On November 18th, 2008, Heide Stefanyshyn-Piper looked out into the blue of the ocean from 250 miles away. Above it. She kicked off for her third EVA for mission STS-126. She was out there with fellow astronaut Stephen Bowen to fix the rotation assembly that allows the solar arrays to follow the sun. It had failed and was not operating optimally. The solution that the those ground control folks came up with? Go out there with some grease and some wipes to clean it up and grease it up. No sweat.
Looking into her airlock bag with these advanced tools she sees something very concerning. “I think we had a grease gun explode in the large bag. There’s grease in the bag.”
She heard Steve Bown observe dryly over her headset, “Ah. it must have been the pressure changes.” Putting that MIT engineering degree to work.
The flight controllers peered through her helmet camera uplink and calmly assessed the situation, with suggestions. She grabbed a dry wipe and did her best to clean up the grease. The EVA suit’s not known for being dextrous, though, and one movement too exxagerated knocked the bag. It tumbled away, off on its own. Out of reach.
“Oh, great. We have a lost tool, uh, I guess one of my crew lock bags was not transferred and it’s loose.”
This is how one more piece of space debris ended up in orbit. There are more than 23,000 pieces of debris larger than 10cm in orbit. This number grows every day. Even something as small as Heide’s tool bag can be identified and seen from the ground.
Space debris becomes more and more of a concern as we look outwards from our own planet. This is a problem known as Kessler syndrom. The thought is that a time could come where there’s such a density of space debris that we avoiding collision would be impossible. Even in the early 2000s we found evidence of small debris embedding itself in shuttle windows.
An impact with a piece of space debris is on average a collision with the relative difference in velocity of 10-15km/s. This is 10x the speed of even the fastest bullets. At that speed, even a bolt no bigger than your thumb will tear through steel like paper.
There’s many projects to track and visualize space debris, but what do we do to make this better?
One approach is to stop putting things in higher orbits. Low earth orbit has a small amount of atmosphere which causes drag on items. This means that, without assistance, items in low earth orbit will leave orbit and return to earth. This is great because it puts a much shorter time limit on debris: years instead of millenia. This is why Starlink is considered less of a negative impact on space debris.
However, that still leaves thousands of tons of space junk in higher orbit. Some of these will take many, many lifetimes before they would deorbit on their own - perhaps longer. Actively removing these takes ingenuity. Science fiction has looked into this active removal via movies and comics.
In reality, it’s more likely that we’ll use ground-based or sattelite-based Laser Brooms to control and deorbit smaller debris (1cm-10cm in size). This works by targeting a piece of debris and firing a high-power laser to heat one side of the debris to produce thrust. This would make the orbit unstable, quickening the eventual deorbit.
Oh, and Heide’s toolbag. It was in a low orbit on its own around Earth until it lost enough velocity to return on August 3, 2009. It was vaporized during reentry.