Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_6/V13_648.TXT

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Subject: SPACE Digest V13 #648

SPACE Digest                                     Volume 13 : Issue 648

Today's Topics:
         Re: Self-sustaining infrastructures
            Re: Beanstalk analysis reprise
             Re: * SpaceNews  27-May-91 *
         Re: Self-sustaining infrastructures
Re: The Reasons for a Station? Was Re: Rational next station design...
           Re: Rational next station design process
         Re: Fred cut, AXAF and SIRTF funded
        Re: Magellan: heartbeat loss response
Re: Bootstrapping (Was: Re: S.E.T.I. Who can give me any reasons ...)
         Re: Moonbase movie *Plymouth* to air Sunday?
           Re: Rational next station design process

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

Date: 1 Jun 91 08:23:21 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!spool.mu.edu!agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Self-sustaining infrastructures

In article <[e-mail]> [e-mail] writes:
>* The best cost estimate for a four-man station is $120,000 million
>  (GAO). It is unknown what Mir costs.  A two man station requires the same
>  life support, refuelling, etc. equipment R&D and would not, I think,
>  cost significantly less than a 4-man job.
>
No. First, your cost assumptions are based on ONE data point (Freedom). Also,
you are using the Freedom lifetime costs, and comparing then to my estimated
design and launch costs. The R&D required for a space station depends very
strongly on the design. If I want a design with a minimal supply requirment,
as Freedom does, this WOULD be expensive to develop. However, there exist,
already designed and waiting to be used: Freedom solar pannels, Shuttle
life support system (needs power supply, oxygen and LiO(2) replacements for
long duration use, but will work well given these.), etc... A 2-man station
that made NO effort to push the state of the art would cost MUCH less to
develop than Freedom.

>* You don't show how either your development or operational cost
>  figures are derived.
>
I am still working on these numbers. The operational costs are, as of this
time, the most through. The supply requirements are based on Soviet experience
which says that a Mir+Kvant sized station requires about 10 tonnes/yr of
supplies for life support and station keeping each year. 2 additional flights
are assumed for crew rotation. An OMV, assumed to mass 5 tonnes, would require
1050 kg of fuel to move a 20-tonne satellite through a 100m/s delta-v. 600 kg
woul dbe needed for a 7-tonne satellite. I have assumed an average of 750kg
of OMV fuel/satellite maintained. Satellite maintance is assumed to require
2, 2-man EVA's. This, to be realistic, is about one week's work (including
upkeep on the station.) Based on this, I have assumed that 50 such missions
are possible. Crew rotation used a semi-balistic re-entry capsule (similar
to Apollo.) As a baseline, I have used the British Aerospace "Multi-Role
Capsule" This is a 4-man, 7-tonne capsule. Since I am considering a 2-man
station, there is room for visiting scienticts or whoever... I assume that
an unmanned cargo version of the MRC is possible. This would be the same
type of evolution used with the Soyuz to Progress vehicles. Based on the
system mass of the MRC, a 3-tonne payload is possible if all manned systems
are removed. This requires, including fuel for the OMV, a total of 18 7-tonne
launches each year. I have used the Office of Technology Assessment's
launch cost models. I am trying to pin down the cost of developing and building
MRC's but the numbers given be BA are in "ESA economic units" and I do not
know the conversion. I have used a rough estimate instead.

>* The number of satellites launched into any particular low earth orbit
>  reachable by an OMV is less than 5/year, not 50/year.  The number of
>  those actually benefiting from refueling is probably no more than one per
>  year; other satellites can be redesigned for optimum component/fuel
>  lifetime balance for less than $30 million.
>
While the number of satellites to maintain IS limited, I doubt the 1/year
number (admitidly, there may be no market for 50/year: I am simply producing
the parameters for a POSSIBLE concept.) Similarly, I doubt your "less than
$30 million" figure. What do YOU base your numbers on?

>* You didn't even bother to amortize the $5 billion.
>Over 30 years at 10%/year, this comes to $7,800 million per repair,

I don't know how YOU amortize at 10%/year. But if you require a 10% rate
of return from the investment, this would require charging an extra $10
million/satellite. By the way, I never said ANYTHING about a 30-year lifetime
Based on Soviet experience, a 10 year lifetime is more likely.

                         Frank Crary

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

Date: 2 Jun 91 01:25:32 GMT
From: usc!chaph.usc.edu!aludra.usc.edu![e-mail]  (The Black Sheep)
Subject: Re: Beanstalk analysis reprise

I do believe diamond beanstalks are slightly described in the epilogue
of Arthur C. Clarke's "2061: Odyssey Three"  Anyone care to elaborate on
this?


--
===============================================================================
Ron A Echeverri,        |  "God is a necessary invention. If there is
The Black Sheep            |    no god, we would have to invent Him."
BSAE 1994 Univ of So California |            - Voltaire

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

Date: 27 May 91 14:17:28 GMT
From: mcsun!unido!gmdzi!eana.f3.gmd.dbp.de![e-mail]  (Peter Henne)
Subject: Re: * SpaceNews  27-May-91 *

In article <[e-mail]> [e-mail] (John Magliacane) writes:
> NOAA-12 is currently transmitting APT images on a frequency of 137.50 MHz,
> the same as NOAA-10, with AOS about 45 minutes later.

Ok, this was valid a week ago. Orbit planes of NOAA-10 and NOAA-12 are
almost equal (difference roughly 0.1 deg). Distance of the birds changes
relatively rapid due to their different rev. per day. Its best to
use a good orbital prediction program
                                   Peter

Peter Henne @ GMD -
German Nat. Research-Center f. Comp.-Sience
e-mail: [e-mail]

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

Date: 27 May 91 15:54:34 GMT
From: usc!cs.utexas.edu!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Self-sustaining infrastructures

In article <[e-mail]> [e-mail] (Steve Hix) writes:
>Btw, would it make sense to build Clarke-orbit comsats with gravity-gradient
>stabilization?  Or do they *really* have to have station-holding capability?

I'd have to do the arithmetic to know whether g-g stabilization would work
that far out, but in any case it's largely irrelevant.  For one thing, the
satellites need three-axis stabilization, because their antenna patterns
are carefully shaped to cover only the areas of interest and so they must
not spin on the Earth-satellite axis.  More important, though, the fuel is
used primarily to hold orbital location, not attitude.  The Earth's slightly
lumpy gravitational field and a variety of minor perturbations require a
Clarke-orbit satellite to make regular corrections to stay in a fixed spot
on the orbit.
--
"We're thinking about upgrading from    | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 to SunOS 3.5."              |  [e-mail]  utzoo!henry

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

Date: 27 May 91 16:47:29 GMT
From: news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: The Reasons for a Station? Was Re: Rational next station design...

In article <[e-mail]> [e-mail] (Herman Rubin) writes:
>One year is long term? ...

Well, in the US it is...
--
"We're thinking about upgrading from    | Henry Spencer @ U of Toronto Zoology
SunOS 4.1.1 to SunOS 3.5."              |  [e-mail]  utzoo!henry

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

Date: 28 May 91 00:18:58 GMT
From: agate!lightning.Berkeley.EDU![e-mail]  (Frank Crary)
Subject: Re: Rational next station design process

In article <[e-mail]> [e-mail] (Nick Janow) writes:
>I didn't say that ALL possibilities must be studied in great detail.  What I
>was arguing against is the elimination of other factors and possibilities.  If
>you limit your view to building a space station, you are denying any other
>possibilities for a space program.
>
If you agree that studying ALL the possibilities in detail is impractical, then
you must agree that SOMETHING cannot be studied in detail. As such, SOME
(or many) possibilities and factors must be eliminated.

Also, I at no time said that a space station should be the entire space
program. I said that the worth of a station should be compaired to its
costs, and if the station is worth it, it should be built.

>Here's an example: you have $100 billion to spend over five years and have two
>choices (your limited study approach).  You can develop a small space station
>or you can develop unmanned technology (robotics, AI, teleoperation).
>
>Now, if you go with one of the choices, you can't properly pursue the other;
>that's the way things work.

I do not agree. I have said that the cost of building a station should be
justified by the work it will do. I do not believe that a station could
justify a $100 billion investment, or even $50 billion. As such, you can
assume that the sort of station I am thinking of would NOT prevent work
from being done on other programs, such as telerobotics. I am NOT advocating
a space station which would dominate the NASA budgets to the harm of all
other programs. I am suggesting that it MAY be possible to build and
operate a station, without costing $100 billion and without harming other
programs.

                     Frank Crary

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

Date: 19 May 91 02:11:49 GMT
From: [e-mail]  (Thomas C. Bruno)
Subject: Re: Fred cut, AXAF and SIRTF funded


 In article <[e-mail]> Nick Szabo writes...

. I disagree.  Congress found the price of permanent human presence
. in space too high.  As well it should.   It chose the more
. fruitful route of expanding our knowledge of space.  Congressional
. common sense prevailed over the economic fantasies of NASA and the
. current Administration (which is much more competent in fields other
. than space).  When somebody comes up with reasonably priced space
. habitats, they will be built.  But at $30 billion per person we
. are nowhere near that now.
.
. Yes, I expect NASA to come back with more bizarre astronaut-toy
. proposals while the astronauts remain in charge of NASA.  I hope
. Bush wakes and fires Richard Truly.  I also expect the Congress,
. and hopefully the Senate, to knock them down as soon as they pop
. up.


   I will always remain uneasy about such a stance as long as our most
 expensive endeavors require a friendly human "bonk" to ensure that they
 will fully function.  The human presence in space is much more than an
 expensive liability- and I do not see how "reasonably priced" space habitats
 will come into existence without "unreasonably priced" ones first.  There's
 only so much R&D that can be effected planet-side; even the best Earth-side
 conceived space habitat, no matter how "reasonably priced," will be flinging
 itself to the unknown without a solid set of EXISTING habitat data.  When the
 human race's data from manned space experiences can be measured easily in
 terms of days or months, it is foolish to assume that anything reasonable can
 be fathomed from such a compilation.
   Habitat R&D must be brought into orbit, and not kept in simulations of
 ideal situations.  It must remembered that simply having a permanent human
 presence in space is quintessential "space research" in its own right, without
 which the habitats of the 21st Century will remain in theoretical limbo.  Even
 poor FRED can still provide us with invaluable information that we'll need for
 the future.  The Soviet Union had the right idea.  While America debated over
 the "usefulness" of various space projects, and slowly axed a Space Station/
 Space Truck vision down into a fleet of space shuttles, the Soviets have
 (even in "tin cans") have logged-in more long term man-hours than any other
 nation can hope to equal within the next twenty years.
   Feel free to flame.  Enjoy the upcoming summer.

 Thomas Bruno
 [e-mail]
 Department of Earth, Atmospheric, and Planetary Sciences

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

Date: 20 May 91 23:32:05 GMT
From: bloom-picayune.mit.edu!space.mit.edu![e-mail]  (Peter G. Ford)
Subject: Re: Magellan: heartbeat loss response

In article <[e-mail]>,
[e-mail] (Mark A Wieczorek) writes:
>
>     Has anyone been reading the magellan status reports? I keep coming
> across this term --- Heartbeat loss response --- and have no idea
> of what it is except that is has to be reset once in a while, especially
> during emergencies. Anyone have any ideas?
>
> Mark Wieczorek

Since nobody else has jumped in to answer this one, let me try. I was
analyzing Magellan data when some of those emergencies occurred, and
I came away from JPL with the following general explanation...

The Magellan commands and data system (CDS) contains 4 computers, two for
command control and two for attitude control (AACS). They communicate by
reading and writing into a pair of common RAM memories. Every few seconds,
I forget the exact time, an AACS will re-write a "heartbeat" word, which
is like a two-valued switch. It alternately sets this word on and off.
Each control computer monitors the heartbeat words and, if they don't see
them change periodically, they assume that either the RAM has failed or
the particular AACS is having trouble. This has now happened to Magellan
on several occasions.

Shortly after going into Venus orbit, two things happened at once--some
stray electrical noise caused an AACS to re-boot and a RAM went flakey.
The AACS heartbeat words weren't updated and the control computers noticed
this, but in the intervening time, the spacecraft had rotated away from
where the AACS thought it was pointing. In making automatic star sightings
to try to this figure out, the AACS apparently locked onto the wrong
star and pointed the high-gain antenna away from earth. Hours later,
after another failure, perhaps caused by that bad RAM, the computers
"gave up" and called on low-level recovery software to relocate earth.

A second failure, rather similar to the first, took place a few days
later, while Magellan was still in the low-level mode.

Since then, the CDS computers have been reprogrammed by their degsigners,
the engineers at the Martin Marietta Corp. in Denver, to anticipate the
heartbeat loss and react in a more "sensible" way. There have been a
couple of failures, and the AACS computers have re-booted, but Magellan
has never again completely lost touch with the JPL controllers. The AACS
computers have lost their pointing information, but quickly regained it
and only a few orbits of mapping data have been lost.

________________________
Peter Ford
MIT and Magellan Project

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

Date: 24 May 91 16:24:49 GMT
From: nsc!pyramid!infmx![e-mail]  (David Cortesi)
Subject: Re: Bootstrapping (Was: Re: S.E.T.I. Who can give me any reasons ...)

>In article <[e-mail]> (Don Coolidge) wrote:
>
>>... Given that we're close to resource depletion here...

In article <[e-mail]> (Paul Dietz) replied:
>
>This is completely wrongheaded.  Most mineral resources are present on
>earth in enormous abundance... Currently we are near historic lows for the
>inflation adjusted prices of most nonpetroleum mineral resources ...

As a person who bought bar silver in the early 70's on the "absolute
certainty" that its price could only increase, I would like to
second Paul's remark.

For those who don't know, silver costs essentially the same absolute
number of dollars per ounce now as it did in '69, which means its
real cost is about half what it was then.  And we are shooting just as
much film and filling just as many cavities as we ever did.  The
only interruption in its *downward* price trend was artificial, when
the Hunt boys tried to manipulate the market.

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

Date: 28 May 91 21:53:32 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!sun-barr!newstop!geraldo.Central.Sun.COM!west!grapevine![e-mail]  (Steven Grimm)
Subject: Re: Moonbase movie *Plymouth* to air Sunday?

In <[e-mail]> [e-mail] (Ed Otto) writes:
>The one glaring item that I noticed was the lack of frost forming on the
>spacesuits or the airlock during the explosive compression sequence about
>twenty minutes before the end.

(another spoiler follows)

My housemate pointed out that the whole sequence inside the colony where people
were scurrying for the radiation shelters was silly.  The whole colony, or at
least all the living areas, would have to be shielded; otherwise, wouldn't all
those pretty plants have to be ripped out and replaced after every severe
solar flare?

Overall, it was pretty accurate, I thought.  The plot was pretty predictable,
though, and the characters were a bit wooden.  Too bad.

I'm crossposting this to rec.arts.tv; it seems appropriate.

---
Steven Grimm  [e-mail]   Moderator, comp.{sources,binaries}.atari.st
"We must be brave, and not let them know how frightened we really are."
                 -- OPEN LOOK Graphical User Interface Functional Specification

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

Date: 27 May 91 16:54:50 GMT
From: van-bc!rsoft!mindlink![e-mail]  (Nick Janow)
Subject: Re: Rational next station design process

[e-mail] (Frank Crary) writes:

> If you agree that studying ALL the possibilities in detail is impractical,
> then you must agree that SOMETHING cannot be studied in detail. As such, SOME
> (or many) possibilities and factors must be eliminated.

Yes, we're just disagreeing on which factors/possibilities to eliminate--or not
eliminate.  :-)

> Also, I at no time said that a space station should be the entire space
> program. I said that the worth of a station should be compaired to its costs,
> and if the station is worth it, it should be built.

I have no objection to that.  However, the costs in terms of overall space
development (effects on unmanned research, etc) have to be included.  They
can't simply be left out of the scope of the study.

> I have said that the cost of building a station should be justified by the
> work it will do. I do not believe that a station could justify a $100 billion
> investment, or even $50 billion. As such, you can assume that the sort of
> station I am thinking of would NOT prevent work from being done on other
> programs, such as telerobotics.

Hmmm, are you saying that it's possible to build a space station that will be
inexpensive and provide a reasonable value for the investment, yet won't affect
(compete with) unmanned services?  If you're saying it may be unlikely, but is
worth a minor amount of study, I can agree.

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

End of SPACE Digest V13 #648
*******************