NASA seeks clues to onboard computer actions

Computerworld | FEBRUARY 05, 2003 | DAN VERTON

[chimera]

It is clear that loss of control pre-dated significant burn-through. The big question is what caused the loss of control. Telemetry data to date indicates escalating port drag, which to me says there was some mighty disturbed airflow on that side relative to the other. Some even speculate that the port gear cover came off over California.

The loss of those sensors points to some kind of symptom and if it was a common mode failure then that would be a big indicator of where the damage occurred. I imagine they are looking at wiring runs in the area of that wheel well. If something there took out the signal conditioner(s) or common cable run for the sensor leads to the trailing edge thermocouples and tire pressure sensors, then the same event could have popped open the wheel well cover. A lot of people will think tire explosion, but what caused that?

If it was a popped open wheel well then I wonder if there is telemetry indicating the state of the well door? Remember there are (or were, on early flights) pyrotechnics that would assure a positive opening of the gear bay doors on landing approach. Could one of those have gone off? Those are supposedly safed until the approach phase but who knows? Surely such an event would have been detected by the crew or shown on telemetry. I am reminded of the mystery hatch cover blast on Liberty Bell 7 after Grissom landed the capsule after his suborbital hop. Everyone said the explosives couldn't have gone off spontaneously but Grisson said they did.

[betty boop]

As we know, the SRB "O-ring" seal failed. However, many seemingly benign events, combined with bad assumptions, and poor risk assessment decisions predisposed the seal failure.

Well, live and learn, OLA. Isn't that what life's all about? Meanwhile, don't take any wooden nickels.

[Willie Green]

Well I guess it's clear what your take is on my humble little scenario.

I'm sorry if that's what I inadvertently implied,
That was not my intention.
I was just looking for a way to post a link to the article I had posted before this tragedy occurred.
In hindsight, I'm upset more than ever that someone in NASA would have wasted the astronauts' time with such frivolous and disgusting nonsense.

[SauronOfMordor]

On a system like the Shuttle, especially after 20+ years of operation, the software is much harder than the devices it acts on. Software doesn't age. It doesn't get brittle or develop stress cracks. Software only gets better with age.

I've been a software developer for over 25 years, and I strongly disagree with you. Software does age. People put changes in it to deal with new situations, to deal with new equiptment, etc. A design that was initially "clean" will, over years and many patches, become more convoluted. Eventually in the life of a piece of software, after patch on top of patch, it becomes unmaintainable and is better off being rewritten.

I'd look first for some fatal mechanical failure as the root cause. It could be from an external event, human error or simply an age or stress related failure.

I agree. That was my first post on this thread, namely that some unanticipated mechanical failure caused the software to make a bad decision that resulted in an overcorrection and a cascade of further problems

[SauronOfMordor]

Few if any companies have the money, manpower or luxury of time to devote to the intense simulation regime that NASA uses. That software has been through the wringer for 20 years and it just seems that if a fatal flaw were there, it would have been spotted long ago.

One thing I've learned the hard way over the years: a simulator can only simulate the assumptions of its designers. The real world inevitably has surprises

[tubebender]

While some theories are easily discounted as hopelessly irrelevant; others, like your hubby's strut mount/wheel cover theory, could play a role.

Dittemore spoke of a possible strike of the tether strut port covering or door yesterday. I would think they had telemetry noting its closure ? It is covered with tile also.

I asked yesterday if the ET was recoverable and someone said it burns up on reentry ?

[betty boop]

In hindsight, I'm upset more than ever that someone in NASA would have wasted the astronauts' time with such frivolous and disgusting nonsense.

Willie, if you mean the "piss as art" project, then I couldn't agree with you more. For one thing, there's no way that I could imagine (at very least) how such a concept could be restated as any kind of a bona fide scientific experiment. Then -- prompted by you -- I get to wondering how long this particular "experimental design" might have been in the offing. And also why it hadn't been killed long before now, as the total waste of taxpayer expense that (arguably) it clearly is, in fact.

The ancient Chinese Curse has come true for us Americans: We do indeed live in interesting times.

Thanks, Willie. Great to hear from you.

[the_doc]

It's not that simple. This was 2.5 pounds of low-density and readily-deformable material. This markedly reduces the damage potential.

(Potential for collision damage involves issues of size and shape and density and elasticity in addition to total mass and velocity.)

I have heard elsewhere on FR that NASA had previously done tests of foamed insulation hitting the shuttle at high speed and had concluded that it's not necessarily a problem. I haven't seen the data, one way or the other, but as a former engineer, I would urge FReepers to take a wait-and-see attitude.

[Not now, Not ever!]

I tried four hours of sunlight once, to no effect, gave up and got a black light.

[El Gato]

don't know of 80 degree turns make sense. Where did you read that? Here is what I dound on the standard de-orbit procedures:

At an altitude of approximately 30 miles, the orbiter makes a series of maneuvers and S-turns to slow its speed

Those "S-turns" are your "80 degree turns". Unless they meant and 80 degree angle of bank, I don't think it seems all that excessive.

[El Gato]

At that altitude, its hard to imagine the control surfaces being all that effective.

Not when you're going on the order of Mach 18 or so, you get plenty of control force from the control surfaces. The fact that the RCS (thrusters) kicked in is what is unusual.

[Moonman62]

I asked yesterday if the ET was recoverable and someone said it burns up on reentry ?

It usually burns up over the Pacific. There are, however, pictures of the ET after separation.

[Moonman62]

I've been a software developer for over 25 years, and I strongly disagree with you. Software does age. People put changes in it to deal with new situations, to deal with new equiptment, etc. A design that was initially "clean" will, over years and many patches, become more convoluted. Eventually in the life of a piece of software, after patch on top of patch, it becomes unmaintainable and is better off being rewritten.

IIRC, there are three flight control computers. Each one gets a "vote" about what action to take. I assume they would not put a patch on all three at one time.

[El Gato]

The F-4 was always called the "flying brick" by us mechanics, it wasn't with out saying "goes to prove if you strap powerful enough engines (j-79s) to a brick, it will fly"

And before that the "Lead Sled", the F-105, demonstrated the same thing with a single J-75 26,500 lbs of thrust verses 17,000 for a single J-79 (in each case depending on the engine/aircraft varient)

[El Gato]

And if there's a bug in that section of code, it may turn a "somewhat wrong" situation into a "catastrophicly wrong" situation. I would take a good hard look at the possibility that unusual drag (or loss/corruption of sensor input) may have caused the computer to overcorrect at Mach 20 (with disasterous results).

I was thinking along the same lines. Although the first time I got there was thinking about deliberate "bug" in the code. I wonder if they did a new build of the code prior to this mission, or if conditions with the heavier bird, were just enough different to trigger the "bug"?

[Cold Heat]

Those "S-turns" are your "80 degree turns".

I am afraid you have posted to the wrong person, as I have never made any mention of a 80 degree S turn. I did not give any degree of turn since I do not have any idea at all what the turning degree is.

[Cold Heat]

Unless they meant and 80 degree angle of bank, I don't think it seems all that excessive.

You must have seen second briefing, because that issue was covered. A reporter asked about the bank and Mr. D said the 80 degree bank was not excessive and within the upper range of nominal.(or something to that effect)

[I_dmc]

What if there was no drag to compensate for?

[foghornleghorn]

The debris would not hit at 1500 mph, but more like 32 ft/sec, since it fell about 32 feet. The tank is traveling at the same speed as the shuttle and the foam covering, when it breaks away, essentially falls like any object subject to gravity. The air, if there was much at that altitude, would affect it somewhat also. But it struck the shutle at nowhere near 1500 mph.

[Shanty Shaker]

You are forgetting that the chunk of foam had a speed relative to the speed of the shuttle not equal to the speed of the shuttle.