Measurement madness

I recently made the mistake of buying a cheap new bicycle off eBay.

When it arrived, the box’s “this side up” arrow did not point up, an axle had pierced through its side, and the only protection found within was some paper to prevent scratching.

It was scratched anyway.

But undeterred by the scratches, dents, and buyer’s remorse, I set about putting my new bike together.

A task which didn’t seem like it’d be too much of a challenge at the time – just a few nuts and bolts to tighten, right?

Wrong.

The bike, having been made outside the U.S., was manufactured to metric standards – unsurprising since most other countries use the Metric System, but problematic here as we still rely on the Imperial System.

And evidently, metric hex sockets don’t get along with imperial Allen wrenches.

While the difference is just slightly off in their measurements, it’s enough to keep my bicycle in pieces while I write this article. A rather pathetic tragedy, I guess, but one that when expanded over a global scale, leaves more than enough room for actual catastrophes to happen.

Case in point: the infamous Mars Climate Orbiter incident of 1999.

When NASA launched its orbiter in December ’98 to embark on a $327.6 million mission, it’s unlikely that anyone expected a measly metric miscalculation to lead them to complete loss less than a year later.

But, according to Arthur Stephenson of the Mars Climate Orbiter Mission Failure Investigation Board, that’s exactly what happened.

“The root cause of the loss of the spacecraft was the failed translation of [imperial] units into metric units in a segment of ground-based, navigation-related mission software,” he said in a report.

Essentially, two separate mission teams were working with two different systems of measurement. Which is perfectly fine, until they have to share information with one another.

And apparently, when those two teams did go to share their information, they failed to convert the units they originally used, the investigation board found.

It’s a dilemma that anyone who has taken science classes may have encountered during exams.

If the conversion is done improperly in part A, then any attempts at doing parts B or C will be misguided since the information gathered to do so is wrong.

And screwing up on the test because of that is frustrating – I know from experience – but imagine how it must feel to do the same thing on a $327.6 million mission.

Probably not good.

Inevitably, the measurement error led to mission failure as the orbiter either drifted off into space or crashed somewhere it wasn’t supposed to on Mars.

An expensive mistake to say the least, but one that NASA didn’t blame on the different units involved – rather, NASA’s leadership blamed it on themselves.

“The problem here was not the error, it was the failure of NASA’s systems engineering, and the checks and balances in our processes to detect the error. That’s why we lost the spacecraft,” according to NASA’s Associate Administrator for Space Science at the time, Edward Weiler.

While it’s certainly true that NASA had failed to catch that error, is it really fair not to place any blame on the difference in measurement systems?

To put it bluntly, had only one system been used, then there would have never been any risk for such an error to have occurred in the first place.

And though NASA has improved its error detection methods since 1999, so long as the Metric and Imperial systems of measurement continue their attempt to co-exist here in the U.S., the risk of another error slipping through still remains – both for NASA and suckers who buy bikes off eBay.

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