Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_2/V13_264.TXT

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Subject: SPACE Digest V13 #264

SPACE Digest                                     Volume 13 : Issue 264

Today's Topics:
               Re: Reliability
              Re: SPACE Digest V13 #261
        POTENTIAL GEOMAGNETIC STORM WARNING - 13 MARCH
             Re: Not about space (sorry)
                MANY QUESTIONS

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

Date: Tue, 12 Mar 91 22:29:24 EST
From: John Roberts <[e-mail]>
Disclaimer: Opinions expressed are those of the sender
    and do not reflect NIST policy or agreement.
Subject: Re: Reliability


>Date: 11 Mar 91 22:59:56 GMT
>From: news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
>Subject: Re: Reliability

>In article <[e-mail]> [e-mail] (John Roberts) writes:
>>>peculiar myth within NASA that all possible problems can be anticipated,
>>>and you really can be certain that the thing will work before you launch it.
>>>The universe keeps trying to tell NASA that this is wrong...
>>
>>That last statement sounds a little too broad. Just about everything they
>>launch is chock full of backup systems, and the unmanned devices have both
>>on-board recovery systems and provision for ground-based reconfiguration.

>All of which can handle only expected classes of failures, by and large.

It's generally not practical to be completely prepared for the completely
unexpected. The best one can hope for is to think of as many contingencies
as possible. Of course, it's also the duty of the designers to put priority
on solving the problems deemed most likely to cause trouble.

>On-board recovery systems and provision for reconfiguration are of limited
>help if your thrusters explode when fired continuously... and we very nearly
>sent Galileo up with thrusters that did exactly that.

In a way, we did. Those same thrusters are still in there. They haven't
exploded, however.

>(The thruster problem
>was discovered only because TVSat 1 used the same thrusters, and it fired
>them long and hard in attempts to shake its stuck solar array loose.  Had
>Galileo been launched on schedule, it would have been very lucky to reach
>Jupiter.  TVSat 1 went up during the post-Challenger hiatus.)

And other things that have not received as much publicity. For instance, the
original design would *probably* (> 50%) have failed before or during the
time-critical Jupiter insertion due to radiation-induced computer errors.
An effort was made to greatly increase the radiation hardening, and such
an event is now considered very unlikely.

>On-board recovery systems and provision for reconfiguration are of limited
>use if your solar arrays flap every time you cross from sunlight into
>darkness... last I heard the HST people had given up on ever being able
>to get full compensation for this, as the onboard systems just don't have
>enough crunch.  It would be unfair to also mention the mirror-distortion
>actuators that don't have enough muscle to take the spherical aberration
>out, so I won't :-).

Since you didn't mention it, I won't reply that HST was designed for
repair (quite a bit of it, anyway) by visiting astronauts. :-)  :-)

>On-board recovery systems and provision for reconfiguration didn't save
>Seasat, or the Viking 1 lander, or the attitude-control system on Solar Max
>either.  All of these things deal only with expected classes of problems.
>They can still be blind-sided by something unexpected.

Viking had very poor on-board recovery by modern standards - no command loss
timer or reacquisition software. (Did it even have a low gain antenna?)

The Voyagers were launched before the Viking loss, yet they have these
features, though possibly only in software. (Trivia question: what was
the last US interplanetary probe launched that could not be reprogrammed
from Earth?)

>>If you're thinking of simpler multiple probes, I think that has both good
>>and bad points, and has to be evaluated on the merits of each case...

>Simplicity vs. multiple missions is a complex tradeoff.  But putting all
>your eggs in one basket is foolish whether that basket is simple *or*
>complex, because *failures do happen*.  Complex systems, while often
>better equipped to cope with failures, also are more prone to them.

>"But this *is* the simplified version   | Henry Spencer @ U of Toronto Zoology
>for the general public."     -S. Harris |  [e-mail]  utzoo!henry

To get back to your original comment, what can NASA *do* that's better than
what it's been doing? If they build multiple probes for a multiyear mission,
should they launch all of them at once, and possibly let the same unforeseen
design problem zap all of them? Or should they keep some on Earth, and put
up with the heat about overspending and probes that could have been used
gathering dust in museums?

If there's plenty of money, they can do both - launch probes every year or
two, with nearly duplicate missions, and retargetable in the event of
failures. Voyager came close to that - missions some months apart, plus
one gathering dust.

For the absolute minimum in eggmonobasketing, perhaps in many cases the
best approach is what NASA has apparently done with Magellan, Galileo, etc.:
for each project, build *one* probe for launch, designed to be as resilient
as possible, and do everything you can to keep it alive. If problems start
to come up, begin thinking about what you could have done better. If the
mission fails, do your utmost to find out why it happened (NASA seems very
good at this), then start begging for money for another probe. That way,
when you start construction of the replacement, you know what pitfalls to
avoid, and you can eliminate design problems that have turned up in the
interim. (The thruster problem was known *before* Galileo was launched, but
at that point it was too expensive to make changes other than in the
operational algorithm. These changes do decrease performance somewhat.)
Furthermore, the development of technology is on your side - there may be
new and better ways to do it. In the meantime, you spread your money over
a wide range of projects, so even if on project suffers a major setback,
you still have valuable results coming in from the other projects.

Yes, there is at least one major drawback to this approach - if the one probe
fails, the team put together to control and use it must disband for a number
of years (or at least cut way back on its activity) while the replacement
is being built. The "standard probe" utilization that you have advocated
would help to reduce this interval.
     John Roberts
     [e-mail]

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

Date: Tue, 12 Mar 1991 13:28 EST
From: Kom <[e-mail]>
Subject: Re: SPACE Digest V13 #261
Cc: [e-mail], [e-mail]
X-Vms-Cc: IN%"[e-mail]",IN%"[e-mail]"

signoff space

Hi,

I attempted for several times to sign off from this list.
Would you please remove me from this list manually?

[e-mail]

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

Date:    Tue, 12 Mar 91 19:26:12 MST
From: [e-mail] (CARY OLER)
Subject: POTENTIAL GEOMAGNETIC STORM WARNING - 13 MARCH
X-St-Vmsmail-To: st%"[e-mail]"

                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

                     POTENTIAL GEOMAGNETIC STORM WARNING

                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

                          Issued:  02:00 UT, 13 March

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


ATTENTION:

     A major-storm level positive magnetic excursion has been measured
locally (northerly middle latitude station) and has been associated with
strong radio signal fading and flutter.  Our station has only been able to
catch the latter part of the larger magnetic disturbance.  The magnetometer
was down for routine maintanence until 01:15 UT.  Hence, we only caught the
falling edge of the magnetic disturbance.  However, from the information we
have gathered thus far, the disturbance locally measured over 234 gammas.
The peak occurred sometime shortly before 01:15 UT, judging by the
signature of the disturbance measured.

     We are not yet sure what the cause of this magnetic storm period is,
or if this is a planetary disturbance.  We have reason to believe this is
a planetary disturbance, and until we can verify the information (very
shortly), we have posted this Potential Geomagnetic Storm Warning.  A
bulletin will follow shortly.

     Until the bulletin is released, please be aware of the potential for
geomagnetic storming, possible strong auroral activity, and possible poor
radio conditions.  The bulletin will formalize the conditions occurring so
far and will list the expected conditions.  A major flare alert will also
follow shortly.


                /\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\/\

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

Date: 10 Mar 91 21:20:26 GMT
From: hoptoad![e-mail]  (Tim Maroney)
Subject: Re: Not about space (sorry)

In article <[e-mail]> [e-mail] (John Hyde)
writes:
>I'm writing a term paper for a class, the title of which will be
>something like "Email and Electronic Bulletin Boards:  Present and
>Future Effects on Society."  I would like to make the case that these
>two media have the potential to have as much effect on the world as
>the printing press did.
>
>The movie Star Trek VI was originally going to be done with young
>actors playing the roles of the familiar characters, set at Starfleet
>Academy.  Word spread instantly through the net, a letter writing
>campaign was initiated, and the idea was scrapped.

Awesome.  Move over, Amnesty International.
--
Tim Maroney, Mac Software Consultant, sun!hoptoad!tim, [e-mail]

"This signature is not to be quoted." -- Erland Sommarskog

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

Date: Tue, 12 Mar 1991 15:14 EST
From: [e-mail]
Subject: MANY QUESTIONS
X-Organization: SUNY at Plattsburgh, New York, USA
X-Envelope-To: [e-mail]

I'VE BEEN READING THIS LIST FOR ABOUT A YEAR NOW AND AM FINALLY GETTING AROUND
TO POSTING SOME QUESTIONS.  iF YOU HAVE ANSWERS YOU CAN E-MAIL THEM TO ME
DIRECTLY OR POST TO THE LIST.

1.  I HAVE WHAT I CALL A "MEMORIAL WALL" IN MY SHOP WHERE I HAVE PICTURES OF
MOST OF THE HUMANS WHO HAVE DIED IN SPACE OR IN RELATED TRAINING.  I ALSO HAVE
A PICTURE OF LAIKA AS A REPRESENTATIVE OF THE "ANIMALS" THAT HAVE ALSO BEEN
SACRIFICED IN THE EXPLORATION OF SPACE.  I KNOW THAT 3 RHESUS MONKEYS (ALBERT-
1948, MIKE & PAT-1952) AND OTHER DOGS, CATS, ETC. DIED BEFORE ABLE AND BAKER
(RHESUS MONKEYS) WERE SUCCESSFULLY RETRIEVED AFTER THEIR ROCKET FLIGHT IN 1959
CAN SOMEONE PROVIDE ANY SOURCES OF INFORMATION CONCERNING THIS EARLY PHASE OF
SPACE RESEARCH WHICH MAY PROVIDE MORE COMPLETE INFORMATION ABOUT THESE "ANIMAL
PIONEERS"?

2. ON THE SAME WALL I HAVE A NICE PICTURE OF YURI GAGARIN, WHO DIED IN A MIG-15
TRAINING JET CRASH IN 1968.  DOES ANYONE KNOW WHERE I CAN GET A PICTURE OF
VLADIMIR SEREGIN, WHO DIED IN THE SAME CRASH BEFORE HE HAD A CHANCE TO GET INTO
SPACE?

3. BEING A MACHINIST, I HAVE PRETTY GOOD APPRECIATION FOR THE KINDS OF HAZARDS
WHICH ACCOMPANY ALMOST ANY KIND OF MECHANICAL/ELECTRICAL ASSEMBLY WORK.
I REMEMBER HEARING ABOUT 2 TECHNICIANS WHO SUFFOCATED AT KSC AFTER ENTERING A
ROOM OR CHAMBER WHICH HAD BEEN PURGED OF OXYGEN.  I BELIEVE THIS HAPPENNED
BEFORE THE FIRST SPACE SHUTTLE FLIGHT.  ALSO, I THINK ANOTHER TECHNICIAN WAS
KILLED IN A CRANE ACCIDENT JUST RECENTLY...ALTHOUGH I CAN'T REMEMBER EXACTLY
WHERE.  CAN ANYONE VERIFY THIS?  COULD YOU PLEASE FORWARD THEIR NAMES TO ME?  I
FEEL THAT THEY SHOULD ALSO BE REMEMBERED FOR GIVING THEIR LIVES TO ADVANCE THE
CAUSE OF SPACE EXPLORATION.

4.  MORE MORBID CURIOSITY...SINCE THE CHALLENGER EXPLOSION HAS THERE BEEN ANY
EFFORT TO REDESIGN THE SHUTTLE ORBITER SO THAT THE CREW CABIN COULD BE USED IN
AN EMERGENCY SPLASHDOWN?  MAYBE SOMETHING LIKE THE PRESENT CREW CABIN WITH ITS
OWN PARACHUTE SYSTEM AND HEAT SHEILD?  THEN IT COULD BE USED IN AN EMERGENCY
DEORBIT IF THE SHUTTLE ORBITER HAD ENOUGH DAMAGE TO PREVENT A NORMAL RE-ENTRY
(AS MIGHT BE SUSTAINED FROM A COLLISION WITH ORBITAL DEBRIS).  I REMEMBER THAT
RESCUE AND RECOVERY SHIPS COULD NOT APPROACH THE AREA WHERE CHALLENGER FELL
BECAUSE LARGE PARTS OF THE CRAFT CONTINUED TO FALL FOR NEARLY AN HOUR AFTER
THE ACCIDENT.  COULD A SUBMARINE HAVE APPROACHED THE CREW CABIN ANY SOONER OR
WITH ANY GREATER DEGREE OF SAFETY?  ASSUMING THAT A CREW COULD HAVE SURVIVED
THE INITIAL SHOCK AND THE SUBSEQUENT IMPACT WITH THE WATER COULD A SUPPLY OF
OXYGEN BE PROVIDED THAT WOULD SUSTAIN THE CREW UNTIL RESCUE COULD BE ACHIEVED?
I REALIZE THAT WE ARE TALKING ABOUT A SPECIAL CASE AND THAT BECAUSE THE
VEHICLE BEHAVED A CERTAIN WAY IN THE PAST IT MIGHT NOT ALWAYS BEHAVE THE SAME
IN THE FUTURE BUT I'M INTERESTED WETHER ANY OF THESE IDEAS WERE CONSIDERED AND
WHY THEY ARE OR AREN'T POSSIBLE.


5. ON THE LIGHTER SIDE...ARE THERE ANY SHUTTLE MISSIONS PLANNED THAT CALL FOR
CARRYING THE EXTERNAL TANKS INTO LEO?  I THINK IT MAY BE USEFUL AS TRAINING
FOR THE SPACE STATION EVEN IF THE TANKS THEMSELVES CAN'T BE USED AS BUILDING
MATERIAL.  TO RENDEVOUS WITH AN EXTERNAL TANK THAT IS ALREADY IN ORBIT AND
ATTACH ANOTHER TANK TO IT WOULD REQUIRE SOME OF THE SKILLS THAT WILL BE NEEDED
TO ASSEMBLE THE STATION.  COULD THE EXTERNAL TANKS HAVE OTHER USES IN ORBIT
(MICROGRAVITY EXPERIMENTS PLATFORM, STORAGE FACILITY)?  I QUESS I REALLY WANT
TO KNOW WHY THIS ISN'T BEING DONE ALREADY.

6.  ARE THERE ANY PLANS WHICH CALL FOR 2 ORBITERS TO BE FLOWN AT THE SAME TIME
AND RENDEVOUS WITH EACH OTHER?

7.  ARE THERE ANY PLANS FOR JOINT MISSIONS WITH NASA'S RUSSIAN COUNTERPART?  I
THINK IT WOULD BE A GREAT P.R. OPPORTUNITY IF AN ASTRONAUT WERE TO GO TO MIR
ABOARD A SOYUZ AND A COSMONAUT TO FLY ABOARD THE SHUTTLE.  THEN THE SHUTTLE
COULD RENDEVOUS WITH MIR, DO SOME INTERNATIONAL GOOD-WILL TYPE STUFF, MAYBE
EVEN SOME REAL SCIENCE, AND THEN, AFTER SOME TYPE OF EVA THE ASTRONAUT WOULD
COME HOME WITH THE SHUTTLE.  IS THERE ANYTHING PREVENTING SUCH A MISSION?

8.  WHEN (OR IF) WE SEND A MANNED MISSION TO MARS ARE THERE ANY PLANS TO LEAVE
SOMETHING LIKE THE SPACE TELESCOPE THERE?  THE DIAMETER OF MARS' ORBIT AVERAGES
ABOUT 283,420,000 MILES (ABOUT 1.5 TIMES THAT OF EARTH) SO A MARTIANSCOPE DOING
PARALLAX MEASUREMENTS COULD INCREASE THE RANGE FOR WHICH THIS TYPE OF MEASURE-
MENT IS ACCURATE.  THE MARTIAN YEAR EQUALS 687 EARTH DAYS (BETWEEN 22 AND 23
EARTH MONTHS) SO COLLECTING DATA FROM OPPOSITE ENDS OF THE MARTIAN ORBIT
WOULD ONLY TAKE TWICE AS LONG AS IT DOES NOW (HOW LONG DOES PLUTO TAKE TO GET
TO THE OPPOSITE POINT IN ITS ORBIT?) AND THE SCOPE COULD BE USED AT CERTAIN
TIMES IN CONJUNCTION WITH EARTH BASED TELESCOPES TO GET INSTANTANEOUS PARALLAX
MEASUREMENTS...AS LONG AS THE DISTANCE FROM EARTH TO MARS IS KNOWN.  FOR MY
MONEY ANYTHING THAT INCREASES THE AMOUNT OF RELIABLE DATA THAT WE CAN MAKE OUR
EDUCATED GUESSES AND STATISTICAL COMPARISONS FROM IS A GOOD INVESTMENT.  HAS
ANYONE CONSIDERED THIS OPTION YET?

9.  AS AN AMATEUR ASTRONOMER I FIND THE SOLAR TERRESTRIAL FORECAST AND REVIEW
USEFUL AS A GUIDE FOR WHERE AND WHEN TO LOOK FOR SUNSPOTS, FLARES, AND AURORA.
WHENEVER THERE IS A FLARE ALERT IT MAKES ME WONDER WHAT PRECAUTIONS THE MIR
COSMONAUTS TAKE TO AVOID LETHAL EXPOSURE.  DOES MIR HAVE A SHIELDED AREA OR IS
IT PROTECTED BY THE EARTH'S MAGNETOSPHERE?  WHAT SORT OF PROBLEM WILL SOLAR
FLARES PRESENT TO THE MARS MISSION AND ITS CREW WHILE THEY ARE FAR REMOVED FROM
THE PROTECTION OF EARTH.  IS IT FEASABLE TO HAVE A LOT OF MASSIVE SHIELDING ON
SUCH A MISSION WITHOUT AFFECTING THE OVERALL DURATION OF THE TRIP?  AND ONCE
THE CREW HAS ARRIVED IS THE MARTIAN MAGNETOSPHERE STRONG ENOUGH TO PROVIDE
ADEQUATE PROTECTION OR WILL THEY STILL NEED SOME FORM OF SHIELDING (LIKE WAIT
OUT THE STORM IN A CAVE )?  DOES THE INTENSITY OF THE EJECTA DIMINISH BY ENOUGH
OF AN AMOUNT TO MAKE SOLAR SHIELDING LESS CRITICAL FOR A SHIP IN ORBIT AROUND
MARS?

10. AND FINALLY (WHEW) I'VE DECIDED THERE ARE THREE DISTINCT TYPES OF POSTS TO
THIS LIST.  THEY ARE THE FACTUAL POSTINGS, SUCH AS THE UPDATES, PAYLOAD STATUS,
SPACE NEWS, AND ORBITAL ELEMENTS, THE QUESTION AND ANSWER POSTINGS, AND THE
SPECULATION AND REPLY POSTINGS.  DEPENDING ON THE SUBJECT, I OFTEN DELETE MOST
OF THE SECOND TWO CATAGORIES BEFORE SAVING THE FILES AND ONLY INCLUDE THEM
WHEN I FIND THE SUBJECT INTERESTING (ANIMAL SPACE EXPLORERS, TERRAFORMING, THE
'FACE', AND FUTURE PROPULSION FOR EXAMPLE).  IS THERE A LIST DEVOTED TO DIS-
CUSSION OF THESE SPECULATIVE ISSUES THAT I CAN REACH FROM BITNET LAND?  ARE
PEOPLE AS INTOLERANT OF OTHERS OPINIONS AS SOME FLAMERS ON THIS LIST:-)?


THANX AGAIN FOR YOUR HELP.  HAVE A NICE DAY!

 ..............................................................................
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------------------------------

End of SPACE Digest V13 #264
*******************