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STS-111
Canada Arm Q & A
Before
the KSC Direct! webcast of the STS-111 launch, space enthusiasts from
all over the world submitted questions for our Canada Arm expert, Benoît
Marcotte. The questions were answered during the show. In case you missed
the webcast, or would like to review each of the questions and answers,
we have provided the STS-111 Canada Arm Q&A in its entirety below.
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Tarun
from Gaithersburg, Maryland:
In what way is the Mobile Remote Servicer Base System an advantage
to the station? What are the current methods to service the
International Space Station? |
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I
guess the best way to answer this is to start with the second
part of the question, which is how we are servicing the International
Space Station right now. Canada Arm 2 was mounted on the International
Space Station on one anchor point last year, in April of last
year, and it has been operating within that radius of action
from that anchor point. The Mobile Base System will give it
now a new operating base from which it can do business, but
not only is it giving it the new operating base, it's got
four operating bases from that particular plate, and it's
also a moveable, transportable base that can move along the
truss of the International Space Station. So, it will allow
us to move the arm and do operations anywhere along the trust,
and not only that, but that the base will also be able to
carry payloads or truss segments when it's time to assemble
that trust segment in the long run. And the base will also
give us the ability as well to do EVA [Extra Vehicular Activity],
or support EVA better along the trust segment. It's going
to be a platform that astronauts will be able to rely upon
to carry out EVAs.
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Lee
from Hong Kong:
Can you explain the function of the Mobile Remote Servicer Base
System, and may I have the poster, please? |
| Well,
I can't answer the second portion about the poster, but the
functions of the Mobile Base System are really anchored around
the main components that we have on that base. I've already
mentioned that there are four grapple fixtures, or four points,
where Canada Arm 2 can anchor itself to on that base, and there's
one in each corner, if you've seen the presentation, the picture
of the Mobile Base System. So the arm also can double grapple,
both ends can be grappled to the Mobile Base System, and later
on when we have the special dexterous manipulator, another robot
that will do finer tasks on orbit, it can also be stored, will
also be stored, on those grapple fixtures. Afterwards, the other
components on the Mobile Base System are also some payload accommodation
points. These are anchor points, there are two different types:
one is a payload, that will be for large payloads, like a truss
segment, let's say. And the other one is more for payloads like,
would be, science experiments and so on, that would be anchored
on the base system while it is in transit from the shuttle payload
bay to where it's going to reside on the truss segment. So the
base will provide these major functions. And also, another important
feature is when payloads are sitting on the MBS, on the Mobile
Base System, they can also receive power through the Mobile
Base System in order to be thermally conditioned during the
time that they will be transited to their intended destination. |
Skyuen
from Burnaby:
How does the most recent modification to the Canad Arm enhance
the ability of the space shuttle? |
| Well,
I read here that when we talk about the Canada Arm is the Canada
Arm as we know it is the Space Shuttle Manipulator that has
been going up with the Space Shuttle since the early 80's or
so. And what I read in your question is what are, the new modification
is really Canada Arm 2, which is a totally new arm, built by
the same company, MD Robotics in Brampton in Canada, but that
arm is very much different, because it also brings new functionality.
Canada Arm 2 can work from either end, when Canada Arm on the
Space Shuttle is only anchored down at one location and it is
fixed at that point. Canada Arm 2 has 7 joints, so 7 degrees
of freedom as opposed to 6. Canada Arm 2 is about 4 times as
heavy as the shuttle arm, and that's because it now has a redundant
capability, because it's going to be on orbit for the next 15
years and will not come back to Earth. When Canada Arm 2 was
designed it was designed with 2 motors in each joint, 2 electronic
circuitry in each joint, and that added some weight to the arm
itself. Obviously it will also carry heavier masses: Canada
Arm 2 can also carry the full Space Shuttle approaching the
space station if that was required. And, as I said, Canada Arm
2 will stay in space for a long time. It's a little longer,
a little wider than Canada Arm, but it brings the functionality
that is absolutely required to continue to assemble the space
station. |
Robert
from St. Petersburg, FL:
Why does the Canada Arm 2 need repair, and what part of it is
not working? |
| Well,
first, let me say Canada Arm 2 is working, we've got 2 system,
2 redundant systems on board of each joint, or each portion
of the arm, so the arm has been functioning very well. We've
had an anomaly that manifested itself on the 5th of March of
this year and Canada, or the Canadian Space Agency, and our
contractor had to look at the, and redo a little bit the software
on that channel in order to operate the arm without one joint,
and so the arm was functioning on that channel with only 6 degrees
of freedom, but the other channel is fully functional and was
used to install the S-Zero truss segment during Mission 8A,
and the arm has been functioning very well. However this anomaly,
should, needs to be fixed, and we believe right now that we
might have a short circuit in one of the joints, and this is
what will be done during this mission. We're going to launch
in mission STS-111 another joint, a replacement joint, and the
crew of STS-111 will do a space walk, an EVA, to go, and remove
the LEE [Latching End Effector] from the end of the arm, and
then remove the joint, and the joint that has an anomaly is
the last joint just attached to the end of the arm, or where
the LEE is attached, and we'll remove the joint, replace it
with the new one, bring the broken one, or the one with an anomaly
back to the ground and will be, at that point, be able to determine
what the exact cause of the anomaly is, fix that, and make it
ready again to be launched as a spare joint if another joint
needed to be replaced in the future. The arm was totally designed
to be repaired in that fashion in space, because it will never
come back to Earth, so that gives us a tremendous capability,
this design is a tremendous design, in order to enable us to
maintain the arm on orbit. So, we will be experiencing a first
maintenance operation during mission STS-111, and we're really
looking forward to seeing the arm being totally healthy on the
two strings. |
Arnie
from Hickory:
How much weight can the Canada Arm handle on Earth? |
| That's
a good question, and it's an ironic question, because, it was
interesting to watch Canada Arm 2 during testing, being mounted
on supporting structures, and the arm components, the booms,
were not attached to each other, because the arm on the ground
can not sustain any major weights. But, on orbit it is able
to maneuver a space shuttle, and that's the interesting part
of why things are so different working in space than working
on the ground. |
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