“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. Keysight, put the very best tools into engineers
hands, and are holding a virtual event for electrical engineers and science enthusiasts
on the 14th of March. That’s 3 days from now so sign up quickly
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circuit board rules-of-thumb and testing them with keysights modern tools. For example, what happens to the electrical
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you can rewatch the stream and they will be holding new live events every 2 months, with
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newbie you should definitely be signing up for this completely free event.
