Message-ID: <wZTUDkG00VcJAD104v@andrew.cmu.edu>
Reply-To: space+@Andrew.CMU.EDU
From: space-request+@Andrew.CMU.EDU
To: space+@Andrew.CMU.EDU
Date: Thu,  7 Dec 89 01:32:17 -0500 (EST)
Subject: SPACE Digest V10 #317

SPACE Digest                                     Volume 10 : Issue 317

Today's Topics:
			 Spacecraft survival
			     Re: Buy Mir?
			       Area 51
		Re: Manned vs Unmanned Mission to Mars
		 Voyager 2 Update 12/6/89 (Forwarded)
		       Re: Mars Mission Agenda
		   Geostationary sattelite question
----------------------------------------------------------------------

Date: Wed, 6 Dec 89 18:06:39 EST
From: John Roberts <roberts@cmr.ncsl.nist.gov>
Disclaimer: Opinions expressed are those of the sender
	and do not reflect NIST policy or agreement.
Subject: Spacecraft survival


>From: mnetor!utzoo!henry@uunet.uu.net  (Henry Spencer)
>Subject: Re: Manned vs Unmanned Mission to Mars

>In article <49170@bbn.COM> ncramer@labs-n.bbn.com (Nichael Cramer) writes:
>>But this is, of course, exactly the point.  Voyager's *overall* mission
>>can, and did, survive problems like this.

>The point is, this was more luck than planning.  Similar failures can kill,
>and have killed, entire missions.  Voyager was lucky, period.  This should
>not be extrapolated to some magic ability of unmanned missions to deal with
>any unplanned problem that arises -- look at TVSat 1 for a counterexample.
>(And a good one, since it was the same sort of problem that could be -- and
>was! -- fixed with a few kicks aboard Mir.)

This is also a good example of the importance of proper design techniques
and adequate ground support. The Voyager spacecraft were built with
considerable redundancy. They are far more "controllable" than minimal
mission requirements call for. In particular, control by means of a
computer with writable program memory makes recovery from mishaps far
more plausible than for a less adaptable device. A proven technology was
chosen, with extensive testing of components and assemblies. (I don't know
whether wide design margins were used, but that's also a good idea.)

Voyager is programmed with routines that allow it to recover from a
variety of failures. I believe it controls its attitude by reference
to star patterns, and can generally find Earth again if its antenna
gets out of alignment. On the way to Neptune, Voyager 2 had a backup
mission control program. If it did not receive a message from Earth every
few days, it would assume that its receiver had failed, and carry out
a good "general-purpose" encounter mission. Since the receiver did not
fail, it was possible to modify the main program to concentrate on 
interesting objects that were discovered at a greater distance.

Equally important were the abilities of the ground controllers. It was
human effort that solved the problems of the stuck gears, the degradation
of the platform control, the lost memory bit, and the receiver failure.
Voyager did not have the intelligence to deal with these problems itself,
but the ability to reprogram its functions made recovery possible.

I read a paper describing the processing of a proposed program modification.
After computer simulation, the program goes through an extensive review and
authorization process by humans. It is finally broadcast along with an extensive
error detection/correction code, and a positive acknowledgement must be
received from the spacecraft. It would appear that the lessons learned from
the loss of contact with the Viking lander may have had a lot to do with
the continued success of the Voyager missions.

The failure of the Phobos probes illustrates the problems that can arise
when these methodologies are not followed. The first probe was lost when
an incorrect instruction was transmitted. The second probe may have been
lost partly because it could not recover alignment with Earth. Presumably
the Soviets have now learned the hard way, as we had to. 

Designers of inexpensive spacecraft, take heed! A little forethought can
greatly increase the chances of a successful mission.

                              John Roberts
                              roberts@cmr.ncsl.nist.gov

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

Date: 7 Dec 89 03:27:20 GMT
From: psuvm!mrw104@psuvax1.cs.psu.edu
Subject: Re: Buy Mir?

In article <957@zorch.SF-Bay.ORG>, scott@zorch.SF-Bay.ORG (Scott Hazen Mueller)
says:
>
>1)  The US space station is expected to cost, what, $14 billion?
>
>2)  The USSR is said to be bracing to face an especially hard winter this
>year.
>
>3)  US-USSR joint space missions are generally considered a "good idea".
>
>So, why not pay $5-7 billion and purchase a half share of Mir?  The USSR
>gets hard currency with which to purchase supplies, we get use of a space
>station for half or less of the cost of building our own, and the technology-
>transfer-scare and military use types get to grind their teeth.  :-)
>
>Ok, I know it sounds dumb.  Flames will be discarded, but I'm interested in
>serious comments.
That's not dumb at all- it's a great idea. Reminds me of a story I heard once
(I don't know if it's true) about the navy in revolutionary times. When
war with England looked inevitable, and the Colonies had a wimpy fleet, some
one suggested that we rent the French fleet. :)

*****************************************************************************
Mike Williams
mrw104@psuvm.bitnet

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

Date: 2 Dec 89 01:53:00 GMT
From: pikes!udenva!isis!scicom!paranet!f428.n104.z1.FIDONET.ORG!Michael.Corbin@boulder.colorado.edu  (Michael Corbin)
Subject: Area 51

Since this discussion got over here somehow, I thought that I 
would invite anyone with any interest in this ongoing subject to 
request ParaNet's daily digest.  I have posted here previously 
about ParaNet and will not go into detail other than to say that 
ParaNet is a research and news gathering international 
organization studying the UFO phenomena.  Anyone wishing to get 
on the mailing list is encouraged to request it from infopara- 
request.alphacdc.com.

Thanks,

Mike

P.S.  We are a serious organization.  No flames!

--  
Michael Corbin - via FidoNet node 1:104/422
UUCP: !scicom!paranet!User_Name
INTERNET: Michael.Corbin@f428.n104.z1.FIDONET.ORG

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

Date: 6 Dec 89 15:37:33 GMT
From: mentor.cc.purdue.edu!l.cc.purdue.edu!cik@purdue.edu  (Herman Rubin)
Subject: Re: Manned vs Unmanned Mission to Mars

In article <3037@uceng.UC.EDU>, dmocsny@uceng.UC.EDU (daniel mocsny) writes:
> In article <1989Dec4.175603.24244@utzoo.uucp>, henry@utzoo.uucp (Henry Spencer) writes:

			.....................

> > As has been mentioned before, nobody uses robots to explore Antarctica,
> > even though supporting humans there is decidedly expensive.
> 
> A more meaningful analogy is between space and undersea exploration,
> where the life-support costs are similar. From what I have read, the
> trend in undersea work is clearly away from manned submersibles and
> toward tele- and auto-bots, even though transportation costs are
> small compared to spaceflight. 

			.............................

I do not see this as being more meaningful, except that in deep undersea work,
EVA is essentially impossible.  Also, on earth, including deep-sea work, the
maximum communication delay time is 1/7 second, and even this provides some
problems.  Experiments on teleoperation with the < 3 second delay for the
distance of the moon show problems.  For Mars, there is a minimum delay of
more that 5 minutes, which means no really interactive teleoperations.  I
understand that the attempt to develop reliable Mars rover robuts is as yet
unsuccessful.

Waldos with essentially human operation have been around for years, and
have been used for such things as handling radioactives.  But the nearly
instantaneous response time means that no programming is required, and
this is not possible at interplanetary distances.
-- 
Herman Rubin, Dept. of Statistics, Purdue Univ., West Lafayette IN47907
Phone: (317)494-6054
hrubin@l.cc.purdue.edu (Internet, bitnet, UUCP)

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

Date: 6 Dec 89 17:15:14 GMT
From: cs.utexas.edu!usc!henry.jpl.nasa.gov!elroy.jpl.nasa.gov!forsight!jato!mars.jpl.nasa.gov!baalke@tut.cis.ohio-state.edu  (Ron Baalke)
Subject: Voyager 2 Update 12/6/89 (Forwarded)


                       Voyager 2 Update
                       December 6, 1989

Up to four more active ice volcanoes on Neptune's moon Triton
were discovered in snapshots taken by Voyager 2, which found the
planet itself is swept by 1,500 mph winds--the fastest yet seen
in the solar system.
 
Because the spacecraft photographed at least two and
possibly five of the geyser-like volcanoes erupting on only a
portion of Triton, "chances are that there are a dozen of these
things going off globally" at any time, said Torrence Johnson, a
planetary scientist at NASA's Jet Propulsion Laboratory.
 
Detection of more such volcanoes--which spew nitrogen
ice and gas--was announced Tuesday during a news conference at
the American Geophysical Union's fall meeting.
 
Voyager project scientists Edward Stone said Neptune's
jet-stream winds push frozen clouds of natural gas past the north
edge of the planet's Earth-size, hurricane-like Great Dark Spot
at nearly 1,500 mph.
 
"These are the fastest we've observed," easily exceeding the
previous record winds of 1,100 mph in Saturn's jet stream, Stone
said.  "These almost may be supersonic winds...a wind which is
Mach 1."

 Ron Baalke                       |    baalke@mars.jpl.nasa.gov 
 Jet Propulsion Lab  M/S 301-355  |    baalke@jems.jpl.nasa.gov 
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 6 Dec 89 23:45:00 GMT
From: cs.utexas.edu!jarvis.csri.toronto.edu!utgpu!utzoo!henry@tut.cis.ohio-state.edu  (Henry Spencer)
Subject: Re: Mars Mission Agenda

In article <5589@mentor.cc.purdue.edu> gtz@mentor.cc.purdue.edu (Eric C. Garrison) writes:
>All this talk about which is better, manned or unmanned, is getting worn.  
>Let's try a new game.  Let's suppose that we were designing a mission to Mars.
>We have THREE options: A manned mission, An Unmanned Mission, and a partially
>robotic mission(a mixture of both technologies, for the people who don't want 
>commit either way)
>
>The object is to design a Mars landing/sample return mission, with minimum cost
>and maximum results.  There is a soft limit on the Budget at $200 billion, and
>a hard limit at $400 billion...

With budgets like that, it's easy.  I offer prizes of $10 billion each
to the first five companies who can launch large amounts of payload into
orbit at $200/lb or less, and similar prizes to the first five companies
who can launch large amounts into orbit at $20/lb or less.  (Actually it
might be better to spread the prizes out over the scale, rather than
lumping them at two points, but that's a detail.  Also, definitions of
terms like "large" will be needed.)  No development subsidies of any kind,
just prizes for results.  It'll be the biggest scramble you ever saw.
Forget the joys of space science and the glow of national pride and etc.;
the power of greed beats any of them and all of them when it comes to
getting results.

At $20/lb, we don't *need* to optimize everything for low mass, and we
can launch a repair mission when something breaks, so we don't need to
optimize for reliability either.  If it *has* to work, just send ten of 
them.  Costs will plummet.

Then we can do the unmanned mission, *and* the partially-manned mission,
*and* the manned mission, several times over, for a whole lot less than 
the remaining $100 billion of the soft limit.  Not to mention opening up
space to an enormous range of other activities. 

In fact, we probably don't need to spend that second $100 billion at all.
How much mass do you need in orbit to launch a "big dumb Mars mission"?
That is, no subtlety:  hardware built by construction companies, large
crew, piles of spare parts, massive redundancy and reserves, old technology.
20 million pounds, maybe?  That's $400M.  Private funding can raise that,
if it tries hard -- big university fundraising campaigns reach those ranges.

Tell you what.  We'll split that second $100 billion up into two parts.
The first goes for five $10 billion prizes to the first five companies
which can launch one 100-ton payload a year to 10% of the speed of light.
Use your imagination for the second half.

Why piss around with one-shot Mars missions when you can open the skies
to mankind for less?
-- 
1233 EST, Dec 7, 1972:         |     Henry Spencer at U of Toronto Zoology
last ship sails for the Moon.  | uunet!attcan!utzoo!henry henry@zoo.toronto.edu

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

Date: 6 Dec 89 16:55:51 GMT
From: ccncsu!ncr-fc!santana.FtCollins.NCR.com!genef@boulder.colorado.edu
Subject: Geostationary sattelite question


	Last night, while observing the Moon, a question came to mind
regarding the influence of the Moon's gravity on the station keeping
ability of geostationary sattelites.  What I would like to know is how
much does the sattelite's position vary as it's orbit passes between 
the Earth and Moon each day.  I realize that the effect should not 
permanently alter the position of the sattelite wrt it's station,
but during the time the sattelite is approaching the line between the
Earth and the Moon, it should appear to move away from it's station, 
then as the sattelite moved away from this line it should appear to move 
back to it's station.


				M
				|
				|
				|
	sattelite returing	|	sattelite moving
	to station	     \	|  /	from station
			      \ s /
			       \|/
				E
				
		View from north geographic pole

	Any help with this quiestion will be greatly appreciated.

---------------------------------------------------------------------------
Gene Fusco        | (303) 226-4105 x404 
NCR               | genef@santana!ncr-sd  (or something to that effect)
Fort Collins Co.  | ********* This line intentionally left blank **********

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

End of SPACE Digest V10 #317
*******************