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Sometimes a Typo Means You Need to Blow Up Your Own Spacecraft

Mariner I, a bit of missing mathematical notation, and why more doom by tiny mistakes is in our future.
July 26, 2014, 7:00am

This is the story of how a tiny mistake became a big mistake—and how, decades later, we continue to make a tiny mistake when talking about said tiny mistake.

On July 22, 1962, and about 300 seconds after the Mariner spacecraft lifted off on its mission to study Venus and win the next volley against Russia in the nascent space race, the craft began to spin wildly out of control. Back on the ground at NASA, a concerned engineer pressed a button and blew the $80 million Atlas rocket to smithereens over the Atlantic.

The decision to blow it up was simple: if he hadn't pressed that button, the ship might have crashed, possibly in the shipping lanes of the North Atlantic or in an inhabited place.

The explanation for the error, according to numerous accounts in the weeks and years that followed, was more complicated: a combination of system failures destabilized the spacecraft, and one of them appeared to originate with a "missing hyphen" or bad FORTRAN code somewhere in the software.

But a funny thing happened on the way to space history: FORTRAN wasn't being used for the rocket guidance system, and a missing hyphen wasn't really to blame.

The missing character was actually an overbar, or vinculum, a mathematical figure meant to indicate the mean of a set. When transcribing by hand the code for the guidance program, some unknown engineer at NASA had missed the overbar in "R-dot-bar sub n" or

\bar{\dot{R}_n}

which means "the nth smoothed value of the time derivative of a radius R." Without the smoothing function indicated by that overbar, the rocket's software interpreted normal minor variations of velocity as if they were serious. This caused mistaken corrections that sent the rocket off course and into oblivion.

Still, five days later, a front-page New York Times headline blared "For Want of Hyphen, Venus Rocket is Lost." Arthur C. Clarke would call it the "most expensive hyphen in history." The dropped hyphen would become central to the unfortunate story of Mariner for years to come, parroted even by officials at NASA and the Jet Propulsion Laboratory. The official NASA account says that Mariner was doomed by "a combination of two factors": a faulty beacon on board the Mariner caused the craft to lose the ground guidance signal, at which point the rocket's own computer kicked in—with that missing "hyphen."

During the periods the airborne beacon was inoperative the omission of the hyphen in the data-editing program caused the computer to incorrectly accept the sweep frequency of the ground receiver as it sought the vehicle beacon signal and combined this data with the tracking data sent to the remaining guidance computation. This caused the computer to swing automatically into a series of unnecessary course corrections with erroneous steering commands which finally threw the spacecraft off course.

Chalk up the long-running confusion over an inability by Congress, the media, and the public to comprehend complex math. This is, after all, rocket science.

But NASA was responsible for the confusion too: a year after John F. Kennedy had startled NASA with plans to go to the moon within the decade, officials were under pressure to quickly move on to the next Mariner mission, leaving little time for investigations or recriminations before the next launch, just over a month later. The official accounts—including mentions of a missing hyphen—were the results of an investigation that was conducted in less than a week.

The confusion over the "hyphen" bore echoes of Mariner's doomed voyage: stupid mistakes are easily made even by the smartest people. And even the tiniest ones can be catastrophic.

Mariner was meant to be a bold sign of the four-year-old space agency's ability. But its engineers were on a very tight schedule, with a narrow launch window of just 45 days.

The Mariner I incident wouldn't be the last time NASA lost a mission due to a simple mistake. Priceonomics reports that:

In 1999, the $125 million ($172 million in 2014 dollars) Mars Climate Orbiter flew off course and disintegrated after spacecraft engineers forgot to convert from English to metric measurements. While Jet Propulsion Laboratory's navigation team used the metric system (millimeters and meters) in its calculations, Lockheed Martin Astronautics, which built the craft, provided measurements in inches, feet, and pounds.

For other people who regularly deal with hyphens, like us writer-reporters, or writer-editors, or editors-at-large (do hyphens belong there?), we are often luckier. We have spell check, and autocorrect, and editing after the fact (though this is generally frowned upon). But we aren't always lucky: this very article was nearly downed by a dumb mistake: while writing this, my computer nearly crashed and I hadn't saved my work, despite the fact that I've lost plenty of work this way before. The spinning ball eventually stopped though. Praise be to the gods of blogging.

Kennedy with NASA officials and a model of Mariner 2. Photo: National Archives

But in these little mistakes is another lesson: the more complex and ambitious our endeavors get, the harder it becomes to predict all eventualities and all the tiny, giant mistakes we might make.

Such eventualities would destroy two other Mariners too: Mariner 3 was disabled by a malfunction and Mariner 5 was hit by micrometeroites. It "joined its sibling, Mariner 3," the space historian Rod Pyle wrote, "dead … in a large orbit around the sun."

See also

Space Shuttle Parking Lot: Tailgating the Rocket Launch 

How Challenger Exploded, and Other Lessons in the Catastrophes We Make