Because this site
may be considered controversial by some people, out of respect for the
astronauts and their families no photos of the astronauts or attempted
memorials will be posted on this site. The names of the astronauts
will only be used when absolutely necessary to the investigation.
The simplest
explanation of what occurs during a Space Shuttle reentry is a careful balance
of three things.
The rate of
descent.
Aerodynamic heating.
Decreasing
forward velocity.
If the shuttle descends too quickly through an
increasingly dense atmosphere it will suffer extensive thermal damage that may
burn through the skin of the orbiter resulting in its loss. If its forward
speed is not decreased sufficiently or if it has not descended to the correct
altitude at the right time, it will not be in the proper position for landing
and will either have to land at an alternate site or crashed into an unpopulated
area after the crew has escaped.
Eqn.
A1
Reentry
Flight Control Parameters
1.)
1Heating Rate Equation
Qmax <
70 Btu / Ft.2-Sec.
k
=
4.4695199x10-9
r=
Gas Density (Slugs / Ft.3) V
=
Velocity
(Ft. / Sec.)
2.)
Normal Acceleration Equation
an
=L
cos
a
+
D
sina
anmax <
2.5 G
L =
Aerodynamic Lift.
See Eqn. A3-1 D
= Aerodynamic
Drag. See Eqn. A3-2
a
= Angle
of Attack (Degrees)
3.)
Dynamic Pressure Equation
q
=1/2rV2
qmax <
300 psf
r=
Gas Density (Slugs / Ft.3) V
=
Velocity
(Ft. / Sec.)
Determined empirically during
Space Shuttle flights and is based on a one dimensional adiabatic
steady state heating model. It is the heating rate for
stagnation regions of the shuttles surface during high Mach number
reentry atmospheric flight.
Eqn.
A2
Six
Degrees of Freedom Equations for Space Shuttle Reentry
rc=
Distance from center of
Earth to vehicle C.G. (Ft.)
Q= Geodetic
Longitude.
F= Geodetic
Latitude.
Vr=
The Earth's relative
velocity. (Ft./Sec.)
g= Flight
path
angle. (Deg.)
Y= Velocity
Azimuth
angle. (Deg.)
w
= Earth's
rotation
rate. (Deg./Sec.)
s
= Vehicle
bank
angle. (Deg.)
Eqn.
A3
Lift
and Drag Equations
5.) CL0= -0.14490
6.) CL1= -0.02924
7.) CD0= -0.07854
8.) CD1= -6.15920(10)-3
9.) CD2= -6.21408(10)-4
L= Aerodynamic Lift.
D= Aerodynamic
Drag.
r
= Gas
Density (Slugs / Ft.3)
V
=Velocity
(Ft. / Sec.)
Sref
= Shuttle
reference surface area (2,690 Ft.2)
m
= Mass
of shuttle (203,000 lbs.)
CL= Coefficient
of Lift. (Mach > 2.5)
CD= Coefficient
of Drag. (Mach > 2.5)
a
= Angle
of attack (Degrees)
To help keep the aerodynamic heating
to a minimum the shuttle has an extremely shallow rate of descent. A
typical reentry
starts with the shuttle at an altitude of 76 miles and a distance of 5,063 miles
from the landing site this is equal to a rate of descent of only 1.5%,
see
"Reentry Aerodynamics", in the document,
Shuttle_Flight_Properties.pdf.
However, simply flying with a constant shallow rate of descent isn't enough due
to changes in the properties of the atmosphere as you drop through it as well as
local weather conditions. To accomplish the feat of keeping temperature
distance and velocity in perfect balance, the shuttle also has a suite of
complex guidance software that takes it through a few fairly simple flight
maneuvers designed to keep all of those factors in perfect balance. By
taking sensor reading from different areas of the shuttle and the outside
atmosphere for temperature and pressure, as well as being fed other data such as
current altitude and distance from the landing site, the shuttle's computers
calculate the correct time to perform the maneuvers. A human pilot
can not take all this data and make all the calculations fast enough to control the shuttle through the critical phases of reentry. It has been estimated
that increasing the rate of descent just a few percent at the wrong time could
lead to a worst case scenario. This is why the shuttle must be on auto
pilot for most of reentry and also why the avionics system is so important that
it has a total of five identical flight computers and no less than two backup
units for every other flight critical system.
Clicking
on the image to the left will bring up an enlarged map of U.S. Time
Zones with a table defining how to calculate the times for the different
zones.
A
similar map showing time zones around the world is also available.
Eyewitness accounts of the Columbia's last few minutes indicate that the shuttle
was losing material from very early on during reentry. Some initial
accounts report debris shedding being spotted by ground observers at 5:45 a.m. PST This
was
probably not possible when the shuttle was high over the middle of the Pacific
Ocean. Other accounts and at least one video tape made in California at
5:53 a.m. indicated that debris was coming off the shuttle at that point.
Some witnesses said it looked like the shuttle was, "dropping flares",
as it flew over California. At this time the shuttle was at an altitude of
233,450 Ft. and had just barely reached its maximum temperature. This would
tend to indicate that damage was being done to the shuttle well before 5:53 a.m.
and well before the maximum temperatures were reached. This is also the
point where temperature anomalies and sensor problems started to be
noticed.
Deorbit
burn:
At
08:15:30 a.m. EST(13:15:30 GMT) the
Columbia initiated de-orbit burn for 2 minutes and 38 seconds to position itself
for Entry Interface (EI).
STS-107
Reentry Data
Pre De-orbit burn data
Orbit
Inclination: 39°
Location (latitude/longitude in
degrees): -35.00000 S. / 85.0000 E.
Time:
13:15:00 GMT
Altitude:
929,016 Ft. (175.95 statute
miles)
Velocity:
17,496 mph (25,661 Ft./Sec.)
Post De-orbit burn data
Orbit
Inclination: 39°
No
change
Location (latitude/longitude in
degrees): -33.58333 S. / 98.1667 E.
Change:
757.39 statute miles
Time:
13:17:38 GMT
Burn
duration: 2:38
Altitude:
929,016 Ft. ( 175.95 statute
miles)
No
change
Velocity: 17,319.7
mph (25,401 Ft./Sec.)
Change in velocity:
- 176 mph
Entry
Interface (EI):
Entry Interface then began at 13:44:09 GMT. Entry Interface is defined as
the point when the shuttle has attained, or descended to, an altitude of 400,000 Ft.
per the
Reentry document on
the NASA Human Space Flight Website.
STS-107
Reentry Data
Entry
Interface
Location (latitude/longitude in
degrees): 30.83313 N. / -167.5564 W.
Change 7580.00 statute miles
Time:
13:44:09 GMT
Change 00:26:31
Altitude:
395,010 Ft. (74.81 statute
miles)
Change 534006 Feet
Velocity:
Mach 24.56 x (speed of sound @ Alt. = 1,431 Ft./Sec.)
=
35,145 Ft./Sec. (23,963 mph)
1Change
+9,774 Ft./Sec. (6665 mph)
Reentry
Angle setup between De-orbit Burn and EI = 0.7644°
After EI the angle is typically
adjusted to between 1˚ and 1.5˚.
It is unknown why
the increase in velocity between the end of the deorbit burn and
EI is so great. If it is not an error it may by a byproduct
of the entry process. The value will be checked further
until it is confirmed.
Reentry
flight maneuvers:
The shuttle crew
initiated the OPS 304 guidance program at 5 minutes prior to EI per the STS-107
reentry instructions, see the flight documents
Entry_check_list_STS-107_a.pdf
and Entry_check_list_STS-107_b.pdf. OPS 304
is a closed loop guidance program designed specifically to control the shuttle
through the peak heating phase of reentry from EI+400 to
EI+1200, see
Fig. A10 for the definition of the peak heating region. OPS 304 uses
closed loop feedback to determine when and where to initiate the Roll / bank
maneuvers that reduce the rate of descent and bleed off the excessive forward
speed. Because the RCS Roll jets are
deactivated at Qbar = 10 psf the shuttle uses the elevons and Yaw jets to perform
maneuvers. The basic operation of the Orbital Maneuvering System (OMS) and RCS are described
on page Technical Overview of the Space Shuttle Orbiter.
Fig. A1
Fig.
A1 to the left depicts a typical Space Shuttle reentry. The area inside the red rectangle represents the
final approach and landing phase shown inFig.
A3. If Columbia had made it to this part of reentry it would
have had to make a 270˚ right hand turn in order to land on Kennedy Space
Center's runway 33 at 9:16 EST. as was anticipated.
Fig. A2
Fig.
A2 shows the two typical flight paths across the United States for
landing at Kennedy Space Center (KSC) depending on the shuttle's orbital
inclination. For STS-107 the orbital inclination was 39˚ and the
associated flight path would have been the Maximum Westerly Approach.
Based only on this diagram, it would appear that the
Columbia was significantly off course during the STS-107 reentry when
compared to what is considered to be the typical nominal Maximum Westerly
Approach flight path. However, it is unknown if the Space Shuttle
follows the exact same flight path every time or if the path is dependent
on the particular circumstances of the flight. Therefore the
Columbia may not have been off course at all but the possibility is
presented here only for discussion purposes.
Fig. A3
Fig.
A3 shows how the Space Shuttle makes its final approach to land at KSC
on runway 33 which was the designated runway for STS-107. What is
most notable is the 270˚ right turn the shuttle needs to make in order to
land.
Detailed
Description of Flight Maneuvers in the Entry Subphase of Space
Shuttle Reentry Taken from
the NASA Space Shuttle reference manual section on reentry.
Also available here
Space
Shuttle Reentry.
Guidance performs
different tasks during the 1Entry,
2TAEM
and 3Approach and Landing
subphases. During the 1Entry
subphase, guidance attempts to keep the
orbiter on a trajectory that provides protection against
overheating, overdynamic pressure and excessive normal
acceleration limits. To do this, it sends commands to flight
control to guide the orbiter through a tight corridor limited on
one side by altitude and velocity requirements for 4Ranging(in order to make the runway) and orbiter control
and on the other side by thermal constraints. 4Ranging
is accomplished by adjusting 5Drag Acceleration to
velocity so that the orbiter stays in that corridor. 5Drag
Acceleration can be adjusted primarily in two ways: by
modifying the 6Angle of Attack, which changes the
orbiter's cross-sectional area with respect to the airstream, or
by adjusting the orbiter's 7Bank Angle, which affects
lift and thus the orbiter's 8Sink Rate into denser
atmosphere, which in turn affects drag. Using 6Angle of
Attack as the primary means of controlling drag results in
faster energy dissipation with a steeper trajectory but violates
the thermal constraint on the orbiter's surfaces. For this reason,
the orbiter's 7Bank Angle(Roll control)
is used as the primary method of controlling drag, and thus 4Ranging,
during this phase. Increasing the 9Roll Angle
decreases the vertical component of lift, causing a higher 8Sink
Rate. Increasing the 10Roll Rate raises the
surface temperature of the orbiter, but not nearly as drastically
as does an equal 6Angle of Attack command. The
orbiter's 6Angle of Attack is kept at a high value
(40°) during most of this phase to protect the upper surfaces
from extreme heat. It is modulated at certain times to ''tweak''
the system and is ramped down to a new value at the end of this
phase for orbiter controllability. Using bank angle to adjust 5Drag
Acceleration causes the orbiter to turn off course.
Therefore, at times, the orbiter must be rolled back toward the
runway. This is called a 11Roll Reversal
and is
commanded as a function of azimuth error from the runway. The
ground track during this phase, then, results in a series of
S-turns.
Technical Footnotes:
Entry:
The first subphase of reentry from EI-5 min. to where
vehicle is traveling at 2500 Ft./Sec. (83,000 Ft.
altitude).
TAEM
(Terminal Area Energy Management):
The second subphase of reentry begins at 2500
Ft./Sec. to altitude under 10,000 Ft.
Approach
and Landing: The third subphase of reentry from under 10,000 Ft. altitude and the shuttle
lined up with runway and ends with orbiters weight
on nose gear after touchdown.
Ranging: The process where the shuttle's guidance system
continuously calculate the required altitude and
velocity based on distance to the runway.
Drag
Acceleration: The physical flight parameter adjusted to
accommodate the results of the Ranging calculations,
(Optimum value is 33_Ft./Sec.2
.Adjusted using either Angle of Attack or Bank
Angle).
Angle
of Attack: Angle between an aircrafts longitudinal axis and
its direction of travel.
Bank
Angle: Rotation about vehicle velocity vector
(direction of travel).
Sink
Rate: An aircraft rate of descent into the atmosphere.
Roll
Angle: Rotation about vehicle longitudinal X axis.
Roll
Rate: Change in vehicle Roll angle with time.
Roll
Reversal: Turns shuttle back towards runway to correct
Bank Angle error.
UPDATE:
12/20/2003
A
transcript of voice communication during reentry between the shuttle crew
and Mission Control Huston is in the document
STS-107_Reentry_Text_J.pdf.
In this transcript at
13:41:35
Commander Rick Husband states' "Two
minutes to entry interface.", to the other crew members. Then
again at 13:43:42
Commander Husband says, "OK. We're just past EI.".
If an official time for entry interface is not given then we know that it
occurred somewhere in the 7 seconds between
13:43:35/42, the time
13:43:37
could be picked arbitrarily and made the official time of EI for use on
this site. The problem is that an official time for EI is given and
it's 13:44:09, 32 seconds after the point where Commander Husband tells
his crew that they just passed EI.
It
could simply be assumed that Commander Husband checked his watch for the
time not realizing it was off by 32 seconds or that Commander Husband was
simply in error. However several of the astronauts, Husband, McCool
and Clark who are all veterans of at least one other shuttle mission, make
statements about seeing plasma out of the front and side windows after
13:43:37 and well before 13:44:09. If the time at which Columbia
reached EI was changed after the loss of the shuttle as an effort to cover
up something that happened to Columbia during reentry, the reason for the
change cannot be found. Since the Columbia was traveling at Mach 25
before EI the 32 seconds translates into 217 miles of travel over open
empty ocean with no discernable observations or data points which may have
required the 32 seconds to prove their legitimacy.
After
looking at
Fig. A10
and the STS-107 Ground Track documents, it does not appear that a 32 second shift would have significantly
changed any of the data that creates the chart, (any changes in velocity,
altitude or angle of attack would be negligible to nonexistent).
Based on the analysis done on Chris Valentine's
visual data, the shuttle was where it was supposed to be when it was
supposed to be there much later in reentry showing that other location
data was not affected by a 32 second time shift. EI may have been
moved to accommodate the substitution of STS-5 telemetry data for STS-107
data as an early step in a cover up process when little to nothing was
know about the shuttle data. Because many of the
data analysis posted on this site were done assuming that EI occurred at
13:44:09, that value will be maintained for the time being.
Any
place where a total time after EI is referred to such as EI+500, 32
seconds can be added to give the time after EI per the cockpit intercom
transcript (EI+532).
Theory
Under Consideration:
If
a cover up exists within the Columbia investigation, then the 32 second
shift in EI time may be connected to the additional 32 seconds of data
taken from the 1OEX data recorder after LOS occurred at
13:59:32. Most likely all of the error messages and aerosurface
position data were shifted 32 seconds forward along with the time of EI
so that there would be 32 seconds of data available after LOS. However,
this has not been proven.
05/15/2004
Based on the only definition for Entry Interface that has been found, it has been determined
that the time of EI was shifted by 32 seconds specifically to alter the
reentry timeline. Entry Interface is defined as the point
when the shuttle has descended to an altitude of 400,000 Ft.
per the Reentry
document on the
NASA Human Space Flight Website. The official altitude at EI
has consistently been given as 395,010 Ft. for STS-107, (in direct
conflict with NASA's own definition). Therefore, EI occurred
at the earlier time, 13:43:37, with the 5,000 Ft.
difference accounting for the 32 seconds. Much if not all of the
telemetry data that is time stamped between 13:59:32 and 14:00:00 should
be moved back 30 to 32 seconds with shuttle breakup then confirmed as
occurring at LOS. The effect this time shift has on other
telemetry data throughout the STS-107 Timeline and Ground Track
documents is currently unknown.
There are currently no plans to
change the times of any events or telemetry data contained in the
various tables and sections of this site. The 32 second shift
would not seriously affect any of the key findings and it is impossible
to know how much data would need to be shifted if none at all.
If the time shift does have an effect on any of the conclusions it will
be noted.
If we had to state a time and location where Columbia's
fate was sealed for the STS-107 mission, it would not be somewhere over
the Atlantic shortly after launch on January 16, 2003. It would
instead be at 13:47:32(EI+203) over the middle of the
Pacific Ocean at an altitude of 298,446 Feet during her reentry, see
Fig.
A4.
What makes this location so suspect is that it was the
end of both Laurel Clark's crew cabin video and marked the end of any
and all significant voice communications with Mission Control Houston. The
Space Shuttle had not lost voice contact with Mission Control to such an
extent since the Tracking and Data Relay Satellite TDRS system was put in
place in the early nineties. Typically the shuttle's avionics system
would find a suitable backup for the voice transmitter and bring it on
line, but that didn't happen during STS-107.
By 13:50:00 data
transmissions from the shuttle were being affected as well. Within
two minutes after that the bits of data that were getting through
indicated off nominal aero increments that were not being corrected by
Columbia's avionics systems.
After
once again closely scrutinizing the transcript of verbal communications
during reentry that has been carefully reconstructed in the document,
STS-107_Reentry_Text_J.pdf,
a fact not previously noticed is a complete lack of voice communication
between the shuttle crew and Mission Control Houston after 13:47:32
(EI+203).
Although Mission Control personnel are buzzing with the many strange and
random anomalous events that begin some time after 13:51:00, there are no
conversations with the crew about the failures. The transcript
contains some verbal ques from Mission Control personnel that may be
attempts the contact the crew, but with the exception of Commander Rick
Husbands two different moments when he is able to broadcast some cryptic syllables
such as, "Bu" or "Uh", the loss of verbal
communication continues to the end.
The
STS-107
GTrack Rev 15.pdf and
STS-107-Timeline-Rev15.xls
documents only list brief communication blackouts that result in loss of
data but do not indicate a total loss of air to ground verbal
communication. An interesting note is that 13:47:32 is also the
exact time that Laurel Clark's camcorder failed marking the end of the crew cabin
video released by NASA. Because the
camcorder failed completely at the exact same time that verbal communications
were lost, the two events may be
related.
07/23/2004
Many people have written in claiming that besides
the two times that Rick Husband was able to send those very brief
messages to Mission Control after 13:47:32 he can clearly be heard
saying, "Feeling that heat Mission Control", at about 13:48:00.
To my knowledge this was never part of the transcript. When
William Harwood, the creator of the transcript
STS-107_Reentry_Text_J.pdf,
was questioned about any additional voice communications besides
what he put in the document his response was as follows.
There were no other transmissions
from the crew beyond what you see in my transcript or in NASA's
version. All ascent/entry air-to-ground traffic is broadcast
in the open (even during classified military missions) and if
there had been something else, we'd have all heard it. I
don't have any doubt about that at all.
Just FYI, something like this came
up after Challenger, i.e., rumors of on-board recordings that went
beyond the official ICOM transcript. Those stories were
equally bogus, in my opinion.
William
Harwood
CBS News
Table
A1 lists all of the communication loss events between the shuttle and
mission control which resulted in the missing data shown in the Time Line
documents. Each event includes
the time,
duration and what hardware was involved. What is not shown in the chart is
the complete loss of voice communication after 13:47:32. Although this was
the most significant anomalous communication failure none of the official
investigation documents mention anything about it. It is unknown why
the shuttle continued to transmit telemetry data and not voice communications.
A possible reason is that voice communications are carried on the S-Band PM two
ways system while data is typically carried on the S-Band FM system which
transmits only and cannot receive. Another possibility is that what ever
affected electronic systems onboard the orbiter had a much greater affect on
microphone components than other systems. See,
Technical
Overview of the Space Shuttle Orbiter (Avionics and Communications Systems),
Communications Systems.
This news story confirms how uncommon such a loss
of communications is at this point in our space program, "The Shuttle Blackout Myth Persists".
The crew cabin
video released by NASA is said to have come from a video tape in a camcorder
which survived breakup and was found in the debris field. This video is available for viewing on various news sites, CBS
news Space Shuttle reentry video. It can also be downloaded from
Inside KSC.com here Crew
Cabin Video 100 MB.
Table A1 The following communication failures
occurred during reentry
Event
Time
(GMT)
Duration
(Sec.)
Transmission
antenna affected
Remarks
1
13:50:00
1
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
2
13:50:04
2
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
3
13:50:16
4
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
4
13:50:25
3
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
5
13:50:42
1
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
6
13:52:09
6
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
7
13:52:25
1
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
8
13:52:29
2
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
9
13:52:49
6
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
10
13:53:32
2
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
11
13:54:14
8
Upper Left S-Band PM Antenna
(S-Band Ant. No. 1).
Unexpected Return Link Comm.
drop-out.
12
13:54:26
-
-
Comm. switched to
upper right antenna.
13
13:55:33
2
Upper Right S-Band
PM Antenna
(S-Band Ant. No. 2).
Unexpected Return Link Comm.
drop-out.
14
13:56:00
3
Upper Right S-Band
PM Antenna
(S-Band Ant. No. 2).
Unexpected Return Link Comm.
drop-out.
15
13:56:55
2
Upper Right S-Band
PM Antenna
(S-Band Ant. No. 2).
These breaks
in the communications between the Columbia and Mission Control are all listed as
anomalous events for reentry. However, the communications systems
including the transmitting and receiving hardware as well as all of the antennas
are all located well away from the left wing and do not have any associated
cable harnesses that run through that general area. Therefore a breach in
the left wing does not explain any of the anomalies that occurred with the
shuttle communications system that morning.
The next events were the beginnings of sensor anomalies.
The STS-107_Event_Sequence.pdf
document from NASA contains diagrams that show the time and
location of the various sensor failures and off nominal readings. The
document STS-107_Sensor_Failure.pdf contains similar information but is an older version. Note
that both documents were released before the
OEX data recorder was found and
therefore neither contains the
OEX data that has been determined to be
questionable and most likely fabricated. Because many of these events are
mentioned during reentry by Mission Control personnel it may be possible to
verify the data by comparing the events to the transcript of voice
communications in the
STS-107_Reentry_Text_J.pdf document.
Fig. A6
Fig. A6 is from
STS-107_ Event_Sequence.pdf
released by the C.A.I.B. on 03/14/2003. The image has been
modified slightly to provide more information in a compact format.
Fig. A6 is a modified version of the image that is published with
STS-107_Event_Sequence.pdf.
The diagram graphically shows the approximate X - Y location of all the
affected sensors grouped and color coded by their associated wiring cable harnesses.
Table
A2 is a summary of sensor activity from EI to LOS (Los Of Signal)
that is taken from the same document as the image. The numbers on
the sensors in the image correspond to the numbers in the column labeled
Sensor Ref. No. and are the same as
used in,
STS-107_Event_Sequence.pdf.
The numbers do not correspond to the order of events.
The
most puzzling of the sensor anomalies were those monitoring the supply
water dump nozzles and the vacuum vent near the forward fuselage.
The suspected breach in either RCC panels 8 or 9 is too far from these
to have effected the units or their sensors and wiring.
Fig. A6 shows the temperature sensor cable harness for hydraulic systems 1, 2 and 3
return lines as having a close proximity to the left wing leading edge near
RCC panels 7, 8 and 9, the exact location of the wing breach that exists in
the C.A.I.B.'s failure scenario. This is why the
investigators concluded that the wiring harness was attacked by heat which
caused the anomalies that were recorded, (seeTable A2;
Events 1, 7, 8, 9, 10 and 14).
It has been shown on this site
that the Space Shuttle left wing wiring diagrams such as that shown above in
Fig. A6were created after the
Columbia disaster for use with the official investigation. These diagrams
portray sensor cable routings that are not accurate. The
sole purpose of these diagrams is to further legitimize the existence of a
breach in the leading edge of the shuttle's left wing and point directly to it
as the source of reentry sensor electrical anomalies.The
differences between the wiring diagrams doctored by the C.A.I.B. and the actual
wire and cable routing used on all the shuttles is
clarified in detail in one of the Space Shuttle technical sections.
See,Technical
Overview of the Space Shuttle Orbiter (Wings, Tail, Body Flap and
Control Surfaces),
Wiring
harness routing.
Table
A2 The following anomalous
sensor readings and failures
occurred during reentry
Event
Time
(GMT)
MSID
1Sensor
Ref. No.
Sensor
affected by event
Remarks
1
13:52:17
V58T1703A
1
Left Main Gear Brake Line Temp D
Off nominal temp rise.
2
13:52:32
V62T0439A
V62T0440A
33 & 34
Supply Water Dump Nozzle A/B
Off nominal temp rise.
3
13:52:32
V62T0519A
V62T0520A
35 & 36
Waste Water Dump Nozzle A/B
Off nominal temp
rise
4
13:52:32
V62T0551A
37
Vacuum Vent
Off nominal temp rise.
5
13:52:41
V58T1700A
2
Left Main Gear Brake Line Temp A
Off nominal temp rise.
6
13:52:41
V58T1702A
3
Left Main Gear Brake Line Temp C
Off nominal temp rise.
7
13:52:56
V09T1006A
4
Left Inboard Elevon Lower Skin Temp
Off nominal temp
downward trend.
8
13:52:59
V09T1006A
4
Left Inboard Elevon Lower Skin Temp
Sensor goes offline.
9
13:53:03
-
-
Left outboard Elevon wide-band accelerometer
(10 Gs peak to peak)
signal saturation
indicative of failure
10
13:53:10
V58T0394A
5
Hyd. Sys. 3 Left Outboard Elevon Actuator
Return Line Temp
2Sensor goes offline.
11
13:53:11
V58T0157A
6
Hyd. Sys. 1 Left Inboard Elevon Actuator
Return Line Temp
2Sensor goes offline.
12
13:53:34
V58T0193A
7
Hyd. Sys. 1 Left Outboard Elevon Actuator
Return Line Temp
2Sensor goes offline.
13
13:53:35
V62T0439A
V62T0440A
33 & 34
Supply Water Dump Nozzle A/B
Return to normal
temp rise rate.
14
13:53:35
V62T0519A
V62T0520A
35 & 36
Waste Water Dump Nozzle A/B
Return to normal
temp rise rate.
15
13:53:35
V62T0551A
37
Vacuum Vent
Return to normal
temp rise rate.
16
13:53:36
V58T0257A
8
Hyd. Sys. 2 Left Inboard Elevon Actuator
Return Line Temp
2Sensor goes offline.
17
13:54:10
V58T1701A
9
Left Main Gear Brake Line Temp B
Off nominal temp rise.
18
13:54:20
-
-
Start of slow Elevon trim change on left wing
(Time approx. +/- 10 sec.)
counteracts buildup
of aero drag.
19
13:54:22
V34T1106A
10
Mid. Fuselage Left Body Line Temp
Off nominal temp rise.
20
13:54:22
V09T1724A
28
Left Aft Fuselage Sidewall
Off nominal temp rise.
21
13:54:24
V58T0405A
11
Left Main Gear Strut Actuator Temp
Off nominal temp rise.
22
13:54:53
V51T0574A
18
Main Landing Gear Left Hand Outboard Wheel
Temp
Off nominal temp rise.
23
13:55:12
V58T0842A
13
Hyd. Sys. 3 Left Hand Forward Brake Switch
Valve Rtn. Line Temp
Off nominal temp rise.
24
13:55:41
V34T1118A
27
Mid. Fuselage Port (Left) Sill Longeron Temp
Off nominal temp rise.
25
13:56:16
V58T0125A
12
Left Main Gear Uplock Actuator Unlock Line
Temp
Off nominal temp rise.
26
13:57:19
V51P0570A
17
Main Landing Gear Left Hand Outboard Tire
Pressure 1
Off nominal temp rise.
27
13:57:24
V51P0572A
22
Main Landing Gear Left Hand Outboard Tire
Pressure 2
Off nominal temp rise.
28
13:57:28
V09T1002A
15
Left Lower Wing Skin Temp
Sensor goes offline.
29
13:57:43
V09T1024A
14
Left Upper Wing Skin Temp
Sensor goes offline.
30
13:57:54
V58T0841A
16
Hyd. Sys. 2 Left Hand Forward Brake Switch
Valve Rtn. Line Temp
Off nominal temp rise.
31
13:58:38
V51P0570A
17
Main Landing Gear Left Hand Outboard Tire
Pressure 1
Sensor goes offline.
32
13:58:39
V51T0574A
18
Main Landing Gear Left Hand Outboard Wheel
Temp
Sensor goes offline.
33
13:58:40
V51P0571A
19
Main Landing Gear Left Hand Inboard Tire
Pressure 1
Sensor goes offline.
34
13:58:43
V51P0573A
22
Main Landing Gear Left Hand Inboard Tire
Pressure 2
Shows pressure rise.
35
13:58:48
V51T0575A
20
Main Landing Gear Left Hand Inboard Wheel Temp
Sensor goes offline.
36
13:58:48
V51P0573A
21
Main Landing Gear Left Hand Inboard Tire
Pressure 2
Sensor goes offline.
37
13:58:54
V51P0572A
22
Main Landing Gear Left Hand Outboard Tire
Pressure 2
Prior to going off
line the official report states that the sensor "Shows wire
damage trend" with no other description.
The
only sensors listed in the Event Sequence document that remained nominal
while data was still being transmitted had the reference numbers 23, 24,
25 and 26 and were attached to the following devices,
Hyd. Sys.
3 Left Inboard Elevon Actuator
Return Line Temp
Hyd. Sys.
2 Left Outboard Elevon Actuator
Return Line Temp
Hyd. Sys. Left Inboard Elevon Actuator Temp
Hyd. Sys. Left Outboard Elevon Actuator Temp
Per STS-107_Sensor_Failure.pdf the 2 sensors which showed the greatest temperature increases were
number 11 at 6°/min. for a total of 5 minutes, (+30°F), and number 17 at 14°/min for 1
minute and 38 seconds, (+22.87°F). This was not anywhere near enough heat to cause
damage to Columbia's left wing. In addition to this some of the sensors
showed temperature decreases before they went off line.
Avionics failures:
Nothing is mentioned in either the STS-107 Timeline or STS-107 Ground Track
documents about failures of the General Purpose Computers (GPC's) or any other
of the flight control systems or avionics equipment onboard the Columbia.
The space shuttle has five general purpose computers that are all identical.
Four of the computers are loaded with the same software for guidance, navigation
and control which is produced by PASS. The PASS software is broken down
into OPS programs that control everything the space shuttle does from launch to
wheel stop. The fifth computer is loaded with
Backup Flight Software (BFS) that is produced by a different company. This software is only used in the
event that the four main computers are off line. The BFS can be initiated either by another
GPC or manually by the pilot.
The final report on the Columbia disaster produced by the
C.A.I.B. traces all anomalous events during the reentry of STS-107 to a breach
in one of the leading edge RCC panels of the left wing. This report states
the breach as being in panels 7, 8 or 9 and assumes that it is a 12 to 14 inch
wide hole in the top part of the panel, see
Fig. A6. It has already been shown
that the official investigation altered the location of sensor wires to help
legitimize the breached wing scenario, see the
Sensor failure section above and
the technical section on
Wiring
harness routing. The following detailed analysis of what was
happening to Columbia's flight control system between
13:47:00 and 14:00:00 also
indicates extensive attempts to force the evidence to follow the breached wing
scenario. This is done by ignoring important data or distorting other data
as well as the results of technical analysis. When all of the data is
considered and analyzed from an objective point of view, the cause of the
Columbia disaster appears to lead in the direction of multiple system failure
rather than external damage.
The earliest know "off nominal"
external event, (the nature of this event is never
explained), during the STS-107 reentry occurred at
13:51:19. Prior to this there was some type of multi system
failure at 13:47:32, see
Fig.
A4. After this the
reentry flight was plagued by ever increasing off nominal Yaw and Roll
aero-moments. At 13:51:46 the Time Line and Ground Track documents contain
the following entry,
Inertial sideslip angle (Beta) goes and stays Negative until LOS
While the magnitude of the observed Beta is not outside the flight history (41G
& 42), the almost linear negative ramp prior to the first Roll reversal is not
consistent with other flights reviewed. This is consistent with a negative
rolling and yawing torque on the vehicle.
The
interpretation of the above statement is that the value of this sideslip angle
is no better or worse than what has been measured in previous flights and is
therefore considered to be within the nominal range. However, the fact
that this negative Beta or negative Yaw continues with no attempt by the
shuttle's Digital Auto Pilot (DAP) to correct the flight path is not normal. The C.A.I.B.'s
explanation for the negative Yaw is that the breach on the leading edge of the
left wing resulted in excessive aerodynamic drag on the left side only,
forcing the shuttle to turn in that direction. If we continue to follow
the C.A.I.B.'s scenario, we can assume that the only thing wrong with the Columbia when she reentered the
atmosphere was the wing breach. Therefore
all of the orbiters other systems should be without damage and functioning
normally. One could then only assume that the drag force related to the
wing breach went beyond the ability of the shuttle's flight control system to compensate
and reestablish the correct flight path. However, the fact is that the DAP
itself made absolutely no attempt to reorient the shuttle.
An analysis of the control surface motions and RCS jet firings
occurring between 13:51:46 and 13:59:30 listed in Table A3 do
not appear to be an attempt to correct the flight path.All of the
events that occurred during that period of 7 minutes and 44 seconds are brief,
random and unrelated. The only real attempt to correct Columbia's
attitude did not occur until 13:59:30 when the shuttle's autopilot
suddenly shut down and the RCS Yaw jets fired for a full 8 seconds in an obvious
attempt to correct the negative Yaw angle and bring the orbiter back under
control. Unfortunately the calculations done in Technical Article TA-A2
shows that the 8 second jet firing overcorrected the negative Yaw to a full 90°
positive Yaw placing the shuttle with the left wing facing fully windward.
The error messages near the end of the Time Line referring to the Left RCS
system, L RCS LEAK and L RCS PVT, would seem to indicate
that there was no chance of using the Left RCS Jets to re-correct the positive
Yaw. The result of this calculation would not be provable except for a close analysis
of the Colony Video seen in Technical Article TA-A3 which appears to show the Columbia
for the few seconds between the Yaw jet firing and orbiter breakup flying
sideways with the left
wing still intact and facing windward against the hypersonic flow.
The left wing disintegrated first because it was
exposed to the hypersonic flow in a manner that exceeded its design limits, not
because a breach in the leading edge created a weak spot that became exploited.
We also know that the Yaw and Roll trends did not continue until LOS, and that
the RCS jets were powerful enough to counter a drag force from the left wing if
it existed.
The inability of a space shuttle to make a simple course
correction during any point in reentry is an indication that the full array of 5
General Purpose Computers GPC's failed simultaneously. It is also an
indication of partial or full corruption of the main flight software routines as
well as the backup flight software. The design incorporating 5 identical
GPC's as well as backup flight software is in place to negate the possibility
that a space shuttle is ever left without flight critical avionics.
Something completely unexpected and unaccounted for attacked the hardware
onboard the shuttle so quickly and completely that not one of the astronauts or
any of the flight engineers at Mission Control were aware of the consequences.
By observation it appears that whatever happened to the Columbia began at
approximately 13:47:30, see
Fig.
A4,with the severest extent of
the damage complete between 13:50:00 and
13:51:00. That is the defining line between normal
reentry flight
operations and the complete breakdown of critical avionics systems.
Fig. A7
Fig. A7
is a visual definition of sideslip.
As the Space Shuttle descends through the atmosphere it reaches a point
where significant increases in atmospheric density result in a much
greater rate of aerodynamic heating. This heating effect is
controlled by slowing down the rate of descent and bleeding forward
speed as possible. This is accomplished through the use of flight
maneuvers.
The typical shuttle reentry involves 4 Roll maneuvers and 4 Roll Reversals. The
Roll maneuvers causes sideslip which results in the
orbiter being off course. The Roll reversal
maneuvers are performed to put the shuttle back on its
proper flight path.
Fig. A8
Fig. A8
describes how the negative Beta is controlled and used to roll into the
first flight maneuver.
Another method for slowing down the shuttle's rate of descent and
airspeed is by flying with a very large Angle of Attack (AOA). The AOA must be maintained at
40°
from EI through the peak heating region. This angle
is difficult to hold and is part of the Digital Autopilot
(DAP) reentry program. If the autopilot is disabled
the shuttle would level out very quickly resulting in a
faster descent.
Because of this extreme AOA the lower surface of the
orbiter takes the brunt of the heat load during reentry. Therefore
the entire bottom of the shuttle is covered with the heavy duty black
tiles.
There is also a more natural and provable explanation for the negative Yaw
trend which the official report attributes to the leading edge wing breach.
During reentry the Digital Auto Pilot (DAP) running the OPS-304 reentry flight
control and guidance program maintains the Angle of Attack (AOA) at 40° and
calculates the correct time to initiate the flight maneuvers. The first
flight maneuver which is a Roll to the right was initiated at
13:49:32
and is started by lowering the left elevons a few degrees. Because the AOA is different from any other
aircraft, the result of this command to the aero surface is a negative Yaw
rate and a positive Roll rate or a roll to the right. The maneuver was
initiated just after the multi system failure began at
13:47:30,
and just prior to what seems
to be its completion at
13:50:00.
Normally the Yaw and Roll would be controlled so the maneuver could be
completed but the flight control systems may have become too damaged. A
good indication that the maneuver was not completed is that the time of
completion is missing throughout the final report
and all associated documents. An incomplete Roll Maneuver
would have left the Columbia with the left elevon extended downward by a few
degrees resulting in a constant negative Yaw rate and positive Roll rate as shown in
Fig. A9. Therefore it is a distinct possibility that the Yaw and
Roll trends were the result of an uncompleted flight maneuver.
Another and far more
serious problem resulting from the loss of flight control and especially the DAP
that early in reentry would be the inability to maintain the AOA at 40°, see
Fig. A8
above.
The shuttle's natural aerodynamic tendency is to level out flat if nothing is
constantly maintaining the AOA at 40°. If no flight maneuvers are
performed during reentry and the shuttle flies with the AOA or Pitch angle
= 0° it will descend far too fast through the atmosphere and be subject to
extreme thermal attack on the TPS. The descent flight path of the space
shuttle should look something like the altitude curve of the chart in
Fig.A10. When the
space shuttle sets itself up for reentry it initially enters the atmosphere with
an angle of descent that may seem very small but is essentially the angle that
would cause the shuttle to intersect the Earth at its landing location.
The angle is usually around 1°, STS-5 happened to be 1.24°. Without any
additional input from the flight control system the shuttle will descend
straight through the atmosphere without stopping the descent to bleed off some
of its forward speed. This is what is happening in
Fig.A10 while the
shuttle is passing through the peak heating region. The official
investigation didn't say much about the Angle of Attack except that it didn't
seem like a problem for them.
Fig. A9 is a graphic from one of the C.A.I.B. technical presentations that
were held once or twice a month to bring the press up to date on the
progress of the investigation. The graphic has been altered slightly
with the addition of the red lines and text indicating event times and
descriptions. Because the chart has no units and no detailed
explanation in the accompanying report text, its exact meaning and
relationship to Columbia's attitude are unknown. Its only value is
in showing Roll and Yaw trends over the course of reentry.
Table
A3 lists all of the RCS jet firings during reentry along with changes
in position of the control surfaces, left and right elevons, bodyflap and
speedbrake, (blue text relates to control surfaces and RCS Jet firings). All of
the data in Table A3
comes from
STS-107-Timeline-Rev15.xls
which also lists times when certain flight maneuvers were made.
These flight maneuvers are also listed in the table for comparison with other data.
The flight data used by the C.A.I.B. and which
appears in the official final report also contains another glaring
discrepancy. The
Time Line and Ground Track documents list a time that the first flight
maneuver, a Roll to the right, was initiated as being 13:49:32,
but a time for the completion of the maneuver is not stated, see the
preceding paragraph. The documents then list another flight maneuver
which is a Roll
Reversal initiated at 13:56:30 and completed at 13:56:55. However, the chart in
Fig. A9 indicates
that the off nominal Yaw and Roll trends continued throughout reentry including
the period of time when the Roll reversal was performed. Therefore these two statements from the official final
report are in stark contradiction to one another. Either the Columbia
performed flight maneuvers during reentry, or, it continued yawing and rolling
in the same directions as the chart in
Fig. A9 below shows. Both statements cannot be true. The
addition of the second flight maneuver was probably an early attempt to make
the STS-107 reentry appear more normal up to a point.
Technical Article A1
Aero Moment Definition and its Effect on Flight Control
An Aero-Moment, sometimes also called an Aero-Torque,
is simply a way of describing the leverage that is required to steer an
aircraft such as the Space Shuttle. For instance moving control
surfaces such as the Space
Shuttle's left elevons down into the airflow will result in an uneven
force couple that will have a tendency to turn or rotate the aircraft to the left
about its center of gravity, (negative Yaw), and also result in a
positive Roll.
An Aero-Moment may also be the result of damage to one of the aircrafts
surfaces that disrupts its aerodynamics. This damage causes a drag
force that is located some distance from the aircrafts center of gravity
having an effect similar to the movement of a control surface altering the
course and attitude. It is
then up to the pilot or autopilot to calculate the value of the damage
induced Aero-Moment and determine the required corrective action.
Other factors such as wind may alter the attitude of an aircraft and or
force it to drift off course.
For measuring course and attitude changes
the Space Shuttle has three different types of gyroscopic sensors which
collectively detect motion in any of the six
degrees of freedom. Data from the sensors is sent to the
GPC's where the Flight Control
software calculates the magnitude of the required restorative moment and decides how
to respond. Whether the corrective action takes
the form of firing the corresponding RCS Jets or movement of the
appropriate control surface depends on the phase of reentry flight.
The following sensors detect course and attitude
changes,
Inertial Measurement Units(IMU's) Senses the vehicle's attitude in inertial space relative
to the flight path.
Rate Gyro Assemblies(RGA's) Detects linear motion along any of the three
primary X, Y or Z axis.
The graph of
Fig. A9 represents Aero-Moment coefficients calculated by the
shuttle's flight control software using off nominal attitude and course
values detected by the gyroscopic sensors as described above.
Attitude and course errors may be the result of many different external
events, therefore the sensors onboard the Space Shuttle do not directly
record Aero-Moment data. The avionics system uses only the
knowledge of how the shuttle's attitude and course have changed to
calculate an Aero-Moment sufficient to counter the changes and restore the
orbiter to its proper course and attitude. The
flight control system then sends a signal to one or more of the control
surfaces ordering it through some degree of rotation. Exactly how
much the control surfaces must rotate to create the required Aero-Moment
depends on the atmospheric density which is a function of aircraft
altitude.
AltTA-A1_AeroMoments.htmhough the Digital Auto Pilot was unable to send the command to correct
the errors to either the RCS system or the control surface actuators, the
data was still transmitted to Mission Control.
Fig. TA-A1-1
The main
motions controlled by the shuttle's RCS jets and various control
surfaces are Yaw
(rotation about the Z
axis),Pitch(rotation about the
Y
axis) and
Roll
(rotation about the X
axis).
Whatever change in attitude is
being made, or if multiple changes are being made simultaneously, any
movements of the shuttle will be made about it's center of gravity.
The Yaw diagram to the left shows how closely the
Yaw angle is related to the Sideslip angle Beta. Pitch angle is also
directly related to the Angle of Attack.
Fig. TA-A1-2
Fig. TA-A1-3
The diagram below is a key to indicate how the
various groups of RCS thrust jets affect the shuttle's rotation in
the three primary rotational axis Yaw, Pitch and Roll.
Thrust from forward and aft jets can also be combined to increase the
rate of rotation if required.
RCS jets may be used for translational motion as well when Fore and
Aft jets on the same side are combined. This will cause the shuttle to
translate along any of the three primary axis while holding its Yaw, Pitch and
Roll angles constant.
Location Designations For RCS
Thrusters
In engineering terminology a "moment" is a term that represents
the leverage created by a force and a lever arm of some particular
length. Documents
produced by the C.A.I.B. often use both terms, moment and torque,
to describe the same action. Although the two terms have
similar meanings, torque is most often used to describe the power
output of a rotating shaft or flywheel.
In the case of an Aero-Moment the
force would be the extra drag created by the change in position of
a control surface, the thrust from a maneuvering jet or damage to
the surface of an aircraft which affects its aerodynamics. The location of
the force would be at the centroid of the control surface, the jet
thrust cone or the point of damage. The lever arm would be
the distance from the force to the aircrafts center of gravity.
The conclusions reached by the official investigation revolve
around the existence of a heavily damaged left wing leading edge RCC panel 7, 8 or 9. The
official final report gives the distinct impression that the graphed data shown
in
Fig. A9
represents off nominal Aero-Moment coefficient data resulting
directly from the damaged RCC panel. This data often appears in different
formats throughout the final report.
As explained previously in this section, the shuttle's
avionics system calculates a restorative moment based on off nominal attitude
and flight path data recorded by the
gyroscopic sensors. It was also stated that the changes which occur in the
attitude and course parameters may be due to several different factors affecting
the shuttle's flight path. Therefore the shuttle could not have determined
the off nominal Aero-Moment coefficients due to a damaged RCC panel because the
avionics system had no way of knowing that the panel was damaged. The
system can only determine the total off nominal Aero-Moments due to all factors
including any possible damage without knowing the extent or contribution of any
one factor in particular.
The diagram below
Fig. TA-A1-4
explains the mechanics of Aero-Moments and in particular the Yaw moment that
would be created by damage to the left wing leading edge at RCC panel 7, 8 or 9.
The Plan View (upper left)describes how the Yaw Moment
drives the negative Yaw rate.
[ MYaw
=
(FDx)(DY) ]
View B - Bshows how the Roll moment
drives the positive Roll rate.
[ MRoll
=(FDz)(Dz)
]
For these cases it is impossible to predict the Aero-Moment
values. Although the distance from the force line of action to the
shuttle's C.G. is known, the magnitude of the drag force originating in the RCC
panel is impossible to determine. This is due to the initial nature of the
damage as well as the fact that the official scenario states that the size of
the damaged area steadily increases throughout the course of reentry.
Fig. TA-A1-4
Because the negative Yaw trend may be one of the most
important factors resulting in the breakup of Columbia the diagram of
Fig. TA-A1-5
complements
Fig. TA-A1-4
by describing the Yaw moments resulting from movement of the left
elevons and or firing of the right rear RCS Yaw Jets. In the case
of the elevons the moment is created by the differential between the
rotation angle of left and right. If all 4 elevons are already
rotated down by 2° from 0° then the left side would need to be
rotated a total of 5° from 0° to achieve the elevon rotation of 3°.
Fig. TA-A1-5
The Yaw Moment Coefficient CN
typically relates to an angle of rotation of a control
surface such as the elevons. Depending on some other variables such as
atmospheric density etc. this coefficient can be used with a graph or an
equation to determine the total Yaw Moment. An important observation within the diagram is that the drag force located at
the damaged area,
FDx
has a line of action that coincides with the force that would be induced by the
deflection of the left elevon. Therefore it is equally possible that the
Yaw and Roll trends of
Fig. A9 that lead to the breakup of Columbia were caused by movement
of the control surfaces and not damage resulting from a foam
debris strike during launch and ascent.
Another dimension of interest is from the center of the RCS Yaw Jets to
the Center of Gravity (DRCS
or also DX) is
595.220". Each RCS Jet
provides 870
vacuum pounds of thrust. Our countering moment based on
the amount of thrust from the Yaw Jets and distance to the C.G. can then
be calculated.
The moment created by operating
all four RCS Yaw Jets is then
MRCS = (870)(595.220)(4) = 172,613
Ft.-Lbs.
For two jets MRCS = 86,307 Ft.-Lbs.
The conclusion of the reentry data and event analysis
conducted in the sections above is that a significant disconnect
existed between the attitude changes that were being recorded by the
Columbia's avionics system and the shuttle's response to that
information. The various RCS Jet firings that occur prior to the 8
second continuous RCS burn during the
reentry do not appear to be a response to the negative Yaw trend.
The firing durations are too short and occasionally the wrong jets are
being fired. It also does not appear that any commands were sent
to the shuttle's control surface actuators that were attempts to correct
the errors. Therefore the most
important issue resulting from the analysis of the Yaw and Roll data
along with any control surface movements was the inability of the flight
control system to correct the compounding Yaw and Roll errors.
Although the source of the Yaw and Roll moments may be ambiguous,
resulting from
either wing damage or elevon movement,
the loss of flight control after 13:51:00 (EI+411)
appears to be a major event. The cause
of the avionics failure onboard Columbia must be determined.
Event times may be moved back by
32 seconds, (see
Update
05/15/2004).
Technical Article A2
Columbia's Final Attitude Changes
Factors affecting Columbia's
final attitude:
The official report does not contain any
information on Columbia's final attitude before breakup, but the
sudden application of Mach 18 aerodynamic forces laterally to the
shuttles airframe is the only stress mode that would result in the
sudden and catastrophic breakup that occurred. Based on
Fig. A9 which shows the shuttle as having a constant negative Yaw Moment the
initial conclusion would be that Columbia's final Yaw Angle would have been -90˚
(the shuttle traveling at a right angle to the flight path with the
right hand side facing windward).
Some observed factors relating to the Columbia's
final attitude:
Extensive right hand Yaw Jet firing after 13:59:00. (RCS Yaw Jets R2R and R3R fired for a full 8 seconds in an
attempt to counter the increasing negative Yaw Rate)
1Amateur video with close up taken from Colony
Texas, (near Dallas). (Video appears to shows the Columbia traveling at a right angle to the
flight path with the left hand side facing windward or Yaw = +90˚
in complete contradiction to what
Fig. A9 would lead us to believe)
Debris field data indicates that the shuttle's
left wing broke up before the right. (At Yaw = +90˚
the right wing would be protected while the left is exposed to
the Mach 18 airflow, see
Fig. B3)
Based on these observations the effects of the Yaw Jet firing need to be
determined.
The
Plots of either Roll Moment Vs. Time or
Yaw Moment Vs. Time as the
shuttle performs flight maneuvers should typically look similar to the
5 graphs of
Fig. TA-A2-1. The data should show a repeating pattern that changes from positive to
negative as the shuttle rolls left then right and back to the left
again.
These diagrams may be used to confirm that
no flight maneuvers were performed during STS-107. When
comparing the diagrams to
Fig. A9 it is obvious that
Fig. A9 does not contain any areas that resemble the curves to the
left, even during the period where a roll reversal is said to have
occurred.
A set of graphs were derived from empirical data
before STS-1 to predict how the RCS Yaw Jets would
control the shuttle's yaw rate during reentry. The derived data matched the
actual flight data very closely.
Fig. TA-A2-2 contains two sets of data from a Mach 24 bank
maneuver. The graphs are analyzed here to determine if the
relationship between Yaw Jet firing and Yaw Rate can be used to derive
a function that can predict the shuttle's yaw rate for yaw jet firings
with different parameters.
The increase in Yaw Rate based on the firing of 2
right rear Yaw Jets for a total of 5.5 seconds is 3˚ per second.
Because the relationship between Yaw Rate and time is linear
it can be used as a Rate Function to determine how other firing
durations would increase or decrease the Yaw Rate.
0.2727˚ per second/duration of jet firing
(seconds)/No. of jets
When the shuttle is in an
environment free of gravity and atmosphere this Yaw Rate would
continue until the opposing Yaw Jets are fired to counter it.
During atmospheric flight other factors such as the use of control
surfaces and drag forces would either increase or decrease the Yaw
Rate once the jets have stopped firing. Therefore, during
atmospheric flight it is nearly impossible to determine how the Yaw
Rate changes after the Yaw Jets stop firing unless the value is
recorded.
The derived Rate Function can then be used to
determine how Yaw Jet firing events affected Columbia's
attitude during reentry. The most significant jet firing would
be events 38 and 39 on
Table A3where Yaw Jets R2R and R3R fired
for nearly 8 seconds continuously. All of the other jet firing
events were too short of duration to have an effect on the shuttle's
trajectory.
These values are then inserted into the derived
Rate Function to find the final Yaw Rate after jet firing,
0.2727 * 8 * 2 = 4.36˚
per second positive yaw
By multiplying the final Yaw Rate
produced by the jet firing with the period of time that Yaw Rate was
maintained and adding to this the initial Yaw angle whether it was
positive or negative will give the final Yaw angle of the shuttle
produced by that Yaw Jet firing.
See explanation for RCS
thruster location and direction of vehicle travel at bottom of
section.
Columbia's final attitude:
Columbia acquired a negative Yaw Rate of unknown
value early in reentry due to an incomplete flight maneuver. The left hand elevon was dropped at
13:49:32 to give the negative Yaw and positive Roll required to
begin a Roll to the right. After this no further
commands were given for the completion of the maneuver or to correct
the adverse Yaw and Roll rates. The official investigation
declares the existence of these Yaw and Roll trends by including
various styles of dimensionless charts which are stated to be
graphical representations of the established Aero Moments, see
Fig. A9 and
Fig. TA-A2-4. The
absolute value of the Aero Moment is never provided with the
graphical data so assumptions about the Yaw and Roll rates must be
made to establish the effect these Aero Moments had on the shuttles
flight attitude.
Assumptions:
By
13:59:00
the negative Yaw Rate would have placed Columbia's nose to the left
of the flight path by an undetermined angle, possibly as much as 45˚ or Yaw = - 45˚,
(this yaw angle is only an assumption based on a worst case and may be
less).
13:59:30 is the point where RCS Yaw Jets
R2R and R3R began their 8 second continuous firing to correct the
negative Yaw but it is also the exact moment where the Colony video
begins. This does not provide enough time for the shuttle's
attitude to change and stabilize to what appears during the zoom
portion of the video. The RCS jet firing telemetry data,
events 38
and 39 at
13:59:30
on
Table A3,
are then moved back by 32 seconds,
(see
Update
05/15/2004). The RCS R2R and R3R jet firings then start at
13:58:58 and end at
13:59:06.
The maximum
amount of time required to redirect the shuttle's Yaw angle from
- 45˚ to the final value of
+90˚
is assumed to be 30 seconds,
(this corresponds to
an end time for the Yaw rotation of 13:59:28
which is 2 seconds prior to
the recording start time of the Colony video).
The assumed
initial values can then be inserted into the derived Yaw Rate
Function to get the final Yaw angle,
(4.36˚
x 30 seconds) - 45˚ = +90˚
This places the Columbia at a right angle to the
flight path with the left hand side facing fully windward.
Although the timeline seems a little tight with only 2 seconds to
spare before the start of the Colony video, these times are based on
a worst case scenario. The elapsed time of 30 seconds from the
beginning of Yaw jet firing at 13:58:58
to Columbia's final position at 13:59:28
may have been only 15 to 20 seconds. The Columbia may have
been sitting at its final position of
Yaw =
+90˚ by 13:59:15.
Based on the calculations done above it is entirely possible
that some attempt to correct an uncontrolled negative Yaw rate is what placed the
Columbia in the final position of +90° Yaw.
A subsequent vehicle breakup with the left wing dispersing
its material first would be the next logical event. Although the
conclusion reached using the simple derived Rate Function is entirely possible
it requires some assumptions that have an unknown accuracy. Fortunately an
independent source of evidence exists that relates the final calculated Yaw
angle to an eye witness account. An amateur video taken of Columbia that
begins after that final RCS jet firing and just a few seconds before vehicle
breakup includes a high level zoom of the
orbiter that clearly shows its attitude to be +90° Yaw or flying sideways with
the still intact left wing facing windward. The details of the
Colony Texas videoare on
Technical Articled TA-A3.
The animation of
Fig. TA-A2-3
describesa scenario such as the one described above where some degree of
negative Yaw developed during the first several minutes of reentry. This
negative Yaw is suddenly counteracted by firing the right rear Yaw Jets for 8
seconds continuous. Unfortunately the uncontrolled over correction
resulted in the Columbia being left in the worst possible position, turned
sideways to the Mach 18 airflow. Essentially all of the aerodynamic normal
accelerations are now being taken laterally on the shuttles airframe. This
is something that the orbiter was never designed for and the fact that the
shuttle would breakup would have been a forgone conclusion to any flight
engineer watching.
Fig. TA-A2-3
Attitude Graphs From the Official Investigation
The
following four charts are from the official final report and are intended by
that investigation to add legitimacy to its findings. The definition of
how the data is presented is contained in
Vol. 5
Appendix G13 of the official final report. The explanation for how the
values for the coefficients are arrived at is quite complicated and would not
add to the clarity of the information on this website. If this information
is required it can be found in the section of the final report mentioned above.
This is the same data presented in the graph of
Fig. A9with a clearer representation and added information.
It has been observed that the coefficient values shown on these charts from
STS-107 are not outside the range of values collected from other shuttle
missions. This observation is verified by Time Line and Ground Track
documents from the official investigation that at no point refer to the Yaw and
Roll trends as being significantly greater than that recorded during any other
shuttle mission, (until the last couple of minutes of reentry). The fact then that the Columbia's flight control system
was unable to control the attitude errors is further evidence that this portion
of the shuttle's avionics was severely damaged early during reentry. The
main value of these charts then is the same as that of
Fig. A9which is to show the Yaw and Roll trends over the
course of reentry.
Crossing
over Nevada, Utah, Arizona and New Mexico:
Chris
Valentine is another individual who has done a great deal of work combining and
overlaying images to get a better idea of what happened to Columbia during
reentry. Some graphics he has created such as a compilation of the many amateur
videos of Columbia's breakup have been featured on news reports and have been
used for official training purposes. Some of his data may be able to
tell us how the Columbia was flying through that period of reentry; analysis
follows.
Observational
Analysis A1 12/31/2003
Analysis
of Chris Valentine's Image Data
Note:
The use of outside or 3rd party text
and images on this site does not mean that the owner of that
material condones or agrees with all or any of the statements made
on these web pages. Some images may be enhanced to clarify
the content but should still express the original idea of the
author.
One of the images
Chris Valentine created for his own website, (see links below), is referenced here as ChrisTimeline1.jpg.
This image has still shots from a video he took of the STS-107 reentry overlaid on a version of the STS-107 Ground Track.
Prior to February 1st Mr. Valentine received a
time table from NASA showing where to look in the sky, or
where to aim a camera, in order to spot the Columbia during the reentry of
STS-107. The table has azimuth, elevation and range for a number of
different time points and is custom oriented from your exact GPS location,
(Latitude and Longitude). By using this information it might be possible
to check the validity of the time and location data that is provided in the
STS-107 Ground Track documents.
Verification
of position data shown in images:
In
order to use this information we have to make a couple of assumptions.
First we have to assume that the clock on Chris's camcorder was set to the
correct time. Chris claimed to have set the time on it recently before the
event, and when NASA viewed his video they said his time was, "6 seconds
short of UTC", this is not unreasonable but would have meant approximately
24 miles of travel or 5.5° of angular displacement shown, so this can be
factored in. The only other assumption which is
really the most important one is, where was the camcorder pointed at the precise
times the different still shots were taken? Chris seems to be
confident that the
time stamps on his still shots correspond to the given data point times on the
ground track and the time table. Of course we have no reason to disbelieve
Mr. Valentine but he was obviously busy operating the camcorder and not taking
note of exactly where it was pointed.
We can make a fairly accurate check of the camcorders position relative to the
Ground Track by observing the lighting conditions of the sky in the still images
as well as the position of the sun. For Chris's location, 35.57445
N. Latitude and -111.52940 W. Longitude, on February 1st, 2003 the sunrise and
sunset
for Mountain Standard Time were 7:27 a.m. and 5:55 p.m. MST respectively per the
Farmers
Almanac, and the suns position would have been about 10.5° to the South at
sunrise. After performing this check by drawing check lines and measuring
the various angles it has been determined that the data shown in the image is
most likely accurate.
Fig.
OA-A1-1
Fig.
OA-A1-1 is an image created by Chris Valentine with still shots from
his reentry video overlaid on to pages from the STS-107 Ground
Track. To suit the purposes of this site the following
changes have been made,
The
time table he received from NASA is placed in the lower left hand
corner.
The
Line Of Sight (LOS) to various points along the flight path are
indicated by the red lines. along with the exact Latitude and
Longitude of the location, the time of the sighting and the angle
of the LOS.
The Latitude and
Longitude of Chris Valentine's location has also been
added.
Diagram with a map indicating the
portion of the flight path viewable by Chris Valentine as
he recorded the STS-107 reentry. The image contains other
data such as the GPS coordinates for the end points and the time
on location for the shuttle as it entered and then left the
field of view.
Real
time animation tracing Columbia's flight path across the United States:
Real time animation tracing Columbia's flight path across
the United States from 13:53:00 GMT to end.
Animation includes super imposed video compilation created
by Chris Valentine.
In addition to the
compilation of amateur videos showing much of the STS-107 reentry
Chris Valentine's website contain homemade videos based on
different themes relating to Columbia and STS-107. Some are
set to music but they are all very entertaining as well as tasteful
tributes to Columbia and her crew. Everyone is urged to
visit his website and view or download the content.
At 6:54:44
a.m. MST, (13:54:44 GMT), the angle to Columbia's position on the image is 298°
as measured in a clockwise rotation from due North, while at 6:56:49 a.m. MST,
(13:56:49 GMT), the angle measures 80°. If we compare these values to
those of the time table, (298° Vs. 301.9° and 80° Vs. 84.4°), there seems to
be a minor 4° shift in the positions. When this is taken in context with the supposed
6 second discrepancy in the time stamp, the position shift is then closer to
1.5° and can be considered negligible. The
one aspect of the Columbia's position that cannot be determined easily from
the still photos is the altitude. In the few photographs that include a
ground level reference it is difficult to imagine that the shuttle is at the
elevation that the
time table claims would be necessary to observe it.
Summary
/ Conclusions:
Chris
Valentine's graphic helps the investigation significantly showing that
through this portion of the flight the shuttle was where it was supposed to be
when it was supposed to be there relative to a geodetic location on the Earth.
Chris's video follows the Columbia
across the United States for about 680 miles and 173 seconds. The average
velocity of Columbia throughout the sighting was 14,150
mph, (calculated simply
by dividing the total distance traveled by the total time duration). The
officially reported velocity at the beginning of the sighting was 115,463
mph and at the end 113,983
mph with the average at 14,723 mph. The difference between the sighting
and the official values then was only about 4%. Although the shuttles altitude seems low it would be nearly
impossible to come close to an accurate value by taking angles and distances
from the still photos, therefore no determination can be made about it except
as a general observation.
This
information significantly cuts down on the number of variables that must be
considered when recreating exactly what happened to Columbia during reentry.
Chris Valentines observation ends at 13:57:35 just about 2 minutes before LOS
and orbiter breakup.
Based
on data from the STS-107 Accident Investigation Time Line Rev. 15.
Chris
Valentine's video tracks the Columbia through most of the shuttles travel
across the United States from just East of the California border to nearly
where the orbiter enters Texas. Not only is this an important piece of
evidence because he captured so many events of debris shedding, but it also
makes the transition from observing the Columbia crossing the dark night sky
into early morning light in Texas where many of the videos that captured the
final breakup were shot. Unfortunately there does not seem to be any
video of Columbia from just before she entered Texas until just after LOS
where several different videos all seem to capture the same events.
Among the many amateurs recording the Columbia's breakup after LOS that day
were a pair of not so amateur Dutch AH-64 pilots training near Fort Hood who
kept the Apaches gun site camera trained on the Columbia debris for as long as
possible. It is unknown if the pilots who were in America for training
knew what they were watching at the time. It is possible they were
waiting to catch the incoming shuttle on the attack choppers advanced FLIR
sensor.
Sonic
booms:
All
eyewitness accounts of the shuttle disaster are virtually identical
for those residents living within the area that makes up the last 3/4 of the
debris field. The first
odd occurrence that caught the attention of many residents of
Jacksonville, Nacogdoches County and Hemphill Texas very shortly after 8:00 a.m. CST on the morning
of February 1, 2003 was a very loud twin sonic boom followed by a
rumbling that many of them described as feeling as if they were standing
next to a freight train. The first person to produce a
written statement of what happened the morning of February 1st, 2003
lives in Jacksonville Texas. The web page can be accessed at http://www.tyler.net/bone/jba/feb01-03.html.
This account states that the sonic booms started at exactly 8:01 a.m. CST with the
following rumble lasting for at least 30 seconds.
Another account written by John
Frederick of Nacogdoches Texas is very similar to the first except he states
that the sonic booms began at 8:04 a.m. He
described the sound as, "a large BOOM followed by a second smaller BOOM",
which would indicate that it was not the quick succession of two booms about a
half second apart. This could be taken to mean that something was
happening to the shuttle at the moment the shockwave events occurred. The Space Shuttles twin sonic booms are similar to that of any
super sonic swept wing aircraft where the initial event is the shockwave from
the nose of the shuttle and the second is from the rear of the swept wings and
or tail section. This
is another personal account written by a Nacogdoches resident, Sharon
Kasper.
The booms were followed by a loud
rumbling event that is not at all typical of a shuttle landing. Again John
Frederick's account states that it was, "an extended rumble &
roar that shook our house for at least 20-30 seconds". The time
period of 20 to 30 seconds is probably accurate based on statements by many
people who said they had time to run to different rooms of the house and
outside while it was happening. One possibility for what caused the loud
rumble is the many separate shockwave that were created as substantial pieces
of debris broke away from the main body and passed overhead at supersonic
speeds. From the video compilation on Chris
Valentine's website the three main engines can be seen quite clearly
separating from each other and continuing on to impact in Louisiana. The
difference in the times when the sonic booms were heard can be accounted for
based on the travel distance from Jacksonville to Nacogdoches as well as a
decrease in velocity of the debris itself. This is assuming that
someone's clock was not off the correct time by more than a few seconds.
All of the sonic boom witnesses also reported debris
falling in their areas immediately after the event, perhaps within a minute
This technical article
from the NASA website,
Shuttle_Reentry.pdf,
explains how the Space Shuttle typically reenters
Earths atmosphere listing the various phases of flight etc. The
document states that the shuttle does not enter subsonic flight
until it has reached an altitude of 49,000 feet and is about 25 miles
from the runway. When the shuttle is above 50,000 feet very little
of the sonic energy reaches the ground.
Therefore people on the ground usually
only hear the sonic booms when the shuttle is between 80,000 and 49,000
feet. Even then you would only recognize it as a sonic boom from
the shuttle if you were listening for it. Much of the time at
those altitudes the sonic booms are barely audible and most people don't
hear them at all. The fact that so many people living near where
Columbia broke up heard the sonic disturbance so prominently would
almost certainly mean that the Columbia was much lower than 200,767 feet when she broke up, (see
Table A4),
and may have even been below
50,000 feet.
A
more complete explanation of shock waves
and sonic booms
Table
A4 Reentry flight telemetry for STS-107 from officially published data
Table
A4 is simply some
of NASA's STS-107-Timeline
data entered into another Excel spread
sheet for easy data manipulation. All of the data in the gray area is
what is currently being reported
by NASA while the other
data represents the incremental changes in distance, velocity and altitude.
The Excel file used to create the spreadsheet below is STS-107_data.xls, (Based on Revision 12 of the STS-107
Ground Track). As a general check of the data's integrity the distance between data points
(dS) is calculated
using the average velocity and the incremental time between the points.
When the values in the last column, dS (Ft.)
Calculated, are compared to the values in the column, dS
(Ft.),
they seem to match very closely. *See
technical footnotes below chart.
Time (GMT)
N. Latitude
W. Longitude
Altitude (Ft.)
Speed (MACH)
1Speed (Ft./Sec.)
dT (Sec.)
2dS (Mi.)
3dS (Ft.)
dH (Ft.)
dV (Ft./Sec.)
4dS (Ft.) Calculated
13:44:09
30.83313
-167.5564
395010
24.56
24998
EI
EI
EI
EI
EI
EI
13:47:52
36.39853
-150.8472
288932
24.67
25110
223
1033.69
5457901
-106078
76
5599701
13:49:07
37.63983
-144.8031
259878
24.58
25019
75
344.22
1817488
-29054
-62
1876437
13:50:53
38.74388
-136.1424
243048
24.12
24550
106
476.27
2514734
-16830
-319
2602400
13:52:17
38.99255
-129.1507
236791
23.58
24001
84
376.43
1987560
-6257
-374
2016108
13:52:59
38.89502
-125.7137
233618
23.25
23665
42
184.81
975825
-3173
-229
993946
13:53:02
38.88306
-125.4816
233457
23.23
23645
3
12.50
66052
-161
-13
70935
13:53:10
38.84789
-124.8644
232864
23.17
23583
8
33.29
175789
-593
-41
188671
13:53:34
38.70748
-122.9518
231077
22.97
23380
24
103.47
546357
-1787
-138
561129
13:53:46
38.61631
-121.9682
230203
22.86
23268
12
53.44
282164
-874
-76
279221
13:54:10
38.41620
-120.1739
228460
22.64
23044
24
97.98
517348
-1743
-152
553068
13:54:24
38.27043
-119.0681
227437
22.51
22912
14
60.76
320841
-1023
-90
320770
13:54:53
37.93257
-116.8958
225610
22.22
22617
29
120.39
635682
-1827
-201
655892
13:55:12
37.67398
-115.4789
224546
22.02
22413
19
79.38
419174
-1064
-138
425855
13:55:21
37.53489
-114.7805
224002
21.92
22311
9
39.41
208135
-544
-69
200804
13:55:41
37.23783
-113.4046
222821
21.69
22077
20
78.27
413291
-1181
-159
441550
13:56:02
36.88308
-111.9244
221670
21.45
21833
21
85.21
449934
-1151
-166
458498
13:56:03
36.86626
-111.8580
221612
21.44
21823
1
3.84
20326
-58
-6
21823
13:56:16
36.62465
-110.9363
220778
21.28
21660
13
53.69
283490
-834
-111
281582
13:56:17
36.60695
-110.8711
220711
21.27
21650
1
3.81
20154
-67
-6
21650
13:56:20
36.55353
-110.6758
220488
21.23
21609
3
11.44
60442
-223
-27
64827
13:56:22
36.51765
-110.5460
220374
21.21
21588
2
7.62
40236
-114
-13
43177
13:56:24
36.48154
-110.4165
220235
21.17
21548
2
7.61
40197
-139
-27
43096
13:56:30
36.37187
-110.0300
219820
21.13
21507
6
22.78
120301
-415
-27
129045
13:57:19
35.38489
-106.7845
217757
20.45
20815
49
194.06
1024642
-2063
-471
1019953
13:57:24
35.29030
-106.4807
217315
20.38
20744
5
18.32
96773
-442
-48
103720
13:57:28
35.21480
-106.2388
216845
20.31
20672
4
14.61
77150
-470
-48
82691
13:58:16
34.28679
-103.2929
210304
19.55
19899
48
179.10
945655
-6541
-527
955166
13:58:32
33.97970
-102.3245
208380
19.28
19624
16
59.30
313153
-1924
-187
313991
13:58:36
33.90836
-102.0992
207918
19.21
19553
4
13.82
72984
-462
-48
78212
13:58:38
33.87283
-101.9869
207607
19.16
19502
2
6.89
36394
-311
-34
39004
13:58:54
33.57505
-101.0413
205553
18.86
19196
16
58.10
306796
-2054
-208
307151
13:58:56
33.54052
-100.9311
205311
18.83
19166
2
6.77
35792
-242
-20
38332
13:59:06
33.36957
-100.3839
204336
18.68
19013
10
33.68
177846
-975
-104
190137
13:59:30
32.95608
-99.04132
200767
18.16
18484
24
82.74
436882
-3569
-360
443627
13:59:32
LOS
LOS
LOS
LOS
LOS
LOS
LOS
LOS
LOS
LOS
LOS
Technical
Footnotes for Table A4:
EI - Entry Interface
LOS - Los Of Signal
Assumed ground speed Note:
the Mach number provided by NASA is most likely the vector velocity of the
shuttle through the atmosphere consisting of twocomponents,
the forward speed and the rate of descent. Because the angle of descent for
a Space Shuttle is typically small usuallybetween
1 and 3° compared to the
forward speed this value can be
considered negligible for this calculation.Therefore
the given velocity is the assumed ground speed.
Velocity (V) = (MACH Number)*(Speed
of sound 694 Mi./Hr.)*(5280 Ft./Mi.)/(3600 Sec./Hr.)
Distance traveled between
points in miles (Microsoft Excel code)
C=Sin(Latitude1/57.3)*Sin(Latitude2/57.3)+Cos(Latidude1/57.3)*Cos(Latitude2/57.3)*Cos(Longitude2/57.3-Longitude1/57.3)
Distance (S) = 3959 * ACos(C)
Distance traveled between
points in feet Distance (S) = 5280 feet / Mile
Calculated distance
traveled between points in feet Distance (S) = Velocity (Ft./Sec.) * Time Interval (Sec.)
The chart of
Fig. A10 is a graphical representation of the STS-5 reentry flight path.
This chart should represent reentry flight data for all shuttle missions because
it is based on the reentry flight routine contained in the OPS 304 computer
program. The true flight data and reentry flight path for STS-107 will be
very different from STS-5 because on STS-107 the Columbia suffered a complete
flight control systems failure before she could perform any flight maneuvers.
The fact that Columbia suffered a complete loss of flight control It should be noted that throughout the region
of time from EI+0 to EI+923 that corresponds to the STS-107 reentry the shuttle
should hold a 40° Angle of Attack (AOA) while the rate of descent is slowed
considerably through the peak heating region. It is believed that Columbia
was unable to maintain the AOA of 40° and descended too fast.
It
has since been determined that the spread sheet and graph of
Table A4
and
Fig. A10 do not
accurately represent STS-107. The true altitude data from STS-107
was replaced with either nominal data or data straight from another
shuttle mission such as STS-5. This was part of an effort to
maintain a cover story that Columbia was flying normally for most of
reentry.
All that can really be determined about
the actions of the people involved in Columbia's reentry and breakup is
that no one seemed to be alerted to the impending disaster. The
document, STS-107_Reentry_Text_J.pdf,
is a transcription of all of the released verbal communications between the Columbia and Mission Control at
Houston Space Center as well as between the
Columbia crew members. The official final report leads us to believe that the foam strike and the possibility
that the TPS somewhere on the orbiter had been severely breached was widely discussed
with great concern among NASA personnel as well as between flight engineers and
the shuttle crew. This is at odds with the crew cabin video, Crew
Cabin Video 100 MB, from the first
half of reentry that shows smiling astronauts going through reentry checklists
and commenting about the bright and colorful plasma forming outside the
windows. The transcribed communications between Mission Control
personnel is also overly free of concern for the fate of the shuttle.
Although some statements do acknowledge the relatively minor temperature
increases seen in the telemetry data transmitted to Mission Control, no mention
is ever made that the cause could be a breach in the TPS. There was also
no mention of the ever increasing Yaw anomaly depicted in the graphic from
Fig. A9
Fig. A11
After the complete loss of communications occurred with Mission Control at
13:59:32, a contingency plan was put in
place for what actions to take when the Columbia landed at its prescheduled
time of 14:16:00. It just didn't
occur to those tracking the shuttle that the worst had happened until the
reports of multiple contrails and debris falling all over central Texas began coming in. No one
in Mission Control Houston ever used the words "breach"or "burn through"
anytime during reentry. Fortunately some
of the best accounts of Columbia's final minutes come from the amateur videos
that have been widely seen. If anyone observing the events in Mission
Control thought that a burn through was happening as some later stated on
television, they didn't mention it at the time.