Archives For Systems of Systems

Strowger pre-selection

The NBN, an example of degraded societal resilience?

Back in the day the old Strowger telephone exchanges were incredibly tough electro-mechanical beasts, and great fun to play with as well. As an example of their toughness there’s the tale of how during the Chilean ‘big one’ a Strowger unit was buried in the rubble of it’s exchange building but kept happily clunking away for a couple of days until the battery wore down. Early Australian exchanges were Strowger’s, my father actually worked on them, and to power their DC lines they used to run huge battery pairs that alternated between service and charging. That built in brute strength redundancy also minimised the effect of unreliable mains power on network services, remember back in the day power wasn’t that reliable. Fast forward to 1989 when we had the Newcastle (NSW) earthquake and lo our local exchange only stayed up for a couple of hours until it’s batteries died.

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Boeing 787-8 N787BA cockpit (Image source: Alex Beltyukov CC BY-SA 3.0)

The Dreamliner and the Network

Big complicated technologies are rarely (perhaps never) developed by one organisation. Instead they’re a patchwork quilt of individual systems which are developed by domain experts, with the whole being stitched together by a single authority/agency. This practice is nothing new, it’s been around since the earliest days of the cybernetic era, it’s a classic tool that organisations and engineers use to deal with industrial scale design tasks (1). But what is different is that we no longer design systems, and systems of systems, as loose federations of entities. We now think of and design our systems as networks, and thus our system of systems have become a ‘network of networks’ that exhibit much greater degrees of interdependence.

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MH370 Satellite Image (Image source: AMSA)

While once again the media has whipped itself into a frenzy of anticipation over the objects sighted in the southern Indian ocean we should all be realistic about the likelihood of finding wreckage from MH370.

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The MIL-STD-882 lexicon of hazard analyses includes the System Hazard Analysis (analysis) which according to the standard is intended to:

“…examines the interfaces between subsystems. In so doing, it must integrate the outputs of the SSHA. It should identify safety problem areas of the total system design including safety critical human errors, and assess total system risk. Emphasis is placed on examining the interactions of the subsystems.”

MIL-STD-882C

This sounds reasonable in theory and I’ve certainly seen a number toy examples touted in various text books on what it should look like. But, to be honest, I’ve never really been convinced by such examples, hence this post.

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The Mississippi River’s Old River Control Structure, a National Single Point of Failure?

Given the recent events in Fukushima and our subsequent western cultural obsession with the radiological consequences, perhaps it’s appropriate to reflect on other non-nuclear vulnerabilities. A case in point is the Old River Control Structure erected by those busy chaps the US Army Corp of Engineers to control the path of the Mississippi to the sea. Well as it turns out trapping the Mississippi wasn’t really such a good idea…

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Just discovered a paper I co-authored for the 2006 AIAA Reno Conference on the Risk & Safety Aspects of Systems of Systems. A little disjointed but does cover some interesting problem areas for systems of systems.

A UAV and COMAIR near miss over Kabul illustrates the problem of emergent hazards when we integrate systems or operate existing systems in operational contexts not considered by their designers.

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