Going Metric on the Moon

It was announced last month at the 2nd Exploration Conference in Houston that we are going to use metric units on the Moon. This was a big announcement, a decision that was not made easily or lightly, one that will have far reaching ramifications.

Surprised? If you are a scientist, you are probably shocked to hear that NASA is not already using SI units. If you are an engineer, you're probably not at all surprised. And if you are neither, you probably don't think much about units unless you're in Europe and trying to figure out what outfit to wear if the daily high is 23 degrees C.

The Omnibus Trade and Competitiveness Act of 1988 actually requires (with certain exceptions) all Federal Agencies to use the metric system in their procurement, grants and other business-related activities by the end of 1992 (that's 15 years ago!), and yet NASA is still measuring things in feet and inches much of the time. This act, which ammended the Metric Conversion Act of 1975, was yet another attempt by the Federal government to coax America towards Metrication by leading by example. Unfortunately, it turns out that NASA and it's contractors are just as resistant to change as the rest of the American people.

What is wrong with us? We all know the metric system is better. As a scientist, I use the SI units all the time and yet, if someone asks how tall I am - I'm 5'4", if you want that in meters, I need to get out a calculator. I remember the big push towards metric when I was a kid; my brother and I even had this great board game (Metricat10n) that taught us all the SI prefixes. But it all kinda fizzled out didn't it?

For NASA, one of the issues is the mixing of the two systems. Some things are done in metric, some are still in English units. That can lead to serious problems like the highly publicized and embarrassing loss of the Mars Climate Orbiter in 1998 where NASA and most of the contractors worked in metric units but one contractor, Lockheed Martin, provided data in pound force seconds instead of newton seconds. Oops.

I was not party to the discussions leading up to last month's big decision about the Moon, but the rumors I heard suggested that several of NASA major contractors were strongly against metric. Switching is too expensive. Period. If forced, they would do it, but they would only make changes "on the back end" - i.e. they would do everything in English units and then add a line of code at the end that would convert the values into SI. Extra lines of code, of course, add extra risk, something NASA really hates.

I'm very happy that NASA has decided to stick to their guns on this one. I hope the changes are not just cosmetic, I hope they really push the contractors to do more than add code. The transistion may be difficult, but it will be worth it in the long run, it will ultimately be safer, and more efficient, for us, and for our international partners (if we're serious about having them), and for the poor astronaut who only has to carry one set of wrenches when he heads out the airlock to fix that stupid solar panel again.