Designing, constructing and launching a spacecraft may be very costly. That is why NASA missions to Mars are designed to final so long as doable – just like the well-known Alternative rover, which was presupposed to final 90 days, however managed to final 15 years. The longer a mission can go on, the extra information it may gather and the extra we will be taught 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 ceaselessly, as it is going to ultimately run out of gas, so it is necessary to precisely decide how a lot gas is left, nevertheless it additionally proved tougher than NASA engineers anticipated.
Odyssey began with almost 500 kilos of hydrazine propellant, despite the fact that final 12 months the spacecraft gave the impression to be utilizing far much less gas than anticipated.
The problem lies in the truth that there isn’t a simple option to understand how a lot gas is left, so engineers use strategies corresponding to heating the tank and figuring out how lengthy it takes to achieve a temperature that exhibits 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 mistaken.
“First, we had to ensure the spacecraft was so as,” Joseph Hunt, Odyssey Challenge Supervisor at NASA’s Jet Propulsion Laboratory, stated in a press release. “After ruling out the potential for a leak or that we have been burning extra gas than estimated, we began our metering course of.”
After inspecting the programs, the staff 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 house, Odyssey makes use of heaters to maintain elements heat, together with gas tanks. However these heaters additionally heated the gas within the tanks, so when the staff ran their thermal measurements to estimate the remaining gas, there was much less gas inside than there truly was.
“Our measurement methodology was wonderful. The issue was that the hydrodynamics occurring aboard the Odyssey are extra advanced than we thought,” stated 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 12 months.
“It is a bit like our scientific discovery course of,” Name stated. “You discover an engineering system with out figuring out what one can find. And the longer you watch, the extra you uncover what you did not anticipate.”
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