There are only two human spacecraft in interstellar space. And their fuel is dwindling.
Voyager 1 — launched in 1977 and now over 15.6 billion miles from Earth — started out with 10 science instruments, but now has just three running after NASA turned off another gadget to conserve its finite nuclear fuel supply. And later this month, the space agency's engineers will turn off another instrument on its exploration sibling, Voyager 2.
"The Voyagers have been deep space rock stars since launch, and we want to keep it that way as long as possible," Suzanne Dodd, the Voyager project manager at NASA's Jet Propulsion Laboratory, said in a statement. "But electrical power is running low. If we don’t turn off an instrument on each Voyager now, they would probably have only a few more months of power before we would need to declare end of mission."
With such engineering vigilance and expert troubleshooting, it's possible the Voyager craft can stay online through the mid-2030s.
"You have to praise the engineers."
The recently turned-off instrument is the cosmic ray subsystem experiment, which studied cosmic ray particles — high-energy atomic particles speeding through the cosmos, created by events like supernova explosions. This instrument played a pivotal role in revealing when Voyager 1 had left our solar system's heliosphere (a bubble of protective particles emitted by the sun) and entered interstellar space in 2012.
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The remaining science instruments on Voyager are its magnetometer, plasma wave subsystem, and low-energy charged particle instrument, the last of which will be shut off in 2026. The plutonium fuel supply will gradually produce less power; the system has been losing four watts each year. A toaster uses 800 to 1500 watts, and, amazingly, each Voyager craft only generates around 249 watts.
Voyager 1's mission will end when it can't muster the energy to communicate with the gargantuan radio dishes of NASA's Deep Space Network, which are spread around the globe.
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The craft are now approaching 50 years of deep space exploration, surviving extreme bursts of radiation and swoops by icy planets. They are robust, trusty robots, but they couldn't survive alone. NASA engineers have for decades devised ways to keep the aging, radiation-pummeled craft alive, communicating with vintage computers aboard the nearly half-century old probes.
"You have to praise the engineers," Alan Cummings, a cosmic-ray physicist at Caltech — the research university that manages NASA's Jet Propulsion Laboratory — told Mashable last year.
