NASA seeks clues to onboard computer actions

Computerworld | FEBRUARY 05, 2003 | DAN VERTON

[tm22721]

2.5 pound debris hits at 1500 mph

Remember the shuttle is also going 1500 mph. It is the delta velocity between the debris and shuttle that is important. Delta velocity is pretty low that is why NASA discounted this as a problem.

BUMP

[mikegi]

"But what is becoming interesting to us now is the rate of change."

It's been many, many moons since I had control systems class, but any professional control system would be damped enough to prevent it from overshooting the target (ie. overcompensating and causing a spin to the right). I think that what he's hinting at here is that the rate of change to the left couldn't be handled by the control system and that the shuttle spun to the left. Probably because the controls on the left were comprimised.

[Cold Heat]

was so short a small change in velocity caused it to "fall back"

Yes, and the larger the object, the slower it would have accelerated.

[clamboat]

2.5 pound debris hits at 1500 mph a surface which is damaged by a human fingernail.

1500 mph!?! Back that up with a shred of evidence. Maybe you're someone who never took a basic physics course in 8th grade, or if you did you weren't listening.

The debris (whatever it was) fell off the top of the main fuel tank. That fuel tank may have been travelling at 1500 mph, but so was the debris, and so was the shuttle strapped to the tank.

Upon impacting the wing, the debris would have had a relative velocity equal to how much it slowed since falling, plus however much the shuttle itself accellerated in the time it took the debris to go from the top of the fuel tank to the wing.

You are suggesting that the debris decellerated to 0 mph so the shuttle wing could hit it at a full 1500 mph? Or perhaps you suggest that in that fraction of a second, the orbiter and the attached fuel tank accellerated an extra, say 1000 mph, to meet the decelerating debris at 1500mph?

[Tandem]

Both the foam and the shuttle were going at 1500 mph, so the foam didn't hit at that speed. Once it came loose, it started to slow, while the shuttle continued to accelerate. In the second or so after it separated, the estimate was that the difference in speed was 500 mph or less. The engineers doubled that, for sake of analysis, and looked at the strike at 100 mph. It still didn't appear to be a "fatal" strike, as it was a glancing blow.

[OldFriend]

The turns were explained as required to slow down the shuttle as it entered the atmosphere and readied for landing.

[CCWoody]

I assume they use a subroutine that used to be called fuzzy logic, which allows them to learn from their situation and make appropriate adjustments as conditions change. ~ wirestripper

No, you have your terminology mixed up. You are most likely referring to a type of control system called a "feedback control loop". Fuzzy logic, unlike binary logic, which has only 2 states for the flip-flop (on or off), will have transistors that have 3 or more discrete states.

Though fuzzy logic systems have their place today, I doubt that the shuttle computers use them. If my memory serves me, the shuttle employs an 8088 type of processor that Intel put into computers before the advent of the 286 computers. Though, they could have upgraded the computer systems making my knowledge obselete.

Woody.

[BraveMan]

Link to the original article:

http://www.computerworld.com/securitytopics/security/recovery/story/0,10801,78201,00.html

Link to the related article mentioned:

Columbia, other shuttles have history of computer glitches

[Zavien Doombringer]

In the video, I did see the foam separate, but not hit the wing. Boundary layer of air around the tank would have caused a vacuum (low-pressure) and "pull" the chunk back towards the tank, which I do see...

[BraveMan]

Dittmore stated the Delta Velocity was between 513 - 1032 MPH at the time of the incident . . .

[Cold Heat]

Thanks Woody!

I have been out of the loop, so to speak, on processor control since my days with Allen Bradley and Honeywell.

I am sure the new stuff is much better than the old days.

[Tandem]

I meant the engineers assumed the relative speed to be 1000 mph, not 100 mph.

Also, the foam was as soft or softer than the tiles. That is why it appeared to "pulverize", when it struck.

[Zavien Doombringer]

I agree, it wasn't the foam slowing down, it was the craft speeding up! The lack of thrust on the foams/ice part causes it to look like is slowed. Had the velocity remained constant, the foam would look like it was "floating".

[Cold Heat]

Yes, I considered a tank strike as well, and it is very likely.

Also, the after shot with the low res cam did not show any damage at all. If it were major damage the white exposed tiles would have shown on the image.

[glock rocks]

William Readdy, deputy administrator of NASA, said officials are actively searching for any of the shuttle's five onboard computer systems. Although it's unlikely they survived the crash, he said, the computers have "memory resident in them" that could shed light on the status of the shuttle after communications were lost with ground control.

okay, i wasn't imagining things yesterday... i was time traveling :o)

[Rain-maker]

    Rest in peace for the crew of STS-107

 

Time to start implementing a new space delivery system other than the shuttle which is coined in NASA as the "Flying Brick".

Phase out the old and bring in the new. 

 

                                                          http://www.spaceislandgroup.com/shuttleII.html

 

Shuttle II Cost Estimates

 

• Engineering of 2nd Generation Shuttle: $4 billion
  
• Development Time: 3 years
  
• Production Cost of 2 Second Generation Shuttle Prototypes: $600 million each.
  
• Target Commercial Selling Price of 25-50 vehicles: $400 million each
  
• Target Launch Cost of Second Generation Shuttles (excluding ET/ACC and liquid booster tank costs): $10 million
  

[isthisnickcool]

To get a birds eye view of the liftoff and how fast things get moving see the videos here.

[Zavien Doombringer]

Time to start implementing a new space delivery system other than the shuttle which is coined in NASA as the "Flying Brick".


I thought that term was coined for the F-4 Phantom II

[VadeRetro]

The debris (whatever it was) fell off the top of the main fuel tank. That fuel tank may have been travelling at 1500 mph, but so was the debris, and so was the shuttle strapped to the tank.

The truth is somewhere in between. The chunk fell off because it has been grabbed by the tremendous drag pressure of that 1500 mph slip stream. By the time it hits the wing, it hasn't gained the full relative velocity to the spacecraft that the slipstream has, but it's got about 500 mph worth. That's still a fair energy even for a chunk of foam.

[VadeRetro]

Dittmore stated the Delta Velocity was between 513 - 1032 MPH at the time of the incident . . .

Didn't see this before I posted. You got it.