PDA

View Full Version : Shutle Columbia: What is Known so far



dgavin
2003-Feb-02, 02:57 AM
I've been watching the late (6:44pm PST) Press conference on Nasa TV. Here are some Facts they were able to announce.

The temperature/presure sensors failed in succsession from the back of the left wing towards the front over a time of about four minutes. At no time did any of the sensors detect any level of heat or pressure annomolies before thier failure.

(this sort of hints it wasn't a tile/impact issue, but nasa hasn't ruled that out yet either)

No information is know as to why they failed, other then something related to wiring. Thier failure at this time may or may not be related to the accident at all.

The shuttle was in the correct plane of re-entry and was not at an incorrect angle when the catastrophic failure occured.

Nothing else is known yet. (It could be a fuel leak that froze a wiring harness causing it to crack and then spark, the left wing could have simply torn off, or it could of been a micro meteroite impact.)

Nasa is trying to determine if the explosion was the result of some other failure, or if the the explosion occured first. It's looking like the investigation will take quite some time for answers to be sifted out of the wreckage.

AstroGman
2003-Feb-02, 05:41 AM
Ahhh,I see.Thanks 4 the info!!Keep us POSTED!!

JayUtah
2003-Feb-02, 06:50 AM
Pure speculation contained herein.

The failure of sensors in a locality-based pattern is one of those clues that can really mean many things. However in this case it probably means that the locality of the sensors is related to the progression of the failure in the proximal structures.

"Off-scale-low" readings as a sensor failure mode points to damage in the transducer itself. Depending on wiring geometry, it would contraindicate failure in a wiring harness or in the signal conditioning assembly, except under somewhat improbable circumstances. Progressive damage to a wiring harness or localized damage to an SCA would cause progressive loss of data from sensors, but in a random order.

The lack of high-temperature readings prior to failure seems suspicious. This suggests failure of the transducer from mechanical stress rather than overheating, which indeed contraindicates thermal overloading of the structure subsequent to loss of the heat shield.

However, in some thermal transducers you get an off-scale reading when the sensor wires are shorted. This could follow thermal erosion of the electrical insulation. I don't know if the transducers used on the shuttle were of this type.

I'm interested in the reports of elevon excursions and where they fit in the timetable. Was the flight control system responding to something (unlikely, since NASA is reporting correct attitude), or might we be dealing with an uncommanded elevon deflection?

aporetic_r
2003-Feb-02, 06:54 AM
Thank you, Jay. As I've said in reference to the Apollo Hoax discussions, in these matters I trust your speculation more than I trust most people's facts.

Aporetic

JayUtah
2003-Feb-02, 07:10 AM
Unfortunately it's still speculation. I can only give hints as to how engineers will likely look at these clues. And I'm hampered, as everyone else, by having to get all the clues via the media who won't always give you all the relevant clues and won't always get the facts right.

I've spoken at length here and elsewhere about the mental processes that occurred during and after the Apollo 13 explosion. We must not allow ourselves to form an early hypothesis and then "filter" subsequent evidence based on that hypothesis. We must truly keep our minds open to any possibility that can't be ruled out.

Fortunately (or unfortunately as the case may be) I decided to spend the night in a cabin up in the mountains last night and didn't hear anything about this until nearly seven hours after it occurred. So there was already a fair amount of information for me to absorb initially.

Even still, I'm simply trying to give some implications of the data that's being presented, as I see it. It's far too early to be drawing any conclusions, or even to think that we have appropriate data.

dgavin
2003-Feb-02, 07:46 AM
An update from Nasa TV, as of 11:39pm PST

Nasa has announced that they have slowed down the production of the external fuel tank, booster rockets, and other hardware for future shuttle flights.

They also stated, "We will not lauch another shuttle until we come to an understanding of what occured during this mission."

They ammended the previous information by stating there was an increase in tempature on two sensors of the left wing before they failed. The left wheel and brake line temperature sensors.

Thats about it for now.

dgavin
2003-Feb-03, 12:50 AM
Nasa TV Update 4:34 pm PST

Some Updated Information on Shuttle Accident, presenting them in order of events.

Four Sensors along the back of the left wing failed.

The Tire and Brake line Temperature Sensors in left wing registered a 20 degree rise in temperture before they failed.

The left Elevons began compensating for an increase in drag along the left side of the shuttle.

Further sensors in the left wing failed.

The wiring of the left wing sensors are routed around the frame work of the wheel well.

Sensors along the main left fuselage above the wing indicated a 60 degree increase in temperature, compared to 15 degree increase from the corresponding right side.

The left Elevons compansated for more drag drag along the left side of the shuttle.

Left side Tire and Brake Pressure sensors failed, which triggered a minor alarm light in shuttle.

Last Voice Radio contact occured. Loss is being attributed to do Plasma Envelope EM interference. (This normally happens during re-entry when shuttle is at Mach 17 to 19).

An additional 32 seconds of computer data was received after this point, but is still being anaylzed.

Hope this helps, I'll post more as I Catch it on Nasa TV.