2017-01-28

TRIDENT-877 missile veered towards wrong continent; hemisphere

Apparently a test of an submarine launched trident missile went wrong, it started to head in the wrong direction and chose to abort its flight. The payload ended up in the Bahamas.

Aeronautics Museum

The whole concept of software engineering came out of a NATO conference in 1968.

The military were the first to hit this, because they were building the most complex systems: airplanes, ships, submarines, content-wide radar systems. And of course: missiles.

Missiles whose aim in life is to travel from a potentially mobile launch location to a preplanned destination, via a suborbital ballistic trajectory. It's inevitably a really complex problem: you've got a multistage rocket designed to be moved around in a submarine for decades, designed to be launched without much preparation at a target a few thousand miles away. Which must make the navigation a fun little problem.

We can all use GPS to work out where we are, even spacecraft which know to use the other solution to the GPS timing equation - the one which doesn't have a solution close to the geode, our model of the Earth's surface. Submarines can't use GPS while under water and they, like their deliverables, can't rely on the GPS constellation existing at the time of use. Which leaves what? Gyroscopic compasses, and inertial navigation systems: mindnumbingly complex bits of sensor trying to work out acceleration on different axes, use that, time, and its knowledge of its starting point to work out where it is. Then there's a little computer nearby using that information to control the rocket engines.

Once above enough of the atmosphere to see stars in daylight, the missiles switch to astronomy. This turns out to be an interesting area of ongoing work -IR CCDs can position vehicles at sea level when it's not cloudy (tip: always choose your war zones in desert climates). While the Trident missiles are unlikely to have been updated, a full submarine refresh is bound to have installed the shiny new stuff. And in an qualification test of a real launch -that's something you'd want to try. Though of course you would compare any celestial position data with the GPS feed.

Yet somehow it failed. Apparently this was a "telemetry problem", the missile concluded that something had gone wrong and chose to crash into the sea instead. I'm really curious about the details now, though we'll never get the specifics at a level to be that informative. First point: telemetry from the submarine to the missile? That is, something tracking the launch and providing (authenticated?) data to the missile which it could compare with its own measures? Or was it the other way around: missile data to submarine? As that would seem more likely -having the missile broadcast out an encrypted stream of all its engine data and sensor input would be exactly what you want to identify launch time problems. Perhaps it was some new submarine software which got confused, or got fed bad data somehow. If that was the case, then, if you could replicate the failure by feeding in the same telemetry, then yes, you could fix it and be confident that the specific failure was found and addressed. Except: you can't be confident that there weren't more problems from that telemetry, or other things to go wrong -problems which didn't show up as the missile had been aborted
Or it was in-missile; sensor data on the rockets misleading the navigation system. In which case: why use the term "telemetry".

We aren't ever going to know the details, which is a pity as it would be interesting to know. It's going to be kept a secret though, not just for the sake of whoever we consider our enemies to be —but because it would scare us all.

I don't see that you can say the system is production ready if there was any software problem. One with wiring up, maybe, or some other hardware problem where a replacement board -a well qualified board- could be swapped in. Maybe even an operations issue which can be addressed with changes in the runbook. But software? No.

How do you show it works then? Well, testing is the obvious tactic, except, clearly, we can't afford to. Which is a good argument in favour of cruise missiles over ICBMs: they cost less to test.

Tomahawk Cruise missile

Governments just don't take into account the software engineering and implementation details of modern systems into account, of which missiles are a special case, but things like the F-35 Joint Strike Fighter another. Some the software from that comes from BAe Systems a few miles away, and from what I gather, it's a tough project. The usual: over-ambitious goals and deadlines, conflicting customers, integration problems, suppliers blaming each other, etc, etc. Which is why the delivery and quality of the software is called out a a key source of delays, this in what is self-admittedly the world's largest defence programme.

It's not that the teams aren't competent —it's that the systems we are trying to build are beyond what we can currently do, despite that ~50+ years of Software Engineering.