The Mars Metric Mix-Up

###The Mars Metric Mix-Up

Mars Orbit, September 1999 — A $327 million spacecraft vanished forever because two teams of brilliant engineers forgot to check their math units.

In December 1998, NASA launched the $327.6 million Mars Climate Orbiter. Built by Lockheed Martin in Colorado and guided by NASA’s Jet Propulsion Laboratory, the robotic probe sailed flawlessly across space for nine and a half months to study the Martian atmosphere.

But the two engineering teams had a major communication breakdown. Lockheed Martin’s software calculated the spacecraft's thruster power in imperial units—pounds. NASA’s navigation computers expected those exact same numbers to be in metric units—newtons.

On September 23, 1999, the orbiter began its final maneuver. Because of the mixed-up math, it dropped to a lethal 57-kilometer altitude instead of a safe 226 kilometers. The probe vanished behind Mars 49 seconds early, burning up in the atmosphere.

How It Went Down
Probe launchestoward MarsDec 1998Drifting isdismissedDuring journeyFinal maneuverbeginsSept 23, 1999Probe dropstoo low57 km altitudeSpacecraft isdestroyed49 seconds early
Crazy-o-Meter
Hard to believe
No.16
A split-screen cartoon scene of two wildly mismatched engineering desks. On the left side, a confident engineer happily measures a massive iron anvil using an old-fashioned, heavy-duty spring scale. On the right side, another engineer proudly measures a glowing, futuristic glass cube using a high-tech laser measuring tool. In the space between them, hovering right above a red, cratered planet, a highly advanced satellite is spectacularly bursting into cartoon flames as it scrapes the atmosphere, while the two engineers give each other thumbs-up, completely oblivious.

The Mars Metric Mix-Up — Mars Orbit, September 1999