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From: [email protected] (Jon Leech)
Newsgroups: sci.space.tech,sci.space.science,sci.answers,news.answers
Subject: Space FAQ 07/13 - Mission Schedules
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Date: 17 Sep 1996 15:52:33 -0400
Organization: University of North Carolina, Chapel Hill
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Archive-name: space/schedule
Last-modified: $Date: 96/09/17 15:40:34 $

   Compilation copyright (c) 1994, 1995, 1996 by Jonathan P. Leech. This
   document may be redistributed in its complete and unmodified form. Other
   use requires written permission of the author.

SPACE SHUTTLE ANSWERS, LAUNCH SCHEDULES, TV COVERAGE

   SHUTTLE LAUNCHINGS AND LANDINGS; SCHEDULES AND HOW TO SEE THEM

   Steven S. Pietrobon ([email protected]) posts a compressed
   version of the Space Shuttle launch manifest to sci.space.shuttle. This
   includes dates, times, payloads, and information on how to see launches
   and landings. These files are in

           ftp://audrey.levels.unisa.edu.au/space/shuttle.man
           ftp://audrey.levels.unisa.edu.au/space/shuttle.txt

   For the most up to date information on upcoming missions, call toll-free
   (800)-KSC-INFO (800-572-4636) or (407) 867-INFO (867-4636) at Kennedy
   Space Center.

   Official NASA shuttle status reports are posted to sci.space.news
   frequently.


   WHY DOES THE SHUTTLE ROLL JUST AFTER LIFTOFF?

   The following answer and translation are provided by Ken Jenks
   ([email protected]).

   The "Ascent Guidance and Flight Control Training Manual," ASC G&C 2102,
   says:

       "During the vertical rise phase, the launch pad attitude is
       commanded until an I-loaded V(rel) sufficient to assure launch tower
       clearance is achieved. Then, the tilt maneuver (roll program)
       orients the vehicle to a heads down attitude required to generate a
       negative q-alpha, which in turn alleviates structural loading. Other
       advantages with this attitude are performance gain, decreased abort
       maneuver complexity, improved S-band look angles, and crew view of
       the horizon. The tilt maneuver is also required to start gaining
       downrange velocity to achieve the main engine cutoff (MECO) target
       in second stage."

   This really is a good answer, but it's couched in NASA jargon. I'll try
   to interpret.

   1)  We wait until the Shuttle clears the tower before rolling.

   2)  Then, we roll the Shuttle around so that the angle of attack
       between the wind caused by passage through the atmosphere (the
       "relative wind") and the chord of the wings (the imaginary line
       between the leading edge and the trailing edge) is a slightly
       negative angle ("a negative q-alpha").  This causes a little bit of
       "downward" force (toward the belly of the Orbiter, or the +Z
       direction) and this force "alleviates structural loading."
       We have to be careful about those wings -- they're about the
       most "delicate" part of the vehicle.

   3)  The new attitude (after the roll) also allows us to carry more
       mass to orbit, or to achieve a higher orbit with the same mass, or
       to change the orbit to a higher or lower inclination than would be
       the case if we didn't roll ("performance gain").

   4)  The new attitude allows the crew to fly a less complicated
       flight path if they had to execute one of the more dangerous abort
       maneuvers, the Return To Launch Site ("decreased abort maneuver
       complexity").

   5)  The new attitude improves the ability for ground-based radio
       antennae to have a good line-of-sight signal with the S-band radio
       antennae on the Orbiter ("improved S-band look angles").

   6)  The new attitude allows the crew to see the horizon, which is a
       helpful (but not mandatory) part of piloting any flying machine.

   7)  The new attitude orients the Shuttle so that the body is
       more nearly parallel with the ground, and the nose to the east
       (usually).  This allows the thrust from the engines to add velocity
       in the correct direction to eventually achieve orbit.  Remember:
       velocity is a vector quantity made of both speed and direction.
       The Shuttle has to have a large horizontal component to its
       velocity and a very small vertical component to attain orbit.

   This all begs the question, "Why isn't the launch pad oriented to give
   this nice attitude to begin with?  Why does the Shuttle need to roll to
   achieve that attitude?"  The answer is that the pads were leftovers
   from the Apollo days.  The Shuttle straddles two flame trenches -- one
   for the Solid Rocket Motor exhaust, one for the Space Shuttle Main
   Engine exhaust.  (You can see the effects of this on any daytime
   launch.  The SRM exhaust is dirty gray garbage, and the SSME exhaust is
   fluffy white steam.  Watch for the difference between the "top"
   [Orbiter side] and the "bottom" [External Tank side] of the stack.) The
   access tower and other support and service structure are all oriented
   basically the same way they were for the Saturn V's.  (A side note: the
   Saturn V's also had a roll program.  Don't ask me why -- I'm a Shuttle
   guy.)

   I checked with a buddy in Ascent Dynamics.  He added that the "roll
   maneuver" is really a maneuver in all three axes: roll, pitch and yaw.
   The roll component of that maneuver is performed for the reasons
   stated.  The pitch component controls loading on the wings by keeping
   the angle of attack (q-alpha) within a tight tolerance.  The yaw
   component is used to determine the orbital inclination.  The total
   maneuver is really expressed as a "quaternion," a grad-level-math
   concept for combining all three rotation matrices in one four-element
   array.


   HOW TO RECEIVE THE NASA TV CHANNEL, NASA SELECT

   NASA SELECT is broadcast by satellite. If you have access to a satellite
   dish, you can find SELECT on SpaceNet 2, Transponder 5, C-Band, 69
   degrees West Longitude. SELECT has been moved from Satcom F2R to a
   satellite even further to the east, and is apparently even more
   difficult to receive in California and points west. During events of
   special interest (e.g. shuttle missions), SELECT is sometimes broadcast
   on a second satellite for these viewers.

   If you can't get a satellite feed, some cable operators carry SELECT.
   It's worth asking if yours doesn't.

   The SELECT schedule is found in the NASA Headline News which is
   frequently posted to sci.space.news. Generally it carries press
   conferences, briefings by NASA officials, and live coverage of shuttle
   missions and planetary encounters. SELECT has recently begun carrying
   much more secondary material (associated with SPACELINK) when missions
   are not being covered.


   AMATEUR RADIO FREQUENCIES FOR SHUTTLE MISSIONS

   The following are believed to rebroadcast space shuttle mission audio:

       W6FXN  - Los Angeles
       K6MF   - Ames Research Center, Mountain View, California
       WA3NAN - Goddard Space Flight Center (GSFC), Greenbelt, Maryland.
       W5RRR  - Johnson Space Center (JSC), Houston, Texas
       W6VIO  - Jet Propulsion Laboratory (JPL), Pasadena, California.
       W1AW Voice Bulletins

       Station    VHF     10m     15m     20m    40m    80m
       ------   ------  ------  ------  ------  -----  -----
       W6FXN    145.46
       K6MF     145.585                         7.165  3.840
       WA3NAN   147.45  28.650  21.395  14.295  7.185  3.860
       W5RRR    146.64  28.400  21.350  14.280  7.227  3.850
       W6VIO    224.04          21.340  14.270
       W6VIO    224.04          21.280  14.282  7.165  3.840
       W1AW             28.590  21.390  14.290  7.290  3.990

   W5RRR transmits mission audio on 146.64, a special event station on the
   other frequencies supplying Keplerian Elements and mission information.

   W1AW also transmits on 147.555, 18.160. No mission audio but they
   transmit voice bulletins at 0245 and 0545 UTC.

   Frequencies in the 10-20m bands require USB and frequencies in the 40
   and 80m bands LSB. Use FM for the VHF frequencies.

   [This item was most recently updated courtesy of Gary Morris
   ([email protected], KK6YB, N5QWC)]


   SOLID ROCKET BOOSTER FUEL COMPOSITION

   Reference: "Shuttle Flight Operations Manual" Volume 8B - Solid Rocket
   Booster Systems, NASA Document JSC-12770

   Propellant Composition (percent)

   Ammonium perchlorate (oxidizer)                     69.6
   Aluminum                                            16
   Iron Oxide (burn rate catalyst)                     0.4
   Polybutadiene-acrilic acid-acrylonitrile (a rubber) 12.04
   Epoxy curing agent                                  1.96

   End reference

   Comment: The aluminum, rubber, and epoxy all burn with the oxidizer.

NEXT: FAQ #8/13 - Historical planetary probes

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