Space & Astronomy/Space and Astronomy (October 1993).iso/pc/text/spacedig/v13_2/v13_284.txt

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Subject: SPACE Digest V13 #284

SPACE Digest                                     Volume 13 : Issue 284

Today's Topics:
           Abstract of articles in ESA Journal 90/4
            Salyut 7 in Argentina
                 Shuttle size
         Re: railguns and electro-magnetic launchers
              Magellan Update - 03/19/91
         Re: Titan IV Launch - March 8, 1991
Re: German conference highlights doubts about ESA's manned space plans

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
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----------------------------------------------------------------------

Date: 17 Mar 91 13:25:07 GMT
From: mcsun!hp4nl!phigate!philtis![e-mail]  (Harm Munk)
Subject: Abstract of articles in ESA Journal 90/4

Summary of articles in ESA-journal, Volume 14, nr. 4 (1990/4)

Inter-Operability of Europe's Hermes Spaceplane with the Columbus
Free-Flying Laboratory, and with 'Freedom' and 'Mir'-type Space
Stations
[F. Di Mauro, D. Cornier, L. Marechal, W. Fehse, A. Tobias]

The European Hermes spaceplane, which development is primarily
targeted towards servicing the Columbus Free-Flying Laboratory
(during 7 day missions every 180 days), will also be able to
provide the Space Station 'Freedom' with complementary servicing,
and, alternatively, crew-rescue, exchange of international crews
and supplying the European experiments. 'Mir'-type space stations
will be visited in the course of a common scientific programme.
This will be accomplished through the use of an expendable Hermes
Resource Module (HRM), attached to the rear of the Hermes
spaceplane, which carries the docking ports, berthing mechanisms
and utilities interfaces (with different requirements for all
three types of space stations) as well as cargo for the station
being visited.
The Hermes system will consist of a fleet of two spaceplanes,
with three missions per year. Each spaceplane will have a
lifetime of 15 years and 30 missions.
The article describes, besides the rendez vous and docking
scenario's for the three space stations, several organisatorial
aspects and issues to be resolved of the Hermes operations.


The Newton Mission - A Proposed Manmade Planetary System in Space
to Measure the Gravitational Constant
[A.M. Nobili, A. Milani, E. Polacco, I.W. Roxburgh, F. Barlier,
K. Aksnes, C.W. F. Everitt, P. Farinella, L. Anselmo, Y. Boudon]

The Newton mission was one of 22 mission proposals submitted in
response of a recent Call for Proposals for the second medium-
size mission to be considered for incorporation into ESA's Space
Science: Horizon 2000 Programme. Although dropped in favour of
the STEP mission (to test the Equivalence Principle), the Newton
proposal generated considerable interest during the evaluation.
The purpose of the Newton mission is to measure the gravitational
constant, G, to an accuracy of 1 part in 10 000. (The best Earth
based measurements of G can do no better than 1 part in 100.)
In effect, Newton consists of a spin stabilised cylinder with a
base diameter of about  3 meters and a height of 3.5 meters.
Inside the cylinder, a miniature planetary system consisting of
a planet with a mass of 75 kg and a satellite with a mass of 2
kg, performs an almost perfect free fall. An inward looking
camera will track the motion of the system and small thrusters
on the outside of the cylinder will adjust the trajectory of the
cylinder. The cylinder will so follow the trajectory of a drag
free satellite. An added benefit is the ability to map the
gravitational field surrounding Earth, and, by keeping track of
the corrections done by the small thrusters, to measure the
variation of the solar radiation flux. If an accelerometer is
added to the Newton payload, it can be very accurately
calibrated.


Precise Satellite Skin-Force Modelling by Means of Monte-Carlo
Ray Tracing
[. Klinkrad, Ch. Koeck, P. Renard]

In order to increase the precision of orbit predictions of
satellites, in particular for geodetic satellites, it becomes
essential to model non-gravitational forces. Matra has developed
software to model four of the so-called skin forces acting on
satellites. These forces are: aerodynamic forces (lift and drag),
direct solar radiation pressure, earth albedo radiation pressure
and earth IR radiation pressure. The forces can be computed for
a satellite of arbitrary shape complexity and surface properties.
Also, multiple reflections will be included in the computation.
The computation is based on Monte Carlo ray tracing techniques.
The trade-off between computing time and accuracy can be tailored
to user needs by the parameters of the ray tracing.


Attitude and Orbital Modelling of Solar-Sail Spacecraft
[F. Angrilli, S. Bortolami]

The fifth centenary of the discovery of America by Columbus will
be commemorated by the Space Sail Cup in 1992 between the
continents of America, Europe and Asia. The spacecraft will be
lifted to an orbit with an perigee of 1 000 km and an apogee of
36 000 km, free of charge to the design groups. Each spacecraft
may not have a weight of more than 500 kg at launch. Using solar
radiation pressure alone, the spacecraft must then escape from
the Earth gravitational field and, after a lunar flyby, head
towards Mars in an interplanetary orbit around the Sun. The
winner of the first part of the Space Sail Race will be the
spacecraft first to fly by the moon at a distance below 10 000
km, which may take up to 2 years, and the second part by the
spacecraft first to fly by Mars at a distance less than 10 000
km, which may take up to 5 to 7 years.
The European entry will consist of an aluminium-coated mylar sail
of 100 x 100 meters. At the centre of the sail a truss is
attached by means of a joint with two degrees of freedom. A
service unit is attached to the other end of the truss. By
manipulating the attitude of the truss with hull with respect to
the sail, the location of the centre of mass of the spacecraft
can be changed with respect to the centre of pressure of the
solar radiation. In this way, the attitude of the spacecraft can
be manipulated. A spacecraft flight simulator model has been
developed for the first part of the race to study strategies for
controlling orbital flight and attitude.
Using this simulator, it was possible to develop a strategy which
will result in lunar fly-by in about 650 days, while earlier
studies gave a journey time of some 1100 days. The flight
simulator made it also possible to study the spacecraft
gyroscopic behaviour and the effects of torque caused by gravity
gradients.


Navigation of ERS-1 Along-Track Scanning Radiometer (ATSR) Images
[D.M. O'Brien, A.J. Prata]

The ERS-1 satellite, to be launched in may 1991, contains an
Along Track Scanning Radiometer, which measures the temperature
of the sea-surface. This instrument uses a conical scan beam,
which permits each point on Earth to be scanned twice: the first
time when the point passes the forward scan of the ATSR, the
second time, approximately two minutes later, when the point
passes the downward scan of the ATSR. Precise navigation of the
images of the ATSR require detailed modelling of the orbit and
the attitude of the satellite. However, simplified algorithms
to implement a navigational procedure will be required by the
user community, leaving the detailed calculations to ESA. The
article describes such procedures which enable the user to
predict position and velocity of ERS-1, to calculate latitude
and longitude of an ATSR pixel, and to calculate the time when
a target is under the forward or downward scan.


Investigations into Multipactor Breakdown in Satellite Microwave
Payloads
[A. Woode, J. Petit]

Multipactor is a discharge caused by the release of secondary
electrons. These secondary electrons are released by the impact
of free electrons accelerated by the electric field in RF
equipment in spacecraft. Multipactor discharge can have serious
effects on the short term and long term functioning of microwave
equipment. ESA has built a test facility in which multipactor
discharge can be studied. In parallel, a computer simulation has
been developed. Results of this study are a better understanding
of multipactor theory and the parameters that affect multipactor
discharge, and the ability to achieve multipactor free high-
power payload designs.

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

Date: 16 Mar 91 19:00:41 GMT
From: isis!scicom![e-mail]  (Bruce Watson)
Subject: Salyut 7 in Argentina


Spaceflight magazine (official publication of the British Interplanetary
Society) states:

"The Salyut 7 space station met its end shortly before 04.00 GMT on
February 7. According to the TASS news agency, the station plunged
into the Earth's atmosphere at latitude 34.9 degrees south,
longitude 63.8 degrees west. A statement from the Argentine Defence
Ministry said that debris fell in the Paymun and Catriel districts
in the Neuquen province and the adjacent area in the La Pampa and
Rio Negro Provinces.

Eye witnesses described how they could see "fiery rain" as the debris
from the space station burnt up. A fragment "the size of a washing
machine" crashed into the backyard of a house in Rosario, the
Bueno Aires Herald reported."

--
wats@scicom     | One of the things I like about this job is that I'm
                | never bothered by life-insurance salesmen.
                |                                      -- Red Adair

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

Date: 18 Mar 91 00:11:08 GMT
From: zaphod.mps.ohio-state.edu!swrinde!elroy.jpl.nasa.gov!zardoz.cpd.com!dhw68k!ofa123!p2112.f69.n233.z1.fidonet.org![e-mail]  (David Bloomberg)
Subject: Shuttle size


Well, I sort of asked this before, but didn't get any answers, so I'll come out
and just ask the question:

Does anyone know the weight of the U.S. Space Shuttle (including booster
rockets)?  If so, what is it?

Thanks.


--- msged 1.999.7
 * Origin: Religion doesn't belong on a Science Echo! (1:233/69.2112)


--
David Bloomberg
Internet: [e-mail]
Compuserve: >internet:[e-mail]
--------------------------------------------------------------------------

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

Date: 19 Mar 91 23:53:04 GMT
From: agate!bionet!uwm.edu!zaphod.mps.ohio-state.edu!rpi!news-server.csri.toronto.edu!utzoo![e-mail]  (Henry Spencer)
Subject: Re: railguns and electro-magnetic launchers

In article <[e-mail]> [e-mail] (John Prentice) writes:
>I thought the real problem was surviving the initial acceleration...
>... Has anyone ever attempted to
>launch a payload out of a EM launcher that is at all complicated, in the
>sense of having telemetry, etc... ?

Nobody's done this with an EM launcher.  However, it has been done many
times with old-fashioned chemical guns, starting with radar proximity
fuzes in WW2 and progressing to upper-atmosphere research instruments in
the 1960s with Project HARP.

(The proximity fuzes were particularly impressive because the electronics
in them used *vacuum tubes*...)
--
"[Some people] positively *wish* to     | Henry Spencer @ U of Toronto Zoology
believe ill of the modern world."-R.Peto|  [e-mail]  utzoo!henry

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

Date: 20 Mar 91 01:09:57 GMT
From: agate!bionet!uwm.edu!caen!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Magellan Update - 03/19/91


                         MAGELLAN STATUS REPORT
                           March 19, 1991

     The Magellan spacecraft and its radar system are performing nominally.
All of the STARCALS (star calibrations) and DESATS (desaturations) yesterday
were successful.

     Later today the weekly mapping command sequence, M1079, with its radar
control parameter and mapping quaternion files will be sent to the spacecraft.
Also being sent to the spacecraft today will be a command sequence to perform
Test #2 on the Flight Tape Recorder "A".

     If approved later today, the final files to reload AACS (Attitude and
Articulation Control Subsystem) Memory "B" will be sent tomorrow.  Spacecraft
engineers have determined the cause of the heartbeat loss counts and the
protected memory warnings observed last week while trying to reactivate
Memory B, so the process of restoring the full redundancy of the AACS memories
can now be completed.  The new on-board sequence includes fault detection which
will quickly isolate the memory in the event of a chip failure.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|      Ron Baalke         | [e-mail]
     | | | |  __ \ /| | | |      Jet Propulsion Lab |
  ___| | | | |__) |/  | | |___   M/S 301-355        | Change is constant.
 /___| | | |  ___/    | |/__ /|  Pasadena, CA 91109 |
 |_____|/  |_|/       |_____|/                      |

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

Date: 17 Mar 91 04:43:54 GMT
From: skipper![e-mail]  (Mary Shafer)
Subject: Re: Titan IV Launch - March 8, 1991

In article <[e-mail]> [e-mail] (Glenn A. Serre) writes:

>According to the Lompoc something-or-other, a Titan IV was launched from
>VAFB on March 8, 1991.  The payload was said by "space analysts" to be a
>Lacrosse.

Really early in the morning, because by 0530 the contrail/exhaust trail
had drifted so far east that I saw it in the east when I went out for
the paper.  Lancaster is about 100-120 miles east of Vandenberg.

They mentioned it on the Los Angeles news.

>The launch went great, and all parties appear to be satisfied.

Including me, because I scampered back in for my camera and got some
pretty nice pictures.


--
Mary Shafer   [e-mail]  ames!elxsi.dfrf.nasa.gov!shafer
         NASA Ames-Dryden Flight Research Facility, Edwards, CA
                    Of course I don't speak for NASA

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

Date: 11 Mar 91 10:36:00 GMT
From: agate!linus!philabs!ttidca!quad1!bohica!mcws!p0.f851.n102.z1.fidonet.org![e-mail]  (Nick Szabo)
Subject: Re: German conference highlights doubts about ESA's manned space plans

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: German conference highlights doubts about ESA's manned space plans
Message-ID: <[e-mail]>
Date: 11 Mar 91 02:36:00 GMT
In article <[e-mail]> [e-mail] (Andreas G. Nowatzyk) writes:

>True, but I read the original argument slightly differently: It is possible
>to design Solar Max, etc. for in-orbit repair by robots, which was not done.

I didn't mean this, but this is a good point.  Incidentally, Solar Max
did need special design changes to allow repair (as opposed to retrieval
and relaunch) by astronauts.  It would be interesting to compare the cost
of redesign for robotic vs. the cost of redesign for human repair, and
then factor in the costs of human EVA time vs. telerobotic repiar time.


>....For example, a lot of consumer equipment (VCRs & such) and
>some computer gear (Mac's, printers, etc.) are now routinely designed for
>robotic assembly. Lots of tiny details reqire attention: aviod screws,
>avoid round screw-in connectors, provide guide-paths for modules,
>snap-into-place things are king, locking mechanisms that require tools to
>push in several places are fine, but ones that require rotary action are not,
>avoid ill shaped objects like cable harnesses, ... nothing really fancy, but
>it is quite a departure from the way current space probes are designed.
>
>Furthermore, in-orbit repairs are limited to module swaps. It's hard to
>imagine someone replacing a 300+ pin surface mounted chip during EVA.

Good point.  Are there any large differences between design for robotic
and astronautic EVA repair?


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


--
: Nick Szabo - via FidoNet node 1:102/851 [phone]
: ARPA/INTERNET: [e-mail]
: UUCP: ...!{elroy!bohica,elroy!wciu,cit-vax!wciu}!mcws!851.0!Nick.Szabo
: Compu$erve: >internet:[e-mail]

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

End of SPACE Digest V13 #284
*******************