March 22, 2023

Designing, constructing and launching a spacecraft may be very costly. That is why NASA missions to Mars are designed to final so long as attainable – just like the well-known Alternative rover, which was purported to final 90 days, however managed to final 15 years. The longer a mission can go on, the extra information it could actually gather and the extra we are able to study from it.

That is true each for orbiters that journey round Mars and for rovers that discover its floor, such because the Mars Odyssey spacecraft, which was launched in 2001 and has been in orbit round Mars for greater than 20 years. However an orbiter cannot go perpetually, as it would ultimately run out of gas, so it is necessary to precisely decide how a lot gas is left, however it additionally proved tougher than NASA engineers anticipated.

This illustration reveals the 2001 NASA Mars Odyssey orbiter. The mission crew spent most of 2021 assessing how a lot propellant was left on the orbiter and concluded there was sufficient to maintain it lively till not less than 2025. NASA/JPL-Caltech

Odyssey began with practically 500 kilos of hydrazine propellant, regardless that final yr the spacecraft gave the impression to be utilizing far much less gas than anticipated.

The issue lies in the truth that there isn’t a straightforward solution to know the way a lot gas is left, so engineers use strategies similar to heating the tank and figuring out how lengthy it takes to succeed in a temperature that reveals how a lot mass is inside. This methodology was used to calculate the small quantity of gas left, so both the spacecraft was leaking or the measurement was fallacious.

“First, we had to verify the spacecraft was so as,” Joseph Hunt, Odyssey Venture Supervisor at NASA’s Jet Propulsion Laboratory, mentioned in an announcement. “After ruling out the potential for a leak or that we had been burning extra gas than estimated, we began our metering course of.”

After analyzing the methods, the crew discovered that the issue was how the spacecraft heated up and cooled down. As a result of electronics must be stored heat to work correctly in chilly area, Odyssey makes use of heaters to maintain components heat, together with gas tanks. However these heaters additionally heated the gas within the tanks, so when the crew ran their thermal measurements to estimate the remaining gas, there was much less gas inside than there truly was.

“Our measurement methodology was effective. The issue was that the hydrodynamics occurring aboard the Odyssey are extra complicated than we thought,” mentioned Jared Name, Odyssey mission chief.

The excellent news is that with warmth, the Odyssey has not less than 9 kilos of gas left, which ought to final till not less than the tip of 2025. anniversary of the yr.

“It is a bit like our scientific discovery course of,” Name mentioned. “You discover an engineering system with out realizing what you’ll find. And the longer you watch, the extra you uncover what you did not anticipate.”

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