Hey there! I'm NASA astronaut Ricky Arnold. Welcome aboard the International
Space Station. Today we're going to talk about the space station truss. The truss
segment is just about the little better 100 meters from side to side. A truss is
a segment or part of the whole integrated truss structure. The trusses
are used to support the 16 solar array panels which provide energy for us and
radiators which get rid of excess heat that builds up inside the space station.
The design of the truss involves triangles and beams which can be seen on
earth and structures like bridges. Why triangles?
Well this is because of their unique geometric properties, their methods of
transferring loads, and their spacial openness. Triangles are more rigid than
rectangular shapes because they have fewer joints. The larger number of joints
in a shape the more prone that shape is to being impacted by shear forces. What I'd
like to talk a little bit about today is some of the forces that can act upon the
truss. Well the first force I want to talk about is compression force and
compression force is just like it sounds two things being pushed together so if
we apply a compression force to the truss what do you think is going to
happen? Let me go ahead and do it and you can see right here where the
truss would bend. What do you think the opposite force of compression is now?
it's gonna right it's gonna be pulling apart we call that a tension force. And a
tension force is what's gonna help maybe even rigidize the truss segment but it
also could potentially pull it apart. I'm not gonna pull apart this tape measure
because we probably need it later for for some work we have to do. Now if you
look carefully this next force I want to talk about is basically kind of like a
twisting force and we call it torsion and even when I just let go of the the
tape measure you can see it will actually start to happen a little bit.
You can start to see because the center of mass is actually right here where
most of the tape measure is located and when I let it go the tape measure itself
starts to twist just a little bit. Finally the fourth force that connect
along a truss segment is it can occur at a single point where a two opposing
forces work on a single point along the truss just like they can upon the
Earth's surface think about some earthquakes you can
have a plate that is or along a fault line where a part of the one side of the
fault line is moving upward or being forced upward while the other side is
moving downward and that force in at one point and opposite directions is called
a shear force and we could also have that have that happen on the truss
segment. Something like this. One thing to think about where do these forces come
from? One force even though we're up here largely out of the Earth's atmosphere we
do still have drag with the Earth's atmosphere which can impart loads on the
impart a force on the truss segment. Another I already hinted at
earlier is crew working inside we're up here we're exercising we're moving
really heavy pieces equipment of equipment around so we have an amazing
engineering team on the ground and we have specific disciplines that are their
job is to monitor all the forces imparted upon the International Space
Station. They keep track of all those various forces I talked about where they
could be coming from the atmosphere visiting vehicles or even things that
the crew are doing inside the space station and to make sure that those
forces are significant enough to cause any damage to this wonderful laboratory
and living space we have up here in low-earth orbit. Thanks so much for
joining me today we'll see you next time! So long!
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