Re: Will Boeing Use Ada To Build $9 Bln Network For Teledesic?

["Nick Roberts" <Nick.Roberts@dial.pipex.com>]

Dale Pontius <pontius@btv.vnet.ibm.com> wrote in article
<5kcmkd$f3q$1@mdnews.btv.ibm.com>...
[...]
> Is it possible to use a hard drive on a small satellite, or will
> the rotating platters foul things up. I'd expect that the shuttle
> is so big that the effect is insignificant.

A single hard disk drive on a satellite would tend to cause the satellite
to rotate significantly, unless it was spun up once and never spun down
during operation. Two identical drives mounted back-to-back would solve
this problem. However, they would have to be rigged so that if one failed
and spun down, the other would be spun down also.

Conventional hard disk drives would be unsuitable for a satellite, because
they are not sufficiently immune to the vibrations caused during the launch
into orbit. They would also be prone to failure in space, if kept
continuously spun up. Hardened versions exist, but are expensive. I suspect
that FLASH RAM (or similar) would pose a better solution.

The software controlling the satellite's ability to contact its base
control station would have to be highly reliable. Ada would be less
suitable than an 'artificial intelligence' language, such as Prolog, LISP,
or other, for this section of the software, since it would be best to endow
the software with some rudimentary 'intelligence', so it could use
rules-based induction to solve certain problems for itself.

The remainder of the software would not necessarily have to be very
reliable (depending on what sort of communications it was being used for).
I would suggest that the reuse of existing software (such as all that
TCP/IP and related stuff) would be very important (most of which is written
in 'legacy' languages).

But, for some of the software, Ada is likely to be a good choice.

Nick.