Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V16_2/V16NO239.TXT

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

Date: Mon,  1 Mar 93 05:15:15
From: Space Digest maintainer <[e-mail]>
Reply-To: [e-mail]
Subject: Space Digest V16 #239
To: Space Digest Readers
Precedence: bulk


Space Digest                Mon,  1 Mar 93       Volume 16 : Issue 239

Today's Topics:
                           Aurora (rumors)
                      Easy Replumbing for Fred?
                          military aircraft
                  Nobody cares about Fred? (2 msgs)
                     Refueling in orbit (2 msgs)
    Reliable Source says Freedom Dead, Freedom II to be developed
                Robert Goddard or liquid-fuel rockets
                 Sky & Telescope Weekly News Bulletin
                    Spaceflight for under $1,000?
                        Spy Sats (Was: Are La
                  SSF GIF Files on ames.arc.nasa.gov
           SSF Resupply (Was Re: Nobody cares about Fred?)
                          The Future of Fred
                      X-15 / Shuttle performance

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

Date: 26 Feb 1993 13:51:58 GMT
From: Paul Michael Keller <[e-mail]>
Subject: Aurora (rumors)
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Dean Adams) writes:
>[e-mail] writes:
> >This Aurora seems really dangerous for people (near-collisions),
>Are you kidding??  There has been ONE report of a near miss.
>That makes it "really dangerous"?  Come on!  Get real...

Sorry, folks but I'll have to throw some cold water on this one.  The origin of
this report is a very brief article which appeared late last summer in AvLeak
(AW&ST, Aug. 24, p. 24).  The report was by a UAL 747 eastbound out of LAX
which had a head-on encounter with something in the vicinity of Edwards AFB.
Although I do not have that issue on my desk right now, the gist of that re-
port was that it appeared to be some sort of supersonic drone which got away.
I believe it was described as "F-16 sized, or smaller."

Paul Keller
[e-mail]

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

Date: Fri, 26 Feb 1993 13:57:14 GMT
From: Thomas Clarke <[e-mail]>
Subject: Easy Replumbing for Fred?
Newsgroups: sci.space

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.

I really wish that I could believe NASA fell into the second category.
That NASA could show engineering brillance at imnprovisation.  But
sadly, recent histroy does not support this.  Ill made  mirrors,
reinforcing bolts that jam cable spools, not to mention o-rings, all
point to something fundamentally wrong in the way NASA does things.
This is why I write letters to my political representatives recommending
(with a heavy heart) that they cancel Fred and redirect space funding
to hopefully more fruitful avenues such as SSTO and Russian collaboration.

P.S.  The best improvisation to date seems to be done by the astronauts
in orbit.  It would probably be a good thing to get them up in a
Winnebago at the soonest opportunity, even a leased Mir, and away
from the problems on the ground.
--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
[phone], FAX: [phone], [e-mail]

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

Date: Thu, 25 Feb 93 20:58:36 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: military aircraft
Newsgroups: sci.space

>The A-12 was intended to replace the aging A-6.  It ran into
>management problems, overran budget, and has been cancelled.  Aurora
>is the (rumoured only) replacement for the SR-71 Recce aircraft, which
>has (once again, rumoured only) reportedly been flying for a number of
>years now.

    The writer probably confused "Aurora" and "Avenger". However, I'm
    not sure that the A-12 Avenger II was even supersonic, much less
    designed for Mach 4.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: Thu, 25 Feb 93 20:57:25 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Nobody cares about Fred?
Newsgroups: sci.space

>You seem to be assuming fueling as a dedicated mission to arrive at
>the 'no difference in cost' conclusion.  Either that, or you are
>assuming that an entire removable thruster module is not going to
>weigh any more or take up any more space than a large tank of fuel to
>fill it.  I don't think either of those are good assumptions, hence
>replacing thruster modules rather than refueling them costs more
>(because you have t lift more weight and volume to accomplish the
>refueling in the replacement case, and hence can't carry something
>else that will have to be brought up or accomplished on another
>mission).

    I've read this paragraph a few times and still can't figure out
    what you're trying to say. >:-(

    What I was trying to say, however, is that a refueling mission and
    a module replacement mission are both likely to be dedicated flights.
    Therefore, I don't see how a module replacement is more expensive
    than a refueling mission. At least not if both missions are Shuttle
    based. Allen said something, I think, about replacement method needing
    a bunch of extra modules (one on Fred, one on ground in overhaul).
    This is true, but offset by the need to develop orbital refueling
    technology for the alternative, and refueling will still need some
    type of fuel carrier, pumps, etc. Shuttle is coming home anyway, so
    I don't see how carrying back empty modules is particularly expensive.

>And if the Shuttle is grounded and the station is forced into
>free-drift for lack of replacement thruster modules (which is the same
>thing as saying that it ran out of fuel), then where are you?  It all
>comes down to just how much money and opportunity cost is a small
>incremental change in safety worth.  It is this failure at rational
>risk analysis that has earned parts of NASA the poor reputation for
>performance and cost effectiveness that they have.

    Its clear there are arguments both for and against the module
    swap-out method. In my previous post, even I said I would like
    to see a backup refueling capability. However to keep costs down
    (ahem, har har) NASA could chose only one method. As I said, and
    you ignored, I cannot fault NASA for choosing the safer of the
    two methods, which swap-out unquestionably is.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: 25 Feb 1993 21:32:37 GMT
From: Doug Mohney <[e-mail]>
Subject: Nobody cares about Fred?
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Gary Coffman) writes:

> The orginal alternative to off the shelf exchangeable
>hydrazine thruster packs used newly developed H2/O2 thrusters operating
>off of electrolyzed water from Shuttle fuel cells. 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.

Oh no, Gary, that can't be right!  After all, NASA would never suggest anything
that innovative and have Congress de-fund it, being the evil deadweight
bureaucrats that NASA leadership is!

After all, you are suggesting that pennywise is not pound foolish, and we both
know <nudge-nudge> that anyone given $2.32 and some bubble gum can build a
better station then Freedom, with just as much capability and functionality.

Gary, I have no alternative but to assume you're lying. :-)



    Software engineering? That's like military intelligence, isn't it?
  -- >                  [e-mail]                        < --

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

Date: Thu, 25 Feb 93 20:56:44 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: Refueling in orbit
Newsgroups: sci.space

>In article <[e-mail]> [e-mail] (Brian Stuart Thorn) w
r
>ites:
>>>The Centaur which could have benefitted from on-orbit refueling
>>>never had a test program to achieve this mission...
>>
>>    Centaur is an application, but how many payloads would require
>>    this application? Just one: Galileo...
>
>Why do you assume that there will never be another use for it?  I'm
>sure the Cassini people, to take one example, would love to be able to
>go direct to Saturn rather than batting around the inner solar system
>for a while first.  And I expect the Pluto Fast Flyby people wouldn't
>mind some extra delta-vee either.

     Galileo: That's one.
     Cassini: That's two.
     Pluto Fast Flyby: Not on that budget, they don't. Hell, they are
     considering, for cost reasons, using Proton instead of Titan IV,
     never mind two Titan-class launches (Centaur and Centaur-refueler.)

>That doesn't even consider potential missions that aren't even being
>*planned* because they appear to be impractical within the limitations
>of current boosters.

     It doesn't seem likely to me that in 1994 NASA will decide to launch
     a Mars Sample Return Mission in 1995. More reasonably, a big mission
     like that will be years in the making (say, 5 at least) leaving
     considerable time for developing cryo refueling capabilities. When

     we need it, we'll develop it. Hasn't that *always* been the way?
     They didn't mate Titan and Centaur until Voyager needed it.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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

Date: Fri, 26 Feb 1993 11:59:45 GMT
From: "Allen W. Sherzer" <[e-mail]>
Subject: Refueling in orbit
Newsgroups: sci.space

In article <[e-mail]> [e-mail] (Brian Stuart Thorn) writes:

>     It doesn't seem likely to me that in 1994 NASA will decide to launch
>     a Mars Sample Return Mission in 1995. More reasonably, a big mission
>     like that will be years in the making (say, 5 at least) leaving
>     considerable time for developing cryo refueling capabilities. When
>     we need it, we'll develop it. Hasn't that *always* been the way?

It doesn't work that way. nobody is going to use it or plan to use it
unless its there.

Suppose you are the PI of a multi-billion $$ Mars sample return mission.
Are you going to risk your entire project on a technology which hasn't
been done yet and which may or may not work?

Not bloody likely.

   Allen

--
+---------------------------------------------------------------------------+
| Allen W. Sherzer | "A great man is one who does nothing but leaves        |
|  [e-mail]     |  nothing undone"                                       |
+----------------------109 DAYS TO FIRST FLIGHT OF DCX----------------------+

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

Date: 26 Feb 93 06:12:00 GMT
From: [e-mail]
Subject: Reliable Source says Freedom Dead, Freedom II to be developed
Newsgroups: sci.space

In article <[e-mail]>, [e-mail] (Allen W. Sherzer) writes...
>In article <[e-mail]> [e-mail] writes:
>
>>>But Dennis, this is pretty much what NASA planned to do with Freedom
>>>before the micromanagers in Congress insisted on greater integration
>>>to minimize this problem. NASA disagreed saying on orbit instalation
>>>wasn't a problem.
>
>>This is what was scaled way back by having the truss built in larger
>>pieces on the ground and then launched in the cargo bay.
>
>Exactly. NASA said the redesign wasn't needed and Congress mandated it
>because they didn't agree. Again Dennis you find yourself in agreement
>with Congress and disagreeing with NASA. Good job.
>

Well Allen if you read Space News this week you will see that it is the
redesign that has gotten them in a lot of trouble.  I can see this as
the inevitiable result of Congress trying to design a space station
instead of the engineers.  Although I will surprise you and agree that
the whole situation could have been handled better.  It would be
interesting to go back and take a closer look at the original truss and
really see actually how much EVA it would take to buld it.  I will
bet you that the action of JSC and MacDac was a quick fix reaction to
get Congress of their backs, that ended up in their words as problem.
This was reported in this weeks Space News.  No I do not agree with congress
on this one Allen but I do agree with you that the whole EVA issue should
have never been downplayed as it was after Challenger.

>>This is also the
>>case with the refueling that has been talked about here. They are simply
>>changing them out instead of doing all of the on orbit work to refuel.  In
>>addition, the Resupply module is also a quick changout item instead of
>>having astronauts work to bring new supplies in.
>
>Um... the Russians refuel in orbit with zero eva or even astronaut time
>spent. It is done with an automatic system.
>

How about giving some details on this worderful system.  Since you have
a resource such as the Shuttle that has the carry back capability that it
has, it seems to me that the replaceable units are a good idea. It
obviously takes less time to implement, which will save a dime or two
of operations costs.

>Changing a thruster module will indeed take quite a bit of astronaut
>time both in the Shuttle and on Fred. If you where concerned with reducing
>person hours for maintenance (thus freeing up valuable astronaut time for
>experiments) you would oppose the present system. That is, assuming you
>agree that we can develop a system as good as the Russian system.
>
>Bottom line Dennis is the things you think save EVA time actually cost
>more.

How about some comparative numbers on this Allen instead of a blanket
statement with no facts? I will gladly agree with you IF you can do this.
It seems to me just common sense that by using the Canadaarm you could
chage out the module without ANY EVA time.  That is my understanding of
how it will work. Any correction to this?

>
>>With an ET design you have none of the above with the added problems of
>>completely having to build up the interior from scratch.
>
>So it takes a few years. Big deal. A minor issue compared with the years
>and years Fred has taken and will take to achieve ANY operational capability.
>

While you are taking a few years, nothing gets done and you suck up a lot
of dollar doing things on orbit that are better done on the gound.  There
is a principle here.  It is like when I worked on a production floor in
a computer manufacturing operation.  I could fix many boards in an hour, I
also have the skill to rework and test them faster than a rework person could.
BUT the time differential was not enough to make it cost effective for me
to do so.  The rework person was paid much less than I to do a job I was
better at, BUT the math proved that the overall system productivity was
greater when she did the work.

This is a systems engineering approach to manfacture, and this seems to
be your weakness in that you do not consider, or at least fully consider
the implications of your actions at a system level.

>At any rate, these are not problems. If you examine the SSI External Tank
>Study you will find lots of alternatives which solve these problems for
>far less than we are spending now.

Yea that is a STUDY.  All of the original studies for space station were
cheap too.  It is when you get into the hard part of detail design and
bending metal that you find out that you can study your heart out and
still not know how much your system will cost till you build it.  Boeing
built here in Huntsville a flight hab module three years ago just to find
out what it really took to build one and how much it will actually cost.
Funny that it is work package I that is on time an in budget.

>
>>>Which is why the growth in logistics shuttle flights was called 'alarming'
>>>in an internal NASA briefing in early 89.
>
>>That alarm was silenced during the design of station three years ago.
>
>Granted but it was solved by Congress when they mandated the 89 redesign
>over the objections of Freedom managers. I'm gratified to see you agreeing
>with Congress on this Dennis.
>

As the Space News article shows, congresses direction is responsible for
a quick fix redesign that is now 1 billion dollars over budget.  Funny how
good congress is at doing that to a program.  It seems that in order to
placate congress the boys in Houston went off the deep end. Chalk up another
wonderful mess brought to you by a congress trying to design a Space Station.

>>To bring this up now that the problem has been largely solved is meaningless.
>
>Not quite. You see, the problems with Freedom by and large aren't technical,
>they're cultural.
>
>I know I have called NASA managers incompetent in the past but that
>isn't quite the correct word. The real problem is that these people
>work in an environment where the people with responsibility have no
>authority and the people with authority don't care if anything ever
>gets built (so long as funding continues). Each center wants to grab
>whatever they can and stop the other centers from getting anything.
>
>This is why McDac Space Systems is $1 billion over budget on Fred yet
>is performing awesomly on DCX. Nobody could ever expect a system like
>this to ever work.
>
>That culture still exist Dennis and IT is the problem.
>

You know something Allen, I am going to surprise you here and largely agree
with you.  There are cultural problems but not for the reasons that you
state.  The ones who are the problem in NASA are usually those with little
technical savvy and who have their jobs through politics and or through
deft manipulation of the bureacracy. These people exist in all companies,
organizations and governments.  The are like a ball and chain to the ones
working for them and over them, your main problem is that you characterize
all of NASA as being this way.  This is untrue.

For an example of this look at JPL.  Those guys are to be admired.  The
got off track out there.  The were pushing billion dollar babies that became
so large that they simply could not fly throught he politics that it takes
to get a mission in the air.  What has happened.  I have seen a complet
change in the attitude of the JPL folks.  They are now doing the discovery
missions many of which are truly awesome and relatively inexpensive too.
There are many other things that JPL is doing not only to survive but to
prosper.  Point is they got off track and through the trauma of losing
CRAF they turned their act around and now are better than ever in my
opinion.

Hopefully this drastic medicine will not be needed for Station.  Maybe some
major management overhauls such as are happening will suffice.  This is
what got Marshall back on track after Challenger. Even Marshall has
signed on to doing theings better by the redesign of AXAF that is saving
a bundle and will still produce a great observatory.


>>I will be meeting with some sources in the next few days that are working
>>on plans to save about 2-5 billion dollars over the life of station in...
>
>Dime a dozen Dennis. Hell, I have friends at the Reston Program office
>who do that to amuse themselves on coffee breaks. Anybody who thinks
>a little about it can save $20 billion or so in life cycle costs without
>breaking a sweat.
>
>Getting the change implemented, THAT'S the hard part.
>
>  Allen

This last statment is why none of your proposals will be taken or considered
to be implemented. You must be diplomatic and not call the folks that you
want to get to change something a bunch of fools and here is what I'm going
to tell you in order that you may fix all of your problems.  That is how
you are perceived Allen.  There is much that can be done behind the scenes
in such a way that does not allow you to gloat at how much you were able to
get NASA to change, but will allow the more important job of change
accomplished.  That is the difference between us.  Sometimes being on the
outside as a rabblerouser is a plus but you simply have lost the ability to
effect positive change when you implicitly lable anyone who disagrees
with you an idiot.  No you don't do it directly but you do by the tone and
tenor of your approach.  We are all working for a common goal. It never helps
when you reach out and bite the ones that you want to get to listen to you.

Think about it.

Dennis, University of Alabama in Huntsville

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

Date: Fri, 26 Feb 1993 00:45:23 GMT
From: Ben Mock <[e-mail]>
Subject: Robert Goddard or liquid-fuel rockets
Newsgroups: sci.space

Does anyone have any information on Robbert Goddard and liquid-fueled
rockets?  I'm doing a research paper on Goddard so any info on his life
and his beliefs will be apreciated.  Also if anyone has any information on
where I can find information on Goddard will be very helpful.  Thanx.
                            Ben

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

Date: Fri, 26 Feb 1993 04:30:48 GMT
From: [e-mail]
Subject: Sky & Telescope Weekly News Bulletin
Newsgroups: sci.space

In article <[e-mail]>,
[e-mail] (Henry A Worth) writes:

>>  SKY & TELESCOPE NEWS BULLETIN -- February 20, 1993
>>  MORE HUBBLE WOES
>>  The Hubble Space Telescope (HST) suffered its third gyroscope failure,
>>  out of six on board, leaving the spacecraft's pointing-control system
>>  without any backup.
[remainder of S&T article deleted]

>    Does the gyro-loss safe mode put Hubble into a slow stablization spin,
> or in the case of complete gyro loss does it become just a matter of time
> (and flapping solarpanels) until Hubble begins to tumble and has to be
> written off?
[Remainder of Henry Worth's concerns deleted]

No.  There is a whole separate set of safemode gyros which are sufficient
to keep HST in sunpoint safemode (with the back end toward the sun so the
solar arrays get fully illuminated) indefinitely.  The safemode gyros are
not sensitive enough to provide the degree of pointing accuracy necessary
for science operations which is why one more gyro loss puts us out of the
science business until December (or whenever the service mission happens).

As for the concern about grapling HST if the primary gyro system has
failed, the safemode system is more than adequate for this task.  One
little subtlety of capture is that HST has to be rotated such that the
solar arrays are in shadow for the shuttle arm to have access to the
graple point.  The on-board keep alive software will automatically
rotate HST back to a sun-on-panels attitude after 30 minutes to prevent
battery discharge.  So the astronauts have to get HST grapled and on
shuttle power within 30 minutes.

But the fear of HST tumbling out of control simply due to another gyro
loss is unfounded.  About the worst possible case would be for the
astronauts to have one solar panel off and have a shuttle emergency
which required them to jettison HST.  Ugly thought.

-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: 25 Feb 1993 14:46 CST
From: "Guillot, Burt J." <[e-mail]>
Subject: Spaceflight for under $1,000?
Newsgroups: sci.space

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"?

-----------------------------------------------------------------------
Regards,
B.J. Guillot ... Houston, Texas USA           I don't believe in coffee

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

Date: 25 Feb 93 08:17:00 GMT
From: Roland Dobbins <[e-mail]>
Subject: Spy Sats (Was: Are La
Newsgroups: sci.space

DA>
DA>Newsgroups: sci.space
DA>From: [e-mail] (Dean Adams)
DA>Subject: Re: Spy Sats (Was: Are La
DA>Message-ID: <[e-mail]>
DA>Date: Tue, 23 Feb 93 11:37:53 GMT
DA>
DA>In article <[e-mail]> roland.dobbins@the-matr
DA>>DA>That report has been around a while...  DoD's GROUND based trac
DA>>DA>were certainly used and perhaps even one of their airborne plat
DA>>DA>it may just be the press jumping to conclusions to think any sa
DA>>DA>involved.  KH-11 orbits are not all that much higher than the s
DA>>DA>would make an intercept pretty tight, and besides the optics ar
DA>>
DA>>KH-11 is neither the latest nor the greatest "real-time" platform
DA>>
DA>
DA>The ADVANCED KH-11 is... we currently have 2-3 of them up.
DA>
DA>OR, are you talking about Lacrosse or Aurora?
DA>

Yes, among others . . .

Although those two are primarily ELINT/SIGINT.
---
 . Orator V1.13  .  [Windows Qwk Reader Unregistered Evaluation Copy]


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

Date: 15 Feb 93 18:34:52 GMT
From: Ralph Buttigieg <[e-mail]>
Subject: SSF GIF Files on ames.arc.nasa.gov
Newsgroups: sci.space

Original to: [e-mail]
 [e-mail] (Ken Sheppardson) wrote:


 k> Last week I posted a GIF file of Space Station Freedom
 k> to alt.binaries.pictures.misc. I've put this and another
 k> GIF closeup of the station on ames.arc.nasa.gov. The
 k> two files are:

 k>     pub/SPACE/GIF/ssf-pmc.gif
 k>     pub/SPACE/GIF/ssf-closeup.gif

 Is it possible to put them on the new JPL BBS? I don't have FTP access
 but ring JPL monthly.

 ta
 Ralph

--- Maximus 2.01wb
 * Origin: Vulcan's World-Sydney Australia 02 635-1204 (3:713/635)

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

Date: 26 Feb 93 06:34:00 GMT
From: [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 Cof

[stuff deleted]

>Let's see, we are looking at one to two flights a year dedicated to
>replacing thrusters. That's roughly 50 flights over the life of the
>station. Half could be eliminated with refueling so we are looking
>at a savings of over $12 billion by refueling in space.
>
>Are you actually saying that saving $12 BILLION isn't a good reason to
>incur that upfront expense for something you say is simple to do?
>
>  Allen
>

Na I would say that it is Sherzernomics at work again.  You are assuming
that there will be missions devoted to this one task (Not True).  You are
also assuming a freight value charge that even trucking companies do not
use.  When you have a Shuttle working at anthing less than absolute
capacity on lauch you have deadhead. Well the thrusters could be charged
off to deadhead miles and so your 12 billion number goes out the window.
How can we do this Allen derides? Well the fuel and the tanks go up
anyway for refueling, and the structure for it goes up anyway so what is
the big deal about sending up another few thousand pounds in the form of
the thrusters.  It would matter if this would bump another payload but this
is not the case.  Most trucks on the road run with lower than max
payloads.  They are thrilled to have extra weight added. It adds to the
profit margin. You entire assumption is based upon the unfounded premise
that there must be dedicated missions for this effort. Without that you
actually save money by utilizing the capabilities of the system more fully.

Dennis, University of Alabama in Huntsville

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

Date: Fri, 26 Feb 1993 14:17:38 GMT
From: Thomas Clarke <[e-mail]>
Subject: The Future of Fred
Newsgroups: sci.space

[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?


--
Thomas Clarke
Institute for Simulation and Training, University of Central FL
12424 Research Parkway, Suite 300, Orlando, FL 32826
[phone], FAX: [phone], [e-mail]

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

Date: Thu, 25 Feb 93 20:58:01 PST
From: Brian Stuart Thorn <[e-mail]>
Subject: X-15 / Shuttle performance
Newsgroups: sci.space

>I didn't realize the percentage of "Space" X-15 fligts were so low.
>But the basic concept still stands.  That A "Research" vehicle
>undergoing a "Dynamic test routine"  was able to maintain an
>average flight level higher then a "Operational"  shuttle system.
>And that said research vehicle was able to achieve regular routine
>access to space.  Granted tehy are two entirely difficult vehicles,
>but it si only lately, 33 some years after the x-15 flew that
>the STS is able to achieve a flight rate vaguely like the x-15.
>Sortie rates are very important from an operations viewpoint,
>and the shuttle has had a great deal of difficulty achieving
>a reasonable sorty rate.
>
>pat
>

   Well this is definitely a trap to fall in, comparing X-15 and
   Shuttle, but...

   Vehicle    Years Service:  Flights:   Total Crew:
   ---------  --------------  ---------  -----------
   X-15       10 (1959-1968)  199        199
   SOYUZ      27 (1967-1993)  68         153
   SHUTTLE    13 (1981-1993)  53         294

   These are rough figures. I may be off a few on the total crews,
   but these are pretty close. Total crew includes repeated flights
   by the same person.

   Frankly, I think Shuttle to Soyuz is a better comparison.

-------------------------------------------------------------------------
                                     "Who knows... all this might just be
Brian S. Thorn                     an elaborate simulation running inside
[e-mail]        a little device sitting on someone's table."
                                      -Captain Picard, 'Ship in a Bottle'
-------------------------------------------------------------------------

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End of Space Digest Volume 16 : Issue 239
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