Re: [twuug] Space Shuttle Columbia blows up on reentry!

[Charles Shannon Hendrix <shannon@xxxxxxxxxxxxx>]

On Sun, Feb 02, 2003 at 05:27:22PM -0500, Anthony VanCampen wrote:

>     I got a call from my sister in-law, who wanted to know if it was
> possible to reprogram the flight control computers on the shuttle.  My
> recollection is that there are three independent computers running the same
> program and that they are dedicated to the flight management tasks.  I old
> her that anything was possible, but that I didn't think that it was likely
>     Does any one know what OS the flight comp(s) use?  My guess is that it
> is an embeded OS with a very limited set of functions?

You are in for a serious shock.

They are descended from the IBM 360 mainframe, modified and miniaturized
for use on the shuttle.  A similar design was used on some airliners and
other aerospace applications.  It's called the IBM AP-101.  The previous
version was the AP-1, and was used in the F-15.

They are basically just black boxes with a cable coming out for power
and data.  They have no hard drives, and get their software from tape
storage.  You have to remember that the shuttle was designed in the 1970s.

It's not as bad as it sounds.  The mainframe design means the computers
have very good I/O power and reliability.  They are also hardened against
temperature, g-force, and a great many other hazards.

Despite the low CPU speed, they have realtime and I/O abilities even
your latest Athlon gaming system does not have.

The software is running on a custom OS, and is written in HAL/S and
assembly language.  It's very, very reliable and all coding is done in a
formal code, evaluation, and testing process.  

In the 80s they had to have a seperate program for each type of weather
expected during launch and reentry.  They could only alter parameters.
So if it was hot and then started raining, they had to reload the
software.  That's been changed now.

Basically there is no need to change the computers.  They work fine,
the software is very mature and flexible now, and there really is no
match for the hardware available elsewhere.  Despite its age the shuttle
system is the most sophsticated fly-by-wire control system in the world.

Pretty damned cool for a project done in the 70s, eh?

-- 
UNIX/Perl/C/Pizza____________________s h a n n o n@wido !SPAM maker.com


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