Space missions dodged disaster: A tiny problem can have huge consequences for a space mission. Sometimes a huge endeavor hinges on the smallest detail three seconds’ worth of fuel, an engineer’s stubbornness, a speck of paint, or a 1.3-millimeter calibration. When surprise glitches revealed themselves after launch, it took massive efforts to save the missions that gave us a closer look at Mercury, a tour of the outer solar system, our only glimpse of Titan’s surface, and an incredible view of the early universe.
Mariner 10 Was Determined to Fail
Mariner 10 pretty much spent its whole mission trying to fail in increasingly creative ways, and its mission team back on Earth had to work constantly to keep the spacecraft on track. About a month after launch, for no apparent reason, Mariner 10 irreversibly switched itself from main power to backup power, leaving the mission with no backup if the power system failed. Just in case that wasn’t stressful enough for the folks back home, one of the spacecraft’s computers developed a habit of resetting itself during preparations for roll maneuvers, which reset the onboard computer’s clock to zero. Mariner 10’s clock needed to be in sync with the one at Mission Control so mission planners could send the spacecraft commands from Earth; every time the clock reset, the mission team had to reset their clocks and completely re-plan the sequence of commands — which meant rewriting and checking several pages of code.Voyager 1 Almost Ran Out of Gas
Voyager 1, the mission that paved the way for Galileo and Cassini, almost didn’t make it out of Earth orbit. As Mission Control counted down the seconds until launch, a nasty surprise waited in the Titan second stage’s fuel system: a leak, small enough to have been missed in pre-launch inspections, but big enough to potentially doom the mission. By the time the team on the ground discovered the problem, Voyager 1 was already on its way to space, with the Titan rocket’s second stage short about 1200 pounds of propellant. That meant the spacecraft might not make it into a high enough orbit around Earth for the maneuver that would break it away from Earth’s gravity and set it on a course for Jupiter. It looked like Voyager 1, instead of exploring the outer Solar System, might never leave Earth orbit — the space faring equivalent of running out of gas before you’ve left the driveway.Huygens Would Have Disappeared on Titan
The Huygens lander would have been a titanic failure if one engineer hadn’t insisted on doing an extra radio test at the last minute. The Huygens lander didn’t have enough power to send its data back to Earth itself, so it was programmed to transmit its data from Titan’s surface to Cassini, in orbit around Saturn. Cassini would then relay the lander’s messages to the massive satellite dishes of the Deep Space Network on Earth. The whole lander mission depended on that one radio link between the two spacecraft — but when ESA radio engineer Boris Smeds ran a quick test of the link on Cassini’s last Earth flyby (after the first leg of its gravity assist trajectory, which carried it on two swings past Venus before slingshotting outward in an accelerating arc toward Jupiter) — that vital link failed.
“Almost every mission has some design problem,” Smeds said in a 2005 ESA interview. When engineers and scientists are lucky, that design problem shows up before launch, where it can be diagnosed and fixed on the ground. But luck isn’t always on the side of science; then it takes hard work, quick thinking, and a lot of good luck to save a mission from disaster.
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