man. If I recall correct
JL>was aeronautically considered to be unflyable, but flew anyway and
JL>for a while touted as a great instrument for flight to and from low
JL>orbit. It finally crashed on descent when it touched down and did a
JL>up unfortunately a Helo was in the way and the two collided as the
JL>goes. I think That its prototypes and other s are still on display
JL>the yearly aeronautical show at Edwards airforce base.

As I recall, that particular lifting body was called the HL-10, and it
was most certainly _not_ designed *not* to fly . . . .

---
 . Orator V1.13  .  [Windows Qwk Reader Unregistered Evaluation Copy]


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

Date: Fri, 26 Feb 1993 23:56:12 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: Hopkins Leaks (was Re: Blimps)
Newsgroups: sci.space

[e-mail] (Bill Higgins-- Beam Jockey) writes:

>If we're becoming *completely* pedantic, a "zeppelin" is a rigid
>dirigible airship built by the Count's method; there are other
>possible structures.  Nearly all the rigid airships ever built were
>zeppelins (130 of them?  Or was it 130 German ones and three American
>ones?) The British R100 and R101 are examples of non-zeppelin rigid
>airships.

I'm not sure in what way, but two of the rigids built in the
US, the Akron and Macon, were built differently from the
standard German design, and were judged to be better except
for that little modification the FAA insisted had to be made
to the tail design (which was ultimately responsible for the
loss of both craft, one with heavy loss of life, and the other
with only light loss of life).

>For the following paragraph we have the headline "Hopkins Leaks News
>of Balloon Project."  (Or maybe it's just a trial balloon?)

>> Lighter than air vehicles do indeed have lots of potential for Mars, though the
>> difficulties can't be ignored.  It is however _far_ easier than floating a
>> balloon on Jupiter, something Bill Higgins and I have been puttering around
>> with.

>Not much lately, though-- haven't had the time.  Most weekends I can't
>even *get* to Jupiter...

Doesn't your mom and pop live there?

>Oh, by the way (though this quest failed on sci.aeronautics last
>fall):  We're looking for a textbook that details balloon design!
>Anybody know a good one?

I don't know, but _Sky Ship: The Akron Era_ was a good book on
airships.

I know you'll just _love_ the ZMC-1...

>Moira Higgins on astronomy:          Bill Higgins
>"I can always find Orion.            Fermi National Accelerator Laboratory
>Besides that the Moon                Internet: [e-mail]
>is my only other specialty."         Bitnet:   [e-mail]

I'm doing better than her then, I can even find the sun.

Although it has to come out first. I hear it might if the weather
keeps improving.

--
Phil Fraering         |"...drag them, kicking and screaming,
[e-mail]|into the Century of the Fruitbat." - Terry Pratchett,
                       _Reaper Man_

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

Date: Sat, 27 Feb 1993 01:07:22 GMT
From: [e-mail]
Subject: HST daily reports available
Newsgroups: sci.space

Just read Ken Jenks' offer to post the MSFC morning reports, and
thought that I'd mention that the HST daily activity reports are
available in the newsgroup sci.astro.hubble.  It's a moderated
newsgroup BTW.

We discussed the possibility of crossposting it to sci.space.news
here at the STScI a while back, but there didn't seem to be much
need for that.  If there's anyone out there who would like to see
these daily reports of HST activity but can not get the sci.astro.
hubble newsgroup at your site, please let me know.

The HST reports consist of a listing of the day's science activity
followed by the day's engineering activity.  They're likely to be
fairly uninteresting for non-astronomers.

-Bill Gawne,  Space Telescope Science Institute

 "Forgive him, he is a barbarian, who thinks the customs of his tribe
  are the laws of the universe."                       - G. J. Caesar

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

Date: Sat, 27 Feb 1993 00:36:50 GMT
From: Nick Janow <[e-mail]>
Subject: Nobody cares about Fred?
Newsgroups: sci.space

[e-mail] (tomas o munoz 283-4072) writes:

> You can't just send stuff to orbit and leave it there.  That's  MSFC's
> booster mentality.

It seems a shame to throw away all the energy that has been invested in
bringing that mass out of the gravity well.  If it can't be used immediately,
store it in lightweight containers (a big bag).  It might have a temporary
use as shielding.  It also makes the station more stable.  Someday, when the
station is large enough to reprocess materials, that "trash" will be a
valuable resource.

If nothing else, you can lower the bag of trash on a tether and release it to
boost the station.

--

[e-mail]

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

Date: 27 Feb 93 00:12:47 GMT
From: Tim Thompson <[e-mail]>
Subject: Optical interferometry and coherence length
Newsgroups: sci.astro,sci.space

From [e-mail] (Alejo Hausner):

>   Ok, I understand that radio interferometry means measuring the
> difference in arrival time of the same wavefront at two different
> telescopes.  But doesn't that mean that the wavefront is the same
> wavefront at both places?  I remember when in physics class when they
> were talking about lasers, that light travels in photons, little
> packets.  An ordinary light bulb emits lots of photons, but doesn't
> emit them all in phase.  They leave randomly.  In a laser, one photon
> triggers the emission of lots of other photons, and they are all in
> phase.

>  Starlight is like incandescent bulb light, isn't it?  Its photons
> are all randomly out of phase.  So to do interferometry, the two
> telescopes (or more than two, as you point out) must all be looking at
> the same photon, mustn't they?  If photons aren't very big, then you
> can't space the telescopes too far from each other, otherwise they are
> guaranteed to be looking at different photons.

>  I don't understand how those interferometers do it.

   No, the two different antennae are not sampling the same photon. If my
understanding of QM is reasonable, it is not possible for one photon to share
energy between two different antennae. After all, if the energy is quantized
in photons, and each antenna gets a fraction of a photon, then a photon is really
not a quantum.
   Yes, all of the antennae sample the same wave front, but this is strictly a
classical problem, QM and photons are not required, only Maxwell's equations.
Also, the sources are so far away, that the incident waves are plane waves. It is
not so that sampling the same wavefront means sampling the same photon.
   There are books about radio/optical interferometry, but the level of
sophistication is pretty high, so one must be prepared to work, to understand
the details. Most books on radio astronomy, like Kraus, have chapters on
interferometry as well.

---
------------------------------------------------------------
Timothy J. Thompson, Earth and Space Sciences Division, JPL.
Assistant Administrator, Division Science Computing Network.
Secretary, Los Angeles Astronomical Society.
Member, BOD, Mount Wilson Observatory Association.

INTERnet/BITnet:    [e-mail]
NSI/DECnet:         jplsc8::tim
SCREAMnet:          YO!! TIM!!
GPSnet:             118:10:22.85 W by 34:11:58.27 N

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

Date: 27 Feb 93 00:01:25 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: payload return from Fred
Newsgroups: sci.space

[e-mail] (Henry Spencer) writes:

>Why not?  Most of it will be more useful up there than down here.  And
>a heavier station is *better*, because it reduces the frequency with
>which reboost is needed; even trash is more useful as station ballast
>than as return cargo.

You could also reboost by dumping it into the atmosphere with a tether...

But the main reason you can't just leave stuff in space: someone
might start using it, and we don't want anything that crass to
happen.

>C++ is the best example of second-system| Henry Spencer @ U of Toronto Zoology
>effect since OS/360.                    |  [e-mail]  utzoo!henry
--
Phil Fraering         |"...drag them, kicking and screaming,
[e-mail]|into the Century of the Fruitbat." - Terry Pratchett,
                       _Reaper Man_

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

Date: 27 Feb 93 03:21:29 GMT
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: SOLAR gravity assist?  NOPE.
Newsgroups: sci.space,alt.sci.planetary

In article <[e-mail]>, [e-mail] (Robert M. Unverzagt) writes:
[scathing quantitative denial that the Sun helps you get to Pluto deleted]
>
> In the orbital mechanics world this is called a bi-elliptic
> transfer with interior conjunction.
>
> Can the person who originally claimed a benefit for this please
> explain again?  Maybe I missed something, but this sure sounds
> like what you were talking about.

*Sigh*.   Okay, I seem to have confused everybody.  And I'm probably
confused myself.

I was responding to a suggestion that a solar gravity assist might
help a Pluto  mission.  I found out that a "solar gravity assist,"
contrary to conventional wisdom, is not impossible but just barely
possible. This is intriguing.

Let's forget about going to Pluto, okay?

The core of my question was, "How much delta-V can you pick up by
skimming the surface of the Sun in a gravity-assist manuever?"

                      Barycenter of Solar System
(if you think the world revolves around you, you probably live here)
                               |
             Sun               v
(-------------Cs-------------) .                     to Jupiter --->

        Cs is the center of the Sun, 1 ASCII character = 47,000 km

Again, we are assuming here that the solar system consists only of the
Sun and Jupiter, to keep things simple.

The center of the Sun describes a circle around the barycenter once
every Jovian year.  Therefore it moves 78.2 centimeters per second in
the "solar system rest frame."

The right answer, pointed out by several people, is that when a small
mass "scatters" off a large one, it gains at most twice the speed of
the large one.  As any alleged physicist should have known.  :-(  So
under the most favorable encounter conditions,  our probe can pick up
about 1.56 meters per second, jogging speed.

As Jon Thaler put it in e-mail, "No significant boost is possible,
unless one wants to jog to Pluto."

I claim that this is consistent with intuition, which tells you that
this is a ridiculous way to pick up energy and will not be useful.
But I wasn't sure how to calculate it, so I posted it on the Net,
hoping that it would be read by somebody who can say "bi-elliptic
transfer with interior conjunction" three times real fast.  Like you,
Shag.

Kepler: "Did you know that Tycho,  | Bill Higgins, Beam Jockey
my boss, had an artificial nose?"  | Fermi National Accelerator Laboratory
Galileo: "An artificial nose!      | Bitnet:           [e-mail]
How did he smell?"                 | Internet:       [e-mail]
Kepler: "Terrible!"                | SPAN/Hepnet:           43011::HIGGINS

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

Date: Fri, 26 Feb 1993 23:48:38 GMT
From: [e-mail]
Subject: Spaceflight for under $1,000?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail]
(Guillot, Burt J.) writes:
> In article <[e-mail]>, [e-mail]
> (Henry Spencer) writes...
>>Yes, but those computers and that memory will survive conditions which
>>would turn your PC into a paperweight.  When you can't get home without
>>them, you're a bit fussier about computer quality than the MSDOS crowd
>>usually is.
>
> So what were to happen if John Doe takes his 386 to orbit with 4 megs
> of memory on board with, say, a 40 megabyte hard disk.  Would it
> affect the memory only or the storage of the hard disk as well?  And,
> what is "it"?

Cosmic ray flux.  Various other high speed ions zipping around.  When
they go flying down the crystal lattice of silicon they can do a lot
of damage.  The magnetic storage media, like disks and tape, are less
susceptable to damage by ions but are not immune.  All the VLSI chips
would need to be hardened, and lots of bit checking algorythms included
to guard against ionization effects.

-Bill Gawne,  Space Telescope Science Institute

 "Forgive him, he is a barbarian, who thinks the customs of his tribe
  are the laws of the universe."                       - G. J. Caesar

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

Date: 26 Feb 93 14:40:40
From: Steinn Sigurdsson <[e-mail]>
Subject: SSF Resupply (Was Re: Nobody cares about Fred?)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:

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

   >You are also assuming a freight value charge that even trucking companies
   >do not use.

   How about an experiment to see if that is true. You claim that Shuttle
   shouldn't charge or account for transport costs for the engines since
   there will be deadhead space anyway.

   Now go out and buy a brick. Wrap it in paper and see if you can find
   a company who will ship it to me for free. If they balk, explain to
   them how they have deadhead space and so it doesn't matter. If you
   manage to do this, I'll accept your arguement.

Well, Allen, I could ship you a brick FedEx (or USPO express) (COD of
course ;-) - you will be rather astonished to find that the charge for
shipping the brick will not be the cost of the truck+flight from here
to there, rather they'll charge a marginal cost figuring that not only
can they ship a few other bricks in the same direction at the same
time, but the cost of salary etc for the people involved is a constant
overhead and is amortised over all their activities - even FedEx is
not going to fire a driver if I change my mind and don't ship the
brick.


   Except that with automated refueling we can use $35 million Delta's
   instead of half a billion $$ shuttle flights for refueling.

   If we re-fueled automatically and left the thrusters in place we would
   go from ~50 shuttle flights costing $25 billion and go to ~50 Delta
   flights costing less than $2 billion. A savings of over $23 billion.

Allen, what is the development cost of learning how to do
automatic refuelling and over how many flights will you amortise it?
    Do you propose flying fewer shuttle flights without the
resupply (in which case the marginal cost on the remaining flights
increase) or should NASA redirect those flights to another purpose?
Or should they simply fire 20,000 support staff - in which case what
is the cost of severance (including any welfare support to the
government)?

    You make good points, but your accounting methods are, shall
we say systematically skewed.

|  Steinn Sigurdsson    |I saw two shooting stars last night        |
|  Lick Observatory    |I wished on them but they were only satellites    |
| [e-mail] |Is it wrong to wish on space hardware?        |
| "standard disclaimer"    |I wish, I wish, I wish you'd care - B.B. 1983    |

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

Date: 26 Feb 1993 19:41:18 -0500
From: Pat <[e-mail]>
Subject: SSF Resupply (Was Re: Nobody cares about Fred?)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Allen W. Sherzer) writes:
|In article <[e-mail]> [e-mail] (Gary Coffman) writes:
|
|>I'm saying the reality of SSF upfront funding (remember the chart
|>you so convienently deleted?) is so constrained that we're using
|>hydrazine thrusters because development money wasn't available for
|>H2/O2 thrusters.
|
|Who said anything about H2/O2 thrusters? Even if you wanted to use
|H2, the RL-10 should be just fine.
|

Um. Allen. I think Gary has me confused with you.  I had been talking about
how ET Dregs FUel recovery would be useful for Centaur, and That SSF
management was so inept, that they were using Hydrazine intead of
Methane thrusters.  I think he blended the two ideas together and
shoved the reply at you.  My point was given SSF was going to
produce waste CO2,  you could carry upa  small supply of
Hydrogen,  and convery CO2 -> CH4.  then with the released oxygen
run thrusters.  although, if the fuel cells produce water, you might
crack that electrically, and then have all your feedstocks.

pat.
I agree with you on the concept of automated docking vehicles,
it's just cheaper to make fuels in orbit with leftovers then to
haul them up in tankers.  I'd reserve the tankers for astronaut
consumables, life support spares, experimental gear....

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

Date: 26 Feb 93 21:31:10 -0600
From: Bill Higgins-- Beam Jockey <[e-mail]>
Subject: SSTO vs. Shuttle promises (was Re: Refueling in orbit)
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Steinn Sigurdsson) writes:
>     SSTO fans would do well to re-read the history of some
> modern launchers, including the original Shuttle concept and how
> it evolved. Might make some a little less firm in their cost estimates
> and a little less ready to cut other transport systems before the
> SSTOs have demonstrated operational ability... in particular Allen
> might be astonished to realise that some of his DC claims look
> like they were cut out from a NASA report circa 1971-1974 providing
> STS claims ;-)

Oh, yeah, right, I'm sure Allen's never heard THAT criticism before.

Bill Higgins, Beam Jockey              | "Based on the antiproton
Fermi National Accelerator Laboratory  | decay, I would estimate the
Bitnet:           [e-mail]  | incident occurred
Internet:       [e-mail]  | within the last 4.3 hours."
SPAN/Hepnet:           43011::HIGGINS  |         --Mr. Data

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

Date: 26 Feb 93 23:35:12 GMT
From: "Phil G. Fraering" <[e-mail]>
Subject: Stupid Centaur Tricks
Newsgroups: sci.space

[e-mail] (Dave Michelson) writes:

>Centaur continues to evolve.  AW&ST recently carried an item about General
>Dynamics looking for funding to develop a single engine version of the
>Centaur to increase both payload (marginally) and reliability.  I guess
>price would also decrease slightly as well since it's easier to test and
>verify one engine than two.


I don't understand why it's more reliable to have a single engine than
two engines with a gimballing system that would allow it to function
on one engine.

I guess they're just into newspeak (half the engines, half the chance
of failures!).

Anyone else concur?
--
Phil Fraering         |"...drag them, kicking and screaming,
[e-mail]|into the Century of the Fruitbat." - Terry Pratchett,
                       _Reaper Man_

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

Date: 26 Feb 1993 16:43 CST
From: [e-mail]
Subject: The Future of Fred
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Thomas Clarke) writes...
>[e-mail] writes:
>
>>  the battle for the power system that pitted
>> the DC power system against a 20 khz AC system. This battle was won and
>> is one of the unknown things done to build a good station.
>
>20kHz !?!  DC ?!?  What is this, the year 1880.
>Scientific gear works off 60Hz AC, may 400 Hz AC if it is aircraft,
>or 12V DC if it is portable.
>
>Why would NASA pick something that requires every experimenter
>to have equipment specially made?  No wonder Fred is so expensive.
>
>I suppose the carbon-fiber equipment racks are something other
>than the 19 inch standard relay rack also.
>
>Wait.  Maybe I'm flying off the handle again.  Could the 20kHz just
>be an engineering convenience to be able to use small light transformers
>in power distribution? Might NASA have provided state-of-the-art power
>convertors to give experimenters 60Hz AC?
>
>

Yes you are indeed flying off the handle.  When NASA Lewis first was given
responsiblity for the electrical power system architecture on SSF they came
up with this utterly weird 20Khz AC power distribution systeem.  The theory
was that it was lighter and more efficient.  Well NASA (lets say center b)
wanted to keep the Skylab type DC power system due to its simplicty and
ease of integrating experiments.  Due to congresional pressure center b was
overruled and development work on 20Khz went ahead.  When a demonstration
of the 20Khz system was developed and brownt to center b it was connected in
the same room where the center b proposed 75KVA DC system was already up
and operating. (Actually it had been there in one form or another since
Skylab). Well when the 20Khz system was powered up all of the terminals in
the room locked up! All of their computers also went south from the rich
RFI environment that the system produced.  Needless to say the 20Khz system
soon went the way of the dodo bird.

The moral of the story is keep congress out of the engineering design process.

Also the SSF racks will be common with SpaceLab and SpaceHab, so yes you
can go home and sleep well tonight, knowing that NASA is not completely a
bunch of incompetents.

Dennis, University of Alabama in Huntsville

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

End of Space Digest Volume 16 : Issue 244
------------------------------