STS-107, Chronicle Of A Disaster Foretold?
Iconoclast
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To: PCav8or
The foam is an insulation material applied to the main propellant tank. The tank is comprised of two sections. The lower section contains liquid Oxygen and the upper section contains liquid Hydrogen. The insulation minimizes boil-off while on the pad and also due to aerodynamic heating during lift-off and high-speed flight while in the atmosphere.
The foam is an insulation material applied to the main propellant tank. The tank is comprised of two sections. The lower section contains liquid Oxygen and the upper section contains liquid Hydrogen. The insulation minimizes boil-off while on the pad and also due to aerodynamic heating during lift-off and high-speed flight while in the atmosphere.
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Tricky Woo hits the mark with his remarks about what the shuttle is not: (reusable, routine, safe, casual, or a free-roaming space ship).
The reason for most of that is practicality - it is actually still rather difficult - given our grasp of the technology and the 1960's tools in use - to launch things into space so they can return gently on demand. A lot harder than ICBM's. Some days it is impossible.
Kennedy's plan to reach the moon in the 60's was a brilliant amalgam of political, military, economic, & private goals sold to the ever-optimistic American public with plenty of flag-waving and Hollywood-style manipulation. It worked just fine for most of the near-term purposes, but the larger consequence is that NASA has had to mix in equal parts of myth and performance ever since in return for its annual billions. And it has had to rain money every year on politically well-positioned states for contracts, facilities, "Labs", and "Space Centers", especially ones in the Bush family franchise zone, including Florida and Texas, established courtesy of Kennedy's VP and successor from Texas, LBJ.
The NASA-inspired barrage of press materials, calculated leaks, fanstatic new scientific discoveries and environmental problems soluble only through spaceflight tends to closely follow the annual progress of U.S. Federal budget negotiations in Washington. If the funding calculations bog down without enough zeros in the right places for NASA and the numerous off-the books projects that feed into it and draw out of it, then reserve PR troops come in with fresh slants on Global Warming and recently discovered (or not yet discovered) asteroids that may hit the earth at any moment to wipe out all forms of life. Holywood flicks reinforcing the thought are quickly released. For many Washington-watchers, the NASA budget cycle has replaced a certain circus as "The greatest Show on Earth."
One can note with respectful awe how the current cock-up was converted within a matter of hours into a very organized campaign by NASA spokespeople and hangers-on to plead "underfunding" as the root cause and thus negotiate larger budgets for more of the same.
The real problem that plagues NASA the most is not underfunding, but arteriosclerosis. Too many NASA people have the "job for life" mentality that Government employment fosters, so they make choices to ensure continuation of programs which preserve their pension plans, rather than allowing more efficient uses of the available resources. In cases recently coming to light, some practices more resemble corruption than bureaucracy.
All that said, NASA as an institution has done a difficult job quite skillfully under an uncomfortable degree of public scrutiny.
But, at times like this, the organization tends to regress under the protective cover of institutional myths inherited from the 60's, distracting many from the underlying problems by focussing attention on a sea of marginally-relevant details.
The reason for most of that is practicality - it is actually still rather difficult - given our grasp of the technology and the 1960's tools in use - to launch things into space so they can return gently on demand. A lot harder than ICBM's. Some days it is impossible.
Kennedy's plan to reach the moon in the 60's was a brilliant amalgam of political, military, economic, & private goals sold to the ever-optimistic American public with plenty of flag-waving and Hollywood-style manipulation. It worked just fine for most of the near-term purposes, but the larger consequence is that NASA has had to mix in equal parts of myth and performance ever since in return for its annual billions. And it has had to rain money every year on politically well-positioned states for contracts, facilities, "Labs", and "Space Centers", especially ones in the Bush family franchise zone, including Florida and Texas, established courtesy of Kennedy's VP and successor from Texas, LBJ.
The NASA-inspired barrage of press materials, calculated leaks, fanstatic new scientific discoveries and environmental problems soluble only through spaceflight tends to closely follow the annual progress of U.S. Federal budget negotiations in Washington. If the funding calculations bog down without enough zeros in the right places for NASA and the numerous off-the books projects that feed into it and draw out of it, then reserve PR troops come in with fresh slants on Global Warming and recently discovered (or not yet discovered) asteroids that may hit the earth at any moment to wipe out all forms of life. Holywood flicks reinforcing the thought are quickly released. For many Washington-watchers, the NASA budget cycle has replaced a certain circus as "The greatest Show on Earth."
One can note with respectful awe how the current cock-up was converted within a matter of hours into a very organized campaign by NASA spokespeople and hangers-on to plead "underfunding" as the root cause and thus negotiate larger budgets for more of the same.
The real problem that plagues NASA the most is not underfunding, but arteriosclerosis. Too many NASA people have the "job for life" mentality that Government employment fosters, so they make choices to ensure continuation of programs which preserve their pension plans, rather than allowing more efficient uses of the available resources. In cases recently coming to light, some practices more resemble corruption than bureaucracy.
All that said, NASA as an institution has done a difficult job quite skillfully under an uncomfortable degree of public scrutiny.
But, at times like this, the organization tends to regress under the protective cover of institutional myths inherited from the 60's, distracting many from the underlying problems by focussing attention on a sea of marginally-relevant details.
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Concerning heat-resistent tiles, I just remembered something I read a couple of years ago. The Russian shuttle-program "Buran" was apparently using some other carbon-based material that was more heat-resistant and stronger. I checked, and the web-site still exists: http://www.buran.ru/htm/molniya5.htm
The website is a bit slow, but it seems the russians had a few ideas about how to make a "better" shuttle. Maybe some of their ideas could be incorporated to make the american shuttles safer? Would love to see Buran fly alongside the shuttle in the future, but I guess it's a bit unrealistic...
The show must go on.
The website is a bit slow, but it seems the russians had a few ideas about how to make a "better" shuttle. Maybe some of their ideas could be incorporated to make the american shuttles safer? Would love to see Buran fly alongside the shuttle in the future, but I guess it's a bit unrealistic...
The show must go on.
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Can I thank those of you who know so much more about the Shuttle than I do for some very informative postings.
Its a pity that the media does'nt have the same knowledge base available.
Obviously the majority of contributors to PPRUNE are from general/commercial aviation. So perhaps we struggle ( a little) to come to terms with what may well turn out to be a small failure causing such an accident.
I can still remember the Apollo 13 crew being able, on their departure from the command module being able to swing round in their re-entry vehicle to actually see the damage that had caused the problem. To have the Shuttle crew not being able to inspect (via cameras or a space walk) any possible damage surprised me.
After all (as someone suggested) if there was a problem with tiles (if that ends ut being the cause) there could have during a space walk been the chance to effect a "CAT Q I landing" repair.
Although this accident is very sad I still remember a slip in Tampa when we drove across Florida to watch a midnight launch (of the same shuttle). Quite an occasion, but what amazed me was the link via the car radio to the mission control RT feed.
As we watched the launch we listened to the exchanges ( in the first minute after lift-off) between the crew and launch control as numerous AC and DC electric busbars failed with finally the main rocket nozzle directional control reverting to the standby (alternate) signalling.
Throughout the exchanges I should think the EICAS (Engine Indicating, Crew Alerting System for non-Boeing drivers) and the systems panel must have been lit up like a christmas tree!
The exchanges were as if they were in a fixed base (not even full flight) simulator!
The memories of these cool and calm exchanges over the radio were as impressive as the visual spectacle.
They, together with their collegues sadly lost over Texas, are truly special people. I salute them all.
Its a pity that the media does'nt have the same knowledge base available.
Obviously the majority of contributors to PPRUNE are from general/commercial aviation. So perhaps we struggle ( a little) to come to terms with what may well turn out to be a small failure causing such an accident.
I can still remember the Apollo 13 crew being able, on their departure from the command module being able to swing round in their re-entry vehicle to actually see the damage that had caused the problem. To have the Shuttle crew not being able to inspect (via cameras or a space walk) any possible damage surprised me.
After all (as someone suggested) if there was a problem with tiles (if that ends ut being the cause) there could have during a space walk been the chance to effect a "CAT Q I landing" repair.
Although this accident is very sad I still remember a slip in Tampa when we drove across Florida to watch a midnight launch (of the same shuttle). Quite an occasion, but what amazed me was the link via the car radio to the mission control RT feed.
As we watched the launch we listened to the exchanges ( in the first minute after lift-off) between the crew and launch control as numerous AC and DC electric busbars failed with finally the main rocket nozzle directional control reverting to the standby (alternate) signalling.
Throughout the exchanges I should think the EICAS (Engine Indicating, Crew Alerting System for non-Boeing drivers) and the systems panel must have been lit up like a christmas tree!
The exchanges were as if they were in a fixed base (not even full flight) simulator!
The memories of these cool and calm exchanges over the radio were as impressive as the visual spectacle.
They, together with their collegues sadly lost over Texas, are truly special people. I salute them all.
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There is an interesting story in today's New York Times about tile damage on a previous Columbia mission. I think Danny discourages full text pasting of copyrighted text, so the link is here. (Registration required, but it is free.)
http://www.nytimes.com/2003/02/04/national/04WRON.html
The story relates a report on tile damage to Columbia in 1997, in which the number of tile hits greatly exceeded the norm. The tile damage was caused by foam falling off the external tank.
"Inspectors counted 308 hits. Of those, 132 were "greater than one inch." Some of the hits measured up to 15 inches long with depths of up to one-and-a-half inches. The tiles [presumably the ones hit] were only two inches deep, [some tiles are five inches thick] so the largest hits penetrated three-quarters of the way into the tiles." [Comment, if these tiles were only two inches thick, these were not located in an area of high aerodynamic heating.]
The damaged tiles were mostly around the shuttle's nose. After the mission, more than 100 tiles were taken off because "they were irreparable."
NASA also changed the formulation of the foam after the 1997 incident. The Times article states that "... to be environmentally friendly, NASA had eliminated the use of Freon in foam production. The Marshall Space Flight Center in Huntsville, Ala., later concluded that the absence of Freon led to the detachment of the foam. ...the formulation was later improved."
Finally, the Times article includes opinions from several aerdynamicists involved in shuttle aerdoynamic testing, who said 'that even slightly damaged tiles — perhaps only roughened or cracked — could generate turbulence near the tiles during the tremendous speeds of re-entry, creating potentially dangerous heating of Columbia's aluminum skin.'"
_____________________________________
Over 30 years ago when the shuttle was first proposed, the scheme (and corresponding launch rate) was for it to be mainly used as a logistics vehicle to transport hydrogen for off-loading to in-orbit NERVA rockets that would be used for manned lunar bases and manned Mars flights. NERVA rockets used a nuclear reactor to heat hydrogen as the means of propulsion; ultimately, work stopped on these engines just prior to final flight test.
Initial shuttle designs called for two air-breathing engines so it would not be a glider on return (the USAF was most interested in having an ability to land at points some distance away from the orbital track) and for the booster rocket to also be manned and return from a sub-orbital flight to a landing site.
The lunar base and manned Mars exploration missions were much like what Arthur Clarke had whirling around in space in "2001, a Space Odyssey". The basic hardware for these missions would be launched into earth orbit by the bottom stages of a Saturn V type rocket, there to be assembled by astronauts. Use of a Satrun V meant you were not constrained by the weight-to-orbit capabilitiy of a shuttle, nor by its payload bay dimensions.
But in the words of the refrain written by Kurt Vonnegut (who was a prisoner of war in Dresden when it was fire-bombed) in his novel "Slaughterhouse 5": "And so it goes."
http://www.nytimes.com/2003/02/04/national/04WRON.html
The story relates a report on tile damage to Columbia in 1997, in which the number of tile hits greatly exceeded the norm. The tile damage was caused by foam falling off the external tank.
"Inspectors counted 308 hits. Of those, 132 were "greater than one inch." Some of the hits measured up to 15 inches long with depths of up to one-and-a-half inches. The tiles [presumably the ones hit] were only two inches deep, [some tiles are five inches thick] so the largest hits penetrated three-quarters of the way into the tiles." [Comment, if these tiles were only two inches thick, these were not located in an area of high aerodynamic heating.]
The damaged tiles were mostly around the shuttle's nose. After the mission, more than 100 tiles were taken off because "they were irreparable."
NASA also changed the formulation of the foam after the 1997 incident. The Times article states that "... to be environmentally friendly, NASA had eliminated the use of Freon in foam production. The Marshall Space Flight Center in Huntsville, Ala., later concluded that the absence of Freon led to the detachment of the foam. ...the formulation was later improved."
Finally, the Times article includes opinions from several aerdynamicists involved in shuttle aerdoynamic testing, who said 'that even slightly damaged tiles — perhaps only roughened or cracked — could generate turbulence near the tiles during the tremendous speeds of re-entry, creating potentially dangerous heating of Columbia's aluminum skin.'"
_____________________________________
Over 30 years ago when the shuttle was first proposed, the scheme (and corresponding launch rate) was for it to be mainly used as a logistics vehicle to transport hydrogen for off-loading to in-orbit NERVA rockets that would be used for manned lunar bases and manned Mars flights. NERVA rockets used a nuclear reactor to heat hydrogen as the means of propulsion; ultimately, work stopped on these engines just prior to final flight test.
Initial shuttle designs called for two air-breathing engines so it would not be a glider on return (the USAF was most interested in having an ability to land at points some distance away from the orbital track) and for the booster rocket to also be manned and return from a sub-orbital flight to a landing site.
The lunar base and manned Mars exploration missions were much like what Arthur Clarke had whirling around in space in "2001, a Space Odyssey". The basic hardware for these missions would be launched into earth orbit by the bottom stages of a Saturn V type rocket, there to be assembled by astronauts. Use of a Satrun V meant you were not constrained by the weight-to-orbit capabilitiy of a shuttle, nor by its payload bay dimensions.
But in the words of the refrain written by Kurt Vonnegut (who was a prisoner of war in Dresden when it was fire-bombed) in his novel "Slaughterhouse 5": "And so it goes."
Evertonian
Lots of good points & discussion here chaps. (circumstances excluded of course)
arcniz
As much as I'd love to believe that what you have written was a conspiracy theorists gibberish, I sadly believe that you may be right on the money here. It was one of the first things El Presidente did after the event, get mo' money from Congress. Perhaps throwing money at NASA isn't the only solution & the real problems are inherent, as you stated. (Again, I don't wish to diminish what's happened, but I'm assuming the problems at NASA were there all along)
SaturnV
How sadly ironic that in an effort to be environmentally friendly, they may have inadvertantly doomed this mission. Especially considering how much emphasis they are putting on the toxicity of the debris! (I imagine there are other motives here though)
Lots of suggested solutions are just not technologically possible at the moment. It's just like riding a giant trampoline, once at the top of the arc, there's not much else the orbiter can do(manouverability wise) prior to it's descent. Lets hope their sacrifice provides the stimulus to take the next step.
Forgot to put this in...
Did anyone else see the footage of what was purported to be the left wing in orbit during this mission? It looked like the wing root area, but I'd have thought the angles were all wrong. Regardless of that, it showed a definate dent in one section & a crack in another. Does anyone know if NASA has made a statement on this?
arcniz
As much as I'd love to believe that what you have written was a conspiracy theorists gibberish, I sadly believe that you may be right on the money here. It was one of the first things El Presidente did after the event, get mo' money from Congress. Perhaps throwing money at NASA isn't the only solution & the real problems are inherent, as you stated. (Again, I don't wish to diminish what's happened, but I'm assuming the problems at NASA were there all along)
SaturnV
How sadly ironic that in an effort to be environmentally friendly, they may have inadvertantly doomed this mission. Especially considering how much emphasis they are putting on the toxicity of the debris! (I imagine there are other motives here though)
Lots of suggested solutions are just not technologically possible at the moment. It's just like riding a giant trampoline, once at the top of the arc, there's not much else the orbiter can do(manouverability wise) prior to it's descent. Lets hope their sacrifice provides the stimulus to take the next step.
Forgot to put this in...
Did anyone else see the footage of what was purported to be the left wing in orbit during this mission? It looked like the wing root area, but I'd have thought the angles were all wrong. Regardless of that, it showed a definate dent in one section & a crack in another. Does anyone know if NASA has made a statement on this?
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Two points that apply,
The Gen Accounting Office in the US last week completed an audit on NASA. One auditor stated that he has never been so afraid of the safety of space fligh than at the moment (prior to the accident)
Also, retired NASA administrator Dan Goldin once stated that the space shuttle is waste of money as it achies very little.
The Gen Accounting Office in the US last week completed an audit on NASA. One auditor stated that he has never been so afraid of the safety of space fligh than at the moment (prior to the accident)
Also, retired NASA administrator Dan Goldin once stated that the space shuttle is waste of money as it achies very little.
Per Ardua ad Astraeus
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"but I'd have thought the angles were all wrong. Regardless of that, it showed a definate dent in one section & a crack in another. Does anyone know if NASA has made a statement on this"
I too could not figure out the 'angles' either, but the 'crack' was discussed on British TV last night and said to be a piece of wire taped to the inside of the window.
I too could not figure out the 'angles' either, but the 'crack' was discussed on British TV last night and said to be a piece of wire taped to the inside of the window.
In the time of Mir the Russians frequently said that in their view, long-term space flight would regularly involve trouble-shooting by the crews - which everyone west of the Vistula took to be an excuse for building a dodgy space station. I wonder if their design philosophy might be worth looking at?
Avoid imitations
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Anyone know what pressures the shuttle mainwheel tyres are inflated to?
I can't help thinking about those tyres overheating and perhaps exploding in the wheel bay. Would they be capable of causing structural damage to the left wing?
I can't help thinking about those tyres overheating and perhaps exploding in the wheel bay. Would they be capable of causing structural damage to the left wing?
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In connection with the New York Times article linked to by SaturnV: “Engineer's '97 Report Warned of Damage to Tiles by Foam”
-------- Start quote --------
… The newly released NASA video shows a whitish object soaring backward, striking the Columbia's left wing and bursting into a cloud of dust. …
-------- End quote --------
Couldn't it be just as likely that the cloud is largely powdered tile?
-------- Start quote --------
… The newly released NASA video shows a whitish object soaring backward, striking the Columbia's left wing and bursting into a cloud of dust. …
-------- End quote --------
Couldn't it be just as likely that the cloud is largely powdered tile?
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FACTS PLEASE
FLIGHT PROFILE.....
Was the Shuttle flying straght and level at 200,000 feet, mach 18 at a pitch up angle of between 28 and 38 degrees when the disaster happened ?
Was it flying under computer (ie non-manual) control ?
At what stage in the flight profile are the high angles of bank (50 + degrees) normally iinitiated ( Altitude/speed/ distance from touchdown /computer or manual ?).
Are slowing down s-bends optional or obligatory in the standard flight plan.?
Yes I know that this will all be covred in the final Report but in my sadness I am battering my brains for an explanation of this heroic disaster and I don;t want to believe it was just happenchance !!!!!!!
Any info much appreciated
Was the Shuttle flying straght and level at 200,000 feet, mach 18 at a pitch up angle of between 28 and 38 degrees when the disaster happened ?
Was it flying under computer (ie non-manual) control ?
At what stage in the flight profile are the high angles of bank (50 + degrees) normally iinitiated ( Altitude/speed/ distance from touchdown /computer or manual ?).
Are slowing down s-bends optional or obligatory in the standard flight plan.?
Yes I know that this will all be covred in the final Report but in my sadness I am battering my brains for an explanation of this heroic disaster and I don;t want to believe it was just happenchance !!!!!!!
Any info much appreciated
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Buster writes:
I'm not sure what you mean about 'conspiracy' theory, but since 'conspiracy' is a serious legal accusation, I must take exception to your comment.
I do not claim to be aware of any 'conspiracy' at NASA in regard to this particular matter, nor do I contest the integrity of any specific individual. My contention was and is that NASA has become ever more lethargic due to bureaucracy and the unique problems of reinventing its financial raison d'etre each year.
The politics of it are about money and power, much like ancient Rome, but with different hats. Politics is a sanctioned form of conspiracy that always involves some degree of intrigue and rapacity. Certain military programs, NASA, and the 'Federal Labs' are great patronage honeypots that each Presidential administration inherits to manipulate for political purposes - both in terms of the money they can spend directly and for the potential that focussed scientific research has to boost some industries at the expense of others. The elected representatives in Congress are not oblivious to this process and actively maneuver to benefit their constituents from it during the push and pull of legislative negotiations.
As much as I'd love to believe that what you have written was a conspiracy theorists gibberish, I sadly believe that you may be right on the money here. It was one of the first things El Presidente did after the event, get mo' money from Congress. Perhaps throwing money at NASA isn't the only solution & the real problems are inherent, as you stated. (Again, I don't wish to diminish what's happened, but I'm assuming the problems at NASA were there all along)
I do not claim to be aware of any 'conspiracy' at NASA in regard to this particular matter, nor do I contest the integrity of any specific individual. My contention was and is that NASA has become ever more lethargic due to bureaucracy and the unique problems of reinventing its financial raison d'etre each year.
The politics of it are about money and power, much like ancient Rome, but with different hats. Politics is a sanctioned form of conspiracy that always involves some degree of intrigue and rapacity. Certain military programs, NASA, and the 'Federal Labs' are great patronage honeypots that each Presidential administration inherits to manipulate for political purposes - both in terms of the money they can spend directly and for the potential that focussed scientific research has to boost some industries at the expense of others. The elected representatives in Congress are not oblivious to this process and actively maneuver to benefit their constituents from it during the push and pull of legislative negotiations.
PeterJ, and others,
The "sane participants" of the sci.space.shuttle newsgroup have put together the following FAQ:
http://www.io.com/~o_m/columbia_loss_faq.html
Shuttle re-entries are normally under computer control until just before landing. There's an extensive sss thread on the subject here:
http://groups.google.com/groups?hl=e...109%26rnum%3D5
The following info on flight profile is taken from the FAQ. I hope this isn't considered an excessively long post:
===================================
* Where and when did Columbia break up? (Altitude, speed, time, etc.)
===================================
Ground controllers lost communications with Columbia at 7:59:22am
CST, at a mission elapsed time of 15 days, 22:20:22. At the time,
the shuttle was at an altitude of 207,000 feet (63,000 m), traveling
at Mach 18.3, approximately 37 miles (60 km) above the Dallas-Fort
Worth Metroplex region of Texas.
===================================
* What was Columbia's status prior to breakup?
===================================
First, let's look at Columbia's reentry profile. The Shuttle has 3
distinct phases to the standard reentry profile:
1) Thermal Control Phase. This lasts from Entry Interface, when the
first aerodynamic effects occur, until a speed of approximately
19,000 ft/sec (12,900 MPH, 11,200 kts, 20,900 km/hr) has been reached.
2) Equilibrium Glide Phase. This is flight at a constant attitude as
the deceleration due to drag builds up to approximately 1G.
3) Constant Drag Phase. The 1G deceleration is held until the orbiter
enters the Terminal Area Energy Management interface, after which it
is flying as a conventional, but very heavy and fast, glider. This
is usually 52 NM (59 SM, 94 km) from the landing site, at an altitude
of 83,000', and a speed of Mach 2.5 (2500 ft/sec, 760 m/sec) The
orbiter slows to below Mach 1 at about 49,000', 22 NM (25 SM, 40 km)
from the runway.
Columbia was either at the end of the first phase, or the beginning
of the second phase when she broke up.
The first phase begins when the orbiter is oriented tail-first,
and the OMS engines fire to reduce its speed by about 300 ft/second
(90 m/sec). The reaction control system then orients the orbiter nose
first to prepare for reentry. At roughly 400,000 ft altitude (122
km), Entry Interface is considered to occur. This normally takes
place 4,400 NM (5063 statute miles/3160 km) from the landing site.
The speed at this point is about 25,000 ft/second (7600 m/sec).
At this point the orbiter is maneuvered to 0 degrees roll and yaw,
and a 40 degree angle of attack. The flight control system at this
point uses the Reaction Control System to keep things aligned. The
forward RCS engines are turned off at the entry interface, and the
aft RCS system is used to maneuver the spacecraft.
The spacecraft must dissipate the tremendous amount of kinetic
energy it has. It does this by varying the amount of aerodynamic
drag that it presents on the way down. This generates a lot of
heat because of the speed of the shuttle. This heating is controlled
by changing the speed of the shuttle in small amounts. This is done
by varying the aerodynamic drag of the shuttle. Most aircraft do
this by changing the Angle of Attack. When you pull up the nose,
an airplane tends to slow down, unless an engine is used to counteract
the drag. For a re-entering shuttle, the angle of attack must be
held constant to prevent the structure from overheating.
The shuttle controls drag by rolling into a series of 'S' turns along the
flight path. Increasing the roll angle of the orbiter moves the
direction of its lift (perpendicular to its wings) away from the
vertical, causing it to descend faster. These S-turns are used to
fine tune the energy level (A fancy way of saying altitude and
airspeed) of the orbiter, something like skiers turning while going
downhill to control their speed. When a dynamic pressure of 10
psf is reached (EAS of 62 MPH (100 km/hr)), when the orbiter's
ailerons become effective for roll control. At that point, the roll
RCS engines are deactivated. At a dynamic pressure of 20 psf (EAS of
85 MPH(138 km/hr), roughly), the elevators on the orbiter become
active, and the RCS pitch engines are deactivated.
In the Equilibrium Glide Phase of the reentry, the spacecraft is
flown to maintain a constant drag level, where the flight path angle
remains constant. This is maintained until the deceleration of the
orbiter due to drag is about 1G.
In the last phase of the reentry, the 1G deceleration level is held,
reducing the angle of attack as necessary, until the Terminal Area
Energy Management interface. The RCS system continues to control
Yaw until the rudder become effective at around Mach 3.5.
Columbia was lost either at the tail end of the Thermal Control
Phase, or the early stages of the Equilibrium Glide Phase. The
ailerons and elevators were providing control, (the Q at that point
was around 75-80 psf, or an EAS of about 170 mph (275 km/hr)), and
yaw was being controlled by the RCS thrusters in the tail.
Late reports before this writing this indicate that the Flight Control
System reported that it was correcting a left yaw/roll just before
breakup.
The "sane participants" of the sci.space.shuttle newsgroup have put together the following FAQ:
http://www.io.com/~o_m/columbia_loss_faq.html
Shuttle re-entries are normally under computer control until just before landing. There's an extensive sss thread on the subject here:
http://groups.google.com/groups?hl=e...109%26rnum%3D5
The following info on flight profile is taken from the FAQ. I hope this isn't considered an excessively long post:
===================================
* Where and when did Columbia break up? (Altitude, speed, time, etc.)
===================================
Ground controllers lost communications with Columbia at 7:59:22am
CST, at a mission elapsed time of 15 days, 22:20:22. At the time,
the shuttle was at an altitude of 207,000 feet (63,000 m), traveling
at Mach 18.3, approximately 37 miles (60 km) above the Dallas-Fort
Worth Metroplex region of Texas.
===================================
* What was Columbia's status prior to breakup?
===================================
First, let's look at Columbia's reentry profile. The Shuttle has 3
distinct phases to the standard reentry profile:
1) Thermal Control Phase. This lasts from Entry Interface, when the
first aerodynamic effects occur, until a speed of approximately
19,000 ft/sec (12,900 MPH, 11,200 kts, 20,900 km/hr) has been reached.
2) Equilibrium Glide Phase. This is flight at a constant attitude as
the deceleration due to drag builds up to approximately 1G.
3) Constant Drag Phase. The 1G deceleration is held until the orbiter
enters the Terminal Area Energy Management interface, after which it
is flying as a conventional, but very heavy and fast, glider. This
is usually 52 NM (59 SM, 94 km) from the landing site, at an altitude
of 83,000', and a speed of Mach 2.5 (2500 ft/sec, 760 m/sec) The
orbiter slows to below Mach 1 at about 49,000', 22 NM (25 SM, 40 km)
from the runway.
Columbia was either at the end of the first phase, or the beginning
of the second phase when she broke up.
The first phase begins when the orbiter is oriented tail-first,
and the OMS engines fire to reduce its speed by about 300 ft/second
(90 m/sec). The reaction control system then orients the orbiter nose
first to prepare for reentry. At roughly 400,000 ft altitude (122
km), Entry Interface is considered to occur. This normally takes
place 4,400 NM (5063 statute miles/3160 km) from the landing site.
The speed at this point is about 25,000 ft/second (7600 m/sec).
At this point the orbiter is maneuvered to 0 degrees roll and yaw,
and a 40 degree angle of attack. The flight control system at this
point uses the Reaction Control System to keep things aligned. The
forward RCS engines are turned off at the entry interface, and the
aft RCS system is used to maneuver the spacecraft.
The spacecraft must dissipate the tremendous amount of kinetic
energy it has. It does this by varying the amount of aerodynamic
drag that it presents on the way down. This generates a lot of
heat because of the speed of the shuttle. This heating is controlled
by changing the speed of the shuttle in small amounts. This is done
by varying the aerodynamic drag of the shuttle. Most aircraft do
this by changing the Angle of Attack. When you pull up the nose,
an airplane tends to slow down, unless an engine is used to counteract
the drag. For a re-entering shuttle, the angle of attack must be
held constant to prevent the structure from overheating.
The shuttle controls drag by rolling into a series of 'S' turns along the
flight path. Increasing the roll angle of the orbiter moves the
direction of its lift (perpendicular to its wings) away from the
vertical, causing it to descend faster. These S-turns are used to
fine tune the energy level (A fancy way of saying altitude and
airspeed) of the orbiter, something like skiers turning while going
downhill to control their speed. When a dynamic pressure of 10
psf is reached (EAS of 62 MPH (100 km/hr)), when the orbiter's
ailerons become effective for roll control. At that point, the roll
RCS engines are deactivated. At a dynamic pressure of 20 psf (EAS of
85 MPH(138 km/hr), roughly), the elevators on the orbiter become
active, and the RCS pitch engines are deactivated.
In the Equilibrium Glide Phase of the reentry, the spacecraft is
flown to maintain a constant drag level, where the flight path angle
remains constant. This is maintained until the deceleration of the
orbiter due to drag is about 1G.
In the last phase of the reentry, the 1G deceleration level is held,
reducing the angle of attack as necessary, until the Terminal Area
Energy Management interface. The RCS system continues to control
Yaw until the rudder become effective at around Mach 3.5.
Columbia was lost either at the tail end of the Thermal Control
Phase, or the early stages of the Equilibrium Glide Phase. The
ailerons and elevators were providing control, (the Q at that point
was around 75-80 psf, or an EAS of about 170 mph (275 km/hr)), and
yaw was being controlled by the RCS thrusters in the tail.
Late reports before this writing this indicate that the Flight Control
System reported that it was correcting a left yaw/roll just before
breakup.
Swounger
Join Date: May 1999
Location: New York, NY USA
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The latest I'm hearing is that nasa knew there was trouble, they denied that using CIA spy satellites would have been able to see the tile damage, despite the CIA statements to the contrary, and they could have rescued them if they told them to start conserving from the day they saw the damage ie day two. They've also found debris in Califiornia and New York.
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25F
"2) Equilibrium Glide Phase. This is flight at a constant attitude as
the deceleration due to drag builds up to approximately 1G.
3) Constant Drag Phase. The 1G deceleration is held until the orbiter
enters the Terminal Area Energy Management interface, after which it
is flying as a conventional, but very heavy and fast, glider. This
is usually 52 NM (59 SM, 94 km) from the landing site, at an altitude
of 83,000', and a speed of Mach 2.5 (2500 ft/sec, 760 m/sec) The
orbiter slows to below Mach 1 at about 49,000', 22 NM (25 SM, 40 km)
from the runway. "
The decceleration has to be greater than one. Otherwise it is actually accelerating due to gravity and drag forces not being canceled out.
"2) Equilibrium Glide Phase. This is flight at a constant attitude as
the deceleration due to drag builds up to approximately 1G.
3) Constant Drag Phase. The 1G deceleration is held until the orbiter
enters the Terminal Area Energy Management interface, after which it
is flying as a conventional, but very heavy and fast, glider. This
is usually 52 NM (59 SM, 94 km) from the landing site, at an altitude
of 83,000', and a speed of Mach 2.5 (2500 ft/sec, 760 m/sec) The
orbiter slows to below Mach 1 at about 49,000', 22 NM (25 SM, 40 km)
from the runway. "
The decceleration has to be greater than one. Otherwise it is actually accelerating due to gravity and drag forces not being canceled out.