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Ep. 37, Page 16
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Comic 2875 - Ep. 37, Page 16

5th Jun 2019, 8:55 PM in Episode 37 :: Save My Place | Load My Place
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Author Notes:

smbhax 5th Jun 2019, 8:55 PM edit delete
Two days ago I wrote about a couple spacecraft grapple mechanisms in development; so, since I already had to look some of this stuff up, I thought I might as well write a bit about other spacecraft grapple systems—particularly robot arms.

The arm I drew in page 13 of this episode was, of course, based on vague recollections of the large arm that could be mounted in the old Space Shuttle cargo bays: Canadarm (kind of an awkward name, but Canada *really* wanted you to know they made it!).

I got the actual grapple business end of the arm totally wrong, of course; the 15.2 meter long Canadarm didn't have big pincers, but rather a sort of tube assembly housing an enclosed grasping mechanism, made to latch on to specifically designed grapple fixtures that would have had to be placed for that purpose on whatever Canadarm was going to be called upon to manipulate. The standardized North American grapple fixture has a kind of cool sci-fi-ish-looking tripod design of three "ramps" that guide the grasping mechanism to the central pin.

The 17.6m successor to Canadarm, the even less creatively named Canadarm2, makes up a key part of the Mobile Servicing System on the International Space Station. In addition to that large arm, there's a smaller, two-armed Canadian robot named "Dextre," which can be mounted on Canadarm2, or placed by Canadarm2 on mounting points on the station exterior.

Canadarm2 actually has grasping mechanisms at both ends, which also incorporate connections for power, data, and video feeds; it can gradually move itself, in an "inchworm motion," across the station exterior by connecting alternating ends to powered connection ports (the same ports Dextre can be mounted on) while swinging its other end over to advance to the next. : o

If it doesn't want to go to all that work, it can hitch a ride on the station's Mobile Base System, a platform mounted on a 108m track running the length of the station's main truss. The MBS was also made in Canada.

The Japanese module on the ISS has its own 10m arm, JEMRMS, which can use the same grapple fixtures as Canadarm2.

The Russian segment of the ISS is due to get its own arm, the 5m European Robotic Arm. Originally planned for 2015, it has been pushed back at least a few times, from the looks of outdated sections of the Wikipedia page, and is currently scheduled for launch in summer 2020. The ERA will be able to move "hand-over-hand" like Canadarm2 does, but it will connect to grapple fixtures of a different design, and appears to be intended for use more or less exclusively around the Russian segment of the station.