Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_3/V13_312.TXT

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Subject: SPACE Digest V13 #312

SPACE Digest                                     Volume 13 : Issue 312

Today's Topics:
      GEOMAGNETIC STORM INFORMATION UPDATE #2 - 24 MARCH
              Re: More cost/lb. follies
           Space Station Work Packages (Forwarded)

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
  should be sent to [e-mail], or, if urgent, to
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Date: Sun, 24 Mar 91 12:20:57 MST
From: [e-mail] (CARY OLER)
Subject: GEOMAGNETIC STORM INFORMATION UPDATE #2 - 24 MARCH
X-St-Vmsmail-To: st%"[e-mail]"


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

                       INFORMATIONAL MAGNETIC STORM UPDATE
                            Storm Alert Cancellation

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

                               19:00 UT, 24 March

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


ATTENTION:

     The geomagnetic storm is winding down now.  Geomagnetic activity began
settling down around 13:00 UT on 24 March.  A few low intensity minor storm
level perturbations have been observed, but nothing significant has occurred
now for over five hours.

     Geomagnetic storming peaked at severe storm levels between 03:42 UT
and 06:00 UT on 24 March.  Activity then became sustained at major storm
levels until approximately 10:00 UT.  Thereafter, activity decreased to
minor storm levels and faded gradually to generally active conditions by
18:30 UT.

     Reports of auroral activity have been received as far south as 36
degrees north latitude over North America.  Activity was reported from as
far south as southern Nevada to northern Texas to North Carolina.
Locations as far north as Alaska and northern Canada also witnessed
significant levels of auroral activity.

     The Boulder A-index for 18:00 UT on 24 March is 62, which is very near
the predicted levels and represents a moderate-intensity major geomagnetic
storm.  This storm has been classified as "Major."  High latitude A-indices
have been quite a bit higher (near and above 100).  The storming at these
latitudes has been classified as "Major to Severe." High latitude K-indices
peaked at 9, while middle latitudes peaked at 8.

     Satellite proton and PCA activity is gradually decaying, although
there will probably be several more days of satellite proton and PCA
activity (barring any further major flares).

     HF propagation conditions have improved significantly over the past
six hours.  Propagation is now rated fair to good over the middle
latitudes, while high and polar latitudes are still experiencing strong
PCA-related absorption with periodic blackout periods and very poor
propagation conditions.

     No reports of VHF auroral backscatter communications have been received
yet, although not all of the reports are in yet.  Conditions were favorable
for auroral communications on VHF frequencies over high, middle and northerly
low latitudes.

     Geomagnetic activity is not expected to intensify, although isolated
periods of minor (and possibly major) storm level fluctuations are still
possible during this post-storm period.  Activity can be expected to
increase slightly near local midnight, although widespread storming is not
likely to be observed.

     Auroral activity has decreased in intensity and latitudinal extent.
No significant low-latitude auroral activity is expected for tonight.
There is a small chance for some isolated northerly low latitude auroral
activity sightings, although this probability is quite low.  Locations
north of a line from central Oregon, central Idaho, northern Wyoming, south
Dakota, southern Minnesota, southern Wisconsin, southern Michigan, southern
New York and Conneticut will be more likely to witness further lower
levels of auroral activity tonight (late 24 March, local time).

     There is still a high risk for high intensity major solar flaring from
Region 6555.  A major class M5.6/2B flare was observed at 22:20 UT on 23
March (at S23E06), although this flare was not large enough to produce any
significant terrestrial impacts.  It was impulsive and fairly radio-quiet.

     There is a strong possibility for another major proton flare from this
region.  This region will remain capable of producing high terrestrial
impacts for the next four days.  Renewed proton and PCA activity is
possible if another proton flare occurs.  Additional magnetic storming and
low latitude auroral activity is possible if another major proton flare
occurs.  Watch for possible major flare alerts.

The following alerts have been cancelled:
   - MAJOR GEOMAGNETIC STORM ALERT
   - LOW LATITUDE AURORAL ACTIVITY ALERT
   - ELECTRICAL GEOMAGNETIC INDUCTION ALERT

The following alerts remain in progress:
   - SATELLITE PROTON EVENT ALERT
   - POLAR CAP ABSORPTION EVENT ALERT
   - POLAR RADIO SIGNAL BLACKOUT ALERT

The following warnings remain in progress:
   - POTENTIAL MAJOR SOLAR FLARE ALERT
   - POTENTIAL PROTON FLARE ALERT


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

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

Date: 20 Mar 91 21:17:19 GMT
From: sgi!shinobu!odin!schreiber![e-mail]  (Olivier Schreiber)
Subject: Re: More cost/lb. follies

In <[e-mail]> [e-mail] (Bob Pendleton) writes:

>What if you could build it any size you want? Could you do it then?
>Maybe you could.  Maybe this is a rediculous example. :-) Think about
>the cube-square law. If you can build any size you want then the cube
>square law can give you an enormous volume to structure ratio. Maybe
>good enough to build a stainless steel balloon.

In this case, I think the cube-square law does not apply.
Both volume and structure mass would grow as the cube of length scale:

For a spherical tank, with pressure P kept constant,
the force F on the greater cross section is F=P pi R^2
It must be balanced by the structure of thickness e and nominal
tension strength tau:
   P pi R^2 = e 2 pi R tau
Thus, e = P R / (2 tau)
The mass of the structure is M= 4 pi R^2 e
Thus,
M= 4 pi R^3 P/(2 tau)

For a nominal P pressurized tank of tensile strength tau, the mass is
proportional to R^3, just as the mass of the fuel.


>--
>              Bob Pendleton, speaking only for myself.
>   [e-mail] or decwrl!esunix!bpendlet or utah-cs!esunix!bpendlet

>                         Tools, not rules.
--

Olivier Schreiber  Technical Marketing [e-mail] [phone] MS/7L580
Silicon Graphics Inc.,  2011 North Shoreline Blvd. Mountain View, Ca 94039-7311
      The philosophy of one century is the common sense of the next.

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

Date: 22 Mar 91 07:31:45 GMT
From: mips!sdd.hp.com!elroy.jpl.nasa.gov!jato!mars.jpl.nasa.gov![e-mail]  (Ron Baalke)
Subject: Space Station Work Packages (Forwarded)

SPACE STATION FREEDOM WORK PACKAGES


Mike Simmons    March 21, 1991
Marshall Space Flight Center, Huntsville
(Phone:  [phone])

SPACE STATION FREEDOM WORK PACKAGE ONE

        NASA's Marshall Space Flight Center (Work Package 1) has responsibility
for:  the design and construction of Space Station Freedom's pressurized
laboratory and habitation modules, the working area and living quarters for
Freedom's crew members; the logistics modules, used for resupply and storage;
node structures, which connect the laboratory and habitation modules; and
certain subsystems internal to the pressurized modules, including the
environmental control and life support, thermal control, electrical
distribution, communcations and audio/video systems.

UNITED STATES LABORATORY AND HABITATION MODULES

    The U.S. Laboratory Module and Habitation Module will each be 14.5 feet
in diameter and 27 feet in length.  These dimensions allow the modules to be
built, outfitted, integrated and tested on the ground and then transported into
Earth orbit in the Space Shuttle cargo bay and connected to the nodes and other
space station structures.

    The U.S. Lab will include 15 experiment racks and 13 systems racks.
During the station's Man-Tended Capability (MTC) phase, this orbiting
laboratory will serve as the site for microgravity research and will be capable
of conducting that science in both a manned mode, when astronauts are visiting
the station via the Space Shuttle, and in an unmanned mode.  When station
construction reaches Permanently Manned Capability (PMC) and four astronauts
remain onboard for extended periods, life sciences research will be conducted
to learn more about the affects of living in space and to help prepare mankind
for returning to the Moon and exploring the planets.

    With the addition of the Habitation and International Laboratory
modules, the station's module racks will expand to as many as 45.  When
station construction reaches PMC and the Hab Module is added, Freedom's
environmental control and lifes support systems will provide closed-loop water
recycling capability.  The crew's food and other supplies will be carried to
the station via a logistics module which is transported in the Space Shuttle's
cargo bay.  During the Man-Tended Capability phase, astronauts visiting Freedom
will live on the Shuttle.


Kyle Herring
Johnson Space Center, Houston
(Phone:  [phone])

SPACE STATION FREEDOM WORK PACKAGE TWO

    NASA's Johnson Space Center (Work Package 2) Space Station Freedom
Program Office (SSPO) is responsible for the design, development, verification,
assembly and delivery of the Work Package 2 flight elements and systems, which
include: the pre-integrated truss assembly; propulsion assembly; Mobile
Servicing System transporter; resource node design and outfitting; external
thermal control; data management; communication and tracking; extravehicular
systems and guidance; navigation and control systems, and the airlock.

    JSC SSPO is also responsible for the attachment systems required by the
Space Shuttle for periodic visits.  In addition, JSC SSPO provides technical
direction to the Work Package 1 contractor via the Marshall Space Flight Center
for the design and development of all manned space subsystems.

PRE-INTEGRATED TRUSS ASSEMBLY

    The pre-integrated truss assembly is the Space Station Freedom
structural framework to which the modules, solar power arrays and mobile
transporter will be attached.

PROPULSION ASSEMBLY

    The propulsion assembly will be used to adjust or maintain the orbit
of Space Station Freedom to ensure it remains at the required altitude.  Work
Package 2 has responsibility for the overall propulsion system.

MOBILE TRANSPORTER SYSTEM

    The Mobile Servicing System will be a multi-purpose mechanism equipped
with a transportable robotic arm used to help assemble and maintain Space
Station Freedom.  The Work Package 2 contractor will build the mobile
transporter; Canada will provide the robotic arm and a special-purpose
dexterous manipulator.

RESOURCE NODES

    The resource nodes house most of the command and control systems for
the Space Station as well as being the connecting passageways for the
habitation and laboratory modules.  Work Package 2 will outfit the node
structures provided by Work Package 1 to accomplish the objectives of each
node.

EXTRAVEHICULAR ACTIVITY SYSTEMS

    Extravehicular activity (EVA) systems includes equipment such as the
extravehicular mobility unit (EMU) or spacesuit; provisions for communication;
physiological monitoring and data transmission; EVA crew rescue and equipment
retrieval provision and EVA procedures.  An airlock for use by crew members
performing EVA will also be designed as part of Work Package 2.

EXTERNAL THERMAL CONTROL

    The external thermal system provides primary cooling and heat rejection
to control temperatures of electronics and other Space Station hardware located
throughout the facility.

ATTACHMENT SYSTEMS

    In concert with the Orbiter Projects Office, Work Package 2 is
responsible for the development of systems which will permit Space Shuttle
mating with the Space Station.

GUIDANCE, NAVIGATION AND CONTROL SYSTEM

    The GN&C system is composed of core system and traffic management
functions.  The core system function provides attitude and orbital state
maintenance; supports the pointing of the power system and thermal radiators;
accomplishes periodic reboost maneuvers, and provides Space Station attitude
information to other systems and users.  The traffic management function
provides for controlling all traffic in the area around the Space Station,
including orbiter mating operations and trajectories determination of
vehicles and objects which may intersect the orbit of the Space Station.

COMMUNICATIONS AND TRACKING SYSTEM

    The communications and tracking (C&T) system is composed of six
subsystems: space-to-space communications with crew members during space walks
(EVA); aboard the Space Shuttle, and with visiting vehicles such as the
European Space Agency man-tended free-flyer; space-to-ground communications
through the Tracking and Data Relay Satellite System (TDRSS) to ground data
networks; internal and external voice communication through the audio
subsystem; internal and external video requirements through the video
subsystem; management of communication and tracking resources and data
distribution through the control and monitor subsystem; and navigation data
through the tracking subsystem.

DATA MANAGEMENT SYSTEM

    The data management system (DMS) provides the hardware and software
resources that interconnect onboard systems, payloads, and operations to
perform data and information management.  Functional services provided by DMS
include data processing, data acquisition and distribution, data storage, and
the user interface to permit control and monitoring of systems and experiments.

ASSURED CREW RETURN CAPABILITY

    Crew safety is an essential consideration in the development of the
Space Station to the permanently-manned configuration.  A major system failure
aboard the Space Station, injuries or illness may require the return of crew
members to Earth during a period when the Space Shuttle is unavailable.  NASA's
Johnson Space Center has responsibility for conducting definition-phase studies
of an Assured Crew Return Vehicle (ACRV) which would be used to supplement the
Space Shuttle in such circumstances.

WORK PACKAGE TWO CONTRACT

    McDonnell Douglas Space Systems Company's Space Station Division heads
a team completing the work for Work Package 2.  Major subcontractors include
GE Aerospace Government Communications Systems Division, Honeywell Space
Systems Group, IBM Federal Sector Division, Lockheed Missiles and Space Company
and Astro Aerospace.  GE is producing communications and tracking, Honeywell is
working on stabilization and controls, IBM is designing the data management
systems, Lockheed is developing thermal control, power management and
distribution, and extravehicular activity systems, and Astro is responsible for
the mobile transporter system.


Mary Ann Peto
NASA Lewis Research Center
Cleveland, Ohio
(216/433-2902)

SPACE STATION FREEDOM WORK PACKAGE  FOUR

    NASAUs Lewis Research Center, Cleveland, Ohio, is responsible for the
end-to-end electric power system for the Freedom space station.  This includes
defining the system architecture and providing the solar arrays, batteries, and
power management and distribution hardware and software.  The power system
includes power generation and storage, and the management and distribution of
power to the final user interface.   The electric power system is required to
have the capability to deliver 22 kW of electric power for a man-tended
configuration, and 65 kW for a permanently manned configuration with growth
to 75.0 kW.

POWER GENERATION

    Initially, power for Freedom will be provided by flexible, deployable
solar array wings.  This configuration minimizes the complexity of the assembly
process by taking advantage of the technology previously demonstrated on Space
Shuttle flights.  Each 39-by-122 foot wing consists of two blanket assemblies
covered with solar cells.  These are stowed in blanket boxes which are attached
to a deployment canister.  Each pair of blankets is to be deployed and
supported on a deployable mast.  A tension mechanism will supply tension to
the blanket as it reaches complete extension.  The entire wing will be tied
structurally to the pre-integrated truss by means of the beta gimbal assembly.

    In order to provide the power needed during the period of space station
assembly, two solar wings, the energy storage system and electronics components
are assembled into a power module scheduled to be carried up on the first space
staion assembly flight.  These two wings along with engergy storage will
provide 22 kW of power.  The remaining power modules with two solar array wings
per module will be delivered on oribit after the man-tended configuration is
reached.

POWER STORAGE

    Nickel Hydrogen (Ni-H2) batteries will store the energy produced by
the solar arrays.  A battery pack is made up of 76 Ni-H2 cells, wiring harness,
and mechanical/thermal support components.  On discharge, the battery provides
power to the primary bus for eclipse periods.  Ni-H2 batteries were selected
for low weight and high reliability.

POWER MANAGEMENT AND DISTRIBUTION (PMAD)

    The 160/120 volt DC PMAD system is designed specifically to meet the
high electric power system requirements of the space station.  It is user
friendly and can accommodate a wide variety of user loads delivering controlled
power to many scattered loads.  The high voltage DC power system was selected
to provide high efficiency, low cost, and safe operations.
      ___    _____     ___
     /_ /|  /____/ \  /_ /|      Ron Baalke         | [e-mail]
     | | | |  __ \ /| | | |      Jet Propulsion Lab |
  ___| | | | |__) |/  | | |___   M/S 301-355        | Change is constant.
 /___| | | |  ___/    | |/__ /|  Pasadena, CA 91109 |
 |_____|/  |_|/       |_____|/                      |

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

End of SPACE Digest V13 #312
*******************