NASA seeks clues to onboard computer actions

Computerworld | FEBRUARY 05, 2003 | DAN VERTON

[Zavien Doombringer]

NASA investigators want to know if adjustments made to the position of the space shuttle Columbia during its last minutes by the vehicle's onboard control computers could have played a role in its breakup during re-entry Feb. 1. In a revised timeline of events released Feb. 3, Ron Dittemore, NASA's space shuttle program manager, said that at 8:59 a.m. EST, Columbia's five onboard computer systems began to detect a significant increase in drag on the vehicle's left wing and ordered two of the shuttle's four yaw jets to fire for 1.5 seconds to compensate for the change.

Investigators aren't sure yet whether the adjustments ordered by the computer played a role in the shuttle's breakup. "It was well within the flight control system's capability to handle the [maneuver]," said Dittemore. "But what is becoming interesting to us now is the rate of change."

While Dittemore acknowledged that NASA may never be able to determine the exact root cause of the crash, he said investigators are now studying all of the data from the launch process as well as the shuttle's flight control systems.

The focus on Columbia's flight control systems could be significant. On Feb. 3, Computerworld reported that Columbia and other space shuttles have a history of computer glitches that have been linked to control systems, including left-wing steering controls (see story).

Although officials said it's too early in the investigation to pin the blame for the crash on the control computers, 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.

Each computer's memory stores "telemetry of thousands of parameters that affect the flight of the shuttle," Readdy said.

Columbia and other space shuttles have experienced a series of control computer failures during the past two decades, including one that had a direct link to the spacecraft's left-wing control systems. During a March 1996 return flight, NASA officials discovered a computer circuit problem that controlled steering hardware on Columbia's left wing. The computer circuit was responsible for controlling the spacecraft's left rudder, flaps and other critical landing functions.

Speaking at a news conference prior to Columbia's landing in March 1996, NASA spokesman Rob Navius downplayed the seriousness of the computer problem.

"There are three additional paths of data that are up and running in perfect shape, and there's multiple redundancy that would permit a safe landing," he said. Although Columbia landed without incident that time, NASA officials said the failure was significant enough that had it happened earlier in the flight, the agency would likely have ordered the shuttle home early.

The General Accounting Office, the investigative arm of Congress, has also criticized NASA in the past for relying on the same commercial contractors to develop, test and validate the space shuttle software (see story).

However, Donna Shirley, the former manager of NASA's Mars Exploration Program and the team that built the Sojourner Microrover, said there is no evidence yet that flaws in NASA's software-validation program had anything to do with the disaster.

[OneLoyalAmerican]

Greetings Woody, FReepers, et al:
My days of writing ladder logic programs are over, but I am still interested in the field.
I've wondered if the shuttle PLC utilized ladder logic.

< tin foil hat mode> Perhaps the DDOS worm attack, while the Shuttle was underway, might have "masked" latent parameter adjustments to the Shuttle's PLC's ladder logic? < /tin foil hat mode>

[Cold Heat]

Interesting idea...........?

[rickmichaels]

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

I'm not so sure about that. The external tank was obviously travelling upward at the same speed as the shuttle itself. When that piece of foam broke loose, the wing indeed smashed into it because the shuttle was now travelling faster than the piece of foam, although the foam still had upward momentum. The foam was still travelling upward, although not as fast as the shuttle meeting up with it. The wing didn't hit a stationary object at 1500 mph.

[Cold Heat]

After thinking about it, e-mails did and were sent between the shuttle and the ground, but the systems are likely very much separated and different. I think?

[CCWoody]

I've wondered if the shuttle PLC utilized ladder logic. ~ OLA

I think that "ladder logic" is simply the name associated with all PLC (Programmable Logic Chips). Certainly, different manufactures of these chips will have different propietary software, but I think it is all generally called "Ladder logic" after the "good old days" when these type of controllers were literally ladders of relays and coils.

Perhaps wirestripper, who claims to be an LLP (Ladder Logic Programmer), has some better insight.

Sheesh, see what I mean about terminology. PLU, PLC, asic, etc....

Woody.

[Cold Heat]

Actually, ladder logic got it's name because it looks like a ladder, or more like a family tree diagram. You create the ladder and the put in timers, switches (no/nc) and other components as you would draw a schematic diagram. The program is basically sequential and has numerous sub routines and greater than/less than commands.

In short, it is a lot of fun!

[CCWoody]

Here, I found this on the internet (for those who haven't the foggiest notion about what we are talking about):


Ladder logic. That sounds like something painters and window washers would use and be good at. On the other hand, my plumber friend and his father both fell off the same ladder performing the same plumbing task at the same house with the ladder in the same position for each of their falls. If you were to poll me on who’s who of ladder logic, I’d say the couple of plumbers I know are definitely not experts at it.

Ladder logic came along in the fabulous 1960s and matured with the great music my teenagers think was written by contemporary rap artists. Unlike the rappers, ladder logic is an original and didn’t have much except relay coils to take anything from. In fact, I’d wager that some of our most popular micros took some pointers from the beginnings of automated industrial control in which ladder logic was a key player.

Ladder logic’s climb to popularity originated in Motown as auto manufacturers were trying to find a suitable replacement for the relay-based automation found on their assembly lines. Out went the relays and in came the Programmable Logic Controller (PLC), and right there with it was a newfangled programming lingo called ladder logic.

The new programming language adopted some of the old relay logic lingo. Ladder logic programs are full of relays, coils, and contacts. Some of these relay components are real and many more of them are logical, or, for a better word, virtual, as they only exist in the mind of the PLC.

[cyberaxe]

In short, it is a lot of fun!

.....your one sick puppy!.....

.....(LOL).....

.....used to have to do lots-o-that.....

.....now spending more time.....

.....debugging our accounting software.....

.....(the "off the shelve" type at that!).....

[Cold Heat]

The stuff I did related to automated systems for machinery and the like. Sensors, like temp. proximity, speed and control status were inputed to get the desired result. A idiot proof system that worked under any foul up or failure of any individual component. It also would trouble shoot it's self so that failures could be identified and repaired quickly.

Operator interface was minimal. The programs often took months to develop and test.

I am sure the shuttle systems use a similar program, as even back then, I used a intel computer to do the program. I then transferred the program to the processors internal memory. The memory was permanent, but could be modified if you had the program to do it.

[Cold Heat]

.....your one sick puppy!.....

Not the first time someone inferred that, LOL!

I used to live and breath this stuff while sleeping.

[FReepaholic]

>>...I think if one knew the frame speed of the slow motion video ...<<

Standard video is approx. 30fps (frames per second). Generally, the long range tracking telescopes use a 35mm high-speed film camera at 96fps and standard video. At least until 1998 when I last worked at KSC. Could be different now. There are high-speed video units but I don't know if they are used out there.

[cyberaxe]

Some of these relay components are real and many more of them are logical, or, for a better word, virtual, as they only exist in the mind of the PLC.

.....ah.....

.....the dredded logic statement.....

.....(those will toss the operators a "loop").....

[Letitring]

Not to mention all the times NASA computers were hacked, during the Clinton years.

[Flyer]

a tile known to crack from the impact of a quarter dropped from two feet.

A photo of a recovered wing piece shows intact tiles. They survived the initial disintegration and 40 mile fall to earth.

[TheDon]

"Hey, you'd think NASA would be eager to blame this on the insulation impact at launch."

I disagree. Anything but that. If that is the cause, heads will roll at NASA as they knew about it and dismissed it.

[js1138]

I guess they'll be looking for the woman who was seen running off with a circuit board found lying on the highway.

[larry bear]

The foam's velocity would have immediately decreased due to the air resistance. The shuttle would have high at the differential speed. Not exactly a 100foot fall

[Cold Heat]

.....the dredded logic statement.....Yes, most of it is virtual but on the stuff I used the virtual statements were a different color. The feedback loops from the switches and sensors and incremental generators flashed and/or had a ID#.

[Moonman62]

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".

Consider this: there is still atmosphere where this happened, and the air isn't moving along at the speed of the shuttle or the foam. Therefore, the foam would start to slow down rapidly because of wind resistance, while the shuttle was still accelerating.

[CCWoody]

A idiot proof system that worked under any foul up or failure of any individual component. ~ wirestripper

Yeah, right! You obviously needed to find better idiots. Besides, if you truly had an idiot proof system, only an idiot would want to use it. hehehe!

The memory was permanent, but could be modified if you had the program to do it. ~ wirestripper

Most PLC's or ASICs (Application Specific IC's) that I have built (Opps, there goes my engineering expertise) use either a EEPROM (Electrically erasable programable read only memory) or a UV erase type. I was even part of a group once who made chips that were put onto the shuttle, though, I think none of them were the PLC's.

Woody.