Weighing 2.9 tons... this heap of old batteries is now the heaviest single piece of garbage to be jettisoned from the International Space Station.
Digital Trends' What was inside the space station pallet jettisoned into space on Thursday says:
On Thursday, March 11, mission controllers in Houston commanded the space station’s Canadarm2 robotic arm to jettison an external pallet containing old nickel-hydrogen batteries into Earth orbit.
The nickel-hydrogen batteries were once used for the ISS’s power system but have since been replaced with newer lithium-ion batteries featuring improved power capacity, smaller size, and lighter mass.
Fortunately, the pallet and the batteries inside it won’t remain as space junk indefinitely (there’s enough of that already orbiting our planet), as the whole lot will burn up when it enters Earth’s atmosphere in several years’ time.
I suppose that it's fortunate for other spacecraft in LEO that they won't stay in orbit for even longer than "several years' time" but without taking any measures to increase drag like attaching some Terminator Tape or equivalent it's still a non-zero risk.
But for those who breathe all that nickel doesn't just go away, it becomes a long term resident of Earth's atmosphere.
Scientific American's Some airborne particles pose more dangers than others; New evidence suggests that breathing nickel and other metals can lead to lung and heart damage, and even death is from 2009, and the science of the effects of PM2.5 and smaller particles on human heath is rapidly evolving.
- Considering all of the Nickel Hydrogen that were ever on the ISS that have now all been replaced, what fraction were incinerated in the atmosphere we breathe, and how many total kilograms of nickel does this represent?
- Were there any estimates as to what fraction would end up as nickel-containing PM2.5 particles? (the size at which particles tend to remain in our lungs and can sometimes move into the bloodstream and lodge in different organs)