Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT_ZIP/spacedig/V10_4/V10_425.ZIP/V10_425

Internet Message Format | 1991-07-08 | 19KB

Return-path: <[e-mail]>
X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson
Received: from beak.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/[e-mail] (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests)
          ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/IZg1s7y00VcJQ=Gk5D>;
          Sun, 14 Jan 90 01:36:56 -0500 (EST)
Message-ID: <IZg1rlS00VcJQ=[e-mail]>
Reply-To: [e-mail]
From: [e-mail]
To: [e-mail]
Date: Sun, 14 Jan 90 01:36:35 -0500 (EST)
Subject: SPACE Digest V10 #425

SPACE Digest                                     Volume 10 : Issue 425

Today's Topics:
            Re: Nuclear Reactors in Space
             Re: Airlocks & Life support
              Galileo Update - 01/12/90
          Any NASA COBE Personnel Out There?
            Re: Nuclear Reactors in Space
----------------------------------------------------------------------

Date: 13 Jan 90 23:01:25 GMT
From: microsoft![e-mail]  (David LEVINE)
Subject: Re: Nuclear Reactors in Space

In article <[e-mail]> [e-mail]
# (Kieran A. Carroll) writes:
#Ha!  You've gotta be kidding.  RTG's are NOOOKLIER,
#made of ATOMS just like ATOMIC BOMBS.

Isn't that NOOOKULER?
                ^
#
#It's an unfortunate fact of life that there are a number of people out
#there who react to any mention of the "N-word" with mindless,
#unreasoning, superstitious dread, and no arguments, no matter how well
#reasoned and firmly based in fact, will sway them in the slightest.
#
#(I have heard some reasoned, though, in my opinion, quite mistaken
#arguments against nuclear power.  Tim's wild-eyed paraoid rantings
#against anything containing the "N-word" are not among them.)

Its been this way for a long time and there are good reasons for the
paranoia.  Back in 1950 when the US was sitting on top of the world,
atomic power was going to save mankind.  A pamphlet entitled
"Operation Atomic Vision" promised that atomic power would solve all
of our problems -- there would be no hunger and no disease and everybody
would be happy.  This was the official word from the Atomic Energy Commision.

Well, it didn't happen.  In fact, the whole thing has been one big
mess.  We jumped in too far too fast without really understanding the
dangers.  In all sorts of small ways, the fledgling commercial
nuclear industry was subsidized by the government and was not
competitive on its own.  The construction and operation of the plants
has often been done with abysmal standards.  An "N" plant is
reasonably safe if built and operated to spec and a potential
disaster if not.  It has not been treated with the seriousness it
deserves.  Of course, the study of nuclear physics has provided many
other practical improvements to the quality of our life besides
nuclear energy.

The defense agencies were worse.  They did not protect the public or
their own personel from the hazards of above ground testing.  The
mistakes and cost cutting measures in the nuclear facilites has resulted
in the horrible mess we see today trying to clean up old sites and
get rid of waste products.

For YEARS (and perhaps still today), when ordinary citizans questioned what
was going on, they were rebuffed, lied to, or ignored.  Sometimes, they
were harrassed by public and private entities whose toes they stepped on.
It was not possible to put a leash on the companies that built and
operated the plants and especially not on the military.

Slowly, the public became aware of the dangers and started providing
support for the few individuals who had earlier been fighting alone.
Three Mile Island greatly increased the momentum.  The huge backlash
has contributed to the construction of new plants grinding to a halt.

This new grass roots army of anti-nuclear activists usually fits the
bill of reacting to the "N-word" with "mindless, unreasoning, superstitious
dread."  These people are not scientists (not even computer scientists #:->).
However, they know they have been lied to.

I used to love looking at anti-nuclear literature and poking huge holes
in it, both techinical and historical.  The biggest anti-nuclear
organizer on campus admitted that much of the literature he passed around
(he got it from an umbrella organization) was bogus, but people believed
it and supported the cause and that was the important thing.

You don't get a mass movement by painting the problem in shades of grey,
that is partly why (IMHO) you see so many anti-nuclear fanatics.

This has basically killed the future of the nuclear industry and has led
to things like the recent RTG incident.  "But the *scientist* say that
the RTGs are safe to launch" you say.  Those same scientists also
said that above ground nuclear tests were OK.  There is a big
credibility gap here.

By the way, I worked on Galileo for six year while at JPL.  I am quite glad
it went up, thank you.  I'm just trying to justify the seeming insanity
of the Christics and others.  Someone suggested that their motivation was
simply to disrupt large organizations.  This is a bit hard to swallow.

John Q. Public is not an expert in risk analysis or statistics.  The
Galileo launch *was* a quantifiable risk to the residents of southern
Florida.  Many people just don't understand the comparison to other routine
risks (like slipping in the shower or driving over a bridge which might
collapse).

DISCLAIMER:  I think nuclear technology is great stuff.  The commercial
and military nuclear industries are another story entirely however.
I would not want an N plant near my house, nor would I want a
chemical plant or an IC fabrication facility.  Yet my modern life
is based on energy, chemicals and computers.  Yes it is hypocritical.
We must anticipate and pay for the *future* costs of our technology
in order to safeguard everybody.  It certainly will cost more now but
will save magnificently over the long haul.

Sorry, this does not really belong in sci.space, but space scientists must
also understand the social implications of their work.  We will see more
RTG-like incidents in the future.  We must treat those who question the
safety of our pursuits seriously, sometimes they are right!  I don't
mean we should cater to them, but if you brush off one activist like a fly
they will return in hoards.

David Levine


=====================================================
=== The opinions expressed above are entirely mine ==
=== The facts expressed above are probably wrong   ==
=====================================================

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

Date: 13 Jan 90 07:51:39 GMT
From: att!watmath!watserv1!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Airlocks & Life support

In article <[e-mail]> [e-mail] (John Kallen) writes:
>I've often wondered what happens tro the air in the airlocks when
>cosmonauts perform EVAs...

On all US spacecraft, and I'm pretty sure on all Soviet ones, it's simply
dumped.  So far, the mass costs of doing something about it are too high
to be worth it, given that EVAs are infrequent and air compressors are
heavy.

>... Is air sucked out of the airlock prior to the
>opening of the outer hatch before EVA exit, or is it dumped in space when
>the hatch opens?

It's vented through a valve before opening the hatch.  A reasonable fraction
of one atmosphere exerts a good many thousands of pounds of pressure on
a normal-sized hatch; one does not want to just unlatch something holding
back that much force.  Some of the hatches are designed to exploit that
pressure, in fact, to give a better seal:  if the hatch opens inward,
air inside holds the hatch very firmly against the gaskets.  (This is
also a minor safety feature, in that the hatch cannot be opened by
accident with air inside.)  As I recall, both hatches on the shuttle
airlock open inward.

>... Is the
>evacuation of the airlock the activity that makes EVAs so lengthy timewise?

No.  The EVAs themselves are lengthy because work in free fall while wearing
a clumsy suit is difficult.  Preparation for them is lengthy because keeping
the suits' clumsiness to a minimum requires running with an absolute minimum
of pressure in them.  To do that, one has to run the suits on something
approaching pure oxygen.  For various reasons, current preference is to
run spacecraft cabins at near one atmosphere and use a near-normal mix
of oxygen and nitrogen.  The transition from a high-pressure atmosphere
rich in nitrogen to a low-pressure one requires lengthy pre-breathing
of pure oxygen to get the nitrogen out of the astronauts' bodies.  (The
alternative is a strong possibility of decompression sickness, "the
bends", potentially crippling or fatal, as that nitrogen comes out of
solution as bubbles.)  There has been a lot of talk about high-pressure
suits, but getting adequate joint flexibility is difficult.

>... how often does MIR need to be "refueled"
>with air when it is manned? How long can they survive only by recycling with
>LiOH(I think?) before they absolutely need more oxygen...

LiOH takes CO2 out of the air, but it does not restore oxygen.  A constant
trickle of oxygen is required.  Without it, survival time is determined by
how much oxygen there is in the air filling Mir... which is not a lot,
sizable though Mir is.
--
1972: Saturn V #15 flight-ready|     Henry Spencer at U of Toronto Zoology
1990: birds nesting in engines | uunet!attcan!utzoo!henry [e-mail]

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

Date: 13 Jan 90 18:27:55 GMT
From: zaphod.mps.ohio-state.edu!usc!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 01/12/90


             Galileo Mission Status Report
                January 12, 1990

     As of Friday, January 12, 1990, the Galileo Spacecraft is 16,229,650
miles from the Earth, 11,067,810 miles from Venus and was travelling at a
Heliocentric velocity of 73,900 miles per hour.  Round trip light time is
2 minute, 52 seconds.

     Two SITURNS to the Sun were successfully performed without incident
on January 9 and January 12. A total of 1151 real-time commands have been
transmitted to Galileo.  Of these, 845 have been pre-planned in the
sequence design and 306 were not.  In the past week a total of  61 real-time
commands were transmitted; 1 was pre-planned and 60 were not.  To date a
total of 120 contingency commands have been generated and 4 contingency
commands have been transmitted; none were transmitted this week.  This weeks
totals contain 10 commands from EV-05.

     The EV-5 sequence memory load was successfully loaded into the CDS on
January 6.  As part of the load process, elements 212 and 213 of the load
were not received initially and had to be retransmitted.  Preliminary
analysis discovered the CDS had experience eight lock change indications
as detected by the HCD. Investigation into the cause of these lock changes
is in process by systems, CDS and telecom personnel.  The EV-5 sequence
went into operation, as planned, on January 8. The events in EV-5 will
cover spacecraft activities through February 5.

     As part of the investigation into the EUV microprocessor "stop"
anomaly, which occurred during the science checkout activity, the EUV
memory was loaded and readout twice on January 6.  Subsequent to memory
verification, the EUV microprocessor was started on January 8. Memory
readouts were performed prior to and after the microprocessor start and
operation of the EUV was nominal.  The exact cause of the anomaly which
stopped the microprocessor has not been determined.  However, it is unlikely
based on this data that a "hard" failure has occurred in a 6504 memory chip.

     The sixth RPM thruster "flushing" activity was successfully completed
on January 8.  Only the Z, L and S thrusters were "flushed".  Since the P
thrusters are used for periodic SITURNS they were not "flushed" during this
activity.  The temperature profiles for the Z, L, and S thrusters were as
expected and ranged from a peak temperature of about 50 degree C to 100
degree C, well within the predicted limits.

     A command was sent on January 9 to turn off the NIMS shield heater
(26W) for about 3 hours to permit the NIMS to collect Focal Plane Assembly
Temperature data in an attempt to ascertain whether the NIMS radiator
cover was deployed or not.  After 3 hours, the heater was turned on again
consistent with RPM thermal/pressure constraints. Data collected by the
NIMS during the time the heater was off indicated the cover was either
already deployed or that it deployed as a result of the cool down possibly
relaxing any mechanical binding which may have existed.

     The delta DOR function in the RFS was activated for the first time on
January 9.  Delta DOR represents a navigation new data source in addition
to doppler and ranging data already available.  Demonstration of the S-Band
delta DOR is being performed now while the RF link performance is still
"strong" and to allow sufficient time to understand and evaluate the DOR
data and its actual advantages to navigation.  The S-Band delta DOR consists
on modulating the downlink carrier with a 3.82 MHZ sine wave.  It is pointed
out that during the short periods that delta DOR is active, the telemetry
data stream from the Telemetry Modulation Unit is interrupted and no
spacecraft data is transmitted.  Estimates indicate that a 2-3 kg fuel
savings post-Earth flyby is possible based on delta DOR data. The delta
DOR data analysis is in process and is expected to be available around
January 22.

     The AC and DC bus imbalance measurements continued to fluctuate.  On
January 9, the AC imbalance reached 48.4 volts indicative of a near "hard"
short to spacecraft chassis.  The measurement remained stable for several
hours and subsequently dropped to about 40 volts. During this time while
the AC measurement fluctuated upward, the DC imbalance measurement very
slowly crept upward to 20.8 volts and remained stable (see Special Topic).


UPLINK GENERATION/COMMAND REVIEW AND APPROVAL

     The Project reviewed and approved the EV-6 Profile Design on January
12.  EV-6 contains the Venus Encounter Sequence which starts one day before
the Venus closest approach and eight days later.  Venus science data will be
recorded on the Data Management Subsystem (DMS).  The equivalent of four
images will be returned using a technique incremental playback involving
transfer of small portions of recorded science data to the CDS then reading
out CDS memory.

     This process will be done while the telecommunications leak is capable
of supporting the 1200bps downlink. Sequence and command generation starts on
January 15.

     The Project approved the VE-1 and VE-2 Cruise Plans on January 11.
These sequences will cover spacecraft activities from February 19 to March 26
and from March 26 to April 23, respectively.


SPECIAL TOPIC

     The fourth Tiger Team status report to the Project was held on January
10.  Three major topics were covered. PPS reported that after careful review
of the inverter physical layout by LORAL engineers, it was concluded that
the physical spacings between AC and DC functions is large (approximately
30-100 mils) and that the "touching" of AC and DC power lines is very unlikely.
PPS will continue its effort to find any spacecraft event correlations with
the observed imbalance measurements.

     Review of the Spin Bearing Assembly slip ring physical layout revealed
that there are several locations within the four modules where AC or DC or
grounds are adjacent. To determine the feasibility of a slip ring leakage
path, an intensive effort was initiated two weeks ago to develop a model.
The preliminary work to date indicates that it may be possible for small
particles of silver (less than 30 microns) to move under the influence of
electrostatic forces (causes by electric field gradients between adjacent
slip rings) and deposit across the barrier thereby creating a leakage path.
Work will continue on this model to refine the electrodynamic forces and to
generate two dimensional AC and DC electrostatic field diagrams.

     Work has continued to determine the feasibility whether electrical noise
may be corrupting PPS sensor readings. Noise coupling models have been
developed and some stray current paths identified.  Since stray currents may
produce erroneous readings in the PPS sensors, a careful review of all
spacecraft electrical loads is in process. Noise currents on the orbiter of a
few milliamperes may be sufficient to create anomalous readings.


     The Project conducted a detailed review of its readiness and risk for
Venus Science. Assessments were provided by the OET, Sequence and Navigation
Teams of the Engineering Office; the Science Requirement and Ops Planning
Team representing the Science and Mission Design Office, the Flight Control
and Support Office and the Ground Systems Office.  It was concluded that the
Venus Science encounter can be executed, in general, without adverse risk to
the spacecraft; the Flight Team is staffed and trained though there is no
margin in the development of the sequence. We are "GO" for Venus Science.


 Ron Baalke                       |    [e-mail]
 Jet Propulsion Lab  M/S 301-355  |    [e-mail]
 4800 Oak Grove Dr.               |
 Pasadena, CA 91109               |

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

Date: 12 Jan 90 15:32:47 GMT
From: hpfcso!hplisa!hpislx![e-mail]  (Greg Goebel)
Subject: Any NASA COBE Personnel Out There?

I was making notes from the recent SCIENTIFIC AMERICAN article on COBE
when I looked through the "Instrument Parameters" table, under the entry
"Spectral Resolution" for FIRAS:

   0.2 cm^-1

I must've stared at that for five or ten minutes.  Either that's a typo or
I'm missing something.  Any illumination out there?
--
+----------------------------------------------------------------------------+
| Greg Goebel                             NET:     gvg@hpislx                |
| Hewlett-Packard                         HP DESK: GREG GOEBEL / HP0900 / EM |
| MSO Marketing                           PHONE:   Telnet/303 679-3424       |
| POB 301 / MS-CU312 / Loveland CO 80539  FAX:     Telnet/303 679-5957       |
+----------------------------------------------------------------------------+

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

Date: 13 Jan 90 23:09:27 GMT
From: microsoft![e-mail]  (David LEVINE)
Subject: Re: Nuclear Reactors in Space

>something useful well past this point.  And just how do you power the
>proposed TAU (Thousand Astronomical Unit) project?

One configuration I (briefly) worked on used an SP-100 (that space
qualified reactor we've been talking about).

>The engineers at NASA might be a bit slothful, but they aren't entirely dim,

Thanks for the qualifier.

>unlike the Sun at the majority of planets.

Which planets?  Which sun? 8-#:-)

David Levine


=====================================================
=== The opinions expressed above are entirely mine ==
=== The facts expressed above are probably wrong   ==
=====================================================

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

End of SPACE Digest V10 #425
*******************