SPACE SHUTTLE ANSWERS, LAUNCH SCHEDULES, TV COVERAGE
SHUTTLE LAUNCHINGS AND LANDINGS; SCHEDULES AND HOW TO SEE THEM
Shuttle operations are discussed in the Usenet group sci.space.shuttle,
and Ken Hollis (gandalf@pro-electric.cts.com) posts a compressed version
of the shuttle manifest (launch dates and other information)
periodically there. The manifest is also available from the Ames SPACE
archive in SPACE/FAQ/manifest. The portion of his manifest formerly
included in this FAQ has been removed; please refer to his posting or
the archived copy. For the most up to date information on upcoming
missions, call (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
(kjenks@gothamcity.jsc.nasa.gov).
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 Satcom F2R, Transponder 13, C-Band, 72
degrees West Longitude, Audio 6.8, Frequency 3960 MHz. F2R is stationed
over the Atlantic, and is increasingly difficult to receive from
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
(g@telesoft.com, 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