Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V12_5/V12_594.TXT

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Subject: SPACE Digest V12 #594

SPACE Digest                                     Volume 12 : Issue 594

Today's Topics:
              Re: Photon engine
              Galileo Update - 11/22/90
NASA receives award for minority business development program (Forwarded)
            Re: Magellan Update - 11/16/90
           MONTHLY SOLAR TERRESTRIAL REVIEW

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription notices,
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----------------------------------------------------------------------

Date: 24 Nov 90 04:45:57 GMT
From: mcgill-vision!thunder.mcrcim.mcgill.edu!clyde.concordia.ca!news-server.csri.toronto.edu!utgpu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: Photon engine

In article <[e-mail]> [e-mail] (Henry Troup) writes:
>|>only thing left behind with an expanding cloud of plasma. A 100 tonne
>|>ship accelerating at 1 g requires a 3x10**11 watt powerplant. How
>|>does that compare to the human species total power output these days?
>
>Well, it must be less than the power output of a shuttle at launch, right?

Shuttle power output at launch is 15-20 gigawatts, I believe.

However, the inequality you propose doesn't work.  There is no unique
answer to the question of power output for a given mass at a given
acceleration.  It depends on the exhaust velocity.

A 100T ship at 1G (call it 10 m/s^2) requires a thrust of 1MN.  Thrust
is mass flow times exhaust velocity, by conservation of momentum.  At
an exhaust velocity of 3e8 m/s, naively (ignoring relativistic issues),
we need 3.3e-3 kg/s of mass flow.  Kinetic energy over time of that flow,
with respect to the rocket, naively, is 0.5*mass_flow*ve^2, or about
15e13 W.  Call it 150 terawatts.  I'd have to hit the books to sort out
the non-naive version of this, but it probably won't differ by more than
a small integer, and it might even be the same.

I don't have numbers handy for the whole species or total power, but the
electrical power generating capacity of the US is circa 1 terawatt, I think.

Handling 150TW would be, um, a challenge.  For example, assume an efficiency
of 50%.  (That's awfully good for lasers, which are inherently pretty lossy
devices.)  That means our total power output actually has to be 300TW, and
the missing 150TW comes out as heat.  We have to get rid of that heat...
somehow.  The only long-term answer is radiators, but they're big and heavy.
Ignoring practicalities, let us use evaporative cooling instead.  We'll be
generous and say our lasers can run at 2500K (2227C; if you want it in
Fahrenheit, Rankine, or Reaumur, convert it yourself :-)).  Assume our
evaporative material is water, which has a high heat capacity, call
its heat capacity a straight 4.2kJ/kgK, ignoring heats of melting and
boiling, and assume we start with ice at roughly absolute zero.  Then
we are using a mere 15 kilotons of water per second to cool our 100T
spacecraft.  That won't work. :-)

Another non-trivial consideration for photon rockets is how you power them.
They are fiercely difficult to build.  If you are burning up far more mass
powering them than you are exhausting through them, better you should build
a system with the same net mass flow and a lower exhaust velocity, by using
all the mass as exhaust.  Using fission or fusion to power a photon rocket
is ridiculous, in particular.  Fusion burns hydrogen to helium (ignoring
lots of fine points), releasing quite a small fraction of the total mass
as energy.  Even with no losses, most of your fuel mass is going to run
your fusion reactor, after which you are dumping the helium overboard at
roughly zero velocity (compared to the exhaust velocity, any velocity you
can get for that helium is zero).  Building a fusion rocket would give
similar performance with many fewer problems.  Photon rockets make sense
only if you can power them with total matter annihilation; even matter-
antimatter reactions are better used as rockets than as a power source.
(All the more so because we are not very far from being able to build
antimatter rockets, while handling terawatts for a photon rocket is
well beyond us.)
--
"I'm not sure it's possible            | Henry Spencer at U of Toronto Zoology
to explain how X works."               |  [e-mail]   utzoo!henry

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

Date: 26 Nov 90 16:58:03 GMT
From: swrinde!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Galileo Update - 11/22/90


                          GALILEO STATUS REPORT
                            November 22, 1990

     As of noon (PST) Wednesday, November 21, 1990, the Galileo spacecraft is
8,456,170 miles from the Earth and traveling at a heliocentric speed of
61,788 miles per hour; distance to the Sun is 99,324,410 miles (1.07 AU).
The spacecraft is spinning at 3.15 rpm; downlink telemetry is at 7680 bps
through the Low Gain Antenna.  Round trip light time is 1 minute, 28 seconds.

     A SITURN to lead the sun was successfully performed on November 16.  The
turn, about 22 degrees, was the largest to date and resulted in the spacecraft
leading the sun by about 12.5 degrees.  Spacecraft performance during the
activity was normal and without incident.

     The 21st RPM (Retro Propulsion Module) flushing activity was successfully
performed on November 16.  All thrusters were flushed during this activity
except for the P-thrusters which were used later for the sun point activity.
Successful flushing was directly confirmed and observed via high rate
engineering data at 1200 bps (bits/second).

     Delayed Action Commands (DACs) were sent on November 16 to turn off the
S-Band ranging channel to improve the RF downlink performance for subsequent
Venus science data playback on for November 19, 20 and 21.

     A NO-OP command was sent on November 20 to reset the Command Loss Timer
to 240 hours, the planned value for this mission phase.

     The PPR (Photopolarimiter Radiometer) instrument continued its calibration
and checkout activities.  Preliminary data indicates the instrument is working
well.

     The Venus science data was played back from the spacecraft on November 19,
20, and 21.  The data has been stored on the spacecraft since early February
along with UVS (Ultraviolet Spectrometer) Lyman-Alpha data collected during
cruise.  The data was played back twice from Data Memory Subsystem (DMS) tape
recorder.  Data was returned from tracks 1 and 2 on November 19, then tracks 3
and 1 on November 20, and finally tracks 2 and 3 on November 21.  Preliminary
results indicate all Venus data was successfully returned and is presently
being processed.

     Two delta DOR (Differential One-way Ranging) navigation activities were
completed on November 19. The activities were successful using the 70 meter
antenna pairs at Goldstone/Spain and Goldstone/Australia.  A total of 25 of the
planned 27 delta DOR activities are complete; 21 were successful.

     The NIMS (Near Infrared Mapping Spectrometer) instrument was powered on
November 21.  Several spacecraft heaters were configured to maintain
acceptable power/thermal margins.  Preliminary data indicates the NIMS
instrument is functioning normally.

     The PCT (Photometric Calibration Target) heaters were powered off and the
RCT-NIMS heater was powered on November 22 for power margin management and
thermal control.

     Two non-interactive DACs were sent on November 21 to configure the PWS
(Plasma Wave) instrument to gather calibration data from the magnetic field
sensor; the commands went active later that day.  The first command causes the
PWS to inject a square wave signal tone into its magnetic field circuitry; the
second command reconfigured the PWS back to the normal mode.  The calibration
was performed to verify instrument operation in presence of a known fixed
source.  Review of Venus data and recent (last week) data indicates the
possibility of spacecraft generated time variable electric and magnetic fields.

     Commands were sent on November 21 to turn off the PLS (Plasma) instrument
high voltage.  This action drops the instrument power dissipation by about
1.2 watts and relaxes somewhat thermal concerns expressed by the Principal
Investigator.

     The AC bus imbalance measurements dropped about 3 DN and about 47.5 volts.
This measurement has been relatively stable since its inception and is likely
indicative of a leakage resistance to chassis of about 100-500 ohms.  During
the past 2-3 weeks the DC measurement has gradually dropped from near 18.5
volts to its present value of about 2 volts. The gradual decline has not
correlated with any spacecraft load switching event, thermal environment
change or mechanical activity.  The present reading can be indicative of a
return leakage path to chassis of about 150 ohms.  Tests to better
characterize the PPS telemetry sensor performance are in process.  All other
power-related and spacecraft telemetry measurements are normal.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|
     | | | |  __ \ /| | | |      Ron Baalke         | [e-mail]
  ___| | | | |__) |/  | | |___   Jet Propulsion Lab | [e-mail]
 /___| | | |  ___/    | |/__ /|  M/S 301-355        |
 |_____|/  |_|/       |_____|/   Pasadena, CA 91109 |

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

Date: 29 Nov 90 23:24:20 GMT
From: trident.arc.nasa.gov![e-mail]  (Peter E. Yee)
Subject: NASA receives award for minority business development program (Forwarded)

David Garrett
Headquarters, Washington, D.C.                  November 26, 1990
(Phone:  [phone])


RELEASE:  90-154

NASA RECEIVES AWARD FOR MINORITY BUSINESS DEVELOPMENT PROGRAM


     NASA Administrator Richard H. Truly today accepted the
"Government Agency of the Year Award" from the Black Business
Association of Los Angeles for NASA's participation in minority
business development.

     The award, given annually in conjunction with the
association's trade mission to Washington, D.C., is presented to
the government agency which has the most successful program
designed to encourage minority business development.

     "NASA has earned this award for its aggressive and
innovative approach to the small and disadvantaged business
program.  Our members currently hold contracts with NASA
locations in excess of $50 million across the country, compared
to $16 million 3 years ago," said Association Chairman Gene
Hall.  "We would like NASA to keep up the good work."

     Upon receiving the award, Truly acknowledged pride in being
recognized for NASA's program to encourage development of small
and disadvantaged businesses.  He also pledged that NASA would
continue to be a leader in this area as it looked for new ways to
increase the participation of minority businesses in the nation's
civil space program.

     Eugene Rosen, Director of NASA's Small and Disadvantaged
Business Utilization Office, said, "our outreach efforts are
increasing nationwide to small disadvantaged businesses to inform
them of the possibilities of contracting with NASA.  We also are
in the process of installing a mentor program to encourage major
corporations to assist small, disadvantaged businesses in
becoming viable."

     The association, the second largest of its kind in the
nation, has 450 members, 75 of them located outside of the Los
Angeles area.

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

Date: 24 Nov 90 23:34:01 GMT
From: ucselx!crash![e-mail]  (Adams Douglas)
Subject: Re: Magellan Update - 11/16/90

In <[e-mail]> [e-mail] (Henry Spencer) writes:
>In article <[e-mail]> [e-mail] writes:
>>>... what does the science community hope to learn
>>>by mapping Venus?
>>    The reason that we are mapping Venus is to answer many unanswered questions
>>about the earth's origins...
>[Enter cynic mode.]  Nonsense.  We are mapping Venus to learn more about
>*Venus's* geology and origins.  This will improve our knowledge of planets
>in general, and thereby may eventually improve our understanding of Earth

Hey, let's be totally honest. Besides the science, we're also mapping Venus
because it's NEAT! Never lose that thought!

--
====================================================================
Adams Douglas
3206 Raintree Circle         -sometime I'll think of a good quote for here-
Culver City, CA 90230
                                          crash!adamsd

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

Date:    Sun, 25 Nov 90 18:50:35 MST
From: [e-mail] (Cary Oler)
Subject: MONTHLY SOLAR TERRESTRIAL REVIEW
X-St-Vmsmail-To: ST%"[e-mail]"

                   ---  MONTHLY SOLAR TERRESTRIAL REVIEW  ---
                                  October 1990

                Report Issued In-Part from Data Released by the
                       Space Environment Services Center
                               Boulder Colorado

                                   --------


MONTHLY ACTIVITY SUMMARY AND SOLAR CYCLE OUTLOOK NOVEMBER 1990 - MAY 1991

     We are now in month 50 of solar cycle 22.  Averaged activity levels and
solar indices were up again in October compared to September, but not nearly
enough to affect the prediction that July 1989 was in fact the solar maximum
of cycle 22.  The largest increase was observed in daily sunspot number and
the monthly average was up almost 33 points over September values.  The
prediction model used for smoothed sunspot number shows that there is still a
slight statistical possibility that solar maximum is yet to come.  However,
for this to be true, the activity and solar indices would have to reach the
levels obtained in August 1990 and maintain that level for a number of
months.  If time proves July to be just a relative peak of activity and not
the solar maximum, then the regression model predicts late spring 1991 as the
next probably candidate.  However, at this time we do not see any indication
of the kinds of activity that would be necessary to unseat July 1989 as solar
maximum of cycle 22.

     Flare activity ranged from low to high during October.  There were a
total of eleven M-class flares reported during the month.  The two largest,
an M8/1N Tenflare at 18:06 UT on 20 October and an M3/SF at 06:02 UT on 21
October, originated from Region 6311 which became quite active on 20-21
October, producing three M-class flares before it crossed the limb late on
the 21st.  There was a very slight proton enhancement at satellite altitudes
which began around 09:00 UT on 23 October, reached a maximum of 4 pfu at the
>10 MeV range at 14:25 UT on 23 October, and lasted about 36 hours.  Although
no solar event can be pinpointed as the cause of this proton enhancement, its
signature suggests that it originated as an east limb event.

     Geomagnetic activity ranged from quiet to minor storm levels at mid
latitudes and quiet to severe storm levels at high latitudes.  The two most
disturbed days were 10-11 October when mid latitudes experienced minor storm
conditions and high latitudes experienced one day of severe storm and one day
of major storm conditions.  Although no individual event can be suggested as
responsible for this activity, it is possible that the interplanetary
magnetic field was aligned southward, allowing solar wind energy to be passed
efficiently to the magnetosphere, in essence, enhancing the effects of
earlier solar disturbances.

     Radio propagation conditions during the month ranged from very poor
levels at high latitudes to very good levels at low latitudes.  The most
disturbed period occurred in conjunction with the minor geomagnetic storm of
10-11 October.  Significant auroral flutter and fading caused poor HF
propagation over most paths.


SIX MONTH SOLAR CYCLE OUTLOOK

     Prediction models indicate another small increase in the raw solar
indices for November, still not enough to affect July 1989 as solar maximum.
A drop in December and a leveling off through the first couple of months of
the new year are also predicted.  No great deviation from the activity levels
of the last two months are foreseen at this time.

     Radio propagation conditions over the next six months look relatively
good.  No significant changes in overall conditions are expected, excluding
the normal seasonal variations.  Approximately one minor to major geomagnetic
storm can be expected every month or two. Therefore, between 3 to 5
significant periods of degraded propagation conditions should be anticipated
over the next six months, provided current models are accurate in predicting
pulses of solar activity and recurrent phenomena.

     The occurrence of SIDs/SWFs should persist throughout the next six
months.  Present solar models suggest that December through January will
likely be the least productive months in terms of solar flare and SID/SWF
activity.  Also, a decline in MUF is anticipated for December and the first
part of the new year, coinciding with decreased levels of ionospheric
ionization.

     VHF propagation should remain mostly normal throughout the next six
months, with decreased probabilities of DX contacts in December and January.
Reduced MUF will also make DX openings on 50 MHz somewhat unlikely during
these months of expected decreased solar activity.  Although reduced MUF's
are anticipated, there remains a moderate probability for some potential
auroral backscatter communications on VHF bands during periods of minor to
major geomagnetic and auroral storming.  Middle and high latitudes will
benefit the most during these periods.


    RECENT SOLAR INDICES (PRELIMINARY) OF THE OBSERVED MONTHLY MEAN VALUES
                           Updated for October, 1990

              Sunspot Numbers                   Radio Flux    Geomagnetic
      ------------------------------------     -------------  -----------
       Observed     Ratio    Smooth Values    Ottawa  Smooth       Smooth
      SESC    RI   RI/SESC    SESC    RI       10 cm  Value    Ap  Value
      ------------------------------------     -------------  -----------
                                  YEAR = 1988

Nov:  153.8  125.1  .82       168.3  130.2     156.2  177.5    12   16.1
Dec:  229.5  179.2  .78       180.1  137.4     199.8  184.8    13   16.5

                                  YEAR = 1989
Jan:  203.2  161.6  .80       189.2  141.9     235.4  190.2    19   16.7
Feb:  211.0  164.5  .78       196.0  144.7     222.4  194.0    15   17.0
Mar:  176.8  131.0  .74       204.1  149.4     205.1  199.7    41   17.6

Apr:  172.3  129.3  .75       209.9  153.1     189.6  204.4    23   18.2
May:  207.0  138.4  .67       216.4  156.5     190.1  209.3    16   18.8
Jun:  297.3  196.0  .66       220.1  157.9     239.6  213.1    17   19.2

Jul:  193.9  126.8  .65       221.1  158.1     181.9  212.6     8   19.1
Aug:  243.0  166.8  .69       221.5  157.4     217.1  209.7    20   19.3
Sep:  240.7  176.8  .74       221.3  156.3     225.9  207.2    17   18.8

Oct:  217.4  158.5  .73       223.2  157.1     208.7  206.3    21   18.3
Nov:  255.0  173.0  .68       223.4  157.3     235.1  206.1    19   18.4
Dec:  217.8  166.1  .76       217.3  153.3     213.0  203.3    16   18.4

                                  YEAR = 1990
Jan:  239.3  179.4  .75       212.4  150.3     210.1  200.4    14   18.6
Feb:  184.7  128.4  .71       213.9  152.5*    178.3  200.5*   23   18.8
Mar:  198.6  140.8  .71       212.7  151.7*    188.8  198.6*   23   18.6

Apr:  196.1  139.8  .71       210.5  149.0*    185.3  195.3*   27   18.2*
May:  187.7  132.0  .70                        189.7           16
Jun:  168.9  105.2  .62                        170.9           16

Jul:  204.3  147.0  .72                        180.7           14
Aug:  269.4  199.9* .74*                       221.6*          19
Sep:  186.4  124.7* .67*                       175.8*          14

Oct:  219.0  145.2* .66*                       180.6*          14*

* = Preliminary estimates

The lowest smoothed sunspot number for Cycle 21, RI = 12.3, occurred in
September 1986.  The preliminary sunspot maximum for this cycle (cycle 22)
remains July 1989, with a peak smoothed sunspot number of 158.1.


DAILY SOLAR DATA FOR OCTOBER, 1990.


                ENERGITIC EVENT SUMMARY (MINOR AND MAJOR FLARES)
 _____________________________________________________________________________
| Date |    Time (U.T.)  | X-Ray |    Optical Information       | Sweep Freq. |
|      | Begin  Max  End | Class | Type     Location     Region |  Intensity  |
|------|-----------------|-------|------------------------------| II III IV  V|
|08 Oct| 0652  0706  0729| M1.5  |  Uncorrelated event.         |   |   |  |  |
|09 Oct| 0853  0911  1028| M1.6  |  1F       S18E71       6314  |   |   |  |  |
|10 Oct| 1753  1804  1824| M1.1  |  SN       S17E60       6314  |   |   |  |  |
|11 Oct| 0735  0741  0749| M1.0  |  1N       N09E44       6312  |   |   |  |  |
|15 Oct| 0129  0135  0147| M2.8  |  1N       S21E41       6321  |   |   |  |  |
|16 Oct| 1716  1728  1733| M1.4  |  Uncorrelated event.         |   |   |  |  |
|20 Oct| 1753  1806  1812| M8.5  |  1N       N15W82       6311  |   | 1 |  | 2|
|21 Oct| 0312  0320  0325| M1.0  |  SF       N16W92       6311  |   |   |  |  |
|      | 0553  0602  0629| M3.0  |  SF       N14W89       6311  |   | 1+|  |  |
|      | 0949  1008  1106| M1.7  |  SF       N18E23       6327  |   | 2 |  |  |
|22 Oct| 0611  0641  0740| M2.9  |  SF       S08W50       6322  |   | 1+|  |  |
|______|_________________|_______|______________________________|_____________|

NOTES:

 - Xray Flare Classes (weak to strong): C, M, X (with sub-categories rated
   from 0.0 to 9.9 in each class).

 - Optical Flare Classes (weak to strong): S, 1, 2, 3, 4 (with an
   attached figure identifying brightness: F-Faint, N-Normal, B-Brilliant).

 - Locations are given in latitude and longitude as measured from the
   central solar meridian.

 - Sweep Frequency Intensity represents the intensity of detected solar radio
   frequency bursts (bursts sweep over large frequencies).  Type II and IV
   almost always represent ejection of solar material through the solar corona
   and into interplanetary space.  Intensities are rated from 1 to 3+.



                         GENERAL DAILY SOLAR STATISTICS
 _____________________________________________________________________________
|       | Radio Flux  |           |  Sunspot   |           Flares             |
|       |   Ottawa    |  Sunspot  |    Area    |   X-Ray          Optical     |
|Date   |  10.7 cm    |  Number   | mil.sq.km. | C   M   X  |  S   1   2   3  |
|-------|-------------|-----------|------------|--- --- --- | --- --- --- --- |
|01 Oct |     158     |    169    |   2,730    | 3   0   0  | 12   1   0   0  |
|02 Oct |     161     |    182    |   3,450    | 6   0   0  | 20   2   0   0  |
|03 Oct |     177     |    180    |   4,710    |10   0   0  | 25   2   0   0  |
|04 Oct |     184     |    208    |   5,130    | 8   0   0  | 16   1   0   0  |
|05 Oct |     169     |    214    |   3,780    | 6   0   0  |  9   1   0   0  |
|06 Oct |     169     |    181    |   3,270    | 5   0   0  |  6   2   0   0  |
|07 Oct |     168     |    208    |   3,870    |12   0   0  | 10   0   0   0  |
|08 Oct |     179     |    229    |   4,440    | 7   1   0  | 12   1   0   0  |
|09 Oct |     182     |    224    |   4,380    | 8   1   0  | 13   3   0   0  |
|10 Oct |     192     |    216    |   5,520    | 5   1   0  | 18   0   0   0  |
|11 Oct |     202     |    278    |   6,000    |11   1   0  | 14   1   0   0  |
|12 Oct |     200     |    267    |   5,550    |10   0   0  | 25   0   0   0  |
|13 Oct |     207     |    297    |   5,430    | 8   0   0  | 20   1   0   0  |
|14 Oct |     220     |    287    |   5,970    | 5   0   0  | 23   2   0   0  |
|15 Oct |     232     |    368    |   6,300    |14   1   0  | 34   2   0   0  |
|16 Oct |     226     |    361    |   5,790    | 4   1   0  | 25   0   0   0  |
|17 Oct |     193     |    283    |   6,450    |10   0   0  | 26   2   0   0  |
|18 Oct |     195     |    260    |   5,730    |12   0   0  | 13   3   1   0  |
|19 Oct |     221     |    257    |   5,430    | 8   0   0  | 25   0   0   0  |
|20 Oct |     200     |    276    |   4,350    |16   1   0  |  6   2   0   0  |
|21 Oct |     187     |    185    |   1,980    | 4   3   0  | 15   3   1   0  |
|22 Oct |     169     |    221    |   1,860    | 4   1   0  | 13   1   0   0  |
|23 Oct |     164     |    181    |   1,620    | 9   0   0  | 12   2   0   0  |
|24 Oct |     157     |    180    |   2,070    | 8   0   0  | 12   0   0   0  |
|25 Oct |     163     |    183    |   2,310    |10   0   0  | 20   2   0   0  |
|26 Oct |     154     |    171    |   2,010    | 7   0   0  | 16   2   0   0  |
|27 Oct |     164     |    139    |   1,680    | 3   0   0  |  6   0   0   0  |
|28 Oct |     152     |    158    |   2,940    | 2   0   0  | 10   0   0   0  |
|29 Oct |     156     |    155    |   3,270    | 7   0   0  |  9   0   0   0  |
|30 Oct |     154     |    126    |   2,910    | 7   0   0  | 10   0   0   0  |
|31 Oct |     143     |    109    |   2,640    | 5   0   0  | 10   0   0   0  |
|_______|_____________|___________|____________|____________|_________________|


**  End of Report **

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

End of SPACE Digest V12 #594
*******************