The team agreed that they needed some fresh eyes to assess the situation. They brought in Boris Yendler, an outside consultant who also specializes in spacecraft propellant estimation.
Like all spacecraft, Odyssey relies on heaters to keep various parts, including the fuel tanks, working in the cold of space. Yendler wondered whether heat was being added to the propellant from some other source on the spacecraft, complicating the fuel measurement. After lots of experimentation, the team confirmed that was the case: Heaters along a fuel line connecting the tanks were warming them faster than expected, making it seem as if the tanks were nearly empty.
“Our method of measurement was fine. The problem was that the fluid dynamics occurring on board Odyssey are more complicated than we thought,” Call said.
After figuring out how much heat wasn’t being accounted for in their calculations, the team concluded that Odyssey has about 9 pounds (4 kilograms) of hydrazine left. It’s enough to last the mission for a few more years. Although the number could change as the team works to refine the measurements and improve their accuracy, the team is resting easier now that they better understand their spacecraft.
“It’s a little like our process for scientific discovery,” Call said. “You explore an engineering system not knowing what you’ll find. And the longer you look, the more you find that you didn’t expect.”
