Re: Writing better software was: Design by Contract (was Re: Interesting thread in comp.lang.eiffel)

[John Magness <jmagness@swbell.net>]

I read the document at the link.  There are many things it does not mention.
In 1992 I took an Ada language course from an adjunct professor who was an
IBM employee.
He was a member of the shuttle flight software development team.  He told
the class that NASA had asked IBM to determine the cost of the delivered
code. The result of the study was $5000.00 per line of delivered code.
That's late '80's dollars I think.

    I can not speak to the current practice, but prior to 1990, the flight
software was tested in a systems integration laboratory, then was
transferred to the Shuttle Mission Simulation for further testing & crew
training.  The SMS consisted of two crew trainers, each of which had a full
set of flight computers.  The flight software would have patches added due
to the training requirements i.e. Being able to start training at any point
in a mission time line, etc.  By the completion of mission training, the
flight software had been executed thousands of times, with nominal & off
nominal conditions.  The simulation had several thousand  malfunctions that
the instructors could insert into a training session. Traditionally, the
crew would be trained repeatedly for all crucial phases of a mission:
Takeoff, deorbit & landing, emergency landings,
on orbit maneuvers, payload deployment, etc.  At the end of the training
cycle, the crew would fly a complete mission timeline, takeoff to landing.
Generally, the crew were permitted to return to their homes during the
scheduled sleep cycle.

    During the '80's several flight software errors were found, but I can
not give an actual count.  Mind, that at times the simulators run integrated
with MCC, Cape Canaveral, White Sands, & Redstone. Simultaneously.

    The delivered cost for the flight simulators was over $100 M. In late
1970's dollars.
The flight software development cycle then & now has what could be
considered extensive acceptance testing  prior to actual use.

    By the way, I believe that during one of the Gemini missions the flight
software was patched on orbit.

Simon Brady wrote:

> Kent Paul Dolan wrote:
> >
> > The case study in the above book of necessity only follows the project
> > studied up to the book's publication date.  Later breaking news is the
> > delivery of a suite of software for space shuttle control with one bug
> > detected ever in the delivered product.  Not "one bug per KLOC",
> > _one_bug_.
>
> A good article on the Shuttle development process and culture is:
>
>    http://www.fastcompany.com/online/06/writestuff.html
>
> Simon Brady                                            sjbrady
> Research Assistant, Computer Science Dept.               at
> University of Otago, Dunedin, New Zealand            acm dot org