USAF feels Oleg's pain

[baronWastelan]

Originally Posted by dduff442

From Mariner 1 via Ariane 5 to the SAAB Gripen prototype, the history of software in aviation is dismal. If a civil engineer built a bridge that collapsed, he'd be ruined. A software engineer builds his bridge again and again - hundreds of times - and when it finally stands up on its own there's a big party.

Thankfully physical modelling like Il-2/SoW has a better record than most, but many large software projects exhibit not just a lack of competence but a lack of understanding of the most basic precepts of engineering. It's not just that many big IT projects end up non-functional, they start out with designs that couldn't function in the first place. Computer Science grads need to be taught the difference between provable and non-provable designs and how to test ideas.

dduff

That's quite funny, but is it a fair comparison? People have been been building bridges for 1000's of years, and they all do practically the same thing. A single piece of software can do 100's of different things, many of them that have never been done before.

[Azimech]

Originally Posted by dduff442

From Mariner 1 via Ariane 5 to the SAAB Gripen prototype, the history of software in aviation is dismal.

I can give you an outstanding exception: the Voyager program.

[dduff442]

Originally Posted by Azimech

I can give you an outstanding exception: the Voyager program.

I wasn't familiar with this at all, but a trip to Wikipedia turned up the following:

Originally Posted by Wikipedia

Voyager 2's gyroscopes and its computer were operational during its Titan/Centaur launch phase, monitoring the sequence of events, in order for those systems to take over the space probe's attitude control and other functions upon separation from the Centaur upper stage. But at that point, the unexpected happened: Voyager 2's computer experienced robotic "vertigo". In its confusion, it helplessly switched to backup sensors, presuming its "senses" to be defective.

Voyager 2's disoriented flight-control computer remained disconnected from Voyager's powerful thrusters at this point, so it did not cause damage to the launch during the launching itself. The Centaur's attitude-control system stayed in charge, suffering no "vertigo" and, as planned, it electronically corrected the disequilibrium of the Voyager's computer just before separation.

From the spacecraft's control center, engineers and technicians helplessly watched the antics of Voyager 2's disoriented computer. One hour and 11 minutes after lift-off, Voyager 2's own dedicated solid rocket fired for 45 seconds, to supply the final increment of momentum that it needed to get to Jupiter.

I don't mean to knock the potential of software or the talent of its practitioners. What gets me is that the structure of the different markets makes production of quality software uneconomical in many cases.

Put any two software engineers side by side and probably one is a gold mine while the other cancels out his own limited production capacity by pumping garbage into the system. The problem is if you look at their CVs (Resumes), you'll likely never be able to guess which is which.

dduff

[dduff442]

Originally Posted by baronWastelan

That's quite funny, but is it a fair comparison? People have been been building bridges for 1000's of years, and they all do practically the same thing. A single piece of software can do 100's of different things, many of them that have never been done before.

Mmmm... depends on your definitions of 'do' and 'things'. Modern structures are complex and require careful analysis regarding the transmission of stress to the ground, possible resonance due to wind or earth tremors etc.

The claim that computers do things that have never been done before is dubious... Alan Turing determined universally exactly what computers could do. Other mathematicians determined things that computers could *not* do -- NP complete problems etc. I don't know a massive amount about any of this, but its fair to say that Turing spoke a totally different language to software engineers.

It's reasonable to question the fairness of the jibe I made -- usually nobody need die because a computer programme crashes, unlike with collapsing bridges. Some of the excuses made by the industry don't stand up to criticism, however.

Taking the internet as an example, it was built by electronics and fibre optics specialists and jpeg/mp3 etc (all basically the same tech) made it fast, cheap and economical. Microsoft and Netscape, OTOH, bequeathed us javascript, popups and security holes. Even when I think of the internet myself I think software, but it's an illusion. The hardware basically always works reliably but its invisible. The software types control the branding and somehow come away with all the cash...

dduff

[airmalik]

Originally Posted by baronWastelan

That's quite funny, but is it a fair comparison? People have been been building bridges for 1000's of years, and they all do practically the same thing. A single piece of software can do 100's of different things, many of them that have never been done before.

I agree. Building bridges can't be compared to building software. This article does a pretty good job of explaining why:

http://gamearchitect.net/Articles/SoftwareIsHard.html

[swiss]

Originally Posted by Azimech

Can you believe carmakers wish to delete the physical connections between steer-wheels and pedal-brakes? I'm no luddite, but this goes too far. In a car you don't have the time to switch on a backup like in a plane.

I thought we are already there.

Not a single of those jets can fly in space yet the Space Shuttle's software is incredibly tiny in comparison. Instead of all those fancy computerized gizmo's why not develop a plane that can fly to twice the altitude of your competition so you can again dictate any rules of engagement? Think the X15 had a computer on board?

The shuttle has ~2million lines.
http://www.nap.edu/openbook.php?record_id=5018&page=10

and:

The book "Code Complete" by Steve McConnell has a brief section about error expectations. He basically says that the range of possibilities can be as follows:

(a) Industry Average: "about 15 - 50 errors per 1000 lines of delivered code." He further says this is usually representative of code that has some level of structured programming behind it, but probably includes a mix of coding techniques.

(b) Microsoft Applications: "about 10 - 20 defects per 1000 lines of code during in-house testing, and 0.5 defect per KLOC (KLOC IS CALLED AS 1000 lines of code) in released product (Moore 1992)." He attributes this to a combination of code-reading techniques and independent testing (discussed further in another chapter of his book).

(c) "Harlan Mills pioneered 'cleanroom development', a technique that has been able to achieve rates as low as 3 defects per 1000 lines of code during in-house testing and 0.1 defect per 1000 lines of code in released product (Cobb and Mills 1990). A few projects - for example, the space-shuttle software - have achieved a level of 0 defects in 500,000 lines of code using a system of format development methods, peer reviews, and statistical testing."

http://amartester.blogspot.com/2007/...s-of-code.html

I like computers, that's not it. But I rebuilt my own 25 year old car and thank myself, I can repair it all by myself. The only computers that thing has operate the digital dash and the radio.

I have a 20year old car too, stored for the past 5 years - but last time I checked it was plagued by electronic bugs - not even related to SBEC.

[Azimech]

Interesting read!

[swiss]

Originally Posted by julian265

+1 to that. Hydraulic brakes are so simple and reliable... Perhaps a good reason to change it is if you have a completely automated braking system, but my experiences of ABS have been poor, with it degrading braking on surfaces other than smooth bitumen roads. I'll never forget the ~2003 camry that chattered it's way into an (empty) intersection, after we started braking side-by-side coming down a wet road on a slight hill. My '83 car stopped without issue. Traction control is another story of mis-automation. Try a gravel road/driveway on a moderate incline and it struggles.

Well, actually ABS decreases braking distance - on any surface other than on dry tarmac.

I remember following experiment, which involved braking in snow, with and without ABS, with and without winter tires.

ABS vs conventional, winter tires:
ABS<conventional

ABS vs conventional, summer tires:
Conventional<ABS

The latter is explained by the conventional wheel locking up, building a wedge of snow in front of the tires which increases friction.
The ABS however is confused, because then summer tires can't get any grip on the snow - and the ABS doesn't want to let them slip, as result the brake stays open...

Is it possible your camry had shitty tires?

[Azimech]

Who knows... it wasn't his Camry.

But anyway, the argument wasn't against ABS, which can be switched off (in the models I drive in, 1 circuit breaker) but the total absence of a hydraulic/mechanical linkage to the pereiopodical appendage (leg). Even a hydraulic system with a leak or a faulty brake vacuum pump will stop your car but if you are pushing the pedal linked to a rheostat while you've lost complete electrical power, maybe smashing your windscreen and blowing in the wind might help (choose your context).

[swiss]

Originally Posted by Azimech

Who knows... it wasn't his Camry.

But anyway, the argument wasn't against ABS, which can be switched off (in the models I drive in, 1 circuit breaker) but the total absence of a hydraulic/mechanical linkage to the pereiopodical appendage (leg). Even a hydraulic system with a leak or a faulty brake vacuum pump will stop your car but if you are pushing the pedal linked to a rheostat while you've lost complete electrical power, maybe smashing your windscreen and blowing in the wind might help (choose your context).

I'm your side here.
But they could design it like pneumatic truckbrakes where your need the air pressure(in our case epower) to keep the brakes open - if their system leaks air, the truck just brakes and stops.