What happens if an astronaut loses a tool during a spacewalk?
Last Updated: March 27, 2024
We all can have a case of the butterfingers, but what happens if an astronaut drops something, say a tool, on a spacewalk? Since the ISS is in orbit around Earth, would it fall to Earth and potentially hit someone? Would it go flying out into space, potentially hitting something else? Would it hover in place?
Let’s explore the different scenarios, options for astronauts, and the procedures in place for this situation.
Introduction/ Background
Living and working on the space station provides some unique challenges and considerations for this scenario. First and foremost, everything that is on the space station is there because we sent it there. There is no quick trip to the store to stock up on supplies. Restocking supplies requires a launch from Earth and those are not easy to reschedule, even if it is an emergency.
In addition, the ISS orbits Earth in freefall at an average altitude of 250 miles (400 km) at 17,150 miles per hour (27,600 km per hour) which means that it is affected by a very different set of physics than when we drop something here on Earth.
Finally, the ISS is not the only thing either human-made or natural orbiting the Earth. These have to also be considered when we consider something being dropped during a space walk.
What would happen?
Considering all of these factors there are essentially three scenarios that could occur during a drop scenario.
Continue orbiting Earth in some fashion:
Since the ISS is in the microgravity of space (not as in deep space, but still less than Earth) and the ISS is in freefall around the planet, it wouldn’t just drop like an object from the Empire State Building. Due to the microgravity of space, the tool will likely stay in the same orbit as the ISS at least for some time and then move into either a higher or lower orbit depending on a variety of different factors.
Even if it was thrown toward Earth (the astronaut in question would likely have other questions to answer if this was the case), adding an extra couple dozen miles per hour won’t change it much compared to the 17,000 mph it’s currently orbiting around the Earth. The orbit will shift, but it would likely settle into the ISS’s orbit or something similar at least for a bit.
Deorbit into Earth:
Even the ISS makes adjustments to keep it in a stable orbit around Earth. Without those adjustments, the tool would begin to deorbit as it is still affected by Earth’s gravity. Depending on a variety of factors including the size of the object, the speed of the object when it was released, and the direction it was traveling, this deorbit may take months or years. As it gets closer to Earth, it will speed up and then burn up in Earth’s atmosphere upon re-entry.
That being said, the re-entry of space debris into Earth’s atmosphere can be a prolonged process, exemplified by the Exposed Pallet 9 (EP9), a nearly 3-ton structure laden with old batteries. Initially jettisoned in 2021 from the ISS, EP9’s re-entry took nearly three years!
The highest chance of “hitting” Earth (eventually):
If the tool was thrown directly backward compared to the station’s movement, there is the highest likelihood of it deorbiting slowly into a collision course with Earth. But even in that case, it would likely burn up in the atmosphere.
The most likely scenario:
All in all, the most likely effect of a dropped object, such as a tool, is that it would continue orbiting the Earth for a period of time (ranging from days to years), though these orbits would likely change over time, before eventually deorbiting enough to burn up in Earth’s atmosphere.
The concerns:
While it is good that a dropped object in space won’t be careening toward you here on Earth, it causes concern in mainly two other areas.
First is simply the fact that this object has been lost. As stated earlier, everything has to be sent up to the ISS from Earth, meaning it’s often not simple to replace it. Because of this, the ISS does have a backup/ replacement inventory for many materials and objects to help reduce the impact of a broken or lost material or object. If that isn’t an option, astronauts are often able to cobble together a temporary solution (with ground control’s help) while a new one is placed on the manifest for the next shipment of supplies.
The second and larger concern is the object impacting the ISS and other objects in space such as satellites which could cause severe damage. Even a tiny nut or bolt can cause a lot of damage when traveling at 17,000 miles per hour, especially if it hit vital systems.
These lost objects become another piece of space junk (in addition to the naturally occurring Near-Earth Objects), which we are constantly trying to catalog and track to keep our satellites and other pieces of hardware in space safe.
Safety measures to protect this from happening:
Because of these concerns, there are a number of safety measures and procedures in place to reduce the chance of a dropped item (or even an untethered astronaut) on a spacewalk.
Astronauts are attached to the station with small cable tethers on retractable reels either 55 or 85 feet (17 or 26 meters) long which will self-retract to keep them from drifting too far away from the station. In addition to often using foot tethers, there are also small local tethers that only extend about 5 feet (1.5 meters) to help keep them close to the station to do their work, using both hands as opposed to using one to hold on.
There are tethers, velcro, and other attachments for all the tools, bags, and other gear they need for their particular spacewalk with the goal that every item that goes out of the airlock is attached to the astronaut or the space station. But keeping those tethers attached is often the hard part.
One of the concerns and reasons for the potential of dropping items is the challenge of microgravity while also wearing the spacesuit during a spacewalk. For a sense of the experience, try to complete a puzzle (even a small one with big pieces) while wearing hockey gloves. It’s much more challenging than you might expect and yet, even that is not a true comparison since, in the words of astronaut Andrew (Drew) Feustel, it’s closer to “wearing a set of mechanics gloves with welding gloves on top”.
NASA extensively trains astronauts for spacewalks in a similar environment of neutral buoyancy in full spacesuits. However, even this still leaves room for error since there is the possibility of accidents. Something can get nudged, or the tether could slip off for some reason despite being tested for it. And sometimes human error happens. It’s an unfortunate part of life.
So if an object is dropped, what do astronauts do?
Can they lunge for it if they notice it’s not attached? If they are on a short local tether, they will not have a lot of room to lunge, but some may try, especially if they spot it immediately. If they are on a long tether, that lunge could send them another 55 to 85 feet (17-26 meters) and hopefully, the tether would stop them (while tethers, like all space-bound equipment, are rigorously tested, there is always a chance that it could break), and they may or may not have had the chance to grab the object in that time. If the astronaut is in foot tethers, there likely isn’t a chance for them to maneuver out of them in time.
Whether they are in foot tethers, don’t notice the free-floating object in time, or lunge and fail to catch it, they likely just have to watch it float away, reporting the lost object to NASA Mission Control (what it was, how large it was, what direction it is traveling, expected speed based on observations, etc.). Mission Control then sends the data to the space debris tracking network which closely monitors the trajectory to determine if it causes any concern for impact with the space station or anything else.
Something bigger doesn’t always mean more concern than something smaller. A wire tie that was dropped during an EVA in March 2018 caused the first-ever orbital altitude readjustment of a satellite because of a free-floating object in space for fear of damage to the satellite. As demonstrated here, many satellites and even space stations, like the ISS, use a risk management system that creates a box around the hardware (i.e. 50ft cubed for the ISS) and tracks anything that might enter this box so that its course can be adjusted to avoid it. This is obviously not a situation that we want to use on a regular basis, but it is a system that is in place when a tracked object gets too close to a piece of hardware in space.
All in all, though, NASA has a very good track record for holding onto objects on spacewalks with these moments of dropped or missing objects being very rare, with only a few mishaps over the 23 years that the ISS has been in space.
Conclusion
There is concern about a dropped object on a spacewalk. However, these concerns are related to its ability to be replaced and its potential collisions with other space hardware such as satellites and even the ISS itself as opposed to colliding with Earth or even your head.
NASA has very strict procedures on spacewalks to protect the astronauts and the various pieces of equipment needed to complete their tasks to ensure that no one and nothing goes off into empty space. These procedures have ensured that for the vast majority of spacewalks, everything that leaves the airlock comes back in or is installed on the space station as intended.
On the few occasions that something has been dropped, astronauts may attempt to retrieve the item before it drifts too far away, but if they can’t, they report it to Mission Control so that it can be cataloged and tracked to reduce the chance of it impacting either the ISS or something else and causing damage. Eventually, the lost object will likely burn up in Earth’s atmosphere.
Sarah Hoffschwelle is a freelance writer who covers a combination of topics including astronomy, general science and STEM, self-development, art, and societal commentary. In the past, Sarah worked in educational nonprofits providing free-choice learning experiences for audiences ages 2-99. As a lifelong space nerd, she loves sharing the universe with others through her words. She currently writes on Medium at https://medium.com/@sarah-marie and authors self-help and children’s books.
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