Mystery of Orbiter Crash Solved from the Washington Post
<font size=“1”>Friday, October 1,1999</font>
NASA’s Mars Climate Orbiter was lost in space last week because engineers failed to make a simple conversion from English units to metric, an embarrassing lapse that sent the $125 million craft fatally close to the Martian surface, investigators said yesterday.
I remember college physics classes when the professors would always try to trick the students by combining metric and english values in the same problem. They would do this repeatedly to drive home the dangers of using inconsistent units. It became kind of a mantra to check and resolve unit systems before even attempting to solve the problem.
Apparently these clowns didn’t have the same instructors.
One complete set of morals for sale to highest bidder, new in box.
What, that base-10, count-on-your-fingers metric system is better than our binary-based, computer-compatible, customary system?
This is 1999; get with the (computer) program.
“Kings die, and leave their crowns to their sons. Shmuel HaKatan took all the treasures in the world, and went away.”
Hey, the mile-thing isn’t even yours to begin with. It’s the Brits’. And why would a mile be more “compatible” (whatever that is !) to a computer than a kilometre (or is it kilometer) ?
At least a kilometre is 1000 metres. And a meter is 100 centimetres. And a kilogram is (duh) 1000 grams.
Even though I’m sure I could get used to ANY system (example: how long does it take to get used to a foreign currency when on holiday ? answer: maybe 3 weeks, after that it’s automatic), metric sure is more logical. But then, miles ‘n’ stuff are probably more romantic
Unofficially, a lot of ‘old’ measurements are in use in The Netherlands still. Mostly for weight and nautical stuff. But it’s not like they’re gonna arrest you for being unmetric
Disclaimer: I am a citizen of the United States who believes that we should have converted to the metric system a long time ago. I was one of the kids who was in elementary school when they tried switching, and it seemed like unfinished business when the program just went away.
That having been said, you are entirely wrong in your assessment that failure to use the metric system led to the crash of Mars Climate Explorer. The findings clearly state that it was the use of both metric and avoirdupois measurements, and the failure to account for differences in those values, that led to fatal miscalculations in the orbit insertion path.
Yes, if NASA had used only metric calculations the error would not have occurred. The same is true if they had used only English measurements. Get over it.
A couple of years ago, one of our equipment suppliers made the EXACT SAME mistake on a finite element stress analysis. It was for a part already in service, that had deflected (permanent deformation) about 0.25".
Well, they did a finite element stress analysis that showed tiny stresses and deflections (hundredths of an inch). They didn’t give enough information for me to check their work adequately, but this was clearly wrong. After going around in circles with them a few times, they finally figured out that the part had been dimensioned (in Germany) in millimeters, but the analyst (a consultant in the US) had assumed that it was dimensioned in inches. WTH, it’s only a factor of 25!
They always taught me to check units, too, and I’m religious about it, but I guess some people slept through that class.
(For you non-mechanical engineers out there, an FEA is a kind of computer analysis that estimates stresses in a loaded part.)
On a related note, we were in Puerto Rico recently, and we discovered that the speed limit is posted in miles per hour, while distances are posted in kilometers, and gas is sold by the liter.
NASA does use only metric units, except when dealing with the Moronic Public, wherein they convert for our benefit, since we are idiots. But Lockmart, the builder of the spacecraft and a large aircraft manufacturer, apparently provided the engine thrust in pounds force, as jet engines customarily are, rather than newtons; hence the problem. At least according to the news media, and you know how accurate they are!
What seems awfully odd to me isn’t that a units problem happened (they happen even when you stick with one system of units), it’s that it was not caught in a review process long before the “oh, shit!” point. NASA has a better track record than anybody else for getting to Mars (or Jupiter, or Saturn, or…), but this was one awfully embarassing failure, IMHO.
Anyway, this wasn’t a very expensive fuck-up, as interplanetary fuck-ups go - this was on the order of $125 million, compared to in the billions for some of the old-style big-budget missions.
A very similar thing happened in Canada when we converted to Metric. To help get the metric program established, the government forced Air Canada to convert to metric. In the middle of this conversion, a Boeing 767 was incorrectly fueled, and wound up losing all its engines over Manitoba. The pilot managed to glide the jet something like 80 miles to an abandoned runway at Gimli Manitoba and land without any injuries.
Perhaps we’re fortunate this occured with the the Mars Orbiter, and not the Cassinni (sp?) probe, which had plutonium on board for fuel, and recently did a flyby of Earth. The million-to-one odds of it crashing into Earth probably didn’t take int account the chance of a units mismatch.
It is fortunate, but mostly because Cassini is a much more expensive probe than the Mars Climate Orbiter! And also because we launch far fewer probes to Saturn than we do to Mars, and it takes longer to get there.
RTG’s (with plutonium) have reentered before; they’re designed for this. Usually they’re dusted off and re-used; they’re quite hardy.
Also, it would be much easier to notice the error near earth, and even an error of several times the size of the MCO one wouldn’t have made Cassini hit earth.
