“Peggy I don’t have a shield.”
“What?”
“Yeah I don’t have a shield.”
“Where is it?
It’s right by the radiator.
It’s moving… maybe at half a foot a second.
It looks like straight down from the radiator angle.”
“We copy and we see it.”
While on a six-and-a-half hour spacewalk on the International Space Station in 2017, astronauts
Peggy Whitson and Shane Kimbrough experienced a bit of clumsiness that would pose no problems
on Earth, but can cause some major headaches in space.
They dropped a piece of a debris shield that was part of the docking port, a fabric covering
that weighed 8 kilograms and measured 162 cm by 59cm–about the size of a car door.
And that debris shield had an important role to play.
It was supposed to cover a docking port on the ship, protecting it from extreme temperature
changes and orbital debris.
Something the ISS could not do without.
The shield was a whipple shield, which uses the hypervelocity of space debris to its advantage.
Using thin layers of shield to obliterate the debris into tiny fragments that the inner
shield can withstand as the energy of the debris is spread out over a larger distance.
Back on Earth, the Mission Control team got to work.
Thanks to the fact that they have replicas of everything in space, every nut and bolt,
and every piece of fabric.
Mission control found a way for Whitson and Kimbrough to use wire ties and a different
piece of cloth as a substitute for the lost whipple shield, until a replacement could
be sent up on another rocket.
[1]
Having dealt with that problem, there was just one more thing to worry about: whether
that lost piece of the shield would come slamming back into the space station.
The shield was monitored closely for two orbits, before it was determined there was no risk
it would hit the ISS.
Kimbrough and Whitson could breathe a sigh of relief, and Whitson could properly celebrate
having completed the most spacewalks of any woman.
[2]
But just how common is it for astronauts to lose their grip on tools and other objects
while in the microgravity of space?
How costly are these brief bouts of “butter fingers” on the ISS?
And what happens if the newly-made space debris is on a collision course with the station
or another satellite?
These are all scenarios NASA and the astronauts themselves have to prepare for.
Like with anything else, sometimes accidents happen.
The lost shield wasn’t the first time astronauts have lost something to the swirl of space
while conducting an extravehicular activity, or spacewalk.
In 2006, astronaut Piers Seller dropped a spatula while doing work on the space station—and
apparently had a lot of spatulas waiting for him in his office when he came back to Earth
after the mission.
[3] That same year, another astronaut lost a camera.
And in 2008, another astronaut was dealing with a grease gun explosion when she lost
a tool bag.
“Oh great.
Um, we have a lost tool.”
Part of the reason items can become lost is because of the challenge of maneuvering small
objects while wearing massive gloves.
Astronaut Drew Feustel has gone to space three times for a total of 226 days, and conducted
nine spacewalks, accumulating the second-longest amount of EVA time among US astronauts.
He’s plenty familiar with the difficulty of doing work in a bulky 160 kilogram spacesuit.
I equate it to wearing a set of mechanics gloves with welding gloves on top, that’s
how it feels getting tactile feedback with your fingertips and hands.
There’s not really a good way to train that except expose yourself to that environment.
And the way NASA has astronauts practice in advance of going to space is by wearing their
suits in a massive pool, which has a precise recreation of the ISS built underwater for
the astronauts to practice on.
They learn how to maneuver in their suits, how to manipulate tools for repair work, how
to move objects from one area to another, and how to perform an emergency rescue on
team members–all while still on the planet.
It’s a pretty good analog,, but not everyone gets as much time to practice as they might
like.
Historically, during the shuttle area, we’d train at a 10 to one ratio, meaning we’d
practice a technique or task ten times underwater for every single time we saw in space, so
for every hour in space we’d have about ten hours in the pool underwater training
that task and that allows you to really build the knowledge for what you can expect the
feedback to be through your hands as you’re working with the objects in space.
We see much less of that now, we’re probably at a two to three to one ratio if that, so
it's more difficult to have that exposure and it becomes a challenge.
The astronauts also have a number of safeguards for themselves and all their hardware once
they’re outside the station doing an EVA.
They’re always attached to small cable tethers on retractable reels that are either 17 metres
or 26 metres long, which will self-retract, allowing the astronauts to move around without
fear of drifting too far away.
On top of that, they’ll have small local tethers that only extend about 1.5 metres,
which keep them close enough to the station that they can use both hands for a specific
activity, but they still have a little more room to maneuver.
Then there are all the tethers for the tools, bags, and whatever other gear they might be
carrying.
we always attempt to make sure that every single item that goes outside the airlock
with us has some attachment to something, and that’s achieved through those tethers.
We are not always successful in keeping those tethers attached, and it’s always a little
bit scary when you find yourself holding an object and you realize that there’s no tether
attached to it either because it was bumped off or came off accidentally or in some cases
it was never attached in the first place…
I’ve had a couple experiences with holding items that didn’t have tethers on them and
expected to have tethers on them, that’s where you reach down carefully and find a
tether somewhere anywhere to connect back to that thing.
But on one particular occasion, during his ninth spacewalk in March 2018, Feustel lost
hold of an object.
He’d been working to install cameras and wireless communication equipment next to a
docking port, as well as securing a loose component on a solar array blanket box when
he lost a wire tie—what he describes as something like a big garbage tie.
When he’d pulled the tether to which the wire tie was attached, it turned out that
the jaws of it were still open, and the tie quickly floated away.
There have been crew members in the past who have lunged after objects, you could maybe
do that if you have a short tether on, you’re not gonna lunge very far, if you have a long
tether on and you lunge you’re gonna travel for another 55 or 85 ft before that tether
hopefully stops you from your motion hand you may or may not have been successful at
reaching the object that is now floating away from you.
but in my case i was attached to a foot restraint, which m eans my feet were fixed, there was
really no way for me to move and I simp\ly watched this object float away from me.
at that time all you can really do is call Mission Control and say I’ve lost an object,
this is what it was, and this is how large it is, and this is the direction it’s traveling,
and this is how fast I think it’s going and that data gets reported to our tracking
officers at mission control and that gets reported pretty much around the entire space
debris network, which exists not only in the US but internationally to track items that
are floating in space that are not really controlled in any way.
Just as with the piece of dropped shield in 2017, NASA had to closely monitor the trajectory
of the little wire tie—and in this case, despite the object being much smaller, it
ended up being more of a problem.
I was told after the loss of my wire tie was for the first time in history a satellite
had to change its orbital altitude because of a free floating object in space, for fear
of damage to the satellite, and that object was my wire tie that I had lost, was floating
around and chad an impending collision with some type of satellite that was important
to somebody and they actually had to change the orbital altitude of that satellite in
order to create a greater distance or miss distance between those two objects.
Something as small as a wire tie could destroy an entire module on the space station or even
cause catastrophic damage to any piece of equipment in space.
Of course, this issue with debris goes far beyond a few mishaps with astronauts losing
hold of things while on an EVA.
NASA has a pretty good track record—on the vast majority of spacewalks, everything that’s
carried out is carried back inside.
The real problem is that debris has been accumulating in orbit around Earth ever since the Space
Race began with the launch of Sputnik in 1957.
By 1979, debris from satellites and failed rockets was already posing enough of a problem
that NASA created the Orbital Debris Program to monitor the accumulating number of small
objects that could cause damage to spacecraft.
[4]
This program uses a network of ground based and space based observation techniques.
Like the USAF Space Surveillance network, which can keep track of larger objects in
space.
While ground based radar like the Goldstone Solar System Radar can detect much smaller
objects.
Of course it would be impossible to keep track of all the debris.
Today there are about 23,000 objects larger than a softball orbiting Earth, half-a-million
1-cm-sized fragments, and about 100 million micro-fragments that are one millimeter or
slightly larger.
[5] So computer models have been developed to log and track space debris, which also
alert controllers when a collision becomes a threat and allows the avoidance maneuvers
to be performed.
The ISS has a risk management system when a potential collision is detected.
The ISS has an imaginary box drawn around it.
50 kilometres squared and point seven five kilometres deep.
This acts as an exclusion zone and any tracked debris that could pass through it will send
an alert to mission control.
From there careful risk analysis begins.
If there is a one in ten thousand to one in one hundred thousand chance of collision the
ISS receives a yellow warning.
Which means flight controllers must perform avoidance maneuvers if they do not interfere
with mission objectives.
This can be as simple as interfering with microgravity experiments.
If there is a greater than one in ten thousand risk [6], then a red warning is received and
the international space station must take action, regardless of mission objectives.
These exclusion zones exist for all satellites in NASA’s database.
For example on March 29th 2012 an automated email alert was sent to the Fermi Gamma-Ray
Space Telescope team.
Informing them of a predicted incursion between Fermi and Cosmos 1805, a retired Russian spy
satellite, where the two would pass within 200 metres of each other.
Forcing them to abandon their mission temporarily and point their thrusters, which were designed
to deorbit the satellite in their direction of travel, performing a 1 second burn to prevent
a potential collision.
[7]
Even the very smallest bits of debris, like a piece of flaking paint, travel at speeds
fast enough to do serious damage if they hit a rocket or the ISS, and tracking debris this
small is impossible, which is why we need debris shields.
Like the one dropped 2017, which ironically became debris itself.
However the debris shield was a relatively large and light object, helping it deorbit
quicker as atmospheric drag still exists at this altitude.
Forcing the ISS to perform regular boost burns to maintain its orbit.
Feustel says it’s also much harder to lose heavier objects while working outside the
space station.
You know for a large object that weighs 800 lbs, if you let go of it with no tether on
it, it’s not gonna go anywhere.
Even if you bumped it with your hand it’s not gonna go anywhere because you can’t
put enough force into it to actually move it.
But something like a wire tie that’s just a small metal wire, that’s super easy, if
you just flick it with your fingertips or bump it, that thing is gonna go cruising away
much faster than you can reach it.
But it’s not only the risk of a collision that causes problems when an astronaut loses
something to space.
There’s also the issue of whether or not that tool had replacements on the space station.
Consider the lost shield again.
Something that weighs 8 kilograms doesn’t sound very large, but when you factor in the
cost of rocket launches, every kilo counts.
At least in the case of the wire tie Feustel lost, there were others available on the space
station.
And ultimately, the rogue wire tie didn’t cause any damage—though Feustel says it
can be a little blow to an astronaut’s perfect record.
You lose style points for losing things in space.
It’s probably possible to find this out, to do a web search and find out when I lost
my wire tie, I remember saying something like, well, I’m going to have to live with this
for the rest of my life knowing I dropped something in space, because up until that
point I had a pretty good record.
I had gone without dropping anything at all, this last act of misfortune was my contribution
to items floating in space that shouldn’t be.
So it’s more of a style thing.
Nobody looks, it doesn’t reflect negatively, i don’t think, on your spacewalking career,
but it certainly is something that we all strive not to do, and you don’t want to
be the person that’s constantly losing things.
In fact if you were somebody who constantly lost things both in training and in space
you probably wouldn’t be doing spacewalks out on orbit.
Dropping a tool in space is not something any of us have to worry about on a daily basis,
but having the right tool for the job and knowing how to use it can make or break a
project.
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