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Forget Cricket Talk about anything [within Board Rules, of course :) ]

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  #1  
Old August 12, 2004, 09:54 AM
Tintin Tintin is offline
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Default They write the right stuff

An old article. Those who are working in the software field should find this impressive :

"But how much work the software does is not what makes it remarkable. What makes it remarkable is how well the software works. This software never crashes. It never needs to be re-booted. This software is bug-free. It is perfect, as perfect as human beings have achieved. Consider these stats : the last three versions of the program -- each 420,000 lines long-had just one error each. The last 11 versions of this software had a total of 17 errors. Commercial programs of equivalent complexity would have 5,000 errors."

Right Stuff
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  #2  
Old August 12, 2004, 09:57 AM
Arnab Arnab is offline
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Nice one. Thanks.
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  #3  
Old August 13, 2004, 12:43 AM
fab fab is offline
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hmmm Tintin, is this the article we were debating about with my colleagues? Do you still believe this level of excellence is achievable by commercial companies with commercial deadlines?
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  #4  
Old August 13, 2004, 01:46 AM
chinaman chinaman is offline
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How about a new "Huston, we have NO problem" movie?
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  #5  
Old August 13, 2004, 11:04 AM
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AsifTheManRahman AsifTheManRahman is offline
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yeah good stuff
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  #6  
Old August 14, 2004, 01:54 AM
fab fab is offline
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Quote:
Originally posted by chinaman the MEMBER, not the MODERATOR
How about a new "Huston, we have NO problem" movie?
Wasn't that a hardware failure?!
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  #7  
Old August 14, 2004, 02:07 AM
chinaman chinaman is offline
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Well, while a complete software success is attainable, similar success with the hardware is a far cry, probably because of wider use / misuse (injury from pencil)
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  #8  
Old August 16, 2004, 06:02 PM
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BushidoTiger BushidoTiger is offline
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I'd the good fortune to meet some of those Houston folks when they came to JPL, Pasadena.
Although, we deal with the unmanned spacecraft, most of the advanced computing research is done here at the JPL/CalTech collaboration.
A lot of these software guys at the Advanced Computing are truly writing bleeding edge stuff. Unlike those from commercial world, these guys tend to be gun shy, stay out of limelight.
JPL, and NASA in general are high on procedures/policies/directives. When I started as a telecom guy (EE), these procedures would drive me crazy. It seemed like you can mover your pencil from pt. A to pt. B w/o, going thru some exception/waiver request/approval, some study on the system impact of the pencil removal etc.
On other side, not unlike those folks at Houston, the policy of sticking by the book is a widely adapted culture.
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  #9  
Old August 16, 2004, 10:17 PM
Tintin Tintin is offline
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>> Wasn't that a hardware failure?!

That was a 'beautiful' error :

Quote:
The series of events that led to Apollo 13?s life-and-death drama began five years earlier with a simple design change to the Apollo spacecraft.

During flight, the systems aboard the command and service modules were designed to operate at 28 volts. In 1965, however, it became clear that during preflight tests at the Kennedy Space Center, 65 volts would be used. That year, engineers at North American directed that the craft's electrical components be redesigned to accept both levels of voltage.

But one crucial participant never got word of the change.

Within the service module were two tanks of liquid oxygen. Oxygen from these tanks was used not only for the astronauts to breathe, but to help run three fuel cells that provided electrical power to run the command ship's many systems.

Inside each oxygen tank was a thermostat which, along with a heater, was used to regulate the temperature inside the tank. It was the manufacturer of this thermostat that never learned of the need to accept 65 volts of electricity.

All things being equal, that might not have been a problem. In fact, the oxygen tanks used on all previous Apollo missions had flown without trouble. But the Number 2 oxygen tank aboard Apollo 13 did have a slightly tarnished history.

In October 1968, the Number 2 tank eventually used on Apollo 13 was at the North American Aviation plant in Downey, California. There, technicians who were handling the tank accidentally dropped it about two inches. After testing the tank, they concluded the incident hadn't caused any detectable damage.

The dropped tank was eventually cleared for flight and installed in Apollo 13. The tank passed all of its routine prelaunch tests. But at the end of March 1970, after a practice session called the Countdown Demonstration Test, ground crews tried to empty the tank -- and couldn?t.

The small tube used to fill and empty the tank of its supercold contents had been damaged by the mishandling almost two years earlier.

To get around the problem, workers turned on heaters inside the tank to warm up the remaining liquid oxygen, turning it into gas that could then be vented to the outside. The thermostat inside the tank was supposed to prevent the temperature from exceeding 80 degrees Fahrenheit (25 degrees Centigrade).

But as the temperature inside the tank rose, the thermostat was activated, and the oversight from 1965 came into play. The resulting surge of electricity at 65 volts caused the 28-volt thermostat to weld shut. Technicians failed to notice the situation, and during the procedure to empty the tank, temperatures inside rose to 1,000 degrees Fahrenheit (500 degrees Centigrade). The intense heat damaged some insulation on wiring inside the tank.

No one knew it, but when Apollo 13 lifted off, it carried the makings of a small bomb inside its service module.

The "bomb" was triggered on the evening of April 13 when ground controllers asked Jack Swigert to turn on the fans inside the service module's two liquid-oxygen tanks, as a way of stirring the contents, to allow more accurate quantity readings.

When the fan inside the Number 2 tank was turned on, the damaged wiring caused a spark, starting a fire inside the oxygen tank.

With pure oxygen feeding the fire, the pressure inside quickly grew to the point where the tank burst open, at the same time damaging much of the other plumbing inside the densely packed service module and crippling the spacecraft.
http://www.space.com/news/spacehisto...re_000413.html
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