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NASA Avoids "Happy New Year" On Shuttle
ClickOnThis noted that NASA is actually avoiding a Shuttle in Space over New Years. It says
"The worry is that shuttle computers aren't designed to make the change from the 365th day of the old year to the first day of the new year while in flight. NASA has never had a shuttle in space December 31 or January 1. 'We've just never had the computers up and going when we've transitioned from one year to another,' said Discovery astronaut Joan Higginbotham. 'We're not really sure how they're going to operate.'" You may notice some deja vu while reading this story. Sorry. Not much happens on Sundays :)
they have a Y2* bug?
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In reality isn't this a design limitation rather than a bug in the implementation?
liqbase
Verdict from last time:
No they can't run linux, linux is not something you use to fly a shuttle with people in it, can't support the hardware and it was written 30 years ago.
And no, it's not easy to fix bugs in a piece of software like this.
How many places would you have to put that code in and could you be sure it will work?
How do you know the leapyear code works?
Wouldn't your code have to do a year++ line?
Does it matter which direction they are travelling, is it not possible to technically flipflop between one year and the next based on where you are flying over?
What will happen to systems if the day variable is less than the previously stored one, will it cause the ship to flip out and attempt a burn?
Too many factors, nasa is right at the moment.
liqbase
It's probably a little harder than you think. If the space shuttle were MS Notepad, your idea would probably work without a hitch. We'd start it up, wait for the new year to roll over, and then test to see if we could still type and a save and open documents. Test done.
The space shuttle is monumentally complicated. It's controlled by multiple computers. Test cases aren't just typing some stuff in and clicking on a few menus. The computers are hooked up to instruments and relays and motor controllers, and all of that would probably have to be convincingly "faked" for the test to be rigorous.
It doesn't, in the sample provided anyway. If $leapyear is true, $day never gets set back to one...
In any case, they already need to contend with uneven numbers of days in each of the various months anyway, and have to contend with leapyears every February 29th. So they're already (successfully) dealing with incrementing days, and months. I fail to see how they can't cope with years as well... C'mon, this is NASA and it's not the 1970's any more.
Once space travel approaches the speed of light I'll start to buy excuses about the difficulties of tracking time. Until then, sorry - No Sale.
All right, I realise you were trying to be funny but it is a serious point. Progress is systems design is so rapid that stuff from the 70s and 80s is like something from another world - when the Shuttle software was being written, I was working on a reasonably state of the art system in which every critical function had to be written in assembler and the compiler output had to be hand edited - even after we had upgraded the CPU specification to the point that the EMP people were complaining that the only components on the CPU board that they had in their library were the resistors.
Getting really philosophical for a moment, how about this for a sobering thought? We still have the materials and skills to maintain medieval cathedrals. We could probably, without too much trouble, crew and maintain an 18th century ship. We can easily maintain a 19th century railroad engine. We still have early 20th century motor ships in service. We can (with difficulty) keep aircraft from WW2 flying. But keeping a 1980s reusable spacecraft going is extremely difficult, and a 10 year old mobile phone is about as much use as a chocolate teapot.
Pining for the fjords
It's a DUUUUPE.
So, to forestall any of the previous idiotic comments;
Oh, and for the most ridiculous of stuff: Linux is not an option for critical shuttle systems; it is not a reliable RTOS - when you are orbiting at 18,000mph, a 1 second error puts you miles off course, though Debian was used at least once in monitoring an onboard experiment.
Can we all move on?
Leben Sie jetzt die Fragen.
Sorry about that stupid post. Yes of course the Shuttle computers are programmed in HAL and in fact I knew that, if I only had woken up my older brain cells.
Pining for the fjords
When not designed by an idiot, a system clock is a linear device that measures the elapsed time since some reference "moment in time". It doesn't know that it's Thanksgiving, New Years, or any other socially significant but otherwise irrelevant date. It has sufficient resolution to measure the smallest interval of interest and sufficient range to outlive the system.
If the shuttle system clocks use year, month, day, etc., there's a lot that should be done, not the least of which is finding whoever made the design decision and take him out to a public place where thousands of engineers and programmers will point at him and laugh.
I'm a Programmer. That's one level above Software Engineer and one level below Engineer.