Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_2/V13_285.TXT

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Subject: SPACE Digest V13 #285

SPACE Digest                                     Volume 13 : Issue 285

Today's Topics:
               Re: Reliability
         Re: New World Profits (was Re: Space Profits
                  Re: Thrust
            Re: Galileo Update - 03/18/91
Re: German conference highlights doubts about ESA's manned space plans
        MAJOR SOLAR FLARE ALERT - 16 MARCH - EVENT #2

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Date: 13 Mar 91 11:29:00 GMT
From: sdd.hp.com!elroy.jpl.nasa.gov!swrinde!zaphod.mps.ohio-state.edu!think.com!linus!philabs!ttidca!quad1!bohica!mcws!p0.f851.n102.z1.fidonet.org![e-mail]  (John Roberts)
Subject: Re: Reliability

From: [e-mail] (John Roberts)
Path: wciu!elroy.jpl.nasa.gov!decwrl!ucbvax!CMR.NCSL.NIST.GOV!roberts
Newsgroups: sci.space
Subject: Re: Reliability
Message-ID: <[e-mail]>
Date: 13 Mar 91 03:29:24 GMT

>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]



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

Date: 13 Mar 91 19:58:00 GMT
From: agate!linus!philabs!ttidca!quad1!bohica!mcws!p0.f851.n102.z1.fidonet.org![e-mail]  (Unknown)
Subject: Re: New World Profits (was Re: Space Profits

From: [e-mail]
Path: wciu!elroy.jpl.nasa.gov!swrinde!zaphod.mps.ohio-state.edu!rpi!crdgw1!gecrdvm1!gipp
Newsgroups: sci.space
Subject: Re: New World Profits (was Re: Space Profits
Message-ID: <[e-mail]>
Date: 13 Mar 91 11:58:47 GMT
In article <[e-mail]>, [e-mail] (Dan Tilque) says:
>
>[e-mail] (Jack Dietz) writes:
>>
>>In article <[e-mail]> Dan Tilque writes:
>>
>>>slower rate or even halted altogether.  However, Columbus knew
>>>this and kept exploring until he had at least something valuable to
>>>show for his trip.
>>
>>This implies that Columbus was exploring what he thought was unprofitable
>>land.  In other words, he was using the money of the Spanish crown in
>>order to satisfy his desire to explore, not in the interests of the
>>royal pair.
>
>
>>Interesting.  If only our explorers could pull something like that
>>off, leading Congress on while they encourage exploitation...
>
>NASA administrators are good at something like this.  It's a required
>ability of higher level bureaucrats.
>
>---
It's the state of R&D in the US:  Bullshit about what you've "almost"
got your hands on, and get the company (or even better-the gov't)
to pay for the next "trip" (also known as next years budget). the
name of the game isn't to invent, but to spend money and write
papers.  Doesn't matter if you invent, the company usually doesn't
know what to do with it anyway!
Pete (I damn well better put a disclaimer on this one) Gipp
all opinions here are mine and do not reflect the views of any
company I work for or know of

"nobody knows anyone at all, strangers in paradise down at the mall,
everybody needs a home"....Iggy


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

Date: 11 Mar 91 11:20:00 GMT
From: agate!linus!philabs!ttidca!quad1!bohica!mcws!p0.f851.n102.z1.fidonet.org![e-mail]  (Nick Szabo)
Subject: Re: Thrust

From: [e-mail] (Nick Szabo)
Path: wciu!elroy.jpl.nasa.gov!usc!zaphod.mps.ohio-state.edu!wuarchive!uunet!zephyr.ens.tek.com!tektronix!sequent!crg5!szabo
Newsgroups: sci.space
Subject: Re: Thrust
Message-ID: <[e-mail]>
Date: 11 Mar 91 03:20:23 GMT
In article <[e-mail]> [e-mail] (John Roberts) writes:
>Another method that has been mentioned is launching water from Earth, then
>using solar energy to convert it to hydrogen and oxygen for use in a
>conventional engine. Because of its greater density, the water should be
>much cheaper to launch than LOX/LH2.

Much cheaper, for high volumes, would be to capture a small burned-out
comet and launch low-mass mining and processing equipment (ice is much
easier to deal with than rock).   It would take two or three Delta
launches ($80-$120 million) to deliver 100 million kg into GEO
or higher orbit.  This gives us $1/kg plus the cost of upper stage,
retreival, and mining equipment.  Capture is accomplished via gravity
assist and/or aerobraking, with a small mass driver for fine-tuning.

The scientific and technological prerequisites are:

* We need to develop low-mass (<1 Delta payload) mining equipment that
  can operate in microgravity and vacuum to process methane and water
  ice with a small surface layer of tar, dust, and rock;
* We need to increase our tracking of near-earth asteroids from <0.1% to
  at least 10% of the c. 100,000 in the size range above 100m.

The water and methane can be moved to LEO, and used directly as reaction
mass for solar or nuclear thermal rockets.  The water can also be
electrolyzed into hydrogen and oxygen for use in chemical rockets.
These volatiles could also be used for life support, shielding, and
might provide raw materials for larger-scale space manufacturing.


>It might be possible to save even
>more money by using an exotic launch method such as linear or laser launch.
>(How 'bout that, Nick?)

This would be very valuable for cargo that cannot be easily mined
(all cargo for now). I urge NASA and government labs that want in on space
to get to work on advanced launch options.

Both of these cases provide clear examples of why both basic science
(in this case, astronomy) and advanced technology research are so
important to space development, and why setting narrowly defined
goals must be avoided.




--
Nick Szabo            [e-mail]
"What are the _facts_, and to how many decimal places?"  -- RAH


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

Date: 19 Mar 91 01:41:21 GMT
From: uhccux![e-mail]  (David Tholen)
Subject: Re: Galileo Update - 03/18/91

>         Galileo will be the first spacecraft to fly by an asteroid when it
> approaches within about 1,000 miles of the irregularly shaped, stony lump
> measuring nearly 15 miles across.  During the encounter, the spacecraft will

Probably meant to say 15 kilometers across.  The published catalog of IRAS
detections of asteroids shows one successful observation of Gaspra, and that
indicates an effective diameter of 15.5 km.  However, I understand that the
latest orbit for Gaspra has shifted its expected position on the IRAS
detectors toward the edge, meaning that the quality of the measurement is
now in question.  In addition, Gaspra has a fairly substantial rotational
lightcurve variation, indicating an elongated shape, and nobody knows at what
point in the rotational lightcurve the IRAS observation was made, so the
stated diameter is rather uncertain.  The range of 1,000 miles is correct, so
if the true effective diameter is indeed about 15 km, then Gaspra will
slightly overfill the Galileo camera field of view.

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

Date: 15 Mar 91 18:20:41 GMT
From: agate!bionet!uwm.edu!rpi!zaphod.mps.ohio-state.edu!unix.cis.pitt.edu!pitt!nss![e-mail]  (Paul Blase)
Subject: Re: German conference highlights doubts about ESA's manned space plans

[re robots vs humans in repairing space vehicles in orbit]
reply to posting by Andreas G. Nowatzyk

 AG> Hardware that isn't designed for this, will require a very
 AG> elaborate robot. However if the design takes robotic service
 AG> into account, things change dramatically. For example, a lot of
 AG> consumer equipment (VCRs & such) and some computer gear (Mac's,
 AG> printers, etc.) are now routinely designed for robotic
 AG> assembly....

Yes but there's a significant difference between designing something to
be ASSEMBLED by a robot and designing it to be FIXED by one.  In general,
If you want it to be repairable robotically, the cost will go up.  Don't
forget the cost of the robot in the first place, anything that has the
abilities of a human will cost mucho bucks.  Besides, there will always
be those situations that robots are not able to handle.  You mentioned
Solar Max; wasn't it spinning? I remember the astronaut having to do
some unconventional maneuvers to catch the thing.

I imagine that much will be done in space by both robots and telefactors.
However, we shouldn't limit ourselves too much.

--- via Silver Xpress V2.26 [NR]
--
Paul Blase - via FidoNet node 1:129/104
UUCP: ...!pitt!nss!Paul.Blase
INTERNET: [e-mail]

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

Date:    Sun, 17 Mar 91 01:28:51 MST
From: [e-mail] (CARY OLER)
Subject: MAJOR SOLAR FLARE ALERT - 16 MARCH - EVENT #2
X-St-Vmsmail-To: st%"[e-mail]"

                        --  MAJOR SOLAR FLARE ALERT  --

                                MARCH 16, 1991
                                   Alert #2

                              Flare Event Summary
                          Potential Impact Assessment


                                    --------



MAJOR ENERGETIC EVENT SUMMARY

     Region 6545 continues to produce major flares.  Another major flare
occurred at 21:58 UT on 16 March.  This flare began at 21:52 UT, peaked at
21:58 UT and ended at 22:15 UT on 16 March.  The intensity achieved was a
class M6.0/2B rating with an associated 400 s.f.u. tenflare.  Radio
emissions were again fairly rich, although not as intense as in previous
X-class flares from this region.  The intensity at 245 MHz reached 10,000
s.f.u..  The location of this flare was S09W04.

     Region 6545 continues to exhibit a moderate amount of magnetic
complexity.  It maintains a beta-gamma-delta configuration and contains a
fair amount of shear.  This region has spawned numerous minor M-class
flares over the past 24 hours, including an M4.8/1B at 10:54 UT on 16 March.

     A proton enhancement continues at the present time, together with a
small Forbush decrease which was first observed on 12/13 March coinciding
with an interplanetary shock (of uncertain origin) and a following brief
period of major magnetic storming.


POTENTIAL TERRESTRIAL IMPACT ASSESSMENT

     No terrestrial impact is expected from the most recent M6.0/2B
tenflare.  This flare was not associated with any sweeps and does not pose
much of a threat.

     There is concern, however, regarding the potential impacts of the
recent class X1.8/2B tenflare with associated strong Type II and IV sweeps
which occurred at 00:16 UT on 16 March.  There is uncertainty among
forecasters regarding this event.  At the present time, a light to moderate
impact is expected late on 17 March or on 18 March.  Minor storming is
expected for the high latitudes and northerly middle latitudes.  No major
storming is expected.  But given the recent unpredictability of events and
uncertainty present among the forecasting community, confidence levels are
not very high with regards to the possible accuracy of these predictions.

     The one area where there is a strong consensus is with regards to the
possibility for proton and PCA activity.  There is a fairly high
probability (now near 50%) that a major energetic flare could produce
proton and PCA activity, particularly since the proton levels are already
elevated near event thresholds.  A condition YELLOW alert status will
remain in place for possible PCA activity.  Polar regions should be on the
alert for possible flare-induced PCA activity.  Radio communicators should
be aware of the elevated risk for polar blackout conditions on HF polar
paths should solar protons produce PCA activity.

     Further major flare alerts will be posted as needed.  For an update on
the status of the warnings, consult the recent Solar Terrestrial Bulletin
for 06:00 UT on 17 March.


**  End of Alert  **

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

End of SPACE Digest V13 #285
*******************