> Some, but definitely not all. Many places a small fix-up may not need a 
> day's worth of meetings, but with the shuttle, not a single line of code 
> can be changed.

The same happens for code for cars, but IIRC only after the first version 
has been released and tested during development.  After that point there is 
a huge amount of resource put onto testing and evaluation, and after it has 
been "qualified", no changes are allowed without a big meeting and 
discussion for even tiny changes.

> Ah, I figured the avionics linkages would be hydraulic, not computer 
> controlled.

No, too risky to have lots of hydraulic lines going all round the plane, 
also harder to detect when they've (partially) failed and automatically 
switch to a backup system etc.

It's funny, because a lot of the time people regard electronics as much more 
unreliable than mechanical systems.  It's just the failure mechanisms are 
different, but certainly electronics can be made just as reliable as 
mechanical systems, and even more reliable if necessary.  Take for example 
when cars changed from a mechanical distributor to an electronic system ... 
no more getting out the WD40 to dry it out after heavy rain!

>> about to switch it on, and then as he flicked the switch, the mass moved 
>> extremely quickly to point B, past point B, kept accelerating and smashed 
>> off the end of the demo. Everybody laughed.
>
> Heh. Ouch...

Yeh IIRC, his comment was something like "ok, well that didn't seem to work 
then", at which point someone shouted out "no s4!t" :-)

The other system they seemed to be very fond of was the inverted pendulum 
controller.  The pivot of the pendulum can be moved left and right by a 
motor/pulley system, and the idea is to keep the pendulum's tip upright. 
After a hideous amount of maths you finally get to implement it on a real 
system and watch how some people's go totally ape and smash against the end, 
while most people got theirs working eventually.  In the end it is really 
cool to be able to add weights and stuff to the top and wobble it, all the 
while the motor is making tiny adjustments to stop it falling over.

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