by For nearly two years, NASA engineers were concerned that the Mars Odyssey orbiter’s fuel supply was running low. bringing a tragic end to the precious spacecraft. But it turns out they misjudged what’s left in the orbiter’s gas tank and that it’s good to last another two years, according to NASA.
The Mars Odyssey has been orbiting the Red Planet for more than two decades, covering a distance equivalent to 2.21 billion kilometers in space. When it launched in 2001, the orbiter had 500 pounds (225.3 kilograms) of hydrazine propellant to propel it through its orbital to travel around Mars. Which, however, Odyssey does not do have is a fuel gauge, making things difficult for mission controllers to determine exactly how much fuel the orbiter has left in his tank.
To monitor the orbiter’s fuel supply, the team behind the mission would warm up the spacecraft’s two propellant tanks and see how long it takes for them to reach a certain temperature. “Like a teapot, an almost empty fuel tank would heat up more quickly than a full one,” NASA wrote. It’s not perfect, but it still gave mission control a good estimate of how much gas was left in the tank, so to speak.
In the summer of 2021, fuel estimates seemed to indicate that Odyssey was running low with about 11 pounds (5 kilograms) of propellant remaining. Later in January 2022, the team’s calculations showed there was only 6 pounds (2.8 kilograms) of hydrazine left, according to NASA. That meant the mission would run out of fuel within a year, sooner than the team expected.
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Mission engineers were stunned; either the spacecraft was leaking fuel or their calculations just weren’t right. It took them months to figure it out before bringing in an outside consultant, Boris Yendler, who specializes in spacecraft estimation.
After studying the inner workings of Odyssey, Yendler discovered the cause behind the disappearing fuel. The orbiter uses heating elements to keep its parts from freezing in the depths of space, and one of the heating elements, connecting the fuel tanks, caused the propellant to heat up faster than expected. As a result, the team’s attempts to estimate how much fuel was left in Odyssey were thwarted because the propellant warmed faster than expected, leading them to believe there was less fuel in the orbiter’s tank.
“Our way of measuring was fine. The problem was that the fluid dynamics aboard the Odyssey are more complicated than we thought,” Jared Call of NASA’s Jet Propulsion Laboratory in Southern California said in the statement. I mean, that seems a little defensive, but okay.
The team behind the mission went back to the drawing board and calculated how much fuel was left in Odyssey, taking into account the extra heat. As it turns out, the orbiter is good to go until 2025. But that’s not to say it guaranteed, as the team is still working on refining the measurements.
“It’s kind of like our process for scientific discovery,” Call said. “You explore a technical system without knowing what you will find. And the longer you look, the more you discover that you did not expect.”
Odyssey is a critical member of NASA’s Martian fleet. Not only does the orbiter relay data between NASA’s ground control and its rovers on Mars, it has also aided in the discovery of minerals, ice deposits and possible landing sites on the Red Planet. Hopefully, the spacecraft still has some gas in the tank, continuing its 22-year legacy.
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